Control method for a robot

A method for controlling an industrial robot, which robot has at least one axis of rotation and/or translation and an apparatus for controlling the robot, the apparatus comprising at least one actuator at said at least one axis for driving a movement of an arm of the robot, at least one sensor at each rotatable shaft of said arm, a dither-signal generator for generation of a periodic signal to provide a varying dither signal to a servo of said at least one actuator, the method comprising:

• determining an amplitude of a current dither movement of said actuator;
• calculating a deviation from a known reference value of the dither movement;
• sending a control error signal representing the dither movement amplitude deviation to an integrating controller;
• and
• providing an integrated reference signal to a multiplier means and by so doing cause the dither amplitude signal to be automatically adapted to a current operating state.

A computer readable storage medium containing an executable computer program configured to control an industrial robot, which robot has at least one axis of rotation or translation and an apparatus for controlling the robot, the apparatus comprising at least one actuator at said at least one axis for driving a movement of an arm of the robot, at least one sensor at each rotatable shaft of said arm, a dither-signal generator for generation of a periodic signal to provide a varying dither signal to a servo of said at least one actuator, the computer program performs the steps of:

• determining an amplitude of a current dither movement of said actuator;
• calculating a deviation from a known reference value of the dither movement;
• sending a control error signal representing the dither movement amplitude deviation to an integrating controller;
• and
• providing an integrated reference signal to a multiplier and by so doing cause the dither amplitude signal to be automatically adapted to a current operating state.

A control system for an industrial robot, which robot comprises at least one axis of rotation or translation and a robot control apparatus, the robot apparatus comprising at least one actuator at each of said axes configured to drive a movement of an arm of the robot, at least one sensor at each of the rotatable shafts configured to measure shaft angle or rotary position, a dither-signal generator configured to generate a periodic signal to provide a varying dither signal to a servo of said at least one actuator, the control system comprising:

• a computer program stored on a computer readable storage medium and configured to determine what the amplitude of the current dither movement should be;
• and
• a dither control loop configured to automatically adapt the dither amplitude signal;
• wherein the dither control loop is configured to apply a gain (Kad) to a dither amplitude control error (Δ{tilde over (φ)}) and integrate with an integrator the dither amplitude control error (Δ{tilde over (φ)}) before or after applying the gain (Kad).