| The suspension system connects the wheel and the vehicle body,has an important and direct effect on the ride comfort,handling stability and passing ability of an off-road vehicle,especially,the roll stiffness of the suspension has a great impact on these three properties.Although the lower roll stiffness can improve the ride comfort of the pavement and the passing of the rugged road,but also will lead to a larger roll angle when the turning,increasing the tendency of the vehicle to roll and making the contact condition between the tire and the ground worse,as a result,the the stability of the vehicle stability will be poor;In addition,for high-gravity off-road vehicles,in the emergency steering,a large body roll movement may lead to vehicle rollover;Although,larger roll stiffness can reduce the possibility of vehicle rollover,but also increase the torsional rigidity of the suspension,so that the ride comfort in the pavement of the road will be reduced,and in the rugged road,the driving force will be lost and leading to the off-road vehicles fail to through obstacles.It is difficult for traditional passive suspension to meet the high standards of these three performance,engineers can only use the compromise design.As a result,automotive engineers have been looking for a kind of suspension system that can meet all of these properties at the same time.Firstly,the paper presents a new type of hydraulic body motion stability system,the hydraulic system consists of cylinder,damping valve,accumulator,hydraulic pipe.In addition,the anti-roll bar and shock absorber in the passive suspension are canceled.In this paper,the working principle of anti-roll and anti-twist of the system is analyzed,and the mathematical model of roll,pitch,uniaxial excitation,single-wheel excitation and diagonal excitation is deduced according to the geometric parameters of vehicle suspension,and the influence of the parameters of the hydraulic body motion stability system on the overall performance of the suspension is analyzed.Then,taking an off-road vehicle as the research object,based on the above-mentioned mathematical model of each condition,combined with pre-set performance objectives,matching the key parameters of the system:(1)the limit of working pressure;(2)the front and the rear cylinder diameter and piston rod diameter;(3)the volum and pre-charge pressure of the accumulator;(4)the balance state oil pressure.Refer to the original shock absorber damping curve,connecting the damping valve in the hydraulic circuit,testing the damping force in the MTS shock absorber dynamometer machine,through the replacement of the valve to meet the design requirements of the damping valve.The instability state of the vehicle is defined,and the instability threshold of the vehicle is simulated and analyzedFinally,making the samples and placing them on the vehicle,and then testing the vehicle equipped with the hydraulic body motion stability system and comparing it with the original vehicle.The test includes straight running ride comfort,steering vehicle body roll angle,simulated off-road road body posture and the vertical load difference between left and right tire.The results show that the performance of the modified vehicle is as follows:(1)the ride comfort is not reduced?(2)the roll angle of the body when turning is significantly reduced?(3)the vehicle body posture on off-road is smooth and the vertical load difference between the left and right tires is reduced,the effective driving force is increased. |
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