When it comes to factory automation, to be aware of the status of the equipment during operation in real time is a very important part for it may affect production process and product quality. In the conventional factories, the operation environments may have problems such as: high temperature, heavy equipment, sour gas, and other dangerous factors, etc. Therefore these factories most adopt semi-automated or fully automated devices to ensure the stability and security during the production process in order to reduce the risk of industrial accidents. On the other hand, the operation status of the devices may require to be sent to the control room in scheduled time for real time monitoring so that the related personnel can perform necessary maintenance in time to extend the life of the devices, and reduce the incidence of sudden machine shutdown as well.

However, the deployment of wiring for long distance is a big issue when building the architecture of such monitoring system. The complexity of various environment factors cause difficulty in wiring. Therefore, how to reduce the wiring has been an important issue for automation applications.

In order to solve the problem, in recent years, ICP DAS has been working on ZigBee wireless technology and provides integrated solutions for wireless control applications. ZigBee features wireless, low power consumption, compact design, easy-to- setup and mesh (mesh) network etc. It is particularly suitable for used in low-speed and limited- space area wireless transmission system. By using wireless ZigBee technology-based monitoring & control system, it can save the cost of wiring, and the transmission will not be limited by the distance between each factory site; the operation status of the equipment can be monitored in real time. The following section will illustrate how to apply ICP DAS ZigBee wireless technology to fulfill wireless monitoring application in a conventional factory.
 

A. ZigBee features and applications:

Zigbee Alliance was established in 2001 and was committed to build an international standards-based wireless network protocol. ZigBee wireless transmission technology is in line with IEEE802.15.4 standard, the operation frequencies are: 868MHz, 915MHz or 2.4GHz; featuring:

1. Low power consumption: using general battery can last a few months or even a few years.
2. Low cost: low cost in manufacturing, installation and maintenance.
3. Low data rate: generally used for monitoring and control of small amount data transmission.
4. Large network capacity: support a large number of transmission nodes.
5. High reliability: self-repairing network topology




ZigBee network topology includes: Mesh, Star and Tree, etc., is shown as Figure 1 and is composed by three roles:
1. Coordinator (Host): initiate a ZigBee network by selecting the working channel of the network and personal area network identification (PAN ID). Once the network starts, the router and the end device will be able to join the network.
2. Router (Repeater): to assist the Coordinator and End Device to transmit data or routing data, and to allow other routers or end device to join the network.
3. End Device (Slave): not involved in data routing, so it can sleep when not transmitting or receiving data. When joining a ZigBee network, the parent-child relationship is formed between the devices, the added device is the child device and the device allows to join the network becomes parent device.

Three basic concepts for ZigBee networking:
1. Each Node requires the same PAN ID and communications channel.
2. There is only one Coordinator in a ZigBee network.
3. Each node requires a unique Node ID.
Currently ZigBee applications include: consumer electronics, energy efficiency and management, health care, home automation, communication services, building automation and industrial automation. For more detailed information please visit ICP DAS ZigBee webpage:
https://www.icpdas.com/en/product/guide+Wireless__Communication+ZigBee+Converter#609
 

B. System Architecture and Operation

Description and Requirement of the System:
The scenario is located in the Kaohsiung area in Taiwan where lots of factories produce raw materials for iron & steel and chemical industries. One conventional factory requires using heavy machine to hang the semi-products and wash the semi-products by acid pickling liquid. For the pickling process is highly dangerous, it usually use automated hanging devices to perform such operations. And during the pickling process, it is strictly forbidden for unauthorized personnel to enter the site to assure the safety and smooth going of the production process. There are more than 20 hanging devices operating in one track. Each hanging device performs different production process according to the logic rule in its PLC. For the maintenance personnel cannot always keep an eye on the warning light of the hanging device and the environment is noisy that one cannot tell the operating status by the sound. The hanging devices share the same track, if one hanging device encounter unusual situation, the entire production process will be affected. Therefore the customer want to build a system that the main controller in the control room can automatically send requests for the operation status, production process and operation location of various parts from the PLC of each hanging device at scheduled sequence, so that the entire production process can be monitored, possible conflict between each hanging device can be avoid and errors can be ruled out and fixed in real time to ensure smooth going production process.

For the hanging device will move backward and forward to different locations, it is not feasible to deploy wiring between the hanging devices and the control room, in addition, there are metal girders and cranes all over the place, the obstacles in between may affect the transmission of wireless signals and even cause interruption of the communication.

Solution:
The ZigBee wireless communication products of ICP DAS ZT-2000 series are used in this scenario to solve the problems mentioned above. The system architecture is shown in Figure 2. In the control room, the host PC is connected to ZT-2570 via the Ethernet interface and the signal from host PC is converted to ZigBee wireless signal. Each hanging device is equipped with a ZT-2551 module that can convert ZigBee signal to RS-232/RS-485 signal. The received ZigBee signal is converted to RS-232 signal and read by the PLC. For the data rate of the request command sent from the host PC in the control room and the received response information from the PLC on the hanging device only involve small data exchange; Zigbee solution can be used in this scenario.

The ZT-2570 offers VxCOMM communication technology; therefore when the host PC in the control room communicates with PLC via COM port of RS-232; by using VxCOMM technology, it does not require to make any modification on the software of the host PC. The VxCOMM driver will automatically transform the data of COM port to Ethernet data and send to ZT-2570 (ZigBee coordinator), and the ZT-2570 will send the data to the ZT-2551 connected to the hanging device. When the data size of the response data that PLC sends to the host PC exceed the maximum data allowance of the ZigBee wireless transmission packet, the ZT-2570 can deliver it by dividing the data into packets and compose it back to original data before sending it to the host PC to avoid possible error.

Because each ZT-2551 connected to the ZigBee network plays the role of a router; it can perform data transmission. When encountered any obstacle that cause the wireless information of one ZT-2551cannot be sent back to the ZT-2570, the information can be sent by other ZT-2551 on other hanging devices. Therefore there is no additional ZigBee repeaters required.


Figure 2 Architecture of the Hanging Devices Monitoring System

 

C. ICP DAS ZigBee Product Solution

ICP DAS offers a complete ZigBee solution, including Converter, Repeater, I /O, and other related modules. The users may choose products specifically meet their requirements. For more detailed product information, please visit ICP DAS ZigBee webpage:
https://www.icpdas.com/en/product/guide+Wireless__Communication+ZigBee+Converter#856

 

PROFINET Converter & Gateway Products Comparison Table

 

D. ICPDAS ZigBee Wireless Product is perfect for Factory Wireless Monitoring Applications

ZigBee product is one of the ICP DAS wireless product lines providing a variety of ZigBee converters, gateways and I/O modules. They can be integrated into the PC/HMI or ICP DAS PAC to build specific monitoring systems for applications in all fields. Using ZigBee to implement a monitoring & control system in the factory, it the monitoring of the operation status of the remote devices can be easily done and is flexible when requires expansion of the system.

ICP DAS has been working on ZigBee technology and products for years and is dedicated to provide a variety of specific solutions for applications from all fields. We keep on developing products that perfectly meet our customers’ requirements. With extended experiences in wireless technology and industrial communication, ICP DAS provides solutions that are able to integrate different combination of industrial devices. ICP DAS is committed to continue developing solutions to challenge all kinds of difficulties that our customer encountered.