stella.util

Class TelescopeAxis

java.lang.Object

util.PropertyContainer

stella.util.TelescopeAxis

All Implemented Interfaces:

Cloneable, PropertySupplying

public class TelescopeAxis
extends PropertyContainer

A telescope axis represents either axis on STELLA. It is used in PID-tuning to have a more realistic model for the telescope's reaction to a guider offset.
It simulates the axis movement considering a few cornerstones:

• If the guider sends an offset to the telescope, it will take a certain deadtime until the offset is actually pursued. This delay comes from the time to calculate the offset (read-out of guider-ccd, algorithms) within the guider, a time for the submission of a command via the network and last but not least there will always be a delay within the telescope motors itself. The total amount of this delay time is set with setDeadtime(double).
• During deadtime, the telescope will follow its last movement and the next offset it pursues is the offset sent with setDesiredOffset(double, double), not the desired offset plus movement during the deadtime.
• The telescope axis will follow roughly an S-curve movement. Thus, the SCurve class is utilized for the movement of the axis.
• If a new offset will become active during an ongoing movement of the telescope, the old position, velocity and acceleration will act as the boundary condition of the new movement.
• There is always only a single s-curve movement active, the 'old' one during deadtime and after it the new one.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TelescopeAxis.Randomize Tests the axis movement by a randomized offset.

Field Summary

Fields

Modifier and Type	Field and Description
private double	deadtime The deadtime of the movement.
private static double	DEFALPHA The default alpha value.
private static double	DEFBETA The default beta value.
private static double	DEFJERK The default jerk in degree/s^3.
static String	KEY_ALPHA The key to the alpha time-share of the S-curve.
static String	KEY_BETA The key to the beta time-share of the S-curve.
static String	KEY_JERK The key to the jerk of the S-curve.
private SCurve	movealong The old s-curve movement.
private SCurve	moveto The next active s-curve.
private double	switchover The time at which the new s-curve will become active.

Fields inherited from class util.PropertyContainer

KEY_LISTSEPARATOR, KEY_MAPKEYVALUECHAR, KEY_MAPSEPARATOR

Fields inherited from interface util.PropertySupplying

CONFIG, KEY_CLASS

Constructor Summary

Constructors

Constructor and Description
TelescopeAxis(Map prop) Constructs a new telescope axis object.

Method Summary

Modifier and Type	Method and Description
double	getAxisPosition(double tnow) Gets the telescope axis position at the time in question.
void	setDeadtime(double dead) Sets the deadtime.
void	setDesiredOffset(double offset, double tnow) Set the offset the axis should acquire.
void	setJerkConstant(double jerk) Sets the motor jerk.

Methods inherited from class util.PropertyContainer

augment, augment, augment, augment, augment, clone, 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, initProperties, isNew, parseObject, parseObject, reload, reload, removeProperty, requires, rescanned, setObject, setProperties, setProperty, stringProperties, toString

Methods inherited from class java.lang.Object

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

Field Detail

KEY_ALPHA

public static final String KEY_ALPHA

The key to the alpha time-share of the S-curve.

See Also:

Constant Field Values

KEY_BETA

public static final String KEY_BETA

The key to the beta time-share of the S-curve.

See Also:

Constant Field Values

KEY_JERK

public static final String KEY_JERK

The key to the jerk of the S-curve.

See Also:

Constant Field Values

DEFALPHA

private static final double DEFALPHA

The default alpha value.

See Also:

Constant Field Values

DEFBETA

private static final double DEFBETA

The default beta value.

See Also:

Constant Field Values

DEFJERK

private static final double DEFJERK

The default jerk in degree/s^3.

See Also:

Constant Field Values

deadtime

private double deadtime

The deadtime of the movement.

moveto

private SCurve moveto

The next active s-curve.

movealong

private SCurve movealong

The old s-curve movement.

switchover

private double switchover

The time at which the new s-curve will become active.

Constructor Detail

TelescopeAxis

public TelescopeAxis(Map prop)

Constructs a new telescope axis object.

Method Detail

setDeadtime

public void setDeadtime(double dead)

Sets the deadtime. This is the time out from the measurement of an offset until it gets active on the telescope axis. The deadtime should be set in seconds.

setJerkConstant

public void setJerkConstant(double jerk)

Sets the motor jerk. This is a property value as it is needed for the S-curve movement.

setDesiredOffset

public void setDesiredOffset(double offset,
                             double tnow)

Set the offset the axis should acquire.

Parameters:

offset - The offset the telescope should now follow.

tnow - The current time. This determines when the new offset will get active, at tnow plus deadtime.

getAxisPosition

public double getAxisPosition(double tnow)

Gets the telescope axis position at the time in question. First, we check if the old s-curve movement should be used. If so, query the SCurve.getDistance(double) method with the current time and return. If the time in question is over the switchover time for the first time, we query the telescope axis movealong object for the acceleration, velocity and distance at the switchover time. This are the BC's for the moveto object, which is then started at the switch time. The moveto object is now shifted to the movealong state, and distances are queried from it.