ASME Conference Presenter Attendance Policy and Archival Proceedings

2016;():V05AT00A001. doi:10.1115/DETC2016-NS5A.

This online compilation of papers from the ASME 2016 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (IDETC/CIE2016) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

40th Mechanisms and Robotics Conference: Compliant Mechanisms and Micro/Nano Mechanisms (A. Midha Symposium)

2016;():V05AT07A001. doi:10.1115/DETC2016-59012.

This paper presents an integrated design approach, a new topology optimization technique, to simultaneously synthesizing the optimal structural topologies of compliant mechanisms (CMs) and actuator placement — bending actuators and rotary actuators — for motion generation. The approach has the following salient features: (1) the use of bending actuators and rotary actuators as the actuation of CMs, (2) the simultaneous optimization of the CM and the location and orientation of the actuator that is embedded in the CM, (3) the guiding of a flexible link from an initial configuration to a series of desired configurations (including precision positions, orientations, and shapes), and (4) a new connectivity checking scheme to check whether the regions of interest in a design candidate are well connected. A program was employed for the geometrically nonlinear finite element analysis of large-displacement CMs driven by either bending actuators or rotary actuators. Two design examples were presented to demonstrate the proposed approach. The design results were 3D printed, and they all achieved desired shape changes when actuated.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A002. doi:10.1115/DETC2016-59063.

A fixed-guided beam is one of most commonly used flexible segments in compliant mechanisms such as bistable mechanisms, compliant parallelogram mechanisms, compound compliant parallelogram mechanisms and thermomechanical in-plane microactuators. In this paper, we split a fixed-guided beam into two elements, formulate each element using the Beam Constraint Model (BCM) equations, and then assemble the two elements’ equations to obtain the final solution for the load-deflection relations. Interestingly, the resulting load-deflection solution (referred to as Bi-BCM) is closed-form, in which the tip loads are expressed as functions of the tip deflections. The maximum allowable axial force of Bi-BCM is the quadruple of that of the BCM. Bi-BCM also extends the capability of the BCM for predicting the second buckling mode of fixed-guided beams. Besides, the boundary line between the first and the second buckling modes of fixed-guided beams can be easily obtained using a closed-form equation. Bi-BCM can be immediately used for quick design calculations of compliant mechanisms utilizing fixed-guided beams as their flexible segments (generally no iteration is required). Different examples are analyzed to illustrate the usage of Bi-BCM, and the results show the effectiveness of the closed-form solution.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A003. doi:10.1115/DETC2016-59078.

The construction of compliant mechanisms is commonly performed in a single plane, due to the limitations on available manufacturing processes. This paper looks at the design and manufacturing of compliant mechanisms with members that cross over one another and thus need to be manufactured by alternative methods. The approach described here relies on the use of sheet-metal modeling software to create a 3D representation of a compliant linkage that can then be unfolded and 3D printed as a flat part. The modeling process begins with the development of a pseudo-rigid-body linkage to obtain a mechanism geometry to produce a specified motion. The PRBL is then converted to a lumped compliant mechanism by first laying out the locations of the flexural pivots in a modeling sketch, and then using the sheet metal feature of a solid-modeling program to create a model of the mechanism geometry. The sheet metal modeling process requires the user to separate the geometry into appropriate layers to provide clearance between links that cross over one another. The separation into proper layers includes the specification of a proper layer for each link, and the definition of the flexural pivots as belonging to either a single layer or to multiple layers. The sheet metal modeling must also pay attention to the need for the model to be able to unfold into a flat pattern. Once the sheet metal model is fully defined, the model is unfolded at the bends to obtain a flat pattern. The rigid portions of the mechanism are reinforced in the CAD model by thickening the regions of the model that lie between the sheet metal bends. The model is printed in its flat state, and then manually folded to its designed shape. This paper focuses on the design of relatively small models with the printing process being accomplished with the use of a desktop, dual material FFF 3D printer with soft PLA for the flexible material and ABS for the rigid reinforcement. The specific mechanism modeled in this paper is based on a Watt I six-bar linkage designed to imitate the motion of a finger. The size, space, and motion requirements of this design make the model an ideal candidate for conversion to a compliant linkage using the methods described in the paper. While the production process is simplified by the ability to use a 3D printer to produce the model, the design technique may also be applied to larger models where the parts are cut from flat stock using a variety of other manufacturing options.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A004. doi:10.1115/DETC2016-59110.

This paper mainly presents a novel compliant universal joint with linear stiffness (CUJ-LS). This new type of architecture can maintain the linear stiffness while realizing two rotational DOFs. And the planar topology ensures that the rotation axis remains through the center of the moving platform, thus deducing the moment of inertia. According to the Freedom and Constrain Topology (FACT) theory, this paper firstly proposes a topological structure of the compliant universal joint. Then the stiffness model is established by the Beam Constraint Model (BCM) and the condition of achieving linear stiffness is derived: λ = 0.1273/0.8727. By introducing the intermediate platforms, the linear stiffness in two directions of rotation is realized. Finally, FEA method is implemented to verify and analyze the rotation performances of this compliant universal joint. Verified characteristics provide conditions for the applications of compliant universal joint in laser communication, antenna pointing, infrared tracking and aiming, laser processing, precision measurement and other fields which require high-speed, high-acceleration and high precision characteristics.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A005. doi:10.1115/DETC2016-59124.

Taking the tire of the lunar rover as the research background, this paper provides two design concepts of non-pneumatic tires (NPTs) with a compliant cellular solid spoke component. In this study, a series of degrees of freedom (DOFs) and stiffness analysis of NPTs with cellular structures are investigated with the same vertical loading conditions using a commercial finite element analysis tool, ANSYS. The research found that the tread relative to the hub only has in-plane translational degree of freedom in the radial direction, without other DOFs. According to this finding, using the improved design method based on the existing cellular structures and the synthetic design method based on the principle of compliant mechanism, two cases of cellular structures are designed: (i) cross arcs cell and (ii) rectangular cell. Analysis of the influence of geometric parameters of the cell on the performance of NPTs is critical to further improve the performance of the NPTs. Finally, by optimizing the geometrical parameters of the cellular structure, the performance of the NPTs with the cross arcs cell and rectangular cell can be enhanced.

Topics: Tires
Commentary by Dr. Valentin Fuster
2016;():V05AT07A006. doi:10.1115/DETC2016-59206.

This paper introduces a general method for determining the mobility analysis of flexure systems of any complexity, including those that can’t be broken into parallel and serial flexure subsystems. Such systems are called interconnected hybrid flexure systems because they possess limbs with intermediate bodies that are connected by flexure systems or elements. The method in this paper utilizes screw algebra and graph theory to enable designers to determine the freedom spaces (i.e., the geometric shapes that represent all the ways a body is permitted to move) for all the bodies joined together by compliant flexure elements within interconnected hybrid flexure systems. Although many flexure-based precision motion stages, compliant mechanisms, and microarchitectured materials possess topologies that are highly interconnected, the theory for performing a mobility analysis of such interconnected flexure systems using traditional screw theory does not currently exist. The theory introduced here lays the foundation for an automated tool that can rapidly generate the freedom spaces of every rigid body within a general flexure system without having to perform traditional computationally expensive finite element analysis. Case studies are provided in the paper to demonstrate the utility of the proposed theory.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A007. doi:10.1115/DETC2016-59223.

The traditional measurement platform for unbalance moment exploits the knife-edge as the support module but its performance rapidly deteriorates as the edge is worn down. In this paper, the flexure mechanism is utilized to overcome this drawback. The generalized cross-spring pivot is designed to achieve the approximate constant rotational stiffness and reduced center shift, which will benefit the control system and calibration procedure. A 2-DOF flexure mechanism is thus proposed by taking the practical application into account, such as manufacturability, performances of sensor and actuator. The finite element analysis (FEA) is carried out to verify the validation of design. Finally, the experiment is implemented and the results show a high accuracy: the error is less than 2.4g·mm even though the payload is up to 7kg and the unbalance moment is 100g·mm.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A008. doi:10.1115/DETC2016-59247.

Usage of compliant micro mechanical oscillators has increased in recent years, due to their reliable performance despite the growing demand for miniaturization. However, ambient vibrations affect the momentum of the oscillator, causing inaccuracy, malfunction or even failure of these devices. herefore, this paper presents a compliant force balanced mechanism comprising at least a prismatic joint, thereby creating the opportunity for usage of prismatic oscillators in translational accelerating environments. The proposed mechanism entails the symmetric displacement of two coplanar prismatic joints along non-collinear axes via a shape optimized linkage system. Rigid-body replacement with shape optimized X-bob, Q-LITF and LITF joints yielded a harmonic (R>0.999), low frequency (f = 27 Hz) single piece force balanced micro mechanical oscillator (∅35 mm). Experimental evaluation of large scale prototypes showed a limited ratio of the center of mass compared to the stroke of the device (≈0.01) and proper decoupling of the mechanism from the base, as the oscillating frequency of the balanced devices during ambient disturbances was unaffected, whereas unbalanced devices had frequency deviations up to 1.6%. Moreover, the balanced device reduced the resultant inertial forces transmitted to the base by 95%.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A009. doi:10.1115/DETC2016-59287.

Large stroke flexure mechanisms inherently lose stiffness in supporting directions when deflected due to load components in compliant bending and torsion directions. To maximize performance over the entire range of motion, a topology optimization suited for large stroke mechanisms is required. In this paper a new multibody-based topology synthesis method is presented for optimizing large stroke flexure hinges. This topology synthesis consists of a layout variation strategy based on a building block approach combined with a shape optimization to obtain the optimal design tuned for a specific application. A derivative free shape optimization method is used to optimize high complexity flexure mechanisms in a broad solution space. To obtain the optimal layout, three predefined “building blocks” are proposed which are consecutively combined to find the best layout with respect to a specific design criteria. More specifically, this new method is used to optimize a flexure hinge aimed at maximizing the first disturbing eigenfrequency. The optimized topology shows an increase in frequency of a factor ten with respect to the customary three flexure cross hinge, which represents a huge improvement in performance. The numerically predicted natural frequencies and mode shapes have been verified experimentally.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A010. doi:10.1115/DETC2016-59342.

