Position and force control of SPM-type high-thrust-force linear motor for assistive devices

This paper reports high-performance position and force control of helical motion motors. This motor is an axial-gap surface permanent magnet (SPM) synchronous motor having helical stator and rotor. Thanks to this shape, this direct-drive motor can generate high thrust force without using any mechanical transmission system. The experimental results show that thrust force of 200N is achieved by the proposed motor of φ55×132mm size. The thrust-force density is 0.64MN/m³ and force-to-mass ratio is 133N/kg which is two or more times higher than the conventional linear motors.