【作者】 阚超；

【导师】 孔祥东； 高英杰；

【作者基本信息】 燕山大学 ， 机械电子工程， 2007， 博士

【摘要】 电液比例控制技术,是在以开环传动为主要特征的传统液压传动技术和以闭环控制为特征的电液伺服控制技术基础上,为适应一般工程系统对传动与控制特性或有所侧重或兼而有之的特别要求,从20世纪60、70年代开始,逐步发展起来的流体传动与控制领域中一个具有旺盛生命力的新分支。因此有可能在一般工业应用中以其抗污染和节能等优势来取代伺服阀。但目前对电液比例技术的掌握和运用,不论是理论上还是实践上,都有很多问题需要研究﹑探讨﹑总结与提高。因此该类比例控制系统的研究,对电液比例控制技术的发展和完善具有重要的理论意义和应用价值。本论文以寻找比例控制可替代伺服控制的条件为目的,以压力控制系统为研究对象,以实验为基础,从辨识方法﹑系统本身特性差别和采用不同控制策略时系统性能差别三方面对比例系统与伺服系统展开分析与研究,以揭示比例控制与伺服控制的异同点,为更加科学﹑更为合理地运用伺服与比例控制技术提供参考。首先,以材料试验机电液比例与伺服压力控制系统为研究对象,对两种系统的辨识输入信号﹑采样时间的选取,数据如何预处理,系统模型结构形式的确定,模型结构参数的获得,选择适当的参数辨识方式辨识获得系统数学模型以及辨识模型准确性的验证等问题进行深入分析。同时,通过比较在不同输入信号不同模型结构形式和辨识方式下所得辨识模型的效果,确定了适合本试验对象的系统辨识方法。在确定系统数学模型的基础上,运用遗传算法对系统的开环参数进行求解,得到准确的系统开环参数。其次,在保证其它参数相同、不附加任何控制策略、仅控制元件不同的条件下,对材料试验机伺服与比例两个系统分别进行系统综合性能(稳定性﹑快速性﹑准确性)的分析和比较,找出造成两系统性能差别以及影响压力控制系统性能的主要系统参数,依据理论与实验结果,研究在一定条件下,比例系统替代伺服系统进行压力控制的可能性。为了避免在单一控制系统上分析系统特性所得结论可能产生的片面性,在进行特性分析比较时,还同时以挖掘机斗杆臂油缸压力控制系统为另一研究对象,对其系统特性进行了分析。综合两种研究对象的分析结果,对在不同研究对象和不附加控制策略情况下,对比例系统与伺服系统的特性进行了比较研究。研究结果显示,在一定工况条件下,比例系统的特性基本可以实现伺服系统的控制效果。最后,以材料试验机压力控制系统为实验对象,依据通过系统辨识获得的数学模型以及遗传算法求得的系统参数,采用PID控制算法和MRAC控制算法对材料试验机电液比例压力控制系统和电液伺服压力控制系统进行了计算机仿真并在材料试验机系统上进行了实验研究。对比两种压力控制系统在PID控制算法和MRAC算法作用下的系统性能,进一步分析了电液伺服压力控制系统与电液比例压力控制系统在实际系统中相互替代的可行性。实验结果表明,材料试验机伺服系统控制性能略优于比例系统并给出可以采用比例系统实现控制性能的适用条件。更多还原

【Abstract】 Electro-hydraulic Proportional Control has been developing into a vigorous new branch in the field of the Fluid Power and Transmission Control since 1960s. It aims at meeting the special requirements of common engineering systems to emphasize either the traditional fluid transmission technique, which takes open-loop transmission as typical characteristic, or apply electro-hydraulic servo control technique, whose major characteristic is closed-loop control, or take advantage of both of the techniques. It is possible to replace servo valves with the Electro-hydraulic Proportional Control technique considering its advantages such as low cost, antipollution and energy-saving. However, at present, Electro-hydraulic Proportional Control technique needs further study since there are still many problems theoretically and practically. The researches on any kind of Proportional Control techniques will promote and enhance the development of Electro-hydraulic Proportional Control Technique.Targeting at the conditions for replacing servo control with proportional control, taking concrete pressure control system as the research subject, the study researches on proportional system and servo system from the aspects of identification method, the systems’characteristics and the different performances because of the different control strategies and different working conditions. The objective of the study is to figure out the similarities and differences between proportional control and servo control to shed light on the application of the two control techniques.Taking the material testing machine electro-hydraulic proportional pressure control system and servo pressure control system as research subjects, the dissertation sets out to compare and analyze the two systems according to the selections of input signals and sampling time, data processing methods, acquisition of the model structure style parameters, the right identification styles to acquire the mathematical models, and the accuracy of the identified mathematic models. At the same time, based on the comparative and contrastive study on different outputs with different identified mathematic models when inputting signals, with different model structure styles or various identification methods, it finds out the best identification method which is fit for the research subject. On basis of the identified mathematic models, using Genetic Algorithms, the dissertation obtains correct system open-loop parameters.Then, when making sure that all the conditions are the same except for the control element, it compares and analyses the stability, rapidity and accuracy of material testing machine proportion and servo systems, to find out the major parameters which lead to the performance differences of the two systems and which affect the performances of pressure control system. According to theory background and experiment results, it further studies the possibility of replacing servo system with proportional system under certain conditions. In order to avoid unilateral result when analyzing the characteristics of only one control system, the dissertation takes excavator arm cylinder pressure control system as the other research subject. Synthesizing the research consequences of the two subjects, it compares the system characteristics of the proportion and servo systems. It is concluded that under some kinds of working conditions the proportion system can realize the same control effects with that of the servo system.Finally, with the material testing machine as the research subject, using the identified mathematic models and the parameters, adopting PID control and MRAC as control strategies, the dissertation simulates the material testing machine electro-hydraulic proportional pressure control system and the material testing machine electro-hydraulic servo pressure control system. Then experiments are conducted on material testing machine. The study compares the performances of the two systems using both PID control and MRAC, and analyses the practicability of substituting electro-hydraulic servo pressure control system with electro-hydraulic proportional pressure control system in practical systems. The experiments shows that the servo system is superior to the proportion system under this experiment situation. The dissertation point out that proportion system can be applied to realize the proper conditions of controlling system performances.更多还原