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Author Topic: Why Fly-By-Wire exists  (Read 14524 times)

Offline Kim Doherty

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Why Fly-By-Wire exists
« on: August 28, 2013, 05:29:17 PM »
Almost since I flew my first control line model (TD-4) in 1960 I began to understand the need for a better way to teach someone how to fly a control line model. I certainly did not "get it" on my first few flights. (thank god for rubber bands and grass) In fact I did not really learn how to fly in a true controlled manner till I was 9 years old. (1963).

As time wore on and I began to wear out I could see that control line was in trouble. That was a long time ago. At that time I had no idea as to how you could make a really easy to fly trainer that would not crash. One day a few years ago while watching Pat Mackenzie fly a foam F3P model in a gym it came to me. If you were going to build a crash proof trainer you had to tell the pilot of the crashing model to straighten his hand out and level the plane. Of course you would never have enough time to do this so I needed a better solution. Why not just seize control from the pilot before things get really out of hand. There was just one long problem, the pushrod. The pushrod had to go. What to replace it with you ask? Why of course, a servo. And why a servo? Because if the bellcrank and the control surface are not connected mechanically I could seize control and redirect the model back to safety regardless of where the pilot's hand was. And thus was born the idea of control line fly-by-wire.

I have a reasonable idea of how to determine whether the model is right side up or upside down and climbing or diving. I think I can make the model take off under it's own control, climb to say ten feet and then let you "play" inside the hemisphere (or control how much of the hemisphere you can play in) then level off and land.

Having the original post of pictures of a bellcrank moved to an area not connected to electric flight without so much as a heads up from the moderator is rude. I put significant effort into documenting the parts to be able to share with all modelers. Now that effort has been undone.

I must say that the negativity towards the idea and the veiled implication that I might be cheating if I used such a model and put in a very good flight has left me questioning whether any further effort in this regard is warranted. You are certainly entitled to your opinions but not to disparaging my character. Judges and fellow competitors I may fly in front of or with may read these posts and form an opinion not based in fact. It is too late to tell me that that was not the intent as the damage has been done.

If Kim Doherty puts in a great flight with a fly-by-wire model (which I am quite capable of doing without this system) then I must be cheating.


Incredibly disappointed,

Kim.


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ChrisSarnowski

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Re: Why Fly-By-Wire exists
« Reply #1 on: August 28, 2013, 08:48:49 PM »
Maybe the moderators are not as skilled as Sparky and could not move just the last part of the thread to the debate-zone.
I would like to see the technical info returned to this section. Sparky can you help?

-Chris

Offline Igor Burger

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Re: Why Fly-By-Wire exists
« Reply #2 on: August 29, 2013, 12:48:07 AM »
I have a reasonable idea of how to determine whether the model is right side up or upside down and climbing or diving. I think I can make the model take off under it's own control, climb to say ten feet and then let you "play" inside the hemisphere (or control how much of the hemisphere you can play in) then level off and land.

So do it Kim, we will certainly applaud you. The biggest trouble here is that you take all too personal. It is not about YOU, not about "cheating Kim", it is and always was about RULES for stunt. The problem is that RULES cannot prevent anyone using FBW from cheating. And it is clear that anyone having well working FBW system vill see how to push it further. Now you described your autopilot, Doug wrote about gyro, I wrote about quadcopter robotics, it is eavrything doable with existing technology. We simply 1/ are not able define what is and what is not cheating and 2/ cannot inspect and verify if that defined cheating is or is not used. That is reason why I think the controlls IN OUR ACTUAL STUNT should be mechanic.

As I wrote - I will be happy and I will enjoy some "open class" with all allowed ("all" because we cannot define what exactly), but I am sure that it will be constest of 3 or 4 persons on planet, and I simply want my old friends fly with me longer.

Offline Crist Rigotti

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Re: Why Fly-By-Wire exists
« Reply #3 on: August 29, 2013, 06:24:02 AM »
Well said Igor.
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Offline Mike Anderson

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Re: Why Fly-By-Wire exists
« Reply #4 on: August 29, 2013, 07:04:27 AM »
As for moving the thread - the original thread had nothing to do with electric power for models.  It had to do with control systems ...

as does this one.
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Offline John Cralley

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Re: Why Fly-By-Wire exists
« Reply #5 on: August 29, 2013, 07:25:49 AM »
Still Kim's original post is of interest to many of us that are interested in electric powered control line. Let us not begrudge him a chance to show innovations, that he is working on, to those of us interested in them. Putting the thread into the debate section does just that. Persons most interested in his activities are mainly those of us that frequent the "Gettin all AMP'ed up" forum. I personally do not pay any attention to the Debate forum nor do I usually view the forums on construction, finishing etc.
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Offline Mike Anderson

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Re: Why Fly-By-Wire exists
« Reply #6 on: August 29, 2013, 08:19:15 AM »
It is (presumably) also of interest to some 'glow only' members who never come here (electric power).  One can always post a short note with a pointer to the thread in this forum.

