Motion-planning algorithms play a vital role in attaining various levels of autonomy for any ground or flying agent. Three-dimensional (3D) motion-planning is interesting, but rather complex, especially for flying agents such as autonomous unmanned aerial vehicles (UAVs), due to the increased dimensionality of space and consideration of dynamical constraints for a feasible trajectory. Usually, in 3D path search problems, it is hard to avoid extra expanded nodes due to increased dimensionality with various available search options. Therefore, this paper discusses and implements a modified heuristic-based A* formalism that uses a truncation mechanism in order to eradicate the mentioned problem. In this formalism, the complete motion planning is divided into shortest path search problem and smooth trajectory generation. The shortest path search problem is subdivided into an initial naïve guess of the path and the truncation of the extra nodes. To find a naïve shortest path, a conventional two-dimensional (2D) A* algorithm is augmented for 3D space with six-sided search. This approach led to the inclusion of extra expanded nodes and, therefore, it is not the shortest one. Hence, a truncation algorithm is developed to further process this path in order to truncate the extra expanded nodes and then to shorten the path length. This new approach significantly reduces the path length and renders only those nodes that are obstacle-free. The latter is ensured using a collision detection algorithm during the truncation process. Subsequently, the nodes of this shortened path are used to generate a dynamically feasible and optimal trajectory for the quadrotor UAV. Optimal trajectory generation requires that the plant dynamics must be differentially flat. Therefore, the corresponding proof is presented to ensure generation of the optimal trajectory. This optimal trajectory minimizes the control effort and ensures longer endurance. Moreover, quadrotor model and controllers are derived as preliminaries, which are subsequently used to track the desired trajectory generated by the trajectory planner. Finally, results of numerical simulations which ultimately validate the theoretical developments are presented.

Facial Emotion Recognition (FER) software is an important part of modern software applications. It is used for intelligent user interfaces, diagnostics in psychiatry or psychology, human-computer interaction, and even in surveillance. The recent advancements in the use of deep learning, and the advanced architectures based on them, including Convolutional Neural Networks (CNNs) and transformer models have made the development of FER software much efficient and scalable. This review paper contributes to the existing literature by providing a comprehensive synthesis of Facial Emotion Recognition (FER) systems from a software engineering perspective spanning the period from 2015 to the present. Unlike prior surveys, our analysis emphasizes the software engineering perspective, covering aspects such as software architectures, system integration, deployment on edge devices, and MLOps practices for continuous testing and monitoring. It specifically targets software construction, software architecture, software systems integration, training frameworks, datasets employment, and also deployment challenges. It explores common datasets like FER2013, RAF-DB and AffectNet and the prevailing model architectures, which include CNN, Long-Short-Term Memory (LSTM), hybrid and transformers. Importantly, over half of the surveyed studies continue to rely on demographically narrow datasets (e.g., FER2013, JAFFE, CK+), which limits generalizability and raises fairness concerns across ethnicity, age, and gender. This review contributes by providing a comprehensive and up-to-date synthesis of FER systems while providing directions to the development of fair, lightweight, and robust FER systems suitable for real-world deployment.