Mechanical Design of a 4DOF Minimally Invasive Surgical Instrument In order to meet design requirements in minimally invasive surgery (MIS), it is necessary to conduct basic operations in the narrow working space. Taking a grasper for example, a 4DOF MIS instrument driven by servo motors and transmitted by cables is designed. The design of the end of surgical instrument driven by cables is suitable for longdistance transmission, which improves dexterity of the surgical instrument working in narrow space. The mechanism principle including the wrist, graspers and shaft rolling are described. Kinematic coupling between the wrist and grasper are analyzed. Prototype of the surgical instrument is presented. This instrument prototype can be applied in most MIS operations.

Design Strategy for a Surgical Manipulator based on a Compliant Mechanism : Rigidity and Range of Motion: Finding the Optimized Balance Compliant mechanisms have drawn the attention recently in developing surgical robotic manipulators for minimally invasive surgery (MIS) owing to their capabilities in making miniaturized, simple, dexterous mechanical structures. Robotically assisted MIS demands instruments with higher precision, higher output force and a higher range of motion (ROM) for better performances. On the other hand, because of the behaviour of the elastic elements, compromising these factors is challenging. In a compliant mechanism, the rigidity of the elastic element determines the precision and output force. In this paper, we study the behaviour of rigidity and the ROM of elastic elements using previously developed surgical robotic forceps based on a compliant mechanism. To tackle this problem, we studied the variation of ROM of the compliant mechanism at different rigidity values of the compliant structure by changing its thickness. The results showed the linear relationship between the ROM and the rigidity of a compliant mechanical manipulator, suggesting the optimized balance point in this tradeoff.