The parameters of an innovative padding concept were investigated using Finite Element Analyses (FEA) and physical testing. The concept relies on a compliant corrugation embedded in an elastic foam to provide stiffness for force distribution and elastic deformation for energy absorption. The shape of the corrugation cross section was explored as well as the wavelength and amplitude by employing a full factorial design of experiments. FEA results were used to choose designs for prototyping and physical testing. The results of the physical tests were consistent with the FEA predictions although the FEA tended to underestimate the peak pressure compared to the physical tests. A performance metric is proposed to compare different padding configurations. The concept shows promise for sports padding applications. It may allow for designs which are smaller, more lightweight, and move better with an athlete than current technologies yet still provide the necessary protective functions.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A011. doi:10.1115/DETC2016-59348.

Compliant constant-force mechanisms (CFM) are a type of compliant mechanism which produce a reaction force at the output port that does not change for a large range of input motion. This paper describes a new compliant CFM, introduces its design and configuration-improvement process. A finite element analysis (FEA) model of the compliant CFM was created to evaluate its constant force behavior. The FEA result shows that when the displacement is Δ = 4 mm, the compliant CFM maintains a nearly constant force in the operational displacement range of 1.31 mm to 4 mm with an error of 5.05%. The operational range accounts for 67% of the total motion. This compliant CFM can be used to regulate the contact force of a robot end-effector or as an electrical connector.

Topics: Design
Commentary by Dr. Valentin Fuster
2016;():V05AT07A012. doi:10.1115/DETC2016-59498.

The motion capability of a flexure hinge made of shape memory alloy (SMA) can be greatly improved because of the material’s superelasticity. In this paper, the nonlinear deformation characteristics of a superelastic flexure hinge are analyzed. The flexure hinge is considered as a non-prismatic cantilever beam subjected to a combined load at the free end. Superelastic behavior of the SMA is represented by Auricchio’s constitutive model. Govern equations of the large deformation superelastic flexure hinge are derived by using the Bernoulli-Euler beam theory and solved numerically. Based on the static deformation model, the rotation capacity, the stiffness characteristic and the rotation error of the flexure hinge are discussed respectively. Numerical examples compared with Finite Element analysis (FEA) show the accuracy of the proposed methodology.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A013. doi:10.1115/DETC2016-59582.

One of the challenges often encountered in compliant mechanism design is managing material selection given the need to meet multiple constraints. Many methods have been offered previously to systematically facilitate that decision process. However, these methods struggle to incorporate a systematic method for material selection in multi-functional compliant mechanisms. This work seeks to address this gap by generically implementing a new Ashby-based material selection and design method for compliant mechanisms with multi constraint design criteria. To help demonstrate the method, the design of an electrically conductive lamina emergent torsion (LET) joint used for a back-packable solar array is explored. The methodology described here can be used to create other compliant mechanism performance metrics to address the design of specific compliant mechanisms.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A014. doi:10.1115/DETC2016-59590.

This paper presents a new Bistable Collapsible Compliant Mechanism (BCCM) that is utilized in a Lamina-Emergent Frustum. The mechanism is based on transforming a polygon spiral into spatial frustum shape using a mechanism composed of compliant links and joints that exhibits bistable behavior. A number of mechanism types (graphs) were considered to implement the shape-morphing spiral, including 4-bar, 6-bar, and 8-bar chains. Our design requirements permitted the selection of a particular 8-bar chain as the basis for the BCCM. Bistable behavior was added to the mechanism by introducing a compliant link that functions as a compression spring as the mechanism morphs. Parametric CAD was used to perform the dimensional synthesis. The design was successfully prototyped.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A015. doi:10.1115/DETC2016-59616.

Idiopathic scoliosis is a deformity of the spine that affects 2–3% of adolescents. The treatment of scoliosis often requires the use of a rigid brace to align the spine and prevent progression of the deformation. The most common brace, referred to as the Boston brace, has a high success rate in preventing progression of the scoliotic curve. The common root failure is lack of patient compliance in wearing the brace for the prescribed time. This lack in compliance is due to patient discomfort, both physically and emotional, and the patients’ limited ability to perform activities of daily living (ADL) when wearing the brace. The likelihood of needing surgery increases dramatically when bracing is unsuccessful.

We seek to improve patients’ comfort by designing a brace that improves range of motion, while remaining stiff in the corrective direction. Primary ranges of motion were acquired using a motion capture system. A kinematic analysis was performed using homogeneous transformations and screw theory to determine primary screw axes of the motions. The required lateral stiffness for the brace was found in literature.

Compliant mechanisms are used because they can apply the corrective force, but also allow the patients some range of motion. The mechanism implementation was characterized using finite element analysis and compared to a physical model test.

Initial findings confirm that compliant mechanisms are suitable for the application of a scoliosis brace. We have found that the proposed brace can apply the necessary forces at reasonable displacements. The proposed brace will not allow the patient a full range of motion, but we believe that it will achieve an improved range of motion that will increase a patient’s ability to perform activities of daily living.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A016. doi:10.1115/DETC2016-59759.

Majority of existing methods of measuring micro-force are limited by the sensing elements, which are fixed on the manipulator and not well decoupled from other axes. In this paper, a unique 1-D force sensor with different sensing elements is first proposed as a micro-manipulator for 1-D force sensing applications in biological cell injection. The goal is to fabricate a compliant sensor using piezoresistive and PVDF (polyvinylidene fluoride) elements for cell injection with sufficient accuracy. The designed sensor is manufactured and calibrated with a commercial GSO gram sensor. Experimental results show a good linearity between the applied force and output voltage signals, which demonstrates the feasibility of the concept design of a force sensor acting as the cell holder. The performances of the force sensor employing piezoresistive and PVDF elements are compared by conducting experimental studies.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A017. doi:10.1115/DETC2016-59828.

Synthesis of distributed compliant mechanisms is often a two-stage process involving (a) conceptual topology synthesis, and a subsequent (b) refinement stage to meet stress and manufacturing specifications. The usefulness of a solution is ascertained only after the sequential completion of these two steps, which are in general computationally intensive. This paper presents a strategy to rapidly estimate final operating stresses even before the actual refinement process. This strategy is based on the uniform stress distribution metric, and a functional characterization of the different members that constitute the compliant mechanism topology. It enables selecting the best conceptual solution for further optimization, thus maximally avoiding refinement of topologies that inherently may not meet the stress constraints. Furthermore this strategy enables modifying topologies at the early design stage to meet final stress specifications, thus greatly accelerating the overall synthesis process.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A018. doi:10.1115/DETC2016-59830.

Mobility analysis is an important step in the conceptual design of flexure systems. It involves identifying directions with unrestricted motion (freedoms) and directions with restricted motion (constraints). This paper proposes a deterministic framework for mobility analysis of wire flexure systems by characterizing a kinetostatic vector field known as “load flow” through its geometry. The relationship between load flow and the flexure axis is used to determine if a flexure behaves as a constraint or a freedom. This knowledge is utilized to formulate a matrix-based reduction technique to determine flexure mobility in an automated fashion. Several examples with varying complexity are illustrated to validate the efficacy of this technique. This technique is particularly useful in analyzing complex hybrid interconnected flexure topologies, which may be non-intuitive or involved with traditional methods. The proposed framework combines both visual insight and analytical rigor, and will complement existing analysis and synthesis techniques.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A019. doi:10.1115/DETC2016-59834.

Soft compliant robots and mechanisms have generated great interest due to their adaptability, and inherently safe operation. However, a systematic synthesis methodology for these devices has always remained elusive owing to complexities in geometry, and nonlinearities in deformation and material properties. This paper builds the groundwork towards a constraint based design (CBD) method for a unique class of soft robotic building blocks known as fluid-filled fiber-reinforced elastomer enclosures (FREEs). First, the constraint behavior of FREEs with varying fiber angles is mapped using an automated mobility analysis framework that is based on matrix-based kinetostatic methods. Specifically, such an analysis seeks to establish the constraint behavior of FREEs as a function of not just the global geometry, but also its local anisotropic material constituents. Then, the paper demonstrates the principle of reconfigurable constraint by combining several FREEs in series in accordance to the rules of constraint-based design. Eventual extension to actuating FREEs will enable a comprehensive synthesis methodology for soft robots.

Topics: Design
Commentary by Dr. Valentin Fuster
2016;():V05AT07A020. doi:10.1115/DETC2016-59884.

Understanding and controlling the nonlinear bistable mechanics is crucial for the development of advanced bistable devices ranging from quantitative mass sensing to functional smart materials and structures. Currently, bistable features including the switching forces, travelling stroke, bistable index parameter ( ratio of the two switching forces) are affected complicatedly by the structure profile, size and loading cases. Due to the complex coupling effects among these bistable features, it is really difficult to design or modify one specific bistable character without affecting other bistable characters. While subjected to different loads (type and position), the phenomenon of mode switching may occur during the snap-through procedure, thus resulting in bistability uncertainty. Aiming to design specific and stable bistable characters for different application requirements, a novel optimization based bistability design method is proposed through simultaneously modifying the geometries of multi-local segments and their arrangements. With the goal of re-adjusting the bistable index parameter as well as minimizing the snapping force, the uniform cosine-shaped bistable beam is reconstructed by adding several reinforced local segments arranged symmetrically and asymmetrically along the length direction. In two numerical examples, the bistable index parameters and switching forces are properly re-designed without changing the profile and overall size of the original structure. The numerical simulation results show that the bistable index parameter can be redesigned to 1.021 and 1.2 from the original value of 0.598, thus validating the effectiveness of the optimization-based bistability design method, which exhibits great application potentials in bistability based products.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A021. doi:10.1115/DETC2016-59897.

