ASME Conference Presenter Attendance Policy and Archival Proceedings

2018;():V04BT00A001. doi:10.1115/IMECE2018-NS4B.

This online compilation of papers from the ASME 2018 International Mechanical Engineering Congress and Exposition (IMECE2018) 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presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.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

Dynamics, Vibration, and Control: Multi-Physics Dynamics-Control and Diagnostics-Prognostics of Structures

2018;():V04BT06A001. doi:10.1115/IMECE2018-87063.

Magnetic levitation (maglev) concepts are applied to a variety of industries such as the automotive, aerospace, or energy in order to accomplish different tasks: suspension and propulsion in maglev trains, rocket propulsion and spacecraft attitude control, centrifuge of nuclear reactors. In this paper, maglev is implemented in environmentally friendly hydrokinetic energy harvesting to achieve contactless bearing, thus, minimizing friction and improving efficiency. Generally, maglev systems exhibit higher efficiency and reduced maintenance while providing longer lifetime and higher durability when appropriate engineering design and control are applied. A Flow Induced Oscillation (FIO) energy-harvesting converter is considered in this work. To minimize friction in the support of the cylinder in FIO (vortex induced vibrations and galloping) due to high hydrodynamic drag, a maglev system is proposed. In the proposed configuration, a ferromagnetic core (element 1), of known dimensions, is considered under the effects of an externally imposed magnetic field. A second ferromagnetic element, of smaller dimensions, is then placed adjacent to the previous considered core. This particular configuration results in a non-homogenous magnetic field for element 1, caused by dimensional disparity. Specifically, the magnetic flux does not follow a linear path from the ferromagnetic core to element 2. A general electromagnetic analysis is conducted to derive an analytical form for the magnetic field of element 1. Subsequent numerical simulation validates the obtained formula. This distinct expression for the magnetic field is valuable towards calculating the magnetic energy of this specific configuration, which is essential to the design of the FIO energy harvesting converter considered in this work.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A002. doi:10.1115/IMECE2018-87392.

To avoid discontinuation during long-term continuous operation in plants, a reliable monitoring system for the state diagnosis is strongly expected. However, occurring troubles of various facilities in a plant aren’t simple. We proposed a sophisticated estimation method to diagnose the state for reciprocating compressors. Our monitoring system uses both the measuring data in the factory and the analytical results based on the mathematical model, which can express the dynamic behavior about the reciprocating compressor. The mathematical model has multi degrees of freedom and the model parameters are identified to estimate the state change. To realize the reliable monitoring, we have to establish estimation and diagnosis method for any change of the operation state.

In this paper, we discuss estimation method of the rigidity in connecting and sliding portions by using the measuring data during operation of the reciprocating compressor in case of changing a connecting parts. We identified parameters of spring constant, by which one can be obtained the frequencies of eigenvalue analysis correspond to some natural frequencies determined based on an optimal problem. Moreover, we analyzed frequency responses of the model using the identified parameters and compared the frequency responses of the model with those of experimental results.

Topics: Compressors
Commentary by Dr. Valentin Fuster
2018;():V04BT06A003. doi:10.1115/IMECE2018-87416.

In previous study, the relation between dynamic behavior of the system and powder characteristic during rolling the roller on the fine coal spread over a table were investigated with the experimental equipment which consist of an elastic support roller system. In this study, we decreased rigidity of supporting part of experimental equipment to decrease natural frequency. These changes of structure enable us to specify a vibration during rolling the roller. We investigated rotating speed variation which is caused by roller slipping and horizontal vibration acceleration. In addition, we investigated relation between these experimental data and travel speed of the experimental equipment. As a result, both rotating speed variation and horizontal vibration acceleration increased with increasing of travel speed of the experimental equipment. After taking maximum value, both rotating speed variation and horizontal vibration acceleration decreased. To clear up the causes of the phenomenon, we investigated dependency of apparent friction coefficient upon slip ratio. However, noticeable dependency wasn’t represented. In addition, we calculated both horizontal vibration acceleration and RMS with frequency band limiting which is same range as natural frequency of the experimental equipment. As a result, it is found that natural frequency of the low level is excited as a main component and the excited frequency component changed to high level with increasing of travel speed of the experimental equipment.

Topics: Coal , Rollers
Commentary by Dr. Valentin Fuster
2018;():V04BT06A004. doi:10.1115/IMECE2018-87646.

Due to recent technological developments in advanced materials, the integration of shape memory alloys (SMAs) into new machines and mechanisms is becoming more common and it offers tremendous potential for the future. Using currently available properties of common SMA materials, the paper’s contribution is to: Study through dynamic simulation the potential offered by SMA springs to serve as the basis for rotary actuation. In the process, the SMA displaces a rocker arm rotating about an axis to induce rotational motion of a driveshaft, in effect converting a force into rotational motion. When embedded in a cycle with heating & cooling phases and a resetting mechanism, unidirectional rotational motion can be achieved.

Regarding heating and cooling cycles, forced air convection is used to reduce thermal cycle cooling and is calculated via transient thermal analyses. Using typical parameter values for the representative design considered, through forced air convection, cooling cycles are reduced from approximately 30 seconds (natural) to 5.5 seconds (forced) and as a result, a complete system cycle can occur in 10 seconds, with the applied inertial load of 2.0 kg-m2.

Using MATLAB and Simulink, a nonlinear 3rd order dynamic system model was created and simulations were performed. One complicating factor concerned angular limits and the necessary thermal cycling, which was solved through appropriate sequencing and resetting of integrators for different phases. Simulation results for the design considered show that a peak torque of 1.72 N-m is possible and that relatively smooth motion and approximately constant torque output is also possible through the addition of a few more rocker arm systems, properly commutated. Lastly, the design analysis framework and results may inspire future realization of actual devices.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A005. doi:10.1115/IMECE2018-88029.

In this work, a bow thruster is proposed to be used onboard small and medium-size watercraft, like motor yachts, fishing boats, patrol boats, ocean exploration vessels etc. with conventional or unconventional hull designs including displacement hull, planing hull, catamarans, SWATHs, SES, and so on. As oftentimes the case, a magnetic coupling is employed. Specifically, magnetic coupling is used to transfer torque from a brushless motor’s stator to its rotor through a magnetic field rather than a physical mechanical connection. Such magnetic coupling is very convenient for liquid pumps and as, in our case, propeller systems, since a static, physical barrier can be placed between the stationary and rotating part of the system to separate the fluid from the electrically supplied stator operating in air. Therefore, magnetic couplings preclude the use of shaft seals, which eventually wear out and fail from the sliding of two surfaces against each other. In this work, a system identification process of a rim driven bow thruster is implemented employing data series obtained by tests on a prototype scale model. System Identification leads to a black-box model of the system. The model derived can be extrapolated by grey-box modeling techniques for further design improvements. A control system for the proposed thruster is developed and validated through both computer and hardware-in-the-loop simulation, after its implementation onboard a broadly used industrial Programmable Logic Controller (PLC). The mathematical model of the bow thruster mechanism is developed and the performance is analysed by using Matlab/Simulink.

Topics: Engines , Motors , Propellers
Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Multibody Dynamic Systems and Applications

2018;():V04BT06A006. doi:10.1115/IMECE2018-86165.

