Class PidController

Proporitional-Integral-Derivative(PID) controller

that supports

first and second order low pass filtering of process variable
anti-windup
bumpless transfer between auto and manual mode
"warmstarting" -bumpless startup
feedforward
scaling of input and output values
gain scheduling of Kp
gain scheduling of Ti
"kicking" as is usually applied to compressor recycling controllers/anti-surge
min select/max select (also referred to as high select or low select: (multiple pid-controllers controlling the same output switch between auto and tracking mode)

By design decision, this class should be kept relativly simple in terms of coding patterns, so that it is possible to hand-port this class to other languages (c++/c/Structured Text/Labview/Matlab etc). To simulate PID-control, use the wrapper class PIDModel, as it wraps this class and impelments the ISimulatableModel interface needed to simulate with ProcessSimulator

PidModel

Inheritance

object

PidController

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: TimeSeriesAnalysis.Dynamic

Assembly: TimeSeriesAnalysis.dll

Syntax

public class PidController

Constructors

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PidController(double, double, double, double, double)

Constructor

Declaration

public PidController(double TimeBase_s, double Kp = 1, double Ti = 50, double Td = 0, double nanValue = -9999)

Parameters

Type	Name	Description
double	TimeBase_s
double	Kp
double	Ti
double	Td
double	nanValue

Methods

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GetControllerStatus()

Returns a status code, to determine if controller is in manual, auto or in tracking(relevant for split range controllers.)

Declaration

public PidStatus GetControllerStatus()

Returns

Type	Description
PidStatus

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GetFeedForward()

Get the feedforward parameters of the controller

Declaration

public PidFeedForward GetFeedForward()

Returns

Type	Description
PidFeedForward

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GetGainScehduling(PidGainScheduling)

Get the gain scheduling settings of the controller

Declaration

public PidGainScheduling GetGainScehduling(PidGainScheduling gainSchedulingObj)

Parameters

Type	Name	Description
PidGainScheduling	gainSchedulingObj

Returns

Type	Description
PidGainScheduling

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GetScaling()

Get the object that contains scaling information

Declaration

public PidScaling GetScaling()

Returns

Type	Description
PidScaling

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GetTimeBase()

Sets the length of time in seconds between each iteration of the controller, i.e. the "clock time" or "time base". This is very important to set correctly for the controller to function properly. Normally the clock time is set only once during intalization.

Declaration

public double GetTimeBase()

Returns

Type	Description
double

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GetTrackingCutoff()

Get the tracking cutoff parameter

Declaration

public double GetTrackingCutoff()

Returns

Type	Description
double

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GetTrackingOffset()

Returns the tracking offset of the controller, the offset that a non-active controller will add or subtract from its output when inactive in a split range control scheme

Declaration

public double GetTrackingOffset()

Returns

Type	Description
double

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GetUIfInAuto()

Returns the value of the output u that the controller would give if it was in auto. This is useful when considering turning on a controller that is in manual to see that the controller gives a sensible output. Call "iterate" first to update the internals of the controller.

Declaration

public double GetUIfInAuto()

Returns

Type	Description
double

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GetUWithoutTracking()

Split range controllers add an offset to the output u for inactive or "tracking" controllers. This function returns the "raw" u without tracking, which can be useful for initalizing simulations with split range control.

Declaration

public double GetUWithoutTracking()

Returns

Type	Description
double

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Iterate(double, double, double?, double?, double?)

Calculates the next u[k] output of the controller given the most recent process value and setpoint value, and optionally also including the tracking signal (only applicable if this is a split range controller) and optionally the gainScehduling variable if controller is to gain-schedule

Declaration

public double Iterate(double y_process_abs, double y_set_abs, double? uTrackSignal = null, double? gainSchedulingVariable = null, double? feedForwardVariable = null)

Parameters

Type	Name	Description
double	y_process_abs
double	y_set_abs
double?	uTrackSignal
double?	gainSchedulingVariable
double?	feedForwardVariable

Returns

Type	Description
double

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Iterate(double[], double[], double[])

Calculates an entire output vector u given vector of processes and setpoints (and optionally a tracking signal for split range) This method is useful for back-testing against historic data.

