  Localization is a fundamental function in cooperative control of micro
unmanned aerial vehicles (UAVs), but is easily affected by flip ambiguities
because of measurement errors and flying motions. This study proposes a
localization method that can avoid the occurrence of flip ambiguities in
bounded distance measurement errors and constrained flying motions; to
demonstrate its efficacy, the method is implemented on bilateration and
trilateration. For bilateration, an improved bi-boundary model based on the
unit disk graph model is created to compensate for the shortage of distance
constraints, and two boundaries are estimated as the communication range
constraint. The characteristic of the intersections of the communication range
and distance constraints is studied to present a unique localization criterion
which can avoid the occurrence of flip ambiguities. Similarly, for
trilateration, another unique localization criterion for avoiding flip
ambiguities is proposed according to the characteristic of the intersections of
three distance constraints. The theoretical proof shows that these proposed
criteria are correct. A localization algorithm is constructed based on these
two criteria. The algorithm is validated using simulations for different
scenarios and parameters, and the proposed method is shown to provide excellent
localization performance in terms of average estimated error. Our code can be
found at: https://github.com/QingbeiGuo/AFALA.git.
