CINCINNATI MILACRON T3 ROBOT ARM-ASSIGNMENT

INTRODUCTION
A typical industrial robotic controller consists of twocontroller levels, a system level controller and servo loopcontrollers. The system level controller calculates the setpoints for each servo loop controller. Various types ofcontrol algorithms can be used to generate the set pointssuch as position, velocity or torque. The servo loopcontrollers perform low level control on each of the robot'sactuators. A 6 degree of freedom robot requires 6 servocontrollers.The University of Texas at Austin Robotics ResearchGroup is engaged in research which demonstrates that anindustrial robot can be utilized in precision light machiningwithout jigs [l] and for other high value added processes.The robot used by the Robotics Research Group is aCincinnati Milacfon Inc. (CMI) T3-776 heavy dutyindustrial robot. The robot's factory controller consists of aCMI ACRAMATIC version 4 system controller and CMISilicon Controlled Rectifier (SCR) servo loop controllers 'Ws work was qqmcted in pnrt by the State dTexas un&r ATPGrant No.4679 and U. S. Depaament d Energy under Grant No. DE--86NE379966 which are manufactured by Siemens. It became apparentthat the existing system controller of the T3-776 was notcapable of executing complex control strategies.Most current industrial robot system controllers aredesigned for a particular machine. Each brand and, in somecases, model of robot has a different controller architecture.Thus control algorithms designed for one robot cannotnecessarily be ported to anothex. The Robotics ResearchGroup decided to replace the system controller with a highspeedgeneric controller which can be interfad to almostany robot with minimal changes to the system architecture.The new system controller, the Multi-Channel RoboticController (MCRC), by-passed the ACRAMATIC controllerby interfacing to the robot's sensors and outputting thecommand set points directly U, the Semen servo loopControllers. After the initial upgrade of the systemcontroller, it became apparent that the servo controllers werea major bottleneck in the robot's performance. Theremaining sections in this paper will discuss the new systemcontroller, the new servo controllers, and the robot'sperformance enhancements due to these new controllers.