Declaration

public double[] Iterate(double[] y_process_abs, double[] y_set_abs, double[] uTrackSignal = null)

Parameters

Type	Name	Description
double[]	y_process_abs
double[]	y_set_abs
double[]	uTrackSignal

Returns

Type	Description
double[]

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SetAntiSurgeParams(PidAntiSurgeParams)

Sets the anti-surge "kick" paramters of the controller

Declaration

public void SetAntiSurgeParams(PidAntiSurgeParams antiSurgeParams)

Parameters

Type	Name	Description
PidAntiSurgeParams	antiSurgeParams

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SetAutoMode()

Set the control to autoamtic mode (i.e. u varies based on inputs and settings) (use SetManualMode to switch back)

Declaration

public void SetAutoMode()

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SetFeedForward(PidFeedForward)

Set the feedforward of the controller Re-calling this setter to update

Declaration

public void SetFeedForward(PidFeedForward feedForwardObj)

Parameters

Type	Name	Description
PidFeedForward	feedForwardObj

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SetGainScheduling(PidGainScheduling)

Set the gain scheduling of the controller (by default controller has no gain-scheduling) Re-calling this setter to update gain-scheduling

Declaration

public void SetGainScheduling(PidGainScheduling gainSchedulingObj)

Parameters

Type	Name	Description
PidGainScheduling	gainSchedulingObj

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SetKp(double)

Sets the Proportional gain(P) of the controller

Declaration

public void SetKp(double Kp)

Parameters

Type	Name	Description
double	Kp

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SetManualMode()

Set the control to manual mode (i.e. constant u). Will cause a bumpless transfer.(use SetAutoMode to switch back)

Declaration

public void SetManualMode()

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SetManualOutput(double)

Set the manual output of the model (will only be used if set)

Declaration

public void SetManualOutput(double uManual)

Parameters

Type	Name	Description
double	uManual

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SetPidFiltering(PidFilterParams)

Set the object that defines input filtering for the pid-controller

Declaration

public void SetPidFiltering(PidFilterParams pidFiltering)

Parameters

Type	Name	Description
PidFilterParams	pidFiltering

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SetScaling(PidScaling)

Gives a PIDscaling object that specifies how input and output is to be scaled.

Declaration

public void SetScaling(PidScaling pidScaling)

Parameters

Type	Name	Description
PidScaling	pidScaling

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SetTd(double)

Sets the differential(D) time contant of the controller in seconds

Declaration

public void SetTd(double Td_seconds)

Parameters

Type	Name	Description
double	Td_seconds

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SetTi(double)

Sets the Integral(I) time contant of the controller in seconds

Declaration

public void SetTi(double Ti_seconds)

Parameters

Type	Name	Description
double	Ti_seconds

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SetTrackingOffset(double, double)

Set the offset that is to be added or subtracte to a split range controller that is inactive or tracking. If this value is above zero, then the controller is MIN SELECT, if this value is negative then the controller is assumed MAX SELECT if this vlaue is zero, then trakcking will not work properly as controller will be unable to determine if its output was selected by looking at the tracking signal.

Declaration

public void SetTrackingOffset(double uTrackingOffset, double uTrackingCutoff = 0.5)

Parameters

Type	Name	Description
double	uTrackingOffset
double	uTrackingCutoff

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SetU0ForPcontrol(double)

For proportional-only controllers (P-controllers), a u0 offset to be added to u is specified by this method.

Declaration

public void SetU0ForPcontrol(double u0)

Parameters

Type	Name	Description
double	u0

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WarmStart(double, double, double)

Initalizes the controller internal state(integral term) to be steady at the given process value and output value, useful to avoid bumps when staring controller

Declaration

public void WarmStart(double y_process_abs, double y_set_abs, double u_abs)

Parameters

Type	Name	Description
double	y_process_abs
double	y_set_abs
double	u_abs