【作者】 张强；

【导师】 魏建华；

【作者基本信息】 浙江大学 ， 机械电子工程， 2017， 博士

【摘要】 液压机,特别是大吨位的液压机,有必要具备多种工作模式,以满足不同类型产品的生产需求。电液控制系统作为液压机的核心组成部分,其工作性能不仅决定了液压机的工作特性,而且显著影响到被压制产品的质量;因此,希望液压机具备多种工作模式,首先必须要求液压机的电液控制系统具备多种工作模式并存的能力。然而,以往的研究中很少有学者针对液压机的电液控制系统,特别是大吨位液压机的多模式电液控制系统展开深入的研究。本论文将以某大型锻造液压机为研究背景,以大吨位液压机的多模式电液控制系统为具体的研究对象,从核心元件、外负载补偿策略、非线性控制策略等方面出发,对大吨位液压机多模式电液控制系统的关键技术进行系统的研究。本论文共六章,每一章的摘要如下:第一章,概述了液压机的特点及分类、国内外研究现状以及未来的发展趋势,并指出多模式并存是未来大吨位液压机设计中必然考虑的一个问题,继而详细介绍了与大吨位液压机多模式电液控制系统相关的四大关键技术,即电液比例插装阀技术、液压机的外负载建模技术、基于干扰观测器的外负载补偿技术以及电液控制系统的控制技术,并指出了现有技术应用于多模式电液控制系统所存在的问题;最后,阐述了本课题的来源及研究意义,介绍了本论文的研究内容。第二章,针对某一款单反馈比例插装阀(single-feedback proportional cartridge valve, SFPCV)展开系统的研究。首先介绍了 SFPCV的工作原理,然后根据相关的性能指标对SFPCV的主要零部件进行设计,并建立了 SFPCV的非线性数学模型;根据SFPCV的非线性数学模型,建立了 SFPCV的MATLAB/AMESim联合仿真模型,并通过仿真数据与样机实验的对比验证了所建联合仿真模型的正确性;依托所建联合仿真模型,进一步研究了相关结构参数对SFPCV工作性能的影响规律,从而为SFPCV的改进提供依据;根据仿真结果并结合实验,对SFPCV的主要结构参数及控制策略进行了改进。实验结果表明:所研发SFPCV的相关动静态性能达到了设计指标,可以替代进口,应用于大吨位液压机的多模式电液控制系统中去。第三章,首先介绍了某大型锻造液压机多模式电液控制系统的工作原理,针对其与其他类型液压机所共有的、用以完成一般产品压制成形的低速工进系统以及其所特有的蓄能器辅助快锻系统,搭建了相应的实验平台。为了便于后续基于数学模型的非线性控制器设计,建立了实验平台的数学模型,并通过开环仿真及实验的对比验证了所建数学模型的正确性。考虑到后续的研究中需要用到实验平台中的加载液压缸对驱动液压缸进行模拟加载,还进一步研究了加载液压缸的加载控制算法。实验结果表明:采用模糊PID控制算法能够在保证静态加载精度与传统PID控制算法相仿的前提下,显著改善加载的动态过程。第四章,针对未知载荷作用下的低速工进系统高性能运动控制展开系统的研究。首先提出了两种不同的干扰观测器对液压机在低速工进阶段所受到的外负载进行在线估计和补偿:第一种干扰观测器基于外负载可分段线性化这一特点而提出,它的参数自适应由观测器误差和运动跟踪误差同时驱动,本文中把它称为“扩展的分段干扰观测器 ”(extended piecewise disturbance observer, EPDO);第二种干扰观测器基于模糊系统可以以任意精度逼近未知非线性系统这一特点而提出,它的参数自适应同样由观测器误差和运动跟踪误差同时驱动,本文中把它称为“扩展的模糊干扰观测器 ”(extended fuzzy di sturbance observer, EFDO)。针对电液控制系统固有的强非线性特性以及各种模型不确定性,并且考虑到负载口独立控制的低速工进系统的多输入-单输出特性,提出了 一种非线性层叠控制器作为低速工进系统的运动控制器:该非线性层叠控制器的位移跟踪环基于滑模控制而设计,以期望的位移、速度、加速度以及加加速作为输入,以期望的驱动力作为输出;该非线性层叠控制器的压力跟踪环基于backstepping技术而设计,使系统的实际驱动力能够精确跟踪位移跟踪环得出的期望驱动力。针对负载口独立控制的低速工进系统的静态工作点选择问题,提出了一种适用于液压机的“最小等效负载准则” (minimum equivalent load criterion,MELC):该准则把驱动缸有杆腔(相当于液压机的回程缸)提供的力看作等效外负载的一部分,随着估计外负载的增大逐渐减小驱动缸有杆腔的期望压力,并保证最小的等效外负载大于滑块的重力;从而能够最大限度地挖掘出液压机的驱动能力,并且保证液压机在任何状态下都不会出现失稳现象。仿真和实验结果表明:采用本文所提出的非线性层叠控制器,并结合本文所提出的EPDO或EFDO,能够使得液压机在低速工进过程中精确跟踪给定的期望位移曲线;在EPDO或EFDO的作用下,估计的外负载能够在观测器误差和运动跟踪误差的驱动下精确跟踪低速工进过程中所受到的实际外负载;此外,在本文所提出MELC的作用下,控制器能够根据估计外负载的大小,自动改变驱动缸有杆腔的期望压力,从而可以尽可能地挖掘出液压机的驱动能力,提高其位移跟踪性能。第五章,针对蓄能器辅助快锻系统的高频次、高精度、平稳位移控制展开系统的研究。首先从蓄能器辅助快锻系统的基本结构出发,进行核心元件的参数匹配设计。继而在考虑蓄能器辅助快锻系统的多输入-单输出特性,以及蓄能器辅助快锻系统所受到的各种匹配或者不匹配模型不确定性的基础上,提出了 一种最优能量分配-自适应鲁棒控制(optimal energy distributed adaptive robust control,OED-ARC)策略作为蓄能器辅助快锻系统的运动控制器:在OED-ARC控制器的设计中首先把“集总流量”看作系统的等效输入,使得系统的输入输出自由度相等;然后根据期望的运动轨迹,利用backstepping技术推导出“集总流量”的期望值;最终再根据“最优能量分配准则”从“集总流量”推导出两个控制阀的实际控制量。此外,在OED-ARC控制器的设计中还采用了 一种基于蓄能器简化数学模型的“非线性阻尼调节器”来对蓄能器数学模型中存在的非线性参数不确定性进行补偿。仿真和实验结果表明:采用本文所提出的OED-ARC控制器可以使蓄能器辅助快锻系统获得确定的动态特性和静态跟踪精度,即使系统中存在各种匹配或者不匹配的模型不确定性;此外,采用本文所提出的“非线性阻尼调节器”不仅可以较好地补偿蓄能器的非线性参数不确定性,还可以起到微调运动控制效果的作用,增加了系统的调节自由度。第六章,总结了本论文的研究工作;阐述了本论文的主要创新点;并对后续的研究工作进行了展望。更多还原

【Abstract】 It is necessary for the hydraulic press, especially the large-tonnage hydraulic press, to have a variety of operating modes to meet the production requirements of different types of products. As the core part of hydraulic press, the working performance of electro-hydraulic system not only dertermines the working characteristics of hydraulic press, but also significantly affects the quality of the products to be suppressed. Therefore, the electro-hydraulic system of hydraulic press must have the ability of various operating modes coexist to make the hydraulic press have a variety of operating modes. However, few scholars have deeply studied the electro-hyarulic system of hydraulic press, especially the multi-mode electro-hyarulic system of large-tonnage hydraulic press in the past. This thesis takes the multi-mode electro-hydraulic system of large-tonnage hydraulic press as the specific research object, with a large froging hydraulic press as the research background. Systematic researches will be conducted to study the key technologies of the multi-mode electro-hydraulic system of large-tonnage hydraulic