Development of a high performance direct-drive joint

This paper reports on advances in the design and development of a high-performance direct-drive joint for robotics and automation. The joint integrates a motor, a torque sensor and joint bearings. The key design aspects of the motor, such as the armature, motor housing, bearing arrangement and sensors, are detailed. The description of a dynamometer testbed with a hydraulic active load used for motor calibration and to test the dynamic behavior of the motor and its entire control system is also given. We also present a number of advanced implementations in control, motor torque control and motion control using positive joint torque feedback. Experimental results illustrate outstanding performance regarding thermal response, torque ripple, reference trajectory tracking, torque disturbance rejection and joint stiffness.