Modularized multibody multirotor for independent attitude and position control*

Abstract

This paper presents the novel design and development of a multibody multirotor (MBMR) capable of controlling orientation independent of the position by tilting the passive thrust vector without any additional actuators. Conventional multirotors have a limitation in controlling the orientation independently of the position control. In particular, it is important to control the orientation independently since it affects flight efficiency and mission. Thus, various tiltrotors have been developed to control the orientation independently but require additional servo motors. The MBMR consists of a main fuselage and thrust modules without a servo motor. Each of the thrust modules can be utilized by a conventional quadrotor with four rotors connected to the fuselage by passive rotational joints. Two thrust modules, the minimum to form the MBMR, are implemented to demonstrate performance. Toward usability of the MBMR, a hierarchical control system is developed to compute relative thrust and moment vectors with respect to the fuselage. Thrust heading alignment control (THAC) is proposed to overcome a lack of roll angle control. The control system allows the heading angle of the MBMR to track the direction of thrust force so that it can maintain the near-zero tilt angle of the fuselage while generating acceleration. Experimental validation is implemented demonstrating the performance of the MBMR with independent orientation control. It is successfully achieved to regulate the fuselage's pitch angle at 80 degrees angle and track the circular trajectory within the fuselage's tilt angle under 2.6 degrees angle.