Study And Its Applications On System Control Of LED Wafer Special Swing Type NC Multi-wire Saw

Swing type multi-wire saw (MWS) for LED substrate is the special equipment in the LED wafer manufacturing process in semiconductor lighting industry. The quality of the substrate sliced sheet direct impact on LED subsequent processing step. The cutting object of traditional MWS is silicon wafer and crystal with Moh’s hardness about5(Moh’s hardness of diamond is10). LED substrate mainly uses the sapphire and silicon carbide. The two kinds of material in more than nine’s hardness, but due to its high hardness and heavy brittle, there are some problems in the precision machining course. Traditional MWS cutting efficiency is low, even cut motionless and it must use special LED MWS. LED MWS is monopolized by Japanese and Swiss enterprises, and becomes a development bottleneck that constrains our country LED industry. LED MWS have great differences and ascend than traditional MWS in the system function structure, control strategy, automation degree and so on several aspects. Traditional MWS as reference to more contrast, LED MWS key technical difficulties in the process of project research as the main line, LED MWS NC system is further research.(1) The background and meaning of subject research are expounded. The domestic and foreign present study situation of MWS for LED wafers and for several key control technology have been studied. The development trend of numerical control multi wire slice technology is described. According to the project request, the theory foundation has been deeply researched on control system of MWS for LED wafer. The project tasks undertaken by author are introduced. And the main contents of this dissertation are given.(2) Through the analysis of the traditional MWS mechanical structure and principle,the reasons that cutting efficiency of traditional MWS cutting LED material with high speed is low and cutting quality is not stable is got. According to the disadvantages of traditional MWS, the diamond wire+cooling fluid cutting model alternative steel wire+mortar model; the problem of free abrasive is solved.A swinging mechanical structure is designed; the fault that traditional MWS p value is not constant is solved. At the same time, automatic winding institutions and row wire institutions of the pay-off side are increased, and LED MWS mechanical institutions is got. The key and difficult problem of LED MWS is analyzed.(3) To deal with the low precision and instability of nonlinear interference with normal control in the LED MWS, a disturbance observer linear H-infinity control algorithm is proposed.This algorithm take full account of error that caused by dynamics disturbances of subsystem model and unmodeled dynamics disturbances as well as the uncertainty of the parameters and structure of the LED MWS, and the solution is given. The stability of linear H-infinity control systems is studied, and under the conditions of the system stability, the analytical solution of dynamic equation is obtained by using the method of Chelosky decomposition. The system response speed is improved significantly. The experiment result of model machine illustrates that the system is undulating of tension small, stabilizes performance well and the break line ratio low.(4) A detailed analysis of the control difficulty comes after mechanical structure improvement. According to its inherent characteristics, making full use of the advantages of fuzzy control strong robustness and iterative learning control high precision, a fuzzy iterative learning control method is proposed. The control method avoids defects of fuzzy control that steady precision is not high and the iterative learning control that is sensitive to the parameters changes. Through the contrast of fuzzy control and fuzzy iterative learning control the operation of the algorithm, the experiment results show that the fuzzy iterative learning control algorithm is effective.(5) The automatic winding control requirements are analyzed after the change of machine structure and function. According to the system control requirements, the mainstream master-slave synchronous control algorithm was improved, a master-slave-position control algorithm is proposed. Compare with single master-slave control algorithm, master-slave-position control algorithm reduce the control grade and delay.It has the certain progressive significance. The limitations of master-slave-position control algorithm are analyzed, and through establishing a LED MWS mathematics model of the automatic winding, a kind of parallel differential coupled control algorithm is put forward. Its effectiveness is prooved. Parallel differential coupled control algorithm establish unified synchronous model of angular velocity and linear velocity for the system, absorbs the advantages of the adjacent cross coupling control and partial cross coupling control.In the contrast test with master-slave-position control algorithm, it prove that high control accuracy, fast response and the effect is good.(6) People often set machine parameters like the linear speed, tension and speed of the work piece platform with experience. And once the parameters set, the cutting process remains unchanged. Relying on operation experience is the low automatic degree, and is not necessarily the best choice. Fixed cutting parameters may not have the highest efficiency.These parameters is very important to cutting efficiency. This article find out the quantitative relationship between cutting efficiency and above three parameters, and according to the relationship established the mathematical model. A time optimal control is put forward. The experiment results and data analysis show that the machine has high sliced precision and good stability.This scientific project has developed a LED MWS product successfully. The complete machine performance has achieved the expected goal, this new product already put into market application in2011. In this paper, a few core control technology reserched in LED MWS has an important meaning for the NC MWS series equipment development. At the same time, it has important reference function and value for the industry related control topic research.