![](bg7.png)
and a limited control of attitude can be achieved by
both control laws. In addition, a reduction of the au-
topilot’s gain margin (stability) is noted and the total
damping and the time response are affected (see the
settling time in the Fig. 6(a) and the Fig. 6(b)). For
this simulation the autopilot’s design parameters and
the control law gain K were: ω
CR
= 10 rad/s, ζ = 0.7,
τ = 0.2 s, and K = [8,2,8]. Moreover, the initial stage
of the guidance is the worse flight condition that the
autopilot has to deal with. For high altitude h and low
Mach number M, the autopilot requires the higher val-
ues of α and δ. This initial condition affects more the
control law based on y = e
c,h
than the control based on
y = e
t,h
. One way to improve the initial response of
the autopilot is to rise the value of the vehicle’s initial
velocity, but it will always be constrained.
6 CONCLUSIONS
An epipole-based control law for guiding an au-
tonomous UAV has been presented. Only epipolar
measurements from two views were used to drive the
vehicle to a static camera position. Stabilization of
a nonlinear engagement rule by an input-output non-
linear control strategy was developed and two differ-
ent alternatives for guidance, one based on the cur-
rent epipolar coordinate, and the other based on the
target epipolar coordinate, were studied. A state feed-
back control law with integral action guaranteed that
the epipolar coordinates follow a reference equilib-
rium signal. A model of a non-propelled UAV, that
includes a classical three-loop autopilot, was used to
simulate the control strategies. The tracking of refer-
ence signals and stability analysis will be studied as
future developments.
ACKNOWLEDGEMENTS
This work was supported by Universidad de los An-
des / Industria Militar de Colombia (INDUMIL), Uni-
versidad de Zaragoza / Ministerio de Ciencia e Inno-
vaci´on / Uni´on Europea DPI2009-08126, and Univer-
sidad de Nari˜no.
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