Explosive Electric Actuator and Control for Legged Robots

Abstract

Unmanned systems such as legged robots require fast-motion responses for operation in complex environments. These systems therefore require explosive actuators that can provide high peak speed or high peak torque at specific moments during dynamic motion. Although hydraulic actuators can provide a large force, they are relatively inefficient, large, and heavy. Industrial electric actuators are incapable of providing instant high power. In addition, the constant reduction ratio of the reducer makes it difficult to eliminate the tradeoff between high speed and high torque in a given system. This study proposes an explosive electric actuator and an associated control method for legged robots. First, a high-power-density variable transmission is designed to enable continuous adjustment of the output speed to torque ratio. A heat-dissipating structure based on a composite phase-change material (PCM) is used. An integral torque control method is used to achieve periodic and controllable explosive power output. Jumping experiments are conducted with typical legged robots to verify the effectiveness of the proposed actuator and control method. Single-legged, quadruped, and humanoid robots jumped to heights of 1.5, 0.8, and 0.5 m, respectively. These are the highest values reported to date for legged robots powered by electric actuators.

Keywords

• Electric actuator
• Variable transmission
• Integral torque control
• Legged robot