静压回转工作台油膜厚度的控制方法研究

发布时间：2018-09-17 09:27

【摘要】：静压回转工作台凭借其高精度、刚度强、磨损低、工作运行寿命长等技术优点,得以在数控机床领域被大量应用,其是立式数控机床一个重要的功能部件。而静压回转工作台油膜的刚度及其承载的能力基本都是由其油膜厚度来决定的,相对于传统的恒压供油液压系统,因为供油压力是一直不变的,当工作台的外载重和液压油的粘度发生改变时会引起工作台油膜厚度的改变,从而影响静压工作台的工作精度,降低回转台运行的平稳性。因此,为解决我国高精度、高承载且具有自适应调节能力的回转工作台几乎全部依靠进口的现状,迫切需要改进现有供油方式并提升工作台油膜厚度控制的自动化水平。在静压工作台液压工作系统方面,基于静压工作台及其液压供油系统基本原理,重点对开式静压导轨的结构以及其恒流式液压供油的特点进行分析;确定以开式恒流供油液体静压工作台作为研究对象,并设计了一种控制工作台油膜厚度的液压供油方案。在油膜厚度控制方案方面,针对现有工作环境和研究要求,基于控制系统硬件选型依据及意义,为提高油膜厚度控制精度,提出采用西门子840Dsl通用数控系统和变频器结合异步电机、多头泵、静压回转工作台以及电涡流位移传感器等部分环节构成的完整闭环油膜控制方案,并建立了相应控制环节的数学模型,同时推导出了频率与油膜厚度之间的理论模型。在油膜厚度控制方法方面,为了验证电机频率、油膜厚度理论模型的准确性,基于西门子840Dsl数控系统设计开发了油膜厚度智能控制人机交互系统软件,并根据油膜厚度检测方式,搭建油膜厚度控制实验平台,验证了基于理论模型的油膜厚度调节方案的准确性与可应用性。同时,在多次实验数据的基础上,重点提出了基于最小二乘法的油膜厚度控制调节方法,并进行验证分析,实验不仅进一步论证了理论模型的合理性,而且修正了理论模型误差,对油膜厚度控制精度更高,为实际工程应用提供了有力支持。
[Abstract]:With its high precision, strong rigidity, low wear, long working life and other technical advantages, the hydrostatic rotary table has been widely used in the field of CNC machine tools, which is an important functional part of vertical CNC machine tools. And the stiffness of the oil film and the bearing capacity of the hydrostatic rotary table are basically determined by the thickness of the oil film. Compared with the traditional hydraulic system of constant pressure oil supply, the oil supply pressure is constant all the time. When the external load of the table and the viscosity of the hydraulic oil change, it will cause the change of the oil film thickness of the table, which will affect the working precision of the hydrostatic table and reduce the stability of the rotary table. Therefore, in order to solve the situation that the rotary table with high precision, high bearing capacity and adaptive adjusting ability depends on the imported almost all, it is urgent to improve the existing oil supply mode and raise the automation level of oil film thickness control of the table. In the aspect of hydraulic working system of hydrostatic table, based on the basic principle of hydrostatic table and its hydraulic oil supply system, the structure of open hydrostatic guide rail and the characteristics of its constant-flow hydraulic oil supply system are analyzed. The open constant flow hydrostatic table is chosen as the research object, and a hydraulic oil supply scheme is designed to control the oil film thickness of the table. In terms of oil film thickness control scheme, according to the existing working environment and research requirements, based on the control system hardware selection basis and significance, in order to improve the oil film thickness control accuracy, A complete closed loop oil film control scheme composed of Siemens 840Dsl universal numerical control system and inverter combined with asynchronous motor, multi-head pump, hydrostatic rotary table and eddy current displacement sensor is proposed. The mathematical model of the corresponding control link is established, and the theoretical model between the frequency and the oil film thickness is deduced. In the aspect of oil film thickness control method, in order to verify the accuracy of motor frequency and oil film thickness theory model, a man-machine interactive system software for intelligent control of oil film thickness is developed based on Siemens 840Dsl numerical control system. According to the oil film thickness detection method, the oil film thickness control experimental platform was built to verify the accuracy and applicability of the oil film thickness control scheme based on the theoretical model. At the same time, on the basis of many experimental data, the oil film thickness control and adjustment method based on least square method is put forward, and verified and analyzed. The experiment not only proves the rationality of the theoretical model, but also proves the rationality of the model. Moreover, the theoretical model error is corrected and the accuracy of oil film thickness control is higher, which provides a strong support for practical engineering application.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG659

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