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Stablising the compensaton loop for the AD2S82A part?

Question asked by BarryF_S on Nov 12, 2014
Latest reply on Dec 15, 2014 by jcolao

Hi all

 

I was wondering if anyone could offer some advice on stablising the compensaton loop for the AD2S82A part?

 

My system is set up as 12 bit with a ref freq of 16.7kHz, with a tracking rate of <200 rps required.

I used the Component Selection software to calculate the external component values - see attached.

 

The issue I have is the position reading from the RDC fluctuates by about 7 bits.

Checking the compensation circuit I noticed that the integrator output pin (velocity signal) has a significant ripple present - see attached screenshots for examples.

 

The noise level of the position reading seems to be directly related to the amplitude of the fluctuation I see on the velocity signal.

The velocity signal ripple varies in amplitude and form as the position of the motor changes.

 

Would it be safe to assume that the issue is that the compensation loop is unstable or should I investigate other aspects of the circuit first?

 

Any form of help or suggestions would be much appreciated.

 

Thanks

Barry

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