Design of a Friction Drive Actuator with Integrated Force and Torque Sensors

This paper presents an actuator design with integrated force and torque sensors. The actuator is a friction drive composed of two preloaded cylinders. A rod that has to be axially actuated is guided between the cylinders. The axial force sensor is located on the motorized cylinder while the torque sensor is mounted on the passive cylinder. Both sensors are based on flexible mechanical structures. Deformations of the structures are measured by infrared (IR) reflective sensors, enabling sensing without electrical wiring on moving parts. A ray-optics model for behavior of reflective IR sensor is proposed and validated with experiments. The model enables the study of sensor combination for mechanical unbalance cancellation and coupling rejection. Calibration results and performances of the sensors as well as the complete actuator prototype are presented