Investigation On The Vehicle Height Control Algorithm Under The Road Excitation

Body height regulation enhances high-speed handling stability and fuel economy as well as ride and comfort of the vehicle,also serves to adjust the body posture.In order to improve high speed maneuverability and average speed,it requires real-time precise control of body height when driving on bumpy road.This paper probed into the effect of road excitation on body height control and designed a sliding mode control algorithm for regulating body height and an authentic body height observing algorithm,which were aimed at solving overshoot of body height regulating and difficulty in measuring authentic body height under the road excitation.A multi-software joint simulation platform was built to complete body height simulation analysis on various roads and validate the feasibility of the algorithms.Main contents include:1.Analysed non-linear characteristics of pneumatic spring during the inflation/deflation process.Built pipeline gas flow characteristic equation and pneumatic spring pressure gradient equation.Built one fourth model and seven degree model of pneumatic suspension body height regulating system.Built AMESim-Simulink simulation platform based on one fourth vehicle pneumatic suspension body height regulating system and CarSim-AMESimSimulink joint simulation model of vehicle pneumatic suspension body height regulating system,laid the foundation for control algorithm design and body height regulating simulation analysis.2.Probed into the mechanism of road excitation effect on body height control and put forward the concept of suspension static deflation which also served as closed-loop feedback of body height regulating.Proposed a scheme that designed a state observer to anticipate suspension static deflation according to known suspension state variables.Deduced equation of suspension static deflation.Designed a state observer based on Kalman Filter Algorithm on the basis of one fourth body height regulating model.Validated that the designed algorithm could precisely predict the suspension static deflation.3.Analyzed overshoot occurred during body height regulating process.Designed one fourth sliding mode control algorithm based on state feedback linearization aimed at overcharge and over discharge.Conducted body height regulating simulation analysis with no road excitation to validate that designed sliding mode algorithm was able to effectively solve the overshoot problem.And did a comparative simulation analysis with road excitation and it turned out that sliding mode algorithm and observing algorithm could significantly improve the precision of body height regulation with road excitation.4.Designed body height regulating sliding mode control algorithm and mass center height observing algorithm based on above-mentioned theories and conducted body height regulating simulation test by means of CarSim-AMESim-Simulink joint simulation platform with various road excitation.It turned out the designed control algorithm could effectively improve regulating precision with road excitation compared with suspension dynamic displacement feedback control strategy and also stem the body’s pitching and rolling motion to improve body height control quality.