Method of controlling a robot arm based on adaptive friction

A robot system comprising:

• a controller;
• a robotic arm controlled by the controller, the robotic robot arm comprising joints connecting a base and a tool flange, where at least one of the joints is a rotational joint comprising a joint motor having a motor axle, where the motor axle is configured to rotate an output axle of the rotational joint via a joint transmission;
• wherein controller comprises:
• an adaptive friction module configured to determine a friction torque of at least one of an input side of the joint transmission or an output side of the joint transmission based on at least two of:
• an angular position of the motor axle;
• an angular position of the output axle;
• or
• a motor torque provided to the motor axle by the joint motor;
• a transmission torque module configured to determine a robot joint transmission torque between the input side and the output side of the joint transmission based on at least one of:
• the angular position of said output axle;
• the angular position of the output axle and the angular position of the motor axle;
• or
• the angular position of the motor axle and the motor torque provided to the motor axle by the joint motor;
• and
• wherein the said controller is configured to generate a motor control signal based on the friction torque of at least one of the input side or the output side of the joint transmission and the robot joint transmission torque between the input side and the output side of the joint transmission, and (ii) to control the robotic arm by providing the motor control signal to the joint motor.