Wireless industrial network application

This paper introduces the process of wireless network applied to the automatic conveying system of the primer production line (circular self-propelled car). After the system transformation, it is not only flexible but also highly intelligent.

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Due to the increase in market demand, the original production system of Jianghuai Automobile Manufacturing Plant can no longer meet the demand for capacity increase: there is a bottleneck station in the paint primer production line, which is limited by the process time and has a long cycle time; the primer production line adopts segmental power supply. The control method, all the actions are completed by the ground master PLC, the technology is relatively backward, the flexibility is poor, and the expansion is difficult; the old system has been used for 10 years, some equipments are aging, the failure rate is very high, and the maintenance is very difficult. However, the original process tank still has the potential for improvement. The space of the tank is relatively large, and it can be put into two bodies for processing. By double-station transformation of the original production line bottleneck station and the addition of self-propelled car sets, bottlenecks can be eliminated, but the use of the original control system is difficult to achieve, and it is necessary to carry out transformation and upgrading.

The transformation of the primer production line of Jianghuai Automobile Manufacturing Co., Ltd. is actually the transformation of the automatic conveying system of the primer production line (circular self-propelled car). The final production capacity target, after the transformation, single-row, one-row and half-car models have a technical beat of 210s (originally 280s), and the production capacity has increased by nearly 30%; the double-shift daily output has reached 300 units (the original is about 200 units).

Process introduction

The automotive coating primer production line (also known as the “pretreatment and electrophoresis production line”) consists mainly of the process tank system and the automated conveyor system. It is the first key process of automobile painting. The quality of the primer is directly related to the subsequent process, and the automation degree of the conveying mechanism of the primer production line directly affects the quality and efficiency of the coating.


The primer production line has 11 process tanks, which are: pre-degreasing, degreasing, first washing, surface conditioning, phosphating, second washing, deionized water washing, electrophoresis, UF ultrafiltration washing, ultrafiltration washing and deionized washing. . The distance from the first trough to the last trough is about 100m. In addition, there are upper line, lower line and accumulation section. The entire length of the circular line is about 218m.

The action process of the primer production line is: the upper line points the white body of the welding shop to be mounted on the spreader. After the spreader is in place, the trolley carries the spreader into the tank body for processing, and then from the lower line point. The electrophoresis body is removed from the spreader, and after the empty spreader is raised into position, the trolley continues to run, and returns to the upper line through the accumulation area to enter the next cycle.

Generation of wireless solutions

Although the action process of the primer production line is relatively simple, we are retrofitting on the basis of the old line still in production, and the transformation time is very short (about 10 days), which is very risky. Our planning has always been around: ensuring reliability, reducing on-site construction, reducing programming and commissioning time, and enabling the starting point for full information collection.


The self-propelled trolley is a common equipment for the logistics transfer conveyor line. It is provided by the collector on the vehicle body and the sliding contact line pre-installed in the Track to take power during the movement and provide the mobile trolley. This kind of power-taking technology is very mature, but the data communication through sliding contact between the sliding contact line and the collector is quite special and difficult: First, because the sliding lines are laid in parallel in the track, and the distance is relatively close, only between There is insulation, the wire body is bare and there is no shielding layer protection, there is a great impedance between the sliding contact line and the sliding contact of the current collector, and the contact effect during the sliding process is also unstable, or there is more or less interference and each The unstable factor; the second is the problem of the amount of communication data. Due to the limitations of the dimensions of the track and the sliding line, the installation requirements and the economic indicators, the number of sliding lines is usually eight. At present, the popular data communication methods for the sliding line mainly include the on-board PLC-to-station signaling mode, the fieldbus (such as Profibus) mode, and the modulation and demodulation mode.

Since the transformation time of this project is very short, the transformation is also limited by the original old resources, so the above methods are difficult to achieve in the short term. Finally, we chose the most advanced wireless network communication technology. The characteristics of wireless are: wide coverage, high frequency and low interference, low power and not easy to interfere with other equipment; can adapt to harsh environment; easy installation, fast construction, free of a large number of hard wire (multi-core cable) construction; application interface is open, Easy to debug and maintain; easy to expand, high degree of flexibility; large amount of data exchange, fast rate.

It is very suitable to solve the problem of data communication of the trolley line through wireless network communication. The advantages of wireless also meet the needs of our transformation. After testing (including coverage area, signal strength, anti-interference, real-time and the impact of data exchange on network speed, etc.), we finally decided to adopt wireless communication solutions and adopted Phoenix Electronics' wireless technology and products.


Control system implementation

Ground control system

The system network diagram and main hardware configuration are shown in Figure 1 and Table.

