A Comprehensive Review of Recent Research Trends on UAVs

The rapid growth of the UAV field, fueled by scientific and industrial interest and substantial investments, necessitates a comprehensive guide for newcomers. This interdisciplinary field connects aerospace engineering, computer science, robotics, and remote sensing. Existing review papers address various aspects of UAV development, but a synthesis of recent trends and future directions is needed. This paper aims to fill this gap by providing a structured overview of UAV classifications, research trends (analyzed through Scopus data from 2020-2023), open development axes, aircraft control techniques, hardware/software architectures, applications, and key issues. The paper also explores the role of open-source projects in advancing UAV technology. The surge in AI's role in UAVs – enhancing navigation, object detection, and mission planning – further underscores the need for this comprehensive review to guide future research and development.

The paper draws upon numerous existing literature reviews and surveys related to UAVs. These reviews cover various aspects, including open-source hardware and software projects [22]-[24], frame designing and optimization [25], [26], conventional and modern control systems [27]-[31], 5G network integration, AI integration [32], recognition and detection algorithms, and path planning strategies [33]. Existing research highlights the interdisciplinary nature of UAV research and the challenges and opportunities in this rapidly evolving field [34], [35]. The review also incorporates studies on specific UAV applications, such as environmental monitoring [37]-[42], conservation [41], [43], and animal studies [19], [37].

The authors used the Scopus database to analyze recent research trends in UAVs. The search, conducted on March 14, 2023, used keywords such as "drone," "UAV," "unmanned aerial vehicle," and "unmanned aerial systems" to retrieve publications from 2020 to 2023. A total of 47,635 references were obtained. The data was analyzed to identify prominent research directions, with the number of publications used as an indicator of significance. Growth trajectories were plotted to understand the growth rate and acceleration of different research areas. The analysis also examined the interconnections between various research directions to identify areas with significant overlap and potential for integrated solutions. In addition to the quantitative analysis using Scopus, the paper conducts a qualitative review of the literature to discuss various aspects of UAV technology, such as classifications, control algorithms, hardware/software architectures, and open-source projects.

The Scopus analysis revealed that "Antennas" received the most attention (22,150 documents), with strong links to aircraft detection, remote sensing, AI, IoT, and aircraft control. "AI" was the second most referenced research direction (5,789 documents), followed by "Aircraft Detection" (5,604 documents). Other significant areas included remote sensing, IoT, and aircraft control. Figure 2 visually represents the interconnections between these research directions. Table I provides a numerical analysis of these interrelationships. The analysis of growth trajectories (Figure 3 and Table III) identified "Remote Sensing" as a rapidly expanding area, despite having fewer overall publications compared to "Antennas." The paper further details specific research directions within these broader areas: * **Communication and Antennas:** Research focuses on lightweight, compact, and durable antennas, employing ML and DL for design optimization and exploring miniaturization and novel materials. * **IoT Integration:** The integration of UAVs with IoT devices for data collection and analysis in diverse fields is highlighted, along with challenges in security and privacy. * **Aircraft Detection:** The development of advanced systems for real-time aircraft detection and collision avoidance, using sensors and ML algorithms, is discussed. * **Control and Autonomous Flight:** This section explores autonomous flight capabilities, challenges in obstacle avoidance and real-time navigation, and ensuring safety and reliability. * **Perception and Sensing:** The integration of various sensors (cameras, LiDAR, radar), computer vision algorithms, and AI for environmental understanding and decision-making is detailed. * **Energy-Efficient Flight:** Strategies for extending flight time through aerodynamic optimization, lightweight materials, and alternative energy sources are reviewed. * **Human-UAV Interaction:** This section examines human-UAV interaction technologies (VR/AR, gestures, natural language), challenges in real-time response, and safety considerations. * **Swarm Behavior:** The study explores algorithms and control systems for cooperative control of UAV swarms, addressing challenges in communication, control architectures, path planning, and localization. * **AI Integration:** The significant impact of AI in UAV object detection, path planning, autonomous navigation, swarm intelligence, image/video analysis, and cybersecurity is discussed, including applications of ChatGPT for intuitive user interfaces.

The findings address the research question by providing a structured overview of the UAV research landscape. The significance of the results lies in identifying key trends, highlighting the interconnectedness of different research areas, and suggesting promising future research directions. The Scopus database analysis provides a quantitative measure of research activity in different areas, while the qualitative review offers deeper insights into specific technologies and challenges. The paper’s significance lies in its comprehensive approach, integrating both quantitative and qualitative data to paint a complete picture of the current state and future prospects of UAV research. The identified limitations of existing technologies, such as battery life and communication range, highlight areas requiring further investigation. The paper's suggestions for future research in areas like AI integration, swarm technologies, and enhanced communication protocols are highly relevant to the field and can guide future research efforts.

This paper offers a comprehensive overview of UAV research, identifying key trends and interconnections between research directions using Scopus data (2020-2023). It explores potential open development axes, including AI integration, environmental monitoring, miniaturization, swarming, and transformability. The paper also reviews various aircraft control techniques and emphasizes the importance of selecting appropriate control algorithms. Key challenges, such as communication, power, and safety, are discussed, along with an overview of open-source software and hardware projects. Future research should focus on addressing these challenges and further integrating AI, improving communication protocols, and developing robust safety mechanisms.

The Scopus database search, while comprehensive, may not capture all relevant publications, potentially leading to a slightly biased representation of research trends. The analysis focuses on publications from 2020-2023 and may not fully reflect longer-term trends. Further, while the paper offers a wide-ranging overview, it cannot delve into every specific aspect of the multifaceted UAV field with equal depth. The reliance on self-reported keywords in the Scopus database may not accurately reflect the actual focus of all publications.