Snake Aerial Manipulators: A Review <s> D. CURRENT KNOWN PROJECTS <s> In this letter, we introduce a novel transformable aerial robot called DRAGON, which is a dual-rotor-embedded multilink robot with the ability of multi-degree-of-freedom (DoF) aerial transformation. The new aerial robot can control the full pose in $\mathsf {SE}(3)$ regarding the center of gravity (CoG) of multilinks and can render the multi-DoF aerial transformation, which is accomplished by the original two-DoF force vectoring mechanism on each link called the dual-rotor gimbal module. The dynamics is derived on the basis of the special definition of CoG orientation, followed by a control method decoupled into thrust force control and rotor gimbal control. In the thrust force control, the minimum force norm is considered to avoid force saturation, and the rotor gimbal control method is developed to enhance both translational and rotational stabilities during hovering and large-scale aerial transformation. The prototype composed of four links is constructed, and associated preliminary experiments are performed. The feasibility of the novel mechanical design and the proposed control method for the aerial transformation is demonstrated. <s> BIB001 </s> Snake Aerial Manipulators: A Review <s> D. CURRENT KNOWN PROJECTS <s> We propose a novel aerial manipulation platform, an omnidirectional aerial robot, that is capable of omnidirectional wrench generation with opportunistically distributed/aligned Sectional rotors. To circumvent the tight thrust margin and weight budget of currently available rotor and battery technologies, we propose a novel design optimization framework, which maximizes the minimum-guaranteed control force/torque for any attitude while incorporating such important and useful aspects as interrotor aerointerference, anisotropic task requirement, gravity compensation, etc. We also provide a closed-form solution of infinity-norm optimal control allocation to avoid rotor saturation with the tight thrust margin. Further, we elaborate the notion of electronic speed controller induced singularity and devise a novel selective mapping algorithm to substantially subdue its destabilizing effect. Experiments are performed to validate the theory, which demonstrate such capabilities not possible with typical aerial manipulation systems, namely, separate translation and attitude control on SE(3), hybrid pose/wrench control with downward force of 60 N much larger than its own weight (2.6 kg), and peg-in-hole teleoperation with a radial tolerance of 0.5 mm. <s> BIB002
DRAGON. 12 This configuration BIB001 , is characterized by using propellers as hovering elements and servomotors as elements of three-dimensional manipulation. ODAR FAM-ILY Fig. 12 In this case, multirotors are used at the same time as elements of hovering, dexterity and three-dimensional manipulation, through the interaction with three-dimensional joints, for example spherical or ball-joints BIB002 ,  . EHE-CATL Fig. 12 In this case, the multirotors or propellers are used as elements of hovering, dexterity and manipulation with selective assistance of servomotors and interaction with variable three-dimensional joints (as clutches) or restricted three-dimensional joints (for example, spherical joints with a slot for yaw restriction)  .