Industrial equipment and instrumentation wireless remote transmission technology solutions

Industrial equipment and instrumentation wireless remote transmission technology solutions

I. Overview

Enterprise informatization is an important means to enhance the competitiveness of enterprises. Realizing the informatization of industrial enterprises will effectively promote the adjustment of industrial structure and the optimization and upgrading of industries. It is an important basic work to promote economic development and social informatization. The establishment of a complete information system is indispensable in the information transformation. In the production process, the data collection of on-site production equipment and instrumentation provides the basic data source for the manufacturing execution system and the enterprise resource management system. It is an enterprise informationization. basis.

Currently, methods and interfaces for industrial field data collection are various and can be roughly divided into wired and wireless. The wired method mainly includes Profibus-DP fieldbus, RS-485, etc. The wireless methods mainly include the GPRS method and the Zigbee protocol method.

In accordance with its own technical characteristics, Purcell Communications provides a set of wireless remote transmission technology solutions, that is, wireless remote transmission technology solutions based on the PSS wireless ad hoc network. The collection and analysis of serial data is completed without affecting the normal operation of the existing production equipment. The data required by the user is extracted, and the data is sent back to the data server through Precise's precise transmission wireless network. Wireless networking equipment consists of PT-10 series wireless devices, wireless routers (optional), and base stations to complete the establishment of wireless networks and implement ad hoc networks. The computer data receiving software adopts the B/S structure, stores the collected data in the database, and provides the website browsing function to facilitate the user to browse the data. At the same time, the software can interface with other software and send data to other systems.

Second, remote transmission technology based on wireless ad hoc networks

1, the system composition

1 data acquisition and transmission module (hereinafter referred to as acquisition node). Each industrial equipment (such as flow meters, control cabinets, etc.) is connected to a data acquisition and sending module, which is responsible for collecting field data and sending it wirelessly.

2 data receiving module (hereinafter referred to as receiving base station). Placed in the control and monitoring center, you can also send data directly to the remote monitoring center through the Internet.

3 routing module. Optional. In the case of low signal strength, long distance, or other influence on signal transmission, the reliability of signal transmission can be enhanced by adding routing methods.

2, the working principle

The data acquisition module is connected to the device through the Modbus interface, collects the device data at regular intervals (specified by the server), and sends the data to the outside by wireless. Each acquisition node can transmit data in the mesh network and can also be transmitted as other nodes. The routing node in the path, and can receive the control commands issued by the server (such as switching valve commands) through wireless.

After receiving the data, the data receiving device sends the data to the monitoring center computer for storage through the standard interface, and can also be sent to the remote control center through the Internet. For situations where the signal is weak or there are many obstacles, the wireless coverage of the area can be implemented by installing a wireless router, and the stability and reliability of transmission can be improved.

For different needs, our company provides two data receiving base station access methods.

The first kind, for the situation that requires monitoring data in the industrial field control room, the data receiving device provides a standard RS-232 serial interface or USB 2.0 interface directly connected to the computer, real-time monitoring of device status through software and can issue relevant control commands . The remote control center can use the Internet to access the control room database data through verification.

In the second case, for data monitoring only at the remote control center, the data receiving device provides a standard network interface. The TCP/IP protocol is used to send data directly to the remote server over the Internet, or to use the GPRS wireless mode.

3, program advantages

1 strong real-time, can continuously read device data.

2 It has high efficiency, and it is automatically completed from collection to statistics without manual intervention.

3 Zero cost of communication, wireless use of free bands, no registration, no communication fees.

4 The use of automatic frequency hopping technology, stable and reliable communications, anti-interference ability, can achieve a 99.9% read success rate.

5 The network node has the characteristics of self-organizing network, automatic relay link function, and wide network coverage.

6 The control center can set the frequency via wireless settings.

7 good system scalability. When the scale of production is expanded, the number of collectors and concentrators can be increased accordingly to complete the expansion of the system.

Fourth, the program comparison

1. Comparison between wireless solutions and cable solutions

Wired way

Wireless mode

Introduction

Through the field bus and other methods, the data will be transmitted to the collection office for analysis and storage.

Use wireless transmission mode to transmit data through a star network or Mesh network.

transfer speed

High-speed transmission

Faster to meet general needs

Transmission reliability

high

Higher

Construction difficulty

Big. Need to plan wiring, preset interface, line detection and line expansion and other work.

small. Just connect the wireless acquisition module to the device.

Construction cost

Mainly for the wiring costs and signal line costs.

Wireless acquisition module costs.

Maintenance cost

Signal lines are prone to failure when the industrial site environment is harsh, making inquiries difficult.

The failure rate is low, easy to query when there is a fault, and generally has a fault alarm function.

