Load torque control of an electromagnetic motor with a reduction gear and motor/load‐side encoders using a spring model including a dead zone

Actuators with characteristics such as light weight, a high torque/weight ratio, and a high torque control performance are desired for contact tasks using robots. Although electromagnetic motors with gears have these features, friction in gears degrades the torque control performance. Therefore, in this study, the load torque control performance is improved by utilizing motor/load side angle information. Both the torque controller and the load torque observer in the proposed control system utilize motor/load side encoders and the spring model, which includes a dead zone. The dead zone model represents the backlash between the motor output shaft and the reducer output shaft. A simulation and experiment show the efficacy of the proposed control system.