Direct-Drive Position Control of a Spiral Motor as a Monoarticular Actuator

This paper presents the direct-drive position control verification of a spiral motor in monoarticular configuration. The spiral motor is a newly developed high-thrust high-backdrivable direct-drive three-phase permanent-magnet motor with a unique 3-D structure. One of the possible uses of the spiral motor is to actuate musculoskeletal-like structure which is shown in animals and humans. This is achieved by indirectly actuating the elbow/shoulder joints via pulling/pushing the links by using a linear actuator. We describe the control methods for the direct drive of the spiral motor which are the decoupling control and independent control. Next, simulations were performed to assess the control parameter variation effects. Then, the experimental results confirm the validity of the control method in monoarticular position. The key element of the linear motion control of the spiral motor is the magnetic levitation (air gap between the stator and rotor) control and simultaneous angular motion control via vector d- and q-axis currents.