modelPI

Proportional + Integral controller

Extends from Interfaces.Controller (Partial interface for a generic controller).

Information

Description

Proportional + Integral controller with Automatic, Tracking mode and bias signal.
The control law is defined as

              1+sTi 
  CS(s) = Kp ------- (SP(s) - PV(S))
               sTi

Scheme

Name	Description	Conditional?
SP	Set Point	NO
PV	Process Variable	NO
CS	Control Signal	NO
TR	Track Reference signal	YES (useTS)
TS	Track Switch signal	YES (useTS)
Bias	Biasing signal	YES (useBIAS)
ATreq	AutoTuning request	YES (*)

(*) AutoTuning Not available here, please see the package
AutoTuning

The controller can have various operating conditions:

Automatic,
and Tracking

In the Automatic mode, the control output is computed with the proportional+integral control law, while in the tracking mode
it is defined by the input TR.

To note that in the tracking mode the output signal CS is equal to TR, and the first order filter

     1
  -------- TR(S)
   1+s*Ti

is replaced by

     1
  -------- TR(S)
   1+s*eps

where eps is a small time constant. With such a scheme, the integrator does not diverge while the tracking mode
is enabled.

Parameters

Type	Name	Default	Description
Real	eps (from Controller)	1e-1	small time constant that represents the time for switching between auto and tracking mode
Boolean	useTS (from Controller)	false	=true, if TS and TR inputs are enabled
Boolean	useBIAS (from Controller)	false	=true, if BIAS input is enabled
Boolean	useAT (from Controller)	false	=true, if AutoTuning input is enabled
Boolean	useGS (from Controller)	false	=true, if GainScheduling inputs are enabled
Boolean	useSAT (from Controller)	false	=true, if Saturation outputs are enabled
Discretisation
Real	Ts (from Controller)	0	Sampling time (if <= 0 continuous time)
IndustrialControlSystems.LinearSystems.Discrete.Types.discrMethod	method (from Controller)	IndustrialControlSystems.LinearSystems.Discrete.Types.discrMethod.BE	Discretisation method
Saturation
Boolean	AntiWindup (from Controller)	false	Flag that enables the antiwindup feature
Real	CSmin (from Controller)	0	minimum value of the CS
Real	CSmax (from Controller)	1	maximum value of the CS
Initialisation
Real	CS_start (from Controller)	0	output initial value
Parameters
Real	Kp	5	Proportional gain
Real	Ti	1	Integral time

Connectors

Type	Name	Description
Modelica.Blocks.Interfaces.RealInput	TR (from Controller)	Track Reference signal
Modelica.Blocks.Interfaces.BooleanInput	TS (from Controller)	Track Switch signal
Modelica.Blocks.Interfaces.RealInput	BIAS (from Controller)	Bias
Modelica.Blocks.Interfaces.RealInput	SP (from Controller)	Set Point signal
Modelica.Blocks.Interfaces.RealOutput	CS (from Controller)	Control signal
Modelica.Blocks.Interfaces.RealInput	PV (from Controller)	Process Variable signal
Modelica.Blocks.Interfaces.BooleanInput	ATreq (from Controller)	Auto Tuning request
Modelica.Blocks.Interfaces.BooleanOutput	satHI (from Controller)
Modelica.Blocks.Interfaces.BooleanOutput	satLOW (from Controller)
Modelica.Blocks.Interfaces.RealInput	Kp_GS
Modelica.Blocks.Interfaces.RealInput	Ti_GS

Components

Type	Name	Description
Real	bias (from Controller)	bias signal
Real	tr (from Controller)	track reference value
Boolean	ts (from Controller)	track reference signal
Boolean	at_req (from Controller)	auto tuning enabling signal
Boolean	satHigh (from Controller)	High saturation signal
Boolean	satLow (from Controller)	Low saturation signal
Real	Ti_act	Actual integral time
Real	Kp_act	Actual proportianal gain
Real	FBout	output (and state) of the feedback block 1/(1+sTi)
Real	cs	Pre-biased Control Signal
Real	satin	input of the saturation block

Revisions

Industrial Control Systems (v 1.0.0) : April-May 2012