Controlling movement of a surgical robot arm

An arm controller for a surgical robot arm, the surgical robot arm forming part of a surgical robotic system comprising a remote surgeon console, a central controller and the surgical robot arm, the surgical robot arm comprising a series of joints extending from a base to a terminal end for attaching to an articulated surgical instrument, the arm controller being co-located with the surgical robot arm and configured to:

• receive a desired wrist position of a wrist of the surgical robot arm, and desired instrument drive joint positions for those joints of the surgical robot arm which drive joints of the articulated surgical instrument;
• and
• for the remaining joints of the surgical robot arm, determine joint positions so as to cause the wrist of the surgical robot arm to adopt the desired wrist position, the remaining joints of the surgical robot arm being those which do not drive joints of the articulated surgical instrument;
• and
• send control signals to joint controllers of the surgical robot arm to drive the joints of the surgical robot arm to the desired instrument drive joint positions and the determined joint positions.

A surgical robotic system comprising:

• a surgical robot arm comprising:
• a series of joints extending from a base to a terminal end for attaching to an articulated surgical instrument;
• and
• an arm controller co-located with the surgical robot arm;
• a remote surgeon console comprising a surgeon input device;
• and
• a central controller communicatively coupled to the remote surgeon console and the arm controller of the surgical robot arm, the central controller configured to:
• receive a command from the surgeon input device indicating a desired position of a distal end of the surgical instrument;
• transform that desired position of the distal end to (i) a desired wrist position of a wrist of the surgical robot arm, and (ii) desired instrument drive joint positions for those joints of the surgical robot arm which drive joints of the articulated surgical instrument;
• transmit the desired wrist position and desired instrument drive joint positions to the arm controller;
• and
• the arm controller configured to:
• receive the desired wrist position and desired instrument drive joint positions;
• and
• for the remaining joints of the surgical robot arm, determine joint positions so as to cause the wrist of the surgical robot arm to adopt the desired wrist position, the remaining joints of the surgical robot arm being those which do not drive joints of the articulated surgical instrument;
• and
• drive the joints of the surgical robot arm to the received desired joint positions and the determined joint positions.