| Laser wireless energy transfer technology has attracted a lot of attention and research as a flexible and convenient way to transmit energy wirelessly.In the field of UAVs,this technology can be used to provide power to high-altitude UAVs to extend their endurance.However,current research has mainly focused on the efficiency of energy transfer under fixed operating conditions,and there is a lack of research reports on the effect of moving targets on energy transfer efficiency under different positions and attitudes.In addition,the design of laser wireless energy supply systems and photovoltaic arrays need to be studied in depth,while the analysis mechanism of laser wireless energy transfer loss is not yet mature enough to diagnose the system based on the available results.Therefore,this paper aims to fill this research gap and investigate the power loss mechanism in the process of laser wireless energy transfer and its system optimization design method.In this study,the dynamic characteristics of a laser wireless energy transfer system based on a fiber-coupled semiconductor laser are investigated,using a multi-rotor UAV as a typical case of a moving target.The main research work and conclusions of this paper are as follows:1.The basic principles of the UAV receiving array are proposed,the design method of the UAV laser receiving array is given,the electrical model for the physical simulation of the system,the thermal calculation model,and the irradiation model reflecting the energy distribution of the receiving array spot are established,and the real-time prediction of the laser wireless energy transfer state of the moving target is realized.Based on this,a loss analysis framework is proposed in this paper,which refines the total energy transfer efficiency into atmospheric transmission efficiency,cut-off efficiency,Gaussian filling efficiency and photoelectric conversion efficiency.2.Based on the theoretical basis of the propagation characteristics of the laser beam,the design theory of the expanded beam collimation system based on the scaling factor is proposed,the corresponding fixed-focus system and zoom system are designed,and the energy transfer characteristics are explored in depth,and the recommended array design radius is given for different orders of magnitude of the designed energy transfer distance.The results show that the cut-off efficiency of the zoom system is better than that of the fixed-focus system in the energy transfer range of 5-100 m.When the energy transfer distance is 100 m,the cut-off efficiency of the zoom system is improved by 10% compared to that of the fixed-focus system.However,due to the limitation of heat dissipation and spot irradiation uniformity,the operating temperature of the receiving array of the zoom system is higher,and the series resistor consumes more power,resulting in the decrease of the photoelectric conversion efficiency of the array,and the overall efficiency in the short distance is inferior to that of the fixed focus system.3.Based on the irradiation model and analytical framework of the spot energy distribution of the receiving array,the influence of the UAV position attitude and error on the energy transfer characteristics is explored in depth.The results show that the tracking elevation angle has a large impact on the Gaussian filling efficiency of the system,which leads to large fluctuations in the overall energy transfer efficiency,and that the system can no longer meet the power consumption requirements needed for UAV hovering when the tracking elevation angle is less than 37°.The tracking azimuth and body yaw angle have a small effect on the total energy transfer efficiency(<1%),and the total energy transfer efficiency achieves a maximum when the body yaw angle is equal to the tracking azimuth.The inclusion of bypass diodes in the array can mitigate the electrical mismatch caused by errors,but the P-V curves of the array will show multiple peaks.The results of this study are useful for the design and optimization of laser wireless energy transfer systems based on fiber-coupled lasers,and for real-time predictive analysis of the dynamic performance of the energy transfer systems.In the actual operation stage,the position attitude of the multi-rotor UAV can be adjusted in time using the laws summarized in this paper to achieve the optimal energy transfer effect. |
