链式刀库及机械手自动换刀装置可靠性试验台研究

【作者】 朱振华；

【导师】 韩军；

【作者基本信息】 南京理工大学 ， 机械电子工程， 2012， 硕士

【摘要】 加工中心已成为衡量一个国家制造业水平高低的重要标志之一。而自动换刀装置是整个加工中心的关键部件。根据调查显示,虽然近些年,我国自动换刀装置的生产水平取得了长足的进步,但是和一些发达国家相比,还存在不小的差距,主要体现在可靠性方面,并且可靠性低已经成为制约国产自动换刀装置竞争力的重要因素。因此,提高自动换刀装置的可靠性水平对于提高加工中心整体的可靠性水平具有突出的意义。课题结合国家科技重大专项“车铣复合加工中心用刀库及机械手可靠性设计及性能试验技术研究”,针对自动换刀装置可能产生的可靠性故障,如刀库故障、机械手故障、电气故障和液压故障等,设计了相应的可靠性试验台。通过电气系统的设计、控制系统的设计、测试系统的设计和数据分析,搭建了一个完整的可靠性试验台,为可靠性的研究奠定了基础。通过深入研究试验台的功能,依照电气系统设计的规范,设计了试验台的电气原理图,其中包括强电部分和弱电部分。根据整个系统所需的功率大小和电流大小,选择了相应的电器元件,并在此基础上完成了整个电气系统的布局和安装。结合整个自动换刀的功能要求和动作流程,选择了合适的数控系统和控制方式。利用数控系统在随机选刀方面的优越性,编写了刀库的自动选刀程序。基于宏程序的简便性,编写了机械手的自动换刀程序。最后通过现场调试,完成整个自动换刀的程序修改,使其满足自动换刀的要求。测试系统中分别设计了针对机械手和链轮的测试方案,并基于此方案通过PROSIG进行数据的采集。引入Hilbert-Huang变换对机械手在不同换刀速度下和不同抓刀数量下的瞬态运动特性进行了研究,通过对比时频图和能量谱图,可知当机械手瞬时运动状态发生改变时,相对应的瞬时频率和能量也将随之改变,因此可在一定程度上检测机械手的运动故障和掉刀故障并能准确的定位发生的时刻。对链轮振动信号进行了互相关性的EMD去噪预处理和Hilbert变换,对比分析不同载荷和不同转速下链轮的边际谱,可知当链轮周期旋转的条件变化时,频率和能量的分布也会产生变化,为链轮的早期探伤和故障分析提出了一种有效的途径。更多还原

【Abstract】 Machining center is a key flag of weighing a country’s manufacturing level. Meanwhile, ATC is an important component of Machining Center. According to some research, although our country has achieved a huge progress in developing ATC in past decades, there is still a dramatical gap between our nation and overseas developed countries, mainly in the area of reliability. Besides, the low reliability has regressed to be one of these destructive elements that waken the competition of our self-manufactured ATC. Thus, it is a remarkable significance to enhance the overall reliability level of Machining Center by means of improving the reliability of ATC. A relevant reliability testbed is built up following the analysis of possible reliability fault in ATC, such as manipulator fault, magazine tool fault, electrical fault and hydraulic fault based on the national major science and technology project "A Study on Reliability Design and Performance Test of Magazine Tool and Manipulator in Turning-Milling Compound Machining Center". This reliability testbed is a comprehensive testbed which contains electrical system, controlling system, testing system and data analysis. By combining all its four units, a solid ground and experiment environment are paved to discuss the ATC reliability.According to the function of this testbed and the design standand of electrical system, a schematic circuit diagram is carried out, including two parts:strong current system and weak current system. After calculating the power and current, electrical components are sorted out. At last, the layout and installment of this electrical system are conducted.An appropriate Numerical Control System and reasonable control mode is fixed by considering both the sequence of movement and the function of ATC.Due to these superiorities of Numerical Control System in the field of random tool selection, an automatic tool selection program based on magazine tool is compiled. Taking advantage of its convenience of macroprogram, an automatic tool change program based on manipulator is composed. Subsequently, a live debugging is proceeded so as to meet the function of ACT.Two testing schemes are figured out separately on manipulator and chain wheel, then data are collected through PROSIG accordingly. Hilbert-Huang Transform (HHT) is introduced to study the transient motion feature of manipulator under the condition of various tool changing speed and different number of tools. From time-frequency diagram and frequeny-energy diagram, it can be easily to know that transient frequency and energy will change in the wake of the instantaneous movement state change of manipulator. Thus, it’s possible to apply this method in decting movement fault of manipulator and tool-off fault, as well as locating the moment when the fault occurs. After preprocessing the viberation signal of chain wheel with the method of Cross Correlation EMD, the viberation signal is optimized. According to the frequency-energy diagram of chain wheel in different load and various rotate speed, the overall frequency and energy will change when the rotating condition is changed which can be seem as a practical method in flaw diction of chain wheel and fault analysis in chain wheel.更多还原