Questions about Body Energy Coefficient, Bounce % and Pivot Energy

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BillM
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Questions about Body Energy Coefficient, Bounce % and Pivot Energy

Post by BillM »

Art

I've regression tested some of my previously published Augie vector processing (AVP)
simulations (binomial distribution, walking man, and gravity escapements) and they
all work properly as they did with earlier versions of AVP.

I have been experimenting with various object settings hoping to understand the
effects of:
    Body Energy Coefficient (BOE){default .99}
    Bounce % {def .5}
    Pivot Energy {def .9999}

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

The attached are some of my experiments which I try to run ~30-40% speed:
  A_BounceTest-Coef .5.vcp  Body Energy Coefficient .5
  A_BounceTest-Coef .99.vcp  Body Enerby Coefficient .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 coefficient of restitution (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 experimented too much with Pivot Energy to figure out the physical meaning of that parameter.

My goal is to create a simulation of the desktop toy sometimes referred to as Newton's cradle.
I'll publish my experiment with that in a separate post.
 
Bill Michael
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ArtF
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Re: Questions about Body Energy Coefficient, Bounce % and Pivot Energy

Post by ArtF »

Hi Bill:

    If I recall it all properly, the values will be hard to match up with reality meaningfully.
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 overlapped during that quantum,
it wasn't possible for the normal equations to deal with energy. So I fudged the equations to
make the simulation run as close as I could to reality.
  If recoded, I think I would need more of a ray tracing intersection 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 understanding that
simulator to the point to do any real simulation. 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 rationalization 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 explanation 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 afterwards.. :)

  I understand the temptation 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


BillM
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Location: Mystic CT

Re: Questions about Body Energy Coefficient, Bounce % and Pivot Energy

Post by BillM »

Art

Thanks for your reply.  I greatly appreciate your efforts in the creation and continual improvements to Gearotics, Vexx, and Augie.

Now that I know that pivot energy and the Body Energy Coefficient are programmed to empirically get a reasonable simulation I've been devising a new
experiment to get a feel of how these constants effect a simulation.  I'll publish the vcp of this experiment tomorrow.

As you know from my past posts  I am interested in building simulations of real systems. With gearotics my goal was to document the design of an actual
tower clock.  The chronometer gearotics simulation was an attempt to create a simulation of Harrison's H4 chronometer 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 simulation 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
simulation work space.  This Christmas I bought a reproduction of a Mr Machine and I may try to rebuild my walking man simulation with some of
the actual gearing.

Bill Michael

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Re: Questions about Body Energy Coefficient, Bounce % and Pivot Energy

Post by ArtF »

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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