Closed Loop Velocity control using NI-9505 and niFPGA Discrete PID.vi

[MKHokie]

Hello,

I have an application that is roughly based off of the example found in ...\examples\CompactRIO\Module Specific\NI 9505\Velocity Control (closed loop)\Velocity Control (closed loop) - NI 9505.lvproj

The "niFPGA Discrete PID.vi" that that this example uses takes an INT16 in for the velocity set point.  The issue that I am having is that in our mechanical setup, the difference between setpoint increments equates to a large changes in mechanical velocity i.e. a setpoint of 1 equates to about 4mm/min of movement to the piece attached to the screw, and a setpoint of 2 equates to about 11 mm/min.

I would like to have finer control over the motor velocity such that I can obtain speeds in between integer setpoints.  Any suggestions?

Also, does anyone have any suggestions on how the motor current sense output of the 9505 can be used to calculate an average current value (the amount you'd expect to see if you put an ammeter in series with the motor) and not the current during the "on" phase of the PWM cycle?

Thanks

[Justin__D]

Hi MKHokie,

Since this is more of a motion question, it might be best to post it on the Motion Control board.  You should get more views and possibly a quicker answer.

In the meantime I am looking into your question to see what the best option would be.