Siemens Module B3 manual Task Definition for PID Standard Controller

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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

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Contents Module B3 Automation and Drives SCE Table of Contents Automation and Drives SCE Frequency Converter at Simatic S7 To 3 days Module C To 3 days Module DLearning Objective PrerequisitesPLC Hardware and software requiredTasks of Control Engineering Fundamentals of Control EngineeringControlled Variable Components of a Control LoopFeedback Variable r Setpoint Value w Disturbance Variable zComparing Element Controlling ElementControlled System ActuatorDead Time Characteristics Step Function for Examining Controlled Systems ForAutomation and Drives SCE Time constant Proportional Controlled System with a Time DelayTu Delay time Tg Transition time Proportional Controlled System with Two Time DelaysControllability of P-Tn systems Proportional Controlled System with n Time Delays Controlled Systems without Inherent Regulation Types of Controllers Two Position Controllers Hysteresis Switch-On Value Manipulated Variable TimeThree Position Controllers Basic Types of Continuous Controllers Proportional Controllers P-Controller Automation and Drives SCE Integral Action Controllers I- Controller WithController Layout PI ControllersPID Controllers Derivative Action Controllers D-ControllerObjectives for Controller Adjustment 450.85 Digital Controllers DAC Preface Fundamentals YES StructogramExercise Assignment List Symbol Address CommentNetwork Possible Solution for the PLC ProgramD24/AIFillSetpNorm/Norm.value for level setpoint Network 10 Title Task Definition for PID Standard Controller Function Diagram of the control system with a PID controller Use FB 41 ContcDescription Exercise Example Automation and Drives SCE Automation and Drives SCE Automation and Drives SCE Automation and Drives SCE Automation and Drives SCE Automation and Drives SCE Automation and Drives SCE Automation and Drives SCE SP INT PLC’ Automation and Drives SCE Automation and Drives SCE Automation and Drives SCE Tu-TgApproximation GeneralT g Approximation Setting the PI-Controller according to Ziegler-Nichols For setpoint characteristic MAN Solution of the PLC program Setpoint Setting the PI controller according to Ziegler-NicholsAppendix Diagram of the controller blockComrst Bool False Input Parameters Data Value Range Default Description TypeParameter Data Type Value Range Default Lmnhlm Real Lmnllm Output Parameters Parameter Data Value Range Default Description Type