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Permalink Reply by Jeff Smith on August 11, 2012 at 8:35pm

I'll look into it, the hardware/pcb design should be easy enough and I've been looking for an excuse to try one of the on-line custom PCB manufacturers anyway. It will have to wait as I just got done placing an expensive investment in ARM/AVR goodies.

The programming is what concerns me. If I build it and pass a few out would one of you be interested in helping with the software side?

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Permalink Reply by Jeff Smith on August 12, 2012 at 7:14pm

Finally got around to uploading a video, photobucket isn't working so I used YouTube.

I like the last minute... nothing impressive to speak of though :-)

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DeveloperPermalink Reply by R_Lefebvre on August 14, 2012 at 5:37pm

Ok, I think I'm officially done with Hobby King helis. Or at least the 600 parts.  I finally got down to rebuilding this thing, and it's a constant struggle.  It just sucks.  None of the parts fit, even when new.  I feel like an 18th century gunsmith, filing things to fit.  Last night I struggled with the washout control arms, finally got them on so they don't bind.  Today, I am trying to get the seesaw hub on, and it keeps binding up when I tighten the screws.  Must have a small machining error.  I throw it in my mill just to open it up a smidge inside. Just enough to take off the anodizing... but the pattern left reveals the surface wasn't flat to start with!  Now I try to put it on, and find out that apparently I've squished it a bit in the vice, because it's tighter than before!  Now, I couldn't possibly have squished it unless the aluminum was stupid soft.  Which it is...

So on goes the old one.  Looks OK.  I just wanted to rebuild a fresh head to be sure.  But looking through my old crashed parts, I see that I've had to file out that washout hub before.  I forgot, thought I'd be smart and mill it, but it just squishes in the vice.

Anyway, enough of this.  I may check out the new 550GT parts, because the new 450 Pro kit the released the parts are not bad.  But otherwise, I'll build with good quality stuff.

I've already got a 550 half built using all high quality aftermarket upgrades, should be nice.

I just don't want to buy an Align kit because they make you take all their electronics which I don't want.

On the other hand, I have to keep reminding myself I've had several crashes completely the fault of developing the code, and I couldn't afford genuine parts at the rate I was going through them.  But, hopefully things will have settled down now.

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Permalink Reply by Jeff Smith on August 14, 2012 at 9:39pm

I gotta +1 the Align stuff, even the electronics. I've got packs and packs through my 600efl and haven't had an ounce of mechanical issues. I did toss the out-runner in favor of a Setve Neu in-runner, but that is more because I LOVE NEU PRODUCTS than some legitimate deficiency in the Align motor :-)

Besides, if you don't want the electronics the price drops considerably to buy a stripped down version on eBay. The fit and finish of the Align stuff even in my micro sized 250 is phenomenal *if* you don't mind sizing ball ends...

Either way, I'm totally with you on the fact that crashing SUCKS and if it weren't for the giant training gear I keep on the 600 it would have been toast several times over (like my 250 has been). I like to do dumb stuff like fire up the rotor on the 600 when the APM is in default mode or whatever it is when you have the throttle (collective) up when booting.

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DeveloperPermalink Reply by Randy on August 15, 2012 at 9:06pm

@Jeff,

    that last comment about the default mode when throttle is up while booting..that must be a carry-over from the quad code for ESC calibration.  I've never done that but it sounds like a fixable "gotcha!" that we should take care of. thanks for the report.

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Permalink Reply by Jeff Smith on August 15, 2012 at 6:41am

Sorry, I've touched on this subject in two other threads now, but they are all related though I think most relevant here.

Using an ArduIMU V3 as a "camera gimbal" to stabilize the Optical Flow and sonar sensors.

The goal really is for me to get into some of the software that contains the DCM and AHRS code. I am also working on modding the code for the ArduIMU V3 to make it a simple flybarless module for my 250 traditional heli (not to save money over a legit AP solution as I could strap one to it right now, but space requirements of 28mm in width). I also have been feeling that using the OF for countering drift during hover would significantly improve the feel of my flying....

