摘要
随着液压技术的进步,高效节能的泵控系统应用得越来越广泛,并将成为未来液压领域发展的重要方向。泵控系统能量损耗少,相应系统的发热量亦最少,尤其适用于大、中功率的调速系统,另外泵控系统的负载刚度大,液压元件可视为线性结构,其增益和阻尼比相对恒定。在泵控系统中,变量泵作为泵控系统的动力元件和控制元件,它的动态响应能力是关系泵控系统运动品质的一个重要标准,如何提高变量泵的响应速度与精度是改善泵控系统性能的关键。而仿真技术的出现,大大加快了工程技术人员对新产品的研制开发进程,在对液压系统进行设计、分析和改进时,计算机动态仿真具有重要的价值。
本课题研究工作主要包括:
1.本文以JB63系列径向柱塞排量变量泵为研究对象,基于弹簧—位移—力反馈原理设计变量泵的变量机构,并在MATLAB软件的SIMULINK环境中建立了变量泵仿真模型。分析了泵的动态特性,系统的研究了变量机构的结构参数和变量泵的某些参数对变量泵响应特性的影响,从中获得了有关变量泵变量机构运动的规律性认识,为实现新型径向柱塞变量泵输出工作参数的电液数字控制提供了理论依据。
2.在许多工程应用领域中要用到大排量的斜轴式变量柱塞泵,但常用的控制形式是恒压和恒功率,这样在使用中会产生较大的能量损失,如果采用改变泵排量的控制原理,不仅可改善系统的控制特性,也可提高系统的能量效率,但由于斜轴式泵变量机构行程长,不容易实现电子闭环控制,提出采用先导式的弹簧—位移—力反馈原理对其进行控制,本文以A7V系列斜轴式轴向柱塞排量变量泵为研究对象,对这一原理在其变量控制机构上的应用进行了分析,建立了控制系统的数学模型,并在MATLAB软件的SIMULINK环境中建立了变量泵变量机构的仿真模型,同时就系统的结构参数对变量控制系统的影响进行了仿真分析。
仿真结果表明,基于先导式的弹簧—位移—力反馈原理控制的径向柱塞排量变量泵和斜轴式轴向柱塞排量变量泵具有良好的动态特性。与电反馈的相比,控制精度虽没有电反馈的高,但这种变量机构结构简单,成本底,控制方便,值得去研究。
With the developing of hydraulic technology, efficient and energy-saving pump control system has gotten great availability. Pump control system is becoming the emphasis of hydraulic system development. The pump-controlled system with little energy wastage and heat can apply to the high and medium power adjustable-speed system . In addition, because the load stiffness is large and gain and damp ratio is relatively constant, the hydraulic elements should be considered as linear structure. As the power and control component, the dynamic characteristic of variable displacement pump is an important reference of pump control system's quality. How to enhance response speed and precision of variable displacement pump is important to improve performance of pump-controlled system. The utility of simulation technology greatly shorten the research and exploitation progress of new products. Computer dynamic simulation is very valuable when hydraulic system is designed, analyzed, and modified.
The main work could be described as follows:
1. Referring to the JB63 series radial piston variable displacement pump, a variable displacement mechanism of variable displacement pump which is developed on the basis of displacement-spring-force feedback principle is designed. The simulation model of variable displacement pump is set up in SIMULINK of MATLAB. It studies systematically the influence of variable displacement mechanism and variable displacement pump parameters to its characteristic dynamic responses, and summarizes the immanent law of the variable displacement mechanism of variable displacement pump system, and provides theoretical basis for the electro-hydraulic control of variable displacement pump.
2. Large displacement bent axis variable displacement piston pump has been widely used in various industrial fields. The constant pressure and permanent power control which will produce energy losses in use is the typical control system styles. If a controlling principle can be adopted to change pump's displacement, it will not only improve the control characteristics, but also increase the efficiency of the system. But due to a long stroke of the variable displacement mechanism and the difficult implementation of electronic close loop control, a principle of pilot type with displacement-force feedback is proposed to control the pump. The application of the principle to the variable displacement mechanism is discussed, the control system mathematical model was built up and the influence of system structure parameters on the variable discharge system is analyzed in the paper.
Simulation results show that the dynamic characteristic of electro-hydraulic proportion controlling variable displacement pump using this displacement-spring-force feedback principle controller is very good. It have more simple structure, low cost, convenient control characteristics comparing with the electric feedback, however, it showed lower control precision.
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