【作者】 许宝玉；

【导师】 刘义伦；

【作者基本信息】 中南大学 ， 机械工程， 2014， 博士

【摘要】 摘要：铝板带热连轧线的动力学特性及其控制是保证其生产效率,提高轧制板带质量以及降低其维护成本的关键。本文采用理论与实验研究、多学科相互融合的研究手段,对国内某“1+4”铝板带热连轧线及其轧机的稳定性、可靠性及辊系优化进行了机理分析、模型创建、仿真、测试及验证,构建了轧制力随机干扰模型及轧机动力学性能综合指标,提出了轧机辊系随机最优控制策略。通过现场测试和分析,研究了轧机辊系的运动规律及轧机振动的幅值、相位关系和频带能量分布等,获得了其基本振动形态和特征,印证了轧机固有特性仿真结果；建立了轧制力时间序列模型和随机干扰模型,对其进行了时、频域分析,验证了所用建模理论和分析方法的适用性；研究了铝板带热连轧机随机动力学特性,研究表明板带随机物理和几何特性可诱发轧机振动,轧材和轧辊振纹与随机轧制力功率谱密度成正比,得到了辊缝方差和功率谱密度随轧制速度的变化规律；提出了以辊系固有频率和阻尼比为设计变量,辊系振动加速度为最小的优化目标,建立了基于可靠度的轧机辊系动力学优化模型,并对辊系进行了随机优化,得到了不同加速度安全阈值的失稳概率相对应的最佳固有频率与阻尼比；构建了轧机单自由度、两自由度垂直振动模型、并分别与扭转振动模型耦合为轧机联合模型及连轧线多轧机联合模型,研究了主要轧制工艺参数对轧机和轧制过程稳定性的影响,得到了铝板带热连轧线及其轧机的稳定性准则；建立了二自由度板带轧机辊系受随机激励的非线性随机动力学模型,运用拟不可积Hamilton系统随机平均法和奇异边界理论分析了系统的全局随机稳定性,通过求解系统的FPK方程得到轧机辊系的稳态概率密度函数；研究了随机轧制力激励下的辊系动力可靠性,得出了轧机辊系随机振动响应和动力可靠度的变化规律；采用随机最优控制理论和方法对轧机辊系垂直振动的主、被动抑制进行了深入的研究,构建了轧机辊系综合动力性能指标,确定了最优控制力,研究了不同固有频率和阻尼比下辊系绝对加速度和相对位移的均方响应,提出了辊系随机动力学最优控制策略。本文采用的基于随机动力学理论的轧机动态特性分析和研究方法具有普遍性,所提出的随机干扰模型建模、辊系动力优化、辊系可靠性、辊系稳定性与随机最优控制策略在轧机动力学分析与控制的理论与实践方面具有创新性,本文研究表明基于随机动力学的振动分析和研究将有可能在连轧线及其轧机中得到广泛应用且对轧机优化设计、振动机理及其抑制方法的发展和完善具有一定的理论和实践意义。更多还原

【Abstract】 Abstract:The dynamic characteristic of strip hot tandem rolling mill under random and deterministic excitation is the key factor of ensuring its production efficiency, improving product quality and reducing maintenance cost. This paper attempts to investigate the stability, reliability and optimization of the strip rolling mill and the rolling process, including mechanism analysis, model creation, numerical simulation, testing and validation, creating the rolling force random excitation model, building the comprehension targets of stochastic dynamic performance and stochastic dynamic optimal control strategy by combining with the random vibration theory. The Specific studies were carried out on the issues above mentioned, it includes:Investigation of the basic vibration characteristics and mechanism of the aluminum hot strip tandem rolling mill based on field test and signal analysis, the simulation results of the mill inherent characteristics were partly confirmed, it provided the data support for building the rolling force stochastic excitation model combining of the actual production data of hot rolling production line, and its time domain and frequency domain characteristics were investigated. The modeling theory and analysis methods used were also suitable for different rolled materials and rack. The vertical stochastic dynamic characteristics of aluminum hot strip rolling mill were investigated and the mill roll system optimization model were created, it concluded that the random physical and geometrical properties of rolled strip can induced stochastic chatter in rolling process, the oscillation marks on roll and rolled material is proportional to the random rolling force power spectral density, and the variation law of roll gap variance and its power spectral density with the rolling speed were obtained. Taking the natural frequency and damping ratio of roll system as a design variable, and the smallest of vibration acceleration maximum steady value of the roll system as optimization goals, the reliability-based dynamic optimization model of rolling mill roll system were established and the best natural frequency and damping ratio corresponds to the instability probability at the acceleration security threshold were obtained. The stability of the rolling mill and the rolling process were investigated. The single degree of freedom and two degree of freedom vertical vibration model of roll system, the single-modal structure and multi-modal model coupling the torsional vibration and vertical vibration model, and multi-rack vibration model were established. The rolling process parameters on the stability of the rolling process were studied. The two degrees of freedom nonlinear stochastic dynamic model under random excitation for the strip mill roll were established for the first time. The global stochastic stability of roll system were analyzed by using the stochastic averaging method of quasi-non-integrable Hamiltonian systems and the singular boundary theory, and the steady-state probability density function of roll system were obtained by solving the FPK equation of the system. The dynamic reliability of the roll system under different random rolling force ware investigated, the variation of the random vibration response and dynamic reliability of rolling mill roll system were obtained. The stochastic optimal control theory and methods were used for study of vertical vibration suppression of rolling mill roll system; the comprehension targets of roll system were founded. The absolute acceleration and relative displacement mean square response of the roll system on different natural frequency and damping ratio were studied, and their variations of drift coefficient and diffusion coefficient with the total energy of the system for a given rolling speed were obtained, finally the stochastic dynamics optimal control strategy of the roll system was determined. It will be possible to be widely used in design and dynamic analysis for complex mechanical system that the novel vibration analysis and research techniques based on the nonlinear stochastic dynamics, and have important theoretical and practical significance to the methods and theory development and improvement of the mill structure optimization design, chatter mechanism and its suppression.更多还原