Dynamics and Control of UAVs

In recent years, the study of unmanned aerial vehicles (UAVs) has attracted attention because of their diverse applications. Thus, these systems have become increasingly popular and a fundamental component in many everyday and industrial applications, since their use is significantly increasing to a wide range of useful tasks, such as recognition in open fields, communication, environmental monitoring, precision agriculture, transportation of packages, rescue operations, policing, professional photography, mining operations, remote inspection, etc. These applications rely on modeling, control systems, and design of control strategies for UAVs. However, the unmanned aerial vehicle is a complex system to model and design control systems, since these systems have characteristics such as under-actuation, nonlinearity, and strong coupling. Consequently, there has also been a huge growth in the number of control algorithms to support their many applications. In fact, autonomous navigation has become a challenge that requires a good knowledge of vehicle dynamics and aerodynamic effects.

Therefore, despite the significant advances made in recent years, there is a growing interest in developing new advanced control and modeling techniques or adapting existing algorithms in order to ensure that UAVs can navigate as required to carry out specific applications in a robust, reliable, and safe manner.

We are excited to introduce this Special Issue, which presents new developments in modeling and advanced control techniques for UAVs and their applications. It comprises five high-quality research articles. They are summarized in the following paragraphs.

Article [1] presents the design and development of a robust control strategy for a small fixed-wing unmanned aerial vehicle with non-minimum phase zero characteristics in their mathematical model through internal model control, which does not require complex optimization. This approach is highly relevant to practical applications in non-minimum phase-type UAV control problems, as it takes advantage of the model’s non-minimum phase zero characteristics to inform the design process and can also enable fine loop-shaping with higher-order model representations.

Study [2] designs a discontinuous extended state observer-based differential flatness to the trajectory-tracking problem of the spherical inverted pendulum attached on a quadrotor vehicle. The nonlinear mathematical model of the system is derived via the Euler–Lagrange formulation. In this work, considering the differential flatness property of the system, a set of new outputs are defined, which allow the design of an active disturbance rejection control.

Paper [3] shows a trajectory tracking control for a quadrotor vehicle based on a fractional-order S-plane model. Specifically, a control law based on the quaternion error is developed through a combination of fractional-order PID control with S-plane control. Experimental results show that the trajectory tracking control has a better performance against wind disturbances and tracking accuracy compared to a fractional-order PID.

Ref. [4] proposes an algorithm to carry out search and rescue operations tasks with unmanned aerial vehicles. Particularly, an integrated YOLOv5 model and HWF framework have been proposed, in order to reduce the search time and increase the accuracy of search and rescue operations. The YOLOv5 model is used to recognize the search target in real time, and the HWF path-planning algorithm is used to send a UAV to capture images of the search target at different altitudes.

Article [5] develops a consensus tracking control algorithm for multiple unmanned aerial vehicles under the presence of unknown time-varying delays. In this work, the stabilization of multiple quadrotors where the control input is affected by unknown time-varying delays is achieved. For each UAV agent, an unknown input observer is employed to isolate the unknown time-varying delays in the state estimation process. The designed consensus control between the leader and followers is guaranteed by the stability of the proposed scheme, which is proven using Lyapunov’s theory for leader and follower agents.

In summary, this Special Issue documents important advances and developments in the field dynamics and control for UAVs and bring new prospects for further development in multiple applications of these systems. Thus, the papers presented in this Special Issue contribute strongly in the field of modeling and design of control strategies for UAVs, as well as in their applications.

The Guest Editors of this Special Issue, titled “Dynamics and Control of UAVs”, would like to thank the authors for the submission of valuable and high-quality research, the reviewers for their efforts and time spent to improve these articles, and the editorial staff who contributed to making this Special Issue possible.