Differences

This shows you the differences between two versions of the page.

--- searchwing-flight-124 [2019/12/25 11:27]
beckmanf added analysis
+++ searchwing-flight-124 [2019/12/27 10:06] (current)
beckmanf [Results / TODO] added fuselage
@@ Line 16: / Line 16: @@
 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 Analysis ====
 When the current waypoint is set to the last "Land" waypoint at 10:40:11, the target altitude is set to 0m.
@@ Line 48: / Line 48: @@
 Friedrich Beckmann (25.12.2019)
+==== Control Analysis ====
+During turns the aircraft sometimes lost quite some altitude. Looking at the logs there is some instance where the control was critical.
+| {{::swfl124-controllerstability-1.png|Roll and Pitch problems in turn}} |
+| Fig. 4: Roll and Pitch problems in turn |
+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.
+| {{::swfl124-controllerstability-2.png|Altitude and speed loss in turn}} |
+| Fig. 5: Altitude and speed loss in turn |
+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.
+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.
 ==== Results / TODO ====
+  * The new milled fuselage does not seem to show problems during flight. However, the turn behavior of the aircraft was not ideal. Is this related to the fuselage? Not clear, probably controller / wind related.
   * Every non-standard parameter setting should have an exact explanation why we set this. If you don't know what the parameter exactly means: **DO NOT CHANGE THE PARAMETER**
   * We should reestablish the non-standard parameter list in the gitlab and wiki
-  * The parameter **TECS_SYNAIRSPEED** [[https://ardupilot.org/plane/docs/parameters.html?highlight=land_type#tecs-synairspeed-enable-the-use-of-synthetic-airspeed|(link)]] is 1 , i.e. activated. The quote is: This is useful for development testing where the user is aware of the considerable limitations of the synthetic airspeed system, such as very poor estimates when a wind estimate is not accurate. Do not enable this option unless you fully understand the limitations of a synthetic airspeed estimate. We should switch this off which is the default.
+  * The parameter **TECS_SYNAIRSPEED** [[https://ardupilot.org/plane/docs/parameters.html?highlight=land_type#tecs-synairspeed-enable-the-use-of-synthetic-airspeed|(link)]] is 1 , i.e. activated. The quote is: "This is useful for development testing where the user is aware of the considerable limitations of the synthetic airspeed system, such as very poor estimates when a wind estimate is not accurate. Do not enable this option unless you fully understand the limitations of a synthetic airspeed estimate." We should switch this off which is the default.
   * I would be happier with a non-aggressive controller parameter set without D component. The servos get crazy. See PIDP log.
   * In case of emergency as in this flight with the target altitude set to 0m due to misconfiguration the stick mixing is completely useless. Maybe we should disable stick mixing such that we have to switch to FBWA if we want manual intervention. Makes analysis also easier.