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.

assignment

Servomechanism
A system for the automatic control of motion by means of feedback. The term servomechanism, or servo for short, is sometimes used interchangeably with feedback control system (servosystem). In a narrower sense, servomechanism refers to the feedback control of a single variable (feedback loop or servo loop). In the strictest sense, the term servomechanism is restricted to a feedback loop in which the controlled quantity or output is mechanical position or one of its derivatives (velocity and acceleration).
The purpose of a servomechanism is to provide one or more of the following objectives: (1) accurate control of motion without the need for human attendants (automatic control); (2) maintenance of accuracy with mechanical load variations, changes in the environment, power supply fluctuations, and aging and deterioration of components (regulation and self-calibration); (3) control of a high-power load from a low-power command signal (power amplification); (4) control of an output from a remotely located input, without the use of mechanical linkages (remote control, shaft repeater).
The illustration shows the basic elements of a servomechanism and their interconnections; in this type of block diagram the connection between elements is such that only a unidirectional cause-and-effect action takes place in the direction shown by the arrows. The arrows form a closed path or loop; hence this is a single-loop servomechanism or, simply, a servo loop. More complex servomechanisms may have two or more loops (multiloop servo), and a complete control system may contain many servomechanisms.
Servomechanisms were first used in speed governing of engines, automatic steering of ships, automatic control of guns, and electromechanical analog computers. Today, servomechanisms are employed in almost every industrial field. Among the applications are cutting tools for discrete parts manufacturing, rollers in sheet and web processes, elevators, automobile and aircraft engines, robots, remote manipulators and teleoperators, telescopes, antennas, space vehicles, mechanical knee and arm prostheses, and tape, disk, and film drives.

Cincinnati Milacron T3 Industrial Robot
This robot is a more classically designed industrial robot. Designed as a healthy compromise between dexterity and strength this robot was one of the ground breakers, in terms of success, in factory environments. However, while this robot was a success in industry its inflexible interfacing system makes it difficult to use in research.
This robot is used most heavily by students taking Dr. Delbert Tesar's "Robotics and Automation" course (ME 372J) from the Mechanical Engineering Department of the University of Texas at Austin.

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