On Research Of Automatic Overlock Sewing Machine Servo System

The industrial overlock machine is a kind of sewing equipment, which is used in textile and garment factories. Its structure is complex and its servo control system is very difficult. For a long time, the domestic using of the servo controller is basically imported from abroad, and the research and development of the domestic electric overlock sewing machine is started lately. Meanwhile, the domestic technical level is not high, so the high-performance electric overlock sewing machine is luxury goods for only a small number of high-end clothing manufacturing enterprises. The sustained and rapid development of domestic textile and apparel industry has brought enormous opportunities for sewing equipment industry. The performance of the overlock machine is determined by its servo control system. When high performance servo system is applied in large-scale factory production, it can reduce labor intensity and improve production quality and efficiency greatly. Therefore, developing high performance overlock machine servo system is of great significance.In order to develop a suitable servo system for industrial using on overlock machines, on basis of the research of the working mechanism of industrial overlock machine, this paper considered the performance requirements of the servo system. Meanwhile, this paper designed the system scheme, hardware system and software system, and also tested the servo system in the laboratory. The main work of this paper is as follows:(1) The theory study on the AC servo control system, including the mathematical model of permanent magnet synchronous motor, the vector control technology, as well as the voltage space vector pulse width modulation technology. These studies provide theoretical basis for overlock machine servo system scheme design, hardware and software design.(2) The analysis of the servo motor selection. According to the system performance requirements of overlock machine, this paper designed a closed-loop control strategy including position, speed and current. In order to realize accurate servo control, this paper determined the rotor position detection method of servo motor and the speed measurement scheme. At the same time, the motor closed-loop vector control system was simulated, and the intelligent PID controller based on artificial bee algorithm was designed and simulated for speed loop. By using the optimization mechanism of artificial bee colony algorithm, the control performance of motor speed was improved. In addition, the brake control scheme of the servo system was designed.(3) The hardware design for industrial overlock machine servo system. The TI DSP chip--TMS320F28034 was used as the core controller, and some external circuit. They were interconnected with other components through multiple interfaces. The current sampling circuit, the bus voltage sampling circuit, and the speed and position detection circuit were designed. The power drive chip was selected. The other peripheral circuits, such as the foot pedal control circuit, the electromagnetic valve drive circuit, and the photoelectric sensor circuit were also designed.(4) The software design for industrial overlock machine servo system. The TI CCS integrated development environment was used for software development. Meanwhile, the software state diagram and the state machine of the servo system were specifically designed by using the event-driven programming architecture. Also, the vector control algorithm flow was given. And the fault processing module of sewing machine system was designed. At last, the button and display part of the operation panel was designed.Finally, the servo system of overlock sewing machine was tested. The test results show that the servo system can meet the demand of industrial application, and it has a good industrial application prospect. At last, the summary and outlook were put forward, and the direction of further research was also put forward.The main innovation points of this paper are as follows:(1) This paper combined artificial colony algorithm and PID controller, and designed a new fitness function including the overshoot penalty term, and used the stochastic optimization mechanism of artificial bee colony algorithm for optimize the speed loop control parameters of PMSM. The simulation results show that the speed control effect is better.(2) In order to realize the automatic start-stop sewing, this paper added two photoelectric sensors to the servo system. According to the detection results of the sensors,the servo system can judge whether there is fabric through the presser foot. This method realized the automatic detection of fabric position, the automatic lift presser foot function, so as to enhance the automation of the servo control system.(3) In order to guarantee a clean environment in the factory, this paper added two suction wind modules to the servo system. By controlling the electromagnet and pneumatic suction device, the broken wire and broken material could be inhaled to designated bag. This method can effectively maintain the cleanness of the scene of the industrial processes.