press, which include the core component, the external load compensation strategy, the nonlinear control strategy,and so on.The outline of this thesis is as follows:In chapter 1, the characteristics and classification, the research status at home and abroad, and the development trend of hydraulic press are summarized. It is then pointed out that the coexistence of multiple operating modes will be inevitably considered in the future design of large-tonnage hydraulic press. The four key technologies of the multi-mode electro-hydraulic system of hydraulic press are introduced, which include the electro-hydraulic proportional cartridge valve technology, the external load modeling technology, the disturbance observer-based external load compensation technology and the control technology of electro-hydraulic system. The problems of existing technologies applied to the multi-mode electro-hydraulic system of hydraulic press are also pointed. Finally, the origin and significance of this research are expounded, and the research contents are introduced.Chapter 2 conducts systematic research aiming at the single-feedback proportional cartridge valve (SFPCV). The working principle of SFPCV is firstly introduced, then the main components of SFPCV are designed according to the relevant performance indexes, and the nonlinear mathematical model of SFPCV is also established. According to the nonlinear mathematical model of SFPCV, the MATLAB/AMESim co-simulation model of SFPCV is established, whose correctness is proved by comparison between the simulation data and the prototype experiment.Based on the co-simulation model, the influence of the relevant structural parameters on the performances of SFPCV is further studied,which provides the basis for the optimization of SFPCV. According to the simulation results together with the experiments, the main structural parameters and control strategy of SFPCV are optimized. The experiment results illustrate that the dynamic and static performances of the developed SFPCV has reached the design targets; the developed SFPCV can replace imported, and be applied to the multi-mode electro-hydraulic system of large-tonnage hydraulic press.In chapter 3, the working principle of the multi-mode electro-hydraulic system of a large forging hydraulic press is firstly introduced. Experiment platforms are then established for the slow feeding system and accumulator assisted fast forging system of the hydraulic press. In order to facilitate the nonlinear controller design,mathematical models of the experiment platforms are established, whose correctness are verified by the open-loop simulation and experiment comparison. Control algorithm of the loading cylinder is further studied considering that the loading cylinder is applied to load the driving cylinder in the following studies. The experiment results show that the fuzzy PID control algorithm can significantly improve the dynamic response of the loading process under the premise that the steady loading accuracy is similar with the traditional PID control.Chapter 4 conducts systematic research for the high-perfomance motion control of slow feeding system under unknown load. Firstly,two different disturbance observers (DOBs) are proposed to estimate and compensate the external load of the hydraulic press in the slow feeding stage. The first DOB is proposed based on the piecewise linearization characteristic of the external load, its parameter adaptation is driven by the observer error and motion tracking error together. In this thesis, it is called "extended piecewise disturbance observer"(EPDO). The second DOB is proposed based on the characteristic that a fuzzy system can approximate an unknown nonlinear system with any precision, its parameter adaptation is also driven by the observer error and motion tracking error together. In this thesis,it is called "extended fuzzy disturbance observer"(EFDO). Aiming at the inherent