Design And Optimization Of The Active Arm Mechanism Of Minimally Invasive Surgery Robot

The minimally invasive surgical robotic active manipulator which includes the remote center of motion mechanism and the surgical instruments is a key component of the minimally invasive surgical robotic system. The design of the robotic active manipulator not only has a great impact on the performance of the minimally invasive surgical robot, but also restricts the development and design of other parts in the system. Supported by the National Science Foundation of China, the detailed structure design, kinematics analysis, performance optimization as well as simulation and experiment verification has been studied in this thesis.1. The structure design of the robotic active manipulatorThe structure of bending double parallelogram which provided space for the installation of the surgical instrument and the motors was adopted by the remote center of motion mechanism. The roll and pitch joints were directly driven. For the translational joint, the transmission of motor power was realized by the steel cable-driven system. The four degrees of freedom of the surgical instrument, rotation, pitch, deflection, as well as opening and closing, were also achieved by the steel cable-driven system, which can allow the power source to be installed away from the joint position and achieve no backlash under appropriate preload. The power transmission of motors was more stable and more accurate.2. The kinematic mapping relationship modelFor a kind of N degrees of freedom robotic system driven by 2N steel cables, the loop analysis method was put forwarded. Loop matrix and equivalent radius matrix of the motor-driven space can be written out by observing the layout of steel cables. Combined with the traditional robotic kinematics, the complete kinematic mapping relationship model between the motor-driven space and the Cartesian space was constructed, which speeds up and simplifies the kinematic modeling and analysis process of steel cable-driven robot. In addition, the Jacobian matrices of the remote center of motion mechanism and the surgical instrument were calculated, which has laid the foundation for the following performance optimization.3. The optimization analysis of the robotic active manipulatorBased on the kinematic analysis of the remote center of motion mechanism, the comprehensive evaluation index function on the basis of the global manipulability index and the uniformity of manipulability index was constructed. The geometric constraints were determined by the limiting positions of workspace and the cross section sizes. The dimension parameters of the mechanism were optimized by Genetic Algorithm and the finite element analysis. Worthwhile, the surgical instrument was also optimized by Genetic Algorithm and the above evaluation index function. Comp-ared with the previous, the overall manipulation performance of the robotic active manipulator was improved. The purpose of optimization was achieved.4. The simulation of the kinematic mapping relationship model and the physical operation experiment.The kinematic mapping relationship model between the motor-driven space and the Cartesian space was verified by the kinematic simulation analysis, which proves the loop analysis method is correct. In the physical operation experiment, for the remote center mechanism, the workspace and the remote movement center were validated. With regard to the surgical instrument, the experiments that include the four degrees of freedom motion, pipeline-gripping, body-gripping and suturing simulation operation were conducted. The whole experiment process showed that the robotic active manipulator could satisfy the requirements of the minimally invasive surgeries.