In the present paper, we take the complaint double parallel guiding mechanism as a particular case study to investigate a modified pseudo-rigid-body (MPRB) modeling approach for beam flexure based mechanisms by considering the nonlinear effects of the center-shift and the load-stiffening. In particular, through incorporating the elastic stretch of the beam flexure into the linear Bernoulli-Euler equation, a more accurate model of the beam flexure is derived. Accordingly an MPRB model for a beam flexure is established, which consists of two rigid links joined at a revolute joint and a torsional spring along the beam. Different from traditional PRB model, the location of the torsion spring is not only determined by the characteristic radius factor, but also a purely elastic stretch under the action of the axial force. Meanwhile, both the characteristic radius factor and the equivalent stiffness of the beam flexure are no longer constant values, but affected by the applied general tip load, especially the axial force. Based on the analysis results of a beam flexure, we obtain a more accurate model of the double parallel guiding mechanisms, which is further verified by the finite element analysis (FEA) results. The proposed MPRB model provides a more parametric method to predict the performance characteristics such as deformation capability, stiffness variation, as well as error motions of the beam flexure based complaint mechanisms, and offers a new look into the design and optimization of beam-based compliant mechanisms.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A022. doi:10.1115/DETC2016-59923.

Pancreatic cancer is one of the most deadly forms of cancer in the United States. Due to its late diagnosis, only 20% of patients diagnosed with the disease are eligible for surgical resection which is considered the preferred method of treatment. Radiofrequency ablation is a common cancer treatment modality for patients ineligible for open surgery. There is a lack of ablation probes which may be used to generate spherical heating zones which closely match the geometry of typical tumors. In particular, there are no endoscopic ablation probes commercially available in the United States. In this paper the design of a compliant endoscopic radiofrequency ablation probe is presented. This probe features an array of compliant tines which deploy through the cancerous tissue to effectively broaden the ablation zone. A thermal ablation model is used to inform the design of the geometry of the probe. In addition, finite element analysis is used to determine the feasibility of the compliant structures. These design tools are used as aids to inform the design and direct modifications toward a feasible probe which generates a spherical ablation zone.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A023. doi:10.1115/DETC2016-59946.

The initial design of compliant mechanisms for a specific application can be a challenging task. This paper introduces a topology optimization approach for planar mechanisms based on graph theory. It utilizes pseudo-rigid-body models, which allow the kinetostatic equations to be represented as nonlinear algebraic equations. This reduces the complexity of the system compared to beam theory or finite element methods, and has the ability to incorporate large deformations. Integer variables are used for developing the adjacency matrix, which is optimized by a genetic algorithm. Dynamic penalty functions describe the general and case-specific constraints. A symmetric 3R model is used to represent the beams in the mechanism. The design space is divided into rectangular segments while kinematic and static equations are derived using kinematic loops. The effectiveness of the approach is demonstrated with the example of an inverter mechanism. The results are compared against finite element methods to prove the validity of the new model as well as the accuracy of the approach outlined here. Future implementations of this method will include stress and deformation analysis and also introduce multi-material designs using different pseudo-rigid-body models.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A024. doi:10.1115/DETC2016-59959.

This paper presents a new concept: a Shape-Morphing Space Frame (SMSF) using quadrilateral bistable unit-cell elements. The unit-cells are composed of either eight-bar or seven-bar mechanisms in which design constraints, system of elimination and graph theory are used to design, as a proof of concept, a disk like structure with the ability to morph into a sphere. Or specifically, the circumference of a disk structure is approximated by a ten-sided polygon that would then morph into a hollow sphere structure that is approximated by 60-sided polyhedron. The disk-to-sphere structure is tessellated into ten sides for the latitudes circles and 12 sides for the longitude circles; the disk’s thickness and radius are chosen at the design stage. The strategy in morphing the initial shape of the structure (disk) into its final shape (sphere) is that the radial lines on the surface of the disk bend but do not stretch, whereas the circumferential lines compress. Moreover, the radial lines on the disk become longitude lines on the sphere and the circumferential lines become latitude lines on the sphere. The disk’s thickness splits in half, the upper half becomes the thickness of the upper hemisphere and the lower half becomes the thickness of the lower hemisphere. The concept was successfully prototyped and actuation forces were measured.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A025. doi:10.1115/DETC2016-59960.

This paper presents a new concept and method to design mechanisms’ stability using over-constraint. The designs involve the use of parametric Computer-Aided Design (CAD) software to synthesize a mechanism’s geometry in order to achieve a design’s specific bistability requirements. This method ensures a stable position without the need of a hard-stop. There are two main initial design considerations that need to be met in this analysis. First, both (first and second) state of the mechanism should be chosen and should represent the mechanism’s desired stable positions. The first state is the position that the mechanism was manufactured or assembled at, whereas the second state is the position at which the mechanism is toggled to. The second consideration is the assumption that the magnitude of the joints’ torsional spring stiffness is small i.e. living hinges. The main idea is to attach a Potential Energy Element (PEE), such as a spring or a compliant link, to the four-bar mechanism such that it is unstretched in both stable positions and has to deform (stretch or compress) during the motion between stable states. This approach seems to allow the designer considerable freedom in amount of motion between stable states and in the amount of force required to toggle between stable states.

Topics: Stability , Design
Commentary by Dr. Valentin Fuster
2016;():V05AT07A026. doi:10.1115/DETC2016-59966.

Flexure mechanisms are the central part of numerous precision instruments and devices that are used in a wide range of science and engineering applications and currently, design of flexure mechanisms often heavily relies on designers’ previous hands-on experience. Therefore, a design tool that will speed up the design process is needed and this paper will introduce a systematic approach for building the necessary equations that are based on screw theory and linear elastic theory to analyze flexure mechanisms. A digital library of commonly used flexure elements must be available for a design tool and therefore, we first present the compliance matrices of commonly used flexure components. Motion twists and force wrenches of the screw theory can be related with these compliance matrices. Then, we introduce an algorithm that constructs the required linear system equations from individual compliance equations. This algorithm is applicable to flexure mechanisms with serial, parallel or hybrid chains. Finally, the algorithm is tested with a flexure mechanisms and it is shown that this approach can be the core of a future design tool.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A027. doi:10.1115/DETC2016-59979.

The stiffness characteristics of flexure strips in the constrained directions are an important attribute of their behavior when serving as a constituent of flexure mechanisms. The decrease in support stiffness that accompanies movement in the intended degrees of freedom limits the performance of mechanisms comprised of such strips. This paper presents a closed-form nonlinear model that describes the support stiffness in 3-D under arbitrary end-load for the elementary flexure strip. The formulation takes into account geometrical nonlinearities by means of finite strain relations and deformed-configuration equilibrium equations. By distinguishing the low-stiffness large-deflection motion (the degrees of freedom) from the high-stiffness small-deflection motion (the constrained motion) with the appropriate simplification of limited twist, a closed-form stiffness model is obtained for dimension and load ranges of practical interest.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A028. doi:10.1115/DETC2016-59989.

Due to their advantages compliant mechanisms are very popular. However, they also have some disadvantages as well. Considering that for micromanipulators, which have macroscopic dimensions and a workspace typically in millimeter range, the disadvantages of compliant mechanisms are not as significant as the feasible benefits by reason of their advantages. For instance the range of notch hinges, which are typically used for micromanipulators, can be increased by the use of precision notch hinges with a narrow web thickness. Precision notch hinges are cut efficiently by wire electrical discharge machining. Therefore, flexure hinges are widely used in precision engineering applications.

Even though electrical discharge machining is a manufacturing process which is based on the thermo-physical material removal principle with less resulting mechanical stress, it still induces thermal stress on the component. It can be assumed that these influences have an impact on the component’s performance, in particular when the component has filigree structures like precision notch hinges. However, experimental studies on the fatigue of compliant joints are currently missing in research activities.

To analyze the manufacturing related influences on the performance of precision notch hinges a series of fatigue tests have to be performed. Thus, a suitable test bench for fatigue testing of precision notch hinges is designed and the used transmission mechanism is explained. Furthermore, the adjustment mechanism for the swivel angle as well as the adjustment mechanism for different loadings of the test specimens are discussed. Additionally, to avoid incorrect loading several design features are explained. To obtain reliable results, the filigree test specimens have to be positioned on the test bench reproducibly in order to ensure recurring test conditions. Thus, the positioning process is explained. In order to increase the number of tested notch hinges, several test specimens are tested simultaneously under the same conditions. Hence, a clear detection of the maximum number of load cycles of each test specimen is ensured by a detection mechanism. This contribution ends with the presentation of preliminary results of the life expectancy analyses of precision notch hinges and a brief discussion of the results.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A029. doi:10.1115/DETC2016-60496.

A mechanism is designed to transform forces and/or displacements from an input to one or multiple outputs. This transformation is essentially ruled by the kinematics, i.e. the defined ratio between input and output displacements. Although the kinematics forms the basis for the design of conventional mechanisms, approaches for the topology and shape optimization of compliant mechanisms do not normally explicitly include the kinematics in their optimization formulation. The kinematics is more or less an outcome of the optimization process. A defined kinematics can only be realized by iteratively adjusting process-specific optimization parameters within the optimization formulation. Moreover, existing approaches normally minimize the strain energy that is stored in the compliant mechanisms according to a defined input and output displacement — although in some applications a certain amount of strain energy is required. This paper presents a new optimization formulation that solves the aforementioned problems. It is based on the principles of designing compliant mechanisms with selective compliance formerly presented by the author. The formulation is derived by means of an intensive workup of the design problem of compliant mechanisms. The method is validated for different design examples ranging from standard single-input/single-output mechanisms (force inverters) to multi-output mechanisms (shape-adaptive structures).

