Members of the animal kingdom produce motion by muscle contraction. Biological muscle can be viewed as a unidirectional actuator. To achieve bidirectional motion, each muscle has a corresponding antagonist muscle whose contraction produces motion in the opposite direction. This gives biological systems the unique ability to modulate the stiffness of a joint, which is important when interacting with the environment. Certain bio-inspired robotic systems incorporate antagonistic pairs in an attempt to produce similar desirable properties. The cellular actuator employs nested compliant mechanisms to produce human-scale motion from piezoelectric stack actuators, which on their own have a small displacement. The expression for the stiffness of the actuator composed of these mechanisms takes the form of a continued fraction, which results from the nested structure. In this way, the stiffness can be easily approximated to a desired degree of accuracy by considering only the outermost mechanisms.
- Dynamic Systems and Control Division
Analysis of Antagonist Stiffness for Nested Compliant Mechanisms in Agonist-Antagonist Arrangements
Schultz, JA, & Ueda, J. "Analysis of Antagonist Stiffness for Nested Compliant Mechanisms in Agonist-Antagonist Arrangements." Proceedings of the ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control. ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control, Volume 2. Arlington, Virginia, USA. October 31–November 2, 2011. pp. 407-410. ASME. https://doi.org/10.1115/DSCC2011-5953
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