Abstract: A controller for controlling the configuration of a joint in a surgical robot, the joint being driven by a drivetrain which transfers power from a drive source to the joint, wherein the controller is configured to: receive a first input indicating a configuration of the drive source; receive a second input from a first sensor, the second input indicating a measured configuration of the joint in the surgical robot; calculate a value of output torque about the joint using the first input and the second input; and calculate, using the value of output torque, a value of input torque to be applied to the joint in the surgical robot by the drive source.

Abstract: A method for characterising the performance of a joint in a surgical robotic arm, the joint being driven by a drivetrain which transfers power from a drive source to the joint, the method comprising: sending a first command signal to position the robot arm into an initial configuration; sending a second command signal to apply a force to the joint to displace the joint from a steady state; for a plurality of predefined time intervals: receiving a first measurement indicating the configuration of the drive source at a first end of the drivetrain; receiving a second measurement indicating the configuration of the joint at a second end of the drivetrain; calculating a value of elongation using the first and second measurements; and receiving a third measurement indicating the torque experienced by the joint at the second end of the drivetrain; comparing the values of elongation with corresponding values of torque at each of the predefined time intervals; and generating an output from the comparison indicating th