I won't get long and drawn out about *why* the gimbal, I just think an OF that does not change angle relative to the ground when the heli pitches and rolls will make for an easier tunable setup.

Your thoughts?

P.s. Robert, I hope I didn't come out snooty in the Announcing APM thread answering your question about how I'm going to mount the APM. Felt like it could have been mis-taken after reading my own post this morning.

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DeveloperPermalink Reply by R_Lefebvre on August 15, 2012 at 7:08am

I think I missed the context of this message, but OK.

The idea of using the ArduIMU V3 as as simple flybarless controller for small helis is really interesting.  I'd like to follow along on that project.  I didn't really have many intentions of doing GPS Loiter and all that with my 450, I only got it as a knock-around machine and test-bed for the code. And now I'm not sure how great it is at that, because even if I did tame the vibrations, it's simply very unstable in winds due to the size.  How many PWM outputs does the ArduIMU have anyway?

I would imagine it would be possible to created a stripped-down version of Arducopter with all the Navigation and Telemetry stuff gone.  The only thing I'd worry about is not enough EEPROM space for all the parameters needed for a Heli?

This probably deserves it's own thread.

As for the idea of a stabilized OF and sonar mount... yeah... I dunno.  To me that seems unlikely to work.  Well, it's probably good enough for the sonar.  But I'm not sure you'll ever get the thing to work well enough for the OF.  There's always going to be an error, and if the Arducopter is *assuming* that it's always looking straight down, when the ArduIMU and mount can't actually achieve that, I see the possibility of a nightmarish hardware/software feedback loop.

But, give it a try.  I've done lots of crazy things myself.

Now, to bring your other post here to make the discussion coherent for others.... and don't worry, I didn't take it as snooty, sounds a bit tongue-in-cheekish which is how I assume it's meant.

Robert :-)

My *intention* is to make an adjustable plate capable of about 15 degrees of roll and 5 degrees of pitch. Then velcro the APM to it and mount the assembly on the underside of the top of the battery tray (Align 600efl with the quick release slide in trays). I will precisely level the APM and zero it before installing in the heli, then adjust the tray to mechanically obtain a drift free hover, no auto_trim. I just think that the MPU-6000 will be happier that way, and I think there may be issues with the auto_trim not being applied in all modes properly I.e. hovers well after auto_trim in stabilize but wants to drift back and left in loiter. I know the conventional wisdom is weighted plates with various grades of futuristic BeastX super vibration isolating adhesive foams... but I just don't think the mass of the 600 is THAT prone to transmitting the vibes in an amount that will hinder the APM. Time very well prove me wrong :-)

If you think THAT is bad, I also intend on mounting the sonar and optical flow sensors on a camera gimbal style 3-micro-servo-in-120-dergee-format stabilized platform to keep them pointed straight down all the time (barring acro mode if we get that working of course). I'm working on making/modding the ArduIMU V3 for the task. I know the software is supposed to calculate the offset by angle vs altitude and all that, but I think just keeping the sensors pointed STRAIGHT down is a better way to go. Again time may very well prove me wrong LOL

I'll post up the carnage if it doesn't work out :-)

The adjustable mount is interesting.  Again, I'm skeptical it will work, but I'll be interested to follow along.  I have no opinion on the idea that the MPU6000 will be happier that way.  But the idea that the Auto-level works differently in different modes, I very much don't think that's the case.  

I agree that the 600 has less vibration problems than smaller helis... or rather, I think the vibes tend to be at a lower frequency, and the MPU is running fast enough it can actually SEE the vibes from the main blades and filter them out.  But I think the problem crops up when you have a bearing going bad.  That vibration can be very much higher than the rotor frequency.  It's also very variable in nature.  I suspect that's what causes most of the cases of sudden leans.

