Control System Design Of A Mri-compatible Pneumatic Needle Insertion Robot

This dissertation takes the control system of the magnetic resonance imaging (MRI) guided prostate needle insertion robot as the research object. The control system of the robot is developed and the position servo control of the pneumatic cylinder which actuates the robot is researched. The main contents contain the selection of the control system hardware and the design of the software, the mathematical model construction of pneumatic cylinder position servo system, the design of the fuzzy sliding-mode controller and so on. The stability of the controller is researched through system simulation. Combined with the needle insertion experiment on soft-tissue, the performance of the control system and the controller is verified. The achieved results are described as below:Firstly, according to the requirement of MRI compatibility, the difficulties and the solutions of the control system design of the MRI compatible robot are summarized. The scheme that the control system is put outside the MRI room is chosen. The hardware of the control system is chosen and the related software system is designed. The design of the pneumatic system is achieved, the pneumatic control circuit and the pneumatic components are chosen. At last, the control system which contains long pneumatic tube and signal transmission line is constructed based on the determined scheme.Secondly, the PWM controlled pneumatic cylinder position servo control system scheme which controlled by on/off valves is determined. The average method is used to construct the system mathematical model which contains the models of the cylinder load system, fluid system in the chamber of the cylinder, on/off valve and the long pneumatic tube. The fuzzy sliding-mode controller which contains the parameter of the thickness of the boundary layer is designed based on the proposed model.Finally, the simulation model is constructed. The performance of the controller is researched by simulation. The simulation results that the fuzzy sliding-mode controller has high stability to the parameter variation of the length of the pneumatic tube and the load and the fuzzy controller effectively decreases the system chattering are obtained. Experiments of pneumatic cylinder servo control and needle insertion on soft-tissue are put out to verify the performance of control system. The research results of this dissertation have high theoretical significance and application value. In design of the control system of MRI guided surgical robot and the research and application of the pneumatic cylinder servo system with long pneumatic tube, the research results have a certain exploratory significance. The results also lay good foundations for the system experiments in the MRI environment.