Rockwell Automation 2080-LC10-12DWD Micro810 Programmable Controllers User Manual User Manual
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Rockwell Automation Publication 2080-UM001D-EN-E - September 2012
Appendix D IPID Function Block
• PID_PWM
This user defined function block provides a PWM function, converting a
real value to a time related ON/OFF output.
• SIM_WATERLVL
This user defined function block simulates the process depicted in the
application example shown before.
IMPORTANT
User Program Scan Time is Important
The autotuning method needs to cause the output of the control loop to
oscillate. In order to identify the oscillation period, the IPID must be
called frequently enough to be able to sample the oscillation adequately.
The scan time of the user program must be less than half the oscillation
period. In essence the Shannon, or Nyquist-Shannon, or the sampling
theorem must be adhered to.
In addition, it is important that the function block is executed at a
relatively constant time interval.