Application of Emerson PLC and inverter in chemical fiber flexible production line

1 Introduction

In the past, for chemical fiber professional production equipment, the concept of "flexible production" has been increasingly introduced into the current design ideas. Flexible production lines have the advantages of simple configuration, high degree of automation, programmability and reconfiguration, and are adopted by the majority of users.

In the chemical fiber flexible production line, the extruder is an important part of the entire equipment, and the speed synchronization of the subsequent winding parts is the key to the entire system. The accuracy of the multi-motor speed synchronization in the system directly affects the quality of the chemical fiber finished product.

In the past, most production lines of this type used a method of installing an on-site operating box on each roller and manually adjusting the speed according to the actual situation. This solution has the following disadvantages: (1) It is not convenient for centralized data management; (2) The draft ratio needs to be calculated manually according to each speed; (3) If the actual speed does not meet the requirements, it needs to be recirculated to each area for adjustment, which is very troublesome to operate; (4) The scrap rate is high.

In view of the above problems, this design adopts a combination of centralized control and decentralized control in concept, with the touch screen and PLC as the core of control. The touch screen sets the recipe data, the PLC directly calculates the draft ratio, and the communication controls the inverter speed. The human-machine interface is centrally controlled, and a field operation box is installed on each roller, so that all controls can be performed on the touch screen and the entire system can be operated on site.

The application of communication is a major theme in the development of modern industry. The system designed with communication mode has a simple structure, reliable operation and can effectively avoid the loss of the entire system caused by hardware failure.

2 System Introduction

The process flow is shown in Figure 1.

Figure 1 Flow chart of chemical fiber flexible production line

The chemical fiber flexible production line is an important production line in the production of chemical fiber yarns. Its structure includes extruder, metering pump, wire separator, water tank, drafting roller (including heating and non-heating), guide wheel, cooling box, torque roller and wire take-up machine. During processing, the chemical fiber particles are put into the extruder hopper, heated and extruded by the extruder, and the chemical fiber melt is divided into hundreds of primary chemical fiber yarns on the wire separator. After cooling by water, dozens of chemical fiber yarns are wound into a bundle through the guide wheel on each drafting roller machine and stretched step by step to become a very fine chemical fiber finished product wound on the take-up reel. From the initial chemical fiber yarn to the finished product, the initial fineness of the chemical fiber yarn is determined by the gradual acceleration of the running speed of each roller machine. The specific speed is set by the draft ratio, and the draft ratio of different products is different.

The ease of operation is fully considered when designing this system. You only need to set the main speed, and the speed of each level can be calculated separately through the draft ratio. When adjusting the speed, the draft ratio of each level will also be automatically calculated and saved.

During on-site operation, there is an on-site operation box at each level, which can perform speed increase and decrease, independent start and stop, linkage start and stop and emergency stop functions. In addition, two line speed meters are installed on the two operation boxes of the 4-heat seven-roller machine and the 8-heat five-roller machine to display the current line speed for easy on-site adjustment. During centralized monitoring, the selection switch on the control cabinet is turned to the touch screen end, and the touch screen can be used for start and stop operations. Regardless of centralized control or decentralized control, data can be set on the touch screen and the current frequency and current can be displayed.

3 Hardware Design

This system is mainly composed of touch screen, PLC, frequency converter, speed encoder and other auxiliary components. The whole system transmits data through communication, with simple structure, convenient operation and reliable operation. PLC adopts Emerson's EC20-3232BRA main control module, with a 16-point EC20-1600ENN input expansion module.

EC20 PLC is the highest-end product of Emerson's small PLC. It has high reliability, high responsiveness, powerful communication functions, rich instruction sets, etc. The program capacity can reach 12K steps, and the basic instruction time is only 0.09μs. Its board has undergone strict three-proof treatment, the working voltage is AC85~280V, and it has excellent anti-interference performance, which is a reliable guarantee for the stable operation of the system. The most important thing is that it comes with an RS485/RS232 communication interface and has rich communication instructions, making communication with external devices more concise and convenient.

Since the speed requirements of each drafting roller machine are very high, the inverters of each drafting roller machine are all Emerson TD3000 series, and a total of 7 TD3000 inverters are used. In addition, the 3-roller machine, 4-roller machine, 6-roller machine, 8-roller machine, 9-roller machine and 11-roller machine are equipped with speed encoders to ensure the speed accuracy requirements of the equipment. The 12-wire take-up machine adopts a TD3000 inverter without a speed encoder because the speed requirements of the equipment are not so strict.

TD3000 inverter is a high-performance vector control inverter of Emerson. It can be equipped with a speed encoder to form a speed closed-loop control, which can achieve fast response and accurate control of torque, and can operate in a wide range of speed regulation with high control accuracy. It has multiple functions such as automatic tuning, zero servo control, online switching of speed control and torque control, encoder disconnection detection, parameter copying, etc., and has an RS485 free communication interface, which can fully meet the requirements of the system. The metering pump uses two Emerson EV1000 general-purpose inverters.

The monitoring human-machine interface adopts a 10.4-inch touch screen for data display and setting, which is intuitive and reliable.

In the whole system, PLC is the control center, which can complete the whole control process independently. When the touch screen fails, it can still be controlled through the on-site operation box without affecting the operation of the whole system.

The main control part of the system is shown in Figure 2

Figure 2 Electrical main control schematic diagram

The PLC control part of the system is shown in Figure 3.

Figure 3 PLC electrical schematic diagram

4. Software Programming

This system uses a touch screen as the human-computer interaction interface, which is simple to program and has stable performance. The main control screens of the touch screen are shown in Figures 4 and 5.

