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Author Topic: Questions about Body Energy Coefficient, Bounce % and Pivot Energy  (Read 384 times)
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BillM
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« on: January 13, 2020, 04:08:14 PM »

Art

I've regressio n tested some of my previousl y published Augie vector processin g (AVP)
 simulatio ns (binomial distribut ion, walking man, and gravity escapemen ts) and they
 all work properly as they did with earlier versions of AVP.
 
I have been experimen ting with various object settings hoping to understan d the
effects of:
    Body Energy Coefficie nt (BOE){default .99}
    Bounce % {def .5}
    Pivot Energy {def .9999}

So far I've been guessing at the first two parameter s.

The attached are some of my experimen ts which I try to run ~30-40% speed:
   A_BounceT est-Coef .5.vcp   Body Energy Coefficie nt .5
   A_BounceT est-Coef .99.vcp  Body Enerby Coefficie nt .99
   
   Within each test I vary the bounce % from ~0 to 1 in steps of .1

   From observing the bouncing squares it would seem that  I should interpret
      Bounce % of .5  as 50% rather than .005
    
The BOE is probably related to the Bounce % but I'm not exactly certain.
      Is BOE the same thing as coefficie nt of restituti on (COR)?  Where a body during a collision
      loses (or doesn't absorb all) of the input kinetic energy so that a BOE of 1 would be
     no loss of energy and BOE of .6 would be absorbing 60% (or losing 40%).
     
I have not experimen ted too much with Pivot Energy to figure out the physical meaning of that parameter .

My goal is to create a simulatio n of the desktop toy sometimes referred to as Newton's cradle.
I'll publish my experimen t with that in a separate post.
 
Bill Michael

* A_BounceTest-Coef -.50.vcp (2710.95 KB - downloaded 26 times.)
* A_BounceTest-Coef- .99.vcp (3016.86 KB - downloaded 25 times.)
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ArtF
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« Reply #1 on: January 13, 2020, 08:53:42 PM »

Hi Bill:

     If I recall it all properly, the values will be hard to match up with reality meaningfu lly.
This is because as it was written it became apparent to me that the problem was that the
code relied on a quantum of time too much. If two bodies overlappe d during that quantum,
it wasn't possible for the normal equations to deal with energy. So I fudged the equations to
make the simulatio n run as close as I could to reality.
  If recoded, I think I would need more of a ray tracing intersect ion that controls the quantum
of time so it could be set to the instant of collision, then the normal kinematic equations
would have a better chance of meeting reality.

   To my knowledge your the only one who has ever come close to understan ding that
simulator to the point to do any real simulatio n. I too tried a newtons cradle, but that
mechanism kinda embodies what I mean. In a prefect world, as the first ball hits the
stack, the energy would transfer instantly to the end ball, but as the quantum is wrong,
the impact occurs inside the first ball and two energies are created, one to move the ball
back out of the first ball, and another added to the hit ball for transfer to the next.
  This repeats through all balls and each causes a loss due to the energy lost in pushing
the occluding ball away from the one it hit and went into. I fudged formulas to make it work
as well as I could at the time, but the time issue was the one that killed it.
  Collision detection even in 2d can really mess with your mind in terms of how
to compute it, the resultant energy transfer vectors  and the rationali zation of that energy
through the system. Moment of inertia wasn't part of the original kinematic equations
so I bodged it as much as I could to see if it could work.

    I killed that project as I was convinced it needed an entirely new framework to make it
work properly with inertial moment added to the system. Ill look to the code to see
if I see any rational explanati on for those terms, but dont get hopeful.. they kinda
work as they work sorta like a constant added to a physics equation because it makes
it work.. with hopes of figuring out the purpose of the constant afterward s.. Smiley

  I understan d the temptatio n though, there is a certain beauty in it when the
numbers work... its why a newtons cradle was one of the first things I tried
myself.. lol

Art


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BillM
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« Reply #2 on: January 14, 2020, 10:40:21 PM »

Art

Thanks for your reply.   I greatly appreciat e your efforts in the creation and continual improveme nts to Gearotics, Vexx, and Augie.

Now that I know that pivot energy and the Body Energy Coefficie nt are programme d to empirical ly get a reasonabl e simulatio n I've been devising a new
experimen t to get a feel of how these constants effect a simulatio n.  I'll publish the vcp of this experimen t tomorrow.

As you know from my past posts  I am intereste d in building simulatio ns of real systems. With gearotics my goal was to document the design of an actual
tower clock.  The chronomet er gearotics simulatio n was an attempt to create a simulatio n of Harrison's H4 chronomet er based upon the diagrams published in
the 1700's.

The Augie vector processor intrigued me because it allowed creations of linkages, springs and motors.  My walking man simulatio n was an attempt to
mimic the  Mr Machine toy of the 1960's.  The challenge was to mimic the motions of the leg, arm & head and actually have it move across the
simulatio n work space.  This Christmas I bought a reproduct ion of a Mr Machine and I may try to rebuild my walking man simulatio n with some of
the actual gearing.

Bill Michael

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ArtF
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« Reply #3 on: January 15, 2020, 12:04:05 PM »

Bill:

 Thx for the comments. I may one day code a proper simulator, I learned a lot on the subject
from making the vector processor in Auggie. Its nice to see it was used for proper amusement .

Art
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