Siemens Module B3 manual Task Definition for PID Standard Controller

Automation and Drives - SCE

4. CONTROLLER BLOCK (S)FB41 "CONT_C" AS SOFTWARE PID CONTROLLER IN STEP 7

4.1 Task Definition for PID Standard Controller

In this B3 module, the startup of a PID controller in SIMATIC S7 is demonstrated. The output value of the controlled system is to be kept constant with a continuous controller. Depending on the setting, the controlled system can simulate a P, PT1, or PT2 system. The transfer coefficients Ks and the time constants can also be set. (refer to the description of the controlled system).

Thus, the PLC is the controller, and is connected to the controlled system by means of analog inputs and outputs.

The block (S)FB 41 in the PLC SIMATIC S7-300 is used in this task as a continuous digital software controller. It is to solve the control problem as follows: an analog manipulated variable y is read out depending on the respective setpoint/actual value w-x. The manipulated variable y is generated according to the PID algorithm.

The following control parameters can be specified:

KP: Proportional component (for (S)FB41 Gain)

TN: Integrator time (for (S)FB41 TI)

TV: Derivative time (for (S)FB41 TD)

	Preface Fundamentals	Discontinuous Action Controllerr	Controller Block (S)FB41	Setting the System Appendix
	T I A Training Document	Page 37 of 64		Module
				B3
Issued: 02/2008				Control Engineering with STEP 7