Torque Sensors for Robot Joint Control

摘要

In Chapter, the stages of the joint torque sensor design are presented. New torque sensors for implementation of virtual backdrivability of robot joint transmissions have been developed. Torque measurement techniques, namely, electrical, electromagnetic, and optical, are discussed in detail. Technical requirements aimed at designing the highperformance torque sensor for humanoid robot arm were formulated. The substantial advantages of the optical technique motivated our choice in its favor. The main novelty of our method is application of the ultra-small size PI as sensitive element to measure relative motion of sensor components. The hub-spoke, ring-shaped, and semi-ring-shaped topologies of the sensor spring member were designed and investigated in order to optimize the mechanical structure of the detector. Hub-spoke structure was proven to be the most suitable solution allowing realization of compact sensor with high resolution. The designed optical torque sensors are characterized by good accuracy, high signal-to-noise ratio, compact sizes, light in weight, easy manufacturing, high signal bandwidth, robustness, low cost, and simple calibration procedure. In addition to contact force, torque sensor continuously measures the gravity and dynamic load. To extract the value of the contact force from sensor signal, we elaborated algorithm of calculation of torque caused by contact with object.