Instructions
9.4 PID basic functions
PID control
476 Function Manual, 03/2017, A5E35300227-AC
Integral action (TI, I_ITL_ON, I_ITLVAL)
In manual mode, it is corrected as follows: LMN_I = LMN - LMN_P - DISV.
If the output value is limited, the integral action is halted. If the control deviation moves the
integral action back in the direction of the output range, the integral action is enabled again.
The integral action is also modified by the following measures:
● The integral action of the controller is deactivated by TI = 0.0
● Weakening of the proportional action when setpoint changes occur
● Control zone
● The output value limits can be modified online
Weakening of the proportional action when setpoint changes occur (PFAC_SP)
To prevent overshoot, you can weaken the proportional action using the parameter
"Proportional factor for setpoint changes" (PFAC_SP). Using PFAC_SP, you can select
continuously between 0.0 and 1.0 to decide the effect of the proportional action when the
setpoint changes:
● PFAC_SP = 1.0: Proportional action has full effect if the setpoint changes
● PFAC_SP = 0.0: Proportional action has no effect if the setpoint changes
The weakening of the proportional action is achieved by compensating the integral action.
Derivative action (TD, D_F)
● The derivative action of the controller is deactivated by TD = 0.0
● If the derivative action is active, the following relationship should apply:
TD = 0.5 * CYCLE * D_F
Parameter Settings of a P or PD Controller with Operating Point
In the user interface, deactivate the integral action (TI = 0.0) and possibly also the derivative
action (TD = 0.0). Then make the following parameter settings:
● I_ITL_ON = TRUE
● I_ITLVAL = operating point;
Feedforward control (DISV)
A disturbance variable can be added at the DISV input.
To Next Page
Loading...
Need help?
General
