  In this paper, we introduce a new quadcopter fail-safe flight solution that
can perform the same four controllable degrees-of-freedom flight as a regular
multirotor even when a single thruster fails. The new solution employs a novel
multirotor platform known as the T3-Multirotor and utilizes a distinctive
strategy of actively controlling the center of gravity position to restore the
nominal flight performance. A dedicated control structure is introduced, along
with a detailed analysis of the dynamic characteristics of the platform that
change during emergency flights. Experimental results are provided to validate
the feasibility of the proposed fail-safe flight strategy.
