Sorry, the link got broken when I uploaded a corrected version. Here's the new link:
http://www.chiefdelphi.com/media/papers/download/2858
Also, note that there are two different ways to connect the angle error signal to the LabVIEW PID:
1) Connect the error to the Setpoint input, and connect a constant zero to the ProcessVariable input. This is the way mentioned in the paper.
2) Connect the negative of the error (i.e. -error) to the ProcessVariable input, and connect a constant value of zero to the Setpoint input.
The first way effectively disables the "D" portion of the PID (which you probably don't need for this application anyway).
The second way allows the "D" action of the PID to be used, but in a way perhaps not intended by the designer of the PID, since it causes the PID to use the derivative of both the ProcessVariable and the Setpoint. The PID is designed to take the derivative of the ProcessVariable input only*, so using this second way may result in instability or other unexpected behavior.
* see this thread:
http://www.chiefdelphi.com/forums/sh...ad.php?t=88233