Force control of a spiral motor and its application to musculoskeletal biped robot

This paper proposes force control of a spiral motor in combination with zero-power magnetic levitation control. The motor has a helical-shape mover, which moves in a helical-shape stator without contact. Due to the manufacturing process, the actual spiral motor contains fluctuation of neutral point of the air-gap displacement depending on the mover rotation angle. The d-axis current remain a finite value and copper loss arises even when the mover is located at the center between the stator cores. Zero-power magnetic levitation control is proposed to solve this problem. The proposed control is experimentally verified. In addition, a model of a musculoskeletal biped robot equipped with spiral motors is introduced.