(1) Set up a main control cabinet on the ground (see Figure 2), use Phoenix ILC350ETH PLC as the ground master PLC to process data between all ground and trolley, trolley and trolley, and conveyor system and process equipment. All information collection and monitoring of the exchange and production line. Connect to the switch through the Ethernet interface to communicate directly with the wireless access point.

(2) The HMI is installed in the main control cabinet, and the TP 12T touch screen of Phoenix Contact is used to control the start and stop of the 18 cars, the lifting and lowering of the spreader, and the control and operation of the process time of each process; real-time display of the whole line operation, online Information such as the status of the vehicle group, the position, the type of workpiece contained, and the current process tempo status are displayed, and fault diagnosis and alarms can be performed (see Figure 3).

2. Vehicle control unit

(1) 18 sets of new self-propelled cars, each of which uses the Phoenix ILC150ETH PLC to complete the start and stop of the trolley, the lifting of the spreader and the control of the process time of each process to realize the intelligentization of the trolley. The Ethernet interface is connected to the wireless client, and then communicates with the wireless access point through the wireless network, thereby realizing data exchange between the vehicle PLC and the ground master control PLC. The vehicle control unit is shown in Figure 4.

(2) The new self-propelled car drive is changed to the inverter control mode, and the position encoder of the company is configured to communicate directly with the PLC through the RS485 interface to realize the process identification, positioning recognition and anti-collision protection function, no mechanical wear, no reference Point, absolute position measurement, real-time detection, to maximize the intelligence of the car.

3. Wireless network unit

(1) Set up 18 wireless client (EC), install one on each car, and connect to 150PLC through Ethernet cable. The wireless client has a roaming function, and automatically selects the nearest wireless access point communication according to the strength of the signal, so that the vehicle 150PLC can maintain good data communication with the ground ILC350 main PLC.

(2) Set 2 wireless access points (APs). After testing, one wireless access point can meet the system communication requirements, and finally adopt two wireless access point solutions. On the one hand, considering that any one of them fails, the other can still ensure the normal operation of the network. It plays the role of hot standby and improves the reliability of the system. On the other hand, two wireless access points can realize wireless client roaming communication. When both wireless access points are normal, no matter where the car runs to the wireless customer The terminal can maintain the communication distance with the wireless access point to ensure very good communication quality. The on-site wireless access point and wireless client and settings are shown in Figure 5 and Figure 6.

4. Slide line unit

The sliding line unit includes 8 new sliding line systems (5 powers, 3 controls), multi-channel power supply, balanced compensation; the new collector has two-way function, both output and input, flexible and high The communication capacity of the trolley line is increased to a limit. When the wireless network system fails, the new sliding line system can remove the faulty loop into the emergency mode, and use three control sliding lines to ensure that the trolley can operate conditionally under abnormal network conditions.

New system features

1. Consistent electrical products

Both PLC and wireless products use Phoenix Contact's products for consistency, compatibility, compact structure and minimal space.

2. Using wireless networks brings immediate benefits

(1) The installation is simple and convenient, eliminating the work of cable construction and calibration required for hard wire connection, greatly reducing the workload of on-site construction and minimizing the on-site renovation cycle.

(2) It completely eliminates the shortcomings such as jitter, interference and loss that are easily generated by the contact line of the sliding line. In particular, it solves the fundamental problem of the limitation of the signal transmission amount of the sliding line mode, realizes the full collection of system information, and improves the reliability. And stability, it also brings convenience to operation and maintenance.

(3) Provided a system wireless access point to solve the problem of connecting the self-propelled car system with the ground. In the on-board system debugging, parameter change, fault check and maintenance, it is not necessary to use the previous air operation or remote control, and the system can be completely controlled by wireless clients (such as laptops) anywhere in the wireless system coverage area. Point to operate and monitor.

(4) The system interface is fully open, debugging is simple and convenient, saving development and debugging time.

3. High degree of flexibility and easy expansion

In the future, if you want to add a car group, the control system only needs to add a car control unit and a wireless client.

4. Security system

Through the innovative transformation of the sliding line, we have developed a safety guarantee system, even if the wireless failure, the new sliding line system can guarantee the non-stop operation of the production line.

5. Position recognition system is very advanced

The advanced positioning and identification system has no mechanical wear, no need for reference points, absolute position measurement, real-time detection, and maximizes the intelligentization of the car.

Conclusion

The project has been rebuilt and has reached the goal of increasing production capacity. The project has passed pre-acceptance. The wireless network has been fairly stable since the start of debugging and is the key to the success of this project. Through this project, it is proved that the wireless network communication of Phoenix Contact is reliable, and the application can fully exert its advantages in the automatic control system of the self-propelled car, and the cost performance is very high. In China, the wireless network is used in the painting self-propelled car transport system, especially in the loop self-propelled car renovation project with a relatively long sliding distance, a wide range and a large number of vehicles.

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