四轮独立驱动电动汽车行驶稳定性分析与联合滑模变结构主动控制

Driving Stability Analysis and United Sliding Mode Variable Structure Active Control of Four Wheel Independent Driven Electric Vehicles

针对四轮毂电机独立驱动汽车各轮力矩解耦可控的特点,分析车辆转向受力对四轮独立驱动电动汽车行驶稳定性的影响,提出四轮独立驱动电动汽车转向稳定性控制策略,为四轮独立驱动电动汽车四轮转矩协调控制,提升整车行驶稳定性提供了思路。基于模型跟踪控制的思想,采用分层控制思想设计控制器,控制器包含参考模型、顶层控制器、底层控制分配器。采用带质心侧偏角约束的2自由度车辆模型作为参考模型,设计出一种新的非线性联合滑模变结构主动控制的顶层控制器,该方法可以在一定程度上实现车辆横摆角速度和质心侧偏角的解耦控制,避免了横摆角速度和质心侧偏角的较大变化,从而保证汽车稳定性。在底层控制分配器中,采用基于轮胎稳定裕度最大化的最优分配方法。在Carsim软件中,搭建四轮轮毂电机独立驱动电动汽车模型,在Simulink软件中搭建控制策略模型。针对双移线工况,Carsim/Simulink联合仿真的结果表明,滑模变结构控制器具有较好的收敛性,控制分配模块可以实现四轮力矩的优化分配,能够提升车辆在极限工况下的稳定性。研究将为轮毂电机驱动车辆分布式协调控制提供理论支撑。

Aiming at the characteristics of decoupling and controllable wheel torque of four-wheel-independent-driven electric vehicles,the influence of the vehicle force during the steering process on the lateral stability of the four in-wheel independent-drive electric vehicle is analyzed,and the steering stability control strategy of the four in-wheel independent drive electric vehicle is proposed,which provides an idea for the torque coordinated control of four-wheel independent-drive vehicles for the improvement of vehicle lateral stability.Based on the idea of model tracking control,the controller is designed by the hierarchical structure.The controller includes a reference model,an upper controller,and a bottom control allocator.A 2 degrees of freedom model with centroid deflection is used as the reference model to design a novel nonlinear sliding mode variable structure motion upper controller.This method could realize the decoupling control of vehicle yaw rate and sideslip angle to a certain extent,and avoid large changes of yaw rate and sideslip angle,thus ensuring vehicle stability.In the bottom control allocator,the optimal allocation method based on maximizing tire stability margin is adopted.In Carsim,a four-wheel hub motor electric vehicle model was built and Simulink was used to build a control strategy model to carry out Carsim/Simulink joint simulation.The double lane change test results show that the sliding mode variable structure controller has better convergence,and the allocation module can realize the optimal distribution of the four wheel torque,which can increase the stability of the vehicle under the limit condition.The study will provide theoretical support for the distributed coordinated control of wheel motor independent-drive vehicle.