[simpits-tech] Motion...
Chris Brace
simpits-tech@simpits.org
Wed, 2 Apr 2003 22:03:37 +1200
If your really keen here is another link for you.
http://www.cadsoft.de/~kls/fltsim/
This project is very cool and uses some ingenious ideas. Cost is bugger
all, but sadly there has been little movement (pun intended) on it for a
while now.
I'd love to put one of these under my F16-something or other but in all
honestly good visuals and simple motion queueing would be a lot simpler
and just as effective.
I did a couple of hours flying in a full military sim a few years back.
It was an AirMacchi MB339, using a 3 screen colminated display with a
fixed (no motion) base. The feedback from the controls, the sounds
system and the visuals were enough to fool me. I actualy got vertigo
during a pop-up from ground level to 5000ft and rounding off the top. I
suddenly had to grab for the canopy bow because I felt like I was about
to fall over the top as I rounded out and pointed down to the ground
again. It was a very good lesson about visual being able to fool the
senses.
Chris.
-----Original Message-----
From: simpits-tech-admin@simpits.org
[mailto:simpits-tech-admin@simpits.org] On Behalf Of Gordan Sikic
Sent: Monday, 20 January 2003 10:17 p.m.
To: simpits-tech@simpits.org
Subject: Re: [simpits-tech] Motion...
Hi,
Joseph Fagner wrote:
>Think about this for a minute (granted I realize this is probably
>overly simplistic and the math is infinitely more complex): Most
>software out there has the 4 axis of data (not to be confused with the
>axis of evil) one might need for motion. Couldn't one just write some
>software to read this data and translate that to motion? The data to
>which I refer is (1) pitch and (2) roll (X and Y axis); via your
>artificial horizon instrument. (3) Yaw (Z axis), via your compass and
>(4) altitude via the altimeter.
>
>
It is not that simple.
You need angular rates as well as accelerations. Making motion platform
based on attitude of the AC would be waste, beleive me. Generally
speaking, with the motion platform one hopes to imitate (inertial)
accelerations that pilot feels. Simple example acceleration on the
runway during take-off. During that period pilot feels sustained
acceleration on his back. The sense of acceleration is imitated by
rotating the platform slightly backwards, so the weight of the "pilot"
generates the force on the back. That shift is sudden, and later the
platform is slowly returned to middle position. Thus, imitation of just
one linear acceleration is achieved completly different type of motion
(sudden rotation, followed by slow return to neutral position).
Other than this, you should think of something completly different:
Motion platfors are _very_ power hungry, you might easilly end up with
facility which draws couple of tens of KW of power.
Yet another problem is safety. Think of the following: it is very easy
to start the filre in the chitchen with electrical oven of just couple
KW (or even less), and here you are dealing with much more powerfull
equpment.
Yet yet additional problem are foundations, because something must
support complete construction, and take over complete forces and moments
generated by themoving platform.
There are many problems, but this doesn't mean that there is no
sollution :) If you really want to make motion platform, do read
apropriate chapter
in "flight simulation", book that is mentioned few days before. It is
excelent reading, but be warned that it does not provide us with
sollutions, but presents the problems in very concise way, and just
guides towards the solution. But in any way it is a "must have" book.
I've been reading it from the cover to cover and all over again many
times :)
Also check web for motion platforms where you will find some standards
you should achieve. one url is www.fokercntroll.com, and the other is
(if I recall correctly, I'm off line now) www.mug.com.
Personally I'll take following approach:
Generaly, visual system provides low frequency sensations, and use
motion (vibrations to be specific) for the high frequency sensations
(like tyrbulence, or vibrations, ...). This is not as good as well made
motion system coupled with nice visualisation, but it is _much_ better
than wrongly made motion platform, and in any case infintelly safer.
At the end one true story:
(I don't know the details, what kind of AC, how many degrees of freedom
in motion platform, nor how many pilots, ... :)
There was a project of evaluating different algorithms for driving
motion platform, and within the project many (profesional) pilots were
flying on the simulatior, every flight with different algorithm applied.
Needles to say that pilots didn't know which algorithm was to be applied
for any of the flights. After every try, they were asked to describe in
words how they felt, and to place a numerical mark. After the data were
analysed, it turned out that many pilots (more than few, anyway) said
that the best results were achieved with algorithm "number 5". The funny
thing was that algorithm in question corresponded to the case where the
motion platform didn'mtmove at all! Of course, pilots didn;t know that
fact while "flying"
>Jay
>
>-----Original Message-----
>From: simpits-tech-admin@simpits.org
>[mailto:simpits-tech-admin@simpits.org] On Behalf Of Roy Coates
>Sent: Friday, January 17, 2003 6:57 PM
>To: simpits-tech@simpits.org
>Subject: Re: [simpits-tech] Motion...
>
>On Fri, 17 Jan 2003, Brian West. wrote:
>
>
>
>> I have an excellent book published a few years back. The title
>>
>>
>is "
>
>
>>Flight Simulation" by J.M.Rolfe and K.J. Staples, published by
>>
>>
>Cambridge
>
>
>>University Press, ISBN 0-521-35751-9
>>It contains all the mathematical models etc needed plus a lot more.
>>
>>
>It's
>
>
>>almost certainly out of print but a search of secondhand book dealers
>>
>>
>might
>
>
>>turn up a copy.
>>If you can't find a copy come back to me . It's all a bit daunting
>>
>>
>though,
>
>
>>time and costwise for an individual.
>>
>>
>
>Thanks Brian - appreciate that. From what little research I've done so
>far it has become quite clear the there is no fixed rule to motion
>simulation,
>there seem to be several schools of thought on the topic.
>
>It also seems clear that each method has its own weaknesses. I'll
>continue searching!
>
>Roy.
>
>
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>
>
>
>
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