  This paper introduces for the first time the design, modelling, and control
of a novel morphing multi-rotor Unmanned Aerial Vehicle (UAV) that we call the
OmniMorph. The morphing ability allows the selection of the configuration that
optimizes energy consumption while ensuring the needed maneuverability for the
required task. The most energy-efficient uni-directional thrust (UDT)
configuration can be used, e.g., during standard point-to-point displacements.
Fully-actuated (FA) and omnidirectional (OD) configurations can be instead used
for full pose tracking, such as, e.g., constant attitude horizontal motions and
full rotations on the spot, and for full wrench 6D interaction control and 6D
disturbance rejection. Morphing is obtained using a single servomotor, allowing
possible minimization of weight, costs, and maintenance complexity. The
actuation properties are studied, and an optimal controller that compromises
between performance and control effort is proposed and validated in realistic
simulations. Preliminary tests on the prototype are presented to assess the
propellers' mutual aerodynamic interference.
