In this paper, 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 SE(3) regarding the center of gravity (CoG) of multilinks and can render the multi-DoF aerial transformation, which is accomplished by the original 2DoF force vectoring mechanism called 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. The minimum force norm is considered in the thrust force control 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 from 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.

Various state-of-the-art works have achieved aerial manipulation and grasping by attaching additional manipulator to aerial robots. However, such a coupled platform has limitations with respect to the interaction force and mobility. In this paper, we present the successful implementation of aerial manipulation and grasping by a novel articulated aerial robot called DRAGON, in which a vectorable rotor unit is embedded in each link. The key to performing stable manipulation and grasping in the air is the usage of rotor vectoring apparatus having two degrees-of-freedom. First, a comprehensive flight control methodology for aerial transformation using the vectorable thrust force is developed with the consideration of the dynamics of vectoring actuators. This proposed control method can suppress the oscillation due to the dynamics of vectoring actuators and also allow the integration with external and internal wrenches for object manipulation and grasping. Second, an online thrust-level planning method for bimanual object grasping using the two ends of this articulated model is presented. The proposed grasping style is unique in that the vectorable thrust force is used as the internal wrench instead of the joint torque. Finally, we show the experimental results of evaluation on the proposed control and planning methods for object manipulation and grasping.

In this study, we investigated a novel type of the multirotor aerial vehicle with two-dimensional multilinks to demonstrate stable aerial transformation for high mobility in three-dimensional environments. Our goal was to tackle the challenge of traversing narrow spaces or gaps, which is one of the difficulties for existing structure of multirotors, especially in the cluttered indoor environment of disaster sites. The research involved three steps. First, we developed the modeling of the link modules that compose a multirotor with two-dimensional multilinks and conducted a quadrotor prototype. Second, we derived a stable flight control method for aerial transformation on the basis of linear-quadratic-integral optimal control. Third, we investigated the motion planning for the aerial transformation using a state validation method and path optimization in the joint space to maintain the stability during transformation. Successful aerial transformation and the ability of the prototype to negotiate narrow gaps were demonstrated, confirming the feasibility and utility of our proposed transformable multirotor for aerial maneuvering in complex three-dimensional environments.

Multimodal locomotion capability is an emerging topic in robotics field, and various novel mobile robots have been developed to enable the maneuvering in both terrestrial and aerial domains. Among these hybrid robots, several state-of-the-art bipedal robots enable the complex walking motion which is interlaced with flying. These robots are also desired to have the manipulation ability; however, it is difficult for the current forms to keep stability with the joint motion in midair due to the centralized rotor arrangement. Therefore, in this work, we develop a novel air-ground quadruped robot called SPIDAR which is assisted by spherically vectorable rotors distributed in each link to enable both walking motion and transformable flight. First, we present a unique mechanical design for quadruped robot that enables terrestrial and aerial locomotion. We then reveal the modeling method for this hybrid robot platform, and further develop an integrated control strategy for both walking and flying with joint motion. Finally, we demonstrate the feasibility of the proposed hybrid quadruped robot by performing a seamless motion that involves static walking and subsequent flight. To the best of our knowledge, this work is the first to achieve a quadruped robot with multimodal locomotion capability.

In this paper, we present the achievement of aerial grasping by shape adaptive transformation to the object shape, using a novel transformable aerial robot called HALO: Horizontal Plane Transformable Aerial Robot with Closed-loop Multilinks Structure. Aerial manipulation is an active research area and using multiple aerial robots is an effective solution for the large size object. However the cooperation is considered that there are some difficulties such as the synchronized flight control and collision with each other. Then, we focus on the transformable aerial robot with two-dimensional multilinks proposed in our previous works, which can transform to the suitable form for the target object and grasp it. However the transformable aerial robot with the serial-link structure could not achieve stable flight in terms of horizontal position and yaw control due to the low rigidity and large inertia in the case of more than 4 links. Thus, first we construct a novel type of multilinks with closed-loop structure to avoid the deformation and a new link module with a tilted propeller for fully-actuated control. Second, we describe transformation method with closed-loop multilinks. Third, we present the optimization planning method for the multilinks form to be adaptive to the two-dimensional shape of the target object. Finally, we present experimental results to demonstrate the feasibility of closed-loop aerial transformation and aerial grasping for the large size object.

Aerial manipulation is a growing field of research, and multirotors with attached arm manipulator have shown practical utility in contact-based inspection. However, theses coupled platforms limit the pose reachability of the end-effector, which then motivates the development of omni-directional designs for aerial robots. Although the full pose tracking can be achieved by these omni-directional models, the large amount of internal thrust force constrains wrench exertion for forceful manipulation such as valve operation. Thus, in this letter, we harness an articulated aerial robot equipped with thrust vectoring apparatus, which enables not only the omni-directional pose of end-effector, but also the sufficient 6 $^{\circ }$ -of-freedom wrench for valve operation. First, we develop a joint configuration strategy for this articulated model to ensure sufficient torque to turn valves. Then, we present control and motion planning methods for exerting appropriate wrench while following a manipulation trajectory. Comprehensive experiments that involves various valve directions are evaluated in this work, demonstrating the feasibility of our methods to exert forceful wrench. To the best of our knowledge, this letter is the first to achieve the operation of real industrial valve with real torque scale.