【作者】 王静；

【导师】 杨华勇； 龚国芳；

【作者基本信息】 浙江大学 ， 机械电子工程， 2009， 博士

【摘要】 液压传动与控制系统具有抗负载的刚度大、执行器的功率-重量比大的突出优点,已广泛地应用在各个领域中。随着对液压系统的功率和响应时间的要求不断提高,如何提高液压系统的性能一直是一个学科研究的热点问题。液压控制系统的频宽主要受液压动力机构的限制,即为液压固有频率ω_h和液压阻尼比ξ_h所限,而系统的稳定性也需要用足够大的ω_h和ξ_h值来保证。油液的弹性模量决定着液压固有频率,油液的粘度直接影响液压阻尼比。而油液的弹性模量是一个很难确定的量,油液的粘度随温度变化非常明显,一直是一个理论分析与计算的软参数。本文以对接机构综合试验台运动模拟器液压控制系统为选题,着重对油液弹性模量的在线测量和大功率液压系统的油液温度控制进行了研究。油液弹性模量的在线测量中,定义法是一种最直接最可靠的方法。论文从提高定义法的测量精度入手,提出了从测试腔直接提取测量信息的方法,以克服摩擦力的干扰,针对油液弹性模量的影响因素多、测量值变化大不稳定的特点,系统而全面的分析了测试腔形变、泄漏、压缩升温等的影响并采取措施减少其对测量值的干扰,测量精度达到3%。利用该测量装置首次实验研究了系统进气前后和系统抽真空前后油液弹性模量变化,间接反映出油液含气量的变化。针对油温控制纯滞后、参数时变的特点,提出了一套油温控制的方法,利用三通比例水阀分水原理控制通过回油板式换热器的冷却水流量并结合参数自整定模糊PID控制算法精确控制油液温度,仿真和实验结果表明系统油温稳定在45±1℃范围内。对大通径插装阎控制供油压力的稳态特性和动态特性进行的仿真和实验研究,得到了参数变化对性能指标的影响规律,为提高大流量液压源供油压力的性能指标提供了参考依据。论文主要研究内容如下:第一章,介绍了空间交会对接及其仿真技术国内外研究发展概况和大型装备液压系统集成技术国内外发展现状。阐述了油液弹性模量测量和油液温度控制的研究现状。提出了本课题的研究内容以及完成论文所要进行的研究工作。第二章,简要介绍了对接机构综合试验台的结构及组成。设计了运动模拟器液压系统,包括动力机构和液压源两大部分的组成、原理和主要参数等。针对液压源设计中的几个关键技术,油温控制、抽真空除气、油液弹性模量测量和供油压力调节,给出了解决方案并对其原理进行了阐述。第三章,在建立油液弹性模量的理论模型基础上,对影响油液弹性模量的因素进行了分析。详细分析了油液弹性模量测量装置的精度问题。对掺混气体对油液弹性模量的影响、混气油液弹性模量随压力的变化以及油温对油液弹性模量的影响进行了实验研究。并对测量系统压力波动、测量压力以及泄漏量和气泡溶解度对测量结果的影响进行了实验分析。第四章,在建立温度被控对象的数学模型的基础上,分析了油液温度控制的难点,提出了基于参数自整定模糊PID的油液温度控制策略,并进行了参数自整定模糊PID控制器的设计以及油液温度控制的仿真分析。在对接机构综合试验台运动模拟器液压源设备上进行了油液温度控制实验。仿真和实验结果显示,采用参数自整定模糊PID控制算法对液压系统油液温度进行控制,油温稳定在45±1℃范围内。第五章,利用AMESim建立了压力控制插装阀的仿真模型。通过分析选择了几个与压力控制稳态特性相关的参数进行仿真研究。并对主阀芯弹簧、主阀前腔容积、导阀弹簧和阻尼对压力动态特性的影响进行了仿真分析。在对接机构综合试验台运动模拟器液压源设备上进行了压力控制实验。第六章,概括了全文的主要研究工作和成果,并展望了今后需进一步研究的工作和方向。更多还原

