轮毂电机驱动凭借诸多优势成为电动汽车理想的驱动形式, 然而簧下质量增加带来的负效应阻碍了其推广应用。该文基于前期研究揭示的轮毂电机驱动车辆簧下质量负效应的演化规律, 选择电机吸振和两级悬架这2种含电机悬置的轮毂驱动构型, 分别建立半车模型, 开展车辆悬架与电机悬置参数优化以抑制簧下质量增加引发的负效应。为此, 提出了中速段以质心垂向加速度和高速段以俯仰角加速度为主要目标、以悬架偏频和动挠度为约束条件的优化策略, 采用NSGA-Ⅱ算法与熵权法, 对车辆悬架和电机悬置参数开展了多目标联合优化。基于优化得到的车辆悬架与电机悬置参数开展车辆动力学仿真计算与对比分析。结果表明, 相比轮毂电机固定连接构型, 2种含电机悬置的构型均能明显改善车辆的平顺性以及电机振动。其中, 电机吸振构型对车身垂向、俯仰振动和轮胎接地性能改善比较显著, 而两级悬架构型在改善电机垂向振动方面更具优势。

Objective: In-wheel motor drive systems offer significant advantages for electric vehicles, including large chassis space, high transmission efficiency, and great control flexibility. However, in current mainstream in-wheel motor driving vehicles, the unsprung mass is significantly increased because the motor or the driving unit is rigidly connected to the wheel hub. The increased unsprung mass not only deteriorates vehicle ride comfort and road holding performance, but also results in heavy motor vibration. To mitigate these negative effects, configurations with suspended motor or driving unit have been proposed. It is thus desirable to explore the potential of these new configurations in this regard. Methods: This paper aims to mitigate the negative effects of unsprung mass by optimizing vehicle and motor suspension parameters simultaneously. To this end, it examines two typical in-wheel motor drive configurations with motor suspension: the dynamic vibration absorber configuration and the two-stage suspension configuration. Half-vehicle models are established respectively for both configurations, and key indices for vehicle dynamic performance are selected or defined. Drawing on earlier studies on how the increased unsprung mass impacts vehicle performance at various speeds, and considering the trade-off among ride comfort, road holding, and motor vibration, a multiobjective optimization strategy is proposed for parameter optimization of vehicle suspension and motor suspension. In the strategy, the goal is to minimize body vertical acceleration, wheel dynamic load, and motor acceleration at medium speeds while reducing body pitch acceleration, wheel dynamic load, and motor acceleration at high speeds. Constraints include the natural frequency and dynamic deflection of the vehicle suspension. Using the NSGA-Ⅱ algorithm, Pareto optimal solution sets are derived respectively for the two configurations. The entropy weight method is then applied to determine the optimal parameters for vehicle and motor suspensions. With the optimal suspension parameters, dynamic simulations are conducted on a random road, and the dynamic performance is evaluated based on the predefined indices. Results: The results indicate that, compared to the fixed hub motor configuration, both motor suspension configurations achieve a substantial performance enhancement in vehicle ride comfort, road holding, and motor vibration. Specifically, the dynamic vibration absorber configuration delivers greater enhancements in vehicle body vertical and pitch vibrations, as well as wheel dynamic load. Specifically, it reduces body vertical and pitch accelerations by 36.9% and 33.09%, respectively, at medium and high speeds. The wheel dynamic load is decreased by 18.42% and 18.55% at medium and high speeds, respectively. By contrast, the two-stage suspension configuration excels in reducing motor vertical vibration. It reduces motor vertical acceleration by 67.48% and 65.43% at medium and high speeds, respectively. Conclusions: This paper presents a passive control approach to address the negative effects of unsprung mass by utilizing motor suspension configurations. The in-wheel motor drive configurations with motor suspension demonstrate significant potential for improving vehicle dynamic performance. This research serves as a valuable resource for the design of in-wheel motor driving vehicles.