A muscle-like recruitment actuator with modular redundant actuation units for soft robotics

Human muscles contrast sharply with traditional robot actuators in that they consist of several motor units, connected in series and parallel, which can be progressively recruited, or brought into the active state. Some roboticists have explored this idea in robotic actuators, striving for improvements such as the ability to withstand partial damage, inexpensive repeatability by discrete open loop control, the potential of modular actuators, etc. The down side of this is that these systems become rather complex or rely on less widely used actuation techniques such as piezo-actuators or SMAs to produce a compact implementation. In this paper, we present a novel design of a modular redundant actuation unit which can be combined in various combinations to form compliant actuators with varying characteristics. The actuation unit consists of discretely activated solenoids with an integrated compliant coupling. This paper presents the working principle and discusses the physical implementation in detail. Failure of a single motor unit will merely lead to a loss in performance rather than failure of the actuator. Since each motor unit is discrete, neither power electronics nor control require analog signals. Isometric experiments display the actuation ∗Corresponding author Email address: [email protected] (Glenn Mathijssen) Preprint submitted to Robotics and Autonomous Systems October 22, 2014 characteristics and demonstrate the repeatability of actuators composed of these actuation units. The platform can be used in future work to further explore the virtues of exploiting discretization and redundancy in muscle-like control.