Replies to This Discussion

DeveloperPermalink Reply by jasonshort on September 26, 2012 at 9:09am

Hi, 

You basically want to tune down anything that says rate and P. So Rate_roll_P and Rate_Pitch_P should drop considerably. They are the gains that say how fast you need to turn the motor to get the desired rate of rotation. How much more thrust do you think you have? 20%, 30%? Reduce the rate P down by that much. Same goes for throttle_rate_P

Jason

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Permalink Reply by Michael Brown on September 26, 2012 at 1:14pm

Thanks for the advice. Makes sense. I will give it a try.

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Permalink Reply by wraith on September 26, 2012 at 1:55pm

you have to do the same when u change ur battery ie 3s to 4s

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Permalink Reply by Michael Brown on September 26, 2012 at 2:21pm

As that causes an increase in voltage is there any of the electronics that would not be able to handle the change from 3S to 4S? I cannot find any data if the APM 2.5 board can handle it and I would guess that the ESC's are good for it also. Any more insight?

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Permalink Reply by wraith on September 26, 2012 at 3:42pm

u are still getting only 5v through the s bec,  so i dont think the apm has problem its ur motors u have to watch , they might not be able to handle the extra load, , i killed my last set of motors that way but that was cause i was spining 10x4.5 on a 925kv motors with a 4s

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Permalink Reply by Phil Cramer on September 26, 2012 at 2:51pm

Michael, what's the pitch of your 12" props? I changed mine to 12x3.8 APC gray props and have found my 3DR 880kv quad flies pretty good with 2.73 "stock" settings. Also, I'm doing all my flying and tuning with the same payload even if I don't need the video camera and extra battery pack. My payload is a cam boom with either Sony NEX-5N or Sony CX-160 vid cam along with a second 2200mAh pack. Total 'payload' is about 550g. That's the extra 200g pack with a 350g cam. 

I think the 12x3.8 props "gear down" the lift. And the payload "dampens" the flight response. I notice a difference between pitch and roll. The camera and battery are fore and aft so they deliver a higher moment of inertia in pitch. So roll is 'snappier' and pitch is somewhat slower. I could adjust this by decoupling (unlock) the pitch and roll PIDs. 

So my advice is to add your payload and do your tuning with it. You didn't say, BTW, if your crazy flight was with or without payload...

Phil

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Permalink Reply by Michael Brown on September 26, 2012 at 5:47pm

Phil, thanks for the info. The props are 12x4.5 gray EPP from JDrones as that was the source of my quad and coming from a heli background I am not sure how the difference in pitch relates to lift with the quad. It is not much difference from your 3.8 to a 4.5. but it would add a little more lift. I was so worked up about how it was flying with no payload and the 12" props that I didn't give much thought to no load. Right now, all I am flying with for a camera is a GoPro which weighs in at 167g plus the aluminum brackets for the mount. All my load is at the center of gravity for the quad. I would understand more load dampening the flight response. I was also thinking of going to a hexa copter to get some more stability, reliability and load capacity even though I am not nearly carrying a load anywhere near to yours. I work for an electrical utility company and would like to do video inspections of equipment. I would eventually like to get to a setup of video transmission to a ground station. I am still kind of new to the quad as I had a difficult start and put it on the back burner for a while. I had to upgrade the board to an APM 2.5 as my board did not have enough memory to fit 2.7.3. The quad flew great with the 10"x4.5 props with the stock setup and that's why I got concerned when everything was so far out when I put the 12" on.

Now I am curious as to what your battery for the quad is. I am using a 3S 3300mah Turnigy nano-tech 45-90c discharge and I only got 3.5 minutes of flight before the quad slowed down and eased to the ground with a soft landing. I would like to know how well your system works and see what it looks like, if you don't mind.

Thanks for replying, Michael

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Permalink Reply by Phil Cramer on September 26, 2012 at 6:34pm

Michael, you're welcome. 

You've brought up a bunch of questions and I want to do them justice but I'm mid pay-per-view and a couple of glasses of vin blanc... 

PItch. Higher pitch yields faster air speed given the same RPM. The move from 10" to 12" with the same pitch makes a really big difference. Your change from 10 to 12 probably caused the big changes. I changed to 12" and lower pitch before I read a post here (I'll have to look it up later if you can't find it) that reinforced my decision. They were cited as a very good compromise for efficiency. So far they've worked well. 

I've flown a GoPro too. Mine is in the full housing with tripod mount. It doesn't make much difference in flight performance. 

A hex should get you more payload capacity. I'm not sure about reliability. They're supposed to be able to fly even with one motor out. But I'm not sure the two additional motors and associated electronics don't result in more complexity and potential for failures. But it's common in 'the industry' to use a hex for video and fpv. 

I'm using a 2200 mAh Turnigy (not nano) and I get five or more minutes with a light payload like the GoPro. I've got to think something is amiss with your setup. Maybe a bad cell, or a faulty motor in a bind or something. 3.5 minutes is too little. I haven't timed a full flight with two 2200 packs and the heavier camera load. How much payload are you carrying with the 3300 and 3.5 minutes? With no payload I can get six minutes plus and still be at a safe voltage. 

Later, I'll post a link to my flight videos and some photos or whatever you'd like. 

I hope this helps. Don't hesitate to ask for clarifications. 

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Permalink Reply by Michael Brown on September 26, 2012 at 6:56pm

I've had a long day and I get up at 5:30 so I am crashing, No wine for me. I hope it's a good video you are watching, I will fly some more when I get home Thursday from work and then we are headed out to dinner as it will be my birthday. I will try a different battery and I'm thinking of getting a total weight for the system. Enjoy, and later.

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Permalink Reply by Phil Cramer on September 28, 2012 at 4:10am

Here's a thread you might find worthwhile

http://diydrones.com/forum/topics/real-world-props-test?id=705844%3...

The originator of the thread concluded that 12x3.8 APC props were a best compromise for the various motors tested. I had chosen that prop before this thread so it was confirmation of my hunch. 

I definitely think that payload can have a big effect on flight characteristics. I'll also recheck my PIDs to see what my Stabilize Rate P is (or whatever the 'main' PID is). 

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Permalink Reply by Phil Cramer on September 28, 2012 at 5:35am

After reading your post again it occurs to me that for "inspections of equipment" (electrical), the GoPro might not have the best angle of view. It has an extremely wide angle. I find that it makes getting a close up shot very hard. Everything looks much too far away. I'm far happier with the widest angle of my little Sony Handcam CX-160 and my NEX-5N's 16mm. Here's a link to a short hop I made a couple of days ago with the CX-160. It's at dusk so it's a bit dark. I did a quick ascent to just above adjacent power line towers and when the quad drifted toward them I did a descent thru prop wash that was wobbly. But you get the idea. 

120923 Quad CX-160.m4v

Phil

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Permalink Reply by Michael Brown on September 28, 2012 at 7:07am

The GoPro is what I have at the moment. I know what you mean about the wide wide angle but I have to start somewhere. I just saw the video. Pretty good as far as I am concerned. Yes, I would need to get closer. Any more info on your battery for the quad and a photo. How long of a flight do you get. So many questions, so little time. Back to work. TTYL an thanks Phil.

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