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motor phase current


deltaa
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Geo Brick LV to drive a two phase stepping motor in direct micro-stepping mode with 32 micro steps per full step.

Current waveform distortion noticed around zero-cross area as shown in the attachment.

Motor current: 5 A peak to peak

Frequency: 20 ms/div

 

Any idea on how to correct the zero-crossing distortion? thanks.

phase_current_5apeak.jpg.2cccc39362ae1fc277817a1660577382.jpg

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Please refer to the attached plot,

1403265556_ScreenHunter_06Jun_1313_43.thumb.jpg.668bef9062882ccf1254728d124e432e.jpg

 

zoomed,

1778281012_ScreenHunter_08Jun_1313_43.thumb.jpg.aca80a8f38a59685a0527ff7a8c30ddc.jpg

 

Motor is not running smoothly during the movement. ADC readback shows the same pattern as the phase current measurement. The waveform deteriorates as the current setting becomes smaller and smaller.

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2 suggestions:

 

1. Use the Geo Brick LV Setup Assistant Excel spreadsheet available through FileDepot Link (in the menu bar of the forum) in order to get 2048 microsteps per full stepper of the motor.

2. Reduce the I7004 and I7104 (Pwm Dead-time) to a value of 4. This should reduce your zero-crossing distortion.

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Setup the test according to the suggestion, ran several tests and checked ADC readback. When motor is running at a lower speed, the performance is acceptable, with the increase of the speed, more vibration introduced and ADC B readback became distorted, any suggestion? Thanks

Setup: 2048 steps/full step, motor current around 3amp RMS.

 

I122=100, looks good and feels acceptable

I122_100.thumb.jpg.e3b962e5c5dfa12d85071ea0003d3a0a.jpg

 

I122=200, looks ok

I122_200.thumb.jpg.bbbf9c7d50cb8449a4c91f0b4e0a6d3c.jpg

 

I122=300, looks and feels bad

I122_300.thumb.jpg.f1e0aac05212d836a245725324c2ef9f.jpg

 

I122=300, difference Geo Brick

I122_300_2nd.thumb.jpg.b77c106c8a5e1a672956458809e4f300.jpg

 

2 suggestions:

 

1. Use the Geo Brick LV Setup Assistant Excel spreadsheet available through FileDepot Link (in the menu bar of the forum) in order to get 2048 microsteps per full stepper of the motor.

2. Reduce the I7004 and I7104 (Pwm Dead-time) to a value of 4. This should reduce your zero-crossing distortion.

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  • 4 weeks later...

In our experience ( 200 + geobrick - Lv) the current loop tuning will have a significant affect upon smoothness. Alsoi that as stepper speed approaches the const current - const volts cross over some detunuing of the loop can reduce resonances, but we have yet to make an automatic detection and detune for thsi problem.

Further we have been previously advised by SINA that it is possible to set I7m04 to 0 for stepper motors ONLY, but this will only apply to units shipped after a certain date. Is this still the case ( I note his post suggests a value of 4)?

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