Commentary by Dr. Valentin Fuster

40th Mechanisms and Robotics Conference: Medical and Rehabilitation Robotics

2016;():V05AT07A030. doi:10.1115/DETC2016-59303.

The last decade has seen rapid growth in exploring the potential of continuum robots for a variety of surgical applications. The design of these robots requires unique electro-mechanical architectures of actuation units that satisfy operational requirements of precision, workspace, and payload capabilities. This paper presents the task-based design process of a compact nine degrees of freedom actuation unit for transurethral resection of bladder tumor (TURBT). This actuation unit has a unique modular architecture allowing partial decoupling of actuation, force and position sensing in a compact modular format. The derivation of task specifications based on kinematic simulations takes into account workspace, accuracy and force application capabilities for TURBT. Design considerations for supporting modularity, serviceability, sterilization, and compactness are presented. The detailed exposition of the design process serves as a case study that will be helpful for other groups interested in the development and integration of surgical continuum robots.

Topics: Robots , Design , Cancer
Commentary by Dr. Valentin Fuster
2016;():V05AT07A031. doi:10.1115/DETC2016-59305.

This paper proposes an approach for using force-controlled exploration data to update and register an a-priori virtual fixture geometry to a corresponding deformed and displaced physical environment. An approach for safe exploration implementing hybrid motion/force control is presented on the slave robot side. During exploration, the shape and the local surface normals of the environment are estimated and saved in an exploration data set. The geometric data collected during this exploration scan is used to deform and register the a-priori environment model to the exploration data set. The environment registration is achieved using a deformable registration based on the coherent point drift method. The task-description of the high-level assistive telemanipulation law (virtual fixture) is then deformed and registered in the new environment. The new model is updated and used within a model-mediated telemanipulation framework. The approach is experimentally validated using a da-Vinci research kit (DVRK) master interface and a Cartesian stage robot. Experiments demonstrate that the updated virtual fixture and the updated model allow the users to improve their path following performance and to shorten their completion time when the updated path following virtual fixture is applied. The approach presented has direct bearing on a multitude of surgical applications including force-controlled ablation.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A032. doi:10.1115/DETC2016-59314.

Motion synergies are principal components of the movement, obtained as combinations of joint degrees of freedom, that account for common postures of the human body. These synergies are usually obtained by capturing the motion of the human joints and reducing the dimensionality of the joint space with techniques such as principal component analysis. In this work, an experimental procedure to investigate the synergies of the upper body is developed and the results of the pilot study are shown.

The upper-limb kinematics includes the joint complexes of the hand, wrist, forearm, elbow, and shoulder. The different kinematic models in the literature have been reviewed, and a serial chain is considered from the upper arm. A three degree of freedom (3-DOF) linkage containing two revolute joints and one prismatic joint has been chosen to simulate the shoulder motion. A spherical joint represents the Glenohumeral (GH) joint; the elbow and ulna-radius rotations are represented by two revolute joints and the wrist is modeled with two revolute joints. The hand has a tree structure and branches into the individual phalanges, with a 2-dof MCP joint and single R joints for the rest of the phalangeal joints.

The data are collected using motion capture and the joint angles are calculated using a combination of dimensional synthesis and inverse kinematics. Principal component analysis can be used to extract the synergies for a set of previously-selected motions. The motions are performed by healthy subjects and subjects who have suffered stroke, in order to see the changes in the motion primitives. It is expected that this study will help quantify and classify some of the loss of motion due to stroke.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A033. doi:10.1115/DETC2016-59560.

Central venous catheterization (CVC) is a medical procedure where a surgeon attempts to place a catheter in the jugular, subclavian, or femoral vein. While useful, this procedure places patients at risk of a wide variety of adverse effects. Traditionally, training is performed on CVC mannequins, but these mannequins cannot vary patient anatomy. This work describes the development of a mobile training platform utilizing a haptic robotic arm and electromagnetic tracker to simulate a CVC needle insertion. A haptic robotic arm with custom syringe attachment used force feedback to provide the feeling of a needle insertion. A virtual ultrasound environment was created and made navigable by a mock ultrasound probe containing a magnetic tracking device. The effectiveness of the system as a training tool was tested on 12 medical students without CVC experience. An average increase in successful first insertion of 4.2% per practice scenario was seen in students who trained exclusively on the robotic training device. The robotic training device was able to successfully vary the difficulty of the virtual patient scenarios which in turn affected the success rates of the medical students. These results show that this system has the potential to successfully train medical residents for future CVC insertions.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A034. doi:10.1115/DETC2016-59836.

Patients that use crutches for ambulation experience forces as high as 50% of body weight and extreme extension angles at the wrist, which increases the risk of joint injury such as carpal tunnel syndrome. We have designed and fabricated a soft pneumatic sleeve to reduce the wrist loading by transferring part of the load to the forearm. The sleeve uses a Fiber Reinforced Elastomeric Enclosure (FREE). FREEs are soft pneumatic actuators that can generate force and moment upon inflation. We have used a contracting FREE, which is wrapped in a helical shape around the forearm as part of the sleeve. Upon actuation, it contracts in length and reduces in diameter, thereby generating a constricting force around the forearm.

In this paper, we describe the modeling of the constricting force generated by the helical FREE. We can model the FREE as a string due to its negligible bending stiffness. The constriction force can be expressed in terms of the axial tensile force generated in the FREE upon actuation and the geometry of the helix. To obtain the axial force, we have used a model previously reported in literature that uses a constrained volume maximization formulation. We validate the string model by comparing with experimental results.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A035. doi:10.1115/DETC2016-59913.

Transfemoral (above-knee) amputees face a unique and challenging set of restrictions to movement and function. Most notably, they are unable to medially rotate their lower-leg and subsequently cross their legs. The best and most common solution to this issue today is a transfemoral rotator, which allows medial rotation of the leg distal to the knee through a lockable turntable mechanism. However, currently available transfemoral rotators can cost thousands of dollars, and few equivalent technologies exist in the developing world. This paper, supported by the results of field studies and user testing, establishes a framework for the design of a low-cost and easily manufacturable transfemoral rotator for use in the developing world. Two prototypes are presented, each with a unique internal locking mechanism and form. A preliminary field study was conducted on six transfemoral amputees in India and qualitative user and prosthetist feedback was collected. Both prototypes successfully allowed all subjects to complete tasks such as crossing legs, putting on pants, and tying shoes while maintaining functionality of walking and standing. Future iterations of the mechanism will be guided by a combination of the most positively received features of the prototypes and general feedback suggestions from the users.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A036. doi:10.1115/DETC2016-60070.

A new, compact 2 degree-of-freedom wrist mechanism suitable for robotically controlled surgical operations is presented. Current commercially available robotically controlled instruments achieve high dexterity defined by three degrees of freedom and relatively confined swept volume at just under 1 cm in diameter. Current smaller diameter instruments result in high part count and large swept volumes (less dexterity). A mesoscale rolling contact wrist mechanism is proposed as an alternative. The crossed cylinders wrist integrates two half-cylinders whose longitudinal axes are offset by 90°. The surfaces of the half cylinders have been populated with gearing that enables the two halves to roll in two directions while preventing slip. The manufacturing of the parts is demonstrated as feasible by a the layered assembly of Carbon Nanotube (CNT) structures, which can produce parts that are difficult to replicate with traditional manufacturing methods. The resulting wrist has only 2 parts and a small swept volume.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A037. doi:10.1115/DETC2016-60499.

In this paper, we are presenting a framework for capturing human motions using Microsoft Kinect sensor for the purpose of 1) generating task positions for mechanism and robot synthesis, and 2) generation and visualization of B-spline inter-polated and approximated motion from the captured task positions. The theoretical foundation of this work lies in Kinematic Mapping, Dual and Bi-quaternions, and NURBS (Non-Uniform Rational B-spline) geometry. Lately, Kinect has opened doors for creation of natural and intuitive human-machine interactive (HMI) systems in medicine, robotic manipulation, CAD, and many other fields, where visual-sensing and -capture is a central theme. Kinect has made a huge impact in physical therapy area, achieving new benchmarks in tele-rehabilitation by improving physical exercise assessment, monitoring and supervision using the skeletal data. Moreover, Kinect’s depth sensing capability has helped in retrieving depth information required for robotic vision in grasping, object recognition which was previously done using computationally demanding computer vision algorithms. Kinect’s point cloud data with interactive gestures has proven to be useful in various CAD software for conceptual design of shapes. Mechanism synthesis is one of the areas in Kinematics, where Kinect-provided skeletal data can be leveraged to design and develop highly customized end-user collaborated mechanism solutions. We demonstrate that using Kinect, OpenGL, and Openframeworks, we can capture discrete (or, key) rigid body displacements, continuous motions, and generate and visualize rational B-spline motions from captured key positions. Capturing only a few key positions results in significant data savings and also provides a natural way to create tasks for mechanism synthesis problems. The output is a set of dual quaternions and 4 × 4 homogeneous transforms representing a task motion, which can be used as an input for mechanism synthesis applications. The tool produced also allows users to generate trajectories of various points on a moving rigid body interactively. A Kinect-based capture of such motions can help create highly-customized assistive devices for people who suffer from a range of motion-related difficulties due to old age or disabilities.

Topics: Visualization
Commentary by Dr. Valentin Fuster
2016;():V05AT07A038. doi:10.1115/DETC2016-60565.

