| 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. |