strong nonlinearities and model uncertainties in the electro-hydraulic system, and considering the multiple-input single-output characteristic of the individual metering slow feeding system, a nonlinear cascade controller is proposed as the motion controller of the slow feeding system. The motion tracking loop of the nonlinear cascade controller is designed based on the sliding mode control with the desired displacement, velocity,acceleration and jerk as inputs and the desired driving force as output. The pressure tracking loop of the nonlinear cascade controller is designed based on the backstepping technique, so that the actual driving force of the system can precisely track the desired driving force derived from the motion tracking loop. The "minimum equivalent load criterion"(MELC) is proposed to solve the static working point selection problem of the individual metering slow feeding system. The MELC regards the force provided by the rod chamber of driving cylinder as a part of the equivalent external load. With the increase of the estimated external load, the MELC will gradually reduce the desired pressure of the rod chamber of driving cylinder under the premise that the minimum equivalent external load is bigger than the gravity of the slider. By doing this, the maximum driving ability of hydraulic press is digged out,and ensures that the hydraulic press will not appear instability phenomenon in any state. Simulation and experiment results demonstrate that the nonlinear cascade controller, together with the EPDO or EFDO, can make the hydraulic press precisely track the desired displacement curve during the slow feeding stage; with the EPDO or EFDO, the estimated external load can precisely track the actual external load;furthermore, with the proposed MELC, the controller can automatically change the desired pressure of the rod chamber of driving cylinder, which can dig out the driving ability as much as possible to improve the displacement tracking performance.Chapter 5 conducts systematic research for the high-frequency, high-precision and stable displacement control of the accumulator assisted fast forging system.Parameter matching design is firstly conducted for the core components from the basic structure of the accumulator assisted fast forging system. Considering the multiple-input single-output characteristic of the accumulator assisted fast forging system, and the matched or mismatched model uncertainties associated with the accumulator assisted fast forging system, an optimal energy distributed adaptive robust control (OED-ARC) is proposed as the motion controller. In the design of OED-ARC controller,the "lumped flow" is firstly regarded as the equivalent input to make the input degree of freedom and output degree of freedom equal; according to the desired motion trajectory,the desired value of the "lumped flow" is then derived using the backstepping technique; control law of each control valve is finally derived from the "lumped flow" using the "optimal energy distributed criterion". In addition,in the design of OED-ARC controller,a "nonlinear damping regulator" is adopted based on the simplified mathematical model of the accumulator to compensate for the nonlinear parameter uncertainy associated with the accumulator model. Simulation and experiment results illustrate that the proposed OED-ARC controller can make the accumulator assisted fast forging system achieve determined dynamic response and static tracking accuracy even if the system is subjected to various matched or mismatched model uncertainties; what’s more, the proposed "nonlinear damping regulator" can not only compensate for the nonlinear parameter uncertainty of the accumulator, but also fine-tune the motion control performance to increase the degree of freedom for adjustment.Chapter 6 summarizes the research work of this thesis, describes the main innovations of the research, and prospects the future work.更多还原