Research On Robotic Manipulator Modeling And Constrained Motion Control For Minimally Invasive Surgery

With the development of technology,surgical robot has gradually become the focus of research,especially the robots used in minimally invasive surgery(MIS).There are many instability factors in manual MIS.For example,the surgeons will lead to muscle tremor if he/she operates the endoscope for a long time,which makes the visual field of endoscope unstable.In additi on,there are some disadvantages of uncoordinated communication and operation between surgeons and assistants.Therefore,design a stable and efficient surgical robot have gradually become the focus of research,especially robots which are used in minimally invasive robotic surgeries.However,most of surgical robots are specialized surgical robots.The costs of designing and constructing of such robotic system are very high,and it has a long development cycle.The universal manipulator with high accuracy and compact structure is a good choice for the planform used in the MIS.Therefore,this paper conducts research on how to achieve medical surgery based on an universal robotic manipulator automatically.In order to comprehend the differences between a dedicated surgical robot and the universal robotic manipulator,this article analyzes the characteristics of the mechanism based on an existing dedicated surgical robot.In the surgical scene,a method of using an universal robotic manipulator instead of a dedicated surgical robot to achieve a surgical endoscopic operation was test and verified.This paper analyzes the kinematics models for robotic endoscope holder(REH),and obtains the constraints imposed on the robots in minimally inv asive surgical scenarios.At the same time,the kinematics model of the universal robot arm is analyzed,and based on this kinematics model,the position of trocar which restricts the end-effector of universal manipulator can be estimated without t he utilization of external sensors if the joint angle information of the universal robotic arm is given.According to the kinematics model of the robot and the position of the trocar,two constraint model can obtain based on two cases that the remote center of motion is fixed in space and periodically changes with time.Then,the constraint motion equation determined by the constraint model is used to realize the speed control and trajectory planning of the end point in the manipulator tool.The feasibility of the constraint control is p roved by MATLAB.During the operation,the REH needs to be constantly operated to adjust the endoscope.And only the image information of the endoscope can be obtained.In response to this problem,this paper proposes an image-based visual servo controller to track the surgical instrument under the field of endoscope in real time,and adjust the field of view so that the surgical instrument can always be seen in a good view.In the end,a simple experiment was set up on an universal robotic arm,and the constrained movement of the endoscope in the minimally invasive surgery scene was successfully achieved.