Full Content is available to subscribers

Subscribe/Learn More  >

Model-Based Shape Memory Alloy Wire Ratchet Actuator Design

[+] Author Affiliations
Wonhee Kim, Brent Utter, Jonathan Luntz, Diann Brei

University of Michigan, Ann Arbor, MI

Hanif Muhammad, Paul Alexander

General Motors R&D, Warren, MI

Paper No. SMASIS2013-3333, pp. V001T04A018; 12 pages
  • ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems
  • Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Integrated System Design and Implementation
  • Snowbird, Utah, USA, September 16–18, 2013
  • Conference Sponsors: Aerospace Division
  • ISBN: 978-0-7918-5603-1
  • Copyright © 2013 by ASME and General Motors


Shape Memory Alloy (SMA) wire ratchet actuators overcome SMA wire strain limitations by accumulating actuation stroke over multiple cycles. The underlying architecture is effective for producing large strokes from a small package, creating continuous rotation or extended displacement, and precise. It also provides discrete positioning with zero-power hold. While there have been several successful implementations of SMA ratchet actuators, most are designed ad-hoc since limited models exist to predict the stroke and force interaction during actuation cycles. Since the SMA wire actuation is highly dependent on the forces experienced through the ratchet mechanism, a model requires the prediction of the force interaction between the rack and pawl teeth along with friction in the device, and of the external force variation over actuation cycles due to the relative position change between the external system and the SMA wire. This paper presents a model-based systematic design methodology for SMA ratchet actuator which actuates position-dependent external systems. A generalized ratchet mechanism and operation sequence is introduced along with a force balance model for both austenite and martensite equilibrium to address the mechanical coupling changes. Analytical kinematic and kineto-static rack and pawl interaction models are reviewed, which feed into the force balance models. The effective stroke is evaluated by subtracting backlash from the SMA wire stroke, found through equilibrium with the mechanism and external system. This effective stroke accumulates to produce the overall actuator motion. A design methodology is suggested along with visualization methods to aid design decisions. Parametric studies expose the effects of design parameters on the SMA ratchet actuator to gain further design insight. This model-based design foundation and parametric understanding enable the synthesis of SMA wire ratchet actuators.

Copyright © 2013 by ASME and General Motors



Interactive Graphics


Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In