Design And Research Of Electro-hydraulic Load Simulator Based On Variable Gain Sliding Mode Control

The electro-hydraulic load simulator is a kind of hardware in the loop simulator,which can simulate the complex loads in the real environment,and is suitable for the load simulation with high response,large load and high precision.It needs to track the real-time position and load the corresponding load spectrum according to the change of the loaded position,so it is a passive electro-hydraulic servo force control system with position disturbance.The electro-hydraulic load simulator has its own nonlinear link and parameter perturbation,and it is coupled with the position system,which requires that the high-performance electro-hydraulic load simulator can work synchronously with the position system,and is not interfered by the "forced" motion of the position system,its own nonlinear link and parameter perturbation.Sliding mode variable structure control can force the system to move according to the set "sliding" mode according to the current state of the system.In the sliding mode variable structure control,not only the sliding mode can be designed,but also the change of system parameters and external disturbance are invariant.Therefore,for the electro-hydraulic load simulator including serious nonlinear links,parameter perturbation and external disturbance,it has a unique advantage.In this paper,the electro-hydraulic load simulator is taken as the research object.Aiming at the loading accuracy and response speed of the passive electro-hydraulic servo force system,the sliding mode variable structure control method is adopted to make the system still have fast response speed and high precision under the condition of different position disturbance.The main work is as follows:(1)The working principle of the electro-hydraulic load simulator is described,and the nonlinear mathematical model of the whole system is established,including the cavity effect of the hydraulic cylinder and the nonlinear friction of the piston of the hydraulic cylinder.(2)For the electro-hydraulic load simulator,the conventional sliding mode variable structure controller based on pressure difference feedback,terminal sliding mode variable structure controller,fixed gain double power reaching law sliding mode variable structure controller and direct force feedback sliding mode variable structure controller combined with backstepping are designed.On this basis,the sliding mode variable structure controller with variable gain double power approach law and the backstepping sliding mode variable structure controller with disturbance observer are proposed,and the Lyapunov function is used to prove that the system is asymptotically stable.(3)In the Matlab/Simulink simulation software,the system simulation model is established,and the static and dynamic loading simulation is carried out for the system under different controllers.The simulation results show that the variable gain sliding mode variable structure controller can improve the loading accuracy of the system,reduce the disturbance of the position system to the load simulator and the output chattering of the controller,and has good robustness.The direct force feedback backstepping sliding mode variable structure controller can effectively reduce the influence of the piston rod friction of the hydraulic cylinder on the output force of the load simulator,improve the loading accuracy of the system,and the simulation results show that the system can still work normally under different quality.The inverse sliding mode variable structure control with disturbance observer is designed to reduce the influence of zero excursion of electro-hydraulic servo valve on the control accuracy of the system and further improve the output accuracy and robustness of the system.(4)According to the measurement and control design scheme and requirements of the electro-hydraulic load simulator,all kinds of hardware equipment in the measurement and control system are selected.Build the hardware platform of the load simulator,and write the sliding mode variable structure controller and different test programs on the LabVIEW platform to prepare for the next experiment.