Multiaxis robot control having improved continuous path operation

摘要

A digital control for a robot having a plurality of arm joints includes an electric motor for driving each of the robot arm joints and a power amplifier operable to supply drive current to each motor. Pulse width modulators generate digital control signals for the power amplifiers. Feedback control loop means for each joint motor includes at least position, velocity and torque control loops operable to control the associated power amplifier. Motor position, velocity and drive current feedback signals are generated for the control loop means for all of the robot axes. A position/velocity microprocessor control executes a planning program to generate a time profile including acceleration, slew and deceleration time segments for implementing each commanded robot program move. It also executes a trajectory program to generate interpolated position commands for each of the feedback control loop means along the present path segment in accordance with a predefined type of path move and in accordance with the time profile applicable to the present path segment. Execution of a continuous path routine in the planning program provides for computation of coefficients for a stored polynomial equation to enable the position commands to be generated in joint and Cartesian moves as tool orientation and tool position commands that produce smoothed robot tool motion both in tool orientation and tool position between the initial transition point at the end of the slew portion of one path segment to the end transition point at the beginning of the slew portion of the next path segment. The trajectory program computes from the polynomial coefficients interpolated position commands that produce smoothed tool positioning and orientation motion between path segments without position, velocity and acceleration discontinuities in the operation of each of the feedback loop means. The position/velocity microprocessor control computes torque commands from the position command and position/velocity feedback for all of the axes. A torque microprocessor control generates voltage commands for the pulse width modulators from the torque commands and motor current feedback for all of the axes.