This work presents the design and preliminary testing of a prosthetic foot prototype intended for evaluating a novel design objective for passive prosthetic feet, the Lower Leg Trajectory Error (LLTE). Thus far, all work regarding LLTE has been purely theoretical. The next step is to perform extensive clinical testing. An initial prototype consisting of rotational ankle and metatarsal joints with constant rotational stiffness was optimized and built, but at 2 kg it proved too heavy to use in clinical testing. A new conceptual foot architecture intended to reduce the weight of the final prototype is presented and optimized for LLTE. This foot consists of a rotational ankle joint with constant stiffness of 6.1 N·m/deg, a rigid structure extending 0.08 m from the ankle-knee axis, and a cantilever beam forefoot with bending stiffness 5.4 N·m2. A prototype was built using machined delrin for the rigid structure, three parallel extension springs offset along a constant radius cam from a pin joint ankle, and machined nylon as the beam forefoot. In preliminary testing, it was determined that, despite efforts to minimize weight and size, this particular design was still too heavy and bulky as a result of the extension springs to be used in extensive clinical testing. Future work will focus on reducing the weight further by replacing linear extension springs with flexural elements before commencing with the clinical study.

Commentary by Dr. Valentin Fuster

40th Mechanisms and Robotics Conference: Mobile Robots, Motion Planning, Dynamics and Control

2016;():V05AT07A039. doi:10.1115/DETC2016-59231.

Usually, the accuracy of parallel manipulators depends on the architecture of the robot, the design parameters, the trajectory planning and the location of the path in the workspace. This paper reports the influence of static and dynamic parameters in computing the error in the pose associated with the trajectory planning made and analyzed with the Orthoglide 5-axis. An error model is proposed based on the joint parameters (velocity and acceleration) and experimental data coming from the Orthoglide 5-axis. Newton and Gröbner based elimination methods are used to project the joint error in the workspace to check the accuracy/error in the Cartesian space. For the analysis, five similar trajectories with different locations inside the workspace are defined using fifth order polynomial equation for the trajectory planning. It is shown that the accuracy of the robot depends on the location of the path as well as the starting and the ending posture of the manipulator due to the acceleration parameters.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A040. doi:10.1115/DETC2016-59359.

A comparative study on the pick-and-place trajectories for high-speed Delta robots is presented in this paper. The Adept Cycle has been widely accepted as a standardized pick-and-place trajectory for industrial robots. The blending curves and optimization methods to smooth this trajectory are briefly surveyed. Three major types of trajectories: Lamé curves, clothoids and piecewise polynomials, are selected as candidates to be compared. The processes to generate these trajectories are briefly reviewed. The trajectories are firstly compared in term of their computation time. Then, based on a dynamic model and an experimental prototype of the Delta robot, different combinations of the geometric paths and motion profiles are compared in terms of power consumption, terminal state accuracy and residual vibration. The effects of trajectory configurations and parameters on the robot’s dynamic performances are investigated. Through a comprehensive analysis on both simulation and experimental results, a near-optimal pick-and-place trajectory for the Delta robot is identified and validated.

Topics: Robots
Commentary by Dr. Valentin Fuster
2016;():V05AT07A041. doi:10.1115/DETC2016-59384.

This paper presents a new cost effective wireless telemetry system capable of estimating ambient air turbulence using RC helicopters. The proposed telemetry system correlates the RC helicopter’s flight dynamics with ship air wake patterns generated by cruising naval vessels. The telemetry system consists of two instrumentation units each equipped with aviation grade INS/IMU sensors to measure dynamics of the helicopter with respect to the concerned naval vessel. The presented telemetry system extracts ship air wake patterns by removing the helicopter dynamic effects from actual measurements. This paper presents a comprehensive comparison between popular machine learning algorithms in eliminating effects of pilot inputs from helicopter’s dynamics measurements. The system was tested on data collected in a wide range of wind conditions generated by modified YP676 naval training vessel in the Chesapeake Bay area over a period of more than a year.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A042. doi:10.1115/DETC2016-59563.

In this paper, we present dead-beat control of a torso-actuated rimless wheel model. We compute the steady state walking gait using a Poincaré map. When disturbed, this walking gait takes a few steps to cancel the effect of the disturbance but our goal is to develop a faster response. To do this, we develop an event-based, linear, discrete controller designed to cancel the effect of the disturbance in a single step — a one-step dead-beat controller. The controller uses the measured deviation of the stance leg velocity at mid-stance to set the torso angle to get the wheel back to the limit cycle at the following step. We show that this linear controller can correct for a height disturbance up to 3% leg length. The same controller can be used to transition from one walking speed to another in a single step. We make the model-based controller insensitive to modeling errors by adding a small integral term allowing the robot to walk blindly on a 7° uphill incline and tolerate a 30% added mass. Finally, we report preliminary progress on a hardware prototype based on the model.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A043. doi:10.1115/DETC2016-59658.

In this paper, a hybrid controller for robotic arms is proposed and designed by combining a proportional-integral-derivative controller (PID) and a model reference adaptive controller (MRAC) in order to further improve the accuracy and joint convergence speed performance. The convergence performance of the PID controller, the model reference adaptive controller and the PID+MRAC hybrid controller for 1-DOF and 2-DOF manipulators are compared. The comparison results show that the convergence speed and its performance for the MRAC and the PID+MRAC controllers are better than that of the PID controller, and the convergence performance for the hybrid control is better than that of the MRAC control.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A044. doi:10.1115/DETC2016-59676.

A three-dimensional criterion is provided for the estimation of balance stability states of legged robotic systems subject to various constraints. A general framework is established to evaluate the balance stability boundary of a given system in the state space of Center of Mass (COM) Cartesian position and velocity. For each assigned COM initial position, an optimization-based iterative algorithm finds the minimum and maximum COM initial velocity that the system can handle along a given direction, such that it maintains the capability to reach a final static equilibrium. The resulting set of velocity extrema constitutes the system’s balance stability boundary, which represents the sufficient condition to estimate falling states versus balanced states, according to the definitions provided herein. The COM state space domain identified with this approach contains all possible balanced states for the given legged system, with respect to the necessary physical, balancing, and design constraints. The balance state estimation is demonstrated for 1- and 2-degrees of freedom planar legged systems in single support. The domain identified by the balance stability boundary can be used as a “map” for the given legged system in which the distance from a given state to the domain boundaries can provide a quantitative measure of balance stability/instability.

Topics: Stability , Robotics
Commentary by Dr. Valentin Fuster
2016;():V05AT07A045. doi:10.1115/DETC2016-59842.

Municipal solid waste (MSW), generated at an unprecedented rate due to rapid urbanization and industrialization contains useful recyclable materials like metals, plastic, wood, etc. Recycling of useful materials from MSW in the developing countries is severely constrained by limited door-to-door collection and poor means of segregation. Recovery of recyclables is usually performed by waste pickers, which is highly risky and hazardous for their health. This paper reports the development of a robotic mobile manipulation system for automated sorting of useful recyclables from MSW. The developed robot is equipped with a thermal imaging camera, proximity sensor and a 5-DOF robotic arm. This paper presents an approach for sorting based on automated identification from thermographic images. The developed algorithm extracts keypoint features from the thermographic image and feeds into clustering model to map them into a bag-of-word vectors. Finally, Support Vector Machine (SVM) classifier is used for identifying the recyclable material. We used the developed algorithm to detect three categories of recyclables namely, aluminum can, plastic bottle and tetra pack from given thermographic images. We obtained classification rate of 94.3% in the tests. In future, we plan to extend the developed approach for classifying a wider range of recyclable objects as well as to incorporate motion planning algorithms to handle cluttered environments.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A046. doi:10.1115/DETC2016-59984.

Swarm robotic systems can offer many advantages including robustness, flexibility and scalability. However one of the issues relating to overall swarm performance that needs to be considered is hardware variations inherent in the implementation of individual swarm robots. This variation can bring behavioral diversity within the swarm, resulting in uncontrollable swarm behaviors, low efficiency, etc. If swarm robots could be separated by behaviors, operational advantages could be obtained. In this paper we report an approach to the sorting of large robotic swarms using an approach inspired by chromatography. Hence the tedious and expensive calibration process can be avoided. The results investigate the influence of the internal control parameters, together with environmental effects on the robotic behavioral sorting. We concluded that if the robot has knowledge of previous events coupled with a specific arena pattern density will offer improved behavioral sorting.

Topics: Robots
Commentary by Dr. Valentin Fuster
2016;():V05AT07A047. doi:10.1115/DETC2016-60006.

Teleoperated unmanned ground vehicles are very useful in environments that are hazardous for humans. When controlled manually, speed of operation can be very slow due to degraded and delayed feedback of information to/from the vehicle’s environment. Adding autonomy to the vehicle can make control for the human teleoperator easier and improve performance. This paper presents a semi-autonomous control method for avoiding collisions while driving a vehicle. The method is well suited for small unmanned ground vehicles in unstructured environments (i.e. environments without predefined roads/paths to follow). The semi-autonomous control method and the effect of communication latency are evaluated with a human subject study (N = 20) involving teleoperation of a simulated robot search task. Results show that while semi-autonomy does improve performance at low communication latency, the improvement is much larger at higher latencies.

Topics: Vehicles
Commentary by Dr. Valentin Fuster
2016;():V05AT07A048. doi:10.1115/DETC2016-60060.

The stability and trajectory control of a quadrotor carrying a suspended load with a fixed known mass has been extensively studied in recent years. However, the load mass is not always known beforehand in practical applications. This mass uncertainty brings uncertain disturbances to the quadrotor system, causing existing controllers to have a worse performance or to be collapsed. To improve the quadrotor’s stability in this situation, we investigate the impacts of the uncertain load mass on the quadrotor. By comparing the simulation results of two controllers — the proportional-derivative (PD) controller and the sliding mode controller (SMC) driven by a sliding mode disturbance of observer (SMDO), the quadrotor’s performance is verified to be worse as the uncertainty increases. The simulation results also show a controller with stronger robustness against disturbances is better for practical applications.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A049. doi:10.1115/DETC2016-60152.

