Research And Implementation Of The Sunlight Conveyer With Polar Axis Tracking

Aiming at the situation of highway tunnel lighting system currently used the conventional power with high power and energy consumption, a lighting device using sunlight directly for the tunnel’s enhanced lighting has been designed, which not only avoided the inherent performance deficiencies of the sunlight conveyer’s poor stability caused by uncertainty sunlight, but also efficiently used the solar energy to achieve the purpose of energy-efficient lighting. However, using the existing ordinary sunlight conveyer in tunnel enhanced lighting systems has the application bottlenecks which are high optic fiber costs(cost accounting systems’ 3/4) and low light transmission efficiency of long-distance(≥50m), then the sunlight conveyer of free optic fiber with polar axis tracking has been designed. It has used the key technologies of driving device with polar axis type and closed-loop tracking control system for transmitting the changing sunlight into the tunnel from the arch upper air space with fixed direction under eliminating the need of optical fiber, then scattering sunlight with diffuse mirror group which are mounted on the top of tunnel at different depths and heights to complete the access road’s enhanced lighting. The transmission efficiency has been nearly approached to 90%, and the system cost has also been reduced to 1/3. The main contents of this paper are:(1)Scheme design of the sunlight conveyer with polar axis trackingAccording to the actual requirements of highway tunnel lighting system using sunlight directly, the sun conveyer with polar axis tracking has been designed. It mainly includes the condensing-dimmer and light guide means which are installed outside of the tunnel, and diffuse reflected mirrors installed inside of the tunnel. The condensing and dimming mirror and light guiding mirror each equipped with the driving control systems are composed of condensing-dimmer and light guide means. Combined with the function of condensing-dimmer’s fixed-point outputting, the driving device with polar axis type has been designed;(2)Design of the condensing-dimmer’s tracking control system with polar axis typeThe transmission of light flux cannot meet the requirements of road illumination since the restrictions of tunnel’s arched cross-sectional area, by comparing the advantages and disadvantages of the existing tracking method, the Fresnel converging-dimmer equipped with tracking system of polar axis type has been designed. It has been used for gathering the incident sunlight and re-adjusting to get the enhanced and parallel sunlight, then output to the light guides. STC12C5A60S2 has been chosen as a control chip for completing the tracking system’s optical signal acquisition and processing, motor selected and driving control circuit, buttons adjusting and displaying circuit, and the corresponding design of software module;(3)Design of tracking scheme based on the directional output of light guide meansIn order to drive the light-guiding mechanism for outputting the directional sunlight with adjustment of optical path, the method of using the coarse, fine, slight-tuning with three sensors composed of the priority different spatial signal acquisition structure has been designed. It is used to solve the tracking system’s "off-target" since the signal has accessed to the "blind spots" which caused by the optical signal sensor installed inside of the tunnel during the normal operation, and the stability of working system has been ensured;(4)Experimental testing of prototype’s each module and analysisDebugging and testing the designed sunlight conveyer prototype, and analyzing of the obtained data, the Fresnel transmission condensing-dimmer’s light convergence ratio has been nearly approached to 7.19, and the resulting data of optical transmission efficiency and tracking accuracy have also been nearly reached to 81% and 0.1°, which both meet the expected results. Compared with the various types of common tunnel lighting system, it shows that not only the high-precision tracking and outputting the directional enhanced parallel light have been achieved with using this sunlight conveyer, but also the sunlight has been transmitted more efficiently for directly illuminating in the tunnels’ transition sections.As a green sunlight directly illuminating device of high efficiency and low cost, the use of driving device with polar axis type which equipped with closed-loop tracking control system and prototype with Fresnel lens validated by experimental data have been achieved the goals. It has a good response to the call of energy saving when used in the highway tunnel entrances and exits segment and generalized to the underground garage, residential nightside houses which also need lighting during the day, and above workings have laid the foundation for the later industrialization.