基于聚类优化等效因子的分布式混动拖拉机能量管理策略

    Energy management strategy for distributed hybrid electric tractors based on clustering optimization equivalent factors

    • 摘要: 分布式混合动力拖拉机(distributed hybrid electric tractor, DHET)多动力源解耦特性显著提升了系统能效与工况适应潜力,同时也对动态工况下的能量分配效率提出了更高要求。自适应等效最小燃油算法(adaptive equivalent consumption minimization strategy, A-ECMS)因其较好的燃油经济性和可优化潜力被广泛应用于混动系统的能量管理问题,但其优化效果过于依赖等效因子的动态标定精度,因此,本研究针对现有自适应等效最小燃油算法中等效因子实时优化在工况性适应性方面的不足,提出一种融合聚类优化与自适应等效最小燃油算法(A-ECMS)的能量管理策略,采用分层架构通过多阶段优化提升策略的工况适应性和燃油经济性。首先,针对传统工况划分主观性较强的问题,通过K-means聚类算法对标准工况进行聚类分析,并引入轮廓系数(silhoiette coefficient, SC)作为聚类有效性评价指标,确定最佳簇类数量;针对聚类结果,采用动态规划算法(dynamic programming, DP)求解不同簇类的最优等效因子;其次,为解决在线控制中单一等效因子的适应性缺陷,构建了基于连续权重重核函数的等效因子映射模型,基于实时工况特征与离线聚类中心动态匹配等效因子,实现等效最小燃油算法的自适应调整。硬件在环结果表明,该方法能够在绝大部分工况下维持发动机和电机工作在高效区间,在测试工况下,等效燃油消耗量相较于基于PI控制器的自适应等效最小燃油算法降低了6.54%,有效提升了混合动力拖拉机燃油经济性。

       

      Abstract: As the core power equipment in modern agricultural production in China, the tractor plays a significant role in promoting sustainable agricultural development. During plowing operations, complex and variable field conditions often lead to frequent fluctuations in traction resistance, making it difficult for tractors to maintain highly efficient and energy-saving operating states. Traditional internal combustion engine tractors face inherent challenges such as carbon emission restrictions and thermal efficiency bottlenecks, while pure electric solutions are limited by current battery technology in terms of energy density and endurance, making it difficult to meet the demands of high-power continuous operation. To address these issues, this paper proposes a distributed hybrid electric tractor (DHET) architecture with decoupled power output. This architecture significantly improves system energy efficiency and operational adaptability through the decoupling characteristics of multiple power sources, but it also imposes higher requirements on the efficiency of energy allocation under dynamic working conditions. As a core technology for achieving high efficiency, energy savings, and reliable operation in hybrid electric tractors, the energy management strategy directly affects overall vehicle performance. The adaptive equivalent consumption minimization strategy (A-ECMS) is widely used in hybrid power systems due to its excellent fuel economy and optimization potential. However, the effectiveness of this algorithm highly depends on the dynamic calibration accuracy of the equivalent factor, and it suffers from limitations in adaptability to varying working conditions. Therefore, this study proposes an energy management strategy that integrates clustering optimization and A-ECMS. A hierarchical architecture is adopted to enhance the adaptability and fuel economy of the control strategy through multi-stage optimization. Specifically, to address the strong subjectivity of traditional working condition division methods, a K-means clustering algorithm is introduced to analyze standard cycles, with the silhouette coefficient (SC) used as an evaluation metric to determine the optimal number of clusters. Furthermore, based on the clustering results, dynamic programming (DP) is employed to solve for the optimal equivalent factor corresponding to each cluster. To overcome the inadequacy of a single equivalent factor in online control, a mapping model of the equivalent factor based on a continuous weight re-kernel function is constructed. This model enables dynamic matching of the equivalent factor according to real-time working condition features and offline cluster centers, thereby enhancing the adaptive adjustment capability of the A-ECMS algorithm. Hardware-in-the-loop (HIL) experimental results demonstrate that the proposed method can maintain the engine and motor operating within high-efficiency ranges under most working conditions. Under the tested conditions, the equivalent fuel consumption of this strategy is reduced by 6.54% compared to the adaptive equivalent consumption minimization strategy based on a PI controller, significantly improving the fuel economy of the hybrid electric tractor and indicating promising prospects for engineering applications.

       

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