Study On Vehicle Ride Comfort And Control Of Non-stationary Running Under Random Exeitation

As the rapid development of auto industury, automobile industry in the world has been gained remarkable achievements, which is going forward to the direction of safety and comfort and environmental friendliness and energy-efficient, among them, comfort of automobiles specially cars and heavy-duty trucks is important indication and means of people’s high quality life and gaining profits of economy. Ride comfort affects directly comfort of automobile. So, the problem of study on non-stationary ride comfort and control of vehicle under random excitations has become the social focus.Based on theory of stationary ride dynamics of vehicle about the vehicle dynamic model analysis methods, the ride performance and suspension control, a detail analysis on ride comfort, road spectrum identification, vehicle dynamic load indentification and suspension control have been conducted using such theories as pseudo excitation method, inverse pseudo excitation method, the theory of line matrix inequality (LMI) and the robust control theory, and new methods were propounded based on theses.Achievements and content of this paper are as follows:1. The theory of pseudo excitation is applied into the ride performance simulation analysis of half-car and whole-car. Becouse there is a lagged relationship between the front and rear wheel, two-support excitations can be transformed into one-support excitation. The model of two-road excitation was built up; it shows an application where pseudo excitation method was used in simulation test system of vehicle ride comfort; the different characteristics of pseudo excitation method and the Fourier transformation method is compared. The result showed the equality of the two methods and this method is valid to resolve the problem.2. Inverse pseudo excitation method is applied to road spectrum identification. When the vehicle is in stationary random vibration, using the deterministic method solved the road spectrum recognition problem. The auto-PSD and cross-PSD of vehicle vibration response is known. Base on the reversing the power spectrum of road excitation, Road excitation PSD is obtained. Advantages of this method include its computationally efficient nature, and its ability to reduce the ill-conditioning of frequency response function near some resonant frequencies because the singular value decomposition is adopted. Frequency response functions and coherence coefficients were used as criteria to verify the feasibility of this method, which overcomes shortcoming of the early road spectrum identification, such as time spent, uneconomical, there are some errors between the PSD base on road surface roughness obtained and the given PSD of road surface roughness.3. Inverse pseudo excitation method is applied to vehicle dynamic load identification. This paper describes the derivative process which using pseudo excitation method base on half-vehicle modle. In accordance with vertical acceleration response spectrum of the front wheel with different velocities on different road level, this paper gives the result of computer simulate expriment for vehicle dynamic load identification. Research has shown the simulated vehicle dynamic load with different velocities on different road level is practicable and can display the changes with different conditions.4. Inverse pseudo excitation method is applied to vehicle ride comfort analysis. Vehicle ride comfort is analyzed by using inverse pseudo excitation method on indefinite road. If a frequency response of car vertical vibration system is known, the method presented in the paper to analyze vehicle comfort is practicable. This method is simple and effective, the problem which the pavement surface roughness (PSR) is taken as the excitation is avoided.5. Based on a single wheel vehicle with three degrees of freedom model, effects of parametric change of car suspension system on vehicle ride comfort analysis is analyzed. These influencing factors mainly include the vertical body acceleration, the vertical car acceleration, the suspension dynamic flexibility, the wheel relative dynamic load. The study provided a theory gist for designing controller for vehicle active suspension.6. This paper mainly studies the state feedback robust control of active suspension, we choose H^, performance of optimization outputs as optimized target. Base on dissipative inequality system, this paper brings forward a practical and effective method to inhibit outputs of the controlled system. The application of this method shows that the controller of active suspension designed by using the method presented can completely meet the requirement of output force characteristics. So far many investigations about the active suspension control mainly dealt with the stationary or smooth-speed running condition of automobiles, and less investigation considered the non-stationary running condition. However, automobiles in actual road running are frequently in the condition of non-stationary running, such as acceleration for overtaking on the inside or deceleration for braking operation, etc. So the method presented can overcome these shortcomings. The1/4vehicle and half-vehicle model H∞robust control simulation were performed by using H∞robust control theory base on the condition of non-stationary running. According to the specific example, this paper has given some emulation and comparison results between active suspension system and passive suspension system different in some respect, including time and frequent domain characteristics and model for identifying parameter uncertainty, etc, which demonstrates the practicability and effectiveness.