What flight dynamics can be achieved with EasyStar using autopilots
Part 1: latitude/longitude hold
I am posting an example with relaxed altitude hold (+/-10m vs 50mAGL) using 6DOF IMU autopilot.
GPS reception notoriously drops from 10 to 4 sats because of heavy roll (up to 40 commanded and some 50 achieved roll - 6-11m/s windgusts).
My goal was to achieve dogfight-like performance from rudder-only navigation.
Because I used full IMU autopilot, the navigation was smooth and reliable even when the GPS course was jumping at times.
The autopilot is a prototype used the previous year for winter tests. This time, I am focusing on optimising it for the most popular amateur UAV platform.
The navigation algorithm was brutal (not used in regular navigation in this autopilot which loiters around waypoint): hit home position with max allowed roll of 40deg.
Further technical details are not yet released.
This time GPS home position stayed in place, but at my location it likes to drift around by 50m every few minutes depending on the choice of satellites (no EGNOS enabled).
I am posting an example with relaxed altitude hold (+/-10m vs 50mAGL) using 6DOF IMU autopilot.
GPS reception notoriously drops from 10 to 4 sats because of heavy roll (up to 40 commanded and some 50 achieved roll - 6-11m/s windgusts).
My goal was to achieve dogfight-like performance from rudder-only navigation.
Because I used full IMU autopilot, the navigation was smooth and reliable even when the GPS course was jumping at times.
The autopilot is a prototype used the previous year for winter tests. This time, I am focusing on optimising it for the most popular amateur UAV platform.
The navigation algorithm was brutal (not used in regular navigation in this autopilot which loiters around waypoint): hit home position with max allowed roll of 40deg.
Further technical details are not yet released.
This time GPS home position stayed in place, but at my location it likes to drift around by 50m every few minutes depending on the choice of satellites (no EGNOS enabled).
Tags: EasyStar, IMU, autopilot, dogfight, hold, navigation, waypoint
- Attachments:
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Rudder dogfight.png, 394 KB
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Replies to This Discussion
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ModeratorPermalink Reply by Chris Anderson on -
Nice! Love seeing some of the performance of your autopilot emerge. You know more than almost anybody here, so I'm really looking forward to watching you take us to the next level.
IMO, the EasyStar is very good testbed, not because it's an easy platform to make into a good UAV but because it's a hard one and forces you to really refine your algorithms. As a relatively light powered glider without ailerons, it handles wind poorly and can't do coordinated turns. If you can fly tight patterns with an EasyStar, you can flight tight patterns with anything!
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ModeratorPermalink Reply by Krzysztof Bosak on -
This time:
EasyStar navigation in extreme winds is marginally possible when relying on IMU-based heading when GPS course is intermittent. The key is precise roll feedback, which on one hand allows deep turns, on the other hand is must never pass target roll by more then 10deg.
Unfortunately Alti Hold has been disabled, because sudden pressure variations and the turbulence in open autopilot bay were destabilising control too much (damaged autopilot bay cover during one landing that day).
The throttle was held constant at pretty high value, normally allowing some 50-60km/h cruise speed. - Attachments:
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Ultrawind.wmv, 9.7 MB
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ModeratorPermalink Reply by Gary Mortimer on -
Why did you take off downwind??
Pitching up and stall turning might be the way to get it all a little tighter.
Changing speed as well, slowing down for the turns.
Tighter turns running with the motor?
Looking forward to it!! Reckon you could get it to fly around a building??
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ModeratorPermalink Reply by Krzysztof Bosak on -
"Why did you take off downwind??"
Because it's faster ;-) More seriously, ground level wind was very small at this precise moment (tree line helped) and I didn't wanted to pollute the GPS log by intersecting takeoff and autonomous.
"Changing speed as well, slowing down for the turns."
I want reliability, and simplicity.
1nd option: no throttle control at all.
2nd option: airspeed based throtle control, but for sure lowering rpm in a turn is a recipe for stall. This is something we dont want. I dont want shaky flying, I want as dynamic response in adverse weather condition as it gets.
The mission of EasyStar is to bring the airplane above launchsite without damaging the camera even if the weather situations worsens.
The whole autopilot navigates well, the goal is to make navigation formula 'foolproof'.
"Reckon you could get it to fly around a building??"
As soon as I find one without chickening chickens inside.
I don't want to make the locals get upset about whizzing plane at the village.
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ModeratorPermalink Reply by Gary Mortimer on -
I dare you to paint it in a fox scheme and fly it around the chicken shed.
Or paint one of these up
and train the chickens for an escape. Now that could make a movie...........
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ModeratorPermalink Reply by Krzysztof Bosak on -
Chicken Run?
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ModeratorPermalink Reply by Krzysztof Bosak on -
"Pitching up and stall turning might be the way to get it all a little tighter."
What limits the turnrate? The wing's lifting force. When stalled, the wings can lift less. It is never a good idea to stall a beatiful flying machine, once again revealed.
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ModeratorPermalink Reply by Krzysztof Bosak on -
PLS observe on what can be achieved with full IMU navigation in extreme winds:
proper heading integration coupled with GPS allow waypoint convergence even when groundspeed is close to nil (a few km/h). - Attachments:
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High wind wpt.png, 333 KB
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ModeratorPermalink Reply by wayne garris on -
Krysztof,
love your work . do you use lateral acceleration compensation ? a static tube can help with help with the fuselage compression problem.also the ultrawind .wmv link does not seem to work.
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ModeratorPermalink Reply by Krzysztof Bosak on -
Lateral accel in use, before the plane was only able to 30s loiter time, now it is 'foolproof'.
"wmv link does not seem to work."
Just tried it again, it works fine... the encoder was MPEG2 or something. Nothing too fancy to handle...
"Fuselage compression problem?"
This is not a submarine! I am confused... Static pressure is indeed used for alti hold but...
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ModeratorPermalink Reply by wayne garris on -
"Unfortunately Alti Hold has been disabled, because sudden pressure variations and the turbulence in open autopilot bay were destabilising control too much (damaged autopilot bay cover during one landing that day)."
the air pressure inside a fuselage can be different then outside . i like to fed my pitot tube to one side of the differential and a static tube to other differential and also to the absolute , eliminating most false readings due to turbulence . also firefox was the problem with the .wmv.
thanks
wayne
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