Motor vibration/ noise due to parameter setting or resonance frequency?

[seeker21]

Having problem on driving a motor with L6470 at speed range around 120 - 300pps where motor vibrates and making buzzing noise ,especially louder at 150 step/s, or mounting on a panel where the whole mechanical piece parts is vibrating together.

Already followed the parameter optimization step stated in the application notes AN4144, which is target to optimize the compensation curve so that the current output is stable across the application speed range.

However the vibration still happened and the measured current wave showing distortion.

I suspect the vibration is due to the resonance frequency of the motor but I already drive it with 128 micro step... Lowering the current and operate beyond the motor's resonance frequency range is not possible to be the solution for my application.

Not sure if anyone facing the same problem and could give me any guidance on this?

Perhaps someone who experienced on motor can help me to confirm that the root cause is due to resonance frequency of the motor and nothing relate to my setting on L6470.

[Dario CUCCHI · Accepted solution]

Hi @seeker21​ and welcome to ST Community !

Seems from your description that you are facing a resonance problem.

I think the panel on which is mounted has the effect to shift down in frequency and amplifying the mechanical resonance of the motor itself.

So the frequency falls in the frequency range of your application.

The distortion in the current waveform is introduced by the resonance and its harmonics.

Since the effect of this resonance is very big, the L6470 cannot drive properly the motor.

You should act on the mechanical aspect of your system, to improve its behavior.

If possible, try to use a thick panel, with higher mechanical stiffness and with a smaller mass.

Try to fix the motor to the structure not only in the front (where usually have the screws) but also on the rear with a proper support frame.

The point is not to eliminate the mechanical resonances (it is not possible), but to shift them up outside the frequency working range of your application.

I understand maybe these are generic suggestion but the solution here depends on your specific mechanical system.

Then, a quick check you can do about the parameters is to see if outside the critical range (120 - 300 pps) the current in the motor phases behaves as you expected and has a sinusoidal shape.

I hope this can help.