Norwegian industries are constantly assessing new technologies and methods for more efficient and safer production in the aqua cultural, renewable energy, and oil and gas industries. These Norwegian offshore industries share a common challenge: to install new equipment and transport personnel in a safe and controllable way between ships, farms and platforms. This paper deploys the Moving Frame Method (MFM) to analyze the motion induced by a crane and controlled by a gyroscopic inertial device mounted on a ship. The crane is a simple two-link system that transfers produce and equipment to and from barges. An inertial flywheel — a gyroscope — is used to stabilize the barge during transfer. The MFM describes the dynamics of the system using modern mathematics. Lie group theory and Cartan’s moving frames are the foundation of this new approach to engineering dynamics. This, together with a restriction on the variation of the angular velocity used in Hamilton’s principle, enables an effective way of extracting the equations of motion. This project extends previous work. It accounts for the dual effect of both the crane and the stabilizing inertial device. Furthermore, this work allows for buoyancy and motor induced torques. Furthermore, this work displays the results in 3D on cell phones. The long-term results of this work leads to a robust 3D active compensation method for loading/unloading operations offshore. Finally, the interactivity between the crane and the stabilizing gyro anticipates the impending time of artificial intelligence when machines, equipped with on-board CPU’s and IP addresses, are empowered with learning modules to conduct their operations.

Topics: Cranes , Modeling , Ships
Commentary by Dr. Valentin Fuster
2018;():V04BT06A007. doi:10.1115/IMECE2018-86190.

A decline in oil-related revenues challenges Norway to focus on new types of offshore installations and their maintenance. Often, ship-mounted crane systems transfer cargo or crew onto marine structures such as floating windmills. This project analyzes the motion of a ship induced by an onboard crane in operation. It analyzes the motion of a crane mounted on a ship using The Moving Frame Method (MFM). The MFM draws upon Lie group theory and Cartan’s Moving Frames. This, together with a compact notation from geometrical physics, makes it possible to extract the equations of motion, expeditiously. This work extends a previous project that assumed many simplifications. It accounts for the masses and geometry of all components. This current approach also accounts interactive motor couples and prepares for buoyancy forces and added mass. The previous work used a symbolic manipulator, resulting in unwieldy equations. In this current phase, this research solves the equations numerically using a relatively simple numerical integration scheme. Then, the Cayley-Hamilton theorem and Rodriguez’s formula reconstructs the rotation matrix for the ship. Furthermore, this work displays the rotating ship in 3D, viewable on mobile devices. WebGL is a JavaScript API for rendering interactive 3D and 2D graphics within any compatible web browser without the use of plug-ins. This paper presents the results qualitatively as a 3D simulation. This research proves that the MFM is suitable for the analysis of “smart ships,” as the next step in this work.

Topics: Cranes , Modeling , Ships
Commentary by Dr. Valentin Fuster
2018;():V04BT06A008. doi:10.1115/IMECE2018-86323.

This paper presents a mathematical model for multi-axle steering vehicles operating on level ground. For transporting heavy loads vehicles with multiple axles are required. Apart from added complexity steering of multiple axle for turning is a big challenge. Due to type of load being carried a single unit vehicle is sometimes preferred. The mathematical model of a six axle vehicle with 4-axle steering system is developed. Simulations at various track radii, vehicle speeds and steering ratios (ratio between the first, second, fifth and sixth steering axle) are performed. Axle steering angles and wheel slip angles are evaluated. The steering ratio requirements vary with vehicle speed and turn radius. A configuration is selected for better performance for a wider range.

The resulting steering ratios show good vehicle maneuverability, stability and steering efficiency.

Topics: Vehicles
Commentary by Dr. Valentin Fuster
2018;():V04BT06A009. doi:10.1115/IMECE2018-86341.

This paper presents a new graphical technique to locate the secondary instantaneous centers of zero velocity (ICs) for one-degree-of-freedom (1-DOF) kinematically indeterminate planar mechanisms. The proposed approach is based on transforming the 1-DOF mechanism into a 2-DOF counterpart by converting any ground-pivoted ternary link into two ground-pivoted binary links. Fixing each of these two new binary links, one at a time, results in two different 1-DOF mechanisms where the intersection of the loci of their instantaneous centers will determine the location of the desired instantaneous center for the original 1-DOF mechanism. This single and consistent approach proved to be successful in locating the ICs of various mechanisms reported in the literature that required different techniques to reach the same results obtained herein.

Topics: Linkages
Commentary by Dr. Valentin Fuster
2018;():V04BT06A010. doi:10.1115/IMECE2018-87016.

This paper compares the dynamic response of a 3-degree-of-freedom (3-DOFs) parallel manipulator with multiple dry clearance joints and with lubricated joints. For this purpose, a methodology developed on Newton–Euler equations is proposed to study lubricated joints in the parallel manipulator, which involves the hydrodynamic forces and impact forces in the constrained equations. Specifically, the hydrodynamic forces are based on the Reynolds’ equation of an infinitely long lubricated joint. Dynamic simulations are presented through the dynamic parameters of a planar parallel manipulator (3-PRR, the underline of the P represents the actuated joint, P and R represents prismatic and revolute pairs respectively), which has six revolute clearance joints and three ideal prismatic joints. The results of the comparison show that the lubricant makes significant difference and greatly improves the dynamic performance of the parallel manipulator with multiple revolute joints. More periodic states are observed from the dynamic behavior of the parallel manipulator with lubricated joints, making the manipulator easier to drive. All results demonstrate the usage of the procedures which contain the hydrodynamic force model of multiple lubricated joints in non-linear DAEs of a 3-DOFs parallel manipulator.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A011. doi:10.1115/IMECE2018-87126.

For rigid-body systems subjected to non-holonomic constraints, a streamlined method is presented to derive a minimum number of analytical equations of motion. To illustrate the method, a rolling disk problem is considered.

In kinematics, an orthonormal coordinate system is attached to the center of mass together with additional coordinate systems introduced to define the connection path. For each coordinate system, a moving frame is defined by explicitly writing the coordinate vector basis and the position vector of the origin, whereby the attitude of the coordinate vector basis and the coordinates of the origin are compactly stored in a 4 × 4 frame connection matrix of the special Euclidean group, SE(3).

Contact velocity constraints are transformed to pfaffians to obtain the associated variational constraints.

In kinetics, the principle of virtual work is employed. The desired equations of motion are obtained by expressing the translational and angular velocities at the center of mass as the linear functions of the generalized velocities with the coefficients stored in [B]-matrix, and reducing it to [B*]-matrix after incorporating the contact constraints.

The method can be easily extended to multi-body systems with both holonomic and non-holonomic constraints.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A012. doi:10.1115/IMECE2018-87253.

Analytical equations of motion are critical for real-time control of translating manipulators, which require precise positioning of various tools for their mission. Specifically, when manipulators mounted on moving robots or vehicles perform precise positioning of their tools, it becomes economical to develop a Stewart platform, whose sole task is stabilizing the orientation and crude position of its top table, onto which various precision tools are attached.

In this paper, analytical equations of motion are developed for a Stewart platform whose motion of the base plate is prescribed. To describe the kinematics of the platform, the moving frame method, presented by one of authors [1,2], is employed. In the method the coordinates of the origin of a body attached coordinate system and vector basis are expressed by using 4 × 4 frame connection matrices, which form the special Euclidean group, SE(3). The use of SE(3) allows accurate description of kinematics of each rigid body using (relative) joint coordinates. In kinetics, the principle of virtual work is employed, in which system virtual displacements are expressed through B-matrix by essential virtual displacements, reflecting the connection of the rigid body system [2]. The resulting equations for fixed base plate reduce to those for the top plate, obtained by the Newton-Euler method.

A main result of the paper is the analytical equations of motion in matrix form for dynamics analyses of a Stewart platform whose base plate moves. The control applications of those equations will be deferred to subsequent publications.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A013. doi:10.1115/IMECE2018-87458.

