This study presents a new drone, called S-CLOUD, developed for safe and long flight time. It provides 3-axial (x, y, and z)translational motion and stable hovering for more than an hour after takeoff. S-CLOUD consists of two parts; soft blimp part and driving one. The soft blimp is a center-pierced torus-shaped part filled with Helium gas. Thus, it is safe to fly near people because it is light and soft, and all its rotating parts are at the center of the vehicle, which does not get damaged on collision. The driving part is plugged into the center of the soft blimp and includes the flow control mechanism, which consists of co-axial rotors and 2-axis crossed flaps. It controls the altitude, attitude, and translational movements of the vehicle. Its dynamic and reaction features against disturbances are derived using Newton-Euler formulation, and the simulation results are discussed. Finally, a prototype of S-CLOUD is fabricated and its feasibility is experimentally validated with practical applications.

The concept of utilizing the Coandia effect to produce stable flight in saucer type Aerial Vehicles (AV) was first conceived in 1935 by Henri Marie Coanda. Coanda's proposed AV design remained a relatively unexplored curiosity for decades until the recent surge in popularity of small Unmanned Aerial Vehicles (UAV) revitalized interest in the topic. Coandä effect UAV offer some distinct advantages over standard multirotors due to their robust frame design, which offers a unique mix of crash resistance, flight safety, and flight performance making them ideal for Human-Robot Interaction (HRI) applications. While much work has been performed in the area of characterization for Coanda surfaces and improved mechanical design of saucer type UAV, little work has been found in the literature discussing stability and attitude control of the platform. This work seeks to contribute to the study of these drones by introducing an approximate servo mapping for desired control effort of a particular prototype, and an experimental control law implemented within the framework of a modified commercially available flight stack.