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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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180 D. Bereska et al.<br />

3 Control Algorithms for Mechanical Stabilization<br />

In order to measure the quality of the mechanical stabilization, the camera was<br />

look<strong>in</strong>g at the black shape on white background, so it was possible to calculate the<br />

center of the shape’s mass at each frame. The lesser is the shift, the better is the<br />

stabilization. The axes of the whole system have been picked <strong>in</strong> the follow<strong>in</strong>g<br />

order: Z axis was turned upward (yaw angle of rotation), X axis was turned to the<br />

front (roll) and Y axis was turned to the left (pitch). Possible rotations of test<br />

bench (distraction) were allowed on axis X and Y (fig. 2).<br />

Fig. 2. A photograph of testbed used. Red l<strong>in</strong>es <strong>in</strong>dicates coord<strong>in</strong>ate system axis directions.<br />

Servos are the elements which are able to rotate the element positioned on the<br />

axis of rotation by an angle which is proportional to the setpo<strong>in</strong>t. The value can be<br />

calculated by the control algorithms which utilizes the available sensory <strong>in</strong>formation<br />

like orientation from IMU) and setpo<strong>in</strong>ts. Control algorithm us<strong>in</strong>g those<br />

values may be capable of br<strong>in</strong>g<strong>in</strong>g the mechanical system to the state when the<br />

camera’s l<strong>in</strong>e-of-sight is <strong>in</strong> a given direction. Setpo<strong>in</strong>ts for servos may be designate<br />

by the control algorithm based on the values selected and sensory <strong>in</strong>formation<br />

which are not subject of stabiliz<strong>in</strong>g. For <strong>in</strong>stance orientation of the testbed which<br />

is beyond our manipulation control. Such control system is a control system called<br />

open-loop control (fig. 3).

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