This Forum is Dedicated For all The Object Oriented PIC Lovers .......... The concept behind OOPic is straight forward. Use preprogrammed multitasking Objects from a library of highly optimized Objects to do all the work of interacting with the hardware. Then write small scripts in Basic, C, or Java syntax styles to control the Objects. During operation, the Objects run continuously and simultaneously in the background while the scripts run in the foreground telling the objects what to do.

Saturday, March 8, 2008

Re: [oopic] Quadrature Encoder

On Mar 8, 2008, at 12:28 PM, Shaggy wrote:

> I also heard that in other peoples experience, wheel slippage will
> cause
> sufficient errors that simply counting wheel revolutions is a dubious
> measure to begin with. My alternatives seem to be these:
>
> 1) Possibly use oCounterH to count a single wheel speed (only 1 IO
> line for
> this object).
> 2) Just measure true ground speed the old fashioned way and make up
> a speed
> curve based on the set motor speed.
>
> Frankly, unless there is something I have missed, I'm inclined to
> just use
> option 2, since I have already implemented code that will be
> checking the
> dead reckoning position against sonar echoes. Is there anything else
> I might
> consider?

Using the encoder on a driven wheel will be inaccurate due to wheel
slippage as you have suggested. This is more of a problem on loose
ground. You can get better accuracy by putting an encoder on a non-
driven wheel (odometer).

Unless you always run on flat ground and unless your motors have
massive extra torque, just looking at motor speed input isn't going to
be very accurate either. How much accuracy do you need and what are
you willing to pay for it? If you want to go nuts you can add an
inertial reference but that is probably overkill for most applications.

--

Brian Lloyd Granite Bay Montessori
brian AT gbmontessori DOT com 9330 Sierra College Blvd.
+1.916.367.2131 (voice) Roseville, CA 95661, USA

http://www.gbmontessori.com

I fly because it releases my mind from the tyranny of petty things . . .
— Antoine de Saint-Exupéry

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