A Precision Direct-Drive Robot Arm

This paper describes the design and performance of an articulated direct-drive robot arm with six degrees of freedom. All the robot's joints are driven by high torque variable-reluctance stepping motors, each with integral ultra-high-resolution (20-bit) optical shaft encoder. By using direct drive motors and a microprocessor-based servo and trajectory controler, high resolution, and repeatability of better than 0.01 mm were obtained. The robot arm was developed as part of a distributed robot control system (YEWBOT) which included vision and other sensors, and a robot language to drive the system.