Setting Pid Constants Manually; Example Pid Control Application - Omron CJ Series Operation Manual

Setting the PID Constants
Stopping Autotuning
3-9-2

Setting PID Constants Manually

Note
3-9-3

Example PID Control Application

Procedure
1,2,3...
58
same time. Use this flag as an input condition in the CPU Unit's ladder
program and transfer the PID constants from the Operating Parameters'
input area to the word in the output area where the PID constants are
stored.
After the PID constants have been transferred, turn the Change PID Con-
stants Bit from OFF to ON. Toggling this control bit causes the Tempera-
ture Controller's PID constants to be refreshed with the new PID constants
in the output area.
Note Autotuning cannot be started if the Unit is stopped or using ON/OFF control
operation.
• To stop autotuning, turn the Stop AT Bit from OFF to ON. The Stop AT Bit
is in the Special I/O Unit Area words allocated to the Temperature Control
Unit in the CIO Area.
• Only the Stop Bit and Stop AT Bit settings can be changed while autotun-
ing is being executed. Settings changed during autotuning will be enabled
when autotuning is completed.
• If the Stop Bit is turned ON while autotuning is being executed, autotuning
will be interrupted and operation will stop. Autotuning will not restart when
operation is restarted with the Stop Bit.
The PID constants can be set manually by setting the desired values for the
proportional band (P), integral time (I), and derivative time (D) in the corre-
sponding words of the Operating Parameters in the DM words allocated to the
Unit.
1. When you already know the system's control characteristics, set the PID
constants directly to adjust the control characteristics. Set the three PID
constants: The proportional band (P), integral time (I), and derivative time
(D).
2. The Unit will operate with basic proportional operation if the integral time
(I) and derivative time (D) are set to 0. If the default settings are used, the
proportional band will produce a manipulated variable of 0.0% at the set
point.
In this example, autotuning is executed for loop 1 and loop 1 operates using
PID control with two degrees of freedom.
1. Start autotuning by turning ON the Loop 1 Start AT Bit (bit 02 of CIO (n+2)).
2. When autotuning is completed, the calculated PID constants are stored in
the input area of the Operating Parameters in the DM words allocated to
the Unit. (The calculated PID constants are transferred from Temperature
Control Unit to CPU Unit.) At the same time, the PID Constants Calculated
Flag (bit 10 of CIO (n+8)) is turned ON.
Use the PID Constants Calculated Flag as an input condition in the ladder
program and copy the calculated PID constants to the output area of the
DM words allocated to the Unit.
3. After the PID constants have been transferred to the output area by the lad-
der program, turn ON the Change PID Constants Bit (bit 13 of CIO (n+2)).
The PID constants in the output area will be read by the Temperature Con-
trol Unit.
Section 3-9