Research On Motion Control Method Of End Effector Of Cable-driven Parallel Mechanism

The moving target simulation device can make the target complete the expected trajectory movement,simulate the movement of target speed change,turning and turning around,and provide a practical test means for detecting the tracking performance of tracking equipment.The traditional motion simulator uses a twodimensional motion platform to realize the target motion through two-axis interpolation.This structure is suitable for indoor and the motion speed is slow.Using cable-driven parallel mechanism to realize motion target simulation can make the motion simulator have the advantages of large workspace,fast motion speed and simple structure.The research on the motion performance and control method of rope traction parallel mechanism has important engineering application value for the development of high-speed moving target simulation device.In this thesis,the cable-driven parallel mechanism was applied to the design of motion simulator,and the simulation model of cable-driven parallel mechanism was established.Through the trajectory planning and motion simulation of end effector,the motion control system of cable-driven parallel mechanism was developed,and the control of the end effector was realized.The experimental prototype was used for experimental verification.The main research work and results were as follows:(1)The kinematics and dynamics of cable-driven parallel mechanism was studied,and the joint simulation model of Adams-Matlab was established.According to the structural design of the cable-driven parallel mechanism,the kinematic model of the rope driven parallel mechanism was established by means of the inverse solution method.The relationship between the end effector and the length of the rope was obtained.The dynamics of the cable-driven parallel mechanism was established by using the Newton Euler method.The optimal solution of the rope driving force required for the movement of the end effector was solved.Through the joint simulation model,the influence of nonlinear factors such as rope elastic deformation and pulley friction on the movement accuracy of the end effector was reflected.The calculation results of the mathematical model and the joint simulation model were compared.(2)The trajectory planning method was studied,and the trajectory planning of the end effector was completed.According to the requirements of motion planning of moving target simulation device,the principle of trajectory planning was given,and the planning methods of straight line,parabola and circle trajectory were studied.Aiming at the disadvantages of poor continuity of discrete trajectory planning and sudden change of motion speed in traditional interpolation method,the method of combining motion trajectory function with speed planning was studied.The speed curve of end effector was optimized,and the transition process between discrete planning points was improved.After optimization,the speed curve of linear motor is smooth,which reduces the impact and jitter caused by frequent start and stop;The motion track of the end effector is continuous and smooth,which shortens the running time.(3)According to the kinematic relationship of cable-driven parallel mechanism,the controller structure was designed.Using the principle of active disturbance rejection control,the linear motor position feedback control method was given,and the motion simulation of typical test trajectory was carried out.After the optimization of the control algorithm,the speed change curve of each linear motor is smoother,the fluctuation of the acceleration and tension curve of each linear motor is reduced,and the motion accuracy of the end effector is improved.(4)Aiming at the experimental prototype of cable-driven parallel mechanism,the end effector control system was developed,and the experimental verification was completed.The control program was developed based on Twin CAT 3 platform,and the motion trajectory of the end effector was recorded by high-speed camera.The designed control system has the advantages of strong computing ability,good expansibility,fast response speed and so on,and can realize the motion control experiment of various trajectories of the end effector.