The use of Unmanned Aerial Vehicles (UAVs) has become popular in recent years, especially for their potential in various practical applications, but for their use to become a reality this context, it is necessary to study about it. One of the main problems involving UAVs, regardless of the application to which it will be used, is path planning, which is crucial to ensure safety, economy, and effectiveness. In this study we present a literature review on the optimization problem path planning and the methods used to solve it. To this end, we seek to explore the existing papers in literature on this topic, identifying mathematical models, analyzing characteristics of the objective function, types of obstacles, number of UAVs considered, the nature of the solution adopted and deployments and integration in the Internet of Drones (IoD). A comparative analysis of the works analyzed was presented in the form of tables for each path planning technique considered. In addition, some advantages and safety of the methods were also listed. We furthermore present a set of open research challenges, high-level insights, and future research directions related to the UAV path planning problem in the context of IoD. This study contributes deeply with the advancement of state of art regarding the path planning strategies on the Internet of Drones since we provide a thorough analysis of characteristics of the mathematical models used in the UAV path planning problem reviewing papers published in relevant journals and conferences in the last 4 years (2018 to 2022), highlighting the advantages and disadvantages of each method as well as the possibilities of implementation and integration with IoD.INDEX TERMS Internet of drones, Optimization, Path Planning techniques, Unmanned Aerial Vehicles (UAV), IoD architecture.
I. INTRODUCTIOND RONES, as known as Unmanned Aerial Vehicles (UAVs), is the most usual way to refer to an aircraft that does not carry a crew. Several terms are used to refer to "drones". Besides UAV, the most common are: unmanned aircraft systems (UAS), remotely piloted vehicles (RPVs), remotely piloted aircraft (RPAs). In recent years, we have observed the increasing popularity and use of UAVs, in different handy applications, such as delivery, transportation, agriculture, monitoring, medical assistance, image capturing, among others [1]-[9]. In the past, the UAVs were mainly used in military applications where one or more drones were used for weather monitoring, soldier recognition, search and rescue. These applications remain and as listed above, several others have emerged, bringing new challenges and the need for more research about them.Currently, there are several studies related to delivery applications with UAVs. Large and well-known companies such as Amazon [10], Google, iFood [11], are investing in research and possibilities to make their deliveries via drones. However, for such implementation to be possible and feasible in the future, it is necessary to organize and coordinate the airspace and drones, since se...
