[simpits-tech] Motion...-FAO Roy Coates
simpits-tech@simpits.org
simpits-tech@simpits.org
Wed, 2 Apr 2003 14:56:10 +0100 (BST)
Roy,
Try Cambridge University Press, thats where I got my copy from a couple of years ago.
Darren
> from: Gordan Sikic <gordan.s@mail.inet.hr>
> date: Mon, 20 Jan 2003 09:16:46
> 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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