Length conservative surgical instrument

A method of operating a surgical wrist that moves with at least N degrees of freedom, the method comprising:

• independently operating at least N+1 input controllers that are coupled to at least N+1 surgical cables to control motion of the surgical wrist;
• and
• conserving a length of the at least N+1 surgical cables between pairs of the at least N+1 input controllers that are coupled by a reciprocal structure, wherein independently operating the at least N+1 input controllers causes motion of the surgical wrist and creates an inverse motion in the reciprocal structure to conserve the length of the at least N+1 surgical cables between pairs of the at least N+1 input controllers.

A method of operating a surgical instrument having a surgical wrist that moves with at least N degrees of freedom, the method comprising:

• in an attached mode where the surgical instrument is attached to a robotic arm, operating at least N+1 input controllers that are coupled to the surgical wrist via first cabling to control motion of the surgical wrist;
• and,
• in a detached mode where the surgical instrument is detached from the robotic arm, maintaining cable lengths in the first cabling via motion of a structure in the surgical instrument that is coupled to the at least N+1 input controllers via second cabling distinct from the first cabling.