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Navigation Functionalities for an Autonomous UAV Helicopter

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66 CHAPTER 5. SENSOR FUSION FOR VISION BASED LANDING<br />

noisy. Early attempts have been made in applying a low-pass filter to this<br />

velocity to remove the noise but the increased delay made the tuning of the<br />

control system more difficult. The velocity data provided by the Kalm<strong>an</strong><br />

filter has low latency as c<strong>an</strong> be observed from the comparison with the GPS<br />

velocity. This is due to the fact that the Kalm<strong>an</strong> filter takes adv<strong>an</strong>tage of<br />

the high frequency <strong>an</strong>d low latency in<strong>for</strong>mation from the accelerometers.<br />

The use of low latency velocity in<strong>for</strong>mation allows <strong>for</strong> stable control during<br />

the l<strong>an</strong>ding approach.<br />

Figure 5.5: Comparison between velocity derived from raw vision position,<br />

sensor fusion <strong>an</strong>d GPS <strong>for</strong> the North component.<br />

Figures 5.8 <strong>an</strong>d 5.9, show a comparison between the attitude <strong>an</strong>gles<br />

provided by the vision system alone (see Paper III <strong>for</strong> details as to how the<br />

vision system calculates the attitude <strong>an</strong>gles), the attitude <strong>an</strong>gles calculated

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