Research On The Remote Center Of Motion Mechanism And Force Perception For Minimally Invasive Surgery

Minimally invasive robot surgery(MIRS)is a new technology,which could overcome some disadvantages of traditional minimally invasive surgery(MIS),including the doctors' shaking hands and fatigue problems in operations,more and more widely used in the field of MIS.Despite the minimally invasive surgery robot has solved almost all of the technical problems,the lack of force sensing feedback of the operating system also exists potential safety hazard.Because of the special operation environments factors,it is hard to acquire the interaction force between surgical instruments and environment.In this paper,the remote center of motion(RCM)mechanism type and structure optimization has been made,and the kinetic and dynamic analysis is proposed.Based on the dynamic model of the mechanism,the force testing model is put forward,obtaining the interaction force between surgical instruments and environment without placing force sensors in the end of the instruments,which provide the theoretical basis.Firstly,this paper analyzes the operating procedures and operation requirements of MIS,and puts forward the compact RCM structure of the single parallelogram with steel strip.Then,the kinematic analysis of RCM mechanism is proposed,obtaining the attitude matrix of the end of the mechanism,and the operability of the mechanism is evaluated based on the jacobian matrix.A double objective optimization function based on the operability and workspace is presented,solved by using the particle swarm(PSO)algorithm,and obtain the better structure parameters with better performance in maneuverability and workspace.Then,the dynamic model of RCM mechanism is presented by using the Lagrangian approach,acquiring the relationship between the motion state of each joints and the joints torque.Firstly,this paper simulates the kinematic model of the mechanism,and obtain the position curve and velocity curve of the terminal.Then,the dynamic model is simulated based on the Adams simulation software,and the accuracy of the model is evaluated by comparing the theoretical value of Matlab and the simulation value.This paper also analyzes the proportion of the dynamic model by studying the proportion of each component of the dynamic model of each joints,then the gravity term in the dynamic model is validated,which lay the foundation of the subsequent force testing model.The force testing model is established,building the mapping relationship between the joint motor output torque and the terminal force of the surgical instruments,and further establish a more accurate dynamic model with friction.Linearize the dynamic mode and identify the dynamic parameters through the experiments on the basis of the principle of least square method.The accuracy of the model is verified through the experiments and data analysis.Finally,this paper proposes the experimental verification of the force testing model,including the no-load test,the clamping test and the animal tissues vitro experiments in three aspects,through the TwinCAT software implementation of the mechanical arm of the RCM mechanism.The no-load test and the clamping test is to verify the accuracy of the force testing model.The animal tissues vitro experiment is the use of the force testing model,in order to estimate the interacting force between the surgical instruments and the animal organs and tissues,realizing the application and the validation of the force testing model.