Replies to This Discussion

Permalink Reply by Benjamin Lanehart on December 18, 2009 at 1:56pm

Try these links:

Link #1
Link #2
Link #3

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3D RoboticsPermalink Reply by Chris Anderson on December 18, 2009 at 2:25pm

All this is answered on the site, if you'll spend a bit of time reading before asking, but here are some shortcuts:

Q1: yes-ish

Q2: yes.

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Permalink Reply by Tim McMahan on February 20, 2010 at 7:16am

I now have everything I need for my Ardupilot except flight stabilization. I WAS fighting with the idea of using the IMU, or trying to make one, but from the looks of this, I need a few years of college before trying anything other than the IR sensors. Am I misinterpreting that? Can anyone clarify this for me? My airframe is ready, I'm assembling the Shield today, I just don't want to wate anymore time or ennergy if the IMU is totally out of my league anyway. Does the Ardupilot 2.5 code support the ArduIMU?

Thanks,
Tim

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DeveloperPermalink Reply by Mark Colwell on February 20, 2010 at 7:39am

Tim, what you want will be ready soon in a week or so, Doug and I are flight testing now. ArduPilot_IMU looks very good now, but wont be released until it passes successful flight testing. I am testing on a neutral stability Stryker II, Doug is testing with a high wing trainer, I did fly last week but, I had RF interference, still ArduPilot worked as designed, it entered FailSafe and stabilized craft until 72mhz RC rf link returned and I landed. Im fixing rf problem and will resume flight testing, but weather in Colorado is not good for flying now, snowing and windy...

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Permalink Reply by Tim McMahan on February 20, 2010 at 7:52am

That's fantastic news! Snow and wind? Isn't that what you want to test in? That way some yahoo like me in calm conditions should do fine, LOL. j/k
Will this be someting that someone brand new to autopilotinig can do? I was in a robotics club, and did some Atmel programming in Bascom, but am new to Arduino. If this is something that requires a high level of expertise, then I should probably just go with the IR and possibly upgrade later.

By the way, thanks for the crazy-fast reply!!
Tim

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DeveloperPermalink Reply by Mark Colwell on February 20, 2010 at 9:37am

I started Ardrino embedded development with this project last year, you should have a big advantage, just start... Maybe after I tune the PIDs for normal fast flight, I may do high wind conditions PIDs too, but how do you measure cross winds besides GPS track error? This aircraft should handle wind well. I like to fly it when wind is 10 plus, It will almost hover in one place at 20 mph winds. But it can spiral in easily too. I have onboard video to prove it..

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Permalink Reply by mark on February 22, 2010 at 11:38pm

From my understanding, if you're using an IMU it's best to have ailerons. Most users on this site use Easy Star but that doesn't have ailerons. Are there a couple RC planes that you'd recommend for the ArduIMU?

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DeveloperPermalink Reply by Mark Colwell on February 23, 2010 at 12:17am

I don't know about that, I think it depends on the plane, you can usually add ailerons to EasyStar or most similar planes. I added them to my GWS SlowStik, but I reduced dihedral to 2% or You could get a similar plane with ailerons built in. There are lots of choice out there.

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Permalink Reply by mark on February 23, 2010 at 12:19am

The ArduPilot is optimized for EasyStar, correct? Is the same true for ArduIMU or does it not matter too much?

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DeveloperPermalink Reply by Mark Colwell on February 23, 2010 at 12:27am

PID loops controls aircrafts responce based in inputs from attitude sensor, either IR or IMU gyros/accels/compas.
For a good plane check this blog

DeveloperPermalink Reply by Doug Weibel on February 23, 2010 at 8:18am

ArduPilot is not optimized for EasyStar. A lot of the development and testing work has been done with the EasyStar and the default gain values in the header file come mostly from working with EasyStar.

However, 2.5.1 changes the control code to full generic PID control for all control loops and all the little bits of code that were put in to make things work well by trial and error with the EasyStar have been removed. Most of those didn't make the final revision on 2.5 either.

Ailerons and IMU do not necessarily go together. ArduPilot will work equally well with the IMU or thermopiles in a rudder/elevator airframe. The issue is that many rudder/elevator airframes do not perform very coordinated turns so AP control will not be as good as with a better handling airframe. But you can still make it work. I think most of the sentiment that you should have ailerons with IMU is from the perspective of the IMU gives you more accurate attitude info that thermopiles and to take advantage of that for precise control you should have a more capable airframe.

One thing people need to understand is that if you use an AP with a different airframe then you need to expect to do some tuning to the gain values in the header file. Gains that work well in a EasyStar will not be the best gains for a SuperStar or a Predator or a Swift II or a .....

Permalink Reply by Roy Brewer on February 24, 2010 at 5:39am

Michael,

I was thinking about something similar. There are at least 2 data-driven tuning techniques that I'm aware of -Virtual Reference Feedback Tuning, and Fictitious Reference Iterative Tuning - that could probably be adapted to auto-tune the PID gains based on flight data. I'm sure there are others. We are planning to write our groundstation s/w using python(x,y), which has GUI packages as well as mathematical ones.

- Roy

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