Research On Control Methods Of Typical Electro-hydraulic Servo Parallel System

Parallel robot has a broad application prospect because of its powerful working ability,such as large stiffness,high accuracy,fast response speed and strong carrying capacity.In this paper,the two degree of freedom parallel system and the six degree of freedom parallel system are taken as the research objects,and both of them are applied to the parallel machining equipment.The two degree of freedom parallel system is used for glass cutting,plane engraving and other Plane Machining Equipment.The six degree of freedom parallel system is used for High Difficult 3D Surface Machining Equipment and other Space Machining Equipment.Due to the nonlinear characteristics of the parallel system itself and the disturbance influence of uncertain factors,in order to improve the steady-state and dynamic performance of the system.PID control,sliding mode variable structure control and pole assignment control are used to control the two degree of freedom parallel system.The control performance of the controllers is comprehensively compared and analyzed through experiments,and a controller with the best control performance is obtained.The PID controller is used in the experiment of six degree of freedom parallel system.Because the system structure of it is more complex,the motion performance is analyzed.Firstly,the calculation of the degree of freedom is done for the two degree of freedom parallel system and the six degree of freedom parallel system.Because the two parallel systems have the same modeling ideas,the kinematics models of the two parallel systems are established on the basis of generalized coordinates,and the inverse kinematics formulas of the two systems were deduced,which laid a foundation for the subsequent motion simulation.The positive position solution was carried out by using the Newton-Raphson iterative method.Then the dynamics model of the six-degree-of-freedom parallel system is derived by Newton-Euler method.Finally,the co-simulation of Amesim and Visual Studio is introduced,and the simulation experiment is done.Secondly,the mathematical model of the hydraulic drive system is established,and the transfer function is converted,and the state space expression is further derived,which is used for the design of the sliding mode variable structure controller and the design of the pole assignment controller.According to the characteristics of the three controllers: PID control,sliding mode variable structure control,and pole assignment control,different electro-hydraulic position servo system simulation models were built in Amesim,and the algorithms of the three controllers are programmed using C language.The co-simulation experiment verifies the correctness of the controller design.After that,the simulation model of the two degree of freedom parallel system was built in Amesim,and the inverse kinematics algorithm was used to realize the motion of the two degree of freedom parallel system,and the three controllers were applied to the two degree of freedom parallel system.Through a comprehensive comparative analysis of the controller's control accuracy,stability,tracking performance and anti-interference performance.It is concluded that the most suitable control method for a two-degree-of-freedom parallel system is sliding mode variable structure control.Finally,a six degree of freedom parallel system was built in Amesim,and the inverse kinematics algorithm was written in C language.The co-simulation was carried out,and the precise control of six degrees of freedom was realized successfully.