Application Of Mitsubishi Q Plc In Fiber Post-treatment Production Line

1. Company introduction
    The equipment manufacturer of this project is Gao'an Company, which is a large-scale chemical fibre machinery manufacturer. FA products are widely used. There is also a well-known PLC in the industry. This equipment is used in 5000 tons of fibre post-processing production line project. Its owner is a Japanese-funded chemical fibre factory PLC.

      2. Instructions for equipment

      This equipment is mainly used in the production of chemical fibre multi-stretching and crimping pretreatment. It consists of guide frame, eight-bar guide machine, hot water tank, first drafting machine, water bath, second drafting machine, steam box, third drafting machine, stacking machine, tension frame, crimping machine, crimping side plate motor, oil pump motor, vibration motor, circulating water pump and vibration. The scale of PLC I/O control is 103 points, among which 61 points are the input point of switching quantity, 39 points are the output point of switching quantity, and 3 points are the input point of analog quantity. The main control requirements for the application of this system are: the speed of chemical fibre, drafting ratio, steam and water temperature, and interlocking logic control. Speed Synchronization Application of Five Motors of Silk, One Drawing, Two Drawing, Three Drawing and Curling

      3. System Configuration

      As shown in the figure, the system uses Mitsubishi's Q series PLC as the main controller, the transmission control is Emerson's EV2000 series frequency converter, and the man-machine interface is F940GOT.

      The main configurations of the system are as follows:

      Main Controller: Q00CPU: Given the speed and drafting ratio, through I/O module, it can detect the signal of switching and analog signals such as emergency stop, limit and so on, and complete the interlocking control and alarm function.
      Input module: QX40: Achieve on-site switching control acquisition.
      Output module: QY10: Complete switch output.
      Modular input: Q64AD: to complete the field analog detection.
      Serial Communication Module: QJ71C24N-R4: Constructs the communication link of frequency converter.
      Drive Unit: Emerson's EV2000 Series Inverter.

      In view of the space, this paper mainly describes the key design and implementation of the system control, that is, to ensure the speed synchronization of five motors: guide wire, one-pull, two-pull, three-pull and winding. Customers choose Emerson's EV2000 series frequency converter for drive unit based on cost factor, and require the main controller and it to form a low-speed and low-cost communication link with RS485 as communication medium. Although five inverters, i.e. guide wire, one-pull, two-pull, three-pull and crimping, operate in a common DC bus mode, and install incremental encoder to form a speed closed loop to improve speed accuracy. The frequency converter of the crimping machine also adds tension sensors to stabilize tension control and improve fiber quality, especially in the start-stop process of the equipment. The problem of real-time performance of low-speed communication links appears when adjusting parameters such as operating speed and draft ratio during operation.

      In design, although a communication module can form 485 network, because of the large amount of communication, we have to send the speed instructions and start-stop information of the motor in real time. At the same time, we have to constantly read the working voltage, current, frequency and other parameters of the frequency converter. So if we use a module, the communication cycle will increase. Real-time can not be achieved. So we choose two 485 communication modules, that is, four communication ports to communicate with one traction, two traction, three traction, and four coiled frequency converters at the same time, while the guide wire and one traction share one communication port and communicate in the next cycle. Considering that the length of communication protocol frame is 18 bytes, the maximum time difference of each speed instruction response is about 20 ms at 19200 Bit/s transmission rate. When the maximum speed is 200 M/Min, although the guide wire lags slightly, it is technically acceptable. This scheme can effectively solve the synchronization ability of speed command, and realize the synchronization of speed of five motors and the uniformity of fiber tension during starting and stopping in accordance with the command and adjusting speed in operation.

      4. Debugging and Experience

      In the actual debugging process, the system basically meets our expectations. But in the debugging of communication, we find that the stability of communication is related to the scanning period of PLC when Q series PLC is equipped with multi-communication module system. With the continuous enhancement of functions and the continuous improvement of programs, the scanning cycle also increases. When the maximum scanning cycle is greater than 25ms, communication begins to appear unstable.

      Phenomenon: We use the special communication instruction of QJ71C24 to receive communication data. When the scanning period is more than 25ms, there will be occasional communication errors at the last port of the program in the four ports of simultaneous communication. When the receiving flag bit has jumped to ON, it means that the data has been accepted, but there is no data in the receiving data area. We reversed the program order of the four ports of simultaneous communication and found that the situation remained the same. Errors occurred only at the last port in the sequence.

      Analysis of the reasons: We believe that there is a problem in the communication timing. The system accepts the jump of the flag bit and the transmission of system data is not synchronous. That is, when the communication flag is established, the data in the communication buffer has not yet been transmitted. Therefore, we judge that the prolongation of scanning period will affect the timing of system communication. Solution: Simplify the program to shorten the scanning cycle or replace high-speed PLC. However, due to the large amount of program in the system, in order to ensure the reliability of the system, we changed the CPU from Q00 to Q02, which improved the processing speed of the system and reduced the scanning period to less than 10 ms, and the problem was solved.

      5. User Feedback

      The system has been put into operation normally for more than three months. At present, the system runs stably and reliably, and the technical indicators have completely achieved the design effect.