| Hydraulically interconnected suspension(HIS) can improve vehicle’s off-road performance(the wheel ground contact and body twist load). When comparing to traditional stabilizer bar, HIS can transfer the force generated by a single movement of the wheels to the other wheels, therefore the vehicles fitted with HIS process superior dynamic performance in a particular body-wheel movement mode. The system has nonlinear stiffness and damping characteristics, therefore the vehicle with HIS will possess good comfort, handling stability and superior off-road performance at the same time.Academic research of HIS currently focused on enhancing anti-roll effect of the vehicle, or to enhance comfort, but in terms of enhancing vehicle’s off-road performance and improving tire contact force, the study is not much. In this paper, through simulation analysis and experimental study, the theory of HIS enhancing the vehicle off-road performance was analyzed, the differences between the various forms of suspensions in off-road performance were compared based on the car. Main researches and innovations are as follows:First, the hydraulic system unit of HIS is theoretical modeled and analyzed, which is the basis to study vehicle performance. For the study of the external characteristics of the HIS, the hydraulic system flow- pressure is firstly transient modeled and analyzed based on the hydraulic unit. A mathematical model of the hydraulic system unit is established. Further some tests are made to verify the accuracy of the mathematical model; the model indicates that the hydraulic system unit can reflect changes of the parameters of the hydraulic system under different incentives, providing the basis to theoretical study of vehicle dynamics. At last, the mechanical properties of the damping force of the hydraulic system are simulation analyzed, to find out the hydraulic system of key parameters on the damping characteristics.Second, the vehicle fitted with HIS is modeled in time domain and some simulation results are presented. The vehicle dynamic model is established by using state space method. Based on the mechanical and hydraulic coupling model, some studies of body-wheel mode in warp mode are investigated. The analysis results of different suspension systems are compared, such as body torsional load and wheel grounding performance. It is verified that the vehicle roll stiffness target and off-road requirements can effectively reach to a balance. The hydraulic parameters have much free space to design.Third, the vehicle fitted with HIS and anti-roll bars are tested in terms of warp mode. Through the tests results include before and after the roll axis angle absolute value of the difference, the body additional torsional load and body vertical acceleration; it can be seen from the test results, compared with the traditional suspension, HIS can both improve the roll stability and off-road performance.In summary, this paper has developed HIS system based on a sports utility vehicle, the mechanism of HIS enhancing off-road performance is analyzed and road tests are provided. It provides some guidance and practical application value to the suspension design. |
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