In minimally invasive surgery applications, the use of robotic manipulators is becoming more and more common to enhance the precision of the operations and post-operative processes. Such operations are often performed through an incision port (a pivot point) on the patient's body. Since the end-effector (the handled surgical tool) move about the pivot point, the manipulator has to move about a remote center of motion. In this study, a 3-degrees-of-freedom parallel mechanism with 2R1T (R: rotation, T: translation) remote center of motion capability is presented for minimally invasive surgery applications. First, its kinematic structure is introduced. Then, its kinematic analysis is carried out by using a simplified kinematic model which consists of three intersecting planes. Then the dimensional design is done for the desired workspace and a simulation test is carried out to verify the kinematic formulations. Finally, the prototype of the final design is presented.

Assistive robots in surgical applications should be gravity balanced due to safety considerations. This study presents a gravity balancing solution for a 3-degree-of-freedom parallel manipulator to be used as an endoscope navigation robot for transnasal minimal invasive surgery applications. The manipulator has a rather simple structure that allows individual balancing of the three legs in their respective planes of motion. First, sole counter-mass balancing is investigated, but it is seen that the extra mass amount is too much. Sole spring balancing is not considered as an option due to constructional complexity. A hybrid solution as a combination of counter-mass and spring balancing is devised. In the proposed solution, the masses on the distal links of a leg are balanced with counter-masses so that all masses are lumped to the link connected to the base of the manipulator. Hence the problem is simplified into the balancing of a pendulum. The necessary formulations are derived and numerical calculations demonstrate that the hybrid balancing yields a feasible solution.