Load disturbance and environment effect on biarticular manipulator driven by spiral motors

In this paper, we propose passive control of a musculoskeletal biarticular structure driven by direct-drive spiral motors. The spiral motor is a three-dimensional helical three-phase PM motor without any additional mechanism that achieves forward and backward direct-drive linear actuation by magnetic levitation of the rotor and angle control. At first the dynamics of the structure including the spiral motor are shown. Then the passive control scheme of the spiral motor is explained. By giving zero muscle force reference to each muscles, the angle control variables compensates gap control variables to realize passive control of the manipulator. The simulation results on the manipulator show feasibility of maintaining air-gaps during passive control and experimental results on single monoarticular structure validates the control.