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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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System for Multi-axial Mechanical Stabilization of Digital Camera 181<br />

Fig. 3. Schema of the system with open-loop control<br />

A l<strong>in</strong>ear function (1) determ<strong>in</strong>es the value to be set on the servo <strong>in</strong> order to turn<br />

the next member of the manipulator by a specified angle. Such unit ga<strong>in</strong> allows to<br />

transform the Euler angles read from IMU to number of pulses at the output of<br />

servomechanisms. The function has the follow<strong>in</strong>g form:<br />

190 512 (1)<br />

Fig. 4. Schema of closed-loop system with PID controller<br />

The servomechanisms can take <strong>in</strong>put values <strong>in</strong> the range start<strong>in</strong>g from 0 to 1023.<br />

The range represents values from -135º to +135º. Assum<strong>in</strong>g achievement of the<br />

immediate set po<strong>in</strong>t by the servos the track consists of a l<strong>in</strong>ear function and a separate<br />

servo ga<strong>in</strong>. Under such assumption the control system is capable of work<strong>in</strong>g.<br />

The <strong>in</strong>verse k<strong>in</strong>ematics is responsible for the determ<strong>in</strong>ation of the angles that<br />

need to be used as set po<strong>in</strong>ts for servos <strong>in</strong> order to change the orientation of<br />

the camera manipulator by a designated value. Orientation of the camera is a

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