Unimation, Inc.

Timothy P Skewis

Rajan C Penkar

A digital control is provided for a robot having a plurality of arm joints. The control includes an electric motor for driving each of the robot arm joints and a power amplifier supplies drive current to each motor. Each joint motor has feedback control loop means including at least digital position, velocity and torque control loops operable at a predetermined sampling rate to control the associated power amplifier. Digital motor position, velocity and drive current feedback signals are generated for the control loop means for all of the robot axes. Paired system microprocessors or paired position/velocity microprocessors generate position commands for the feedback control loop means in accordance with predefined moves set forth in a robot program. A planning program generates a time profile including acceleration, slew and deceleration time segments for each commanded robot program move. A trajectory program generates position commands for each of the feedback control loop means in accordance with a curved path trajectory and in accordance with the time profile applicable to the current move segment. The trajectory program employs stored third order polynomial equations and arc equations each having predetermined variable parameters operative to particularize that equation to a commanded curved path segment. The trajectory program responds to parameters specified by the robot program and implements the stored equations corresponding to the specified parameters to generate the position commands and define a tool tip trajectory corresponding to the curved path defined by the robot program.

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Roxbury, CT, United States of America

Timothy P Skewis