Application of intelligent control system in tunnel and road lighting

In recent years, with the gradual development and maturity of tunnels and road construction, lighting has become more and more important as one of the necessary functions, and the requirements for lighting effects are getting higher and higher. The intelligent control system is gradually introduced into the tunnel and road management system, which shows a huge energy saving effect and a significant cost advantage.

As the light source develops from a conventional light source to an LED light source, public lighting becomes more abundant and more reliable. LED can respond quickly to dimming, LED luminous flux and forward current are approximately proportional, and dimming has no effect on LED life. The characteristics of these LEDs provide a powerful guarantee for intelligent control, operation and development of lighting. .

(1) Characteristics and requirements of tunnel and road lighting

Tunnels and road lighting, especially highway tunnel lighting, have the following distinctive features and requirements:

The number of lighting nodes is generally thousands or even thousands of miles;

The management area is large, ranging from one kilometer to more than one hundred kilometers;

Construction installation and maintenance are difficult and costly;

Lighting is related to driving safety and requires high reliability and stability;

Need centralized control;

Based on the above points, the owners of the tunnel and the design, operation, maintenance and other units have put forward the need for intelligent control of lighting. In addition, with the advancement and development of technology, people have also generated new performance expectations and requirements for control systems:

Simple, quick and easy control of all lighting fixtures on a computer or electronic device

On-demand dimming of tunnel luminaires, especially luminaires that enhance section lighting, achieves the goal of eliminating white holes and black holes, and saves energy.

For road lamps, the astronomical clock is calculated according to the latitude and longitude of the installation area of ​​the lamp, and the lights are automatically turned on at sunset and turned off at sunrise. Dimming on demand to achieve energy saving and consumption reduction.

It can quickly and in real-time grasp the working status of all lamps, and timely alarm the abnormal state to improve safety and reduce maintenance costs.

Supports various control modes such as auto dimming, time control dimming, and manual dimming.

(II) Introduction of common intelligent control schemes for tunnels and road lighting

Intelligent control has become a topic of tunnel and road lighting. The intelligent control schemes commonly used in recent years are as follows:

1, loop control (PWM or analog signal)

The twisted pair is used to transmit the PWM signal, and the PWM interface is driven to adjust the output current according to the PWM duty cycle to achieve the purpose of adjusting the brightness.

The advantage is that the PWM interface power supply has a lower price. The disadvantage is that only the circuit dimming can be performed, and the single lamp can not be dimmed; no data communication can control the state of the lamp; the power supply driver has no intelligent protection mechanism; the position of the regional controller is limited, and The quantity demand is large; the work of twisted pair laying is large.

2, Dali bus

The Dali signal is transmitted by twisted pairs, and the Dali power supply on each luminaire has a separate address to respond to commands sent to itself, such as dimming and returning parameters.

The advantage is that the Dali protocol is mature and reliable, and the disadvantage is that the Dali protocol is mainly suitable for indoor lighting control with dozens of lamps. In the tunnel of several thousand lamps, the number of regional controllers is greatly increased; the communication speed is very slow. Only 1.2Kbps will result in a long response time of the control command; the interface circuit can only use analog circuit design, there is no mature, reliable, low-cost chip support; the bus laying workload is large.

3, RS485 bus

The twisted pair is used to transmit the RS485 signal, and the power driver on each luminaire has a separate address to respond to the command sent to itself, such as dimming and returning parameters.

The advantage is that RS485 bus communication technology has been used for 30 years, and there are abundant, low-cost, mature and reliable interface chips with multiple performance specifications; the single bus has a long communication distance of up to 1200 meters, which can greatly reduce the use of the tunnel site. The number of regional controllers; the bus communication rate is relatively high, generally 9.6Kbps ~ 115.2Kbps, the disadvantage is that the bus laying workload is large.

4, power carrier (PLC)

The power line is used to transmit digital signals, and the power driver on each luminaire has a separate address to respond to commands sent to itself, such as dimming and returning parameters.

The advantage is that there is no need to lay control lines. The disadvantage is that the current narrowband PLC communication rate is below 5.4Kbps, and the speed is slow; the grid noise, especially the impulse noise, is very disturbing to the PLC; the PLC cannot be realized across the transformer, so the number of regional controllers Also a lot.

5, wireless

Following the IEEE802.15.4 protocol, the digital signal is transmitted by the radio frequency, and the power driver on each luminaire has an independent address, which will respond to the commands sent to itself by dimming and returning parameters.

