Research On The Fully Active Redundant Orientation Mechanism Of A Master Manipulator For Minimally Invasive Surgery

In recent years, robotic minimally invasive surgery has been used in a wide range of industries because of short recovery time, high-quality operation, etc. The master manipulator as the connector which delivers doctors’ surgery operation to the slave surgical instrument in the minimally invasive surgical robotic system, is required to be flexible enough to reflect doctors’ motions. The flexibility of the master manipulator is mainly decided mainly by its orientation mechanism. The master manipulator with low flexibility causes difficulty in performing complex surgery, and thus the quality of surgery is reduced severely. Therefore, it is of great significance to do research on high performance of the orientation mechanism of a master manipulator.According to the requirements of the orientation mechanism of a master manipulator in minimally invasive surgery, the advantages and disadvantages of different mechanisms are analyzed and the serial 4R redundant orientation mechanism is adopted. In order to decouple the master manipulator, the axes of the redundant orientation mechanism of a master manipulator(ROMMM) intersect at one point. The forward kinematics of the ROMMM is obtained according to D-H notation. The Jacobian matrix of the ROMMM is established through differential transformation. Analyses of the singularity and workspace of the ROMMM are carried out. Considering the dexterity index as the objective function, the optimization of the ROMMM is conducted to improve the operational performance of the ROMMM based on simulated annealing algorithm. The specific structure design of each part is completed. At the same time, the stiffness analysis of the ROMMM is carried out based on the finite element method.The self-balancing issue of the ROMMM is analyzed and a methodology of combining counterweight and motor torque to achieve self-balancing is proposed. The Lagrange method is applied to establish a self-balancing model and the relationships of the required motor output torque and master manipulator posture are obtained. Simulations are carried out to validate theoretical method. In order to reduce the inertia and the required motor driving torque for balancing, parameters of counterweight are optimized.Finally, the control system software and hardware of the ROMMM are designed and experimental platform is established. By zero calibration experiments, the relationship between mechanical zero position and the global coordinate is obtained. Self-balancing algorithm parameters are calibrated, which improves the accuracy of self-balancing algorithm model greatly. Based on self-balancing experiments, the capability of achieving self-balance in any posture is verified. A master-slave teleoperation experiment platform is established and the feasibility of the ROMMM applied in the master-slave surgery is verified.