Torque Sensor Embedded Actuator Module for Robotic Applications

Measuring accurate torque is a core ability of advanced robotic technologies. However, embedding torque-sensing systems into robot joints are still a challenge due to limitations including size, weight, and cost. Moreover, the influence from axial forces/torques (x- and y-axis) and the sinusoidal effect from the harmonic drive make it difficult to measure torque accurately. This paper presents a novel actuator module for robotic applications that includes a torque sensor, harmonic drive, motor, and encoder. The torque sensor adopts the capacitive sensing scheme, which can allow for self-decoupling of the axial influences through the use of a symmetric arrangement of sensing cells. Moreover, the torque ripple cancellation method, which can reduce the sinusoidal effect from the harmonic drive, is introduced. Finally, the detailed design of the actuator module is described, and its performance is experimentally evaluated.