Robotic joint control

A joint velocity limiting system for limiting joint velocity of a plurality of joints of a surgical robotic system, the surgical robotic system comprising a robot having a base and an arm extending from the base to an attachment for an instrument, the arm comprising a plurality of joints whereby the configuration of the arm can be altered, the joint velocity limiting system being configured to:

• obtain joint states for a first group of k joints of the arm, where k>1;
• and
• for each of the k joints:
• determine from the obtained joint state a permitted range of motion for that joint;
• derive, using the permitted range of motion, a joint velocity limit for that joint;
• select the minimum joint velocity limit of the k joints to be a common joint velocity limit used to limit each of the k joints individually;
• calculate drive signals for driving the k joints to actuate at least one of the k joints wherein the velocity of each of the k joints is limited using the common joint velocity limit;
• and
• control the arm to actuate at least one of the k joints in response to the drive signals.

A non-transitory computer readable storage medium having stored thereon computer readable instructions that, when executed at a computer system, cause the computer system to perform a method for limiting joint velocity of a plurality of joints of a surgical robotic system, the surgical robotic system comprising a robot having a base and an arm extending from the base to an attachment for an instrument, the arm comprising a plurality of joints whereby the configuration of the arm can be altered, the method comprising:

• obtaining joint states for a first group of k joints of the arm, where k>1;
• and
• for each of the k joints:
• determining from the obtained joint state a permitted range of motion for that joint;
• deriving, using the permitted range of motion, a joint velocity limit for that joint;
• selecting the minimum joint velocity limit of the k joints to be a common joint velocity limit used to limit each of the k joints individually;
• calculating drive signals for driving the k joints to actuate at least one of the k joints wherein the velocity of each of the k joints is limited using the common joint velocity limit;
• and
• controlling the arm to actuate at least one of the k joints in response to the drive signals.