Hi LV-Experts!
I try to control a linear motor using LV and a cRIO-System including an FPGA. I have two question regarding the FPGA PID Express VI on LV 2013.
1) What is the expected scaling of SetPoint and Process variable input and what is the scale of the output of the PID-Express.vi?
My control variable is force given in [N] . I transform the process variable (measured voltage of a DMS bridge) to the same unit [N] and feed it into the PID und would feed the output directly to drive the motor. Is this ok? see VERSION 1 in PID-Scaling_Question.pnd below
Or should both be scaled to % of the max. input or relative to the max input. If the input is given in % or relative , how do I have to scale the PID output before feeding it to the motor?
VERSION 2 inPID-Scaling_Question.pnd
2) Could it help to scale the ouptput of the PID with the (known) motor scaling which is valid for the static case (F= scale x U)?
For the static case I know exactly the relation between voltage and produced force... VERSION 3 in PID-Scaling_Question.pnd
I have added a snippet and vi illustration all three situation (two for question one, one for question two) that might illustrate what I try to ask...
It would be very kind to get some feedback...
Luke
