液压机械无级传动全功率动力换段机理及控制研究

The power shift control is the key to improve the performance of Hydro-mechanical variable transmission (HMT). Studies found that the power shift method by overlapping the clutches’ engagement and regulating the displacement of the variable displacement hydraulic component could reduce the fixed displacement hydraulic component speed fluctuation and power interruption. In this method, moreover, the high and low pressure circuit interchange of the closed hydraulic circuit can be finished in the overlapping period of the clutches, which makes it possible to shift with full power. In this project, the process of the HMT full power shift will be divided into five stages: the current range, the former stable period, the power transition period, the later stable period, and the target range, and the full power shift theory and control will be studied. The main research contents and innovations include: (1) A real-time model predicting the key state parameters of target range will be established, and the theory of predicting state of the target range according to current range will be proposed. (2) The power transition mechanism will be revealed. A real-time displacement regulating model and a displacement inverse control model of the variable displacement hydraulic component will be built. The theory and method of power transition by regulating the displacement current to control the high and low pressure circuits interchange of the closed hydraulic circuit will be proposed. (3) A real-time control model will be established, and the full power shift control technology based on model prediction will be studied. The parameters’ online self-learning method will be explored to improve the shift quality. This research will establish the theory and method of HMT full power shift, which can not only solve the HMT shift problem, but also provide new way for the multimode hybrid transmissions.

换段过程控制是决定液压机械无级传动性能的关键技术和瓶颈。研究发现，采用离合器结合重叠、调节排量的动力换段方法能减小液压元件转速波动，避免动力完全中断，且可在离合器结合重叠中完成液压回路高低压侧互换，使全功率动力换段成为可能。本项目将全功率动力换段分为当前段、前稳定、功率过渡、后稳定、目标段五个阶段，研究其机理及控制方法。主要研究内容及创新点包括：①建立目标段关键状态参量实时预测模型，提出基于当前段关键状态参量的目标段状态预测理论。②揭示换段过程功率过渡机理，建立实时排量调节模型、排量控制逆模型，提出通过排量电流主动控制液压回路高低压侧释压建压过程，实现功率转移的理论与方法。③构建实时控制模型，研究基于模型预测的全功率动力换段控制方法，探究以换段品质为目标的模型参数在线自学习方法。项目将建立液压机械无级传动全功率动力换段理论与方法，彻底解决换段问题，也为多模混合动力模式切换提供新途径。

动力换段是液压机械无级传动(HMT)的关键技术，研究换段中功率过渡机理及其主动控制方法，实现无动力中断的全功率换段，对于彻底解决换段问题、提高车辆动力性具有重要意义。.提出了五阶段全功率换段方法，在双离合器结合重叠的动力换段中，通过调节液压元件排量比，主动控制液压回路高低压侧压力互换，控制当前段离合器转矩向目标段离合器有序转移，实现了换段过程传递全功率。建立了全功率换段目标段状态预测模型，分析得到了目标段状态与当前段关键参数的内在规律；开展了典型工况下目标段状态预测试验，验证了预测模型的正确性。.建立了全功率换段的排量调节模型，进行了主动建压过程的排量比调节动态特性仿真及试验研究，获得排量主动调节控制规律。建立了功率过渡模型，研究了油液含气量对目标段建压时间的影响规律；开展闭式液压回路模型辨识与试验研究。提出了基于直接逆控制的排量控制方法，通过仿真与试验对比研究，验证了控制方法的可行性，实现了全功率换段中功率过渡的主动精益控制。.开展了全功率换段时机非对称偏差特性仿真分析与试验研究，获得了换段时机超前、滞后对离合器滑磨过程和前稳定阶段状态的影响规律；采用全局敏感度分析法对目标段压力预测模型简化获得了实时预测模型。建立了全功率换段控制策略，硬件在环试验表明该控制策略能识别换段时机、预测目标段状态，实现全功率换段。.在完成项目研究内容基础上，针对装载机合作开发了HMT样机和控制器，提出了考虑作业效率的分阶段速比调节策略，仿真分析与试验结果表明，HMT的无级调速特性可增大动力系统的节油优化空间；所开发控制器能够进行段内调速与换段控制。.项目研究成果揭示了液压机械全功率换段机理，提出了其控制方法。搭载HMT的装载机等高动态作业车辆，存在工况识别、工况转换协调、动力系统一体化控制、动态工况下快速换段等关键科学问题，亟待进一步深入研究。