Jake McGrath, UT-Austin

"Bioinspired Actuation"

Abstract: Electromagnetic motors convert stored energy to mechanical work through a linear force–velocity (FV) relationship. In biological systems, however, muscle actuation is characterized by the hyperbolic FV mechanisms of the Hill muscle—in which a parameter α characterizes the degree of nonlinearity. Previous work has shown that bioinspiration in human-engineered systems can contribute favorable mechanical attributes—such as energy efficiency, self-stability, and flexibility, among others. In this study, we first construct an easily amendable, bioinspired electromagnetic motor which produces FV curves that mimic the Hill model of muscle with a high degree of accuracy. A proportional-integral-differential (PID) controller converges the characteristically linear FV relationship of a DC motor to nonlinear Hill-type force outputs. The bioinspired electric motor does a fixed amount of work by lifting a 147.5 g mass, and we record the translational velocity of the mass and the nonlinear applied force of the motor. Under optimized gain coefficients in the PID, the bioinspired motor achieves agreement of R^2~0.99 with the Hill muscle model. Studies have shown that designing biologically inspired actuators produce comparatively energy efficient systems. We investigate the energy economy of actuating our motor with nonlinear, Hill-type forces in direct comparison with conventional linear FV actuation techniques. We find that the bioinspired motor delivers energy economy with respect to energy consumption and conversion: the nonlinear, Hill-type DC motor reduces the energetic cost of actuation when delivering a fixed amount of mechanical work.