针对分布式电驱动汽车,以实现车辆主动安全性同时兼顾制动能量回收为目标,提出一种主动前轮转向(AFS)与电液复合制动集成的控制策略.AFS控制器采用滑模变结构控制,滑移率控制器采用滑模极值搜索算法,基于分层结构(上层为期望制动力矩计算模块,中层为考虑执行器带宽的动态控制分配模块,下层为电机与液压复合执行器),并考虑位置与速率约束.转向制动时,考虑车辆纵向动力学对侧向动力学的影响,引入前轮转角对滑移率控制律进行了修正.在MATLAB/Simulink中建立七自由度整车模型,对控制算法进行了验证.结果表明:分离路面直线制动时,所提出的控制策略可以同时保证制动能量回收和制动方向稳定性;转弯制动时,可以更好地跟踪理想横摆角速度,提高了车辆的侧向稳定性.
A new control strategy was proposed by integrating active front steering and electro-hydraulic braking in distributed electric drive vehicles to ensure vehicle active safety by taking into account braking energy recuperation. The AFS controller was synthesized by means of sliding mode control. The wheel slip controller was designed with a hierarchical control structure. In the upper layer, sliding mode extremum-seeking algorithm was adopted to obtain the desired braking torque, and a dynamic control allocator considering different actuators bandwidths was employed to determine the optimal split between the electric and friction brake torque in the middle layer. In the lower layer, a hybrid actuator system consisting of the hydraulic brake and the electrical motor was designed on the basis of actuator position and rate constraints. The wheel slip control law was modified by introducing the road wheel angle factor considering the strongly coupled dynamics of steering and braking systems when braking-in-turn. Simulation results obtained with a 7-DoF vehicle model in MATLAB/Simulink environment have shown that the control strategy can significantly enhance vehicle directional stability and ensure braking energy recovery in split-t; straightqine braking, and can better track ideal yaw rate with vehicle lateral stability improvement when cornering.