| Robotic minimally invasive surgery(MIS)not only inherits the advantages of traditional minimally invasive surgery,such as small wound,less pain and quick recovery,but also provides more flexible and precise operation to overcome hand-eye incoordination and alleviate surgeon's fatigue.As an interface between surgeons and MIS robot,the force feedback manipulator transfers the surgeon's action to the slave robot to complete the operation meanwhile it reflects the interaction force back to the surgeon.The performance of the force feedback manipulator directly affects the overall performance of MIS robot,and then affects the safety and reliability of the surgical operation.This thesis focuses on researches about the design and optimization of force feedback manipulator in minimally invasive surgical robot system,singularity avoidance and gravity friction compensation of force feedback manipulator,force feedback control strategy,master-slave control experiments of MIS robot.According to the characteristics of MIS robot,a special force feedback manipulator is developed.In order to reduce whole inertia,the position output arm mechanism adopts a parallelogram to move the driving device forward.The orientation output wrist mechanism adopts redundant active joint to improve manipulability.Usually,the control cycle of force feedback manipulator and MIS robot reaches thousands of Hz.Aiming at real-time control requirement of force feedback manipulator,a control system architecture based on high-speed real-time bus is selected.This realizes the control algorithm of force feedback manipulator to centralized calculating and to distributed processing of joint motor.The advantage of the control system architecture is that the slave manipulators can be easily extended and integrated into the system.The master and slave manipulators is mounted on the same bus,which guarantees the real-time performance of master-slave control.The forward and inverse kinematics model of the force feedback manipulator are established.Aiming at the dexterity workspace requirement,the average and volatility of the Jacobian condition number are used to optimize the linkage length of force feedback master.The manipulability distribution of expected workspace is determined.The workspace interior singularity is determined by using block Jacobian matrix of the force feedback master.To improve the complexity and inefficiency of the gradient projection type singular avoidance method s,the practical wrist mechanism singularity avoidance planning is carried out by using the optimal manipulability of initial orientation configuration combined with penalty function.The singularity of wrist joints can be avoided in the process of surgeon's operation,which improves the manipulability and comfort of force feedback manipulator.In view of the fact that each linkage gravity of the force feedback manipulator and joint friction torque between drive chain are the main manipulating obstruction,When the surgeon grasp the force feedback manipulator performing minimally invasive surgery.That makes the surgeon easily fatigue and affects the comfort and safety during manipulation.Based on the principle of virtual displacement,a gravity compensation model of the force feedback manipulator is established.The gravity model is validated by Adams.An improved Stribeck friction compensation model is proposed,and the friction parameters of each joint is identified.Then model based feedforward gravity compensation and friction compensation are adopted.In view of the extremely complex characteristics of the dynamic s of the seven DOF force feedback master,the dynamics model is appropriately simplified.The dynamics of the force feedback master is established by Lagrange method and is verified by using Adams.According to the linearization of the robotic dynamics model,the force feedback master dynamics is linearized and decomposed.In order to solve the problem of inaccurate parameters in direct measurement of dynamic parameters without considering friction effect,an optimized finite Fourier series trajectory was used to identify the dynamic parameters of the force feedback master.To overcome the shortcomings of open loop impedance control,which neglects the dynamic effects,such as inertia force,Gothic force and friction force,a closed loop impedance control strategy is implemented to improve the froce feedback control.The performance experiments of force feedback manipulator and master-slave control integrated experiments of MIS robot are studied.The accuracy measurement experiment,redundant wrist singularity avoidance experiment,gravity and friction compensation experiment and force feedback experiment of force feedback manipulator are carried out.The results indicates that the force feedback master meets the design specifications.Combined with slave manipulators,the MIS robot platform is constructed.Base on the funciton requirements of master-slave hand eye coordination control,the comprehensive master-slave control experiments are carried out.The master-slave orientation alignment experiment,master-slave control ring-rod sliding movement experiment,master-slave following analysis,and master-slave control ring movement under laparoscope experiment verify the funciton of the force feedback manipulator.All the experimental results show that the force feedback master can meet the manipulation requirements of the MIS robot,reducing the operation time,improving efficiency and safety of the surgical operation,enhancing the surgeon's manipulation feeling. |
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