Research On The Modeling And Control Of The Main Manipulator With Six Degrees Of Freedom

The master manipulator is the carrier that connects the master manipulator and the slave manipulator in the master-slave medical surgical robot and its performance has an important influence on the working effect of the master-slave system.During the operation,the gravity of the master manipulator increases the driving force provided by the operator,which makes the operator easy to fatigue,afifects the stability and the operation accuracy of the robot system,and increases the operation difficulty.The positioning accuracy of the master manipulator will also have a great impact on the performance of the whole system.In view of the above problems,a master manipulator with self-weight balance performance was designed in this paper.The modeling and control strategy of the master manipulator were studied.The experimental platform was built and the experiments were carried out.The main research contents of the paper are as follows:Firstly,according to the characteristics and requirements of the master-slave robotic system,a six-degree-of-freedom master manipulator was designed by using SolidWorks.The master manipulator has three position degrees of freedom and three attitude degrees of freedom.In order to achieve the clamping function,the end operator has opening and closing degree of freedom.The two position degrees of freedom are provided by a parallelogram mechanism.The parallelogram mechanism is placed horizontally so the mechanism does not need to be provided additional gravity compensation.The gravity of other joint mechanisms are compensated by using balance weight and motors.Secondly,the kinematics and the dynamics models of the master manipulator were carried out,and the inverse kinematics and Jacobian matrix were solved.The performances of the master manipulator were evaluated by using the operability and the dexterity indexes based on the Jacobian matrix.The dynamics model of master manipulator was simulated by using the Motion module of SolidWorks,and the joint friction model was modelled.In order to achieve the gravity balance of the master operator,based on the dynamics and friction models of the master manipulator,a gravity compensation strategy was proposed.Finally,an experimental platform was built to analyze the performance of the master manipulator.To improve the position accuracy of the master manipulator,the kinematics error model of the master manipulator was established by using screw theory on the basis of the analysis of kinematics.And the kinematics parameters were identified by the least squares method.Based on the established experimental platform,the calibration experiment of kinematics parameters was carried out.The experimental results show that the position accuracy of the master manipulator was improved by 67.43%after calibration of the kinematic parameters.The experimental results show that after gravity compensation,the master manipulator can reach the balance in the working space,and the gravity compensation effect was better.