滑动轴承支承机电耦联轴系的稳定性分析

发布时间：2018-05-17 12:21

本文选题：可倾瓦轴承 + 运动极坐标　；参考：《沈阳工业大学》2012年硕士论文

【摘要】：广泛用于数控机床的电主轴具有结构紧凑、动态精度高等众多优点,已逐渐取代传统结构的变速箱。本文研究轴承-转子系统的动力学问题,主要研究内容包括:1)径向可倾瓦轴承动力系数计算;2)可倾瓦轴承稳态平衡位置搜索;3)轴承—转子系统临界转速确定;4)轴承—转子系统稳定性分析。可倾瓦径向滑动轴承动力特性系数的计算主要基于对雷诺方程的求解:首先根据力矩平衡条件确定瓦块摆角,用偏导数法得出各瓦块稳态时的动力系数;然后,考虑瓦块摆动对系数的影响,建立静动坐标间动力系数的关系,计算出可倾瓦轴承动力特性系数。针对可倾瓦轴承稳态平衡位置搜索,提出了一种新式运动极坐标系搜索方法,该方法能有效避免搜索过程中的死循环问题,也适用于其它滑动轴承。不平衡磁拉力的存在会改变轴承—转子系统的临界转速,运用专业软件对电主轴进行磁场分析,提取不平衡磁拉力,以更准确计算轴系的动力特性。本文介绍了两种临界转速的计算方法:1)传递矩阵法。用传递矩阵—多项式法计算临界转速,可以容易地将支承的阻尼包含在传递矩阵中,由于状态向量含有8个元素,因此特征方程阶次较高,为提高低阶根的精度,引入时间因子,借助QR法求解复数特征根;Riccati传递矩阵法将两点边值问题转变为一点初值问题,因此保持了较高精度。2)有限元法计算过程。在有限元分析软件中建立轴系的简化模型,考虑陀螺力矩影响,加载后求解,绘制出系统的CAMPBELL图,提取临界转速。本文还简单介绍了模态振型和不平衡响应的计算过程。对数衰减率用来度量振幅衰减快慢,反应系统受扰后回复到平衡状态的能力,可以作为衡量轴系稳定性的指标,已被推广到多自由度系统。针对计算的转子系统,本文画出了复特征值对应的对数衰减率曲线,分析了轴系的稳定性。
[Abstract]:The motorized spindle, which is widely used in NC machine tools, has many advantages such as compact structure, high dynamic precision and so on. It has gradually replaced the traditional transmission. In this paper, the dynamic problem of bearing-rotor system is studied. The main research contents include: 1) calculation of the dynamic coefficient of radial tilting pad bearing 2) search for steady equilibrium position of tilting pad bearing 3) determination of critical speed of bearing-rotor system (4) Stability analysis of bearing-rotor system. The calculation of dynamic characteristic coefficient of tilting pad radial sliding bearing is mainly based on the solution of Reynolds equation. Firstly, the swing angle of tile is determined according to the condition of moment balance, and the dynamic coefficient of each tile is obtained by partial derivative method. Considering the influence of tile swinging on the coefficients, the relationship between the dynamic coefficients of the static and dynamic coordinates is established, and the dynamic coefficients of tilting bearing are calculated. In this paper, a new search method of polar coordinate system is proposed to search the steady equilibrium position of tilting pad bearings. This method can effectively avoid the dead cycle problem in the search process and is also suitable for other sliding bearings. The existence of unbalanced magnetic pull force will change the critical speed of the bearing-rotor system. The magnetic field analysis of the motorized spindle is carried out by using professional software to extract the unbalanced magnetic pull force to calculate the dynamic characteristics of the shaft system more accurately. This paper introduces two calculating methods of critical speed: 1) transfer matrix method. The damping of the support can be easily included in the transfer matrix by using the transfer matrix polynomial method. Because the state vector contains eight elements, the order of the characteristic equation is higher, in order to improve the accuracy of the low order root. By introducing the time factor and solving the complex eigenvalue Riccati transfer matrix method, the two-point boundary value problem is transformed into a point initial value problem by using the QR method, so the high accuracy of the finite element method is maintained. The simplified model of shafting is established in the finite element analysis software. The gyroscopic moment is considered and solved after loading. The CAMPBELL diagram of the system is drawn and the critical speed is extracted. The calculation process of modal mode and unbalanced response is also briefly introduced in this paper. The logarithmic attenuation rate is used to measure the amplitude attenuation speed and the ability of the reaction system to return to equilibrium state after disturbance. It can be used as an index to measure the stability of shafting and has been extended to multi-degree-of-freedom systems. For the calculated rotor system, the logarithmic decay rate curve corresponding to the complex eigenvalues is drawn, and the stability of the shafting is analyzed.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH113.1

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