This paper demonstrates an approach for predicting and optimizing energy consumption in skid-steer mobile robots (SSMRs) conducting manufacturing tasks. This work is unique in that it considers the energy associated with real-time predictions of slipping in the SSMR and further considers a specific application in which the SSMR is operating in an inverted (climbing) configuration on metal surfaces with homogeneous properties. The approach is based on a dynamic model that provides estimates of SSMR slipping motion during simulation. The model is used to estimate the underlying components of energy and will serve as the tool for objective function evaluation. The approach will follow previous path optimization strategies, parameterizing the path to provide design parameters and using appropriate optimization tools. A method to select the desired trajectory prior to conducting a manufacturing task is demonstrated. This paper primarily focuses on a scenario in which a climbing SSMR maneuvers on a steel surface by means of magnetic-based tracks with strong adhering forces. For this case, the friction due to slipping represents the primary source of energy consumption. This implies that the path selection is the most important parameter for the optimization.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A050. doi:10.1115/DETC2016-60303.

Mobile robotic systems are advancing manufacturing operations in fields that generally exhibit less automation such as shipbuilding, pipe inspection, and construction applications on non-planar surfaces. Mobile robots operating in such environments are typically required to assume climbing configurations to complete desired tasks. These tasks are usually considered planar in nature, however, in practice are generally non-planar. A common task seen on non-planar surfaces is the welding of ship hulls. This process consists of welding segments together and is normally completed by a skilled laborer due to the complexity of the surface. Through the advancement of kinematic modeling of mobile robots there exists the ability to develop future platforms with the potential to perform efficient operations on non-planar surfaces. While the majority of kinematic models presented for mobile robots assume operations on planar surfaces, a number of studies consider kinematic behavior on non-planar surfaces. These past works generally take one of two approaches: developing assumed modifications to the existing kinematic constraints as algebraic equations, or making use of a set of differential equations describing the instantaneous motion of the contact point between non-planar surfaces. The second approach is more general and shown to be applicable for both general and specific terrains. However, the previous works main focus is on differential-steer platforms with a passive castor. Conversely, Skid-Steer mobile robots, (SSMR), provide simple, robust platforms that have several features making them well suited to manufacturing tasks. This paper will present a kinematic model for an SSMR operating on a non-planar, nominally spherical surface with a method readily generalized to other surface geometries.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A051. doi:10.1115/DETC2016-60545.

Due to high degrees of freedom of humanoids and induced redundancy, there are multiple ways of performing a given manipulation task. Finding optimal ways of performing tasks is one desirable property of any motion planning framework. This includes optimizing the path with respect to a certain objective function. Additionally, a variety of constraints need to be satisfied such as stability, self-collision and collision with objects in the environment and also kinematic closed-loop chains formed during the task. Time requirements of the planner is another important aspect that drives us to use sampling based methods. In this paper, we present an asymptotically optimal sampling based approach for generating statically stable motion plans. We use RRT*-connect algorithm which we obtained by modifying RRT-Connect. Moreover, we use a gradient based inverse kinematics solver to generate goal configurations. We evaluate the efficacy of our approach in the results section in a simulation environment on Hubo+ robot model. The results show a significant improvement in path costs as well as overall optimality of the given task.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A052. doi:10.1115/DETC2016-60547.

This paper presents a sampling-based method for path planning in robotic systems without known cost-to-go information. It uses trajectories generated from random search to heuristically learn the cost-to-go of regions within the configuration space. Gradually, the search is increasingly directed towards lower cost regions of the configuration space, thereby producing paths that converge towards the optimal path. The proposed framework builds on Rapidly-exploring Random Trees for random sampling-based search and Reinforcement Learning is used as the learning method. A series of experiments were performed to evaluate and demonstrate the performance of the proposed method.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A053. doi:10.1115/DETC2016-60550.

This paper presents the design, analysis and testing of a fully actuated modular spherical tensegrity robot for co-robotic and space exploration applications. Robots built from tensegrity structures (composed of pure tensile and compression elements) have many potential benefits including high robustness through redundancy, many degrees of freedom in movement and flexible design. However to fully take advantage of these properties a significant fraction of the tensile elements should be active, leading to a potential increase in complexity, messy cable and power routing systems and increased design difficulty. Here we describe an elegant solution to a fully actuated tensegrity robot: The TT-3 (version 3) tensegrity robot, developed at UC Berkeley, in collaboration with NASA Ames, is a lightweight, low cost, modular, and rapidly prototyped spherical tensegrity robot. This robot is based on a ball-shaped six-bar tensegrity structure and features a unique modular rod-centered distributed actuation and control architecture.

This paper presents the novel mechanism design, architecture and simulations of TT-3, the first untethered, fully actuated cable-driven six-bar tensegrity spherical robot ever built and tested for mobility. Furthermore, this paper discusses the controls and preliminary testing performed to observe the system’s behavior and performance.

Topics: Robots , Design , Tensegrity
Commentary by Dr. Valentin Fuster

40th Mechanisms and Robotics Conference: Novel Mechanisms, Robots and Applications

2016;():V05AT07A054. doi:10.1115/DETC2016-59111.

The flying style of bats has much difference with the birds and insects, which adopt the backward folding movement of the wing when up flapping. The wingspan is changed during the up and down flapping, which makes the effective flapping area difference and the net lift increase. Firstly, basing on the research of bats’ flapping style, the mechanism of active morphing wing is proposed, then the dimensional synthesis is carried out basing on the movement trajectory of bats’ wing, after that, the kinematic model is build and analyzed, and the analysis result is compared with the ADAMS software. The flapping and morphing of the wing is actuated by a single motor, which can increase the power coefficient of the system and realize the coupled flapping and folding motion of the wing at the same time. The folding and stretching of the wing is actuated by a cam installed on the axis of crank, then the space flapping trajectory of the wing can be planed by changing the cam contour and the installation phase, this mechanism provide a way to design the foldable flapping wing aerial vehicles (FWAV).

Topics: Design , Wings
Commentary by Dr. Valentin Fuster
2016;():V05AT07A055. doi:10.1115/DETC2016-59218.

Balancing stiffness and weight is of substantial importance for antenna structure design. Conventional fold-rib antennas need sufficient weight to meet stiffness requirements. To address this issue, this paper proposes a new type of cable-rib tension deployable antenna that consists of six radial rib deployment mechanisms, numerous tensioned cables, and a mesh reflective surface. The primary innovation of this study is the application of numerous tensioned cables instead of metal materials to enhance the stiffness of the entire antenna while ensuring relatively less weight. Dynamic characteristics were analyzed to optimize the weight and stiffness of the antenna with the finite element model by subspace method. The first six orders of natural frequencies and corresponding vibration modes of the antenna structure are obtained. In addition, the effects of structural parameters on natural frequency are studied, and a method to improve the rigidity of the deployable antenna structure is proposed.

Topics: Cables , Tension
Commentary by Dr. Valentin Fuster
2016;():V05AT07A056. doi:10.1115/DETC2016-59268.

Advanced actuation methods are needed in legged robots in order to build robust and efficient robotic systems. State of the art robots either consume much more energy than their biological counterparts or are dramatically less mobile. Advanced actuation methods are necessary to achieve both efficiency and mobility. Many highly mobile legged robots are actuated in serial, but serial actuation has many known weaknesses. This research explores a new and promising method of actuation that is a hybrid of serial and parallel actuation. This method is able to draw from the large body of research conducted on parallel manipulators over the last several decades. This research has shown that parallel manipulators can offer many advantages over serial arms including: smaller mobile mass, more rigidity, faster end effector speeds, and large force capacity. All of these advantages are well suited for the requirements of legged robots. In this paper, the authors detail the implementation of this advanced actuation method from conceptualization to the first stages of testing. It details the choice of configuration, which was important, and somewhat counter intuitive. It also walks through the kinematic solutions, showing relatively simple solutions to challenging problems. The goal of the work is to use multiple, small motors in parallel to actuate the hip and the knee. In this way, during the stance phase of gait, multiple motors can be used in parallel to provide a powerful burst for push-off. Our two-link parallel structure allows the motors to cross multiple joints and therefore can be used to actuate several joints at once. In addition, by mounting motors at the base, the inertia of the leg is greatly reduced.B@Creating a fast, efficient leg structure is the first step in our project. The higher level goal of this research is to create a quadruped robot that is designed for efficient and fast running. The novel leg structure described in this paper will be capable of the types of motions associated with high speed gait. The robot needs to be capable of both high speed motions and high force output, without being excessively heavy. It should also be capable of accurate three dimensional control, and meet certain manipulability criterion. In this paper we show a functional and promising 3D printed leg prototype. This paper will provide a detailed description of this unique approach to actuation. It will also show the solution to the kinematic equations. Finally, as a proof of concept, the leg was moved in a gait pattern over a treadmill.

Topics: Robotics
Commentary by Dr. Valentin Fuster
2016;():V05AT07A057. doi:10.1115/DETC2016-59273.

A natural snake can navigate lots of diverse environments owing to their extreme agility and hyper-redundancy. However, earlier snake robot designs are inadequate to imitate the living snake locomotion comprehensively, since the deficiency of mobility in each single module. The application of parallel mechanism in snake robot can provide considerable dexterity and support-ability to overcome the aforementioned drawback. This paper presents a bionic parallel module for snake robot inspired by the anatomy of biological snake. To generate four distinct gaits of living snake, three motion screws of the mechanism are obtained via mobility analysis. Further, a kinematic model of this mechanism is investigated by reciprocal screw and Lie algebra aimed to evaluate the kinematic performance in an efficient and accurate scheme, which facilitates real-time motion control. Finally, a numerical result using this method is supplied, and its effectiveness is corroborated by kinematic simulation of ADAMS.

