全轮转向非线性重型车辆稳定性集成控制研究

Nonlinear integrated control for maneuvering stability of a heavy-duty vehicle with all-wheel steering

建立了某三轴重型车辆的十自由度操纵稳定性非线性动力学模型,轮胎纵向力与侧向力采用非线性的刷子模型计算。考虑垂向载荷转移和车轮滑移率变化等对轮胎侧向力的影响,基于刷子模型对车辆参考模型的轮胎侧偏刚度进行逆向估计和动态实时修正。结合阿克曼原理和模糊PID控制技术,设计了一种主动比例转向控制(6WS)和直接横摆力矩控制(DYC)相结合的集成控制器(6WS+DYC),参考模型的横摆角速度名义值通过前轮转向和全轮转向横摆角速度相等时的临界速度确定。基于MATLAB/Simulink建立了车辆模型和6WS、DYC及6WS+DYC三种控制器,仿真了车辆高速转向和低附着路面转向两种极限工况下的响应,并对三种控制器的有效性进行了对比分析。研究结果表明,6WS控制可在一定程度内降低车辆的失稳程度,DYC控制和6WS+DYC控制均能保证车辆在极限工况下具有较好稳定性;6WS+DYC控制能够使车辆在两种转向工况下的质心侧偏角均接近于零,同时能够有效降低车辆横摆角速度、簧载质量侧倾角和车辆侧向加速度,其效果明显优于6WS控制和DYC控制。

A 10-DOF nonlinear dynamic model for a certain 3-axle heavy-duty vehicle was established to study its maneuvering stability. Its tire longitudinal and lateral forces were calculated with the nonlinear brush model. Considering effects of vertical load transition and wheel sliding rate on tire lateral forces, based on the brush model, the tire cornering stiffness of the vehicle reference model was reversely estimated and dynamically corrected. Using Ackerman principle and Fuzzy PID control technology, an integrated controller (6WS+DYC) combining the active proportional steering control (6WS) and the direct yaw moment control (DYC) was designed. The normal value of yaw rate of the reference model was determined with the critical speed when the yaw rate of the vehicle front wheel steering (FWS) was equal to that of its all-wheel steering (6WS). Based on the software MATLAB/Simulink, the vehicle model and three controllers of 6WS, DYC and 6WS+DYC were built to simulate vehicle responses under two limit working conditions of high speed steering and low adhesion road surface steering. The effectiveness of three controllers is contrastively analyzed. The results showed that the 6WS control can reduce the instability of the vehicle to a certain extent;the DYC control and the 6WS+DYC one can ensure the heavy-duty vehicle to have a better stability under limit working conditions;the 6WS+DYC control can make vehicle sideslip angles two limit working conditions be close to zero, and can effectively reduce vehicle’s yaw rate, spring mass side inclination and vehicle’s lateral acceleration, its control effect is obviously superior to those of the 6WS control and the DYC one.