It is perhaps more suited to either the "Design" or "Engineering"  board.  Even the 'Rules' board would seem to be at least somewhat appropriate, given what the whole thing turned into.

I would agree that moving it to the "Debate" board may have not been helpful to it.  I don't go to that section much either.

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Offline John Cralley

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Re: Why Fly-By-Wire exists
« Reply #7 on: August 29, 2013, 11:45:52 AM »
Mike, Point taken.
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Re: Why Fly-By-Wire exists
« Reply #8 on: August 29, 2013, 04:19:43 PM »
It is (presumably) also of interest to some 'glow only' members who never come here (electric power).  One can always post a short note with a pointer to the thread in this forum.

It is perhaps more suited to either the "Design" or "Engineering"  board.  Even the 'Rules' board would seem to be at least somewhat appropriate, given what the whole thing turned into.

I would agree that moving it to the "Debate" board may have not been helpful to it.  I don't go to that section much either.



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Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #9 on: August 29, 2013, 05:46:11 PM »
I must say that the negativity towards the idea and the veiled implication that I might be cheating if I used such a model and put in a very good flight has left me questioning whether any further effort in this regard is warranted. You are certainly entitled to your opinions but not to disparaging my character.

  I haven't seen anyone suggesting that you are cheating in any of these threads (nor the one before). And in fact, since there are no rules preventing any possible functionality of the system, it's literally not possible to cheat as it currently stands. Using a fully programmed autopilot is current LEGAL and there is nothing to prevent it in the rules.

   What everybody is concerned about is autopilots. As I mentioned when this first came up, *autopilots are going to be banned*. I don't think you are likely to disagree with the point we don't want an autopilot doing autonomous maneuvers while the pilot just stands there.

   The problem remains, as Igor correctly points out, and taking as a given that autopilots are going to be banned - *how* are you going to ban them? One way certain to work is to require mechanical connections. It's a crude response, it unnecessarily disallows your fly-by-wire system that most of us think is OK, but it certainly bans autopilots effectively.

  As previously, if you don't want your fly-by-wire system to get banned it would be worth your while to put efforts towards a rule that permits yours, and still clearly prohibits autopilots. I think that is more important to your cause than developing the fly-by-wire system further. I have been thinking about it for ~15 years now, and I still can't come up with anything better than "mechanical connections" but unless you do, your system is going to get banned, too.

   Brett

Offline Kim Doherty

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Re: Why Fly-By-Wire exists
« Reply #10 on: August 29, 2013, 09:00:09 PM »

   What everybody is concerned about is autopilots. As I mentioned when this first came up, *autopilots are going to be banned*. I don't think you are likely to disagree with the point we don't want an autopilot doing autonomous maneuvers while the pilot just stands there.

   The problem remains, as Igor correctly points out, and taking as a given that autopilots are going to be banned - *how* are you going to ban them?

  I have been thinking about it for ~15 years now, and I still can't come up with anything better than "mechanical connections" but unless you do, your system is going to get banned, too.

   Brett

Brett,

There is no question, without reservation that I would not support any autonomous flight path control capability.

Maybe the first step is to define exactly how far we are prepared to go in the non mechanical linkage direction. For me, the only part remaining would be to experiment with yaw control since it is available through a mechanical linkage. So primary flight surface control without the aid of sensors and receiving primary input via a bell crank that is attached to the lines, yaw control through a gyro or other sensor and motor control without limits.

What I have trouble understanding is that you and all members of the AMA have for decades taken a person at their word that they were the builder of their own model. If they declare it so then it is. Why should this be any different?

As far as testing to determine if the model is using flight path control, simply tape the lead outs together, power the model up (without a prop) and move the nose in three dimensions. If the controls move it is using flight path control.

If the model passes technical inspection but is suspected of transgressing the rules I suggest that someone file a protest and a competent flier be appointed to fly the model and render an opinion. I have no problem letting any competent flier fly my model. If that is the price of admission then so be it.

I do not see the FAI rule being changed any time soon.


Kim.
 

Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #11 on: August 29, 2013, 09:35:19 PM »
What I have trouble understanding is that you and all members of the AMA have for decades taken a person at their word that they were the builder of their own model. If they declare it so then it is. Why should this be any different

  Probably shouldn't be, but I can tell you there are people lining up to write that proposal. It was rejected before, maybe it will again, but I wouldn't count on it.

   You have a point about trusting the competitors. But, BOM is actually a rule, and you have to lie to break it.

    With this, there is no rule at all right now, so no rule to break, an autopilot is absolutely permitted as it stands today.  I presume that you would suggest "electronic coupling of the flight surfaces shall limited to causing the surfaces to move in proportion to the bellcrank deflection" or some such. That might be a viable rules proposal. THEN, your theory about trusting the people to not cheat would be one possible outcome.

    But you need to make the argument and convince people it is workable. Starting by stating that people are trying to conspire against you is not likely to bring people to you point of view.