There are many models of impact used to predict the post-impact conditions of a system and all of them are based on Hertz’s theory, dated from the nineteenth century, where the repulsive force is proportional to the deformation of the bodies under contact and may also be proportional to the rate of deformation. The objective of this work is to analyze the behavior of the bodies during impact using some contact models and compare the results to a Finite Element Method model. The main parameters which will be evaluated are the body velocities, the contact force and the deformation of the bodies. An advantage of using the Finite Element Method is the possibility to apply plastic deformation to the model according to material definition. In the present study, it will be used Johnson–Cook plasticity model where the parameters are obtained based on empirical tests of real materials. Thus, it is possible to compare the behavior of elastic and plastic numerical models with the finite element model and to verify how these models reproduce the impact between solid bodies.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A014. doi:10.1115/IMECE2018-87545.

This work presents a new systematic solution to identify the vehicle inertia parameters which are essential inputs for vehicle simulation and vehicle safety research. In conceptual design phase of this work, a virtual three Degree-of-Freedom (DoF) test bench/ parallel manipulator (PM) whose moving platform is used to clamp vehicle under test is developed. In order to realize the kinematic characteristics of the proposed PM, the kinematic analysis consists of inverse kinematic and singularity architecture is carried out. Aiming at obtaining all ten vehicle inertia parameters (i.e., mass, center of gravity and inertia tensor), the observation matrix for parameter identification is derived from the dynamic model of PM. To get the dynamic model, the Euler’s equation and Lagrange approach are applied to implement the dynamic analysis for PM’s moving platform and actuators, respectively. It is beneficial to reduce the complexity of dynamic model and load of numerical computation. In the following section, to minimize the sensitivity of parameter identification to measurement noise, an optimization process of searching for the optimal movement trajectory of PM is proposed. For this purpose, the parameterized finite-Fourier-series are used to definite the general movement trajectory of PM firstly. Subsequently, the parameters of general trajectory are optimized by employing a nonlinear iterative algorithm. Objective of this algorithm is to obtain the minimal condition number of observation matrix and meanwhile to ensure the PM still works in the achievable working space during the test. The results show that the vehicle inertial parameters can be effectively identified by executing the single optimal movement trajectory on the PM. It is expected that the proposed systematic solution could be an important approach to improve the identification efficiency and identification accuracy of vehicle inertial parameters.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A015. doi:10.1115/IMECE2018-87858.

During the past few decades, significant interest in applying linear and nonlinear dynamical vibration absorbers for energy transfer and dissipation has significantly arisen. The existing studies of employing dynamical absorbers with small and large-scale dynamical structures have been mostly focusing on suppressing the oscillations for structures that move in one direction only. However, most of these structures are vulnerable to different sources and types of excitations that could induce two-dimensional oscillations into these structures. Consequently, this paper presents an application of a vibration absorber to suppress the two-dimensional vibration induced into the structure caused by a two-dimensional impulsive loading. The system description and the governing equations are firstly introduced and then followed by an optimization process to maximize vibration suppression. The response of the system under various combinations of longitudinal and lateral impulsive loadings is presented and the capability of the proposed absorber to suppress the induced vibration is evaluated.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A016. doi:10.1115/IMECE2018-87862.

Meeting the stringent requirements on fuel economy and emissions is still a challenge for automotive original equipment manufacturers (OEMs). In this study, we consider the light weighting opportunities of a heavy commercial truck by evaluating the various requirements of its anti-roll bar. First, an MSC.ADAMS model of the truck is analyzed under some standard vehicle dynamics maneuvers and a target for the anti-roll bar is set. A topology optimization study is then performed using Solid Isotropic Material with Penalization (SIMP) method to determine its dimensions and material to meet this target. For this purpose, a finite element (FE) model of the anti-roll bar is developed in order to determine its torsional stiffness using MSC.Nastran commercial software. The advantages and disadvantages of various optimization results are discussed. Finally, fatigue performance of the anti-roll bar is assessed under the road load data coming from various road simulations. The results prove that the simulation tools and optimization methods offer great capabilities to meet challenging requirements of automotive industry.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A017. doi:10.1115/IMECE2018-88053.

There are different types of uncertainty sources in the Complex System Thermal-Hydraulics Codes calculations resulting in inaccurate computations. The sources include boundary and initial condition, model structure, their corresponding parameters, user inputs, the numerical techniques and the errors in the validation test data. Regarding the codes structure, the uncertainty sources are utilization of simplified mathematical models expressing conservation laws, thermodynamics laws, state equations applicability, discretization of governing equations, and physical characteristics of the simulated system. The Edwards high-pressure test tube is a well-known test for verifying the results of simulating complex numerical codes. On the other hand, the existence of deterministic values in the initial, boundary conditions and geometric dimensions can challenge the results of this experiment.

In this study, a probabilistic approach is utilized to study the behavior of the Edwards High-Pressure pipe using RELAP5 Complex System Thermal-Hydraulics Code. A probabilistic distribution is estimated with appropriate accuracy for the experiment uncertainties.

An efficient approach consisting of Wilks sampling method is implemented to quantify the uncertainty of experimental results.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A018. doi:10.1115/IMECE2018-88485.

Whole-body vibrations (WBV) have been used for enhancing muscle strength and bone density of human bodies, training athletes and dancers, and helping people with disabling conditions and rehabilitations. On the other hand, WBV-induced occupational diseases have been reported. Researchers in automotive, farm equipment, and heavy machinery have put forward a few models for studying harmful vibrations on human bodies.

This paper will review the effects of frequencies and magnitudes of WBV on a human body. Discussion of effects of frequencies and magnitudes on a human body will provide a preliminary boundary line between good and bad whole-body vibrations. Two multibody dynamics models and associated application cases will be proposed to show how the models may be used to represent whole-body vibrations under both good and bad vibrations. Three basic vibration elements associated with whole-body vibrations of the human body are handled as follows: (1) ligaments are modeled as spring elements; (2) muscles and tendons are modeled as damping elements; (3) bones are modeled as rigid bodies with masses/inertias and connected by idealized massless joints. In such a biomechanical vibration system, the spring elements (ligaments) help hold the human body skeleton structure in a stable condition, pass spring forces and potential energy to rigid bodies (bones) for bone vibrational motions. The damping elements (muscles and tendons) play roles of a damper and absorb energy input from the whole-body vibration resource.

Based on the proposed multibody dynamics models, Kane’s method is then used to develop equations of motion. The equations will be further used for development of simulation algorithms to understand frequencies and magnitudes of both good and bad whole-body vibrations.

The models may be utilized to understand why frequencies and magnitudes of whole-body vibrations will provide benefits to human health under one situation but cause occupational diseases under another scenario.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Nonlinear Dynamics, Control, and Stochastic Mechanics

2018;():V04BT06A019. doi:10.1115/IMECE2018-86299.

This paper presents an optimal design for a system comprising multiple nonlinear energy sinks (NESs) and piezoelectric-based vibration energy harvesters attached to a free–free beam under shock excitation. The energy harvesters are used for scavenging vibration energy dissipated by the NESs. Grounded and ungrounded configurations are examined, and the systems parameters are optimized globally to maximize the dissipated energy by the NESs. The performance of the system was optimized using a dynamic optimization approach. Compared to the system with only one NES, using multiple NESs resulted in a more effective realization of nonlinear energy pumping particularly in the ungrounded configuration. Having multiple piezoelectic elements also increased the harvested energy in the grounded configuration relative to the system with only one piezoelectric element.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A020. doi:10.1115/IMECE2018-86530.

Current methods of unmanned underwater locomotion do not meet stealth, robustness and efficiency. This work discuses about designing a Bioinspired UUV or Unmanned Underwater Vehicle that uses an undulating fin approximating to that of a cuttlefish fin locomotion. This propulsion method has higher maneuverability and ability to navigate while leaving its surroundings relatively undisturbed as compared to other propeller based systems. Mathematical models and control algorithms describing the complicated locomotion have been developed, and a simulation model is used to verify the theoretical results. This design of UUV can be utilized for underwater data collection and military applications without hampering the underwater wildlife.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A021. doi:10.1115/IMECE2018-87474.

