Towards reconfigurable and flexible multirotors: A literature survey and discussion on potential challenges

Reconfigurable multirotors (RMs) with flexible frames and integrated mechanical compliance are increasingly explored to develop multifunctional aerial robots with high power-to-weight ratios. In this paper, we review the state-of-the-art research on RMs and classify them into three broad categories as tiltrotors, multimodal and foldable RMs. The RMs with the ability to arbitrarily orient their thrust by employing tilting rotors are classified as tiltrotors, the multirotors with multi modal locomotion capabilities by transforming the chassis into land/water propulsion systems are classified as multimodal RMs, and those which can alter the size of the chassis are labelled as foldable RMs. Existing platforms are analyzed from three different perspectives—mechanical design, challenges of low-level control and high level motion planning techniques. Finally, we identify the critical parameters for design optimization, and discuss the issues associated with developing a common control and motion planning algorithm that can leverage any RM’s features to demonstrate successful autonomous missions.