Position sensing and motor control in industrial robotics

Actual industrial robots are rigid mechanical manipulators, with simple and kinematically solvable mechanical structures. Modern robots are actuated by permanent magnet (PM) brushless synchronous motors and a computer system is used to control and supervise the robot motion, using sensor information to obtain the environment and robot status. Generally those controllers implement a simple positional control law and are closed to the advanced user, i.e., generally direct access to motor torques and position information is not allowed, and the user cannot change the positional control law. In this paper, the authors briefly present the basics of position sensing, motor joint actuation and control of a typical industrial manipulator. In the process, the basic processing and control circuits are presented and discussed. After that, they briefly introduce an implementation of those circuits, designed and built at their laboratory with the objective of allowing access to joint positions and motor reference signals. The low level software designed to operate with the circuits is also briefly introduced and the advantages and achievements of the new circuits explained