    Brett
   

Offline MikeCoulombe

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Re: Why Fly-By-Wire exists
« Reply #12 on: August 30, 2013, 08:11:20 PM »
Ok so debate aside, Kims system is not cheating, Brett makes some good points also.
What constitutes a "auto pilot"? Is it the part of the system that "Knows" when the airplane is not level and autonomously corrects it? I don't think that any system could sense and correct a non level flight situation, sure level flight is achieved at around 4-6 feet, but what happens when the model is at 45 degrees up from center at the top of a simple loop? You certainly don't want the system to correct non level flight at the top of the loop.
Is the auto pilot the part that adds a little more or less out board flap in a maneuver? Is it the part that adds a little more or less throttle?
Is it the part of the system that has a little slop in the flap horn (I've tried this) to maybe soften the control at neutral in theory to help eliminate hunting.
How do you "prove" that you have no auto pilot, how do you "test" a system to prove it is not autonomous?
Brett, if there is a rule banning autonomous control systems, then yes it would be like the "bom" rule.
Thoughts?


Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #13 on: August 30, 2013, 09:30:48 PM »
How do you "prove" that you have no auto pilot, how do you "test" a system to prove it is not autonomous?
Brett, if there is a rule banning autonomous control systems, then yes it would be like the "bom" rule.
Thoughts?

  Kim's test (hold the leadouts and move the airplane around and see if it reacts) sounds OK. Of course you could have the timer enable the system at motor start.

    I don't think, the way the stars are aligning, that it will be like BOM, because I think the overwhelming likelihood is that anything but mechanical connections are going to get disallowed. Not because of any sort of vendetta, but because no one can think of anything better that is sure to work. I don't necessarily advocate that, but that's what I expect to happen.

    BTW, what we mean by "autopilot" could mean almost anything from weak stability enhancement, to full-on automatic flight. Typically we use it to make the control input a "rate command" system where the bellcrank angle represents an target angular rate, which is then achieved by a combination of feedback sensors. I am not entirely convinced that this is a bad thing, but I bet I am in the minority. It's a very small step from there, to generating the rate commands to perform a perfect maneuver automatically when triggered. Everybody agrees that this is not acceptable.

     Brett

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Re: Why Fly-By-Wire exists
« Reply #14 on: August 31, 2013, 02:48:04 AM »
I think everyone is making a mountain out of a mole hill. It is a huge jump "HUGE"from this to any type of pre programmed flight system. The only thing I would be concerned with is stabilizing Gyro's which is doable from here.
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Re: Why Fly-By-Wire exists
« Reply #15 on: August 31, 2013, 06:04:18 AM »
Berkeley had a model back in the 1940's or so that had mechanical flight stabilization. If you are going to have a rule to eliminate electronic stabilization then you also need to include mechanical stabilization as well. It had a pendulum to augment the user control inputs. It was the Berkeley "Bug" and the control system was called "Autotrol."

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Offline MikeCoulombe

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Re: Why Fly-By-Wire exists
« Reply #16 on: August 31, 2013, 12:50:36 PM »
I think the real issue here is the fact that some would move to suppress innovation and creativity in a hobby that should welcome  and embrace new technologies.
Stunt has always been about innovation.

If we move to stifle the exploration of new innovations and technologies, then we might as well sign stunts death certificate now!

Go ahead, propose your little witch hunt rules that suppress free and independent thought.

I can hardly wait to see you prove your control system is all "mechanical" when it is enclosed in the airframe!


Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #17 on: August 31, 2013, 04:44:44 PM »
I think everyone is making a mountain out of a mole hill. It is a huge jump "HUGE"from this to any type of pre programmed flight system.

  No, it isn't. It's actually quite simple once you have a processor in the loop, then it's just a matter of software. Plenty of people already know how to do it.

    Brett

Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #18 on: August 31, 2013, 04:46:21 PM »

Go ahead, propose your little witch hunt rules that suppress free and independent thought.


   That's not helpful, nor likely to win any converts to your position.

    Brett

Offline MikeCoulombe

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Re: Why Fly-By-Wire exists
« Reply #19 on: August 31, 2013, 06:16:13 PM »

Go ahead, propose your little witch hunt rules that suppress free and independent thought.



You are right Brett I won't win any converts to my opinion with such volatile rants.
I apologize to the forum and retract the statement.
Sorry.

I just feel that the all out ban on anything but direct mechanical control will jeopardize the future of stunt.
We are presenting our passion for precision aerobatics to a new generation, a digital generation who I believe want to be able to endlessly "tweak" things to make them do what they want them to do.
I'm sure that many new flyers would embrace the technology.



Offline Tim Wescott

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Re: Why Fly-By-Wire exists
« Reply #20 on: August 31, 2013, 06:44:37 PM »
  No, it isn't. It's actually quite simple once you have a processor in the loop, then it's just a matter of software. Plenty of people already know how to do it.

That, I think, is a stretch.  To do an autopilot that could beat one of the world-class guys would take a lot more than just the ability to string a few lines of code together.
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Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #21 on: August 31, 2013, 07:48:12 PM »
That, I think, is a stretch.  To do an autopilot that could beat one of the world-class guys would take a lot more than just the ability to string a few lines of code together.

