Research On Semi-active Control Of Aircraft Nose Wheel Reduction

The control of nose wheel shimmy system is generally divided into passive control,semiactive control and active control.The semi-active control is between the passive control and the active control.It combines the advantages of the two and makes up for the shortcomings of the two.It is a research hotspot nowadays.Compared with the traditional oil damper,the MRF damper applied to the nose wheel shimmy of aircraft has the advantages of adjustable damping force,short response time and stable performance.Therefore,the MRF damper has a good effect on suppressing the nose wheel shimmy of aircraft.Based on this,the dynamic model of the MR damper and the control of the nose wheel shimmy are studied,the specific work of this thesis is as follows:First of all,through the analysis of the working principle of the MR damper and the commonly used dynamic expression model of the MR damper,using the mechanical performance test data of the MR damper,using Bouc-Wen model and hyperbolic tangent model to build the dynamic model of the MR damper respectively,and identify its parameters,which lays the foundation for the design of the MR damper's control algorithm.Secondly,the semi-active control model of nose wheel shimmy is established by analyzing the dynamic balance equation of wheel shimmy and the constraints of tire rolling.Through the Simulink simulation of the nose wheel shimmy movement,the stability of the shimmy system is analyzed,and the critical shimmy speed in the critical shimmy state is obtained,and the shimmy movement of the nose landing gear in different sliding speed States is analyzed.According to the simulation results of nose wheel shimmy,the influence of structure and tire parameters on nose wheel shimmy is analyzed.Thirdly,in order to restrain the nose wheel shimmy,according to the research of the characteristics of the MR damper and the regularity of the nose wheel shimmy system,the linear quadratic optimal control strategy(LQG control strategy)and the fuzzy control strategy based on the MR damper are designed.Through the numerical simulation in ideal state,LQG control strategy and fuzzy control strategy are used to compare their control effects with passive control,which lays the foundation for the next step of time-delay control.Finally,the mathematical model of nose wheel shimmy with time-delay is established by analyzing the time-delay of MR semi-active control system.Based on the study of the control principle of Smith predictor,S-LQG time-delay controller and fuzzy Smith predictor compensation controller are designed.Through the simulation analysis of the nose wheel shimmy control system with time-delay,the control effect of ideal state controller,no measure state controller with time-delay,S-LQG time-delay controller and fuzzy Smith predictive compensation controller are compared,and the necessity and rationality of the research on time-delay control based on MR damper are proved.