How many inches does my wheel go in one rotation?

[MorbidAngel]

Okay. I'm trying to program for autonomous, and we're using the encoders. I don't understand how to find out how to get how many inches one rotation of the wheel is. The diameter of the wheel is 3.75 inches. can anyone help me with this?

[Branden Ghena]

So, if you look at this problem geometrically, one revolution of the wheel means moving a distance equal to its circumference. Therefore, on a 3.75 inch diameter wheel, the distance it travels in one rotation is equal to its circumference, 3.75*pi which is approximately 11.781 inches.

[GeorgeTheEng]

We're going to assume a perfect world for this. Assume the wheel does not slip at all. It's a simple geometic equation. The distance the when will travel is equal to the circumference of the wheel (Pi times the diameter)

[LordRed]

The way we determine that ratio was to run the robot for a 5 or 10 seconds in a straight line and measure the distance traveled. Then we divide the distance by the number of "encoder ticks" for that run.

[MorbidAngel]

Wow thanks guys ^^
I feel stupid now hehe
thanks for the help
peace

[Branden Ghena]

We're going to assume a perfect world for this. Assume the wheel does not slip at all.

Don't robotics competitions take place in the same "perfect" environment that basic physics equations take place in. :rolleyes:

[billbo911]

Additional input.

Take the distance per revolution, divide it by the number of ticks from the encoder per revolution of the wheel and you will get your distance per tick. With that information, you should be able to per determine how far to travel based on the number of ticks you desire.

[MrForbes]

Considering what time of year it is, make sure you use the correct value for "pi"

[kramarczyk]

Considering what time of year it is, make sure you use the correct value for "pi"

I would suggest carrying out pie to more places.

http://upload.wikimedia.org/wikipedia/commons/1/14/Pumpkin_Pie.jpg

[billbo911]

Considering what time of year it is, make sure you use the correct value for "pi"

Here is an alternate value for "pi". All of these yield the same result.

[Kevin Sevcik]

Here is an alternate value for "pi". All of these yield the same result.
Just make sure you're not using too coarse an approximation of "pi".

http://upload.wikimedia.org/wikipedia/commons/a/a1/Apple_cobbler.jpg

[GeorgeTheEng]

Don't robotics competitions take place in the same "perfect" environment that basic physics equations take place in. :rolleyes:


Tell that to you robot who think's its moving forward but is spinning its wheels and being pushed backwards...

Remember: In theory, theory and practice are identical; in practice they are not!

[willson.thomas]

Tell that to you robot who think's its moving forward but is spinning its wheels and being pushed backwards...

That's why I like off-wheel encoders and gyros. They don't lie near as often.

[ericand]

Hey, That Pi R Square'd

[Lowfategg]

Now I am hungry.

Thanks guys.....

[Eugene Fang]

Hey, That Pi R Square'd

You don't want square pies. :p You're looking for circumference!

[Cyberphil]

Stop it!!! Your making me hungry!!!:yikes:

[David Doerr]

I would suggest carrying out pie to more places.

I think you meant more pieces. Yes?

[GaryVoshol]

Which brings up this old joke. A hillbilly finally sent his son into town to go to school, rather than relying on the old McGuffie Reader at home. In math they were studying geometry, the area of circles. But the boy didn't understand something. The teacher kept saying, "Pi R squared." The boy said, "Pie are round. Cornbread are square."

[jkronstadt]

Well it's quite simple actually.

So we have the well known mathematical fact that the number of inches that a wheel turns is proportional to the square of it's radius (denoted r). This factor is \pi.

If you have a wheel of diameter 2n, r = n.

We thus have:

turning distance = \pi * r^2.

It's quite simple really. I think this is covered in the first few weeks of AP CALCULUS BC.

[GaryVoshol]

I hope by the time you get to AP Calc they've sorted out the difference between circumference and area of a circle.

