First successful autopilot flight
After a long period of bad, rainy & windy weather, we finally had a perfect weekend. Sunny and only 1-2 BF wind. Perfect for testing my autopilot.
After some first tests on Saturday, I discovered my EB-85 GPS was also suffering from a known firmware problem. After a minute of flight, the data coming from my GPS module was useless, and my plane kept flying North instead of circling around the home waypoint. Damn you, E-Tek!
Anyhow, as a quick hack to make things work a bit more reliably, I hot-restart the GPS unit every 50 seconds. Also, I set the maximum roll angle the autopilot will use to 17 degrees. These gentle movements will less likely confuse the GPS unit.
And it worked! The easystar circled nicely around it’s one waypoint (being the take-off position). For 25 minutes, my transmitter was laying on the ground while I was just watching the plane. Must have been a weird sight for the people passing by for a walk on this beautiful day :-)
These are some other things I’m having in mind for my autopilot:
- Programmable waypoints
- Improve attitude stabilization on fast unstable planes
- A downlink with some kind of groundstation software
- Document the code better
- Create a new PCB with static and maybe a dynamic pressure sensor… + using a dsPIC with more flash ram.
I only I had more time :-)
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Congratulations!
— ComSubVie, 13 February 2008, 20:23 | #
Congratulations Tom, looks like your AP is getting close to be ready. Remember that there are several of us who have offered to help and get involved. Please let us know when you are ready !
Cheers!
— Mariano I. Lizarraga, 15 February 2008, 06:21 | #
Hi Tom,
Glad to heard that you got the first successful flight. Due to my job and family consumed me lot of time, my project delay and delay. Hope I can have my first flight within 6 months.
— Brian Ho, 27 February 2008, 05:27 | #
Hi Tom, congrats on your successful flight. I do have a few questions – looking at your photo, I see you’ve incorporated the SFE’s 5-DOF IMU board, presumably for attitude sensing. My question has to do with the performance of that IMU system – how have you managed to address problems with vibrations affecting the performance of the KF? I have a similar system, although using a slightly different sensor but am finding that vibrations are causing the IMU performance to suffer drastically. I’d love to hear how you’ve addressed that problem. Thanks.
— Daniel Wee, 11 April 2008, 14:12 | #
Hello Daniel,
My first tests on a very small delta wing were less successfull. I’m not sure if it was due to vibrations or something else (bad EB-85).
Now I do my tests on an easy star, and I seem to have no problem with jitter, after over 20 flights. The 5DOF contains a basic analog low pass filter. I added an extra low pass filter in software for every sensor.
How does the vibrations affect your IMU? Are the accelerometer’s readings very noisy or does the gyro drift very fast?
— Tom, 11 April 2008, 14:49 | #
Hi Tom, A couple of things – the newer EB-85A’s seem to have fixed the firmware issue. There are also other MTK set GPS units that you might want to consider. E-mail me if you’re interested in the info.
What I’ve found is that my unit behaves well on the ground but once there is some vibrations, the tracking goes off. It looks like the accelerometer is what’s getting hit the hardest. It might be that my implementation is off so I’ll have to check that but basically once I kill the motor, the unit tracks again. I’ll try to get a video up so maybe you can see better what I mean.
— Daniel Wee, 11 April 2008, 16:07 | #