A method is applied here to extract the amplitude-dependent modal damping coefficients and frequencies of nonlinearly coupled oscillators with a nonlinear force in which a negative linear stiffness is incorporated. The proposed method can be directly applied into the equations of motion of the original system where the solution is not required to be obtained a priori. The exact nonlinear frequency content in the nonlinear coupling element is employed to obtain an equivalent amplitude-dependent stiffness element using a scaling parameter that preserves the exact frequency content in the original nonlinear element. Therefore, at each amplitude in the nonlinear coupling force, the modal damping coefficients and frequencies are calculated from the eigensolution of the instantaneous amplitude-dependent equivalent system. It is found that the modal damping content is strongly affected by the nonlinear frequency content where the modal damping coefficients become amplitude-dependent quantities. The obtained amplitude-dependent damping coefficients are plotted with respect to the potential energy of the nonlinear coupling force. The method is also applicable with larger degree-of-freedom nonlinear dynamical systems in which negative and non-negative linear stiffness components are incorporated in the nonlinear coupling forces. The amplitude-dependent modal damping matrices of the amplitude-dependent equivalent systems are found to be satisfying all matrix similarity conditions with the linear modal damping matrix of the original system.

Topics: Damping , Stiffness
Commentary by Dr. Valentin Fuster
2018;():V04BT06A022. doi:10.1115/IMECE2018-87586.

This paper studies and simulates the dynamics and controls for a two-wheeled robotic chassis that successfully and consistently self-balances. Previous approaches to similar models have derived their dynamics from first principles using Newtonian mechanics for a linearized, shared-axle system and Lagrangian mechanics for a linearized, independently-actuated system. As such, the derived dynamics do not often reflect important factors of real world models which are not linear. However, this study specifically focuses on a more complicated system with independently-actuated wheels, for which a sophisticated and realistic dynamic model is derived using non-linearized Lagrangian mechanics. The pendulum and cart movements are each assumed to be planar, and their planes of motion are defined perpendicular to each other. The system’s performance is then analyzed in the simulation environment to determine the effect of various controllers and filters in cases of full and partial state feedback with and without sensor noise. Performance is characterized in terms of pendulum angle relative to the vertical axis and cart trajectory relative to the ground plane, both of which are functions of the voltage-applied force on each wheel independently. A comparison of the results shows that the non-linearized Lagrangian model best fits the true data and yields less uncertainty given a sensor failure. Therefore, the presented study has high intellectual merits compared to existing studies which focus on only linearized models. Based on the deterministic parameters of this study’s non-linearized model, a recommendation is made about which combination of controllers and filters best maintains the system’s stability in the event of a sensor failure returning only partial state feedback.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A023. doi:10.1115/IMECE2018-87766.

The superharmonic resonance of second order of microelectro-mechanical system (MEMS) circular plate resonator under electrostatic actuation is investigated. The MEMS resonator consists of a clamped circular plate suspended over a parallel ground plate under an applied Alternating Current (AC) voltage. The AC voltage is characterized as hard excitation, i.e. the magnitude is large enough, and the operating frequency is near one-fourth of the natural frequency of the resonator. Reduced Order Model (ROM), based on the Galerkin procedure, transforms the partial differential equation of motion into a system of ordinary differential equations in time using mode shapes of vibration of the circular plate resonator. Three numerical methods are used to predict the voltage-amplitude response of the MEMS plate resonator. First, the Method of Multiple Scales (MMS) is directly applied to the partial differential equation of motion which is this way transformed into zero-order and first-order problems. Second, ROM using two modes of vibration is numerical integrated using MATLAB to predict time responses, and third, the AUTO 07P software for continuation and bifurcation to predict the voltage-amplitude response. The nonlinear behavior (i.e. bifurcation and pull-in instability) of the system is attributed to the inclusion of viscous air damping and electrostatic force in the model. The influences of various parameters (i.e. detuning frequency and damping) are also investigated in this work.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A024. doi:10.1115/IMECE2018-88320.

Industrial hydraulic systems are complex, and show nonlinear dynamic behavior because of their nature. When it is not easy to deal with the nonlinear models, hydraulic systems are usually described by linear or linearized models around operating points. In this work a nonlinear dynamic and mathematic model for the position control of a double rod hydraulic actuator was developed.

Three control strategies were implemented: PID control, optimal control (LQR) and control by Feedback Linearization. For the PID control and optimal control (LQR) strategies a linearized model of the hydraulic actuator was developed around a specific operating point, contrary to the Feedback Linearization control that have a wide operation range and the nonlinear model was used.

These mathematical models were represented on Simulink environment, in order to compare and analyze the response and dynamic behavior. The optimal control (LQR) shows better settling time than the PID control, both without overshoot; and the Feedback Linearization show the best dynamic performance in terms of settling time with a little overshoot and disturbance tolerance.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Novel Control of Dynamic System

2018;():V04BT06A025. doi:10.1115/IMECE2018-86758.

The stabilization of the inverted pendulum-cart system (IPCS) is a classical problem in the control engineering. The study of IPCS is motivated by its applications to the balancing of rocket boosters and bipedal robots. IPCS represents a class of nonlinear, under-actuated, and unstable system hard to be controlled in real-time. In this paper, a novel nonlinear time-frequency control (NTFC) strategy is applied to stabilize an inverted pendulum mounted on a cart. The proposed controller design is adaptive and employs discrete the wavelet transform and filtered-x least-mean-square (Fx-LMS) algorithm to realize the control in real-time. Using the wavelet transform, the adaptive controller is demonstrated to inhibit the deteriorations of the time and frequency responses simultaneously before the residual oscillation is too broadband to be controlled. The presented controller consists of two adaptive finite impulse response filers that operate on the wavelet coefficients: the first one realizes the online identification and provides a priori information in real-time while the second one realizes a feedforward control and rejects the uncontrollable input signal based on the first FIR filter. The equation of motion is derived based on the Newton’s Second law of motion and the model id simulated in MATLAB for verification. A number of commonly used control methods for the stabilization of the IPCS are investigated and evaluated against the proposed NTFC strategy. The simulation results show that the proposed control strategy is feasible for balancing the IPCS for a large, tilted initial angle within a short time interval and strongly robust to external impact and perturbation in real-time.

Topics: Pendulums
Commentary by Dr. Valentin Fuster
2018;():V04BT06A026. doi:10.1115/IMECE2018-86824.

In this paper, periodic motions in a first-order, time-delayed, nonlinear system are investigated. For time-delay terms of non-polynomial functions, the traditional analytical methods have difficulty in determining periodic motions. The semi-analytical method is used for prediction of periodic motion. This method is based on implicit mappings obtained from discretization of the original differential equation. From the periodic nodes, the corresponding approximate analytical expression can be obtained through discrete finite Fourier series. The stability and the bifurcations of such periodic motions are determined by eigenvalue analysis. The bifurcation tree of period-1 to period-4 motions are obtained and the numerical results and analytical predictions are compared. The complexity of periodic motions in such a simple dynamical system is discussed.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A027. doi:10.1115/IMECE2018-86833.

In this paper, the experimental dynamics of a Duffing oscillatory system are studied for periodic motions. A Duffing oscillatory circuit is developed for the experimental study of periodic motions on the bifurcation trees. The coexisting asymmetric periodic motions are obtained experimentally. The analytical periodic motions in the Duffing oscillator are presented for comparison with experimental results. Because of hardware and data leakage of experimental instruments, the experimental result accuracy is much lower than the analytical results of periodic motions. To improve the experimental results accuracy, the high quality hardware and instruments should be adopted and the high resolution data acquisition systems should be adopted.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A028. doi:10.1115/IMECE2018-86842.

