## 2 Aerial Robotics  
This Special Issue collects 16 papers in total in the field of aerial robotics, which are divided into 15 research papers and 1 review. The platforms used in these researches are based on a rotary-wing unmanned aerial vehicle (UAV, 9 papers, 3 of them are on aerial manipulation), on a fixed-wing UAV (6 papers), or on a flapping-wing UAV (1 paper). A consistent set of the papers contained within this Special Issue focuses on the motion planning and control of rotary-wing UAVs (9 papers), either with or without an end-effector to interact with the environment. In particular, three papers home in on the emerging field of aerial manipulation (UAV plus robot manipulator), one paper is a review on the propulsion system design methods of both rotary-wing and fixed-wing UAVs, and all the other works are written on conventional rotary-wing UAVs. In the field of aerial manipulation, [PERSON] et al. [1] propose two novel inverse kinematic control methods, used to track a trajectory and pick a load with an aerial manipulator. Among the main challenges in aerial manipulation, one which has been addressed with this work, is related to the movement of the UAV base caused by manipulator disturbance torques and forces. This is a motion that jeopardizes the precision of the robot manipulator. The first proposed method to be presented is adapted from the generalized Jacobian formulation used in space robotics and includes the change in system momentum resulting from gravity and UAV control forces in the inverse kinematic control equation. To drastically reduce the undesired UAV motion by exploiting the kinematic redundancy of the manipulator, the extended generalized Jacobian is then introduced by adding an additional task constraint that minimizes the reaction torques on the UAV. The proposed methods are suitable for real-time implementation and are validated through dynamic simulations. [PERSON] et al. [2] propose a motion control scheme for a new concept of omnidirectional UAV for transportation and manipulation tasks. The proposed quadrotor platform can provide multi-directional thrust thanks to an actuated gimbal mechanism in charge of modifying the orientation of the frame on which the four rotors are mounted. The mechanical design outlined above, unlike omnidirectional UAVs with tilted propellers, avoids internal forces and energy dissipation due to non-parallel propellers axes. The proposed motion controller is based on a hierarchical two-loop scheme. The external loop computes the force to be applied to the vehicle and the reference values for the additional joints, while the inner loop computes the joint torques and the moment to be applied to the multirotor. Simulation case studies prove the capability of the omnidirectional UAV platform to track a 6-Degrees-of-Freedom (DOFs) trajectory, both in free motion conditions and during a task involving grasping and transportation of an unknown object. Aerial continuum manipulation systems (ACMSs) have been recently introduced via the integration of a continuum robot (CR) into an aerial vehicle to address several issues of conventional aerial manipulation systems. This includes concerns such as safety, dexterity, flexibility and compatibility with objects. The nonlinearity and complexity of CRs modeling make it difficult to design a coupled ACMS dynamic model suitable for practical applications. In this context, [PERSON] et al. [3] present a coupled dynamic model for ACMSs to deal with CR and the aerial vehicle as a unified system. This is based on the Euler-Lagrange formulation. The simulation results of free flight motion scenarios are reported to verify the effectiveness of the proposed modeling and control techniques. In this Special Issue, several research works concerning conventional rotary-wing UAVs are presented, mainly on dynamics, control, sensor fusion for localization, and motion planning. 3D motion planning algorithms play a vital role in attaining various levels of autonomy for UAVs.