Nonlinear Vibration And Active Control Of Landing Gear System

The landing gear system is an important component to bear the external load when the aircraft landing and taxiing. It plays an important role in the safety of aircraft landing and taxiing. The vibration of the landing gear system is caused by irregularity of airport ground. The vibration of landing gear system may be the important factor to result in low service life, poor stability, difficult operation and low passenger comfort. The vibration of landing gear system is an important issue in aeronautical engineering. The problem of landing gear system vibration has theoretical significance and practical application value.In the present dissertation, nonlinear vibration and active control of landing gear system is studied. In accordance with the model from simple to complex, we investigate the single degree of freedom and two degree of freedom nonlinear landing gear vibrating system. The effect of nonlinear parameters on vibration of landing gear system is analyzed, and delayed feedback control is applied to control the vibration of the landing gear system. The vibration of landing gear system is studied when the 1:2and 1:3 internal resonance occurs. The dynamical behavior of the landing gear system is investigated when the external excitation nears to the first and second order vibration mode frequency. The focus is to use delayed feedback control to control the vibration of the landing gear system. The effect of gain and time delay on vibration of landing gear system is studied, and delayed feedback control is employed to suppress the vibration of the landing gear system.First, the landing gear system is simplified into a single degree of freedom mass-spring-dashpot nonlinear vibrating system. The nonlinear dynamical behavior of the system is analyzed, and delayed feedback control is employed to control the vibration of the vibrating system. The effect of damping coefficient, nonlinear stiffness coefficient, gain of delayed feedback and time delay on vibration of landing gear system are studied. The results show that large value of nonlinear stiffness coefficient may result in multiple value phenomenon of the amplitude frequency response curves. As the increase of damping coefficient, the vibration of the landing gear system is decreased. Large value of delayed feedback gain may help to stabilize the system.Second, taking into account the single degree of freedom model does not fullyreflect the vibration characteristics of landing gear system, therefore, a two degree of freedom nonlinear model is constructed, while landing gear and wheel sets as two independent degrees of freedom. Taking into account that the landing gear structure may be two and three nonlinearity, the cases of 1:2 and 1:3 internal resonance are investigated respectively. In the cases of external excitation nears to the first and second order vibration mode frequency, the vibrating characteristics of the landing gear system is investigated. The influence of the physical parameters, such as the nonlinear parameter and the damping coefficient, on the dynamic behavior of the system is studied. The main purpose is to study the delayed feedback control to control the system vibration, the effects of delayed feedback gain and time delay on the system vibration are analyzed. The research results show that the amplitude of the landing gear will be decreased with the increase of the system damping, and the amplitude of the wheel set does not affected by system damping. The amplitude of the landing gear system will remain unchanged when the damping is increased to a certain value. The nonlinear stiffness coefficient has no effect on the amplitude of the system, and it will cause the resonance peak value offset, so it is easy to cause the system to lose its stability. The amplitude of landing gear system changes periodically with time delay, there are peak and though in the amplitude-delay response curves.The vibration of landing gear system can be suppressed when time delay is located in the through of amplitude-delay response curves.Finally, the multiple scales method is employed to obtain the second order approximate analytical solutions. The software of Mathematica and WINPP is applied to obtain the numerical simulation results. The results of theoretical analysis is agree with the numerical simulation well, and reliability of results is confirmed.The research results of present dissertation show that delayed feedback control technique is a kind of simple operation, good vibration suppression and wide frequency bandwidth. The performance of vibration suppression is significant when delayed feedback control is applied to landing gear vibrating system. In the view of theory, the research of present dissertation has promoted the development of nonlinear dynamics. In the view of practice, it provides a new vibration suppression technique for technical personnel.