paper: Drivetrain Acceleration Model

[Andrew Schreiber]

Originally Posted by Ether

I posted an update/correction to the C code:

- fixed an error in the English-to-SI conversion constants

- modified the accel function to better reflect the relationship between friction and rolling resistance

- added total drive motor amps to output

Dangit man, I just finished converting to coffeescript and started putting a front end on it! Mind posting your diffs?

http://bl.ocks.org/schreiaj/raw/6604...a78a8c98eda1b/ It's still missing the axis so it's kinda useless to get numbers out of but I'll post the updated version tonight once I get the axis un-inverted.

Current coffeescript port available at https://gist.github.com/schreiaj/660...a78a8c98eda1b/

[Ether]

Originally Posted by Andrew Schreiber

Mind posting your diffs?

There's a CSdiff report in the posted ZIP file that contains the revised C code :-)

[Andrew Schreiber]

Originally Posted by Ether

There's a CSdiff report in the posted ZIP file that contains the revised C code :-)

Thanks, I'll get those integrated sometime in the near future.

[Ether]

Originally Posted by Andrew Schreiber

Thanks, I'll get those integrated sometime in the near future.

I've got visitors coming over in 15 minutes.

Later this evening I'll strip out all the non-functional changes and give you a report of the minimum changes needed.

It's not a lot, once I get rid of the non-functional changes.

[Ether]

Originally Posted by Andrew Schreiber

http://bl.ocks.org/schreiaj/raw/6604...a78a8c98eda1b/... I'll post the updated version tonight...

Thanks for doing this. I'm hoping your user-friendly interface will generate more interest and technical discussion, and maybe even inspire teams to conduct tests and make their data available.

[Andrew Schreiber]

Originally Posted by Ether

Thanks for doing this. I'm hoping your user-friendly interface will generate more interest and technical discussion, and maybe even inspire teams to conduct tests and make their data available.

Here's the updated version (haven't put your code changes in yet) but I did make it a little easier to read.

http://bl.ocks.org/schreiaj/raw/6604...06fc207f7a970/

[IKE]

Thanks for putting this together.

I put together this "Drag Estimator" for my HS supermileage team years ago. It is based off of the Empirical rolling resistance and wind resistance test given in the Bosch automotive handbook.

http://www.epulaski.k12.in.us/tech/s...ign/design.htm

For rolling resistance, this gives a constant coefficient and a v^2 coefficient.

[Ether]

Originally Posted by IKE

For rolling resistance, this gives a constant coefficient and a v^2 coefficient.

I'm glad you brought this up.

I structured the code to make it very simple to change the rolling resistance model if you want to. It takes only 2 keystrokes to change the rolling resistance model from

L = Kro+Krv*V; (line #68 in the 9/19/2013_1112a code)

to

L = Kro+Krv*V*V;

In fact, you could make the rolling resistance any function of V, or even use a look-up table if you have experimental data.

However, I think the V*V term only comes into play due to air resistance at speeds much higher than FRC robot speeds. It would be enlightening to see some actual data of rolling resistance vs speed for a typical FRC robot (with drivetrain mechanically disengaged from wheels) on FRC carpet surface.

[SoftwareBug2.0]

Originally Posted by Ether

I structured the code to make it very simple to change the rolling resistance model if you want to. It takes only 2 keystrokes (^2) to change the rolling resistance model from

L = Kro+Krv*V; (line #68 in the 9/19/2013_1112a code)

to

L = Kro+Krv*V^2;

Um... "^" is xor in C.

[Tom Line]

Originally Posted by SoftwareBug2.0

Um... "^" is xor in C.

Someone slipped into excel mode in the middle of a line of C.

[Ether]

Originally Posted by Tom Line

Someone slipped into excel mode in the middle of a line of C.

Actually...
Octave, Maxima, SciLab, AWK, and RLaB :-)

[Andrew Schreiber]

Originally Posted by Ether

Actually...
Octave, Maxima, SciLab, AWK, and RLaB :-)

Which is still less weird than the weird case of coffeescript that I found while porting this by accident...

Turns out "variable *" compiles to "variable * variable" as opposed to throwing a compile error.

[brennonbrimhall]

Based on the discussion on this thread (see posts #24 and #28), I've ported Ether's/Andrew Schreiber's C code to Java, and made a GUI front-end with charting. It's not the most pretty thing ever coded, but it may help to make the calculator more accessible by non-programmers. You can find the source code here, with .jar file releases here.

I'd appreciate any feedback you might have.