util
Class PIDControl

java.lang.Object
  util.PropertyContainer
      util.PropertyResources
          util.PropertyBundles
              util.PIDControl

All Implemented Interfaces:

Cloneable, Initializable, LocalizedSupplying, PropertySupplying, ResourceSupplying

public class PIDControl
extends PropertyBundles

PID (Proportional-Integral-Differential) Controllers are basic applications in servo motor controls. If the difference between nominal and actual is denoted as an error e(t), the output of the PID controller, i.e. the required correction c(t) can be writtn as:

   c(t)=kp·e(t)+ki·∫e(t)dt+kd·de(t)/dt
   

The name PID comes from these three proportional constant, that are related to the signal itself, its integral, respectively differential with time. Determining the values of this three parameter is some science on its own.

This class allows basic access to PID-control. It allows registering of an Integrator and Differentiator. The three constants are provided in the PIDControl's properties. Calling the getCorrection() method evaluates the formular above and returns the c(t).

Nested Class Summary

static class

PIDControl.Test Test string representation.

Nested classes/interfaces inherited from class util.PropertyResources

PropertyResources.URLResource

Field Summary

private static double	DEFDIFFERENTIAL The default value of the differential constant.
private static Class	DEFDIFFERENTIATOR The default differentiator class .
private static double	DEFINTEGRAL The default value of the integral constant.
private static Class	DEFINTEGRATOR The default integrator class .
private static double	DEFLIMIT The default limit, zero=no limit.
private static double	DEFPROPORTIONAL The default value of the proportional constant.
private Differentiator	differentiate The differentiator to use.
private boolean	initialized True after the first error has been added.
private Integrator	integrate The integrator to use.
static String	KEY_DIFFERENTIAL The differential constant.
static String	KEY_DIFFERENTIATOR The class name of the differentiator.
static String	KEY_INTEGRAL The integral constant.
static String	KEY_INTEGRATOR The class name of the integrator.
static String	KEY_LIMIT The PID correction limit.
static String	KEY_PROPORTIONAL The proportional constant.
private double	lastoffset The last offset added, used for the proportional term.

Fields inherited from class util.PropertyBundles

KEY_LOCALECOUNTRY, KEY_LOCALELANGUAGE, KEY_RESOURCEBUNDLES

Fields inherited from class util.PropertyResources

applet, DEFURLUSECONFIG, DEFURLUSECURRENT, DEFURLUSEHOME, KEY_NOINITONCREATE, localurl, locate, POSTFIX_DIR, POSTFIX_EXT, POSTFIX_FILE, POSTFIX_LIST, POSTFIX_URL, urlset

Fields inherited from class util.PropertyContainer

KEY_LISTSEPARATOR, KEY_MAPKEYVALUECHAR, KEY_MAPSEPARATOR

Fields inherited from interface util.ResourceSupplying

KEY_URLRESOURCES, KEY_URLUSECONFIG, KEY_URLUSECURRENT, KEY_URLUSEHOME

Fields inherited from interface util.PropertySupplying

CONFIG, KEY_CLASS

Constructor Summary

PIDControl(Map<String,String> info)
Constructs a new PID-control.

PIDControl(String pid)
Convenience constructor allowing instantiation with a string like

Method Summary

void	addError(double offset) Adds an error signal in the equal time-step case.
void	addError(double t, double offset) Adds an error signal with a varying time-step.
void	clear() Clears the PID and allows for a new run.
double	getCorrection() Returns the correction to the signal as derived from previous offsets.
double	getDifferential() Sets the differential term.
double	getIntegral() Sets the integral term.
double	getProportional() Gets the proportinal term.
private static boolean	searchDouble(String key1, String keyset, Map<String,String> search, PropertySupplying where) Searches the map for a string representation of the key in the first argument, tries to convert this to a double and set this as the second string property in the property container.
void	setDifferential(double diff) Sets the differential term.
void	setIntegral(double integral) Sets the integral term.
void	setProportional(double prop) Sets the proportinal term.
String	toString() Returns the three main parameters of the pid as a string.

