Meeting Abstract

P1.78  Saturday, Jan. 4 15:30  Seeking muscle-tendon properties in robotic legs: Designing a piezoelectric series-elastic actuator SCHROEDER, R.T.*; LEE, D.V.; Univ. of Nevada, Las Vegas schroe95@unlv.nevada.edu

New actuation technologies are needed for the advancement of robotics and prosthetics. In fact, the disparity between the operating principles of electromagnetic motors (EMMs) and skeletal muscle is well known. For example, biological muscle (BM) functions at low frequencies while achieving peak forces. This behavior, characterized by the force-velocity curve of muscle, shows a direct contradiction to the nature of EMMs, which dictates that they must rotate at high speeds in conjunction with large gear reductions to produce any sizable torques. Because of this fundamental contradiction, as well as other inadequacies (e.g. torque fidelity, torque density), we predict that piezoelectric motors (PEMs) will mimic the functions of BM more effectively. It is known that PEMs exhibit a sort of locked-clutch behavior, which allows them to sustain static positions while wasting little to no energy. This ratcheting effect mimics the cross-bridge cycling, which occurs in a sliding filament. Also, the force-velocity curve of PEMs is similar to that of a BM. However, PEMs have not yet been tested in artificial muscles. Thus, our study investigates PEMs for a design capable of mimicking BM. An experimental prototype has been designed in order to verify the comparative operating principles of both motors. This design consists of an actuator system in which a load wheel is pulled by two artificial tendons (compliant cables) in order to mimic a flexor/extensor coupling in BM. The inherent characteristic of co-contraction allows for a control system capable of biomimetic operation. By comparing the performances of PEMs with EMMs in a biomimetic robotic system, we predict that a clear advantage will be exposed, in favor of the PEMs.