Research On Connection Stiffness Characteristics Of Electro-hydraulic Load Simulator And Its Influence On Control Performance

The passive electro-hydraulic load simulator is primarily applied to reproduce and simulate the air force/torque load of the aircraft navigation gear in the actual flight under laboratory conditions.As the performance index of aircraft steering gear becomes more and more demanding,the loading precision and response speed of passive electro-hydraulic load simulator are also improved.Therefore,research on passive electro-hydraulic load simulator has important significance for technological progress in fields such as national defense.During the operation of the passive electro-hydraulic load simulator,the steering gear system simulates the motion state of the steering gear in the actual flight process,and the loading system simulates the aerodynamic force/moment of the steering gear.Ideally,the loading system moves with the steering gear system,but in practice,the loading system does not always move with the steering gear system.When the servo system is out of sync with the loading system,the active motion of the servo system will drag the loading system,resulting in forced flow in the hydraulic actuator cavity of the loading system.The force/moment output by the system under the action of forced flow is called extra force/moment.The extra force/moment causes a large deviation between the actual load force/moment and the expected load force/moment,which seriously affects the loading precision.Therefore,the suppression of surplus force/moment is an important step to improve the performance of passive electro-hydraulic load simulator.To this end,this paper mainly does the following research:Firstly,linear and nonlinear mathematical models of the passive electro-hydraulic load simulator are established.Usually,the parameters of the actual physical system are deviated from those of the theoretical model.In order to accurately identify the parameters of the actual physical system,a parameter identification law based on extended particle swarm optimization is designed.In order to improve the accuracy of parameter identification law,a parameter identification law based on backward step theory is designed.Considering the influence of measuring noise of torque sensor on parameter identification accuracy,a transverse filter based on LMS algorithm is designed to effectively filter the gaussian white noise.The simulation results show that the parameter identification law and the transverse filter can effectively realize their functions.Based on the constructed mathematical model,the effect of connection stiffness on the load moment and extra moment of passive electro-hydraulic load simulator was analyzed and a reasonable range of connection stiffness was given.An backstepping adaptive controller is designed and the system's intermediate variables are used as control inputs and outputs to design the controller for each subsystem.The controller of each subsystem is recursive to the controller of the entire system,but at the same time,considering the possible changes in system parameters,the corresponding adaptive law is described.We propose the conclusion of the parameter optimization of the backstepping controller with the cumulative error and the error convergence speed as the optimization indices.The controller was simulated and validated.Simulation results show that the backstepping controller can effectively improve the performance of passive electro-hydraulic load simulator.