Method And Controller System For Controlling Backlash

A computer program for controlling backlash by means of a first motor arranged to drive a first gear and a second motor arranged to drive a second gear, which first gear and second gear are mechanically connected in parallel with an actuator gear, and which first gear, second gear and actuator gear form a gear train, wherein the computer program includes computer code which, when run on a processing unit of a controller system, causes the controller system to:

• a) obtain a current position of the actuator gear relative to a reference position of the gear train,
• b) obtain a current backlash value for the current position from a data structure including a plurality of pairs of positions of the gear train and corresponding backlash values which have ail been determined in an empirical manner for the actuator gear, the first gear and the second gear under control, which positions contained in the data structure are distributed along the entire work range of the actuator gear, and wherein the current backlash value is obtained by finding a position of the gear train in the data structure corresponding to the current position and thereby identifying the corresponding backlash value,
• c) determine a first backlash compensation for the first motor and a second backlash compensation for the second motor, wherein the first backlash compensation is based on a first component that includes the current backlash value with the sign of the first component being a function of a motor torque of the first motor and the second backlash compensation is based on a third component that includes the current backlash value with the sign of the third component being a function of a motor torque of the second motor, and
• d) control the first motor based on the first backlash compensation and controlling the second motor based on the second backlash compensation.

A controller system configured to control backlash by means of a first motor arranged to drive a first gear and a second motor arranged to drive a second gear, which first gear and second gear are mechanically connected in parallel with an actuator gear, and which first gear, second gear and actuator gear form a gear train, wherein the controller system comprises:

• a processing unit, and
• a storage unit containing computer code, wherein the computer code when run on the processing unit causes the controller system to:
• a) obtain a current position of the gear train relative to a reference position of the gear train,
• b) obtain a current backlash value for the current position of the gear train from a data structure including a plurality of pairs of positions of the gear train and corresponding backlash values which have all been determined in an empirical manner for the actuator gear, the first gear and the second gear under control, which positions contained in the data structure are distributed along the entire work range of the actuator gear, and wherein the current backlash value is obtained by finding a position of the gear train in the data structure corresponding to the current position and thereby identifying the corresponding backlash value,
• c) determine a first backlash compensation for the first motor and a second backlash compensation for the second motor, wherein the first backlash compensation is based on a first component that includes the current backlash value with the sign of the first component being a function of a motor torque of the first motor and the second backlash compensation is based on a third component that includes the current backlash value with the sign of the third component being a function of a motor torque of the second motor, and
• d) control the first motor based on the first backlash compensation and controlling the second motor based on the second backlash compensation.

An industrial robot system comprising:

• an industrial robot,
• an actuator gear arranged to actuate the industrial robot,
• a first motor and a second motor,
• a first gear arranged to be driven by the first motor and a second gear arranged to be driven by the second motor, wherein the first gear and the second gear are mechanically connected in parallel with the actuator gear, and
• a controller system configured to control the first motor and the second motor having:
• a processing unit, and
• a storage unit containing computer code, wherein the computer code when run on the processing unit causes the controller system to:
• a) obtain a current position of the gear train relative to a reference position of the gear train,
• b) obtain a current backlash value for the current position of the gear train from a data structure Including a plurality of pairs of positions of the gear train and corresponding backlash values which have all been determined in an empirical manner for the actuator gear the first gear and the second gear under control, which positions contained in the data structure are distributed along the entire work range of the actuator gear, and wherein the current backlash value is obtained by finding a position of the gear train in the data structure corresponding to the current position and thereby identifying the corresponding backlash value.
• c) determine a first backlash compensation for the first motor and a second backlash compensation for the second motor wherein the first backlash compensation is based on a first component that includes the current backlash value with the sign of the first component being a function of a motor torque of the first motor and the second backlash compensation Is based on a third component being a function of a motor torque of the second motor, and
• d) control the first motor based on the first backlash compensation and controlling the second motor based on the second backlash compensation.