Drive assembly interface

A surgical robot arm extending between a base and a terminal link, the terminal link being connected to an adjacent link in the surgical robot arm by a joint which permits the terminal link to rotate about a longitudinal axis of the terminal link and being configured to interface with a robotic surgical instrument such that a longitudinal axis of a shaft of the robotic surgical instrument is coincident with the longitudinal axis of the terminal link, wherein the terminal link comprises:

• a drive assembly comprising a plurality of drive assembly interface elements configured to drive a plurality of instrument interface elements of the robotic surgical instrument when the surgical robot arm engages the robotic surgical instrument, the drive assembly comprising;
• a first drive assembly interface element being engageable with a first instrument interface element on the longitudinal axis of the terminal link and linearly displaceable along the longitudinal axis of the terminal link so as to drive the first instrument interface element along the longitudinal axis of the terminal link;
• a second drive assembly interface element being engageable with a second instrument interface element along a second axis so as to drive the second instrument interface element along the second axis;
• and
• a third drive assembly interface element being engageable with a third instrument interface element and linearly displaceable along a third axis so as to drive the third instrument interface element along the third axis,
• wherein the first, second and third drive assembly interface elements are independently driveable to thereby independently drive the respective first, second and third instrument interface elements along their respective axes.