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Old 01-06-2013, 08:56 AM   #41
R_Lefebvre
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Quote:
Originally Posted by Exposure View Post
Please explain to us mortals how a Z-axis gyro can help in any way with altitude control.
Sorry, not a Z-axis gyro, a Z-axis accelerometer. I mis-spoke.

Previously we only used the barometer to control height. This was somewhat imprecise and laggy. You had to have a significant error for it to be able to detect the change in altitude.

Now we are using data from the Z-axis accelerometer, which is much much faster. Put simply, at center-throttle-stick, the systems attempts to maintain a 9.81 m/s/s vertical acceleration. (ie: 1G) Any external force that attempts to move the heli is countered immediately by a response from the collective pitch. Far faster than a human can.

It's fairly simple. The only difficulty is dealing with the fact that we want very precise control, but the signal-to-noise-ratio on that accelerometer is pretty bad due to vibrations in the heli. Just have to employ lots of smart digital filtering.

I think we basically have it nailed within the limits of the deadband of the servos and mechanical slop in the system.

Againk, DJI basically have a system like this. But I'm not sure who else does.

Edit: just read the BeastX manual. It gives no clues at all what they are doing. I'm not even sure this is really the same thing, since mine doesn't do it flying manually. When flying fast forward and then pulling back on cyclic, it does pitch up sharply initially, but doesn't oscillate.
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Old 01-11-2013, 10:23 AM   #42
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I got all my blades in from Spin Blades. I wasn't super happy with the packaging. It arrived more banged up than anything I've gotten from China. I would have hoped for better packaging on something so valuable, long, thin and fragile. I had to inspect them all to make sure they weren't broken, but they seem OK.

I bought the "factory seconds" based on the fact I was told they were merely cosmetic defects, and would still be better than factory-first from most manufacturers. For the most part I'd say that's probably true. But one of the 700 blades actually has a small bit of de-lamination on the trailing edge. I wouldn't use it as is. I'll have to try a little CA to stick that down. I'm not sure if it's just a gel-coat layer or cosmetic overlayer, it appears to be just the white material.

I'll have to see how it goes, but I probably wouldn't order the seconds again.

So, hopefully I can functionally test these on the 450 soon.

Now question: How much negative pitch do I need to make sure I can get this thing down? Normally I try to use as little as possible, so that I get the best resolution I can on the collective stick. So typically about -3. But I fear on these maybe I need more negative?
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Old 01-11-2013, 04:38 PM   #43
madmcphil
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Default Re: Anyone try PS1/ Spinblades, Asymm. for AP?

Use -3 will still bring it down nicely

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Old 01-12-2013, 08:49 AM   #44
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There seems to be something inherently different about how the spinblades respond to collective input on hover. Maybe I have just forgotten that the phenomenon is simply an exaggeration of shorter chord, symmetrical blades. But it seems that if altitude is allowed to drop, the collective compensation needed to arrest the fall increases very quickly. I am experimenting with higher gains on my alt hold to see if responding more aggressively will diminish the +- 3m fluctuations in gusty conditions.
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Old 01-12-2013, 01:13 PM   #45
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Which controller are you using? I wonder if what you are experiencing is linked to Vortex Ring State. My 450 is tricky even with standard blades.

Quote:
Use -3 will still bring it down nicely
Thanks. And what about the positive side?
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Old 01-19-2013, 10:22 PM   #46
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Test flew the SpinBlades today. On my 450 heli, in 30-40 km/h winds. Not a lot of problem in Altitude Hold mode. It was still moving a bit, but not too bad. The servo on this thing are getting sloppy so I can't use as much gain as I should.
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