This paper develops semi-analytical solutions of periodic motions of the van der Pol oscillator. The van der Pol system is discretized to form implicit mappings. Based on specific mapping structures, the semi-analytical solutions are obtained accurately, and the independent bifurcation branches of periodic motions are also presented for a better understanding of the nonlinear characteristics of the van der Pol oscillator. Stability and bifurcations are carried out though eigenvalue analysis. For comparison of analytical and numerical solutions, numerical simulation is completed and displacement and trajectories are presented.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A029. doi:10.1115/IMECE2018-86849.

In this paper, period motions in a periodically forced, damped, double pendulum are analytically predicted through a discrete implicit mapping method. The implicit mapping is established via the discretized differential equation. The corresponding stability and bifurcation conditions of the period motions are predicted through eigenvalue analysis. Numerical simulation of the period motions in the double pendulum is completed from analytical predictions.

Topics: Pendulums
Commentary by Dr. Valentin Fuster
2018;():V04BT06A030. doi:10.1115/IMECE2018-86862.

In this paper, period-1 motions varying with excitation frequency in a periodically forced, nonlinear spring pendulum system are predicted by a semi-analytic method. The harmonic frequency-amplitude for periodical motions are analyzed from the finite discrete Fourier series. The stability of the periodical solutions are shown on the bifurcation trees as well. From the analytical prediction, numerical illustrations of periodic motions are given, the comparison of numerical solution and analytical solution are given.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A031. doi:10.1115/IMECE2018-88051.

Real-world networks are dynamical complex network systems. The dynamics of a network system is a coupling of the local dynamics with the global dynamics. The local dynamics is the time-varying behaviors of ensembles at the local level. The global dynamics is the collective behavior of the ensembles following specific laws at the global level. These laws include basic physical principles and constraints. Complex networks have inherent resilience that offsets disturbance and maintains the state of the system. However, when disturbance is potent enough, network dynamics can be perturbed to a level that ensembles no longer follow the constraint conditions. As a result, the collective behavior of a complex network diminishes and the network collapses. The characteristic of a complex network is the response of the system which is time-dependent. Therefore, complex networks need to account for time-dependency and obey physical laws and constraints. Statistical mechanics is viable for the study of multi-body dynamic systems having uncertain states such as complex network systems. Statistical entropy can be used to define the distribution of the states of ensembles. The difference between the states of ensembles define the interaction between them. This interaction is known as the collective behavior. In other words statistical entropy defines the dynamics of a complex network. Variation of entropy corresponds to the variation of network dynamics and vice versa. Therefore, entropy can serve as an indicator of network dynamics. A stable network is characterized by a specific entropy while a network on the verge of collapse is characterized by another. As the collective behavior of a complex network can be described by entropy, the correlation between the statistical entropy and network dynamics is investigated.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A032. doi:10.1115/IMECE2018-88101.

Literature review shows that much effort has been given to model physical systems involving a large number of interacting constituents. As a network evolves its constituents (or nodes) and associated links would either increase or decrease or both. It is a challenge to extract the specifics that underlie the evolution of a network or indicate the addition and/or removal of links in time. Similarity-based algorithm, Maximum likelihood methods, and Probabilistic models are 3 mainstream methods for link prediction. Methods incorporating topological feature and node attribute are shown to be more effective than most strategies for link prediction. However, to improve prediction accuracy, an effective prediction strategy of practicality is still being sought that captures the characteristics fundamental to a complex system. Many link prediction algorithms have been developed that handle large networks of complexity. These algorithms usually assume that a network is static. They are also computationally inefficient. All these limitations inevitably lead to poor predictions. This paper addresses the link prediction problem by incorporating microscopic dynamics into the matrix factorization method to extract specific information from a time-evolving network with improved link prediction. Numerical experiments in applying static methods to temporal networks show that existing link prediction algorithms all demonstrate unsatisfactory performances in link prediction, thus suggesting that a new prediction algorithm viable for time-evolving networks is required.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A033. doi:10.1115/IMECE2018-88326.

In the multi-axis high-speed and high-precision machining process, the contouring error and the feed rate of tool tip and affect the quality of machined workpiece and the processing efficiency, respectively. The faster feed motion will result in greater tracking error of each axis. The contouring error which directly affects the quality of machined part is caused by the tracking errors of the axes. Obviously, it is difficult to improve the contouring accuracy and increase the feed rate simultaneously. To this end, a novel optimization model is developed here based on the model predictive control method. First, the feed servo model of translational and rotary axes are established, and the contouring error model is afterwards constructed. Subsequently, the optimization algorithm is derived to achieve the high processing speed, and input constraints are addressed to avoid violation of the performance limitation of the drivers. In addition, contouring error constraint, which is obtained by calculating the contouring error of the processed path, is addressed to high contour accuracy. Finally, a simulation is conducted to verify the effectiveness and superiority of the proposed method.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A034. doi:10.1115/IMECE2018-88435.

Piston pumps use a mechanism to create a reciprocating motion along an axis which then builds pressure in the barrel to force fluid through the pump. In general, pressure in the chamber is controlled by a heavy linear actuator to manipulate the valves at both suction and discharge points. While hydraulic actuators are strong enough to handle heavy payloads, they are not much suitable to drive arm manipulators mounted on mobile robots due to their heavy weight. To simplify the control logic more suitable for mobile robotics applications and to reduce the overall weight, we have used a smaller pump and utilized two simple trigger valves to control the stroke displacement of the extender. Since valves can only be in on and off states, a pulse width modulation (PWM) with duty cycle control is adopted. End manipulator position and velocity actuation are driven by a PI controller and maximum displacement accuracy, minimal rise time with minimum overshoot cases are studied. Experimental setup of the fluid valve control logic is explained. Both open and closed loop cases are discussed. It is shown that duty cycle control of valves can reach to a reasonable accuracy compared to the traditional linear control system with a lower weight and a simpler control logic.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Posters

2018;():V04BT06A035. doi:10.1115/IMECE2018-86008.

A simplified roll-plane model is proposed to assess the effect of the vertical position of the center of gravity of the body-cargo system, on the rail fatigue life. A set of assumptions are made to simplify the analysis, including neglecting the bogie’s dynamic contribution to the wheel-rail forces. Three performance measures are defined to assess the effect of different dedicated railway cars on the rail fatigue life, including the fourth-power law, the load dispersion, and the rail fatigue. The simulation results suggest that the vertical position of the center of gravity of the body-cargo set, severely affects the fatigue life of the railway material, with the two-stack car being the most aggressive. For example, twice as aggressive as the gondola car.

Topics: Rails , Damage
Commentary by Dr. Valentin Fuster
2018;():V04BT06A036. doi:10.1115/IMECE2018-86840.

Although 3D printing has become a widespread method of fabrication, the vibratory properties of thermoplastic composites are poorly understood. This is, in part, due to the anisotropies introduced by the 3D printing process, the composite materials used, and the geometry. In this study, an attempt has been made to characterize the vibratory response of a 3D printed thermoplastic cantilever, in order to determine the damping ratio and natural frequency. The cantilevered beams were 3D printed, with a range of varied parameters. These parameters include the inclusion and exclusion of continuous carbon fiber reinforcement, as well as the three orthogonal build directions. Impact tests and frequency sweeps were used to gain information about the vibratory response of these cantilevers. This information was used to model the effects of the carbon fiber and anisotropy introduced by the different build parameters. During the experiments, a high-speed camera was used to record the response of the cantilevers. These videos were then post-processed with image analysis tools to quantify the response. Then, a point near the tip of the cantilever was used as the time-dependent variable for a reduced order model. By proceeding in this described method, the damping ratio and natural frequency of the system may be written as a function of the build parameters.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Renewable Energy, Structural Health Monitoring, and Distributed Structural Systems

2018;():V04BT06A037. doi:10.1115/IMECE2018-87493.

