Investigations of a Robotic Testbed with Viscoelastic Liquid Cooled Actuators.

We design, build, and thoroughly test a new type of actuator-dubbed viscoelastic liquid cooled actuator (VLCA) for robotic applications. VLCAs excel in the following five critical axes of performance: energy efficiency, torque density, impact resistance, joint position, and force controllability. We first study the design objectives and choices of the VLCA to enhance the performance on the above-mentioned criteria. We follow this study by an investigation on viscoelastic materials in terms of their damping, viscous, and hysteresis properties as well as their long-term performance. As part of the actuator design, we devise a disturbance observer to provide high-fidelity force control for a wide range of impedance control capabilities. We proceed to design a robotic system capable to lift large payloads with high output power. In addition, we experiment with quick trajectory control while carrying moderate payloads. Finally, we perform experiments on impedance control capabilities and mechanical robustness by studying the response of the robot to impacts produced by a hammer and human-induced external forces. Overall the main contribution of this paper is on the invention of a VLCA using elastomers with a pistonlike ball screw drive for multidof robots and the thorough investigation of its robotics performance.