Methods inherited from class util.PropertyBundles

clone, getLocalized, getLocalized, getLocalizedString, getLocalizedString, loadResource

Methods inherited from class util.PropertyResources

createFrom, createFrom, createFrom, getApplet, getAsResources, getLocalClassLoader, getPropertiesToKey, getPropertiesToKey, getResource, getResourceAsStream, getResourceFromKey, getResources, init, keyCreate, keyCreate, loadAppletResource, reload, setApplet

Methods inherited from class util.PropertyContainer

augment, augment, augment, defaultBoolean, defaultChar, defaultDouble, defaultFloat, defaultInt, defaultLong, defaultObject, defaultObject, defaultProperties, defaultProperty, getAsBoolean, getAsChar, getAsDouble, getAsEnums, getAsFloat, getAsInt, getAsList, getAsLong, getAsMap, getAsMap, getAsObject, getAsObject, getProperties, getProperty, has, isNew, parseObject, reload, removeProperty, rescanned, setObject, setProperties, setProperty, stringProperties

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface util.ResourceSupplying

getResource, getResourceAsStream, getResources

Methods inherited from interface util.PropertySupplying

defaultBoolean, defaultChar, defaultDouble, defaultFloat, defaultInt, defaultLong, defaultObject, defaultObject, defaultProperties, defaultProperty, getAsBoolean, getAsChar, getAsDouble, getAsFloat, getAsInt, getAsList, getAsLong, getAsMap, getAsObject, getAsObject, getProperties, getProperty, has, parseObject, removeProperty, setObject, setProperty, stringProperties

Methods inherited from interface util.Initializable

init

Field Detail

KEY_PROPORTIONAL

public static final String KEY_PROPORTIONAL

The proportional constant.

See Also:

Constant Field Values

KEY_DIFFERENTIAL

public static final String KEY_DIFFERENTIAL

The differential constant.

See Also:

Constant Field Values

KEY_INTEGRAL

public static final String KEY_INTEGRAL

The integral constant.

See Also:

Constant Field Values

KEY_LIMIT

public static final String KEY_LIMIT

The PID correction limit. Corrections exceeding this are truncated.

See Also:

Constant Field Values

KEY_INTEGRATOR

public static final String KEY_INTEGRATOR

The class name of the integrator.

See Also:

Constant Field Values

KEY_DIFFERENTIATOR

public static final String KEY_DIFFERENTIATOR

The class name of the differentiator.

See Also:

Constant Field Values

DEFPROPORTIONAL

private static final double DEFPROPORTIONAL

The default value of the proportional constant.

See Also:

Constant Field Values

DEFDIFFERENTIAL

private static final double DEFDIFFERENTIAL

The default value of the differential constant.

See Also:

Constant Field Values

DEFINTEGRAL

private static final double DEFINTEGRAL

The default value of the integral constant.

See Also:

Constant Field Values

DEFLIMIT

private static final double DEFLIMIT

The default limit, zero=no limit.

See Also:

Constant Field Values

DEFINTEGRATOR

private static final Class DEFINTEGRATOR

The default integrator class .

DEFDIFFERENTIATOR

private static final Class DEFDIFFERENTIATOR

The default differentiator class .

lastoffset

private double lastoffset

The last offset added, used for the proportional term.

integrate

private Integrator integrate

The integrator to use.

differentiate

private Differentiator differentiate

The differentiator to use.

initialized

private boolean initialized

True after the first error has been added.

Constructor Detail

PIDControl

public PIDControl(String pid)

Convenience constructor allowing instantiation with a string like

P=0.5:I=0.2:D=0.0:L=20.

PIDControl

public PIDControl(Map<String,String> info)

Constructs a new PID-control. It is the user's responsibility to not call the getCorrection() method before enough differences had been added with addError(double) for the integrator/differentiator to work. Additionally, the user must be aware that the integrator/ differentiator supplied in the properties is compliant with the addError(double) method used, i.e. whether a fixed time-step or a (error-t) pair is used.

Method Detail

searchDouble

private static final boolean searchDouble(String key1,
                                          String keyset,
                                          Map<String,String> search,
                                          PropertySupplying where)

Searches the map for a string representation of the key in the first argument, tries to convert this to a double and set this as the second string property in the property container.

Returns:

True, if double was entered.

addError

public void addError(double offset)

Adds an error signal in the equal time-step case. It is the users responsibility to supply an integrator/differntiator that can work with equal step-size integration/differentiation. The default integrator and differentiator can only work with this method.

clear

public void clear()

Clears the PID and allows for a new run.

addError

public void addError(double t,
                     double offset)

Adds an error signal with a varying time-step. It is the users responsibility to supply an integrator/differntiator that can work with non-equal step-size integration/differentiation. The default integrator and differentiator can not work with this method.

getCorrection

public double getCorrection()

Returns the correction to the signal as derived from previous offsets. May not be called prior to adding enough offsets using the addError(double) method.

getProportional

public double getProportional()

Gets the proportinal term.

setProportional

public void setProportional(double prop)

Sets the proportinal term.

getDifferential

public double getDifferential()

Sets the differential term.

setDifferential

public void setDifferential(double diff)

Sets the differential term.

getIntegral

public double getIntegral()

Sets the integral term.

setIntegral

public void setIntegral(double integral)

Sets the integral term.

toString

public String toString()

Returns the three main parameters of the pid as a string.

Overrides:

toString in class PropertyContainer