Research On Vehicle Time-delay Reducing Vibration Control And Vibration Test-bed Design

In recent years,control theory have been applied widely in the design and development of vehicle suspension systems.Many scholars have conducted a lo t of theoretical and experimental researches on vehicle active and semi-active suspensions,but time delays are inevitable in the control process.According to the correlation research on time-delay system in the control field,this problem is that the time-delay factor potentially changes the accuracy of the control system and affects the behavior of the dynamical control system.Therefore,applying time delay and avoiding disadvantages has become the important topic in current study.In this paper,the time-delay feedback control is applied in the engine mount and the vehicle suspension system to study the vehicle vibration characteristics under different operating conditions.The main content of the research is as follows:(1)According to the vehicle vibration characteristics in idle condition,a5-degree-of-freedom half-vehicle suspension model with time delay feedback control is proposed.Firstly,the five-degree-of-freedom dynamic equations with one and two delays are established about different feedback strategies on the engine displacement,velocity and acceleration.Secondly,the appropriate objective function is selected as the evaluation index to measure the vehicle vibration effect.Then,the optimal feedback gains and time delays of the controlled engine and vehicle suspension system are obtained by using the optimization algorithm.Subsequently,combined with the stability switching and the time-delay stability criteria,a new frequency scanning method is utilized to analyze the stability of t he controlled suspension system.Finally,numerical simulations in the Matlab/Simulink environment are conducted to validate the performance of time-delay reducing vibration control on different engine feedback conditions.Simulation results indicate that the active suspension with time-delay feedback control can effectively improve the vibration characteristics and optimize the dynamic performance.Under the vertical harmonic excitation,when the single-delay feedback control based on the engine speed,the vehicle vibration performance can be adjusted effectively and the performance indicators of the vehicle body acceleration and pitch acceleration,the front and rear suspension deflection and tire dynamic displacement are reduced obviously.When the double-delay feedback control based on the engine acceleration,the vehicle vibration effect is the best,and the body acceleration and pitch acceleration are reduced obviously.Therefore,compared with the traditional suspension,the suspension system with time-delay feedback control effectively improves the vehicle vibration performance.(2)Based on the requirement of the driving comfort,the 8-degree-of-freedom vehicle suspension model with time-delay feedback control is proposed.Using the cab movement as evaluating indicator,the time-delay reducing characteristics of the cab suspension system are studied to ensure the ride comfort for the driver.After optimization and stability analysis,the optimal control parameters of the time-delay system are obtained,and its vibration characteristics are verified through simulation analysis.The simulation results show that the time-delay feedback control can effectively reducing the cab vibration response and optimize the ride comfort.(3)Aiming at the five-degree-of-freedom half-vehicle suspension model,a reducing vibration method with double-delay feedback control under road excitation is proposed.The weighted objective function based on the amplitude-frequency response of the body acceleration and pitch acceleratio n is established.Utilizing particle swarm optimization(PSO)algorithm in optimizing and analyzing,the optima l feedback coefficient and time-delay are obtained,then the various performance indicators are simulated in the time domain and frequency domain respectively.Simulation results indicate that with the performance indicators reducing in different range,the vehicle vibration performance and ride smoothness are improved effectively on double-delay feedback control.(4)For the theoretical study of the suspension system,the vehicle vibration test-beg is designed.The test beg consists of a series of equivalent masses and equivalent springs,involving a total of 8 degrees of freedom.The actuators can be added between equivalent body mass and the equivalent tire mass,or the equivalent body mass and the equivalent engine mass.It can study the vibration characteristics under idling and running condition.This study shows that a reasonable choice of time-delay feedback can effectively optimize the suspension system and improve the system vibration performance in idle condition and driving condition to meet the driving requirements.All these results will provide new design ideas and reference methods for the development and research of vehicle suspensio n systems.