Topics: Kinematics , Robots , Screws
Commentary by Dr. Valentin Fuster
2016;():V05AT07A058. doi:10.1115/DETC2016-59290.

This paper presents forward and inverse position kinematics equations and analytical solutions for the 2-dof RRSSR Parallel Robot. Two ground-mounted perpendicular offset revolute (R) joints are actuated via servomotors, and the single-loop parallel robot consists of passive R-S-S (revolute-spherical-spherical) joints in between the active joints. A study of the multiple solutions in each case is presented, including means to select the appropriate solutions. This rigid-link parallel robot forms the hip joints of the Ohio University RoboCat walking quadruped. The methods of this paper are suitable to assist in design, simulation, control, and gait selection for the quadruped. RoboCat hardware has been built and used to help validate the examples and results of this paper.

Topics: Kinematics , Robots , Hardware
Commentary by Dr. Valentin Fuster
2016;():V05AT07A059. doi:10.1115/DETC2016-59291.

This paper describes the spatial three-dof 3-SUR 1-RU spherical Parallel Platform Robot. This type of robot has been previously proposed by other authors, but the present design, platform-mounted actuators, and application are unique. Further, the inverse kinematics problem is solved analytically. This robot is under development at Ohio University to serve as the active orienting device for aerodynamic testing of unmanned aerial vehicles (UAV) with up to 3 m wingspan. The UAV will be tested on a Windmobile which is a ground vehicle that is driven with the test article on an instrumented truss extended in the front in an undisturbed flow field. This system is an inexpensive substitute for a large-scale wind tunnel for measuring aerodynamic parameters of the UAV.

The three-degrees-of-freedom (dof) of the platform robot are actively controlled by three servomotors (R joints) mounted to the underside of the moving platform and there is a passive fourth middle leg with passive R-U joints for support. The inverse orientation kinematics (IOK) problem is formulated and solved analytically in this paper. Given the three desired Euler Angles, the three required actuator angles are found. Geometrically this analytical solution is equivalent to finding the intersection point of two circles on different planes, independently for each of the three platform robot legs. The analytical solution requires finding the roots of a quartic polynomial. There are at most two real solutions (elbow-up and elbow-down) which means that there are always at least two imaginary solutions to the IOK problem, which are discarded. Examples are presented to demonstrate the platform robot IOK solution algorithm for use in practical platform robot control.

Topics: Kinematics , Robots
Commentary by Dr. Valentin Fuster
2016;():V05AT07A060. doi:10.1115/DETC2016-59386.

This paper presents the design and analysis of a bioinspired miniature modular Inchworm robot. Inchworm robots play crucial roles in surveillance, exploration and search and rescue operations where maneuvering in confined spaces is required. Rectilinear gaits have been demonstrated with favorable results in terms of stability and small size due to the absence of wheels and tracks; however, exhibit slow speeds. The proposed mechanism utilizes undulatory rectilinear gait motion through linear expansion/contraction of modules and anisotropic friction skin to produce pure linear motion. The use of anisotropic friction skin results in a simple, low cost, miniature mechanical structure. Friction analysis of the anisotropic material is performed and the system is modeled to derive its equations of motion. Modeling and simulation results are validated through experiments performed with an integrated prototype. Results indicate that the robot can achieves an average forward velocity of 11 mm/s on various surfaces.

Topics: Robots , Design
Commentary by Dr. Valentin Fuster
2016;():V05AT07A061. doi:10.1115/DETC2016-59387.

This paper presents the design and analysis of a novel Discrete Modular Serpentine Tail for mobile legged robotic systems. These systems often require an inertial appendage to generate forces and moments to provide a means of improved performance in terms of stabilization, maneuvering and dynamic self-righting in addition to enhancing manipulation capabilities. The majority of existing tail designs consist of planar pendulums that limit improved performance to specific planes due to limited articulation. The proposed system consists of a modular two degree of freedom, spatial mechanism constructed from rigid segments actuated by cable tension and displacements whose curvatures are dependent on a multi-diameter pulley. Modules can be interconnected in series to achieve multiple spatial curvatures; thus, can bring about multi-planar improved performance and enhanced manipulation capabilities to the overall robotic system. First, the detailed design is presented after which the forward kinematics of the mechanism is derived to analyze both the kinematic coupling between the segments and the influence between the ratio of segment lengths and pulley diameters. The equations of motion are derived and modified due to cable tension driving segments and are used to determine torque requirements of the system to aid the design process for motor selection. Multi-objective optimal kinematic synthesis is then formulated and presented as a case study for synthesizing physical dimensions of the mechanism to achieve the best fit of user defined tail curvatures.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A062. doi:10.1115/DETC2016-59388.

This paper presents the design and analysis of a reduced degree-of-freedom Robotic Modular Leg (RML) mechanism used to construct a quadruped robot. This mechanism enables the robot to perform forward and steering locomotion with fewer actuators than conventional quadruped robots. The RML is composed of a double four-bar mechanism that maintains foot orientation parallel to the base and decouples actuation for simplified control, reduced weight and lower cost of the overall robotic system. A passive suspension system in the foot enables a stable four-point contact support polygon on uneven terrain. Foot trajectories are generated and synchronized using a trot and modified creeping gait to maintain a constant robot body height, horizontal body orientation, and provide the ability to move forward and steer. The locomotion principle and performance of the mechanism are analyzed using multi-body dynamic simulations of a virtual quadruped and experimental results of an integrated RML prototype.

Topics: Design , Robotics
Commentary by Dr. Valentin Fuster
2016;():V05AT07A063. doi:10.1115/DETC2016-59438.

This article discusses the concept of using an industrial robot arm platform for additive manufacturing. The concept being explored is the integration of existing additive manufacturing process technologies with an industrial robot arm to create a 3D printer with a multi-plane layering capability. The objective is to develop multi-plane toolpath motions that will leverage the increased capability of the robot arm platform compared to conventional gantry-style 3D printers. This approach enables print layering in multiple planes whereas existing conventional 3D printers are restricted to a single toolpath plane (e.g. x-y plane). This integration combines the fused deposition modeling techniques using an extruder head that is typically used in 3D printing and a 6 degree of freedom robot arm. Here, a Motoman SV3X is used as the platform for the robot arm. A higher level controller is used to control the robot and the extruder. To communicate with the robot, MotoCom SDK libraries is used to develop the interfacing software between the higher level controller and the robot arm controller. The integration of these systems enabled multi-plane toolpath motions to be utilized to produce 3D printed parts. A test block has been 3D printed using this integrated system.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A064. doi:10.1115/DETC2016-59526.

In recent years, applications in industrial assemblies within a size range from 0.5mm to 100mm are increasing due to the large demands for digital multimedia products. Research on grippers or robotic hands within the mesoscopic scale of this range has not been well explored. This paper proposes a mesoscopic scale gripper (meso-gripper) which has two modes: passive adjusting mode and an angled precision gripping mode. The gripper adjusts its shape automatically according to the appropriate mode. This form of gripping and the associated mechanism are novel in their implementation and operation. The meso-gripper which has metamorphic characteristics is generated by integrating a remote center of motion (RCM) mechanism with a cross four-bar (CFB) linkage. The dimensional synthesis of the gripper is outlined for a specified task-based gripping followed by the analysis of the synthesizing mechanism. A differential mechanism is adopted to increase the flexibility of the meso-gripper. Prototype is fabricated and tested using 3D printing technology to verify the feasibility of the design.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A065. doi:10.1115/DETC2016-59549.

A gravity equilibrator is a statically balanced system which is designed to counterbalance a mass such that any preferred position is eliminated and thereby the required operating effort to move the mass is greatly reduced. Current spring-to-mass gravity equilibrators are limited in their range of motion as a result of design limitations. An increment of the range of motion is desired to expand the field of applications. The goal of this paper is to present a compact one degree of freedom mechanical gravity equilibrator that can statically balance a rotating pendulum over an unlimited range of motion. Static balance over an unlimited range of motion is achieved by a coaxial gear train that uses non-circular gears. These gears convert the continuous rotation of the pendulum into a reciprocating rotation of the torsion bars. The pitch curves of the non-circular gears are specifically designed to balance a rotating pendulum. The gear train design and the method to calculate the parameters and the pitch curves of the non-circular gears are presented.

A prototype is designed and built to validate that the presented method can balance a pendulum over an unlimited range of motion. Experimental results show a work reduction of 87 % compared to an unbalanced pendulum and the hysteresis in the mechanism is 36 %.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A066. doi:10.1115/DETC2016-59643.

The current rate of incidence of cataracts is increasing faster than treatment capacity, and an autonomous robotic system is proposed to mitigate this by carrying out cataract surgeries. The robot is composed of a three actuator RPS parallel mechanism in series with an actuated rail mounted roller that moves around the eye, and is designed to perform a simplified version of the extracapsular cataract surgery procedure autonomously. The majority of the design work has been completed, and it is projected that the system will have a tool accuracy of 0.167 mm, 0.141 mm, and 0.290 mm in the x, y, and z directions, respectively. Such accuracies are within the acceptable errors of 1.77mm in the x and y directions of the horizontal plane, as well as 1.139 mm in the vertical z direction. Tracking of the tool when moving at 2 mm/s should give increments of 0.08 mm per frame, ensuring constant visual feedback. Future work will involve completing construction and testing of the device, as well as adding the capability to perform a more comprehensive surgical procedure if time allows.

Topics: Robotics , Surgery
Commentary by Dr. Valentin Fuster
2016;():V05AT07A067. doi:10.1115/DETC2016-59674.