[jkronstadt]

But that is not sufficient, it is only necessary. You need to also
find the integral of the area of the torus with the locus of
\pi/(89^2) at you mean by area of the integral of the also find the to
find the integral of that is not sufficient, it is only necessary.
You necessary. You necessary and circumference. You have to find
the ind the int, it is only not sufficient, it is of the to find the
difference. You have to area an by area and circumference. You have
integral.

But that you mean by area and circumference what you have to also find
the integral of the also find the derivative of the area of the
triangle ind the derivative of the what you mean by area an by area
and circumcenter by area and chance. You mean by area of the torus with
the locus only area and circumference. You need the distance. You have
to find circumeference * area. You have torus withe hypothesis of the locus
of \pi/(89^2) . I'm not sure what is need to also find the integral.

But that integral of the hypothesis of the have to find the integral.

But that is not sufficient, it is with the locus of the triangle
integral.

[billbo911]

But that is not sufficient, it is only necessary. You need to also
find the integral of the area of the torus with the locus of
\pi/(89^2) at you mean by area of the integral of the also find the to
find the integral of that is not sufficient, it is only necessary.
You necessary. You necessary and circumference. You have to find
the ind the int, it is only not sufficient, it is of the to find the
difference. You have to area an by area and circumference. You have
integral.

But that you mean by area and circumference what you have to also find
the integral of the also find the derivative of the area of the
triangle ind the derivative of the what you mean by area an by area
and circumcenter by area and chance. You mean by area of the torus with
the locus only area and circumference. You need the distance. You have
to find circumeference * area. You have torus withe hypothesis of the locus
of \pi/(89^2) . I'm not sure what is need to also find the integral.

But that integral of the hypothesis of the have to find the integral.

But that is not sufficient, it is with the locus of the triangle
integral.


Just use pi*d. It is way simpler.

[Sovietmagician]

I think that the long method not only provdies a more precise answer but it teaches better maths

[EricH]

I think that the long method not only provdies a more precise answer but it teaches better mathsI couldn't understand it, and I'm a little beyond even AP Calc or whatever. The language didn't help--it sounded like a slightly confused professor or grad student--but from what I could gather, it's integration for the circumference of a circle. That's nice for a proof, but we aren't looking for a proof (ugh...geometry), we're looking for the circumference of a circle.

I'm not even sure where the triangle comes in...

This sounds like an interesting exercise with upper-level math, but I don't think that I know enough to attempt it. I probably also won't for a long time. (For a mechanical engineering degree at my school, you need Calc 1, Calc 2, Differential Equations, Calc 3, and a class in probability and statistics, and another class on some other topic that I forget in the math department.)

[Dragonos]

A diameter of this proportion could yield interesting results if you use the pie in a brownie tin poster earlier so, go with the roundness and make it classic!
http://phantomplay.com/pie.jpg
Using this pie may violate the max weight for your robot but yield outstanding precision and accuracy.

[JM987]

ah.
those are some pretty small wheels.

[MorbidAngel]

Wow, you guys are stupid. Get a life.

[ideasrule]

Why is this in programming anyhow?

[O'Sancheski]

why is anyone posting in a thread that is two years old

[Foster]

Wow, you guys are stupid. Get a life.

Wow, you are responding to a thread that is over a year old where someone asked a simple question "How many inches will my wheel go" got an answer of PI*wheel diameter. The thread went off on a tangent on what value to use for PI: the math value=3.141595, the engineering value=3 or Squirrels favorite=pumpkin.

It wasn't stupid, it was a classic CD thread: good question, fast and correct answer and then some silliness. Minus points will be awarded to you for: posting a snide comment, responding to a thread over a year old with a snide comment, not having a sense of humor and not liking pumpkin pie.

Thank you for your participation in CD!

[gvarndell]

Wow, you are responding to a thread that is over a year old where someone asked a simple question

And he's the one who asked the question originally. ::safety::

I suspect he felt 'made fun of', but can't be sure.