双半挂汽车列车两种建模方法的对比研究

为建立基于线性轮胎特性的双半挂汽车列车四自由度动力学模型,提出了一种从整体角度分析的建模方法.双半挂汽车列车由牵引车、第一节半挂车和第二节半挂车共计三个车辆单元组成.该方法采用对三个车辆单元进行受力和力矩平衡分析,对第二个和第三个车辆单元进行力矩平衡分析,对第三个车辆单元进行力矩平衡分析,可列出四个微分方程并进一步进行求解.与传统的分别对三个车辆单元进行受力和力矩平衡分析,列出的六个微分方程相比,整体法的优势在于无需过多代入求解车辆单元间的约束条件,减少了化简中的繁琐步骤,可有效防止计算过程中出错.在牵引车前轮角阶跃输入下,通过MATLAB仿真求解,两种方法的仿真结果一致,验证了整体法建模的正确性,为下一步建立更复杂的多挂汽车列车系统动力学模型奠定了基础.对低速和高速工况下的双半挂汽车列车各物理参数的仿真结果分别进行分析,发现其存在后部放大效应,且高速工况下更容易失稳,进一步验证了整体法仿真结果的正确性.

Comparative Study on Two Modeling Methods for B-double Vehicles

To develop a four-degrees-of-freedom (DOF) dynamic model for B-double vehicles based on linear tire characteristics, a modeling method was proposed where the system was studied from a whole view. B-double vehicles were made of three vehicle units, including tractor, first semitrailer and second semitrailer. This method carried out the analysis on force and moment equilibrium of three vehicle units, moment equilibrium of second and third vehicle unit, and moment equilibrium of third vehicle unit, and then four differential equations were deduced and solved further. Compared with traditional method taking the analysis on force and moment equilibrium of each vehicle unit, respectively, six differential equations were then deduced. The advantages of whole method were that it did not need to overmuch substitute and solve the constraint conditions between vehicle unit, which decreased the tedious procedures during simplification and avoided the errors in calculations effectively. With the step angle input of tractor steering wheel, simulation results of these two methods are the same asthat of MATLAB, which verifies the validity of the whole method and lays the foundation for more complex dynamic model of multi-trailers combination vehicles in the next step.The results of physical parameter simulation for B-double vehicles were analyzed under low speed and high speed working conditions, respectively. It indicates that B-double vehicles possess rearward amplification (RWA) and are prone to instability more easily at high speed, which further verifies the validity of whole method.