Multiaxis digital robot control having a backup velocity monitor and protection system

DETAILED DESCRIPTION A digital control is provided for a robot having a plurality of arm joints.
An electric motor drives each of the robot arm joints and a power amplifier operates to supply drive current to each motor.
Each joint motor has digital feedback control loop means operable at a predetermined sampling rate and including digital position and velocity control loops driving a digital torque control loop in accordance with digital position commands to generate digital motor voltage commands for controlling the associated power amplifier.
Means are provided for sensing the motion of each joint motor and for generating corresponding digital position and primary velocity feedback signals for control calculations in the position and velocity control loops.
Means are also provided for generating digital signals representative of the respective joint motor drive currents for control calculations in the torque control loop.
Backup velocity monitoring means independently determines the velocity of each joint motor from the motor current and terminal voltage and the motor inductance and resistance.
Comparisons are made between the primary and backup velocity signals for each joint motor.