| As a new generation sensor network, wireless sensor network is a sort of multi-hop and self-organizing network, consisted of many low-cost micro sensor nodes displaced within the detection area, in the form of wireless communication. Wireless sensor network is one of the four high-tech fundamental industries with merits such as fast distribution, self-organization, strong hidden and high fault tolerance, and is widely utilized in domains of military, environment detection, medical nursery, industry and so on. The development and application of wireless sensor network will provide profound effects for fields of human life and production. However, energy issue, which affects wireless sensor network's function and longevity, is the key problem that restrains the development and application of wireless sensor network. Therefore, it deserves significant economic and social value to solve the energy issue of wireless sensor network and lengthen its longevity.Researchers proposed a series of energy management strategies which just lengthened wireless sensor network's longevity to a certain extent but didn't radically settle down the energy problem. The longevity of wireless sensor network has been lengthened after self-power supply technology was proposed. However, in situations of no environment energy or low environment energy, the application of self-power supply technology is limited. On base of that, the dissertation proposed the method of wireless sensor network active laser energy supply. This method makes full use of laser to transmit energy wirelessly, by transforming the focused light energy into dispersed and well-distributed space light field in working sites to supply energy to multi-node wireless sensor. This method enables wireless sensor network to perform in high-risk places with no environment energy such as large-scale underground oil depots and coal mines, which extends the application domain of wireless sensor network. In this dissertation, the optical model of wireless sensor network laser active-power supply is established and its features are analyzed; the Si solar cell's opto-electronic model is analyzed, on base of which the method of utilizing nano-hole array film to improve solar cell's function is proposed and the optical model is set up; the micro energy depletion collecting system on base of laser's active power supply is designed; in the experiment the feasibility of laser's active power supply is tested and verified and the improvement of nano hole array film on solar energy battery's function is also tested and verified, and the principle and performance of the designed energy collecting system is also tested and verified. The specific details include:1) Set up the physics model of laser transmission in the atmosphere according to Atmospheric Physics, analytically calculate the transmission performance of laser with different wavelength; the calculations indicate the transmission losses of visible laser and near-infrared laser in the atmosphere are less, and the transmission power loss of 1064nm laser is the least in far-distance transmission.2) Brought up forward two methods of transforming single-point laser into space light field: laser excitation phosphor and laser - diffuse reflector. Analyzed the optical properties of the two methods and calculated their efficiency and light field uniformity. Among the two methods, laser excitation phosphor is better in light field uniformity, but lower in efficiency; laser-whiteboard method is higher in efficiency but worse in light field uniformity. Designed and analytically compared two optical structures which can improve laser utilization.3) For the illumination intensity of the space light field from laser active-power supply was weak, the article mainly analyzed different Si solar cell's low light response property and chose various Si solar cells in accordance with various laser wavelengths. Thus, the laser active power supply network, which enlarged the acreage of power supply, was designed.4) Since solar cell's property is of criminal importance in the whole power supply system, the dissertation put forward taking nano-hole array film as solar cell's antireflection coating to improve solar cell's transmission efficiency on base of analysis of solar cell's optical model. In addition, the dissertation analyzed the optical property of nano-hole array film in principle of Rigorous Coupled-wave theory, established the optical model of nano-hole array transparent film solar cell and optimized the optical structure of nano-hole array film. The optimized structure parameters of nano-hole array film are: period a=500nm, filling fraction f=0.2, thickness t=110nm.5) The dissertation analyzed commercial solar cell wireless nodes'structure, on base of which the power harvesting system and wireless nodes of laser active-power supply are designed. The voltage feedback method of tracking solar cell's optimized working point enhanced solar cell's charge efficiency. Meanwhile, the low power loss control circuit was designed, which realized high efficiency and low power loss in the power harvesting system.6) Two power supply systems were set up and their properties were tested, i.e. laser excitation phosphor power supply system and laser-whiteboard power supply system.7) In micro-nano processing method, various periods'nano-hole arrays were fabricated on the transparent film ofΦ200μm Si detector and the corresponding testing system was set up. The results suggested that devices'property was improved obviously in 500nm period; the improvement was about 6% when short circuit electric current was in 400nm-1100nm wavelength and about 15% in the 400nm-600nm wavelength; the open circuit voltage's improvement was about 2%; the nano-hole array film could well enhance Photovoltaic devices'transmission efficiency.8) The designed power harvesting electric circuit was processed and debugged and its property was tested; it proved that the circuit could work well in condition of laser active-power supply illumination (50-100μW/cm2). Wireless nodes based on this power harvesting circuit was processed and practically measured with perfect results.
|
PDF Full Text Request