直拉式冷轧实验机液压张力控制策略研究与应用

发布时间：2018-05-30 21:11

本文选题：直拉式冷轧实验机 + 张力控制　；参考：《东北大学》2015年博士论文

【摘要】：近年来,我国钢铁行业取得了举世瞩目的成就,特别是在冶金工艺模拟研究设备的自主研发方面取得了巨大进展。在成就的背后,也存在着很多问题,如高端实验装备长期依赖进口,缺少自主知识产权,核心技术受制于国外。直拉式冷轧实验机作为冷轧工艺和产品研究开发的关键实验装备,采用左、右两个液压缸对轧件施加张力实现冷轧过程恒张力控制。考虑到在冷轧张力控制过程中多余力位置扰动、强耦合、时变性特点,造成控制难度极大。进口设备多采用复杂液压系统设计,且控制算法黑箱处理。国内在张力控制上多采用常规控制策略,控制效果并不理想。针对上述问题,本文对直拉式冷轧实验机液压张力控制进行了系统的分析研究,设计了新型的液压张力控制平台,基于该控制平台建立完整的控制系统数学模型,针对现有系统在应用过程中存在的问题提出相应的解决办法并成功应用于现场,取得良好的效果。本文的主要研究内容和创新点如下：(1)本文首先从轧件的弹性变形理论出发,结合塑性变形及轧制理论对直拉式冷轧实验机工作过程中的前、后张力进行系统分析,得出影响张力控制精度的关键因素在于轧制过程中控制对象的时变性、多余力扰动以及前后张力间的强耦合作用,常规液压伺服系统难以有效克服上述不利因素。(2)设计一套以张力调节与速度跟踪为主的液压伺服系统和以压力限幅及多余力削减为主的液压比例系统相结合的新型液压硬件控制平台,该平台利用伺服阀的高动态响应特性实现张力闭环控制及轧制速度跟踪；依靠比例溢流阀良好的压力流量特性消除多余力扰动及前、后张力间的强耦合作用。(3)基于伺服阀的流量特性及频响特性,建立伺服阀的传递函数模型并获取模型的关键参数,根据压缩法原理设计一套液压油及软管体积弹性模量的测量实验装置,实测液压油和软管的体积弹性模量,并建立常温下液压油的压力幂指数模型。在前、后张力液压缸的流量连续性方程及力平衡条件基础上,结合轧制过程工艺要求,充分考虑轧件变刚度、前后张力强耦合、外在干扰、液压管道效应、液压缸摩擦及伺服阀非线性等影响因素基础上,搭建被控对象的过程变化模型,为控制策略的仿真研究及实际应用奠定基础。(4)依托本文建立的被控对象数学模型,对不同控制策略进行系统的仿真研究,结果表明：传统的PID控制模式,虽然能获得良好的静态控制效果,但动态性能较差,且容易引起张力的震荡；设计速度前馈加张力反馈的组合式控制策略,可以获得良好静态加载及动态加载特性,但由于该控制策略无法完成自适应调整,随着轧件减薄、张力减小以及轧制速度升高等轧制工况的变化,控制效果变差；在此基础上,提出速度前馈加张力反馈模糊PID组合式控制策略,引入的模糊PID控制器能够实现变工况条件下控制参数的自适应调整,系统响应速度快、精度高、鲁棒性强。(5)将研究结果应用于最大100kN张力加载能力的直拉式冷轧实验机,对几种典型的金属材料进行张力冷轧实验,最大轧制速度达到0.4m/s,单道次最大压下量达到37%,动态张力控制精度均保证在±1.1kN以内。采用高精度液压张力控制技术的直拉式冷轧实验机,可为各种金属材料的张力冷轧工艺开发与研究提供可靠的技术支撑。
[Abstract]:In recent years, China's iron and steel industry has made remarkable achievements, especially in the independent research and development of metallurgical technology simulation research equipment. Behind the achievements, there are also many problems, such as the long-term dependence of high end experimental equipment on import, the lack of independent intellectual property rights, and the core technology being controlled abroad. As the key experimental equipment for research and development of cold rolling process and product, the tension control of cold rolling process is applied by two hydraulic cylinders left and right to realize the constant tension control in cold rolling process. Considering that the multi force position disturbance, strong coupling and time-varying characteristics in the process of cold rolling tension control, the control difficulty is great. The complex hydraulic system is used in the imported equipment. The traditional control strategy is used in the tension control, and the control effect is not ideal. In this paper, the hydraulic tension control of the direct drawing cold rolling mill is analyzed and studied. A new hydraulic tension control platform is designed, and a complete control platform is set up based on the control platform. The mathematical model of the system is made to solve the existing problems in the application process and be applied to the field successfully. The main contents and innovation points of this paper are as follows: (1) first of all, the paper starts with the elastic deformation theory of the workpiece, and combines the plastic deformation and rolling theory to direct drawing cold rolling. The front and rear tension is analyzed systematically in the working process of the experiment machine. It is concluded that the key factors that affect the precision of tension control lie in the time variation of the control object, the disturbance of multi force and the strong coupling between the front and back tension during the rolling process, and the conventional hydraulic servo system can not effectively overcome the disadvantages mentioned above. (2) a set of tension adjustment is designed. A hydraulic servo system based on speed tracking and a hydraulic hardware control platform combined with pressure limiting and multi force reduction hydraulic proportional system. The platform uses the high dynamic response characteristic of the servo valve to realize tension closed loop control and rolling speed tracking, and the high pressure flow characteristic of the proportional relief valve is eliminated. The strong coupling between the residual force and the front and post tension. (3) based on the flow characteristics and frequency response characteristics of the servo valve, the transfer function model of the servo valve is established and the key parameters of the model are obtained. A set of measuring experimental device for the volume elastic modulus of hydraulic oil and hose is designed according to the principle of compression method, and the volume elastic modulus of hydraulic oil and hose is measured. The pressure power exponent model of hydraulic oil at normal temperature is set up. On the basis of the flow continuity equation and force balance condition of the front and back tension hydraulic cylinders, combined with the process requirements of the rolling process, the influence factors of Zhang Liqiang coupling, external interference, hydraulic pipe effect, hydraulic cylinder friction and servo valve nonlinearity are fully considered. On the basis of this, the process change model of the controlled object is set up to lay the foundation for the simulation research and practical application of the control strategy. (4) relying on the mathematical model of the controlled object established in this paper, the simulation of different control strategies is carried out systematically. The results show that the traditional PID control mode can obtain good static control effect, but it is dynamic. The performance is poor and easy to cause tension shock. The combined control strategy of design speed feedforward and tension feedback can obtain good static loading and dynamic loading characteristics. However, because the control strategy can not complete adaptive adjustment, the control effect is controlled with the change of roll thinning, tension and rolling speed higher rolling conditions. On this basis, the fuzzy PID combined control strategy of speed feedforward and tension feedback is proposed, and the fuzzy PID controller introduced in this paper can adjust the control parameters adaptively under the condition of variable conditions. The system response speed is fast, the precision is high, and the robustness is strong. (5) the research results should be used in the direct drawing cold rolling of the maximum 100kN tension loading capacity. In the experiment machine, several typical metal materials are tested by tension cold rolling, the maximum rolling speed reaches 0.4m/s, the single pass maximum pressure is 37%, the dynamic tension control precision is guaranteed to be within + 1.1kN. The cold rolling experiment machine with high precision hydraulic tension control technology can be developed for the tension cold rolling process of all kinds of metal materials. And research provides reliable technical support.
【学位授予单位】：东北大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG333

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