  Well, you would certainly have to do some math, but it's simple enough.
 
    Brett

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Re: Why Fly-By-Wire exists
« Reply #22 on: August 31, 2013, 09:36:29 PM »
Well I think it would take more than just a processor in the loop. You need appropriate sensors to detect altitude, speed, and directions. However there are flight computers for quadcopters and such with the necessary hardware, and at reasonable cost.

-Chris

Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #23 on: August 31, 2013, 10:09:37 PM »
Well I think it would take more than just a processor in the loop. You need appropriate sensors to detect altitude, speed, and directions. However there are flight computers for quadcopters and such with the necessary hardware, and at reasonable cost.

  Absolutely! To first approximation, you only need gyros. Make the deflection of the bellcrank represent the commanded rate, command the servo to a value proportional to the bellcrank deflection, and then add to that the difference between the rate command and the gyro rate. If the rate deviates from the desired rate, the gyro corrects it. That's a reasonable, simple autopilot design, that would make the airplane much easier to fly because you no longer have to pay much attention to whether or not your control input did what you expected.

    Now, replace the bellcrank input to this system with something that, when triggered, generates a fixed pitch rate command, and integrates it until you get to 90 "steradian degrees", then sets the commanded rate back to zero. Trigger with "hard-over" bellcrank position, below hard-over, it works like it did in the previous example. Now you have a perfectly programmed square corner, repeat 4 times, perfect square, correct for drift by changing trigger points.

   That could be done with a very minimal processor contained in the postulated "black box".

   If you want it better, then start adding accelerometers to create a "strapdown" inertial reference, then you won't have to correct for drift due to wind any more and can program complete maneuvers.

    All this sort of processing is quite simple and people have been designing systems like this for more than 50 years for satellite control and rocket guidance. The Atlas missile guidance system autopilot worked pretty much exactly like the simple system above, the guidance law output was a body angular rate command that was implemented with a feed-forward (the bellcrank angle generating the control deflection) and gyro rate feedback to correct errors in the open-loop feedforward. The guidance was external on that one, based on riding radar beams early on.  Which brings up the other half of this that no one has mentioned - our  soon-to-be-permitted 2.4 ghz radio links. Which could provide the external reference to make the thing entirely automatic.

   It would take some work but all of this is well within the state of the art.

    Brett

Offline MikeCoulombe

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Re: Why Fly-By-Wire exists
« Reply #24 on: September 01, 2013, 08:49:24 AM »
So the tech exists, banning it won't make it go away.

Personally I can hardly wait for a fully programmable over the counter control system.

Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #25 on: September 01, 2013, 01:12:38 PM »
So the tech exists, banning it won't make it go away.

Personally I can hardly wait for a fully programmable over the counter control system.

   Why? What is the point of doing that, aside from showing you can do it? If you buy it turn-key, you are showing only that someone else can do it. But no one cares what you sport-fly with, enjoy it however you wish to. Contest rules are not going to matter for sport-fliers.

   Banning it certainly will make it not show up in a contest environment, which is where the problem is. Virtually no one wants an autopilot to be legal, Kim included, because it fundamentally alters the event. Autopilots will be made illegal, period.

Given that, if it requires banning fly-by-wire systems unnecessarily (because we can't come up with a better way to ban autopilots than "mechanical connections")  that will be what happens.

    Brett

Offline MikeCoulombe

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Re: Why Fly-By-Wire exists
« Reply #26 on: September 01, 2013, 02:26:47 PM »
I didn't say "autopilot" I said "control system".
I don't want an autopilot any more than you do.
I think we need to define "where" exactly digital control ends and autopilot begins.
Some may say that accelerometer based throttle control is autopilot.
Some may say that a mechanical device to change you rudder in turns is autopilot.

Offline Avaiojet

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Re: Why Fly-By-Wire exists
« Reply #27 on: September 01, 2013, 06:09:16 PM »
Kim,

I just gave you a + to get you out of that -1 hole you were in. A hole I know all to well.  LL~ LL~ LL~

I was at -375 once, remarkable but true! Tell ya, it's dark and lonely down there.  Really dark and really lonely. You can't dig your way out of a -375.

Model airplanes, will they ever be X-rayed? Scrapings from under the nails to test for BOM?

Anyway, I have interest in anything electric, and expect to enter that "cave" shortly. Shortly, well, hopefully before I die. Got some engines to sell first.

I like and have interest in what you're up to. Kudos!  H^^

That servo thing operating the control surfaces. I know it quite well from R/C pattern and it works. Not sure for CL, but please, you will keep us informed.

I'm always late in Threads because I don't like to read. So, at first, I thought you eliminated one of the handle lines. Hey! That thought worked for me.  n~

In all honesty, when I saw your magnetic bellcrank, I was at first disappointed. I'm over that now and, two lines or not, I'm still interested in your endeavors, .

Can you get it down to one line, one servo and a "joy" stick?

Hey! I got your back with that +.

Keep up the good work!

