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HomeAircraftHelicopterHelicopter Main Discussion › To Bar Or To NoBar, That Is The Daring To Question
01-05-2015 07:57 AM  3 years agoPost 41
Climax

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Most of the 2 and 3 axis gyros used in FBL controllers have digital outputs, usually exposed via SPI or I2C. Interestingly the single axis PinPoint devices used by some of the high end units provide an analogue and a digital output.

Also in most cases you can still specify the internal bandwith if required, this is usually configured or set via an external capacitor. Typically this is left as large as possible and is then dealt with by the application with appropriate digital filtering etc.

Incedentally some of the newer Invensense parts work very well as demonstrated by the Spartan Esprit, especially on electric helis. The bulk of my FBL experience is with the PinPoint devices, however I am about to build an Invensense version... The PinPoint gyros are excellent but you need 3 of them as they are only single axis parts. With Invensense you can get almost as good performance but with a single device. This also works out to be a lot cheaper!

Electronics, Physics, Helicopters, Fixing Things...

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01-05-2015 08:00 AM  3 years agoPost 42
EEngineer

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Most of the 2 and 3 axis gyros used in FBL controllers have digital outputs.
You contradicted yourself...

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01-05-2015 08:09 AM  3 years agoPost 43
Climax

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The 2 axis parts are sometimes used with a single axis tail component. Is this what you meant?

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01-05-2015 08:25 AM  3 years agoPost 44
EEngineer

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No....

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01-05-2015 08:30 AM  3 years agoPost 45
Climax

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You've lost me!

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01-05-2015 08:37 AM  3 years agoPost 46
EEngineer

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Your analysis is of old MEMs gyro tech...used to work that way...

The contradiction in your discussion was that analogue noise interferes with the analogue gyro ouput.

When your opinion was challenged, you switched...as if digitized outputs were the norm....vs analogue rate outputs...

I can't envision how a capacitor would could improve the performance of an FBL..

And, no offense intended, post your data...

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01-05-2015 09:03 AM  3 years agoPost 47
Climax

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What!

The point I was trying to make was that the rotor generates a large and unhelpful signal that is superimposed on the desired rate output (digital or analogue). As far as I'm concerned with respect to a FBL control loop this has to be dealt with as it will ultimately detract from performance and if not can also end up as out of band noise on the servo outputs. That was all!

I know this to be true as I have spent an inordinate amount of time designing, analysing and building a working FBL controller. Try it, I massively underestimated the complexity and effort required. It's been a humbling experience!

As for referring to signals I had intended to be agnostic as to whether they were digital or analogue.

I'm done here! This thread is supposed to be about NoBar.

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01-05-2015 09:07 AM  3 years agoPost 48
EEngineer

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Well..then happy new year....

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01-05-2015 09:16 AM  3 years agoPost 49
EEngineer

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Just curious...what test and measuement equipiment do you use?

Myself...like the UK Picoscope...what do you use?

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01-05-2015 09:32 AM  3 years agoPost 50
Climax

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For the airborne stuff it's all bespoke as it has to be light weight. Mostly based around Microchip dsPIC33E and PIC32MZ embedded controllers, also PinPoint, Invensense, EEPROM etc.

The firmware is all in C with some assembler. The offline analysis is all written in C# for convenience (I really should use MatLab).

As for bench equipment, just the usual suspects, e.g. Tektronix etc.

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01-05-2015 09:36 AM  3 years agoPost 51
EEngineer

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Show me your data....

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01-05-2015 12:19 PM  3 years agoPost 52
Cobra 46

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Cambridge il usa

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This thread started out about flying without a controler , less parts less money, I think that's what the op was getting to. Now you guys are jousting about crap I dont understand . But it is entertaining ! Keep it up 😄😄😄😄

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01-05-2015 12:40 PM  3 years agoPost 53
Climax

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I have tried flying NoBar and didn't realy like it compared to FBL or Flybarred. It certainly keeps you on your toes, especially on a breezy day.

I guess I'm too old for it!

When I first learnt to hover I was a student and couldn't afford a tail gyro (this was back in the 80s). It was hard work but I persevered and got there in the end, all be it tail-in only! I remember when I finally did get a gyro, wow what a difference!

I don't think that NoBar is as bad, but I prefer locked in fun...

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01-05-2015 01:44 PM  3 years agoPost 54
icanfly

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ontario

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the rotor generates a large and unhelpful signal that is superimposed on the desired rate output
this info is very helpful, a lot of the info you brought here very informative, things I was not completely aware of until you posted.

Your replies have revealed aspects of the cp performance impacts on a fbl gyro most everyone would otherwise be in the dark on. If it were possible to review nobar performance (I may go there again with a 450 and video the outcome) there was a time a certain heli I had which was unstable in the roll axis while more calm on the pitch axis, I turned the battery sideways to balance it in the roll axis and the heli became easier to manage.

If the present form of e heli configurations lends itself to improvement of any kind it's nice to know and be able to do something about it, 99% of the world not giving two cents worth to more than end use.

Maybe I need to go back to nobar and correct some balance inconsistencies. leverage, that's what was the problem with nobar, the wind exerting added unpredictable lift like a plank will suffer in wind. The 3x gyro doing partial work correcting for what it can, while smaller helis experience more wind effect due to small size, mass, momentum.

btw, when I did the basement hover test the body was not on, I did one more hover before going out doors and had put the body on adding a couple of ounces on a 1lb machine, it tamed it that bit extra.

This whole nobar topic begs to ask, if nobar was perfected and proven successful would guys leave 3x gyros? There have been many attempts on nobar, have you ever tried to spin a Jack with only two arms? now add wind,

I suppose what is at the heart of this is examining the gyrotational forces of a rotating object and how they affect a rc heli + or -ly. Even a plank with a 3x gyro flies a lot more stable and predictably.

Climax, continue please, what fbl controller did you work on?

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01-05-2015 02:10 PM  3 years agoPost 55
Climax

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The real work is commercial and UAV related. However as model helis are a passion of mine, we (myself and a like minded friend) couldn't resist building our own FBL controller. There are some photos, a video and other sketchy details in my gallery.

The funny thing is that UAVs are quite a bit easier to control as they are much more constrained and don't have to 3D!! Building a generic FBL controller that works well on all of our extremely agile 3D models is a real challenge. As we know, not all manufacturers have been able to pull this off to the same degree!

I'm pretty sure that NoBared helis of the type we all like to fly will struggle to compete with flybarred or FBL versions. That's not to say that you can't have fun trying!

One thing that we've noticed is that NoBar does achieve nice crisp aileron stops, but the elevator can be a bit bouncy especially if the COG is off.

Electronics, Physics, Helicopters, Fixing Things...

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HomeAircraftHelicopterHelicopter Main Discussion › To Bar Or To NoBar, That Is The Daring To Question
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