【作者】 张明柱；

【导师】 周志立； 李言；

【作者基本信息】 西安理工大学 ， 车辆工程， 2007， 博士

【摘要】 液压机械无级变速传动(HMCVT)是一类由液压功率流与机械功率流联合的双功率流传动形式，良好的原理设计与先进的控制技术相结合，能够实现大功率、高效率无级变速传动，在大功率车辆上表现出良好的应用前景。论文针对HMCVT在大功率拖拉机上的应用，围绕原理设计、特性分析、建模仿真、无级变速和换段规律、工程应用控制策略、控制技术等方面进行了研究。在分析HMCVT的组成原理、基本类型和传动特性的基础上，结合农业拖拉机的作业特征及其对传动系统性能的要求，开发了一种新型的多段HMCVT传动原理。新型多段HMCVT具有无级变速范围宽，在拖拉机的主要工作速度段传动效率高的突出优点。研究了HMCVT的传动比、转矩、功率流及效率等特性的分析计算方法和装备HMCVT拖拉机的牵引特性分析计算原理和表达方法，为车辆液压机械无级变速器的原理设计、性能分析、装车匹配及控制技术研究奠定了理论基础。以开发多段HMCVT控制系统为主要目的，采用模块化方法建立了具有双流复合传动特征的多段HMCVT数学模型以及拖拉机整车动力传动系统数学模型。建模中，将多段HMCVT机械传动构件简化为具有集中质量和阻尼的刚性系统，在满足控制仿真要求的基础上简化了模型结构。针对多段HMCVT状态多变的特征，根据有限状态机原理，应用Matlab软件开发了多段HMCVT连续无级变速和换段的多状态转换仿真系统。通过仿真分析，提出了提高传动比调节速度的变增益PID控制原理和消除车速波动的调速位置变化率前馈控制原理。验证了建模方法的有效性，为快速研究各种控制策略提供了仿真试验条件。获取最高生产率是设计拖拉机的主要目标，据此，针对多段HMCVT这类具有无级变速和有级换档双重特征的无级变速器，制定了基于牵引功率最大的无级变速和换段规律。指出要实现拖拉机的牵引功率最大，需要调节HMCVT的传动比，使发动机工作在与调速位置对应的最大功率点上。制定了使HMCVT优先工作在高效率段从而提高拖拉机牵引功率的换段原理。提出了用调速位置、发动机转速、工作段号和实际传动比作为控制参数的工程应用控制策略，论述了无级变速及换段规律中发动机工作转速和换段转速的计算原理。仿真表明了工程应用控制策略的有效性，为控制系统的开发提供了理论依据。分析了影响拖拉机经济性的主要因素，指出因为多段HMCVT在不同传动比下效率差别较大，保证发动机的燃油消耗率与HMCVT传动效率之比g_e／η_b最小，是实现拖拉机经济性最佳的基本要求。提出了在HMCVT传动比和发动机转速二元协同控制下，保证g_e／η_b最小和车速稳定的拖拉机经济性最佳无级变速和换段规律。制定了以目标车速、发动机转速、油泵齿条位移、最佳传动比和滑转率为控制参数的工程应用控制策略。研究了用滑转率修正系数，对不同地面和垂直载荷条件下的滑转率进行实时修正的方法，实现了在各种工况下拖拉机的实际速度与目标速度的一致。给出了最佳传动比的优化计算原理和详细计算流程，制定了避免循环换段的换段规则。仿真验证了无级变速规律的合理性和工程应用控制策略的有效性。在仿真分析和变速规律研究的基础上，根据建立的HMCVT传动拖拉机工作模式，开发了多段HMCVT液压和电控系统。由于排量比控制决定传动比控制的精度，论文提出一种排量比模糊-PID动态加权综合控制原理。进行了传动比控制台架试验，达到了快速性和准确性好、动态跟踪误差小的效果。该研究成果为多段HMCVT装车应用奠定了基础。更多还原

【Abstract】 Hydro-mechanical continuously variable transmission (HMCVT) combines the hydrostatic power flow and mechanical power flow to realize stepless speed change with high efficiency and large power, so it has many advantages in the power train system of heavy vehicles. To develop and utilize the HMCVT in large power tractors, This thesis studies its principle and characteristics, modeling and simulation, stepless speed change and range shift law, control strategy and implementation method, as well as electronic control technology.Based on the analysis of compositive principle, fundamental types and kinematic characteristics, according to the work feature of tractors and the need of power train system, a novel principle of multi-range HMCVT is developed, which has a wide stepless speed change range and high efficiency in the main work speed field of tractors. The analysis methods of transmission ratio, torque, power split ratio and efficiency characteristic are derived. For the tractive characteristic of tractors equipped multi-range HMCVT, an analysis and drawing method is represented. These research will establish the theory foundation of HMCVT on the design, characteristic analysis, match method and control technology.For the development of control system, with the modular method, the model of multi-range HMCVT and tractor’s powertrain system are established. The mechanical components are simplified as lumped mass-dashpot system to meet the need of control simulation and reduce the complexity of model. Based on the principle of finite state machine(FSM) and software of MATLAB, a multimode transfer simulation system of multi-range HMCVT is developed, which can simulate the control process of continuously speed change and range shift. By control simulation and analysis, it is presented that a variable parameters PID control principle which can increase the adjusting speed of transmission ratio, and that a throttle change rate forward control principle which can avoid the fluctuation of vehicle speed. The validity of modeling method is proved by bench test. A simulation test condition is created for the development of control strategy.According to the main purpose of obtaining highest productivity for tractors, based on getting largest tractive power, a speed change and range shift law for the multi-range HMCVT is represented. A control strategy of engineering implementation is established, which uses throttle position, engine speed, range number and real transmission ratio as the control parameters. It is expounded that the calculating method of engine work speed and range shift speed in the speed change and range shift law. The control strategy of engineering implementation is proved to be validity by simulation test, which is the theory support to develop the control system of multi-range HMCVT.By analyzing the main influencing factors of economical efficiency for tractors, it is represented that the rate of fuel consumption and the multi-range HMCVT’s efficiency (ge/ηb) must be keep least to realize the highest economical efficiency, because the efficiency of multi-range HMCVT changes in a wide field with the transmission ratio. Based on getting the highest economical efficiency of tractors, a speed change and range shift law for the multi-range HMCVT is presented, which can ensure ge/ηb to be the least and the vehicle speed to be correct on the condition of coordinate control of transmission ratio and engine speed. A control strategy of engineering implementation is established, which uses object vehicle speed, engine speed, injection pump gear rack position, optimal transmission ratio and slip rate as the control parameters. The real vehicle speed is held to be equal to the object vehicle speed on any work conditions by real time adjusting the slip rate that is adjusted by slip rate correction factor on different condition of soil and vertical load. The calculating method of optimal transmission ratio is derived. A range shift law is made which can avoid the recirculation range shift. The control strategy of engineering implementation is proved to be validity by simulation test.According to the established work modes of tractors equipped with HMCVT, the hydrostatic and electronic control system of multi-range HMCVT is developed. Because the control precision of transmission ratio is decided by the displacement ratio, a weight dynamic change fuzzy-PID integrated control principle for the displacement ratio control is presented. The control of transmission ratio is done by this principle in the bench test. The result showed that the rapidity and accuracy is good and the dynamic follow error is small.更多还原