巡航过程的节油驾驶是汽车经济性驾驶技术的重要组成，其核心问题是节油巡航策略的辨识。为此，定量化地求解了速比离散型变速器车辆的加速-滑行式（Pulse-and-glide，PnG）节油巡航策略。将节油策略的辨识构建为一最优控制问题；由于发动机的油耗呈强非线性，且PnG策略的加速阶段与滑行阶段动力学特性不一致，导致该问题属于非线性切换型最优控制。采用拼接策略将该非连续问题转化为加速和滑行两段光滑子问题的组合，通过伪谱法实现对积分型性能函数和微分型状态空间方程的代数转化，从而将原最优控制问题转化为非线性规划问题，并进而实现发动机输出转矩、变速器档位、模式切换时刻等参数的数值优化。结果表明：对所研究的车辆，平均巡航速度在中速范围内，PnG策略相对匀速巡航具有显著的节油效果，最高节油率接近25%。最后分析PnG策略实现节油的物理机理，并对节油效果进行了实车试验验证。
徐少兵
,
刘学冬
,
李升波
,
杜雪瑾
,
林庆峰
,
成波
. 速比离散型车辆加速-滑行式节油巡航策略[J]. 机械工程学报, 2017
, 53(14)
: 49
-58
.
DOI: 10.3901/JME.2017.14.049
The fuel-saving cruising technique is the momentous part of economical driving, of which the key issue is how to identify the fuel-saving operating strategies. The pulse-and-glide (PnG) cruising strategy for road vehicles with discrete gear ratio transmission is presented aiming to minimize the fuel consumption in cruising scenarios. The optimization of PnG cruising strategy naturally casts into the optimal control framework. The studied vehicle is featured with strong nonlinear fuel characteristics in engine and different dynamics in the pulse and the glide modes. Those features lead to a non-smooth switching problem, for which the multi-phase knotting technique is employed to cut this problem into two smooth sub-phases, i.e., accelerating and coasting. The pseudo-spectral method is employed to convert the differential type space state equation and integral type performance index. The associated nonlinear programming is finally solved to achieve optimal engine torque, transmission gear ratio, and switching time of pulse and glide. The optimization results show that for the studied vehicle, the PnG strategy can save fuel when cruising at middle speed as compared to the constant speed (CS) operation, and the highest fuel saving rate can reach up to 25%. The mechanism of PnG is discussed, and the fuel saving performance is verified by the real-vehicle tests.
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