186 Rockwell Automation Publication 2080-UM005E-EN-E - March 2018
Appendix D PID Function Blocks
PID Application Example
The illustration above shows a basic water level control system, to maintain a
preset water level in the tank. A solenoid valve is used to control incoming water,
filling the tank at a preset rate. Similarly, outflowing water is controlled at a
measureable rate.
IPID Autotuning for First and Second Order Systems
Autotune of IPID can only work on first and second order systems.
A first order system can be described by a single independent energy storage
element. Examples of first order systems are the cooling of a fluid tank, the flow of
fluid from a tank, a motor with constant torque driving a disk flywheel or an
Output Sequence 1: 50 -> 70 -> 30
Sequence Condition Autotune Result Action for Autotune Fail
Process value reached 'first peak' and
'second' peak in time
Likely successful NA
Output Sequence 2: 50 -> 70 -> 50
Sequence Condition Autotune Result Action for Autotune Fail
Process value not able to reach
'first peak'
Likely unsuccessful Reduce Deviation or Increase Step
Output Sequence 3: 50 -> 70 -> 30 -> 50
Sequence Condition Autotune Result Action for Autotune Fail
Process value not able to reach
second peak
Likely unsuccessful Increase Deviation or increase Step
Output Sequence 4: 50 -> 70
Sequence Condition Autotune Result Action for Autotune Fail
Process value not able to reach First
peak in time
Likely unsuccessful Increase ATDynamSet
Water In
Water Level
Tank
Water Out
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