Complementary Behaviors of Active Steering and Traction/breaking Force Distribution and Online Optimizations

本研究针对四轮独立转向车辆之轮胎力分配进行主动控制。从主动安全性的观点来看，迫切需要在车辆动力学控制方面取得进一步进展。为了保持直接横摆力矩控制，牵引力/制动力必须有效地分布在四个车轮上。越来越精确的在线优化算法正在研究，以取代以前的经验方法。根据轮胎摩擦圆模型，轮胎受力不会超过轮胎所受垂直载荷与路面摩擦系数的乘积。若按极小极大准则优化轮胎工作负荷，则在轮胎摩擦系数相同的自然条件下，可确定所有轮胎的最优牵引/制动力分配，而不需要实际的摩擦系数。首先，推导了一种简单的代数方法，用于等转角转向系统， ...更多信息 电缆的前轮主动转向和四轮主动转向车辆。四轮独立转向是指车轮转向动作完全独立可控的车辆。在轮胎工作负荷的最优化中，使用前轴和后轴处的横向力的控制条件来优化轮胎力在左前轮和右前轮之间的分配。除了基本的问题公式，转向和牵引力/制动力分配之间的互补性可以被利用，以进一步减少最大轮胎工作负荷。为了实现减阻效果，轮胎力分配器必须考虑两项之间的互补关系进行改造，但其物理结构基本不变。该算法的更新和转向和牵引/制动力分配的合作，有效地减少了最大的轮胎工作负荷。由于基于工作负荷的优化是基于四个车轮上的路面摩擦系数均匀的假设，因此基于μ率的优化需要路面摩擦系数的估计值。为此，本文研究了基于刷子模型的摩擦系数估计方法。将轮胎力与回正力矩之间的关系转化为接触区路面摩擦系数的估算公式。通过用等效值代替估计的轮胎垂直载荷，将工作负荷最小化算法转化为基于μ率的方法。这些算法进行了验证的数值模拟，使用流行的仿真软件CarSim与车辆控制器一起使用Matlab/Simulink环境实现的轮胎力分配器。少

This research project deals with the active control of four-wheel independent steering vehicle with respect to the tire force distribution. From the viewpoint of active safety, there is a strong need for further progress in vehicle dynamics control. In order to maintain direct yaw-moment control, traction/braking forces must be effectively distributed over the four wheels. Increasingly precise online optimization algorithms are being studied to replace the former empirical methods. According to the tire friction circle model, the tire force will not exceed the product of the vertical load on the tire with the road friction coefficient If the tire workload is optimized in minimax criterion, the optimal distribution of traction/braking force can be determined for all tires, under the natural condition that the tires have identical friction coefficients; the actual friction coefficient is not required. First of all, a simple algebraic approach is derived to isoangle steering systems appli … More cable to the front wheel active steering and the four-wheel active steering vehicles. Four-wheel independent steering means vehicles whose wheels' steering actions are totally independently controllable. In optimization of the tire workload, the distribution of tire forces is optimized between the left and right front wheels using control conditions of lateral forces at the front and the rear axles. In addition to the basic problem formulation, the complementarities between the steering and traction/breaking force distribution can be exploited to further reduce the maximum tire workload. To realize the reduction effecte, the tire force distributor must be reconstructed to take accounts of the complementarity relations between two terms, but basically the physical configuration is unchanged. The algorithm is updated and the cooperation of the steering and the traction/braking force distribution effectively reduces the maximum tire workload. Since the workload based optimization is based on the assumption that the road friction coefficient is uniform over four wheels, the μrate based optimization needs the estimated value of road friction coefficients. So we studied the friction coefficient estimation method based on the brush model. The relation between tire forces and the aligning torque is translated into the estimation formula for the road friction coefficient at the contact area. The workload minimization algorithms are translated into the μrate based approach by the replacement of the estimated vertical loads of tires by the equivalent values. These algorithms are verified by the numerical simulations using popular simulation software CarSim with the vehicle controller together with the tire force distributor implemented using the Matlab/Simulink environment. Less