Investigations of viscoelastic liquid cooled actuators applied for dynamic motion control of legged systems

To significantly improve actuation technology for legged systems, we design, build, and empirically test the viscoelastic liquid cooled actuator (VLCA) for use in a robotic leg. Unlike existing actuators, VLCAs excel in the following five critical axes of performance, which are essential for dynamic motion control of practical legged robots: energy efficiency, power density, impact-resistance, position controllability, and force controllability. In this paper, we explain design details with respect to the five criteria, and present results from our extensive study of a variety of viscoelastic materials. Position controllability and power density are experimentally evaluated by demonstrating dynamic motion with a single leg testbed, custom-built using VLCAs. In the experiment, the testbed shows 6.1 rad/s maximum velocity and 240 Nm maximum torque while accurately executing the commanded motions.