【Abstract】 Hydraulic transmission and control system has been widely used in various fields for its great load stiffness and high power-to-weight ratio.With the development of higher power and faster response of hydraulic system,the improvement of system performance is always on the agenda of research community.In all performance parameters,the frequency width and the stability of the hydraulic system are two essential characteristics.They are both limited by hydraulic natural frequencyω_h and damping ratioξ_h.The hydraulic natural frequencyω_h is determined mainly by bulk modulus of oil,and the damping ratioξ_h is mostly affected by viscosity of oil.The bulk modulus and the viscosity of oil are difficult to determine,as they are varying with the temperature and pressure obviously.With the increase of hydraulic natural frequencyω_h,the bulk modulus of oil should be improved and tested.In order to get a steady damping ratioξ_h the temperature of oil must be kept constantly.The techniques of oil bulk modulus monitoring on-line and oil temperature precision control are studied in detail in this thesis.For instance,the researches have been done on the motion simulator for a docking mechanism comprehensive test-rig which has an electro-hydraulic servo system required high flow and high performance.There are several ways for oil bulk modulus to be monitored on-line,among them the method of definition is most direct and reliable.To improve the test accuracy,an installation was invented and discussed according to the definition of oil bulk modulus,in which information of pressure and displacement was directly extracted from test chamber.The effects of test chamber deformation,leakage and temperature on measurement accuracy were analyzed in this thesis.The measurement accuracy reached as high as 3%because the approaches were effective.Using this measurement device,experiments were carried out on bulk modulus of hydraulic oil and a set of values of oil bulk modulus with different air contents were made for the first time.On account of characters of time delay and time-varying parameters in oil temperature control,a set of control method was proposed. The proportional water valve was used to control the flow rate of cooling water and the parameter self-tuning fuzzy PID control algorithm was used to control the opening of the valve.The simulation and experiment results indicated oil temperature maintaining in 45±1℃.The study of steady-state and dynamic properties of large-bore pressure control cartridge valve identified the rules of performance changing with structure parameters.The result provides reference to improvement of pressure performance in high flow hydraulic systems. The main contents of each chapter are summarized as follows:In chapter 1,the history and current research status of the rendezvous and docking technology and the simulator test rig are reviewed based on a lot of publications and conference papers.The research statuses of oil bulk modulus measuring and oil temperature control are also presented.Accordingly,the research and the goal of the project are brought forward.In chapter 2,the construction and composition of docking mechanism comprehensive test-rig is briefly introduced.The hydraulic system of motion simulator is designed, including composition,principle and main parameters of power mechanism and hydraulic resource.Several key technologies in hydraulic resource design,such as oil temperature control,vacuum degassing,oil bulk modulus measuring and oil supply pressure adjustment, are stated and the principles are explained.In chapter 3,based on the theoretical model of oil bulk modulus,the influence factors are considered.The accuracy of oil bulk modulus measurement device is analyzed in detail. Experiment researches on the effects of entrained air on oil bulk modulus,the changes of oil bulk modulus with pressure and the effects of temperature on oil bulk modulus are made. The effects of pressure fluctuation in test system,leakage and air solubility on measurement results are analyzed with experiments.In chapter 4,based on the mathematical model of temperature control object,the difficulties of oil temperature control are analyzed.A kind of oil temperature control strategy based on parameter self-tuning fuzzy PID control method is put forward.The parameter self-tuning fuzzy PID controller is designed.Oil temperature control experiment is made on facilities of hydraulic resource of motion simulator.The simulation and experiment results show oil temperature maintaining in 45±1℃.In chapter 5,the simulation model of pressure control cartridge valve is established with AMESim.The relevant parameters with steady characteristics are analyzed.The effects of spring in main spool,volume ahead main spool,spring in pilot valve and damping on dynamic characteristics are observed.Pressure control experiment is made on facilities of hydraulic resource of motion simulator.In chapter 6,some conclusions are given and some new views are put forward in the future.更多还原