Principle And Control Strategy Design For Switchable Hydraulically Interconnected Suspension

Compared to the passenger cars,off-road vehicles have higher demands on handling stability and passing ability because of bad driving environment and the height of centroid.The hydraulically interconnected suspension(HIS)connects the four wheels with the hydraulic pipes.The hydraulically interconnected suspension can couple dynamic response of the suspension and control the roll mode and the pitch mode of the vehicle.The hydraulically interconnected suspension has six different connection forms,each of which has own unique characteristic.By filling oil and discharging oil,the hight of vehicle body can be adjusted.Aiming at an off-road vehicle,the principle and control strategy of the oil pipes switch and the height switch of the hydraulically interconnected suspension are studied.The main contents of this paper are arranged as follows:(1)Different connection forms of the passive hydraulically interconnected suspension and the height switch hydraulically interconnected suspension are introduced.According to the different forms of pipe connections,the hydraulically interconnected suspension can be combined into six kinds of suspensions.Through the theoretical analysis and software simulation,the anti-roll performance,anti-pitch performance and anti-twist performance of each connection form of the hydraulically interconnected suspension are analyzed,and the principle of height switch hydraulically interconnected suspension is proposed.(2)The principle and control strategy of the oil pipes switch of the hydraulically interconnected suspension are studied.In order to make full use of the advantages of the hydraulically interconnected suspension of different connection forms(mode-1--H2 interconnection form and mode-2--X interconnection form),a specific pattern is selected under different conditions.And the principle of oil pipes switch is proposed.Based on the hierarchical control theory,a switching control strategy is analyzed,and the threshold of oil pipes switch is determined.(3)The principle and control strategy of height switch of the hydraulically interconnected suspension are studied.By filling oil and discharging oil,the height of body can be adjusted.A hierarchical control strategy is designed for the height switch of body,and the threshold for height switch is determined.(4)Based on the Carsim/AMESim/Simulink joint simulation platform,the vehicle model is built.The correctness of the switch control strategy is verified.The ride comfort and handling stability of the vehicle with the hydraulically interconnected suspension in the middle state mode 1 and mode 2 and the original vehicle are compared.