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]

Originally Posted by GeorgeTheEng

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.

[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]

Originally Posted by squirrel

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.

[billbo911]

Originally Posted by squirrel

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]

Originally Posted by billbo911

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".

[GeorgeTheEng]

Originally Posted by Branden Ghena

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

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]

Originally Posted by GeorgeTheEng

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.....