CONTROLLING A SURGICAL INSTRUMENT

A control system configured to control manipulation of a surgical instrument in response to manipulation of a remote surgeon input device. The surgical instrument comprises an end effector having opposable first and second end effector elements connected to a shaft by an articulated coupling. The control system receives a command from the surgeon input device to both (i) change the orientation of the end effector, and (ii) open the first and second end effector elements relative to each other. In response to the command to change the orientation of the end effector, the control system determines an angle θ between the longitudinal axis of the articulated coupling and the end effector. In response to the command to open the first and second end effector elements, the control system determines an opening angle ϕ between the first and second end effector elements. The control system compares θ to a maximum angle θmax between the longitudinal axis of the articulated coupling and the end effector, and if θ>θmax, drives the first and second end effector elements to rotate such that (i) the angle between the longitudinal axis of the articulated coupling and the end effector is θmax, and (ii) the opening angle between the first and second end effector elements is ϕ.