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[Studies in Computational Intelligence 481] Artur Babiarz, Robert Bieda, Karol Jędrasiak, Aleksander Nawrat (auth.), Aleksander Nawrat, Zygmunt Kuś (eds.) - Vision Based Systemsfor UAV Applications (2013, Sprin

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226<br />

K. Daniec et al.<br />

height. The next step is to<br />

achieve an <strong>in</strong>itial height that is equal to 1 <br />

5 of the desti-<br />

nation altitude. When this<br />

happens, there are activated height and head<strong>in</strong>g control-<br />

and despite all the efforts,<br />

it is not perfect. The land<strong>in</strong>g process is divided <strong>in</strong>to two<br />

parts, the first concerns the approach to land and set the plane on of the glide path<br />

(fig. 6), while the second<br />

concerns the land<strong>in</strong>g curve. To determ<strong>in</strong>e the coordi-<br />

nates of the approach for land<strong>in</strong>g, important <strong>in</strong>formation is: where (relative to<br />

lers, which effects the stabilization of the take-off dest<strong>in</strong>ation altitude.<br />

The autonomous land<strong>in</strong>g algorithm proved to be quite difficult to implement,<br />

airport) is a plane.<br />

Fig. 6. Approach for land<strong>in</strong>g<br />

Depend<strong>in</strong>g on the location aircraft, the algorithm determ<strong>in</strong>es from 6 (purple and<br />

green colors) to 9 (blue and red colors) coord<strong>in</strong>ates. The first coord<strong>in</strong>ate is not<br />

always at the beg<strong>in</strong>n<strong>in</strong>g of the first arrow <strong>in</strong> the fig. 6. It can be located for exam-<br />

ple <strong>in</strong> the middle of this arrow. The method for determ<strong>in</strong><strong>in</strong>g whether a coord<strong>in</strong>ate<br />

is reached, is to compare<br />

the absolute values of all three ENU coord<strong>in</strong>ates, with<br />

predef<strong>in</strong>ed precision value<br />

(4).<br />

<br />

|| || || , (4)<br />

where: confirm the position is reached, , , ENU coord<strong>in</strong>ate compo-<br />

nents, redef<strong>in</strong>ed precision value <strong>in</strong> meters.<br />

When the airplane reaches the beg<strong>in</strong>n<strong>in</strong>g of the glide path, algorithm starts to<br />

determ<strong>in</strong>e the land<strong>in</strong>g curve. The function of the curve is described by the formula<br />

(5), but it is scaled to the<br />

left and right side of the -axis. Each part conta<strong>in</strong>s 10<br />

coord<strong>in</strong>ates, and the whole left side concerns only for the airport. Navigation dur-<br />

<strong>in</strong>g land<strong>in</strong>g is fairly complicated, and therefore, when determ<strong>in</strong><strong>in</strong>g achieved posi-<br />

tion algorithm checks only the height of the airplane. Us<strong>in</strong>g the follow<strong>in</strong>g ENU<br />

coord<strong>in</strong>ates there is determ<strong>in</strong>ed the pitch angle from the formula (6), and the<br />

orientation of the plane is set towards the end of the runway. When the height<br />

relative to the airport will be sufficiently low (i.e. the plane will be about 5<br />

above the runway), the setpo<strong>in</strong>t speed is reduced to the land<strong>in</strong>g speed, and f<strong>in</strong>ally<br />

when airplane reaches this speed the eng<strong>in</strong>e is turned off.

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