A mechanism approach is presented in this paper to deal with machining errors and model the accuracy of a precision transmission device in connection with kinematic geometry. The 3D motion of a rotor with six DOFs is perfectly represented by a redundant mechanism [1]. Positions and orientations of two rotors are determined by solving the vector equations of the redundant mechanisms at different instants. The geometric properties of loci traced by the characteristic points and lines of the rotors are analyzed. The invariants of the discrete line-trajectories, the image spherical curve and striction curve, are introduced into the accuracy evaluation for the precision transmission device. The rotary table of a machine tool is used as an example to test the proposed model. The results show that the kinematic geometry is advantageous in modeling effects of errors in multiple body mechanical systems.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A068. doi:10.1115/DETC2016-59837.

In-hand manipulation is a frequently demanded task which requires a significant dexterity from grippers. Operations such as object twisting, re-grasping and re-positioning with correct posture after manipulation are the major industrial challenges. Such requiring also determine design complexity of grippers. This paper proposes a new modular two DOF finger which is capable to do manipulation such as twist object about two independent axes when used in modular assembled configuration. Multiple identical fingers of such type can be used to build the gripper whose primary purposes are solving manipulation and after manipulation requirements such as regrasp and release object with appropriate posture. The fingers are implemented in the gripper by means of a properly conceived mechanism to ensure the mobility needed for grasping. In this research, the manipulation capabilities of the gripper developed by such identical fingers is investigated by the means of simulation in a multibody simulated environment. Moreover, a prototype of one finger has been built for preliminary inspection of the modular entity which represents the constructive base of the gripper concept object of this study.

Topics: Grippers
Commentary by Dr. Valentin Fuster
2016;():V05AT07A069. doi:10.1115/DETC2016-59930.

This paper presents a single-degree-of-freedom (single-DoF) gravity balancer that can deal with variable payloads. The proposed design is made of a standard spring-based statically-balanced mechanism and a spring adjusting mechanism. The installation points of the balancing spring are controlled by two cables. When the payload is applied, the spring adjusting mechanism will drive the two cables to regulate the spring installation points to suitable locations for balancing purpose. The significant novelty of the proposed design is that the balancer can sense the change of the payload and then automatically regular its spring attachment, which are all done by pure mechanical solution, i.e., with no electrical sensor or actuator. A prototype is built up to test the proposed design.

Topics: Gravity (Force)
Commentary by Dr. Valentin Fuster
2016;():V05AT07A070. doi:10.1115/DETC2016-59977.

Applications of deployable mechanisms can be found in aeronautic and civil engineering, often in the creation of unfolding large-scale structures with curved surfaces. This paper proposes novel mechanical networks, which are used to approximate three-dimensional surfaces, such as cuboids, ellipsoids, or hyperboloids. Each such deployable structure is assembled from unit Sarrus and scissor linkages of different sizes, has several decoupled degrees of freedom, and can take any shape within a different family of parameterized surfaces. Each degree of freedom controls a separate parameter in the equation describing the physical boundary of the linkage network. The size and placement of the unit linkages and their elements are analyzed and selected for obtaining the expected families of surfaces. CAD models and kinematic simulations demonstrate the abilities of the mechanisms to perform dynamically the desired approximation.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A071. doi:10.1115/DETC2016-60291.

This work presents a series of DNA-structured linear actuators that have high displacements and compact profiles. These actuators operate by twisting and untwisting a double helix that resembles a DNA molecule. Unlike most similarly-motivated twisted string actuators (TSAs), these DNA-structured actuators can have the ability to exert both push and pull forces on a load. Thus, although originally designed for cable-driven robotics, these actuators have the ability to work as part of many different mechatronic systems. Two inherently different actuator designs were investigated, one with straight-line edges (rails) and one with helical rails. Two mathematical models of angular rotation versus linear displacement were developed and simulated, one for each design, and three prototypes were constructed to validate the models. The final prototype was tested for displacement, restorative torque, and pull force characteristics. This last prototype showed a 30.5 cm stroke for a 40.5 cm actuator, or a displacement of 75.3% of its total length.

Topics: Actuators , DNA
Commentary by Dr. Valentin Fuster
2016;():V05AT07A072. doi:10.1115/DETC2016-60354.

Dexterous in-hand manipulation tasks have been difficult to execute, even with highly complex hands and control schemes, as the object grasp stability needs to be maintained while it is displaced in the hand workspace. Researchers have shown that underactuated, adaptive hand designs can effectively immobilize objects with simple, open-loop, but there have been few cases where underactuation has been leveraged to enhance in-hand manipulation. In this work, we investigate the performance of a gripper utilizing a thumb with an active, belt-driven, conveyor surface and an opposing, underactuated finger with passive rollers, for a variety of manipulation tasks and range of objects. We show that consistent, repeatable object motion can be obtained while ensuring a rigid grasp without a priori knowledge of the object geometry or contact locations, due to the adaptive qualities of underactuated design. Many dexterous in-hand manipulation examples with their anthropomorphic equivalents are examined, and simple, open-loop control schemes to optimize the repeatability of these tasks are proposed.

Topics: Grippers
Commentary by Dr. Valentin Fuster
2016;():V05AT07A073. doi:10.1115/DETC2016-60379.

In this work, we investigate the integration of ultrathin galvanic cell batteries with high energy density and flexibility into the highly deformable wings of the flapping wing air vehicle (FWAV) known as “Robo Raven” that we previously developed for independent wing control. The goal of this research was to create a multifunctional wing structure that provides higher energy density than the existing, singular function, lithium polymer batteries currently being used to power the platform. The key areas of inquiry explored are the effect the integration of batteries has on the aerodynamic forces generated during flapping under simulated flight conditions, and whether there is an adverse effect on flight performance where the platform payload capacity is diminished for similar flight time. Upon investigation, we determine that the electrical performance of the battery is as expected after integration into the wing structure, while force generation is not significantly affected, which enhances flight time enhancement and/or payload capacity.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A074. doi:10.1115/DETC2016-60387.

Flapping wing unmanned aerial vehicles (FWUAVs) provide an alternative to traditional platforms because they are more maneuverable than fixed wing platforms while being faster, quieter, and more natural looking than rotary wing platforms. While real birds are able to execute complex and highly controlled aerobatic maneuvers, executing FWUAV aerobatics presents unique challenges due to difficulty in execution of controlled quick orientation change. This paper demonstrates a simple method for using a large 2 degree of freedom tail for quick orientation changes and flight control, enabling execution of a pre-programmed backflip maneuver on the Robo Raven V, a hybrid FWUAV. The platform reached angular velocities of up to 420° per second during the maneuver.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A075. doi:10.1115/DETC2016-60495.

Cable sag can have significant effects on the cable length computation in a cable-suspended robot and this is more pronounced in large-scale outdoor systems. This requires modeling the cable as a catenary instead of an approximated straight-line model. Furthermore, when there is actuation redundancy involved, the modeling and simulation of the system becomes much more complex, requiring optimizing routines to solve the problem.

A cable-sag-compensated (catenary) model was implemented in simulation for an example large outdoor cable-suspended robot system to solve the coupled kinematics and statics problems. This involved optimization of cable tensions and finding the errors involved in the cable length. A comparative analysis between the straight-line and cable sag model is presented, the main contribution of this paper. Based on the qualitative and quantitative results obtained, recommendations were made on the choice of model and solution methodologies.

Commentary by Dr. Valentin Fuster
2016;():V05AT07A076. doi:10.1115/DETC2016-60571.

Flapping wing flight is a challenging system integration problem for designers due to tight coupling between propulsion and flexible wing subsystems with variable kinematics. Due to the fluid-structure interactions present in such a system, models must be tailored to a particular design instantiation to provide high accuracy and a clear picture of underlying physical phenomena. However, a practical design approach requires an extensible model that enables exploration of several design alternatives. The difficulty of generating models that are both highly accurate and extensible suggest a combined experimental and simplified modeling approach may offer a more tractable approach to system design and integration. However, experimental data on flapping wing air vehicles that is collected in a static laboratory test or a wind tunnel test is limited because of the rigid mounting of the vehicle, which alters the natural body response to flapping forces generated. Therefore, we undertake the design of a flapping wing air vehicle system that is instrumented to provide data that may be used to create and validate a simplified aerodynamics model that is capable of freely flying. The sensor suite includes measurements of attitude, heading, altitude, position, wing angle, as well as voltage and current supplied to the drive motors. With this approach, a complete energetic picture of flight is constructed, and by varying the parameters of the vehicle, the envelope of feasible performance is investigated. Finally, the results of the experimental testing are compared to a simplified aerodynamic model to establish the effectiveness of the proposed approach to system design.

Topics: Vehicles , Wings , Flight
Commentary by Dr. Valentin Fuster
2016;():V05AT07A077. doi:10.1115/DETC2016-60575.

This paper presents a novel robot fish propelled by an active and compliant propulsion mechanism. The key innovation of this robot fish is the combination of an active wire-driven mechanism with a soft compliant tail to construct the active compliant propulsion mechanism, which can accomplish multi-modal swimming motions. First, the design method was proposed, the wire-driven mechanism and the compliant tail could be well designed. Second, using this robot fish experimental platform, numerous experiments were conducted to investigate the effect of different controllable parameters on cruising speed, descending speed and turning performance. These parameters include flapping frequency and amplitude of the propulsion mechanism, attack angle of the pectoral fins. A more detailed parametric study was conducted with these significant parameters to study and understand the relationship between swimming performance and various parameters. This process can help to optimize controllable parameters for superior swimming performance. Based on the parametric study, we obtained the best experimental swimming performance under optimized parameters; the maximum speed reached 2.15 BL/s (body length per second), the maximum turning speed is 269°/s the descending speed is 42 cm/s (when attack angle is 60 degree). Compared with existing robot, the new robot fish has several advantages: it is simple in structure, easy to control, and capable of high speed swimming and maneuverable swimming.

Topics: Robots , Propulsion
Commentary by Dr. Valentin Fuster

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