Compact servo driver for torque control of DC-servo motor based on voltage control

A new torque control method for DC-servo motors based on voltage control is proposed and investigated. Through analyzing the torque control system consisting of DC-servo motor, reduction gear and torque sensor, it is shown that torque control by voltage control is feasible. It is also possible to eliminate the static error of the output torque and the interference of the disturbance torque such as the friction at the reduction gear. According to the analysis, a prototype servo driver is developed. Since only the voltage control capability is needed for the servo driver, the volume and mass of the developed servo driver are around 30% of the conventional values. Through experiments using the developed servo driver, it is confirmed that accurate torque control is feasible by the proposed method.