Figure 4 Touch screen main display screen

Figure 5 Parameter setting screen

The "touch screen main display screen" is the screen that operators often need to view. It is mainly used to display the operating frequency and current of metering pumps 1, 2 and each drafting roller machine as well as their current operating status, and also displays the master speed and the length of the take-up line. It only monitors the current operating status and cannot be set. Various command buttons are set on the upper part of the screen. Click them to query the corresponding status or perform corresponding operations. Click "draft ratio" on it to enter the screen shown in Figure 4. It is the main operation screen when the user is debugging. When adjusting the machine, the user first sets the linear speed of each drafting roller machine, and then clicks "confirm" to calculate the draft ratio of each level and the main draft ratio. After determining the draft ratio, you only need to adjust the master speed to automatically set the operating speed of each roller machine according to the draft ratio, so as to achieve the purpose of speed increase and decrease. At the same time, toggling the "speed increase/decrease" switch on the operation box can also achieve the purpose of speed increase and decrease. "Maximum speed limit" is mainly a protective measure to prevent improper operation. As the lower computer of the touch screen, PLC is responsible for data transmission and processing. It reads and sets data through communication with the inverter. Its network composition is shown in Figure 6.

Figure 6 PLC and inverter communication network communication composition diagram

When forming this network, since the communication protocols of EV1000 and TD3000 inverters are inconsistent, only free communication protocol can be used for communication. EC20 PLC, as the control master station, has absolute control in the system. It actively sends instructions to the inverter and actively receives feedback data from the inverter. Here, we use the COM1 port of EC20 as the RS485 communication port to communicate with the inverter, and the COM0 port is used to communicate with the touch screen, which is set to MODBUS protocol. The following is a brief introduction to the communication between Emerson PLC and inverter.

[page]

The communication between devices requires not only the corresponding hardware interface, such as USB, RS232 interface, RS485 interface, Ethernet port, etc., but also the corresponding software support, that is, the communication protocol. This system uses the RS485 interface and the free port communication protocol. RS485 communication can theoretically connect 128 devices, the communication distance can reach 1200 meters, and it has strong anti-interference performance. It is currently a commonly used communication method in industrial control.

The following is the design of the communication program: Before writing the program, we must set the serial port parameters, such as baud rate, data bit, start bit, stop bit and parity check. Here we set the baud rate = 9600, data bit = 8, start bit is not set, stop bit = 1, parity check = no check. The specific parameter settings are shown in Figure 7.

Figure 7 Emerson PLC communication parameter settings

After setting these parameters, we can write the communication program. This program is relatively long, so I will not explain it in detail here. I will only list the TD3000 inverter frequency setting and current reading subroutines for your reference. For specific data reading and writing, please refer to the Emerson EV1000 and TD3000 free port communication protocol.

Entry parameters: addr, freq_set

Export parameters: end, freq

//Set frequency, read current, use long frame to read function parameter FF.05

//Initialize short frame, frame header is 02

LD SM0

MOV 16#2 V3

MOV #addr V4

MOV 16#1F V5

MOV 16#5 V6

MOV 16#0 V7

MOV 16#0 V8

MOV 16#44 V9

MOV 16#7F V10

MOV #freq_set K4M1980

MOV K2M1988 V11

MOV K2M1980 V12

MOV 0 Z0

MOV 0 V13

//XOR check

LD SM0

FOR 9

LD SM0

WXOR V13 V4Z0 V13

LD SM0

INC Z0

NEXT

//Send and receive

LD SM0

MPS

NOT SM122

XMT 1 V3 11

RCV 1 D7000 11

MRD

AND SM123

MOV D7004 K2M1988

MOV D7005 K2M1980

MOV K4M1980 #freq

MPP

AND SM123

SET #end

//After sending, turn on the completion flag END

This program is a subroutine for setting the frequency and reading the current of the TD3000 inverter. The communication program of EV1000 can be designed according to its communication protocol. The following introduces the parameter setting of the inverter. Since there are a total of nine inverters that need to communicate, we set the addresses of the inverters to 10 to 18 respectively. The specific communication parameters of TD3000 are set in the F9 group, and EV1000 are set in the FF group. In addition to setting the communication parameters, there are also encoder, analog quantity setting and other parameters. The settings are as follows:

TD3000 inverter communication parameters F9.00 3 F9.01 0 F9.02 12-18

Encoder parameter Fb.00 1024

Start and stop parameters F0.02 1 F0.03 6 F0.05 1

Analog parameter F6.08 0 F6.11 7.8

EV1000 inverter communication parameters FF.00 0005 FF.01 10-11

Start and stop parameters F0.00 2 F0.03 1

In this program, in addition to setting the frequency for the inverter, we also need to read the current current and fault status of the inverter to reflect the current operating status of the equipment. In addition, there are parameter calculation, system start and stop, fault alarm and other programs, which are not listed here one by one.

5 Conclusion

Since the operation of this chemical fiber flexible production line, the following effects have been achieved:

(1) Excellent synchronous speed accuracy significantly reduces product scrap rate.

(2) Perfect centralized control greatly reduces workers’ labor intensity.

(3) The equipment speed has been increased from 100 m/min to 150 m/min, increasing efficiency by 50%.

(4) The parameters of the production process are fully recorded, providing a basis for quality traceability.

The above effects have been highly praised by users.

Judging from the actual application this time, the high speed accuracy of Emerson's high-performance vector inverter TD3000 and the powerful communication capability of the EC20 series PLC can fully provide the chemical fiber industry with a systematic solution with high stability, high reliability, high automation and high efficiency.

Communication is increasingly entering the field of modern control, and it is directly leading the transformation of traditional industrial control design concepts. From monitoring systems with tens of thousands of points to single equipment, communication is everywhere. It has won the support of many industrial control experts with its fast hardware configuration and efficient operation. Emerson EC series small PLC has added a communication interface and many powerful and practical communication functions, which is the current development direction of small PLC.