Charles
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Re: Why Fly-By-Wire exists
« Reply #28 on: September 02, 2013, 07:06:38 AM »
There are some nice conveniences available for a fly-by-wire system, I think.

If you want a removable wing on your model, it is a lot simpler to do if there are no mechanical control linkages. Just an electrical connector and a few nylon screws to hold the wing on.

Plus if you want to play with control ratios flaps/elevator, you just modify program a bit. Also if you want a response curve on your elevator or flaps that is not linear (say exponential or logarithmic) it is easily accomplished in software. No fancy machining or mechanical design.

-Chris

Offline MikeCoulombe

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Re: Why Fly-By-Wire exists
« Reply #29 on: September 02, 2013, 09:26:51 AM »
There are some nice conveniences available for a fly-by-wire system, I think.

If you want a removable wing on your model, it is a lot simpler to do if there are no mechanical control linkages. Just an electrical connector and a few nylon screws to hold the wing on.

Plus if you want to play with control ratios flaps/elevator, you just modify program a bit. Also if you want a response curve on your elevator or flaps that is not linear (say exponential or logarithmic) it is easily accomplished in software. No fancy machining or mechanical design.

-Chris

Chris, You Nailed It Exactly! #^

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Re: Why Fly-By-Wire exists
« Reply #30 on: September 03, 2013, 05:05:45 AM »
I have been playing around with the line spacing at my handle to get the response that I liked from a model that I just started flying. With the fly by wire system you probably can just change some system settings to get the control sensitivity that you like. Also if you move the position of the lines to get the same sensitivity inside and outside turns, you can do that electronically as well. That is pretty neat, too!

-Chris

Offline Bob Hunt

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Re: Why Fly-By-Wire exists
« Reply #31 on: September 03, 2013, 05:27:00 AM »
As for moving the thread - the original thread had nothing to do with electric power for models.  It had to do with control systems ...

as does this one.


Hi Kim:

First off, please do not blame Dean Pappas for moving this thread from the All AMPed Up section; I did it. As Mike Anderson so correctly posted, this is not a subject that is about electric models. It's about control systems, and, as the posts here have shown, it is a subject ripe for debate.

If you were to look at the one post I did make about your system on the All AMPed Up section, you would see that I was one of the few who not only defended you and your system, but also applauded you for it.

I see forums as a vehicle to help those who need questions answered and exchange ideas. I feel that subjects that spur strong debate should have a section where debates can take place without confusing or scaring off newcomers who only want their basic questions answered. If they see too much arguing between experts, they just might pack up and leave. That we cannot afford; we need all the newcomers we can get.

I feel that this is an important subject and one that will be the test case for future electronic advances that might improve our mode of flying. Sparky did the exact right thing in forming a new forum topic for it.

Kim, I'm not your enemy. I see and understand your path, and highly applaud it. It's just not something that needs to be, or should be, part of the electric propulsion discussion. You should have originally posted this on the Open Forum. While I don't consider it rude that you didn't do that, I was disappointed that you chose to inject another highly argumentative subject into a forum that deals with an already sensitive subject to many.

Bob Hunt

Online Howard Rush

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Re: Why Fly-By-Wire exists
« Reply #32 on: September 03, 2013, 06:05:53 AM »
To do an autopilot that could beat one of the world-class guys would take a lot more than just the ability to string a few lines of code together.

Yes, it would.  It would take MEMS sensors, now readily available, and the specialized knowledge of control systems, with its kinda esoteric math.  Some of us have the latter, including Brett, me, Igor, and Tim.  I think most of us can see what's coming.
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Re: Why Fly-By-Wire exists
« Reply #33 on: September 03, 2013, 06:24:09 AM »
I didn't say "autopilot" I said "control system".
I don't want an autopilot any more than you do.

None of us can look at somebody else's electronic control system and tell whether it's a straight open-loop control, augmented control, or an autopilot.  That's the problem. The only way to draw the line is to forbid electronics in the pitch axis.

Some may say that accelerometer based throttle control is autopilot.

It's an autothrottle.  That's what it's known as in the industry, anyhow.  Now you have to have one to place in the world or European championships or to win the US Nats. The effect of automation in pitch would be much more than for propulsion. 

Some may say that a mechanical device to change you rudder in turns is autopilot.

Obviously not.  Writing the rule to ban electronics would allow such a linkage.  It's a simple distinction.  Using a yaw rate feedback to control rudder, as has been done since the early days of swept-wing airplanes, and as Igor has done with a stunt plane, is a different matter.  My people would call that a stability augmentation system.  Whether to allow a SAS in yaw and roll is a separate subject than allowing electronics in pitch.  I would recommend banning electronics from all aerodynamic control surfaces.
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Offline pmackenzie

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Re: Why Fly-By-Wire exists
« Reply #34 on: September 03, 2013, 07:26:52 PM »
None of us can look at somebody else's electronic control system and tell whether it's a straight open-loop control, augmented control, or an autopilot.  That's the problem. The only way to draw the line is to forbid electronics in the pitch axis.

That would be one way to do it.

