# Power Sources for Unmanned Aerial Vehicles: A State-of-the Art
## 2 Unmanned Aerial Vehicle (UAV)
### Battery-Based Supply Techniques
#### 2.2.3 Laser Beam Inflight Recharging
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\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Main Contribution** & **Advantages** & **Limitations** \\ \hline A dual-drum structure was implemented in the hardware platform to enable fast and efficient hot swapping. This design feature allows for the quick replacement of batteries, enhancing the efficiency of the swapping process. & A flight test was conducted to evaluate the performance of the system, taking into account communication constraints. During the test, the system was assessed under real-world conditions, considering limitations in communication capabilities. This provided valuable insights into the system’s performance and effectiveness in scenarios with communication constraints. & The study did not include tracking the health of the vehicle or monitoring its condition. Additionally, the experiments conducted had a maximum mission time of only 70 min. Therefore, the study did not focus on monitoring and assessing the overall health and performance of the vehicle throughout extended missions. \\ \hline A declarative model was proposed to optimize the routing of a multi-agent system consisting of UAVs and mobile battery swapping stations (MBS) for delivery missions. The model aimed to efficiently plan the routes and schedules of UAVs and MBS to ensure timely by the UAVs and maximizes the efficiency of the system. By optimizing these factors, the study aimed to enhance the performance and cost-effectiveness of the system. However, it should be noted that the feasibility and practility of implementing the proposed optimizations were not specifically tested or evaluated in the study. & The study presented computational results related to the optimization of the traveled distance and the number of UAVs in the context of the multi-agent system with mobile battery swapping stations. However, it did not include experimental validation or testing of the proposed techniques. The focus of the study was on computational modeling and analysis, providing insights into the potential benefits of the proposed optimizations. The specific details and mechanisms of the swapping technique were not discussed in the study, as it primarily concentrated on the computational aspects of routing and optimization. \\ \hline The study aimed to achieve precise UAV positioning after landing with minimal error. The researchers focused on developing techniques or algorithms that would ensure accurate positioning of the UAVs after the landing process. By minimizing the positioning error, they aimed to enhance the overall performance and efficiency of the system. However, it is important to note that the specific methods or approaches used to achieve precise UAV positioning after landing were not detailed in the information provided. & The study reported a relatively long swapping duration, indicating that the process of replacing batteries in the system took a considerable amount of time. However, it should be noted that the entire system, including all its components and functionalities, was not tested as a whole. This means that while certain aspects of the swapping process may have been examined or validated individually, the complete integration and performance of the system were not assessed through comprehensive testing. As a result, the overall efficiency and effectiveness of the swapping mechanism, as well as its potential limitations or drawbacks, remain uncertain and require further investigation or evaluation. \\ \hline \hline \end{tabular}
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Table 2: _Cont._safety by eliminating risks associated with take-off and landing. Laser transmitters can be strategically positioned on tall building rooftops to ensure an unobstructed laser beam path, or they can be installed on a mobile station, as depicted in Figure 5. This establishes a radiative link between the UAV and the nearest energy source, enabling fast power transfer. Companies like LaserMotive (Washington, DC, USA) have developed working prototypes capable of transferring hundreds of watts of power [54].