As a special section of the highway, the highway tunnel determines the difference in brightness between the inside and outside of the tunnel. It has the disadvantages of serious pollution and high noise, which reduces the traffic capacity of the road and threatens the driving safety of the vehicle. In order to improve the traffic capacity of this bottleneck section and ensure the safety of driving, it is necessary to scientifically set up the lighting system . Tunnel lighting is very different from ordinary road lighting. The biggest is to illuminate during the day, and daytime lighting is more complicated than night lighting. During the day when the car driver approaches, enters and passes through the tunnel from a bright environment, various special visual problems will occur: before entering the tunnel, due to the great difference in brightness between the inside and outside of the tunnel, the tunnel with insufficient illumination is seen from the outside of the tunnel. At the entrance, you will see a "black hole"; after the car enters the tunnel from the bright outside, due to the sharp change of brightness, there will be a visual "adapted hysteresis"; at the exit of the tunnel, there is a strong glare, resulting in a very Bright holes reduce the driver's visibility. Therefore, tunnel lighting must solve the visual adaptation problem of the driver entering the tunnel. At present, tunnel lighting designers usually design the lighting by dividing the tunnel into four sections: the entrance section, the transition section, the middle section and the exit section. The length and illuminance of each section are based on the driving safety requirements of the whole year. The design of the maximum illumination in the tunnel is to determine the lamp power and the distribution density of the lamps in each section of the tunnel with the maximum brightness and maximum speed of the year.  On-demand and real-time control of lighting is not possible. In the use of lamps, high-pressure sodium lamps have been widely used due to their long life, good light efficiency and strong fog permeability. New energy-saving lamps have not been promoted due to technical and cost reasons. The above traditional lighting design has a lot of waste of electric energy. This paper is aimed at the current waste of tunnel lighting energy, research on the construction of energy-saving dimming control algorithm and control system, in order to maximize the energy saving of tunnel lighting. .
1 Lighting energy-saving dimming control algorithm
Algorithm principle: According to the traffic volume and the brightness outside the hole, the theoretical demand curve of the brightness in the hole is established, and then the dynamic dimming control of the lamp is performed according to the theoretical demand curve of the brightness in the hole. The entire lighting control output is close to a smooth curve, which can quickly respond to the tracking lighting demand curve, get the best control effect and achieve energy saving.
According to the "Code for Design of Ventilation Lighting for Highway Tunnels" (JTJ026.1-1999), the tunnel lighting design is divided into the following sections: the entrance section, the transition section, the middle section, and the exit section, as shown in Figure 1. Therefore, the calculation of the tunnel lighting theoretical demand curve L in the automatic control algorithm is performed in a segmented manner, and the calculation result is output to the control interface. The entrance section, the middle section and the exit section are straight lines of brightness demand, and the corresponding lamps are 256-level logarithmic dimming. The logarithmic dimming curve utilizes the characteristics of the human eye to be sensitive to low-illumination light, so that the entire dimming area looks like Like linear adjustment. The transition section is the brightness demand curve, and the corresponding fixture is a single 256-level logarithmic dimming. The automatic control algorithm usually adopts the time trigger condition, and re-reads the parameters such as brightness and traffic volume outside the hole every 5 to 10 minutes, and recalculates the lighting demand.
(1) Inlet section brightness requirement Lth(cd/m2)Lth=kÃ—L20 (1) In equation (1): kâ€”reduction factor; L20â€”external brightness, (cd/m2) . The k value in the formula can be determined according to the â€œCode for Design of Ventilation Lighting for Highway Tunnelsâ€ (JTJ026.1â€”1999), and the intermediate value can be calculated by interpolation method, as shown in Table 1. Table 1 Deduction coefficient values â€‹â€‹for different traffic volumes and driving speeds
(2) Middle section brightness requirement Lin (cd/m2) Middle section brightness Lin See Table 2, using the interpolation method to calculate the different traffic volume and the intermediate segment brightness Lin value when calculating the driving speed. Table 2: Middle section brightness values â€‹â€‹for different traffic volumes and driving speeds
In equation (2): xâ€”the distance from the point on the transition to the start of the transition (m); Dtrâ€”the length of the transition (m); v â€“ the average speed (m/s); Dâ€²trâ€”the length of the transition period (m).
(4) Outlet segment brightness requirement Lot (cd/m2)
2 Lighting energy-saving simulation system design
The traditional tunnel lighting is to achieve reasonable lighting of each section, according to sunny day, cloud sky, cloudy sky, heavy cloudy day to strengthen lighting and all-day basic lighting, daylight basic lighting, full-day basic emergency lighting seven modes control , the control method is too Simple, it is impossible to achieve adaptive control of lighting according to parameters such as outdoor environment illumination, traffic flow, and vehicle speed in the tunnel. The lighting effect is not good and the power is wasted. The tunnel lighting energy-saving intelligent control system adds intelligent control links based on traditional lighting, and applies fuzzy control technology to the design of tunnel lighting system, so that the entire tunnel ventilation lighting can automatically adapt to the influencing factors such as vehicle speed, traffic flow and environmental weather outside the tunnel. Changes that reduce unnecessary lighting waste. The use of high-power LED lights on the luminaires to replace the high-pressure sodium lamps widely used at the present stage has truly achieved green lighting. In recent years, high-power LED lighting has a tendency to continuously replace conventional lighting equipment such as high-pressure sodium lamps, and it has the following advantages:
(1) High efficiency. The use of LED lighting under the same brightness conditions consumes only 10% of incandescent lamps and 50% of fluorescent lamps.
(2) Long life. The theoretical life of LED is 100,000 hours, which is 10 times that of fluorescent lamps and 100 times that of incandescent lamps.
(3) Easy dimming control. LEDs have great advantages in dimming performance, enabling digital dimming, especially for special occasions where dimming is required, such as tunnel lighting.
In this simulation system, the model luminaire adopts white LED, each LED power is 1W, the LED forward voltage is 3.5V, and the average current is 350mA at the brightest. The LED dimming control generates the PWM by transmitting the dimming information through the host computer. Pulse to achieve.