Another way would be to simply say the system must be open-loop, and the contestant says that it complies.
You know, take people at their word.
Works in F3A and F3P where stability augmentation is not allowed.

And it would be easy to see what devices are on a PCB. If there is only a microcontroller and no accelerometers or gyros then it is pretty clear that the system is open loop.

If one's goal was to cheat then even with normal bellcranks and solid pushrods systems could be devised that could augment stability.
Look no further than cars with stability control to see how it can be done.

I can't quite understand the desire by some (a few?) to kill this before it has even flown in a contest.
Plenty of time to formulate rules if things get to the point where electronic systems show some sort of clear and unfair advantage.
Till then it seems very reactionary.

Pat MacKenzie

P.S. Congratulations on making the US team.
« Last Edit: September 03, 2013, 07:58:59 PM by pmackenzie »
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Re: Why Fly-By-Wire exists
« Reply #35 on: September 04, 2013, 12:55:43 AM »
Pat, that what you say is not enough. You probably did not read argumentation while we spoke about it in rules working group. We also do not want preprogrammed open loop clock work, not only feed back systems. We cannot say "it is compliant" because we even cannot define what is and what is not allowed, because there is not clear line between "controlled by pilot" and "autopilot". This what you wrote is clear example. We not need to see only rocket technics with gyros and accelerometers. I can say for myself, that on latest ECh I got marks between 8 and 9 for almost all figures. But I got twice (from 7 official flights) mark 6.8 for not so well done 60 degrees turn to triangle and hourglass (it was not so bad, but some judges simply want cut top guys for even small mistake to make clearer differences). I wrote it somewher in another thread and I posted also my score sheet, it is well visible. So for me it will be very very helpful a small function which will trigger preprogrammed 60 degrees turn when it sees that I do first corner of triangle or hourglass. This will give me may be 5 or 10 safe points what will make me good sleeping front of Richie and Alex. This is in my eyes clearly unfair, but I can still say that I send my pilot commands by lines to model. And even IF we can find clear wording to disable this then we cannot find way to inspect it. Because it is PROGRAMATICAL solution. You cannot see it on PCB, and you cannot check it on ground.

And why we want it stop as soon as possible? You know how much effort it costs you ... so that is reason, those who can do it also will must develop it if they want to stay competitive and those who cannot, will think if they want continue. We simply do not want to kill event with solution undoable by average pilot or builder.

Pat, again and again ... this is about stunt rules, nothing else. When I saw it first time, I did not wrote to Kim (or anyone else) that he is "bad guy". I wrote to working group and triggered speech about it. Result is that the best way is to allow only mechanical way from pilot to any control surface. And why? it is pretty simple and practical - because for passed 50 years no one invented useful autopilot. So we believe no one will do it also in next 50 years, while only existence of FBW opens in all heads how to use gyros, accelerometers and other tricks. I know you spent lot of time with FBW and you do not want to throw it to trash, but you knew long time that it will have strong opposition, that is why I opened it immediatelly I saw it first time. It is not plenty of time to formulate rules, as I see it is already too late.

But tomake it clear and I wrote it already, I do not see problem with FBW itself, if FBW will allow newcomers to start safely as Kim wrote, it will be very good, so simply do it, I will welcome it in area where it helps, I simply do not want to push stunt to programmers event for 5 people of planet.

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Re: Why Fly-By-Wire exists
« Reply #36 on: September 04, 2013, 04:22:19 AM »
Something like a preprogrammed 60 degree turn will require massive amount of feedback.
I doubt it is even possible without  RF connection between a ground based computer that employs multiple cameras to track the model combined with a precise mathematical model of the models flight.

The latter is how the many videos you see of quadcopters dancing, bouncing balls back and forth or playing music have been done. None of them are autonomous.
Until you see someone setting up a half dozen video cameras, some of them 60 feet in the air, and parking a mini van full of equipment next to the circle you don't have anything to fear about being beaten due to prep-rogrammed 60 degree turns.

Without all that "tech" the only thing you can do is simply preset the amount of deflection and hold it for a certain period of time.
The end result will be about as good as a blindfolded pilot would be capable of accomplishing.

In any case, again looking to other events pre-programmed sequences are also not allowed by rules in F3A.
So we are once again back at taking people at their word.

I did see some of the working group discussion, and in the end there was no change to the rules that precluded a FBW system.
What they ended up doing was allowing RF control of non primary systems, so rather than restricting technology the actually expanded it and defined where it was permissible.

Quote
1.3.2 Category F2 - Control Line Circular Flight
a) Control Line Circular Flight is flight during which all control is accomplished via physical connection
to the pilot through one or more inextensible wires or cables directly connected to the model aircraft.
The control wires or cables must be attached to a hand held device (control handle). Automatic flight
path control and/or automatic manoeuvring are not permitted.
b) Powertrain control may be accomplished by the pilot via the wires or cables or by an onboard selfcontained,
automatic process.
c.) For permanent shutdown of the engine(s), any device or system is permitted including the use of 2.4
GHz Spread Spectrum technology legal for use in the country of competition. The competitor will
determine the suitability for use of the chosen system.
Any such device or system:
1) must be operated only by the pilot, and
2) must not affect any other model.

