基于MPC的分布式驱动越野车辆原地转向控制研究

Research on Pivot Steering Control of Distributed Driving Off-Road Vehicles Based on Hierarchical Structure

针对轮毂电机分布式驱动越野车辆在狭小空间快速机动的需求,设计了一种分层结构的原地转向控制策略。基于动力学原理分析了各轮载荷、附着条件对原地转向横摆速度的影响机理,并搭建原地转向运动学模型,上层采用模型预测控制算法设计原地转向理想轨迹以及期望的横摆角速度,开发基于PI滑模控制的横摆运动跟踪算法,通过补偿转向横摆力矩以提高方向角控制的鲁棒性和稳定性,下层以最优轮胎利用率为目标,设计二次规划算法优化分配各轮附加横摆力矩。dSPACE硬件在环测试结果表明,所提出的控制算法可在保证稳定性的前提下实现原地转向,大幅提高了车辆的转向机动性,在方向盘动态输入仿真中,车辆最大转弯半径为0.157 m,转向中心的最大偏移量为3.610 m;同时,驾驶员能对转向过程进行闭环控制,实现了原地转向过程中横摆速度的实时调节。

A hierarchical pivot steering control strategy has been developed to meet the demand for fast maneuvers of in-wheel motor distributed drive off-road vehicles in confined spaces.Firstly,based on the principles of dynamics,the influence mechanisms of individual wheel loads and adhesion conditions on the yaw velocity of pivot steering are analyzed,and a kinematics model for pivot steering is constructed.The upper layer adopts the model predictive control algorithm to design the ideal trajectory of pivot steering and the expected yaw rate.The yaw motion tracking algorithm based on PI sliding mode control is developed to improve the robustness and stability of directional angle control by compensating the yaw moment during steering.The lower layer aims for the optimal tire utilization rate,and uses a quadratic programming algorithm to optimize the allocation of the additional yaw moment for each wheel.The simulation results from dSPACE hardware-in-loop tests show that the proposed control algorithm can achieve pivot steering while ensuring stability,which greatly enhances the steering maneuverability of the vehicle.In the steering wheel dynamic input simulation,the maximum turning radius of the vehicle is 0.157 m and the maximum offset of the steering center is 3.610 m.Meanwhile,the driver can carry out closed-loop control over the steering process,achieving the real-time adjustment of the yaw speed during the pivot steering process.