>At 07:50 PM 10/28/99 , Engstrom wrote:
>>>> [ I wrote g_uasge = max(cur)/max(peak); ]
>
>>> Ignoring the transition component, you'd want something like:
>>>
>>> g_usage = sqrt((cur_lat/peak_lat)^2 + (cur_accel/peak_accel)^2)
>>>
>>Now, usage at any point in the run is calculated as the highest of three
>>numbers.
>> 1) Total G percentage - this number is the distance from the
>> origin (or center of the friction circle) of the total Gs that
>> the car is currently pulling divided by the distance from
>> the origin of the edge of the friction circle that touches
>> a line that runs from the origin through the total G point
>> that the car is currently pulling.
>
>Okay. I think the math for this would be the g_usage I gave above,
>where you use the appropriate friction circle for your speed.
In my original post on this, I didn't mean for my "max" function to be
taken literally in the mathematical sense, but just locgically in the
sense that GEEZ thinks you should be maximizing one of the three data
channels. While your math is close, it isn't exactly what you want. In
addition to quantizing for speed (the idea of a friction cylinder) you'd
also have to quantize for the vector angle for (at least) two reasons.
The first is that you can brake much harder than you can accelerate. If
you use your formula above, acceleration is always going to be some
fraction of peak usage as soon as you hit the brakes. The second is
that tires aren't linear in their ability to generate g's with respect
to the angle of the force.
A third consideration could be quantizing over time. Say the first half
of the course was wet or on a different surface. Clearly your absolute
g's are going to be different for differing conditions. I guess my
point is that Byron has probably put quite a bit more thought into
getting useful usage numbers than we can surmise on this list.
However, I still think GEEZ has a limitation by not looking at the rate
of change in acceleration, like it does for lat g's. You should not be
"penalized" for acceleration going through the center of the friction
circle (as you do in straight line braking.)
Todd
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