Modeling Of Displacement-dependent Shock Absorbers And Study Its Effects On Vehicle Ride Comfort

At present, Passive double-tube hydraulic shock absorber is the most widely used in vehicle, its mechanical property is a kind of compromise between the vehicle ride comfort and handling stability and it is difficult to obtain the optimal suspension performance. To solve the contradiction encountered in the traditional suspension, semi-active suspension and active suspension are continuous development in recent years, which can achieve damping continuous adjustable, and have been applied to the real vehicle. These advanced suspension system installed complex test devices, actuators and processors, although significantly improves the performance of suspension system, but there also has complex structure, high cost, large energy consumption and other outstanding issues, so it is difficult to get widely used.Under this background, this paper designed a displacement-dependent shock absorber(DDSA), which damping characteristics change with the change of the position of the piston. When the vehicle ride on good road under no-load condition, the damping force is small, which is good to improve vehicle ride comfort; When the vehicle is full-loaded or in emergency conditions, such as steering、braking, the damping force of the damper becomes high, which can effectively control the body posture, inhibit wheel vibration, to ensure the vehicle driving safely. In addition, the damper is improved based on passive damper, simple structure, no need of additional sensors and controllers, without increasing the cost, and has broad application prospects.This article studied in-depth on the displacement-dependent shock absorber’s damping characteristics and its effect on vehicle performance, the main research contents are as follows:1、Establish physical modeling of displacement-dependent shock absorber and analysis its mechanical characteristics. According to the structure and working principle of the original damper, using the theory of fluid mechanics, deduced the flow-pressure equation of each valve and established Simulink model of the original damper, the accuracy of the model was verified by bench test of the original damper, and analyzes the influence of valve parameters on the external characteristics; combine with the structure characteristics of displacement-dependent shock absorber, establish the physical model of displacement-dependent shock absorber, and study the effect of structure parameters of the bypass on the damping characteristics.2 、 Optimization design and manufacture of displacement-dependent shock absorber. Embed displacement-dependent shock absorber model into a quarter vehicle dynamics model, establish the optimization model of single wheel vehicle, determine the optimization objective function and constraint conditions based on vehicle ride comfort, using the genetic optimization algorithm to optimize a bypass parameters. According to the result of optimization, manufacture displacement-dependent shock absorber prototype, through comparing the model simulation results and prototype test data to verify the correctness of displacement dependent shock absorber model.3、Test verification of the effect of displacement-dependent shock absorber on improve vehicle ride comfort. Build damper-in-the-Loop real-time simulation system based on x PC Target, through comparison result of Hardware-in-the-Loop test to verify the effect of displacement-dependent shock absorber on improve vehicle performance. The displacement-dependent shock absorber prototype installed in the test vehicle, select the cobblestones, Belgium road and highway three kinds of typical road to carry on vehicle ride comfort test and verify the displacement-dependent shock absorber have an advantage over improving vehicle ride comfort:(1)On cobblestone and Belgium road, the vehicle which install displacement dependent shock absorber, comfort evaluation index decreases more than 10% on no-load condition, improved slightly when full load;(2)On highway, the vehicle which install displacement dependent shock absorber, comfort evaluation index decreases about 5% on no-load condition, and increases slightly on full-load condition.