The advantage is that there is no need to lay control lines; the communication rate can reach 250Kbps; the area controller installation position can be arbitrarily specified, and the required number is small; the disadvantage is that an area controller and power driver need to install an antenna.

(3) The main requirements of the intelligent control communication protocol

All intelligent control solutions are inseparable from the support of communication protocols, which are the cornerstone of all functions. However, no matter whether it is foreign or domestic, there is no mature, reliable and powerful mainstream communication protocol in the field of road lighting.

In response to the above situation, Mingzhi began to visit and investigate related tunnel lighting design units, tunnel lighting maintenance units, construction units and major lighting design and production companies in 2010. After integrating the needs of each family, we summarized some of the main requirements for the communication protocol for tunnel lighting intelligent control:

1. The protocol needs to be compatible with a variety of communication methods, including bus communication, wireless communication, power carrier communication, etc., in order to facilitate users to select a suitable communication carrier for different environments.

2. The protocol needs to support as many address assignments as possible to reduce the number of centralized consoles on site, so as to reduce construction difficulty and cost.

3. Need to support single-lamp control, to achieve different functions for different types, different functions, different manufacturers of lamps can be dimmed.

4. Need to support multicast dimming, broadcast dimming, flexible grouping, and rapid dimming

5. Support scene dimming to achieve automatic dimming according to external environmental parameters

6. It is necessary to support two-way communication, query the status of each lamp's voltage, current, temperature, etc., and judge the lighting status function.

7. Support the communication link monitoring and judgment function to determine if any nodes are not in the control area.

8. The agreement needs to support the online upgrade function to minimize the customer's post-maintenance and upgrade costs.

9. The protocol needs to be simple and reliable, suitable for low-cost hardware design.

In response to the above research and research results, combined with Mingzhi's R&D experience in the field of industrial control, we were commissioned by the Shanghai Construction and Communications Commission in 2011 to work with the LED lighting working group and other units to design a suitable tunnel lighting field. Intelligent control communication protocol LCP-SH. This agreement is an open agreement. After two expert review meetings organized by the Shanghai Construction and Communications Commission, it has become the local standard for tunnel lighting control systems in Shanghai.

The actual cases of using this control protocol in the past three years include the lighting renovation project of Dalian Road Tunnel in Shanghai, the lighting renovation project of Tangling Tunnel in Yongtaiwen Expressway, the National Highway of Guangdong Guangzhu West Phase III, the intelligent control pilot project of Shanghai Shenchang Road, and the Zhangzhou Expressway. Reconstruction project, Yinshuang tunnel reconstruction project and other projects. The cumulative number of control nodes has reached more than 30,000, and the implementation includes bus communication and wireless communication. Powerful, stable, and recognized by the owners.

(4) Comparison of LCP-SH with other existing lighting control protocols

(5) Typical configuration of control system following LCP-SH protocol

In the tunnel, the typical configuration of the LCP-SH protocol control system is shown in the figure below. The server of the control center and the area controller of the tunnel site are connected by Ethernet. Due to the long tunnel distance, the optical cable in the tunnel is generally used as the transmission medium. The area controller and the intelligent drive, single lamp controller, illuminance monitor, traffic flow detector and other equipment rely on RS485 bus or RF wireless connection to transmit digital signals. This signal follows the LCP-SH protocol.

In road lighting, the typical configuration of the LCP-SH protocol control system is shown in the figure below. The control center server and the road site area controller are connected by the wireless carrier's digital communication service; the area controller and the intelligent drive, single lamp controller, illuminance monitor, traffic flow detector and other devices rely on RF signal or PLC communication connection. A digital signal is passed, which follows the LCP-SH protocol. This configuration can greatly reduce the cable laying cost and construction period of the road control system and reduce the construction difficulty.

The control software and database are installed on the server. The user can log in to the server through the Ethernet using a computer or a handheld terminal. Through the operation of the software on the server, the monitoring and management of all the lamps on the road can be visualized, simply and quickly completed.

(6) Conclusion

With the application of intelligent control systems in tunnels and road lighting, energy conservation and consumption reduction will be effectively realized, and operation and maintenance costs will be reduced. In addition, reasonable lighting control will effectively improve lighting effects, thereby ensuring driving comfort and safety. It is conceivable that the extensive use of intelligent control systems will help tunnels and road operations achieve real safety, efficiency, energy saving, low consumption, and bring greater social and economic benefits.