This paper presents the effectiveness of using mixed, nodal and/or modal coordinates in modeling wind turbines. The paper shows that the nodal model exhibits excellent numerical properties, especially in the case of highly rotations. In the case where the rotation of the rotor-blade is extremely high, the geometric stiffness effect must be taken into account, and therefore, the nonlinear stiffness terms should be included within the model. On the other side, the dynamics of the tower as well as other components can be modeled using a set of modal coordinates. The paper shows a method of utilizing experimental modal coordinates for low speed components and those that deflected by simple motion shapes. The wind-turbine model based on the floating frame of reference formulation and by using the suggested mixed coordinates can be utilized for design process, identification and health monitoring aspects.

Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Smart Structures and Structronic Systems: Sensing, Energy Generation, and Control

2018;():V04BT06A038. doi:10.1115/IMECE2018-86157.

The work presented here investigates a unique design platform for multi-stable energy harvesting using only interaction between magnets. A solid cylindrical magnet is levitated between two stationary magnets. Peripheral magnets are positioned around the casing of the energy harvester to create multiple stable positions. Upon external vibration, kinetic energy is converted into electric energy that is extracted using a coil wrapped around the casing of the harvester. A prototype of the multi-stable energy harvester is fabricated. Monostable and bistable configurations are demonstrated and fully characterized in static and dynamic modes. Compared to traditional multi-stable designs the harvester introduced in this work is compact, occupies less volume, and does not require complex circuitry normally needed for multi-stable harvesters involving piezoelectric elements. At 2.5g [m/s2], results from experiment show that the bistable harvester does not outperform the monostable harvester. At this level of acceleration, the bistable harvester exhibits intrawell motion away from jump frequency. Chaotic motion is observed in the bistable harvester when excited close to jump frequency. Interwell motion that yields high displacement amplitudes and velocities is absent at this acceleration.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A039. doi:10.1115/IMECE2018-86390.

A gyroscopic power generator that generates 1.8 W by using a rotor of 100 mm diameter spinning at 500 rpm is developed. In conventional vibrational generators, which use simple vibrations of a inner pendulum, the output power has been less than 10 mW. Gyroscopic generators increase the inertial force by rotating the pendulum at high speed and generate about 100 times greater power than the conventional ones. However, gyro generators have not been able to operate under arbitrary vibrations at wearable sizes because they are unstable and easily stall by disturbances, and the gyro torque and the electromechanical transformation efficiency rapidly decrease by miniaturization. In this paper, first, a theoretical model is developed to clarify the basic characteristics of the generator. Next, a desktop-sized generator that works under any vibration is developed using highly precise motors and gears determined by the theory. Next, mechanical and electrical characteristics are measured to show the validity of the theory. Finally, the performance of wearable-sized generators is predicted to show the generators that have the same device size and rotor spinning speed as those of 2.5” and 3.5” HDD’s generate 0.74 W and 1.84 W, respectively.

Topics: Motors , Generators
Commentary by Dr. Valentin Fuster
2018;():V04BT06A040. doi:10.1115/IMECE2018-86444.

A motor-driven gyroscopic generator was developed that self-accelerates by power feedback. In a previous report, power generation of 1.8 W was confirmed, but an external power source was used to drive the spin motor. In this research, a method is presented to apply the power generated from the precession movement to the spin motor. It enables not only eliminating the power source but also accelerates the spin velocity. To achieve acceleration, however, the feedback circuit must boost the generated voltage since the counter voltage of the spin motor also increases with its velocity. Also, there is an optimum boosting rate that depends on the spin velocity. In this paper, first, a circuit equivalent to the gyro-generator system is presented and the coil resistance of the generator is shown to limit the highest boosting rate. Next, the rotor accelerating characteristics of four boosting circuits are compared. Electrical boosting is shown to have the same effect as mechanical impedance control. A numerical simulation is conducted and the power acceleration by boosting is also verified. Finally, a prototype generator is developed. The validity of theoretical results is verified and an output power of 0.1 W is obtained.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A041. doi:10.1115/IMECE2018-86860.

The use of robots in search and rescue operations has increased dramatically over the years. A robot is able to detect survivors of a dangerous situation, like an earthquake, without putting the operator’s life in danger as well. There are many types of robots being developed for search and rescue purposes, but a smaller and more durable robot will be beneficial for designs in the future.

The purpose of our project is to research and design a soft body robot that is capable of locating individuals in search and rescue operations. The robot has a design similar to a car which will allow the control of the robot to be easy to use. It has been designed with a self-righting mechanism in case the vehicle flips over or gets stuck. The robot has a small size so that it can fit through small holes that a person could not enter. The robot will be capable of traversing over uneven terrain, including small ledges through an actuator. The actuator will be designed to cause the robot to spring over or on a ledge. According to simulations from SolidWorks, the wheels of the robot can also withstand a drop from 2 meters. The design and material of the wheels will be further tested and changed to increase the performance of the wheel. Once a design has been chosen, the body of the robot will be designed. Current designs of ground rescue robots will be studied in order to attain a better understanding on what designs work best. The hope is to make the robot more durable than previous designs using a soft material as the outer shell of the robot. A soft material should allow the robot to be able to absorb impacts from falling debris or unexpected falls.

Once the design of the robot has been optimized, a prototype will be created. The next step will be to code the robot so that it can be controlled with a remote. The current proposal is to use an Arduino board to send and receive signals from that remote. Then a camera will be attached to the robot which will allow the operator to see where the robot is and where the survivors are located.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A042. doi:10.1115/IMECE2018-88599.

For the laminated piezoelectric rectangular plate with large deflection and large rotation, the nonlinear equilibrium differential equations are derived and solved. Firstly, the global Cartesian coordinate system to describe the undeformed geometry and the local orthogonal curvilinear coordinate system to describe the deformed geometry are established respectively on the mid-plane of the plate before and after the deformation, and the relationship between the two coordinates is expressed by transformation matrix. For the convenience of calculation, the expressions of the nonlinear curvatures and inplane strains are obtained by Taylor series expansion. Considering the piezoelectric effect, three equilibrium partial differential equations describing nonlinear bending problems are obtained by the principle of virtual work. Furthermore, in order to simplify the solution process, the stress function is introduced to automatically satisfy the first two equations for the large deformation of the cantilever plate, and the relationship between stress function, the mid-plane internal force and shear force is also given for the first time. Therefore, the stress function and the transversal displacement are the main unknowns of the governing equation and compatibility equation. Additionally, the approximate deflection function and stress function are given which can satisfy all the displacement boundary conditions and only part of the force boundary conditions. Thereby, the generalized Galerkin method is used to obtain the approximate solution of the nonlinear bending problem. Finally, the results in the study are verified by comparison with the results obtained from the finite element method. It also provides a theoretical basis for the engineering application of the large deformation of the piezoelectric cantilever plate.

Topics: Deformation
Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Vibration, Noise Control, and Damping Technologies

2018;():V04BT06A043. doi:10.1115/IMECE2018-86089.

