Research On Anti-skid Braking Control Of Aircraft With Hydraulic System Vibration Constraint

Vibration instability of hydraulic servo system is an urgent problem to be solved in the design of aircraft brake system,as the core actuator of the brake system,vibration instability of hydraulic servo system may lead to serious accidents such as hydraulic pipeline rupture and aircraft fire.Aiming at the vibration instability of hydraulic servo system during aircraft braking,this thesis establishes a new three-stage jet tube servo valve fluid-structure interaction model,puts forward the practical stability analysis criterion of hydraulic servo system,designs the sensitivity constraint and robustness constraint of the control parameters,and completes the design of the robust self-learning PID anti-skid control law of aircraft brake based on the above constraints.In general,the research in this thesis is mainly divided into four parts: servo system model establishment,servo system parameter identification,constraint design based on practical stability analysis,and anti-slip control law design with constraints.The main contributions and research work of this thesis are as follows:(1)Aiming at the problem that the hydraulic servo system model cannot fully characterize the nonlinear dynamic behavior of the system in the design of the existing aircraft brake control system,considering the nonlinear characteristics of the internal components of the servo valve,such as ferromagnet hysteresis,spool displacement dead zone and saturation characteristics,a new three-stage jet tube electro-hydraulic servo valve nonlinear fluid-structure interaction vibration model is established,which overcomes the shortcomings that the traditional three-order linear model cannot describe the dynamic characteristics of the internal state of the servo system,and studies the occurrence mechanism of the instability and oscillation phenomenon of the hydraulic servo system during the aircraft braking process.And provides the model basis for vibration suppression control of aircraft brake hydraulic servo system.(2)Aiming at the problem that some parameters of the hydraulic servo system are difficult to obtain accurately,a quadrature filter error estimation algorithm with automatic selection mechanism is proposed.In order to eliminate the coupling between unknown parameters in the system identification process and improve the parameter identification accuracy,this thesis realizes the identification of key parameters of hydraulic servo system based on orthogonal nonlinear filter error algorithm.The experimental results show that the residual detection outlier of the orthogonal filter estimation with automatic selection mechanism proposed in this thesis is less than 2.8%,and the identification results have good credibility,which improves the accuracy of the hydraulic servo system model.(3)Aiming at the problem that Lyapunov stability theory is not suitable for describing the stability of strong real-time and strong nonlinear systems,a practical stability criterion for aircraft brake hydraulic servo system is proposed.Firstly,based on the phase diagram analysis method,the influence of external interference,brake cavity,oil return cavity volume and other factors on the nonlinear oscillation of the system is studied.Secondly,the practical stability criterion of servo system under disturbance state is proposed.In addition,based on the Koopman operator,the global linearization of the brake servo system model is carried out,and the vibration constraint of the brake servo system is designed according to the practical stability criterion,which provides a theoretical basis for the design of the protective brake control law of aircraft with vibration suppression.(4)Aiming at the problem of vibration instability of hydraulic system caused by the vibration characteristics of servo system without considering the vibration characteristics of servo system in the design of traditional aircraft brake system,a robust self-learning PID control algorithm with vibration constraint of hydraulic system is innovatively designed according to the sensitivity constraint and robustness constraint of the control parameters.In addition,aiming at the problems of complex external interference factors and changeable runway states during the braking process of aircraft,the robust self-learning PID anti-skid control algorithm is optimized based on the mixed control mode(MSD)of slip ratedeceleration rate and improved particle swarm algorithm.The optimized algorithm can track the optimal slip rate of the system under different runway conditions by adjusting the control parameters and parameter learning rate in real time,which improves the safety and reliability of the system while maintaining high braking efficiency.