【作者】 怀猛；

【导师】 金晓宏；

【作者基本信息】 武汉科技大学 ， 机械电子工程， 2007， 硕士

【摘要】 厚度与板形精度是板带产品的两大质量指标。目前随着轧制理论、控制理论和人工智能理论的发展,以及它们在轧制过程中的应用,使得板带产品的厚度精度与板形指标有了很大提高,然而,对单个机架轧机采用专门的控制技术,实现微米级带材精度的控制,仍是目前板厚控制领域研究的热点问题之一。板带轧机的控制非常复杂,其负载力大、扰动因素多、扰动关系复杂但同时对控制精度和响应速度要求很高,轧制过程是一个复杂的多变量强耦合非线性过程,各变量之间相互作用和影响密切。由于工况的改变,液压缸行程发生改变,使系统刚度及阻尼等参数发生变化,使系统在全工况范围内不能保持基本一致的响应时间和较高的控制精度。本文以武钢1700mm五机架冷连轧机机组的第一机架液压AGC作为研究对象,对液压变参数的范围、影响和补偿控制进行了研究,具体工作可归纳为以下几个方面:(1)概述了自动厚度控制的基本理论和变刚度AGC的控制策略,分析了该轧机应用的传统AGC的控制原理。(2)根据实际的物理模型,建立了液压APC模型和传统的前馈及监控AGC数学模型,并给出了系统的主要参数。(3)在建立的仿真模型的基础上利用基于MATLAB的Simulink工具箱进行了数字仿真,讨论了AGC系统中电液伺服阀固有频率、液压缸行程和负载阻尼等参数变化时系统的特征及其对系统控制精度与稳定性的影响,通过仿真值与实测值的对比验证了所建模型的正确性。(4)针对变参数系统的刚度变化和阻尼比相对较小的问题,在满足系统全工况范围内上升时间趋于一致的目标下,提出了应用滞后校正和位移微分正反馈校正的综合校正措施。进而通过仿真分析得出了经过校正后的系统具有更高的控制精度的结论。本文针对APC系统具有参数变化的特点,探讨了液压APC系统参数的变化对厚度控制精度的影响,在保证系统在全工况范围内响应时间基本一致的前提下,采用了滞后校正和位移微分正反馈校正的综合校正措施,为现场轧制提供了一种新的解决方案。更多还原

【Abstract】 The accuracy of strip gauge and the strip flatness are the main quality targets of a strip product. Currently, there have been huge advancements in the two targets above with the development of rolling theory, control theory, and artificial intelligence theory and their application in the rolling process. However, the application of the special control technology in singular-stand rolling mill and the realization of the control process with micron-level precision is still one of the hot spots in the control of strip thickness.The control of the strip rolling mill is very complex because there exist heavy loads and all kinds of disturbances and complicated relationships between them, and meanwhile high control accuracies and instant response are required. The whole rolling process is a nonlinear one with multiple variables, strong couplings and close relationships and interactions between those variables. Owing to the change in the operating range, the corresponding change in the stroke of the hydraulic cylinder, such parameters as the system stiffness and damping ratio vary a deal, and as a result of the entire system is unable to maintain the basically consistent response time and unable to achieve a higher control precision within the whole operating range as well.The paper discusses the ranges, influences and compensations of the variable parameters in the Automatic Gauge Control (AGC) in the first stand at WSPC’s 1700-millimetre cold tandem mill. The works discussed in this paper are as follows.(1) The basic theory of the AGC system and the control strategy of the AGC system with variable stiffness are summarized, and the control principles in the traditional AGC used in the rolling mill mentioned above are analyzed.(2) Based on the physical model in actual system, the mathematic model of both the Hydraulic Automatic Position Control (HAPC) system and the traditional AGC system with feedforward and monitors are established, and the main parameters of the system are provided.(3) Simulations are implemented subsequently with the SIMULINK Blockset in MATLAB based on the mathematic model already established. The natural frequencies in electro-hydraulic servo valve, the displacement of the actuators and the damping ratio are variable. The feature of the system with the variable parameters and their influences on the accuracies and stabilities in AGC are discussed. The simulation results and the measured results are compared to verify the validity of the model.(4) In order to solve the problems of variable stiffness and relatively small damping ratio, a compensation combining phase lag with positive differential feedback of displacement was advanced with the target for a constant response time in the whole operating range. The simulations demonstrated that the system compensated has higher control precision.This paper discusses the influences of the variable parameters on the accuracy of the gauge control in accordance with the characteristics in the variations of the parameter in the APC system. Aimed at the realization of a constant response time in the whole operating range, a compensation combining phase lag with positive differential feedback of displacement are utilized, which offers a new solution to actual rolling process.更多还原