Research On The Key Technologies Of Coal Mine Mobile Wireless Power Transmission

The application of wireless sensor networks?WSN?in coalmine underground can greatly improve the monitoring perfermance.However,batteries power the wireless sensor nodes,and the limited capacity of those batteries affects the stability of WSN.With the development of wireless power transmission?WPT?,these problems can be solved.Thus,this thesis focus on the key technologies of WPT application in coalmine underground.First,this thesis propose the application model for underground WPT system,based on the analysis on the domestic and foreign research status and according to the transmission characteristics of the microwave in coalmine underground.Futhermore,this thesis analyzes existing problems of the WPT system working in coalmine and gives the solutions.Secondly,this thesis proposed a method for underground coupling resonance WPT system,based on Helmholtz coil structure.The proposed structure can generate more uniform eletromagnetic field?nearly reach 92%?for the receiver and more convenience for the mobile charging scenario.By the theoretical analysis and simulation,the optimized paramters of the Helmholtz coil structure are given.Through circuit simulation and experiment demonstration,the results shows that the efficiency of WPT system based on proposed Helmholtz coil structure can get over 60%and receive power can get over 0.5Watt,and this is satisfied for underground mobile charging.Secondly,this thesis studys and analyzes the attenuation characteristics of electromagnetic wave in underground tunnel environment,by the testing and measuring data gathering from vector network analyzer in different coalmine underground environment.The data shows that the energy of electromagnetic wave attenuation characteristics is close to the statistical attenuation model,and the transmission power can reach to 10^-3 Watt when the transmission distance is 2 meters.Then,in order to test the performance of the microwave transmission system,this paper designs a rectangular microstrip antenna with 5.8GHz center frequency;through the rectifier filter circuit of the receiving antenna,get the optimal antenna microstrip rectifier.The experimental results show that when the transmit power is 5Watt,the distance of the receiving antenna at 2 meters away,the receiving power can reach3.3mW,which is satisfied for some ultra low power sensor nodes'energy supply.Finally,this thesis propoed an optimal algorithm for microstrip antennas design.Which is aims to solve the optimization problem of frequency offset in the desgin of microstrip antennas.This method uses Genetic Algorthim?GA?to optimize antenna design software,and the optimized results show that the proposed algorithm can improve the design precision and perferamance of the antenna effectively.