| With the development of textile industry, and the improvement of automatic control technology, the higher demands of automation sewing equipments is raised by textile industry, which means that the more advanced automatic technology is needed for the sewing machines. Industry Sewing Machine (ISM) is a typical automation sewing machine, and the servo control system is the power source and the main controller of the ISM, so the level of automation technology of ISM is determined by that of the servo control system. But most of the intellectual properties are mastered by the other countries and china hasn't advanced enough automatic technology ourselves, which makes the sewing machine manufacture companies in china be in a passive state. So developing ourselves' ISM has important significance for the textile industry even automation field of china.In this paper, the ISM servo control system is deeply studied, and the current research situation and future development trends are analyzed. Based on simplifying the hardware system, this paper combines modem control theory and traditional control system to realize the functions and performances of the servo control system.The servo control system uses PIC18F4431 and Intelligent Power Modules (IPM) as chief controller and motor driver, and it has the protection circuits and some auxiliary circuits. The hardware system has characteristic of high integration and high reliability.The main functions of servo control system are quick start, quick braking, speed control, position control, system protection and so on. The two key technologies are speed control and position control. For needs of research and decreasing the cost of hardware, the HALL position sensors and current sensor with low precision are used to be acquisition tools for position, velocity and current signals. Since there aren't high precision real-time signals, it brings much more difficulties of speed control and position control. To solve this problem, the fuzzy-PI algorithm is used for speed control and the expert controller is used for position control. For speed control, the improved PI algorithm has good steady-state but there will be overshoot. Fuzzy algorithm has good dynamic response but there will be stead-state error. To avoid the disadvantages of the two algorithms, the fuzzy-PI is used, and it has good dynamic response and also has no steady-state error. For position control, since it can't gain the high precision signals during the braking, the traditional control theory can't be used directly. According to the rich experiences of the developers, the expert controller with the input of velocity, current and duty cycle before braking is used for position control, and it has good control effect of high precision, stability and reliability.The numerical control automatic thread trimming servo control system of ISM using the methods discussed in this paper has been mass-produced and passes the tests of markets. So, the program in this paper is feasible. |
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