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Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #37 on: September 04, 2013, 02:03:04 PM »
Without all that "tech" the only thing you can do is simply preset the amount of deflection and hold it for a certain period of time.
The end result will be about as good as a blindfolded pilot would be capable of accomplishing.

   No. If I take a reasonably accurate (over the period of 200 msec) gyro and integrate the output, I can make it do a nearly perfect corner. You couldn't do a whole flight that way, but the effect of drift would be negligible and the scale factor error could be calibrated out. We do it all the time. It would be open-loop, but dead-nuts repeatable. You could get it right in a few flights.

   With enough radio links, you can do what you can do with multiple cameras. A completely passive tracking array could be generated using 3 transmitters and a properly-designed antenna and tracking system in the airplane. It could be as accurate as half a wavelength, which if I did my guzzintas right, is about 2 3/8". Easy - no, but certainly possible with sufficient trickery. Since there will be nothing preventing a 2-way link, all the processing could be on the ground.

   Of course, I also know how to jam such a system, so if you see me with a 5Kw spark gap transmitter, that's why.

    Brett

 

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Re: Why Fly-By-Wire exists
« Reply #38 on: September 04, 2013, 06:06:24 PM »
Well I have to say Kim's various threads about Fly by Wire has been a very interesting read and sorry for going "Off Topic" but.....

I'm still not convinced that it's even possible to put together a package that would respond to prevailing conditions even close to that of the handle waving capabilities of <Insert your favourite Stunt God here>. But I'm not saying never, and I guess future proofing is what establishing the rules are all about.

I was wondering given the assertions of various people that this could be done now if a better use of the perceived auto pilot technology would be to develop it's use it as a scoring device. If it really is possible to get the perfect pattern with an auto pilot then presumably it is even easier to remove the complication of actually moving the control surfaces and just log the flightpath? Then you could just download the flight and let software compare its path with the manoeuvres as they should be flown and score accordingly.

I'm not trying to do the judges out of a job as it's a thankless task but Igor commented that sometimes he feels that as a top pilot he gets hit harder than some if he flies a bad manoeuvre and others have suggested the feeling of a "Halo Factor" or discrepancies between different judges scores for the same manoeuvre.

One of the issues with F2B as opposed to other Cl disciplines has always been that a flight could be considered open to a certain amount of interpretation rather than an judged by a measurable baseline such as a stopwatch or streamer cuts etc.

I'm not having a dig at judges, far from it but if an application which just scores based in a known baseline was possible it could be a great "leveller" at Nats and World Champs for example.

I would be all for it.

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Re: Why Fly-By-Wire exists
« Reply #39 on: September 04, 2013, 06:45:58 PM »
   No. If I take a reasonably accurate (over the period of 200 msec) gyro and integrate the output, I can make it do a nearly perfect corner. You couldn't do a whole flight that way, but the effect of drift would be negligible and the scale factor error could be calibrated out. We do it all the time. It would be open-loop, but dead-nuts repeatable. You could get it right in a few flights.

   With enough radio links, you can do what you can do with multiple cameras. A completely passive tracking array could be generated using 3 transmitters and a properly-designed antenna and tracking system in the airplane. It could be as accurate as half a wavelength, which if I did my guzzintas right, is about 2 3/8". Easy - no, but certainly possible with sufficient trickery. Since there will be nothing preventing a 2-way link, all the processing could be on the ground.

   Of course, I also know how to jam such a system, so if you see me with a 5Kw spark gap transmitter, that's why.

    Brett

 

You are making my point, thank you. :)
Gyros or radio links = tech.
Already prohibited under the rules and not a part of our system.

My point was that a FBW system as allowed under the current rules incapable of doing a pre-programmed 60 degree corner.
Or maintaining level flight, or any of the other things some seem to fear.

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Offline Igor Burger

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Re: Why Fly-By-Wire exists
« Reply #40 on: September 05, 2013, 12:46:12 AM »
I'm not trying to do the judges out of a job as it's a thankless task but Igor commented that sometimes he feels that as a top pilot he gets hit harder than some if he flies a bad manoeuvre and others have suggested the feeling of a "Halo Factor" or discrepancies between different judges scores for the same manoeuvre.

John, I did not want to comment judges work, pilot never see his mistakes well, in reality I saw it and others (well Tania :-P ) also told me that I did not do it well. I wanted to tell that such mistake can cost lot and judges are not forgiving and I did it twice on the same place. The point is that such a system not needs to make pattern instead of me, it is plenty to give little advantage which can be enought to securely win or move forward. Differences on top places were small this time. And if you look to results of your NATs you will see it also. Therefore such a simple trick like preprogramed one small invisibke point in whole program can easily change result. We not need rocket technic.

