抗俯仰液压互联悬架三轴重型货车动态特性_英文_丁飞

Received date: 2011-9-11

Foundation item: Key Project of Chinese National Programs for Fundamental Research and Development (2010CB832705); National Science Fund of China for Distinguished Young Scholars (10725208)

第1卷 第4期

2011年9月汽车工程学报Chinese Journal of Automotive Engineering Vol.1 No.4Sept. 2011

抗俯仰液压互联悬架三轴重型货车动态特性

丁飞1，2，张农2，韩旭1

（1. 湖南大学 汽车车身先进设计制造国家重点实验室，湖南，长沙 410082；

2. 悉尼科技大学 电机、机械与机械电子学院，悉尼，澳大利亚 2007)

摘 要 ：完成了安装抗俯仰液压互联悬架(HIS)三轴货车动力学方程的推导。采用自由图法和阻抗传递矩阵方法推导建立耦合机械系统和液压系统的动力学方程，该特征方程以机械系统的位移和速度以及机械与液压耦合边界处的压力作为状态矢量。对比分析HIS 对车体恢复力和力矩及车体振动固有频率的影响。结果表明，液压互联悬架HIS 系统能够为车体提供较大的抗俯仰力矩。自由振动分析表明，HIS 改变了车体垂向和俯仰振荡中心位置，且增加了车体俯仰模态对应的固有频率，同时车体垂向跳动模态对应的固有频率几乎保持不变。

关键词：液压互联悬架(HIS)；舒适性；抗俯仰悬架；三轴货车

中图分类号：U 463.33+5文献标志码：A DOI ：10.3969/j.issn.2095-1469.2011.04.022

Dynamic Characteristics of a Tri-axle Heavy Truck Fitted

Hydraulically Anti-pith Interconnected Suspension

Ding Fei 1，2，Zhang Nong 2，Han Xu 1

（1.State key Laboratory of Advanced Design and Manufacturing for V ehicle Body, Hunan University, Changsha, Hunan 410082, China;

2. School of Electrical, Mechanical and Mechatronic Systems, University of Technology, Sydney, Australia 2007）

Abstract ：This paper brie fl y presents the derivation of the equations of motion of a tri-axle truck fi tted with pitch resistant hydraulically interconnected suspension (HIS) system. Based on free body diagram and fluid transfer impedance matrix method, the characteristic equations of this mechanically and hydraulically coupled system are derived with a state vector including the displacements and velocities of mechanical system and the pressure at the mechanical-hydraulic boundary section. The comparison analysis of the sprung mass’ responses to road inputs is carried out between the trucks with conventional suspension and hydraulically interconnected suspension system. The obtained results indicate that the HIS system can provide great pitch restoring moment of sprung mass. And the free decay vibration analysis reveals that the HIS system changes the bounce and pitch oscillation center of sprung mass, and the obtained natural frequencies of bounce and pitch modes of sprung mass illustrate that the pitch stiffness is increased while the bounce stiffness is slightly softened.

Key words ：HIS ；ride comfort ；pitch resistant speci fi c suspension ；tri-axle truck

416 汽车工程学报 第1 卷

The bounce and pitch vibration behavior of heavy truck is somewhat different with that of small vehicles because of the longer wheelbase and higher resonant frequencies. The dynamic index k2/ab, where k is the radius of gyration of sprung mass in pitch, i.e. k2=Iyy/M, and a and b are the distance from the front and rear axle to the center of gravity (CG) of sprung mass respectively, changes in a wider range due to the highly variable payload mass and load distribution compared with small vehicles. Moreover, the bounce and pitch heavy coupled dynamic property makes the performance characteristics of heavy truck be strongly related to the pitch motion, including the ride comfort, suspension stroke, and tyre dynamic forces. And the ride performance of heavy truck is generally dominated by the pitch-plane motions while the lateral and roll vibration have been considered to be relatively less important[1]. Therefore, the optimal compromise between bounce and pitch motion can significantly reduce the bounce and pitch displacements of sprung mass and improve the ride and handling performance of heavy truck.

Recently, research efforts have been focused on advanced suspensions for the purpose of overcoming the inevitable compromise between ride comfort and handling performance encountered in conventional suspension systems by varying the system stiffness or damping properties using semi-active or active control. However, the drawbacks of advanced suspension, such as increased cost, weak reliability, power consumption requirements and inherent complexity, promote alternative passive suspensions that can improve vehicle stability and simultaneously maintain the ride comfort. Interconnected suspensions have been reported to be able to overcome the confl ict between ride comfort and handling performance for passenger cars through providing additional stiffness or damping in roll, bounce and pitch as well as warp mode depending on the interconnected scheme[2]. An experimental investigation compared the performance of two SUVs, one equipped with a conventional suspension and the other with a hydraulically interconnected suspension (HIS) under the ‘fi shhook’ manoeuvre specifi ed by USA NHTSA. It was found that HIS equipped vehicles with high roll stiffness provided greatest roll resistance and was also affected by roll damping[3]. Furthermore, a simulation indicated that vehicle equipped with HIS and that with conventional suspension system had very similar ride performance[4].

Most reported work on HIS system focused on the roll and bounce investigation of passage vehicles. Some studies were also reported on the dynamic characteristics of heavy truck fi tted with HIS system using the model of a simple two axle heavy truck[5-6]. However, the study of heavy truck with multi-axle suspension system is not just an extension of two-axle vehicles. It requires more accurate practical study on the further application of HIS system to these heavy trucks.

In this paper, a novel HIS system is proposed for achieving optimal compromising between bounce and pitch motion of tri-axle heavy truck in pitch plane. The derivation of mechanically and hydraulically coupled equations of motion of the truck for vibration analysis is briefly presented. A state vector for the coupled system is so defi ned that it contains all the independent displacements and velocities of mechanical system, as well as the pressure at each coupled boundary section where the mechanical and hydraulic systems kinetically coupled. Based on the transfer matrix method, the impedance matrix of hydraulic system is