Siemens Module B3 manual FB 41 Contc, Use, Description

Automation and Drives - SCE

4.2 (S) FB 41 “CONT_C“

(S)FB 41 "CONT_C“ (continuous controller) is used for controlling technical processes with continuous input and output variables on the PLC SIMATIC S7. By means of parameter assignments, you can switch on or switch off subfunctions of the PID controller, and thus adjust it to the controlled system.

Use:

You can use the controller as PID fixed setpoint controller individually, or in multi-loop control systems as cascade controller, blended controller, or ratio controller. The working method is based on the PID algorithm of the sampling controller with analog output signal; if needed, supplemented with a pulse shaper step to generate pulse-width-modulated output signals for two position or three position controller with proportional final control elements.

Description:

In addition to the functions in the setpoint and actual value, the (S)FB implements a complete PID controller with a continuous manipulated variable output and the capability to influence the manipulated value manually.

Depending on the CPU type, it can be used as FB 41 or as SFB 41.

The following subfunctions exist:

-Setpoint branch

-Actual value branch

-System deviation generation

-PID algorithm

-Manual value processing

-Manipulated value processing

-Feedforward control

Operating modes complete restart/restart

The (S)FB 41 (CONT_C) has a complete restart routine that is run if the input parameter is set to COM_RST = TRUE.

At startup, the integrator is set internally to the initialization value I_ITVAL. When called in a time interrupt level, it continues processing starting with this value.

The other outputs are set to their default values.

Error Information

The error signal word RET_VAL is not used.

	Preface Fundamentals	Discontinuous Action Controllerr	Controller Block (S)FB41	Setting the System Appendix
	T I A Training Document	Page 39 of 64		Module
				B3
Issued: 02/2008				Control Engineering with STEP 7