Controlling Algorithm - Siemens SIMATIC S7-1200 Function Manual

Using PID basic functions
7.3 TCONT_CP
7.3.2.2

Controlling algorithm

General
1. Enter the "Sampling time PID algorithm".
A controller sampling time should not exceed 10 % of the determined integratl action time
of the controller (TI).
2. If the controller structure contains a proportional action, enter the "proportional gain".
A negative proportional gain inverts the rule meaning.
Proportional action
For changes of the setpoint, it may lead to overshooting of the proportional action. Through
the weighting of the proportional action, you can select how strongly the proportional action
should react when setpoint changes are made. The weakening of the proportional action is
reached through a compensation of the integral action.
1. To weaken the proportional action for setpoint changes, enter a "Proportional action
weighting".
– 1.0: Proportional action for setpoint change is fully effective
– 0.0: Proportional action for setpoint change is not effective
Integral action
With a limitation of the manipulated value, the integral action is stopped. With a control
deviation that moves the integral action in the direction of an internal setting range, the
integral action is released again.
1. If the controller structure contains an integral action, enter the "integral action time".
With an integral action time of 0.0, the integral action is switched off.
2. To give the integral action an initialization value, select the "Initialize integral action"
check box and enter the "Initialization value".
Upon restart or COM_RST = TRUE, the integral action is set to this value.
Derivative action
1. If the controller structure contains a derivative action, enter the derivative action time (TD)
and the coefficients DT1 (D_F).
With switched derivative action, the following equation should be maintained:
TD = 0.5 × CYCLE× D_F.
The delay time is calculated from this according to the formula:
delay time = TD/D_F
Set PD-controller with operating point
1. Enter the integral action time 0.0.
2. Activate the "Initialize integral action" check box.
3. Enter the operating point as the initialization value.
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Function Manual, 03/2017, A5E35300227-AC
PID control