Design and Flight Control of a Novel Tilt-Rotor Octocopter Using Passive Hinges

This letter presents a novel tilt-rotor octocopter that can generate tiltable thrust without the need for servo-driven mechanisms. The octocopter's eight rotors are divided into pairs and each pair is mounted on an arm, which is connected to the airframe through passive hinges. Each pair is also equipped with a sub-controller that uses the differential thrust of the rotor pair to control the arm's tilting angle. Then, these sub-controllers work together with the main controller installed on the frame body to regulate the attitude and position of the octocopter. This octocopter can be controlled via a remote controller in a manner similar to a classic quadrotor, operating in stabilized or position mode both indoors and outdoors, also capable of executing flight missions following predefined trajectories. Considering that the communication delays between the main controller and sub-controllers would degrade the control performance due to the delayed response of the vectored thrust. We also propose a decentralized control allocation strategy that directly assigns parts of control loops to the sub-controllers so that the communication delays can be bypassed. Finally, we demonstrate the advantages of the new octocopter with the proposed method through simulations and real flight experiments.