My heli flew beautifully for about 10 flights.  Then I had a minor crash with minimal damage.  I repaired it, but probably didn't go over it as thoroughly as I should have.  I suspect maybe a main bearing got damaged.  I did a test hop which was fine.  Then on the next flight, it crashed.  I suspect the variability of the vibes coming from a bad bearing is the cause.  They can come and go.

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DeveloperPermalink Reply by Randy on August 15, 2012 at 8:39pm

I don't think it's a great idea to try and stabilize the optical flow sensor.  Accuracy is key and a mechanical stabilization is going to have some lag in it and I suspect that will mess up the position calculations.  I think it's better just to account for that in software.  If you check out the ARParrot drone that also uses optical flow there's no stabilization going on.  Still, I'm not saying, 'don't do it'...it'll be interesting to see the results in anycase.

 

For sonar it would probably work fine because it's got such a wide beam, it doesn't really matter if it's perfectly pointing downwards but it would be helpful when you reach the limits of the beam (i.e. leaned over at >30 degrees).

 

yes, using the ArduIMU as a cut-down controller sounds cool to me.

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Permalink Reply by malcolm churn on August 15, 2012 at 1:57pm

I have just loaded the latest code 2.7.1, setup the heli, the apm is mounted a lot more solidly than it was before. Everything works well on the bench, I have removed the sonar and will be concentrating on getting the barometer to hold the altitude. I have removed all the I term from the stab settings. Will report more tomorrow. 

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DeveloperPermalink Reply by R_Lefebvre on August 15, 2012 at 2:12pm

Ok.  Did you ever test the Acro mode I sent you?

I'm also thinking of ditching my rubber dampers, and just going to the blue vibration damping grommets.  I don't have scientific evidence yet, but they seem to have given the best results so far.  That was when my 450 was at it's best.  Foam tape didn't work, and rubber dampers didn't work.  Not exactly scientific but...  And then my quad is flying awesome, even though it vibrates badly, and it has the blue dampers.  I had tried the blue dampers on the 600 before, but I think I didn't use them properly.

And I guess going way back in time, my very first 600 setup, I simply had the APM1 mounted on a plate with screws, and a couple of servo grommets squished between the plate and the APM.  That also worked fairly well...  I had a bit of leans, so I started on the crusade for ultimate vibration damping, but I'm not sure any of it worked.

I don't know when I'll actually get flying mine, but the head is half done and feeling nice.  I'm going off-roading this weekend, then the Maker Faire in Montreal the weekend after that, then probably camping the following.  But things should slow down in September.

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Permalink Reply by malcolm churn on August 15, 2012 at 2:20pm

I didnt get round to testing the acro code, sorry robert was busy sorting out the DJI system.

I want to get back to testing the ardu code on my 600. If 2.7.1 gives bad results then i'm going to go back to 2.0.40 and try it again, would it be possible to use the new GPS with that code?

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Permalink Reply by Jeff Smith on August 16, 2012 at 6:30am

Did a bunch of reading last night looking at the eagle files and available ArduIMU stabilization stuff out there. I found that of the 6 available PWM channels on the Atmega328p only 2 of them are available off the board (labled PWM0 and PWM1), 2 of them are running the red and blue LED's, 1 is used for data ready at the 5883 and 1 is used for the SPI communication.

So it looks like what guys are doing for camera gimbals ect, is either inputting/outputting PPM on the PWM0 & 1 lines, or using A0-A7 pins as PWM inputs, using PWM0 and PWM1 as outputs and converting other pins (D8, ect) to do PWM as a non phase correct PWM on a generic I/O's.

Haven't decided the best approach yet for what I want to do, but I am considering either removing the red/blue LED's and reconfiguring the pins (red/blue PWM and PWM0 & PWM1 output phase correct PWM to 4 channels, using PPM input on D8), or just running a Sparkfun Pro Micro or other small processor board as a PWM to PPM converter as an oil pan, but I haven't looked into that option much yet. I'd like to make this work with just the ArduIMU and not have to mod the board.

Any good reason NOT to use generic I/O's as PWM? How significant is it to not be phase corrected?

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