This paper presents results from a follow-up study of fractional damping and time delay. Fractional damping has been used in the literature to demonstrate certain advantages over integer-order damping in many applications involving viscoelastic characteristics. It is observed that fractional damping can be used to influence stability boundaries, natural frequencies and vibration amplitudes, thus providing modeling flexibility in predicting the response of an isolated system during preliminary design. Additionally, time delay or lag is known to be inherent in a damped system, therefore a direct representation of time delay in modeling the damping force is expected to enhance model fidelity. This paper investigates the use of Voigt and Maxwell-Voigt models that incorporate fractional damping and time delay. In this paper, fractional damping has been particularly introduced to investigate possible improvements in the frequency response. Results indicate that fractional damping can be used to significantly enhance the capability of the Voigt model. The influence of the fractional order is found to be analogous to the damping ratio in an integer-order model. Fractional order is seen to exhibit a somewhat limited influence on the Maxwell-Voigt model. However, attributes such as the peak frequency and maximum amplitude are seen to be directly influenced by the fractional order. Although time delay is seen to exhibit an influence on the frequency response, it needs to be limited within useful bounds. Overall, it is observed that fractional order and time delay can be used to improve the accuracy of the Voigt and Maxwell-Voigt models. These enhanced models can be used for the design and development of elastomeric isolators and vibration isolation systems.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A044. doi:10.1115/IMECE2018-86136.

A free-fall absolute gravimeter uses a Mach-Zehnder interferometer to track the free-falling object. Theoretically, it needs an inertial reference point, which is a reference retroreflector keeping static in inertial frame for an accurate absolute gravimetry. Practically, the reference retroreflector is always disturbed by the ground vibration. Traditionally, a vibration correction method with a broadband seismometer is used to reduce the effect of the ground vibration. The transfer function between the reference retroreflector and the seismometer is hypothesized as a proportional element with time delay. The difference between the hypothesized and the real transfer function limits the effect of the vibration correction. On this basis, a modified method, replacing the sensitive element of a seismometer with the reference retroreflector, is proposed. The motion of the reference retroreflector is measured directly by differential parallel plate capacitance detection. A closed-loop control circuit produces feedback voltage to make the reference retroreflector track the ground vibration. The feedback voltage represents the reference retroreflector’s motion directly. Experiments show the capacitance detecting circuit detects the displacement of the reference retroreflector relative to the ground with a resolution of 0.6 nm at 500 Hz. The acceleration resolution of the homemade vertical seismometer is about 10 mGal. The sensitivity of the seismometer is 316 V/g. The damp ratio of the homemade seismometer is little, and the natural frequency of the homemade seismometer is 104 Hz by analyzing the step response of the system. The bandwidth of the system is around 175 Hz. In the future, the homemade seismometer will be applied in absolute gravimeters for hostile measurement.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A045. doi:10.1115/IMECE2018-86143.

This paper presents an energy-regenerative suspension device that is able to harvest some of the wasted energy that is generated in a suspension system. For a traditional road vehicle suspension system, shock absorbers are mainly dissipating energy to reduce vibration. The dissipated energy may be collected to improve the fuel economy of road vehicles. In this research, CarSim and Simulink are used to simulate and determine the harvestable energy in a conventional shock absorber under different operating conditions. A conceptual energy-regenerative absorber is designed and tested using a fabricated prototype. A variable speed motor is implemented to adapt the change of stroke length of a mechanism due to the various road roughness. Instruments, e.g., laser tachometer, pressure gauge, ammeter, voltmeter, and stopwatch, are used to collect data. The simulation and prototype testing results indicate that the proposed energy-regenerative suspension device could harvest dissipated energy to improve vehicle fuel economy.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A046. doi:10.1115/IMECE2018-86220.

In this paper, a crushable absorber system is designed to analyze the dynamic behavior and performance of a helicopter seat. The mechanism of the absorption system makes use of the crash energy to plastically deform the aluminum material of the seat legs. Seat structure is composed of a bucket, two legs and two sliding parts on each leg. Seat legs are made of aluminum and and the sliding parts of the seat are steel. During the impact event, the heavier sliding parts move down and crash the aluminum material for the purpose of deforming the aluminum material under the sliding parts and reduce the crash energy. The designed helicopter seat is analyzed using the explicit finite element method to evaluate how the seat energy absorbing mechanism works. Dynamic simulations are performed in ABAQUS by crashing the seat to a fixed rigid wall. To simulate the plastic deformation, true stress-strain curve of the aluminum material of the seat leg has been used. Time response results are filtered to calculate the meaningful g loads which incur damage to the occupants. Analyses are performed with and without the energy absorption mechanism in order to see the effectiveness of the energy absorption mechanism on the human survivability by comparing the g loads on the seat bucket with the acceptable loads specified by EASA. This study is a preliminary study intended to check the effectiveness of the damping mechanism based on the plastic deformation of the aluminum legs of the seat in the event of a crash.

Topics: Absorption
Commentary by Dr. Valentin Fuster
2018;():V04BT06A047. doi:10.1115/IMECE2018-86774.

Hydraulic dampers are usually used to reduce the vibration of a vehicle, which convert the vibration energy into heat. Except for wasting energy, the unchangeable damping characteristic cannot adapt the various road conditions. Previous work on regenerative damper with changeable damping, which usually consist of one generator have some shortcomings, which consist of energy wasting and small range of damping tuning. Aiming at above problems, a new design principle with multiple-controlled generators is discussed in this paper. Furthermore, a new energy-harvesting damper with multiple-controlled generators (DMCG), which is based on the new design principle is designed. A prototype was built and tested by MTS testing system. The experiment results show that DMCG can not only tune the damping almost linearly, but also extract vibration energy as much as possible.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A048. doi:10.1115/IMECE2018-87175.

In this paper, negative stiffness in static state is made stable by constraining it in positive matrix. The stability of the system is tested using energy function. The motion of the two mass model system is described with a system of two coupled nonlinear differential equations. The numerical results are validated by comparing the predictions with calculations from analytical method. For small oscillations about the static equilibrium position the numerical model agree with analytical model. The developed model can be served as an efficient means of eliciting negative stiffness.

Topics: Stiffness
Commentary by Dr. Valentin Fuster
2018;():V04BT06A049. doi:10.1115/IMECE2018-87488.

Vibration suppression has been implemented for many years as a way for a building’s occupants to feel more comfortable in structures prone to horizontal swaying or vertical oscillation. Suppression of a structure’s natural vibrations becomes even more important when delicate work, like surgeries, will be performed within. The purpose of this experiment was to confirm the validity of a passive vibration suppression unit to reduce the vibration in a portable shelter floor where surgeries would take place. Impact tests were done to determine the natural frequency of the floor, and along with the weight of the floor, were used to calculate operating parameters for a tuned mass damper, or TMD. A TMD was then assembled and vibration suppression effects were tested at 4% of total floor mass, to confirm the viability of the design. Additionally, TMDs of 2%, 3%, 4%, and 5% of the mass of the floor and shaker combined were made so frequency sweep tests could be done. Finally, a cantilever beam TMD was made, to test effectiveness of an easily adjustable TMD variant. The produced TMDs are expected to reduce the time the floor is vibrating and reduce vibration of the floor by up to 60%, bringing oscillations within comfortable levels even at the floor’s natural frequency.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A050. doi:10.1115/IMECE2018-88691.

Acoustic filters, or mufflers, are used in a number of applications for suppression or attenuation of sound. These mufflers use pipes with side branches and/or Helmholtz resonators thus routing the flow through a number of passages wherein the waves are partially reflected resulting in sound power attenuation. With the idea of using a pipe for active noise cancellation to reduce cabin noise in propeller aircraft, we define an objective function that maximizes sound pressure (or other criteria) at a given frequency f0 while minimizing (attenuating) the pressure at other harmonics m1 f0, m2 f0 etc. within the frequency band. Thus, the device can be used to generate anti-noise at the first harmonic, while attenuating noise at higher harmonics. A design tool is developed here using an optimization technique. Plane wave propagation is assumed. A choice of objective functions can be user-specified. Details of the design parameters and objective functions are given followed by acoustic analysis details. Test results are then given which show that the code can be used as a valuable design tool for noise reduction.

Topics: Noise control , Design
Commentary by Dr. Valentin Fuster

Dynamics, Vibration, and Control: Vibrations of Continuous Systems

2018;():V04BT06A051. doi:10.1115/IMECE2018-86871.

