Flight tests with ArduPilot in EasyGlider Pro

I posted an earlier blog with pictures on how I placed the avionics in an EasyGlider Pro for autonomous flight. I found out that was the easy part! Now I’m performing flight tests to hone in on the code mods for stable flight ( as Jordi states, the latest code is optimized for the EasyStar). My method has been:
Fly and observe performance in autonomous mode – record observations – make code modifications on laptop – remove GPS and upload code – replace GPS – fly again. Laborious but also fun since physical computing yields immediate effects that you get to see.
I’ve attached a table I made in Excel to organize my iterations and keep me on track. Maybe this will help others in the same situation. One mistake I made was getting in a hurry to go fly. I could have found out about the reversed servo throws and IR sensor placement by just walking the plane around on the ground and changing its attitude by hand. This would have avoided the “death spirals” I experienced on that first day of flying!
Bryan

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Comment by Matt on May 20, 2009 at 6:11am
Thanks Bryan,

I had another go at it today with the Predator 74".
This time, without any code changes, I hit RTL and the nose porpoised up and down at about 1hz. I don't know why it didn't do this the last time I flew...... then suddenly the very small spar folded and the aircraft was destroyed.
The ardu had all the pins bent, so rather than having a potentially faulty Ap in the air I threw it out.

I have an easy glider copy on the way from hobbycity called the Turnigy Rogue. Only $49USD and a 2nd 328 board I can use.

I'll use your settings as a start point. Could you post your code here so I can see your current settings?

Thanks again

Matt

3D Robotics
Comment by Chris Anderson on May 20, 2009 at 7:40am
Sorry to hear about the Predator! If it hadn't been destroyed, I'd have advised you to change the pitch gain (probably the I term). It's a shorter-coupled airframe than the EasyStar, which is why you had those oscillations.
Comment by Bryan Cuervo on May 20, 2009 at 2:25pm
Sorry about the Predator Matt. The most frustrating experience is different flight behavior without any code changes!!!! You may have flown that last RTL flight at a higher throttle setting and this may have been the cause of your pitch oscillations?
Unfortunately I still haven't found the right code settings for my EasyGlider and I'm still experimenting. Any code changes are shown in my posted flight tables and the changes that have shown promise are hilighted yellow.
Comment by Matt on May 20, 2009 at 3:41pm
OK, well when I have my EasyGlider I'll have a good go at the settings...
.... or maybe 2.2 will be out by then. :)
Comment by Bryan Cuervo on May 23, 2009 at 4:29am
Latest flight tests-- I'm realizing the importance of throttle management so it sounds like the Ardupilot shield with the pressure sensor will be a big help. Pretty strange how the weather appears to have such a strong effect on performance.


3D Robotics
Comment by Chris Anderson on May 23, 2009 at 7:00am
Byran,

Yes, that's why we added the airspeed/throttle loop. We were unable to get consistent results with the EasyStar in wind. A powered glider, because it's so affected by wind, is actually one of the hardest planes to use for a UAV. (AttoPilot actually recommends against them). But they're easy for beginners to fly, and the EZ is cheap and indestructable, so we picked it anyway. The FunJet can fly well autonomously in the wind without an airspeed sensor, but the EZ (and other powered gliders, such as yours) needs one.

Moderator
Comment by Graham Dyer on May 23, 2009 at 10:34am
Bryan, well done on having the diligence to record the parameter changes and their apparent effects! It really helps those of us in the same boat trying to get a non-standard airframe to navigate correctly - some of my experiences blogged here: http://diydrones.com/profiles/blogs/failures-and-sucesses

keep it up...:-)
Comment by wilsonj on July 28, 2009 at 1:14pm
Bryan, any update on the EZglider testing? I'm about to head down that path myself.

Are you using a Y connector for the aileron servos? The reason I ask is that I tried putting an FMA on just one aileron servo and to me it worked better than it did when using a Y connector. Not what I expected....
Comment by Bryan Cuervo on July 28, 2009 at 3:59pm
Hi guys,
For the moment, I'll stay grounded untill the Ardupilot code is fixed. Peter M. has been putting in a lot of flight time trying to diagnose what the problem is and he is flying the recommended plane. Between Peter's flight tests and Jordi's programming skills I'm sure there will be a new code revision that will work fine.
Yes, I'm using a Y connector for the ailerons and the rudder is fixed. I've used the FMA Copilot on an electric trainer that also had just just one aileron servo like you described and it did work great. Unfortunately, I 've not gotten the "fly by wire" mode to work in the last two Ardupilot codes so it's tuff to compare. Overall, I think the EasyGlider is a good performer and the Elapor foam is easy to work with but there isn't much room in the stock cockpit.

3D Robotics
Comment by Chris Anderson on July 28, 2009 at 4:04pm
Bryan,

To get fly-by-wire to work, change the gain settings in the config file to 8. Our default of 16 was too high.

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