[DUG] Chart Smoothing

[Alistair Ward]

Hi Wallace,

What you have here is not a charting problem, but a signal processing
problem.

I've not done a lot of work in the signal processing field, but I would
suggest you do some research into Kalman filters - these may be what you
are looking for.

I would feed the raw data through a filter, and then feed the filtered data
to the charting component.

Another (possibly simpler) filtering approach would be to apply a low-pass
filter to the data.

As usual, Google is your friend with these things :-) (try search for
discrete time low pass filter)

Cheers,
Alistair.


On Tue, 11 May 2021 at 18:25, Marshland Engineering <
marshland at marshland.co.nz> wrote:

> After much searching, I cannot find 3rd part components to use.  Am I
> search
> for the wrong thing ?
>
> This is version 2 of my dyno. The old version was a bought package that
> used a
> Freq to voltage converter and then an A to D converter for the input to
> the PC
> but he resolution was very poor and I had to do a lot of fiddling with
> higher
> power bikes to get reasonable data.
>
> My idea with this version is to get as high a resolution as I can.
>
> If you have some time to spare, here is my logic.
>
> The drum speed goes from 45 to 65 kph over 4 seconds. Or 12.5 to 18 m/s
> I'm sampling at 30 hz
>
> Over the time period, I take 120 samples. The average rate of change of
> each
> sample is 0.17 kph. If I take the 0.17m over the average speed range, it is
> 1/330 or 0.3 %. That is quite optimistic for dyno, but it where I'm
> starting.
>
> Each timing period from the drum represents 200mm on the surface and the
> ATMEGA can count up to 65535 clock cycles in this period.  My resolution on
> the ATMEGA is therefore  0.003 mm per clock cycle.
>
> I think I have enough resolution for what I want.
>
> One of the problems is that the wheel to drum, engine speed changes etc are
> not exactly linear. I believe this is where the noise is from, however, the
> data below the noise is valid.
>
> I can improve the plots by fewer samples, ie getting a bigger rate of
> change
> between samples but then my resolution will decrease.
>
> Cheers Wallace.
>
>
>
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