Brushed DC motor encoder oscillations
Brushed DC motor encoder oscillations
(OP)
I purchased a Pittman brushed DC motor with a 500 count/rev encoder. I noticed quite a bit of oscillation in the encoder signal when the shaft is rotating at a constant rate. After running some tests I started to notice a trend. For instance, when I ran the motor at an average 600 RPM (averaged from the encoder oscillations), or 10 rev/s I measured a 10 Hz oscillation in the encoder signal. Running at an average 1200 RPM, or 20 rev/s I measured a 20 Hz oscillation in the encoder signal. I performed this test at various speeds and always found the oscillations to equal the motor's frequency. I tried running the motor at a very low rate (~1 Hz) and can actually see/hear the motor slow down at a certain point once every revolution.
I am speculating that perhaps there is a commutation issue with one of the brushes. I am curious if anyone else has some experience with this and if they have any suggestions. I ultimately want to use the encoder for feedback control and would like to solve the issue itself rather than just adding filters. Any recommendations would be greatly appreciated.
:LabGuy330
I am speculating that perhaps there is a commutation issue with one of the brushes. I am curious if anyone else has some experience with this and if they have any suggestions. I ultimately want to use the encoder for feedback control and would like to solve the issue itself rather than just adding filters. Any recommendations would be greatly appreciated.
:LabGuy330





RE: Brushed DC motor encoder oscillations
RE: Brushed DC motor encoder oscillations
RE: Brushed DC motor encoder oscillations
:LabGuy330
RE: Brushed DC motor encoder oscillations
You may be able to improve the performance of your system even with the Pittman motors by adjusting the phasing between the encoder and the motor's commutator.
Mike Halloran
Pembroke Pines, FL, USA
RE: Brushed DC motor encoder oscillations
TTFN

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RE: Brushed DC motor encoder oscillations
:LabGuy330
RE: Brushed DC motor encoder oscillations
what exactly does that mean?
your motor does NOT - note - NOT - have a once per rev cogging - it is impossible.
SO. AGAIN, how are you running this motor where is the voltage and current coming from?
please do not jump to some conclusion about cogging when your data makes that not a possible cause.
RE: Brushed DC motor encoder oscillations
RE: Brushed DC motor encoder oscillations
No conclusions have been made. This is a discussion. I only relayed the information I received after calling Pittman motors. I am still very open to the advice from others.
:LabGuy330
RE: Brushed DC motor encoder oscillations