College of Automobile and Traffic Engineering, Nanjing Forestry University, Nanjing, China.
PLoS One. 2023 Jun 9;18(6):e0285485. doi: 10.1371/journal.pone.0285485. eCollection 2023.
The purpose of this paper is to study the control of differential steering for four-in-wheel-motor electric vehicles. The so-called differential steering means that the front wheel steering is realized through the differential driving torque between the left and right front wheels. With the consideration of tire friction circle, a hierarchical control method is proposed to realize the differential steering and the constant longitudinal speed simultaneously. Firstly, the dynamic models of the front wheel differential steering vehicle, the front wheel differential steering system and the reference vehicle are established. Secondly, the hierarchical controller is designed. The upper controller is to obtain the resultant forces and resultant torque required by the front wheel differential steering vehicle tracking the reference model through the sliding mode controller. In the middle controller, the minimum tire load ratio is selected as the objective function. Combined with the constraints, the resultant forces and resultant torque are decomposed into the longitudinal and lateral forces of four wheels by the quadratic programming method. The lower controller provides the required longitudinal forces and tire sideslip angles for the front wheel differential steering vehicle model through the tire inverse model and the longitudinal force superposition scheme. Simulation results show that the hierarchical controller can guarantee the vehicle to track the reference model well on both of the high and low adhesion coefficient road with all of the tire load ratios smaller than 1. It can be drawn that the control strategy proposed in this paper is effective.
本文旨在研究四轮电机电动汽车的差动转向控制。所谓差动转向，是通过左右前轮的差动驱动力矩来实现前轮转向。考虑到轮胎摩擦圆，提出了一种分层控制方法，以实现差动转向和恒纵向速度。首先，建立了前轮差动转向车辆、前轮差动转向系统和参考车辆的动力学模型。其次，设计了分层控制器。上层控制器通过滑模控制器获得前轮差动转向车辆跟踪参考模型所需的合力和合成转矩。在中间控制器中，选择最小的轮胎载荷比作为目标函数。结合约束条件，采用二次规划方法将合力和合成转矩分解为四轮的纵向力和侧向力。下层控制器通过轮胎逆模型和纵向力叠加方案为前轮差动转向车辆模型提供所需的纵向力和轮胎侧偏角。仿真结果表明，分层控制器可以保证车辆在高低附着系数路面上都能很好地跟踪参考模型，并且所有轮胎载荷比都小于 1。可以得出结论，本文提出的控制策略是有效的。
