Development and control of a novel cylindrical IPM linear vernier motor for compliant robot actuation

We have been studying small sized direct-drive electromagnetic linear actuators and their control method. These actuators were able to emulate the viscoelastic characteristics of the human muscle by PD position control to respond to external forces flexibly. However, their thrust force was not enough in order to apply to legs and shoulders of robots. In this paper, we present a novel small cylindrical linear vernier motor for artificial muscle of humanoid robots. First, the structure and operating principle of the proposed linear vernier motor are described. Then, the thrust and detent force of the motor are shown by 2D finite element analysis and measurement on a prototype. As the result, the validity of the simulation is discussed. Finally, the effect of the position controller with the disturbance observer on reduction of detent force and deviation between target and actual mover position is clarified.