Re: [Emc-developers] pid with derivative inputs

[Peter C. W. <pc...@me...>]

On Mon, 1 Nov 2010, Jon Elson wrote:

> Date: Mon, 01 Nov 2010 11:18:06 -0500
> From: Jon Elson <el...@pi...>
> Reply-To: EMC developers <emc...@li...>
> To: EMC developers <emc...@li...>
> Subject: Re: [Emc-developers] pid with derivative inputs
> 
> Peter C. Wallace wrote:
>>
>>
>> One good sanity check on the velocity output is to setup your hardware step
>> generator for quadrature mode and set a constant velocity but randomly
>> changing directions(and ~infinite acceleration). Another good test is just a
>> slow velocity ramp. The advantage is the the hardware doesnt have the quirks
>> of a real encoder/motor. For example, quadrature phase error (signals not at
>> exact 90 degrees) will limit the improvement that a simple, all edge time
>> stamp can bring.
>>
> But, I WANT to see how it responds to all the vagaries of real encoders,
> especially dither
> and the quantizing noise.  I was comparing against the software encoder
> component reading
> my MPG, with detents.  I observed the phase error effect as the detents
> in the MPG severely
> affected the quadrature phasing.  By gripping the knob tightly in my
> clenched fist I got most
> of the detent effect to disappear.  That was an interesting effect to
> observe.

Sure, ultimately you want to test with real world signals but when debugging 
its good to reduce the number of variables or at least have good control of 
them...

Peter Wallace
Mesa Electronics