10 - Biomimetic muscle—The slipping/sliding friction mechanism (SFM) for dynamic agile animal robots

Abstract

The need for a biomimetic muscle is described and is followed by a review of state-of-the-art biomimetic muscles, including their advantages and disadvantages and why these actuators are proving to be of limited use as biomimetic muscles. A new species of biomimetic artificial muscle that is suitable as a biomimetic muscle is then described. This new species accurately emulates skeletal muscle in terms of performance, summarized as energy efficiency, back drivability, controllability, power-to-weight ratio, power-to-volume ratio, and force resolution. This new species of biomimetic muscle is a mechatronic “sliding friction mechanism” (SFM), which produces a unidirectional force via sliding friction that will enable a new genre of dynamic agile animal robots that can sprint, jump, fly, and swim fast. Since the SFM produces a unidirectional force, a pair of SFMs is required to bidirectionally actuate a single limb. The SFM is designed to be equally as effective as in (i) static position holding (as in a displacement servomechanism) and (ii) motion articulation (as in a velocity servomechanism) of robot limbs. A proof-of-concept prototype has been built and successfully tested and a more advanced, more powerful prototype is under construction. The device creates a force impulse which can be programmed as a force-time signature. The device possesses ultra low bidirectional output impedance, i.e., extremely high forward and backward drivability and this back drivability is obtained, uniquely, using a passive method. The term, “output impedance” is defined in the main text. A force actuator with the property of low bidirectional output impedance obtained passively is the primary characteristic for mimicking biological skeletal muscle. Finally, the SFM proof-of-concept apparatus is described together with a basic control methodology.