2, a variety of wireless solutions

The current industrial wireless communication network is based on point-to-point data transmission and a star network structure. The network protocol uses a method in which a master station polls each slave station and a slave station sequentially uploads data, and the network transmits on a fixed channel. This method has the following problems:

● The network does not support relay transmission. If obstacles exist, multiple star networks must be formed, resulting in complexity and reduced reliability.

● Power consumption is high. All slave stations must be in listening mode and are not suitable for battery-powered applications.

● Fixed channels are susceptible to other noise interference, reducing reliability.

Pusai's wireless network uses a multi-channel and time-synchronized technology solution. In a wireless network, each node switches on multiple channels according to its default pseudo-random sequence, while dividing the time into multiple time slices. The nodes select different time slices in each super frame cycle according to a predetermined sequence. The channel wakes up and sleeps at other times. The main advantages of this technology are:

● Multi-channel technology can effectively avoid the common single channel interference in the common band. Because all 16 channels are used for transmission, neighboring nodes can communicate on different channels at the same time, which greatly improves system communication capacity.

● Time synchronization technology makes the communication delay predictable, controllable, and reduces the probability of data collisions. At the same time, since nodes can sleep and wake up synchronously, power consumption is effectively reduced and a low-power router is implemented.

● reliable and stable transmission mode. All nodes simultaneously maintain multiple communication paths. Once a path is blocked, an alternative path can be used for transmission immediately.

The technology is at the international advanced level. At present, well-known automation equipment manufacturers such as Emerson and Honeywell have adopted similar wireless technology solutions to add wireless capabilities to their products. We are committed to improving the reliability, stability and anti-jamming performance of our products in industrial environments. We have adopted various patented technologies such as redundant paths, breakpoint retransmissions, and end-to-end acknowledgement to meet the stringent requirements of industrial wireless networking. In the long-term fatigue test, our network achieves 99.9% or more transmission success rate. At the same time, in the case of sending packets every 30 seconds, the average current is as low as 1.5 mA, and it can work continuously for at least three months in the case of two AA batteries.

Compared with other solutions, our program features and advantages:

Pusai Industrial Wireless Sensor Network

Wi-Fi (802.11) network

GPRS network

Zigbee network

Communication operation costs

None (common frequency band)

None (common frequency band)

Yes (SMS or GPRS network traffic charges)

None (common frequency band)

Power consumption

Low (using full-network synchronous hibernation technology, 5th battery power for 3-6 months)

High (laptop battery power 2-3 hours)

In the (mobile phone battery power supply 1-2 days)

The 5th battery high-power router node can supply power for 2-3 days, and the low-power terminal node can supply power for 6 months

reliability

High (multi-channel transmission, redundant path retransmission, guarantee 99.9% data transmission reliability)

general

Relies on operator networks

Weak (only on a single channel network and susceptible to interference from other networks)

Networking capabilities

Strong (multi-hop relay transmission, ad hoc network, self-healing, bypass obstacles, increase transmission distance)

Weak (only support star network structure)

Relies on operator networks

The number of network hops and the number of hops per node need to be determined in advance

Working frequency

All ISM free bands, such as 2.4GHz, 800MHz, 470MHz and 433MHz, can be flexibly configured according to customer requirements

2.4GHz

Mobile, China Unicom authorized frequency band

2.4GHz

User customization

Nodes have RS232, RS485, CAN bus interface, 8 analog I/Os and 8 digital I/Os, can realize digital transmission, sampling and control functions according to customer requirements

low

low

According to different manufacturers

V. Appendix:

1. Abbreviations

2. Terms/Definitions

Wireless ad hoc network

Wireless ad hoc networks, or wireless Mesh networks, also known as "multi-hop" networks, are new wireless network technologies that are completely different from traditional wireless networks. In a traditional wireless local area network (WLAN), each client accesses the network through a wireless link connected to the AP. If users want to communicate with each other, they must first access a fixed access point (AP). This kind of network structure is called single-hop network. In a wireless mesh network, any wireless device node can act as both an AP and a router. Each node in the network can send and receive signals. Each node can communicate directly with one or more peer nodes. The biggest benefit of this architecture is that if the most recent AP is congested due to excessive traffic, then the data can be automatically rerouted to a nearby node with less traffic. And so on, the data packet can also continue to be routed to the nearest next node for transmission according to the network conditions until reaching the final destination. This access method is multi-hop access.

Mesh access point

Mesh access points provide links between Mesh networks and backbone networks. Other Mesh devices automatically find the route to the access point.

Mesh router

Mesh network devices that provide multi-hop routing.

RS-232 interface

The computer serial communication port physical interface mode realizes the data transmission between the external device and the computer.

RS-485

Data signals use differential transmission, also known as balanced transmission.

Modbus

The Modbus protocol is a common language used on electronic controllers. Through this protocol, controllers can communicate with each other, controllers via a network (such as Ethernet), and other devices.