Parallel robots have been primarily investigated as potential mechanisms with stiffness modulation capabilities through the use of actuation redundancy to change internal preload. This paper investigates real-time stiffness modulation through the combined use of kinematic redundancy and variable stiffness actuators. A known notion of directional stiffness is used to guide the real-time geometric reconfiguration of a parallel robot and command changes in joint-level stiffness. A weighted gradient-projection redundancy resolution approach is demonstrated for resolving kinematic redundancy while satisfying the desired directional stiffness and avoiding singularity and collision between the legs of a Gough/Stewart parallel robot with movable anchor points at its base and with variable stiffness actuators. A simulation study is carried out to delineate the effects of using kinematic redundancy with or without the use of variable stiffness actuators. In addition, modulation of the entire stiffness matrix is demonstrated as an extension of the approach for modulating directional stiffness.
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October 2019
Research-Article
Directional Stiffness Modulation of Parallel Robots With Kinematic Redundancy and Variable Stiffness Joints
Andrew L. Orekhov,
Andrew L. Orekhov
Department of Mechanical Engineering,
Nashville, TN 37235
e-mail: andrew.orekhov@vanderbilt.edu
Vanderbilt University
,Nashville, TN 37235
e-mail: andrew.orekhov@vanderbilt.edu
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Nabil Simaan
Nabil Simaan
Department of Mechanical Engineering,
Nashville, TN 37235
e-mail: nabil.simaan@vanderbilt.edu
Vanderbilt University
,Nashville, TN 37235
e-mail: nabil.simaan@vanderbilt.edu
Search for other works by this author on:
Andrew L. Orekhov
Department of Mechanical Engineering,
Nashville, TN 37235
e-mail: andrew.orekhov@vanderbilt.edu
Vanderbilt University
,Nashville, TN 37235
e-mail: andrew.orekhov@vanderbilt.edu
Nabil Simaan
Department of Mechanical Engineering,
Nashville, TN 37235
e-mail: nabil.simaan@vanderbilt.edu
Vanderbilt University
,Nashville, TN 37235
e-mail: nabil.simaan@vanderbilt.edu
Contributed by the Mechanisms and Robotics Committee of ASME for publication in the Journal of Mechanisms and Robotics. Manuscript received July 2, 2018; final manuscript received April 26, 2019; published online July 8, 2019. Assoc. Editor: Shaoping Bai.
J. Mechanisms Robotics. Oct 2019, 11(5): 051003 (9 pages)
Published Online: July 8, 2019
Article history
Received:
July 2, 2018
Revision Received:
April 26, 2019
Accepted:
April 26, 2019
Citation
Orekhov, A. L., and Simaan, N. (July 8, 2019). "Directional Stiffness Modulation of Parallel Robots With Kinematic Redundancy and Variable Stiffness Joints." ASME. J. Mechanisms Robotics. October 2019; 11(5): 051003. https://doi.org/10.1115/1.4043685
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