Active Suspension Control Of Vehicle Under Complex Driving Conditions

Control of active suspension system can obviously improve the riding comfort and handling safety of vehicles.Intelligent Vehicles has the ability of perceiving environment accurately and technologies to acquire and process information,and can obtain multilateral external information in real time and transmit it effectively.For the sake of boosting the performance of active suspension vehicles further,this paper studies the control methods for active suspension by using the road recognition technology of Intelligent Vehicles combining information of vehicle status.Different road roughness and travelling speed will affect the vehicle's disturbance excitation characteristics of pavement.The design of traditional automobile active suspension control algorithm is based on that vehicle speed and road roughness are both changeless,namely the system disturbance is stationary random signal.However,environment of vehicle driving is complex and changeable,so the system disturbance signal tend to have non-stationary random characteristics,which results in the limitations of the existing control algorithms in improving the performance of active suspensions.Aiming at the vehicle comfort and handling requirements,this paper analyzes the characteristics of vehicle-road coupling excitation,and then designs the active suspension controller considering the characteristics of disturbance signal.Moreover,a gain scheduling control strategy of vehicle active suspension adapt to changes in road uneveness and travelling speed of vehicle is presented to improve vehicle comfort and smooth performance further.After summarizing and analyzing the existing research results of active suspension control algorithm,the control problem and research idea which would be solved in this paper are determined,thereby the research content of this project is developed.First of all,based on active suspension system of quarter-car vehicle models,to analyze the time domain and time-frequency characteristics of vehicle-road coupling excitation signal when the vehicle is passing through the deceleration belt.And then to introduce a weighting function of two order oscillation on account of the frequency distribution characteristics of the disturbance signal,for designing a H? output feedback controller with control constraint conditions.Finally,the simulation result proves that the controller designed in this paper can effectively restrain the disturbance in the corresponding frequency bands and improve the vehicle comfort when the vehicle travels through deceleration belt on the different grade road.In the third chapter,a gain scheduling strategy of H? output feedback controller of vehicle active suspension system adapt to changes in road uneveness and speed of vehicle is presented further.Firstly,to analyze the problem of designing controller in that disturbance energy based on car and road is difficult to determine.Furthermore,to deduce the relationship between disturbance energy in limited time and power spectral density and speed of car.Finally,to give methods of designing and scheduling of H? output feedback controller based on the speed and power spectral density.To reduce the quantity of controller parameters designing,this paper further discusses a way to partition controller parameters divided by speed of car.The simulation results show that the gain scheduling method can improve comprehensively control performances of vertical acceleration and the ratio of dynamic and static load of tyre of vehicle active suspension on various driving conditions.Finally,aiming at the problem that how to improve ride comfort of vehicle which through a collapsed road surface when running straight,active suspension system of half-car model is established in the fourth chapter,and H? feedback controller is designed to suppress vehicle pitching motion,and then to improve vehicle ride comfort from this.The simulation is carried out under the corresponding driving conditions of vehicle.It is proved that the controller designed in this chapter can obviously improve the comfort and safety of vehicle.