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Encoder Model

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Hi

 

Iam using a simple quadrature encoder...I need to know how should I model it in the control loop.

 

Thanks

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Hello SK0480

 

Thank you very much for getting in touch with us!  The quadrature encoder is simply a way of determining the position/speed/acceleration of your motor through feedback.  It should have negligible effects on the system dynamics. 

 

Are you simply looking to convert the encoder feedback to something meaningful?  If so, all you would need to do in your feedback loop is add a compatibility equation for your sensor converting the number of encoder counts to the number of revolutions.

 

How many encoder counts are there per revolution?  You would simply want to include an equation in your code to convert the encoder counts to motor revolutions in order to implement your feedback system. 

 

 

Sincerely,

Greg S.
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Hi

 

The resolution of the encoder is 16 pulses per revolution....so i want to convert the counts to the revolution what would be the equation for it

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Accepted by topic author SK0480

Hello SK0480

 

Thank you for this information. To find the number of revolutions for a given number of pulses, simply divide the number of pulses by 16.

 

For a more detailed explanation:

 

If you know that the encoder is 16 pulses per revolution then we also know how many revolutions per pulse we have.  To obtain this value, we simply take the inverse value of the pulses per revolution to find the number of revolutions per pulse.

 

In short, Number of Revolutions = (Number of Pulses) / 16 = (1/16) x Number of Pulses = (0.0625 x Number of Pulses)

 

So, if you have convert counts to revolutions, multiply the number of pulses by 0.0625 or divide by 16.

 

I have included a  document that illustrates this step by step but I do not mean to make this situation overly complicated.

 

This concept will be very important for your success so please let me know if I can provide any further clarification. 

Sincerely,

Greg S.
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Hello

 

Thanks for sending me the compatibilty equations.

 

Ok now the quadrature encoder iam using has a resolution of 16 pulse /revolution as I mentioned earlier...what iam getting out of this encoder is the angle that motor has rotated..so what would be proper compatibility equation.

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If the feedback you are receiving is the rotation angle and you want to know how many times the motor has turned, just divide the fed back rotation angle by 2*pi radians or 360 degrees.  One rotation is defined as 2*pi radians or 360 degrees.   Please let me know if this is clear, I will be happy to explain it further as you require.

Sincerely,

Greg S.
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Iam basically building model of the entire system on a paper by hand so iam not using labview to model. Iam using a second order tf for the motor and gain block for the amplifier and iam using the counter on my daq device to count the pulses. the way i have configured the encoder using the daq assistant is that it is giving me angle not edges. So what iam trying to find out is should i include just the constant such as .0625 to get revolution per pulse. or do i also need to take into account counter
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Hello SK0480

 

If you are building a block diagram, you won't have to include your sensor conversions for the feedback.  What I am most concerned about is that you may accidentally consider this conversion factor as a gain.  You will receive different system dynamics if you do this.

Sincerely,

Greg S.
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so are you saying to not include anything in the feeback

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Hello SK0480

 

So that I can best assist you, what system exactly are you trying to control and what is your input/ouput signal that you are dealing with?  Do you want to upload your current model for my reference?  Thank you very much for your response!

Sincerely,

Greg S.
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