中文摘要：

为简化对车辆侧倾动力学的研究特别是对车身侧倾角的估算和控制,提出针对车身侧倾角的Padé模型降阶方法。该文首先建立了线性三自由度车辆模型,并在此基础上推导出了车身侧倾角的传递函数,由于此传递函数的高阶特性难以用于车辆侧倾动力学的计算与控制中,所以接着对所推导出的侧倾角传递函数进行降阶处理。又考虑到车身侧倾的低频特性以及Padé模型降阶法在低频区能有较好的拟合效果,该文采用Padé模型降阶法对车身侧倾角传递函数进行降阶处理。为了验证降阶后模型的有效性,从时域、频域和复域3个方面分别进行了论证,并通过Truck Sim和Matlab进行了仿真对比。结果表明降阶后的模型在低频区具有较好的逼近效果,此降阶方法可以简化对车辆侧倾动力学的研究,并可以将此降阶模型应用于车身侧倾角的估算和控制中。

英文摘要：

With the continuous development of agricultural engineering, architectural engineering and transportation, more and more technical vehicles for agriculture and architecture, heavy trucks, buses, vans, and so on have run on the road. However,the vehicle rollover accidents caused by high center of gravity have also increased in recent years. In order to study the vehicle roll dynamics and prevent rollover accidents by effective control, it is necessary to calculate the roll angle of vehicle body accurately. In this paper, a linear 3-DOF（degree of freedom） vehicle model was built firstly, then the transfer function of the vehicle body roll angle was deduced from it and the steady-state gain of the roll angle was also obtained. The denominator of the roll angle transfer function is a fourth order expression, and the numerator is a second order expression. High order system is difficult to be calculated and controlled for transient-state, so this paper proposes main effort to reduce the order of the vehicle roll model inspired by the thought of reducing system order from some researchers. Considering that the frequency of the roll dynamics is low generally, and the Padé technique for model reduction has good approximation in low frequency domain, the Padé reduction technique was adopted in this paper. After reducing the order of the roll model, the denominator and numerator of the transfer function came to be a second order expression and a first order expression respectively.Subsequently, the validity of this reduction method was illustrated from 3 aspects, i.e. time domain, frequency domain and complex domain respectively. In the time domain, the original model was simulated by Trucksim, and was also simulated by Matlab. Then, the roll angle of reduced model was compared with that of the original model in the vehicle driving conditions of angle step and sine wave. Simulation results show that, the steady-state gain and the changing tendency both fit well. With the vehicle velocity increasing, the approximation