Contactless magnetic gear for robot control application

This paper describes the application of a magnetic gear to a robot by fulfilling the essential requirements for a robot control, which are velocity control, position control, and force control. A magnetic gear is a transmission device that realizes contactless torque transmission by applying a magnetic force. When using a magnetic gear, cogging torque and spring characteristics need to be considered. In this paper, we introduce an approximate model of cogging torque. This model is used for velocity control to attenuate the disturbance due to cogging torque. In the case of position control, the oscillations due to the spring effect of the magnetic attractive force become a problem. To reduce the adverse effect due to these oscillations, resonance ratio control is applied. We also propose to use a magnetic gear for realizing the force sensorless bilateral control of teleoperation. Thanks to the frictionless transmission of a magnetic gear, the force sensorless estimation of a reaction force can be realized using a reaction force observer.