RE: Smoothing a roughly sinusoidal signal

[llrjt100]

Hi Allen,

Thanks for your reply.

For some reason my post appears twice in the topic list. I've uploaded the
.csv data in the first post.

The processed position data is the input for a motor controller, with a
control loop frequency of 20 Hz, so lag is undesirable. My first attempts at
this were with a simple moving average filter, from which I very quickly
learnt that the lag is proportional to how far back in time the filter
looks.

In terms of modelling the system, there's a stepper motor driving a gearbox,
the encoder is mounted on the output shaft. The fast ~2 s error in the graph
is microstep error, the ~24 s error in the graph is encoder interpolation
error, and most of the rest will be mechanical gearbox errors (the ratios of
each stage are known). The period of all the errors is related to the motor
velocity, so hopefully this constitutes a good model?



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