Biological Actuators Are Not Just Springs
While there is a trend in current robotics towards more biologically inspired actuators, most work emphasizes the elastic property of muscles and tendons. Although elasticity plays a major role in many forms of movements, particularly walking and running, other features of animal muscles might also affect or even dominate movement dynamics. In this paper we use the Hill-type muscle model, common in biomechanics, to investigate the relationship between muscle dynamics and control signals in simple goal-directed movements. We find that the various non-linearities of the model lead to desirable properties with regard to controllability, such as increased stability and robustness to noise, independence of position and stiffness, or near linearity in search space. We conclude that in our attempt to create robots exhibiting the same flexibility and robustness as animals we have to seek a balance between the complexity of actuators and the extent to which their natural dynamics can be exploited in a given task.
KeywordsControl Signal Joint Position Muscle Model Interaction Torque Antagonistic Muscle
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- 1.Bar-Cohen, Y.: Electroactive Polymer (EAP) Actuators as Artificial Muscles - Reality, Potential and Challenges, vol. PM98. SPIE Press, San Jose (2001)Google Scholar
- 2.Feldman, A., Ostry, D., et al.: Recent tests of the equilibrium-point hypothesis (lambda model). MotorControl 2, 189–205 (1998)Google Scholar
- 4.Gribble, P.L., Ostry, D.J., Sanguineti, V., Laboissiere, R.: Are Complex Control Signals Required for Human Arm Movement? J. Neurophysiology 79, 1409–1424 (1998)Google Scholar
- 5.Brown, I.E., Loeb, G.E.: A reductionist approach to creating and using neuromusculoskeletal models. In: Winters, J.M., Crago, P.E. (eds.) Biomechanics and Neural Control of Posture and Movement. Springer, New York (2000)Google Scholar
- 7.Pfeifer, R., Iida, F.: Morphological computation: Connecting body, brain and environment. Japanese Scientific Monthly 58(2), 48–54 (2005)Google Scholar
- 8.Pfeifer, R.: Building ‘fungus eaters’: Design principles of autonomous agents. In: Maes, P., Mataric, M.J., Meyer, J.A., Pollack, J., Wilson, S.W. (eds.) From Animals to Animats 4: Proceedings of the Fourth International Conference on Simulation of Adaptive Behavior. MIT Press, Cambridge (1996)Google Scholar
- 9.Pratt, J.E., Krupp, B.T.: Series Elastic Actuators for Legged Robots. SPIE, San Jose (2004)Google Scholar
- 12.Zajac, F.E.: Muscle and tendon: properties, models, scaling, and application to biomechanics and motor control. CRC Crit. Revs. biomed. Engng. 17, 359–411 (1989)Google Scholar