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# Deriving Resonant Frequencey

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Investigating an issue where two axes sit on the same seals.

Excitation of one axis (Z-axis), displaces the other (Y-Axis) and vice versa.

I have made attempts to tune the opposing with Integrator (with Integration mode = 1)...results got worse.

My next approach is to use a notch filter in an attempt to use this as a low pass filter.

For the cut-off frequency, being a component of the Velocity....with this FFT how would I determine the appropriate value, or by what process?

Thank You

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Investigating an issue where two axes sit on the same seals.

Excitation of one axis (Z-axis), displaces the other (Y-Axis) and vice versa.

I have made attempts to tune the opposing with Integrator (with Integration mode = 1)...results got worse.

My next approach is to use a notch filter in an attempt to use this as a low pass filter.

For the cut-off frequency, being a component of the Velocity....with this FFT how would I determine the appropriate value, or by what process?

Thank You

Y-Axis Velocity FFT.bmp

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Can you tell if there is a deterministic relationship between the action of one axis and the disturbance of the other? If so, the best strategy is to characterize this relationship and create your own cross-coupled feedforward algorithm (usually in a PLCC 0) to put a counteracting torque offset in the other motor before there is a chance for the error to build up.

But the first step is to attempt to characterize the relationships. Are the errors proportional to the other motor's acceleration? Velocity? Both? I would look in time domain first, but both time and frequency plots can be valuable.

P.S. You do have some pretty big spikes at the AC line frequency and harmonics. I can't tell if these are causing real problems for you, but you may want to investigate this further.

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Can you tell if there is a deterministic relationship between the action of one axis and the disturbance of the other? If so, the best strategy is to characterize this relationship and create your own cross-coupled feedforward algorithm (usually in a PLCC 0) to put a counteracting torque offset in the other motor before there is a chance for the error to build up.

But the first step is to attempt to characterize the relationships. Are the errors proportional to the other motor's acceleration? Velocity? Both? I would look in time domain first, but both time and frequency plots can be valuable.

P.S. You do have some pretty big spikes at the AC line frequency and harmonics. I can't tell if these are causing real problems for you, but you may want to investigate this further.

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