1. Company introduction
The equipment manufacturer of this project is Gaoan Co., Ltd., which is a large-scale chemical fiber machinery manufacturer. FA products have a wide range of applications and have a certain reputation in the industry. The equipment is used for the 5000 tons fiber post-processing production line project. The owner is a Japanese chemical fiber plant.
2. Equipment description
The equipment is used for chemical fiber multi-stretching and pre-crimping production, mainly by wire guides, eight-stick wire guides, hot water tanks, first drafting machines, water baths, second drafting machines, steam boxes, and third Drafting machine, stacking machine, tension frame, crimping machine, curling side plate motor, oil pump motor, vibration motor, circulating water pump, vibration detection and other devices. The I/O control scale is 103 points, of which the switch input point is 61 points, the switch output point is 39 points, and the analog input point is 3 points. The main control requirements are: chemical fiber filament speed, draft ratio, steam and water temperature, and related chain logic control. The key to the control of this system is to ensure that the speeds of the wires of the guide wire, the pull, the pull, the pull, and the curl are synchronized.
3. System Configuration
As shown in the figure, the system adopts Mitsubishi's Q series PLC as the main controller, the transmission control is Emerson's EV2000 series inverter, and the man-machine interface is F940GOT.
The main configuration of the system is as follows:
â— Main controller: Q00CPU: speed and draft ratio given, through the I / O module, testing the scene of each machine emergency stop, limit switches and analog signals, complete chain control and alarm functions.
â— Input module: QX40: complete on-site switching control acquisition
â— Output module: QY10: Complete switching output.
â— Module input: Q64AD: to complete the on-site analog test.
â— Serial communication module: QJ71C24N-R4: Make up the drive communication link.
â— Drive unit: Emerson's EV2000 series inverter.
In view of space, this article mainly describes the key design and implementation of system control, that is, to ensure the speed synchronization of the guide wire, one pull, two pull, three pull and curl five motors. The customer based on the cost factor, the transmission drive unit selects Emerson Corporation's EV2000 series frequency changer, and requests the main controller and its to form a low-speed and low-cost communication link which uses RS485 as the communication medium. Although the guide wire, one pull, two pull, three pull and curl 5 frequency converters use the common DC bus operation mode and install an incremental encoder to form the speed closed loop to improve the speed accuracy, the crimper inverter also applies a tension sensor to stabilize The tensile tension is controlled to improve the fiber quality, but the problem of real-time performance of the low-speed communication link is demonstrated when the process parameters such as the running speed and the draft ratio are adjusted during the start-up process of the equipment, especially during operation.
In terms of design, although a communication module can form a 485 network, because of the large amount of traffic, we must send the motor's speed command and start-stop information in real time. At the same time, we must constantly read the parameters of the inverter's operating voltage, current, frequency, etc. Therefore, if a module is used, the communication cycle will increase and it will not achieve the real-time effect. Therefore, we use two 485 communication modules, that is, four communication ports communicate with one lead, two lead, three lead, and four inverters at the same time. The guide wire and a lead share a communication port and communicate in the next cycle. Taking into account the maximum length of the communication protocol frame is 18 bytes, the maximum time difference of each speed command response is about 20ms at the transmission rate of 19200Bit/s. When the maximum speed is 200M/Min, although the guide wire is slightly lagging, It is acceptable in terms of process. This solution can effectively solve the synchronization capability of the speed command, achieve the synchronization of the speed of the five motors and the tension of the tension of the fiber tension during the start-up and stop-by-command synchronization of the speed of the drive and the speed adjustment during operation.
4. Commissioning and experience
In the actual debugging process, the system basically meets our expectations. However, in the communication debugging, we found that when the Q series PLC is equipped with multiple communication module systems, the stability of the communication is related to the length of the scan cycle of the PLC. With the continuous enhancement of functions and the continuous improvement of the program, the scanning period will also increase. When the maximum scanning period is greater than 25 ms, communication will begin to experience instability.
Phenomenon: We use the special communication instruction of QJ71C24 to accept the communication data. When the scan cycle is greater than 25ms, there are occasional communication errors at the last port of the program during the four ports of simultaneous communication. When the acceptance flag has been changed to ON indicates that the data has been accepted, but there is no data in the accepted data area. We reversed the order of the four ports of communication at the same time and found that the situation was still the same. Errors only occurred when the order came last.
Analysis of reasons: We believe that there is a problem with the communication timing. The system accepts the flag bit transition and the system data transfer is not synchronized. That is, when the system internal communication flag is established, the data of the communication buffer has not yet been transmitted. Therefore, we determine that the extended scan cycle will affect the timing of system communications. Solution: Reduce the program to shorten the scan cycle or replace the high-speed PLC. However, due to the large amount of program in the system, in order to ensure the reliability of the system, we will replace the CPU from Q00 to Q02, improve the system processing speed, reduce the scan cycle to less than 10ms, the problem can be solved.
5. User feedback
The system has been put into operation for more than three months. The current system operation is very stable and reliable, and the technical indicators have fully achieved the design effect.