Re: [oopic] Does oMathC work?

Those are good points, but fortunately, I won't have to worry too much about
that. The pulses will get shipped off to a desktop computer via a bluetooth
connection on demand. Therefore, I only really need the pulse counts, and
don't have to worry about interpolation or any calculations on the OOPic
itself. The noise that will happen, will be limitted to the low bits, but
there is no particular need to ignore them on a desktop, because they should
fall within a normal distribution around the true count.

The computer will send a value 0-127 for the speed of the motors. My current
plan is to measure the pulse rate for a few low speeds and computer a curve
of pulses/input. This curve will be used to calculate actual speed for the
high end where the pulse rate will probably become increasingly innacurate
due to overloading the OOPic. However, this speed will be fed to a dead
reckoning module that will keep track of where the robot is, while a
secondary system will confirm the moves relative to echos from two pairs of
SRF08 ultrasonic sensors. At low speed, the curve used by the dead reckoning
module will be tested by measuring pulse rates against the curve.

rtstofer wrote:
>
> As with all digital division/counting, calculating speed is highly
> non-linear with regards to bits.
>
> Consider just the least signifcant bits at low speed: adding one more
> bit doubles the calculated speed.
>
> At high speed, the low order bits are much less significant.
>
> So, consider how accurate you need to be and think about doing the
> conversion in ranges. Perhaps you could do some fairly quick linear
> interpolation from a look-up table in EEPROM. Or, maybe you don't
> even need to interpolate.
>
> As to getting speed from the output pulse width; that just won't work.
> As the load on the motor varies, the speed will vary as well
> regardless of the applied voltage.
>
> You might want to see what Phillip Malone has done (he used to hang
> out here but I haven't heard from him in a long time)
> http://philbot.com/software.htm

Phil has done some absolutely
> brilliant work with the OOPic.
>
> Richard
>
>
>
>

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