| In recent years,the contradiction between the number of ophthalmic diseases and the number of ophthalmologists has been increasing,and the master-slave control ophthalmic surgical robot combined with the rich clinical experience of doctors has gradually become a research hotspot.This thesis takes the master-slave 6-PSS parallel actuator as the research object,and focuses on some key technologies applied to ophthalmic surgical robots,including actuator kinematics modeling,workspace analysis,structural optimization,micro-force perception and tactile transmission,etc.The specific research contents are as follows:1.The kinematics model of 6-PSS parallel actuator is established.The inverse kinematics model of the master actuator is established by the space closed-loop vector method.Aiming at the problems that Newton’s method to find the positive solution of parallel actuators has a large amount of calculation and the convergence of the solution is easily affected by the initial value of iteration,the forward kinematics model of the actuator is established by combining BP neural network and Newton’s method.And the Jacobian matrix of the master actuator is obtained in the speed loop.Finally,the correctness of the forward and inverse kinematic models and Jacobian matrix is verified by simulation.2.Aiming at the shortcomings of low search efficiency in the traditional polar coordinate search algorithm to find the working space boundary of parallel actuators,a fast polar coordinate search algorithm based on dichotomy is proposed.The idea of finding function zero by dichotomy is applied to find the boundary of actuator workspace,which reduces the time complexity of the algorithm.The position workspace,attitude workspace and reachable workspace of the master actuator are analyzed by using the fast polar coordinate search algorithm based on dichotomy.3.In order to meet the requirements of the slave actuator’s workspace and the output capacity of the motor,the multi-objective optimization of the slave actuator is carried out using multi-body dynamics software.On the basis of creating design variables,the parametric model of the slave actuator is established by using the method of parameterized key points,and the objective function and constraint function of the actuator are created.On this basis,the relationship between different design variables and the objective function of the actuator is studied.Finally,the multi-objective optimization of the slave actuator is carried out by the linear weighted sum method,and the workspace of the actuator is quantitatively analyzed by the Monte Carlo method.The simulation results show that after optimization,the workspace of the actuator increases by 9.8%,and the mean value of the maximum driving force of the moving pair decreases by 6.5%.4.In order to realize the micro-force perception of the actuator without the force sensor,the gravity compensation method of the actuator is studied.The BP neural network is used to identify the gravity model of the actuator,and the interference of the actuator’s own gravity is actively compensated through feedforward.On this basis,the master-slave bilateral control of the 6-PSS parallel actuator is carried out by using a four-channel bilateral control algorithm based on disturbance observer and reaction force observer in joint space.Finally,the instruction tracking and tactile transmission experiments are carried out on the master-slave actuator.The experimental results show that the PD+BP neural network gravity compensation control can improve the tracking ability of instructions;the master-slave bilateral control based on the BP neural network gravity compensation can achieve good force-tactile perception and improve the transparency of the system.In summary,this thesis takes the 6-PSS parallel actuator as the research object,and conducts a systematic research on some key technologies of its application in ophthalmic surgical robots,laying a solid foundation for the application of parallel actuators in ophthalmic surgery. |
PDF Full Text Request