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Permalink Reply by Derek Ernewein on July 7, 2012 at 4:46am

I am working on building a carbon fiber frame that will be 40 inches motor to motor. However, until all of the parts arrive (waiting on wire, connectors and screws) I have built the quad on a 450mm (17.5 inch motor to motor) frame that I got cheap off ebay in order to make sure that all of my parts are working. Perhaps you could try a smaller frame for now to make sure the only change is the frame (really just motor location on your existing frame would work) which make the difference. That would help answer your unknowns like ESC location and APM mounting method.

I wish I could help with PID tuning, but I am simply not there yet. Hopefully I will be by the end of next week.

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Permalink Reply by Jae Paik on July 9, 2012 at 7:45pm

Yeah, thought about slimming down the frame.  Will need to scrounge up some money before going that step though.

Let me know how your behemoth takes shape and behaves.  If you get it tuned well share the joy.

Thanks!!

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Permalink Reply by Derek Ernewein on July 12, 2012 at 7:22am

I flew my 1000mm frame late last night. It leaned to the front right corner when trying to take off. Giving it more throttle quickly got it of the ground good though. I need larger landing gear to stop it from leaning.

Once it was off the ground it flew fairly stable with the default PID settings considering it is over twice the size of the quad that the default PID were setup for :P

I will be doing the PID tuning soon. I have increased the logging and got the "APMLogVisualizer" to help see what the output is.

I have read a lot about PID controllers and how to tune them now. I think I have a good grasp on what to do to be able to tune this thing now.

However, I had a very big problem with Yaw.... It appears that I have no Yaw control at all. The motors speed up as they should but nothing happens. The props are not the correct size (smaller pitch value than they should be), so that could be part of it giving less thrust than it should be. We'll see.

I broke some of my temporary plexiglass frame. I am going to try making it out of thin plywood next and try flying again.

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Permalink Reply by JeffBetts_KK4MTC on July 7, 2012 at 8:57pm

Sounds like you should increase the RateP gain to make it not quite so sloppy, and adding some expo to your transmitter should help with the over corrections. Do you have a transmitter with rotary knob you can use to tune parameters while flying? My DX8 does, and it's a HUGE help in tuning. Best of luck.

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Permalink Reply by Jae Paik on July 9, 2012 at 7:47pm

Yeah, at one point, I believe I hat the RateP to max but that wasn't helping much.

Someone is lending me their DX8 in few days so will try out the in-flight tuning feature.

Thanks!

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Permalink Reply by JeffBetts_KK4MTC on July 10, 2012 at 7:37am

This is a good reference for Rate and Stab PID tuning on multicopters... http://aeroquad.com/showwiki.php?title=PID+Tuning 

My quad is stable, but I'm about to put it through this process and see what I get. Then compare it to what I had. 

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Permalink Reply by Jae Paik on July 10, 2012 at 10:31am

Yeah, I read that.

Seems like most tuning requires you to hold the quad in your hand.  It gets pretty hairy with my monster.  I will need to come up with some rig rather than holding it in my hand.

What's your quad's spec?

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