This paper presents a general approach for the free vibration analysis of curvilinearly stiffened rectangular and quadrilateral plates using Ritz method employing classical orthogonal Jacobi polynomials. Both the plate and stiffeners are modeled using first-order shear deformation theory (FSDT). The displacement and rotations of the plate and a stiffener are approximated by separate sets of Jacobi polynomials. The ease of modification of the Jacobi polynomials enables the Jacobi weight function to satisfy geometric boundary conditions without loss of orthogonality. The distinctive advantage of Jacobi polynomials, over other polynomial-based trial functions, lies in that their use eliminates the well-known ill-conditioning issues when a high number of terms are used in the Ritz method; e.g., to obtain higher modes required for vibro-acoustic analysis. In this paper, numerous case studies are undertaken by considering various sets of boundary conditions. The results are verified both with the detailed Finite Element Analysis (FEA) using commercial software MSC.NASTRAN and for some cases, and with those available in the open literature for others. Convergence studies are presented for studying the effect of the number of terms used on the accuracy of the solution. The paper also discusses the effects of stiffener and plate geometric dimensions on the dynamic characteristics of the structure. The method also has an advantage of saving significant computational time during optimization of such structures as changing the placement and shape of stiffeners does not require repeated calculation of plate mass and stiffness matrices as the stiffener shapes are changed.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A052. doi:10.1115/IMECE2018-87134.

To study the impact of compliant terrains on the biomechanics of rapid legged movements, a well-known spring loaded inverted pendulum (SLIP) model is deployed. The model is a three-degrees-of-freedom system (3 DOF), inspired by galloping greyhounds competing in a racing condition. A single support phase of hind-leg stance in a galloping gait is taken into consideration due to its primary function in powering the greyhounds locomotion and higher rate of musculoskeletal injuries. To obtain and solve the nonlinear second-order differential equation of motions, the Lagrangian method and MATLABb R2017b (ode45 solver), which is based on the Runge-Kutta method, has been used, respectively. To get the viscoelastic behavior of compliant terrains, a Clegg hammer test was developed and performed five times on each sample. The effective spring and damping coefficients of each sample were then determined from the hysteresis curves. The results showed that galloping on the synthetic rubber requires more muscle force compared with wet sand. However, according to the Clegg hammer test, wet sand had a higher impact force than synthetic rubber which can be a risk factor for bone fracture, particularly hock fracture, in greyhounds. The results reported in this paper are not only useful for identifying optimum terrain properties and injury thresholds of an athletic track, but also can be used to design control methods and shock impedances for legged robots performing on compliant terrains.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A053. doi:10.1115/IMECE2018-87181.

Dynamic analysis of a multi-span beam structure carrying moving rigid bodies is essentially important in various engineering applications. With many rigid bodies having different speeds and varying inter-distances, number of degrees of freedom of the coupled beam-moving rigid body system is time-varying and the beam-rigid body interaction is thus complicated. Developed in this paper is a method of extended solution domain (ESD) that resolves the issue of time-varying number of degrees and delivers a consistent mathematical model for the coupled system. The governing equation of the coupled system is derived with generalized assumed mode method through use of exact eigenfunctions and solved via numerical integration. Numerical simulation shows the accuracy and efficiency of the proposed method. Moreover, a preliminary study on parametric resonance on a beam structure with 10 rigid bodies provides guidance for future development of conditions on parametric resonance induced by moving rigid bodies, which can be useful for operation of certain coupled structure systems.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A054. doi:10.1115/IMECE2018-87220.

This research explores parametric instabilities of the PGT driveline system and a stability-based method for ring gear rim thickness design. Parametric excitation of a planetary gear transmission (PGT) driveline system arises from two sources: 1) gear mesh stiffness variation, 2) Interaction between moving planets, flexible ring gear and boundary struts. Many researchers have studied the parametric instability of planetary gear transmissions due to gear mesh stiffness variation, however, the effect of interaction between moving planets, flexible ring and discrete boundary struts on parametric instabilities has not been fully studied before. Especially, for sufficiently thin ring gears, this kind of effect becomes even more significant. To illustrate the novel PGT rim design proposal, firstly, a structural dynamics model of a complete PGT driveline system with elastic ring gear supported by discrete boundary struts is established. Secondly, by applying Floquet method, the parametric instability behavior due to the second parametric excitation source is fully investigated. Lastly, the design guidelines for planetary gear transmission ring gear rim thickness are proposed based on system stability from a dynamical viewpoint. The analysis and results provide new and important insights into dynamics and design of lightweight planetary gear transmission ring gear rim.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A055. doi:10.1115/IMECE2018-88015.

This paper investigates the parametric resonance of electrostatically actuated MicroElectroMechanicalSystems (MEMS) cantilever resonators. The electrostatic force is modeled to include fringe effect. The MEMS consists of a cantilever over a parallel ground plate and an AC voltage between them. The actuation frequency is near first natural frequency of the cantilever beam. This leads to parametric resonance. It is of interest to investigate the amplitude frequency response of MEMS cantilever resonators. This paper uses the Homotopy Analysis Method (HAM), which is able to capture nonlinear behaviors for higher amplitudes, large parameters, and strong nonlinearities. The base method used for comparison in this work is the method of multiple scales (MMS). MMS is a perturbation method. It requires a relatively short computational time for simulations. Although the CPU time is advantageous, MMS is only accurate for weak nonlinearities and low amplitudes. It is in the interest to compare how well HAM captures the softening behavior of this system as opposed to MMS. In this paper the influences of Casimir forces and Van der Waals effects are included. Electrostatic, Van der Waals and Casimir forces are nonlinear. HAM is a deformation technique that continuously deforms the initial guess, provided to the procedure, to the exact solution. In this work the first and second order deformation equations are constructed for the equation of motion governing the behavior of the MEMS cantilever beam. In the first order deformation, HAM deviates from the solution obtained by MMS. This deviation demonstrates the power of the method to capture the softening behavior more accurately than MMS even at the 1st order deformation HAM. In the second order deformation construction, the HAM’s solution softens more than the previous, demonstrating that higher order deformation approximations result in higher accuracy. In the second order deformation, HAM contains the convergence control parameter. This parameter is chosen via the c0 curve approach. Up to 2nd order HAM deformations are evaluated for this paper. These higher order homotopy deformation solutions were developed and automated symbolically in the software Mathematica and tested numerically using Matlab software.

Commentary by Dr. Valentin Fuster
2018;():V04BT06A056. doi:10.1115/IMECE2018-88527.

The effect of all-inclusive generic offset payload characteristics on the modes of vibration and nonlinear characteristics of a rotating flexible manipulator with a revolute pair has been accomplished in the present article. A brief dynamic modelling and free vibration analysis to obtain the eigenspectrums of the system, whereafter nonlinear analysis of a manipulator with a general offset payload undergoing overall motion has been accomplished. Dynamic equation of motion and associated boundary conditions have been developed where the payload is considered as a mass whose center of gravity doesn’t coincide with the point of attachment with the manipulator. The effect of various system parameters such as offset mass, offset inertia, offset length, hub mass, actuated inertia and hub stiffness on eigenfrequency is well tabulated and the same effect on eigenspectrums is presented graphically. Further, MMS is employed to investigate the effect of parametric variation on the nonlinear behaviour and associated bifurcation of the rotating single-link flexible manipulator being harmonically driven at the joint under primary resonance considering the centrifugal forces acting on the link and payload as well. The present analysis indicated the pronounced effect of system mass, inertia, stiffness and rotating speed on the eigencharacteristics and bifurcations of a flexible manipulator with a rotating joint.

Commentary by Dr. Valentin Fuster

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