【作者】 胡宏伟；

【导师】 周晓军；

【作者基本信息】 浙江大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 自动变速系统是现代汽车技术发展的重要方向之一,湿式自动离合器是汽车自动变速系统中的重要部件,对其接合控制和接合过程的特性进行深入研究,对于提高我国汽车关键零部件的研发水平,促进国产自动变速器行业发展具有重要的意义。本文针对国内汽车自动离合器技术的发展现状,结合理论研究和实际项目的需要,从提高离合器的接合品质和使用寿命的研究目标出发,沿着优化控制方法和改善设计参数两个研究思路,重点对湿式离合器接合过程动力学建模、接合过程最优控制、接合过程中抖动和稳定性、接合过程中热负荷等方面进行了系统深入的研究。第一章阐述了论文研究的背景和研究的意义,分析了汽车自动离合器的控制、接合过程抖动、接合过程热负荷、离合器试验台等国内外研究现状和目前存在的问题,最后给出了论文的主要研究内容及章节安排。第二章建立了湿式多片离合器接合过程系统动力学模型。首先介绍了自动变速汽车传动系统模型及湿式离合器的结构和工作原理,通过对湿式离合器接合过程的分析,建立了接合过程中汽车传动系统动力学模型,并对模型中的参数进行了分析,最后建立了自动湿式离合器的液压执行机构的力学模型和控制模型。第三章对离合器接合过程优化控制策略以及执行机构跟踪控制方法进行了研究。首先对离合器接合品质进行了研究,指出离合器的接合品质主要与离合器接合过程的摩擦转矩变化有关。然后根据接合过程动力学模型,建立了以摩擦转矩变化率为控制变量的接合过程控制系统的状态空间方程,并以冲击度和滑磨功作为二次型性能指标,通过权重系数来调整控制策略,利用最优控制理论,得到具有干扰矩阵情况下的摩擦转矩最优轨迹。其次,针对摩擦力矩的不可观测以及液压执行机构的非线性,采用滑模控制理论对具有干扰的离合器控制系统设计了滑模控制器,实现对离合器接合最优轨迹的跟踪,提高了控制的精度和控制系统的鲁棒性。最后,以换档品质综合性能系数为适应函数,研究了利用遗传算法对双离合器接合过程的现有控制方案进行参数优化的方法。第四章对离合器接合过程中的抖动机理及接合稳定性进行了研究。首先研究了离合器摩擦力矩及其仿真模型,其次建立了离合器接合过程的4自由度传动系统扭转振动模型,从自激振动的角度,分析了离合器抖动产生的机理。并通过对摩擦系数变化线性化,探讨了离合器接合过程中系统的稳定性。最后通过仿真分析了摩擦系数斜率、静摩擦系数、传动系统阻尼、刚度以及接合压力波动等参数对离合器抖动的影响,为改善离合器摩擦特性以及传动系统设计提供了参考。第五章对离合器接合过程摩擦副的热负荷进行了研究。首先分析了离合器接合过程热流量的产生,建立了离合器轴对称热传导模型和热弹性模型,并确立了边界和初始条件,接着采用有限元方法对温度场和应力场进行耦合求解,并结合离合器接合过程动力学模型,并对某接合工况下的计算结果进行了分析。最后讨论了压力控制方案、转速负载、摩擦副结构和材料参数对热负荷的影响,得到了一些重要的结论,为离合器摩擦副设计提供了有益的参考。第六章对离合器性能试验台设计进行了介绍。首先对试验台的设计要求进行了分析。然后介绍了LHZ型离合器试验台系统组成和试验台原理,重点对电能量回馈、电惯量模拟、温度测量等试验台几个关键技术进行了研究。最后介绍了试验台的软件系统。第七章对全文工作进行了总结,并对接下来的研究工作做了展望。更多还原

【Abstract】 Automatic transmission system is one of the most important developing aspects of automobile technology. Automatic wet clutch is the important component of automobile automatic transmission system. Thorough research of the control of engagement and its dynamic characteristic has great significance of improving the design level of automobile key components and promotion of automatic transmission industry. From the present status of domestic research and the need of the theoretical research and practical project, some key problems were studied to improve engagement quality and its life-span. From the point of the optimal control method and improvement of design parameters, the main work of this dissertation include the dynamic model of clutch engagement, optimal control of engagement process, judder and stability of engagement process ,thermal load of engagement process and so on.In chapter 1, the background of the research work and important significance of the dissertation were discussed. Some crucial techniques involved with the research project, such as automobile automatic clutch control, clutch judder of engagement process, thermal load of engagement process, clutch test bench and etc., were analyzed. Finally, detailed research contents and chapters arrangement were given.In chapter 2, the dynamic model of multi-plate wet clutch engagement was studied in detail.Having introduced structure and principle of wet clutch and model of automobile automatic transmission system, this dissertation has established the dynamic model of vehicle transmission system through the analysis of wet clutch engagement process. The parameters of model were also analyzed to establish mechanical model and control model of hydraulic executive machine in automatic wet clutch.In chapter 3, the optimal control trajectory of automatic clutch and tracking control method were studied. Having investigated the engagement quality of clutch, this dissertation has pointed out that engagement quality of clutch has much to do with the change of friction torque in clutch engagement process. In accordance with the dynamic model of engagement process, this dissertation has established the state-space equation which takes change speed of friction torque as its control variable. The jerk and the dissipated energy were regarded as quadratic performance index, weight coefficient was used to adjust control tactic, friction torque optimal contrail was achieved under disturbing matrix through the usage of optimal control theory. Having aimed at unobservable friction torque and nonlinear hydraulic executive machine, this dissertation has designed the sliding mode controller with the usage of sliding mode control theory. Optimal contrail track of clutch engagement was realized to increase control precision and robustness of control system. Finally, the jerk and the dissipated energy were regarded as fitness function.And the parameter optimization method based on genetic algorithm for present control method in dual-clutch engagement was studied. In chapter 4, the mechanism of clutch judder and engagement stability of clutch engagement process were investigated. Having studied the friction torque and its simulation model, this dissertation has established 4-DOF torsional vibration model of transmission system. The mechanism of clutch engagement judder was analyzed from the perspective of self-induced vibration. The stability of clutch engagement process was discussed through linearization of friction coefficient. In order to improve the friction characteristic of clutch and provide reference for design of transmission system, this dissertation also analyzed the effect through simulation on the clutch judder influenced by friction coefficient gradient, static coefficient of friction, transmission system damping, stiffness, fluctuation of engagement pressure.In chapter 5, friction thermal load of clutch engagement process was studied. Having analyzed produce of thermal flux in clutch engagement process, this dissertation has established axisymmetric heat transfer model and thermoelastic model with certain boundary and initial condition. Coupling solving was operated with FEM method on temperature field and stress field. The calculation result of certain engagement condition was analyzed on the basis of the dynamic model of clutch engagement. This dissertation has also discussed the effect on thermal load influenced by pressure control, velocity load, friction structure, material parameter. Finally, some important conclusions were drawn to provide useful reference for design of clutch friction.In chapter 6, the design of a bench to test clutch engagement dynamic characteristic was introduced. Having analyzed the design requirement of test bench, this dissertation has presented the structure and principle of LHZ clutch test bench. This dissertation mainly studied some crucial technology of test bench such as electricity-feedback, electrical-inertia simulation and friction surface temperature measurement etc. Finally, the software of test bench was presented.In chapter 7, main results and conclusions of this dissertation were systematical summarized, the prospects and study emphases of the future research work were discussed and forecast.更多还原