轧机非线性垂振系统动力学特性及稳定性控制策略研究

发布时间：2019-01-15 08:49

【摘要】：面临日益严峻的资源与环境的约束以及产能和需求之间的矛盾,作为主要成材工艺的板带轧制生产需要进一步转型升级。然而,板带轧机在高速轧制过程中经常发生振动现象,阻碍了轧制生产的高效化发展进程,集中表现在机架与轧辊间产生的垂直于轧制方向的振动,是破坏轧制系统稳定性以致轧制厚度波动的主要原因。因此,为提高板带轧机轧制稳定性和轧制精度、改善轧制产品的质量和性能,本文对多种非线性因素影响下的板带轧机辊系振动行为及抑制策略展开研究。首先,本文分别研究了活塞杆与液压油两种介质间弹性模量的差异所导致的液压缸刚度非线性,液压缸活塞与缸壁间非线性摩擦,轧制力动态特性以及轧件变形滞后非线性特性等因素对轧机辊系振动行为的影响。其次,采用集中质量法将板带轧机辊系结构简化为弹簧-质量块模型,基于广义耗散Lagrange原理分别建立液压缸分段非线性约束下的板带轧机辊系振动模型、轧制力动态特性影响下的板带轧机辊系振动模型和轧件滞后变形非线性影响下的板带轧机辊系振动模型,并在此基础上提出一类具有弹性和阻尼双分段非线性约束模型。分析液压缸非线性刚度、非线性摩擦、轧制速度和外激励等因素影响下的辊系振动系统的周期响应特性,分别得到各非线性因素变化对板带轧机辊系振动系统幅频响应和稳定性的影响规律。然后,采用平均法和增量谐波平衡法等非线性问题求解方法得到各系统模型的动态响应。运用奇异性理论得到系统在不同约束条件下的转迁集,在由转迁集划分的各个子区域选取开折参数得到板带轧机辊系振动系统所有分岔拓扑。结合系统分岔图和最大Lyapunov指数曲线,分析板带轧机辊系振动系统随轧制速度、外激励幅值和频率变化的分岔行为,得到系统分岔失稳时的参数临界值。运用Melnikov方法得到分段非线性约束系统发生混沌的条件解析表达式,并提出了分段非线性约束系统混沌运动的时滞状态反馈控制策略。最后,组建板带轧机辊系振动测试试验平台,在板带轧制生产线上进行振动测试实验。通过模型仿真分析与实验结果对比的方式验证了本文所建立的板带轧机辊系非线性振动模型及分析结果的有效性。本课题的研究将弥补国内在轧机辊系振动系统建模及其动力学特性分析方面理论研究的不足。针对板带轧机液压系统存在的分段非线性约束特性,提出分段非线性约束系统混沌运动的控制策略。研究结果给在保证轧制精度的前提下提高轧制速度奠定了基础,对提高板带轧制稳定性和产品质量具有重要意义。
[Abstract]:Facing the increasingly severe constraints of resources and environment and the contradiction between production capacity and demand, strip rolling production, as the main process of finished wood, needs to be further transformed and upgraded. However, the vibration of strip rolling mill often occurs in the process of high speed rolling, which hinders the development of high efficiency of rolling production, which is mainly reflected in the vibration in the direction perpendicular to the rolling caused by the stand and roll. It is the main reason to destroy the stability of rolling system and cause the fluctuation of rolling thickness. Therefore, in order to improve the rolling stability and precision of strip mill and improve the quality and performance of rolling products, the vibration behavior and suppression strategy of roll system of strip mill under the influence of many nonlinear factors are studied in this paper. Firstly, the stiffness nonlinearity of hydraulic cylinder caused by the difference of elastic modulus between piston rod and hydraulic oil and the nonlinear friction between piston and cylinder wall are studied. The influence of dynamic characteristics of rolling force and nonlinear characteristics of deformation lag on roll system vibration behavior of rolling mill. Secondly, the roll system structure of plate and strip mill is simplified into a spring-mass block model by means of concentrated mass method. Based on the generalized dissipative Lagrange principle, the roll system vibration model of plate and strip mill under the nonlinear constraint of hydraulic cylinder segment is established respectively. The roll system vibration model of plate and strip mill under the influence of dynamic characteristics of rolling force and the roll system vibration model of strip mill under the influence of nonlinear deformation of plate and strip mill are presented. Based on this model, a class of elastic and damped double segment nonlinear constraint model is proposed. The periodic response characteristics of roller system vibration system under the influence of nonlinear stiffness, nonlinear friction, rolling speed and external excitation of hydraulic cylinder are analyzed. The effects of various nonlinear factors on the amplitude frequency response and stability of roll system vibration system of strip mill are obtained. Then, the dynamic response of each system model is obtained by means of averaging method and incremental harmonic balance method. By using the singularity theory, the transition sets of the system under different constraints are obtained, and all bifurcation topologies of the roll system vibration system of plate and strip mill are obtained by selecting the opening parameters in each sub-region divided by the transition set. Based on the system bifurcation diagram and the maximum Lyapunov exponent curve, the bifurcation behavior of roll system vibration system with rolling speed, external excitation amplitude and frequency is analyzed, and the critical values of parameters when the system bifurcation is unstable are obtained. The conditional analytical expression of chaos in piecewise nonlinear constrained systems is obtained by using Melnikov method, and a time-delay state feedback control strategy for chaotic motion of piecewise nonlinear constrained systems is proposed. Finally, the vibration test platform of strip mill roll system is set up, and the vibration test experiment is carried out on the strip rolling line. The effectiveness of the nonlinear vibration model and the analysis results of the roll system of strip mill are verified by comparing the simulation results with the experimental results. The research in this paper will make up for the shortage of theoretical research on the modeling and dynamic characteristic analysis of roll system vibration system in our country. Aiming at the piecewise nonlinear constraint characteristics of hydraulic system of strip mill, a control strategy for chaotic motion of piecewise nonlinear constrained system is proposed. The results laid a foundation for improving the rolling speed under the premise of ensuring the rolling accuracy, and it is of great significance to improve the rolling stability and product quality of strip rolling.
【学位授予单位】：燕山大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG333

【相似文献】