And speaking about computer judge is completaly something else. It need RECOGNIZING ... that is relatively difficult, but theoretically still doable, but knowing the path of the model, I cannot imagine how to convert observed difference between real path to theoretically proper in terms defined by rules ... and then even worse, how to deduct mark. Making autopilot from this point of view is trivial job :- ))))

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Re: Why Fly-By-Wire exists
« Reply #41 on: September 05, 2013, 01:03:12 AM »
My point was that a FBW system as allowed under the current rules incapable of doing a pre-programmed 60 degree corner.
Or maintaining level flight, or any of the other things some seem to fear.

Seems to me that you are really trying to keep open doors for such things. I am surprised you are trying to say something is not doable without trying I wold never say such thing, because I saw "undoable" things many times in my life.

Such preprogrammed maneuvers are successfully done in R/C world may be 20 or 30 years ago. By simple timers. I saw perfect and repetitive rolls always finishing in perfect level position with F3A airplane and timer executed by simple button. So it is obviously doable and replacing muscle memory be electronic device does not have space here in my eyes.

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Re: Why Fly-By-Wire exists
« Reply #42 on: September 05, 2013, 11:20:31 AM »
Berkeley had a model back in the 1940's or so that had mechanical flight stabilization. If you are going to have a rule to eliminate electronic stabilization then you also need to include mechanical stabilization as well. It had a pendulum to augment the user control inputs. It was the Berkeley "Bug" and the control system was called "Autotrol."

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And it was bogus.  
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Offline Brett Buck

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Re: Why Fly-By-Wire exists
« Reply #43 on: September 05, 2013, 12:26:01 PM »
You are making my point, thank you. :)
Gyros or radio links = tech.
Already prohibited under the rules and not a part of our system.

My point was that a FBW system as allowed under the current rules incapable of doing a pre-programmed 60 degree corner.
Or maintaining level flight, or any of the other things some seem to fear.

  Agreed. The problem is that those very same rules DO permit a pre-programmed corner, and that is very likely to get fixed in the very near future. If you don't want FBW to get caught up in that, then you need to come up with a reasonable rule that permits one and not the other. Personally, saying it isn't an autopilot is probably OK with me but that's not going to be good enough for everyone else, you are going to have to prove it somehow.

   Brett

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Re: Why Fly-By-Wire exists
« Reply #44 on: September 05, 2013, 12:40:24 PM »
And it was bogus.  

Do you mean "bogus" as in it didn't work worth a damn or "bogus" as in it against the rules?

I have to dig out the plans for it again...

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Re: Why Fly-By-Wire exists
« Reply #45 on: September 05, 2013, 12:54:18 PM »
Yes, it would.  It would take MEMS sensors, now readily available, and the specialized knowledge of control systems, with its kinda esoteric math.  Some of us have the latter, including Brett, me, Igor, and Tim.  I think most of us can see what's coming.

I'm not sure that the current crop of consumer-grade, lightweight MEMS sensors is up to the task of doing an entire pattern autonomously -- but that's mostly because there's very little information available to the Kalman filter about the airplane altitude until it pops into the first corner of the wingover.  After that, I'm pretty sure you could just attach the handle to a speed pole, then sit down and enjoy the show.

With GPS augmentation it would be a no-brainer, in a corporate-funded half a man-year of effort sort of way.  I've got about 50% of the code for that sitting on my computer, left over from a vehicle tracking project that included some generous terms about what technology I could keep for my own use.  Attach handle to speed pole, push "start" button, sit back...

And Howard -- I don't think the math is kinda esoteric.
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Re: Why Fly-By-Wire exists
« Reply #46 on: September 05, 2013, 01:51:33 PM »
I'm not sure that the current crop of consumer-grade, lightweight MEMS sensors is up to the task of doing an entire pattern autonomously -- but that's mostly because there's very little information available to the Kalman filter about the airplane altitude until it pops into the first corner of the wingover.  After that, I'm pretty sure you could just attach the handle to a speed pole, then sit down and enjoy the show.

With GPS augmentation it would be a no-brainer, in a corporate-funded half a man-year of effort sort of way.  I've got about 50% of the code for that sitting on my computer, left over from a vehicle tracking project that included some generous terms about what technology I could keep for my own use.  Attach handle to speed pole, push "start" button, sit back...

And Howard -- I don't think the math is kinda esoteric.

   You aren't going to do a full pattern on inertial guidance with the current MEMs types that would fit in an airplane without an external observer of some sort. the drift and scale factor with 360-degree-per-second maneuver over 6 minutes. And I might suggest you don't want a Kalman filter to incorporate the observers, either, or at least I have seen plenty of cases where the Kalman filters were not optimal in these DOF-constrained cases.

  But overall, the notion that it couldn't be done and therefore there's no reason for concern is clearly not valid, even assisting in a few spots could make all the difference in the world, per Igor's example.

    Brett

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Re: Why Fly-By-Wire exists
« Reply #47 on: September 05, 2013, 02:29:18 PM »
   You aren't going to do a full pattern on inertial guidance with the current MEMs types that would fit in an airplane without an external observer of some sort. the drift and scale factor with 360-degree-per-second maneuver over 6 minutes.

I've started up a new thread for this:

http://stunthanger.com/smf/index.php?topic=32691.0
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