Patent ID: 8500722

Claim:
A method for a set-up arm of a robotic surgical system, the method comprising: balancing a linkage structure with a balancing mechanism to support a load, wherein the linkage structure includes a first set-up joint coupled to a supporting structure, a second set up joint adapted to couple to a robotic arm, and a counter balancing link pivotally coupled to the first set-up joint at a first pivot point and to the second set-up joint at a second pivot point, wherein the balancing mechanism has a plurality of pulleys including a first pulley rotatably coupled to the linkage structure at the first pivot point, a second pulley rotatably coupled to the first setup joint, and a third pulley rotatably coupled to the counter balancing link such that a distance from the second pulley varies as the counter balancing link pivots around the first pivot point; moving the linkage structure in a first direction thereby varying a moment at the first pivot point due to the load being near an end of the second set-up joint of the linkage structure; changing a path length of one or more cables over the plurality of pulleys in the balancing mechanism in response to the movement of the linkage structure in the first direction; and compressing a spring in response to the change in the path length to increase tension in the one or more cables to balance the variance in the moment.