Research On High Pressure Pneumatic Launching Process Control

Regarding compressed air which has the properties of instantaneous expansion of strong,high power density as the working medium,High-pressure pneumatic launch technology with advantages of high power-to-mass ratio,clean,anti-fire,anti-explosion,anti-electromagnetic interference,low working fluid pressure,no thermal protection measures,good versatility and low cost,has good application prospect in missile launching field.However,the pneumatic system has many weaknesses which are not conducive to precise control,such as strong nonlinearity and model uncertainty.That how to improve the tracking control performance of pneumatic position servo system is still difficult.In this paper,the high-pressure pneumatic control system is divided into high-pressure pneumatic subsystem and hydraulic position control subsystem.The high pressure pneumatic subsystem consist of gas source,valve,cylinder and other components,in order to obtain the ideal valve flow area,a high performance position control strategy is designed for the high pressure pneumatic subsystem.Including the hydraulic cylinder,servo valve,oil and other components,the hydraulic servo subsystem is used to realize the precise tracking control of spool displacement.Through the ideal valve flow area by the aerodynamic control subsystem theory simulation,design the desired position of the hydraulic position control subsystem;control the valve spool according to the preset trajectory movement,complete high-pressure pneumatic ejection process.The goal of this paper is to realize high pressure pneumatic control;the research of high precision trajectory tracking control of hydraulic servo system that drives the valve spool motion is the key.Based on the nonlinear model which describes the characteristics of the system,the pneumatic loading control strategy and the hydraulic servo position control strategy are deeply studied by means of the combination of theoretical analysis and experiment.(1)A complete nonlinear model of the high-pressure pneumatic system is established for the pneumatic control subsystem of the launchers.Considering that the properties of the high-pressure gas have deviated from the ideal state,the modified Ville equation is used to modify the ideal gas state equation.Based on the modified gas state equation,a more realistic dynamic equation of pressure is derived.For the uncertainties(parametric uncertainties and uncertain nonlinearities)in the pneumatic loading system,a nonlinear controller based the integral of sign of the error for pneumatic servo system is designed.In addition,in order to improve the transient performance of the control system,a prescribe performance control method is proposed to impose constraints on the transient performance of the system,ensuring the steady-state performance and transient performance of the system.The effectiveness of the controller is verified by simulation.(2)A complete nonlinear model of the hydraulic servo system is established for the hydraulic position servo subsystem of the launchers.The main problems of position control of hydraulic servo system are described.For the uncertainties of the hydraulic servo system,a feedback nonlinear robust control strategy with disturbance compensation is designed.The controller consists of a finite time disturbance observer and a nonlinear robust controller based on the backstepping method.The on-line disturbance estimations are used to compensate for the uncertainties of the system,and the robust feedback is used to ensure the stability of the system and high tracking accuracy.Finally,the effectiveness of the controller is verified by the comparison experiment of different working conditions.(3)For the existence of the velocity signal measurement noise in the experiment,a feedback nonlinear robust control strategy based on extended state observer is designed.Through the on-line estimation and real-time compensation of velocity state and disturbance,it is possible to reduce the influence of the uncertainties on the control performance of the controller while suppressing the serious noise that the speed signal may introduce into the system.(4)Due to the presence of the dead zone in the valve,the initial position of the hydraulic position servo system that drives the valve opening and closing is mismatched,it is possible that the speed or acceleration is too large and the position control accuracy of the hydraulic system is reduced and affecting the control accuracy.In this paper,the motion tracking control of hydraulic system based on full state constraint is studied.Based on the barrier Lyapunov function,considering the interference compensation and noise suppression,the full state constraint control strategy is designed.Finally,the effectiveness of the control strategy is verified by experiments.(5)According to the actual working conditions,the prototype of the launcher is designed.Based on the related control problems and different technical difficulties,the reasonable experimental scheme is designed.The validity of the system model and the effectiveness of the control strategy are verified by the hydraulic position tracking curve and the missile launch displacement curve and the launch velocity.