Unmanned Aerial Vehicles Research On Laser Wireless Energy Transfer Charging Strategy

Unmanned Aerial Vehicles(UAVs)have many advantages such as simple control,low cost,powerful,safe and reliable,and are widely used in both military and civilian fields.However,due to the short endurance,the application and development of UAVs in various fields are severely limited.In order to solve the problem of short endurance,research institutions and experts and scholars have proposed a variety of ways.Among them,laser wireless energy transmission technology uses laser as the energy carrier,which can replenish electrical energy for UAVs over long distances in real time,and the energy receiving device is small,which does not affect the load and execution of UAVs.At the same time,the wavelength of laser is in the visible and near-infrared wavelengths,which will not interfere with satellite communications.At present,laser wireless energy transmission technology has achieved substantial success in remote wireless charging technology for UAVs,but the overall energy transmission efficiency is low,in the range of 10% to 25%.To address this problem,this paper focuses closely on improving the efficiency of laser wireless energy transmission,and the main research contents are as follows.Firstly,the current research status of laser wireless energy transmission technology is introduced,focusing on the transmission efficiency of this technology,and the research status of laser wireless energy transmission efficiency improvement is introduced,along with the working principle,classification and selection principle of lasers and photovoltaic cells,and laser tracking and aiming system.Secondly,an equivalent model of the PV cell is established to simulate and analyze the effects of irradiance and temperature on the output curve of the PV cell,and to summarize the output characteristics of the PV cell under different irradiance and temperature.At the same time,the output curves of PV arrays with series-parallel,fully crossed and bridge structures are compared and analyzed under uniform and non-uniform distribution of irradiance.When the irradiance is uniformly distributed,the output curves of the three electrical connection structures are basically the same;when the irradiance is not uniformly distributed,the output power of the PV array connected with the fully crossed structure is the largest,which can effectively reduce the electrical mismatch loss caused by uneven irradiance.Due to the Gaussian distribution of laser energy,the irradiance received by each cell in the PV array is inconsistent.In order to further reduce the mismatch loss between PV cells and improve the photoelectric conversion efficiency of PV arrays,the reconfiguration design of PV arrays with fully crossed structure is based on the principle of minimum balance difference,and the effectiveness of the reconfiguration method is verified by simulation on 5×5 and 6×6 PV arrays,and the maximum output power of PV arrays is increased by 29.13% and 32.25%,respectively,compared with that before reconfiguration.Finally,a model that can reflect the relationship between PV cell material,temperature,irradiance and laser wavelength and PV cell output is established to estimate the temperature of PV cell under different irradiation,and the power loss model when laser is transmitted in the atmosphere with oblique range is also established to analyze the relationship between the emitted power of the laser and the current at the maximum power point of PV array output,to design a five-stage constant-current charging scheme with closed-loop control,and to closed-loop control and open-loop control modes to analyze the laser energy usage.Under the completion of the same power replenishment,the five-stage constant-current charging with closed-loop control can reduce the use of laser energy by a maximum of 13.99% and a minimum of 1.05% compared with the open-loop control,i.e.,improve the utilization of laser energy and enhance the energy transfer efficiency.