Research On Key Technologies About A Medical Robot For Celiac Minimally Invasive Surgery

Minimally invasive surgery (MIS) has been widely adopted all over the world forits no opening, small incisions, less pain and quicker recovery. However, thedisadvantages existed in conventional MIS impede the expansion of MIS. For example,the bad hand-eye coordination affects surgeon operation; surgeon can be easilyexhausted for long time holding the instrument in MIS; and the hand tremor has anegative effect on the operation precise. Fortunately, these problems can be overcomethrough the use of robot assistance, which is also helpful for improving the surgeryconditions and quality. In this paper a novel medical robot is presented for celiac MIS,specific details are as follows:The mechanism design and the control subsystem of the robot are studied. Basedon the characteristic of the celiac MIS, configuration for the robot is established, therobot is composed of a robot cart and surgical instruments, the surgical instruments aremounted on the robotic arms to carry on the operation. According to the requirementsof the celiac MIS, the robot cart and surgical instruments are designed in detail, thelength of the robotic arm is optimized and the structural performance of the surgicalinstrument is validated by simulation. Besides, based on the working feature of therobot, the control subsystem is designed, which includes the hardware subsystem andthe software subsystem. And the safety measures for the robot are taken intoconsideration from the mechanical and control aspects.The master-slave control of the robotic system is studied. According to theconfiguration of the master and robotic arm, the kinematic mapping relationshipsbetween the master and robotic arms are built, and the control strategy is provided,which is the combination of the Cartesian space control and joint space control. Basedon the robot working mode, the inverse kinematics solution is analyzed with themethods of equivalent differential equation and error compensation. In order toachieve the robot smoothness movement, the methods of cubic spline interpolation andmoving average filter are adopted for the trajectory planning and tremor filtration,respectively.The robotic arm joint control is studied. According to analyze the dynamiccharacteristic of the robot movement, the methods of gravity compensation and fuzzyPD control are combined to build the joint control strategy, and the joint controllerdesign is presented in detailed. And the performance of the joint controller is validatedwith simulation experiments.The robotic arms pose selection and port placement are studied for pre-operationplanning. As cholecystectomy is common celiac MIS, taken it as an example, the mathematical model is built for the incisions. According to the optimization purpose,objective optimization functions are established for three robotic arms configurationsetting, and the configuration setting of the positioning joints are analyzed with theGradient Projection Method, the setting for remote center of motion (RCM)mechanism are analyzed based on the location of the cholecyst. Based on the roboticarm configuration setting, the placement selection of the port is analyzed with theperformance index, and the effectiveness of the selected ports is validated bysimulation experiment.The robot system is integrated and a series of experiments are carried out to testthe robot performance. With the Optotark Centus system, which are used to acquiringthe position and posture information of the test specimen, the mechanical performanceof the RCM mechanism is tested, and the decoupling motion and the joint movementerror of the surgical instrument are also measured, which indicates the robotmechanical performance and operation accuracy meets the demands of the MIS.Besides, the biological tissue experiments simulated the cholecystectomy areconducted to validate the robot practical operation performance, and the experimentalresults proofed that the robot can well reproduce the surgeon hands movement andcomplete the surgical operation. Moreover, the in-vivo animal experiments areconducted and validated that the robot system can complete practical surgical task,which further validates the effectiveness of the robot system and lays the groundworkfor the next clinical application.