Open Loop Command

[Chevvron]

Tom,
We have a linear axis with linear scale position feedback driven by an analogue servo drive and brushless motor with velocity feedback using +/10 volt command input.
Our initial setup would be to adjust the amplifier volts/rpm so that 9 volts analogue command input = our desired maximum axis velocity as an open loop motion move.
How do you use the Step response screen to command an open loop motion profile move so that we can set the +/-10 volt servo amplifier speed reference before then closing the position loop using the KFlop and tuning using the PID gains ?
Regards,
Tim

[TomKerekes]

Set the PID parameters to zero. Command a Move of your desired maximum velocity. Adjust the Velocity Feed Forward until you get a 9V output (9/10 x 2047 = 1842 DAC counts). Or, compute VFF from Output = VFF x Velocity. See:

[Chevvron]

Thanks Tom.
I now understand VFF = DAC counts with PID gains all zero.
Tim

[TomKerekes]

Hi Tim,

Actually it is DAC = VFF x Current Velocity. So for example if the Profile Velocity goes to 100000 counts/second and VFF = 0.01 then the DAC will be 1000 counts. Here is another related article.