挡位离散型车辆经济性加速策略的伪谱法优化

加速过程中, 车辆的油耗与驾驶员的操作策略密切相关. 本文通过最优控制方法定量化地研究了挡位离散型车辆的经济性加速策略. 将加速策略的辨识构建为一个Bolza型最优控制问题(Optimal control problem, OCP), 设计了考虑加速距离影响的经济性定量评价指标. 该问题含有离散型控制变量, 隶属于混合整型最优控制问题, 且性能函数和状态方程呈现强非线性. 为高效地求解该问题, 结合变速器挡位切换规律, 将该整型问题转化为多段光滑问题的协同优化, 采用Legendre伪谱拼接法实现变速器挡位、换挡时机、发动机力矩的数值求解. 解析分析了经济性加速策略的形成机理, 总结了实用化的经济性加速度选择策略和挡位切换规律. 仿真验证了所求策略的节油潜力.

Pseudospectral Optimization of Economical Accelerating Strategy for Vehicles with Discontinuous Gear Ratio

The fuel consumption of ground vehicles in accelerating scenarios is significantly affected by how they are driven. This paper quantitatively studies the fuel optimal accelerating strategies for vehicles with discontinuous gear ratio under the optimal control framework. The identification of economical accelerating strategy is converted into a Bolza-typed optimal control problem (OCP), in which an equivalent fuel consumption index is proposed to eliminate the difference of accelerating distances. The converted OCP has discontinuous input, i.e. gear ratio of transmission, and nonlinear cost function and plant model, which naturally casts in the mixed-integer OCP. Considering the gear shifting rules of mechanical transmission, we transform the discontinuous OCP into multiple but interconnected continuous problems. The multiple-phase knotting technology combining Legendre pseudospectral discretization is used to obtain the optimal numerical solutions to gear position, gear shifting time, and engine torque. The mechanism of the fuel optimal accelerating strategy is analyzed, and the practical rules of gear shifting and acceleration selection are also summarized. The fuel benefit of the economical accelerating strategy is validated by simulations.