A preliminary study for using reactive braking torque in variable impedance actuation

Variable impedance actuation is a new paradigm in robotics, which aims to reach the safety, dexterity and efficiency level of biological systems. Recent advances in the control of variable impedance actuated (VIA) robots offer new venues for the integration of additional types of actuation elements to these systems. In this work, we present our feasibility study of using a momentum wheel to augment explosive motions such as throwing, jumping, kicking for VIA robots. In our concept, the momentum wheel attached to the distal link of the robot is accelerated to a high speed with a low-weight and low-torque electrical motor and decelerated abruptly using a mechanical brake capable of generating high braking torques. We test this concept in simulation experiments for a ball throwing task using the model of a two-link variable stiffness robot with antagonistic actuator configuration. Simulation experiments indicate that the ball throwing performance of a VIA robot can be improved using a momentum wheel with a high rotational speed.