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searchwing-flight-124 [2019/12/26 04:03] beckmanf added quotes |
searchwing-flight-124 [2019/12/27 09:56] beckmanf added control analysis |
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The last waypoint was landing. After that waypoint was active, the plane lost altitude and then probably stalled and crashed near the street. | The last waypoint was landing. After that waypoint was active, the plane lost altitude and then probably stalled and crashed near the street. | ||
- | ==== Analysis Landing ==== | + | ==== Landing Analysis ==== |
When the current waypoint is set to the last "Land" waypoint at 10:40:11, the target altitude is set to 0m. | When the current waypoint is set to the last "Land" waypoint at 10:40:11, the target altitude is set to 0m. | ||
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Friedrich Beckmann (25.12.2019) | Friedrich Beckmann (25.12.2019) | ||
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+ | ==== Control Analysis ==== | ||
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+ | During turns the aircraft sometimes lost quite some altitude. Looking at the logs there is some instance where the control was critical. | ||
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+ | | {{::swfl124-controllerstability-1.png|Roll and Pitch problems in turn}} | | ||
+ | | Fig. 4: Roll and Pitch problems in turn | | ||
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+ | Figure 4 shows the roll and pitch problems during a turn. The target roll angle is -40° but the actual roll angle is -90°. The target pitch is +15° and the actual pitch is -40°. This is a critical control situtation. | ||
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+ | | {{::swfl124-controllerstability-2.png|Altitude and speed loss in turn}} | | ||
+ | | Fig. 5: Altitude and speed loss in turn | | ||
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+ | As a result there is an altitude loss of 12m versus the target altitude of 50m and the speed decreases to 9 m/s in the following recovery phase. | ||
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+ | My guess is that the controller settings of PIDP, PIDR and the NAV controller is too aggressive resulting in controller instability and possible control loss under certain circumstances. I suggest a less aggressive control strategy which may result in path following errors but more stable flight behaviour. We can improve controller settings during extensive flight tests later. | ||
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==== Results / TODO ==== | ==== Results / TODO ==== |