Brief introduction of forest fire prevention monitoring system

With the continuous development of afforestation, the area of forest land and forest stock increase year by year, and fire prevention is the primary task. Forest fires are characterized by suddenness, randomness of disasters and huge losses in a short time. Therefore, in the event of a fire, fire-fighting measures must be taken at an extremely fast speed. Whether the fire is put out in time and the decision is proper depends on whether the forest fire behavior is discovered in time. Therefore, efforts are being made at home and abroad to prevent, reduce and control forest fires.

In view of the actual situation of forest coverage in China, due to the complex terrain conditions in forest areas, the usual wired transmission mode is not applicable. After several years of project practice, Zhongtian Huayi Company put forward a set of feasible solutions-wireless image monitoring system for forest fire prevention.

The wireless image monitoring system for forest fire prevention consists of forest monitoring management command center system, wireless transmission system, camera and lens system, pan/tilt control system, power supply system and iron tower. The forest monitoring and management command center system is the image display and video control center of the whole system, with remote control function, which provides comprehensive, clear, operable, recordable and replayable real-time images for command and dispatch personnel. The forest monitoring and management command center system also has the interface function with the superior forestry bureau and the provincial forestry department.

Key points of system design

In order to realize real-time monitoring in complex forest environment, the system should consider the following characteristics:

1, the monitoring range is large due to the environment. In the choice of monitoring points, first, the camera should be installed at the commanding heights of the forest, requiring a wide field of vision, accessibility and a large monitoring angle. Set as few monitoring points as possible, and the forest area covered by each monitoring point is as large as possible. If there is a dead angle, more monitoring points can be added.

2. All-weather monitoring. The monitoring point should work around the clock, which requires that infrared sensitive color cameras should be selected when choosing cameras; The lens should be used day and night, and the activities of outsiders within 3 kilometers can be seen clearly; Pan/tilt needs an outdoor integrated pan/tilt driven by screw. In order to reduce the jitter of long-distance images, the installation of cameras should also ensure stability.

3. The transmission link is the most critical link in the system. Because of the characteristics of forest fire prevention monitoring, it is impossible to use wired or optical cable for transmission, so the most ideal way is wireless transmission. Wireless transmission mode has the advantages of simple construction, low cost and less one-time investment, so it is undoubtedly the first choice for the transmission link of monitoring system. Images can be transmitted clearly in real time, the transmission frequency can be selected, and the power can be configured according to the transmission distance and different natural conditions on site. If you encounter obstacles, you can set up a relay (image/data) system.

4. Forest fire prevention involves a wide range and a long distance. The forest areas that need to be monitored are far from the monitoring management center, and the distribution is relatively scattered. Usually, the mixed networking mode of 2.4G and 5.8G products is adopted. 5.8G point-to-multipoint networking mode is adopted for densely distributed remote points; Individual remote points can be networked with 2.4G products.

5. Power supply of front-end equipment. In forest fire prevention monitoring system, it is very important to provide stable power supply for front-end equipment. Therefore, when we choose the monitoring point, we try to choose the place with fixed power supply, but we will consider that the monitoring point with power supply is far from the center, which shows the advantages of long-distance transmission of wireless equipment. If you can't find a suitable activity point, you can only use solar energy to supply power.

When using solar power supply, we must first choose the products of professional solar power supply companies; Secondly, the solar power supply system should at least ensure that it can provide 24-hour power supply for all front-end equipment at each monitoring point in rainy days. The solar power supply system consists of a solar cell array composed of solar cell modules, a solar charging control device, an inverter and a storage battery. The solar cell array converts solar energy into electric energy in sunny days, supplies power to the load and charges the battery pack at the same time; When there is no light, the battery supplies power to the load.

6. Lightning protection and grounding should be safe and reliable. The weak link of forest fire prevention monitoring system is the lightning protection and grounding of front-end equipment, which directly affects the safety and reliability of the whole project. Ignoring lightning protection and grounding will bring great losses to users. The principle of lightning protection is that all equipment should be installed within the protection range of lightning rod, and the grounding resistance should not be greater than 10 ohm. If engineers do not have the ability of lightning protection and grounding, it is recommended to cooperate with local professional lightning protection and grounding companies. The characteristics of lightning protection and grounding are determined by the environment, which affects the actual lightning protection effect. It is not feasible to design lightning protection and grounding without considering the specific situation of the project site.

7. In order to find the fire in time, the front end needs smoke sensor and alarm linkage equipment. At this point, it is necessary to pay attention to:

(1) Connect the sensor and alarm linkage equipment to the 485 line of the video encoder correctly.

(2) Set the 485 address.

(3) Front-end and back-end control protocols must be consistent.

(4) The baud rates of the far-end and back-end devices must be consistent.

8. The center monitors the working status of front-end equipment in real time. Because the whole monitoring front-end equipment is located in the mountainous area, it is extremely inconvenient to maintain, so the center should be able to grasp the working state of the front-end equipment at any time, which will play an important role in guiding and analyzing the maintenance work. On the one hand, it will reduce the intensity and cost of the whole system maintenance, on the other hand, it will protect the interests of both users and engineers.

9. Back-end monitoring command and control systems usually view images in a multi-client manner. On the premise that the wireless link bandwidth is sufficient, all images should be transmitted by multicast to save the wireless link bandwidth and ensure the stability of the wireless link. At this time, the switch in the monitoring center must have multicast forwarding control function to prevent broadcast storm.

Requirements for wireless transmission links

When selecting microwave products, the following factors must be considered to ensure that reliable and efficient links can be established in harsh and complex forest environment, thus ensuring the performance of the whole system:

1. Meet outdoor products.

2. Support long-distance and point-to-multipoint large-scale networking transmission, provide high enough link bandwidth and support bandwidth allocation.

3. Support the forwarding control of video multicast packets.

4. The stability and reliability of wireless transmission are high.

5. Simple installation, powerful management function and low maintenance cost.