Development of an optical type torque sensor and application to impedance control

Abstract

This thesis describes to design an optical torque sensor and analyze its influences on impedance controller. Impedance control adjusts dynamic interaction between manipulator and environment, which provides a robot compliance. Capacitive type or optical type torque sensors have been adopted for force control recently since strain gauge-based torque sensor have bonding and wiring problems. These sensors could measure rough torque signal exerted by unexpected environment that surrounds a robot, which would affect the control quality. To analyze the control performance on sensor types, we developed a novel optical type torque sensor and implemented impedance control. The proposed torque sensor is designed to measure up to 30Nm and have two optical chips symmetrically in order to decouple undesired load components, which shows lower interference rate than the commercial optical torque sensor. Static calibration and dynamic test were conducted. Finally, the control performance indices were compared between strain gauge type and proposed sensor with frequency. The results imply that the robot could provide ensuring safety by using optical torque sensor instead of strain-gauge torque sensor.