Open Loop Tuning

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Chevvron
Posts: 19
Joined: Mon Apr 22, 2019 9:26 pm

Open Loop Tuning

Post by Chevvron » Mon Oct 05, 2020 1:01 pm

Tom,
I thought i understood your reply to this question but i obvously do not.
With the machine motion control issues i want to check the velocity response of the axes and go back to the beginning.
I have attached the configuration for the Y axis.
I have attached the step response configured how i think i understand
9 volts = 1842 DAC output.
The axis maximum velocity for 9 volts = 150000 counts / sec = 150.000 mm / sec.
Acceleration = 150000 counts per sec / sec = 150.000 mm /sec /sec.
Jerk needs to be very high so response is trapezoidal.
I would start by commanding a move of 50000 counts / sec = 50.000 mm /sec and then adjust the servo amplifier to match the commanded velocity to the actual velocity.

Where am i going wrong ?

I have read the help section on configuring an open loop spindle and with the example settings and no encoder input i get what i expect on my Y axis but obviously i need to see the actual axis velocity to make sure the velocity loop is tuned correctly.

Regards,
Tim
Attachments
OPEN LOOP RESPONSE.jpg
Y AXIS CONFIG.jpg

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TomKerekes
Posts: 1117
Joined: Mon Dec 04, 2017 1:49 am

Re: Open Loop Tuning

Post by TomKerekes » Mon Oct 05, 2020 3:38 pm

Hi Tim,

I'm not sure what you are trying to do. But with a Velocity FF of 1842 it will output the 9V at a velocity of 1 count/sec. But you are commanding 150,000 counts/sec. So as you see in the plot the output immediately saturates at 10V. The axis moves at its maximum speed of ~150000 counts/sec and then soon gets a following error. You probably want to set the VFF at:

2047/150000 = 0.0136
Regards,

Tom Kerekes
Dynomotion, Inc.

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