Integrative Design And Performance Analysis Of Passive Joint For Robotic Minimally Invasive Surgery System

Robot assisted Minimally Invasive Surgery (MIS) has great advantages onthe operation process, which made the study in "minimally invasive Robotsystem for surgery" widely spread in the world. In the development of Robot forMIS, domestic and foreign research institutions have taken many kinds ofmeasures to ensure the operation safety. Meanwhile, to improve the convenienceand reliability，as well as reduce the volume of the robot, research of theintegrated redundant endoscope arm has become a new hot direction. Belongingto "Research on minimally invasive Robot for laparoscopic surgery" from the"863" project of China, this paper has designed a kind of passive joint for theMIS surgery robot, which realized the integration of mechanical structure，control component and driver. The joint can realize the rotary motion andlocking in any position during operation reliably. The locking mechanism isdriven by stepping motor. A force sensor is used to detect the locking torquewhich is adjustable.Based on the thinking of integration design, this paper designs a passivejoint of minimally invasive Robot for laparoscopic surgery, which includes themechanical structure, sensor devices and control units integrated in the joint.Having analyzed the MIS operation requirements of the passive joint, we put up5criterions for the designing of passive joint. According to the criterions, wedesign the passive joint with reliable locking mechanism, make the selectioncalculation of the components inside the joints and check the strength of keycomponents. What’s more, we designed the locking mechanism control unit andthe joint angle observation circuit based on AVR Micro Controller Unit.Then, according to the structure features of passive joint locking mechanism,this paper analyzed the performance of locking with the theory of elasticmechanics and the finite element simulation software. After the analysis of thetheories related to friction and contact, we establish the mathematicalrelationship of joint friction block contact stress and its key parameters, by usingthe solution method of contact problem based on elasticity theory. And weabstract the optimization model with mathematical optimization method, and gotthe optimization result with MATLAB. Based on that, we simulated the contactcondition of locking part with the contact module of ANSYS.At the end, the paper certificated the relating parameters and conclusions ofthe designing process of passive joint by experiments. At first, we use the Zwickelectronic tensile testing machine to finish the input output calibration of sensor and its control circuit. Then, we verified the performance of the passive joint ofMIS robot with experiments, including joint load experiments, control unit andthe locking performance experiments.