vona.time

Class TrapezoidInterpolator

java.lang.Object

vona.time.Interpolator

vona.time.TrapezoidInterpolator

public class TrapezoidInterpolator
extends Interpolator

Vona's utils: a trapezoid interpolator.

This extends Interpolator to follow trapezoid trajectories.

The trajectory may be specified in two ways:

• by giving a total Interpolator.duration and accelFraction, the fraction of that time that should be spent ramping up at start and down at end
• by giving a maxSpeed(vona.time.Clock, double, double, double, double) to use for the constant-speed section and a accelFraction

The various parameters are related to each other according to the following equations:

 maxVelocity = accel*accelFraction*duration

 distance = accel*(accelFraction*duration)^2 + (1-2*accelFraction)*duration*maxVelocity
 

Copyright (C) 2004 Marsette A. Vona, III

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

Author:

Marsette (Marty) A. Vona, III

Field Summary

Fields

Modifier and Type	Field and Description
double	accel The acceleration during ramp up/down.
double	accelDistance Distance traveled accelerating.
double	accelFraction Fraction in [0.0 0.5) to spend accelerating at the start and decelerating at the end (constant speed fraction is 1.0-2.0*accelFraction).
double	accelTime Time spent accelerating.
(package private) static java.lang.String	cvsid CVS id.
static double	DEFAULT_ACCEL_FRACTION Default accel fraction.
double	maxVelocity The velocity during the constant-speed phase.

Fields inherited from class vona.time.Interpolator

clock, distance, duration, end, start, startTime, wallClock

Constructor Summary

Constructors

Constructor and Description
TrapezoidInterpolator(Clock clock, double start, double end, double duration) Covers TrapezoidInterpolator(Clock, double, double, double, double) but always uses DEFAULT_ACCEL_FRACTION.
TrapezoidInterpolator(Clock clock, double start, double end, double duration, double accelFraction) Create a new TrapezoidInterpolator.
TrapezoidInterpolator(double start, double end, double duration) Covers TrapezoidInterpolator(Clock, double, double, double) but always uses Interpolator.wallClock.
TrapezoidInterpolator(double start, double end, double duration, double accelFraction) Covers TrapezoidInterpolator(Clock, double, double, double, double) but always uses Interpolator.wallClock.

Method Summary

Methods

Modifier and Type	Method and Description
protected double	currentValue(double when) Hook for subclasses to implement different interpolation schemes.
static TrapezoidInterpolator	fixedDuration(Clock clock, double start, double end, double duration) Factory method to make a fixed-duration TrapezoidInterpolator.
static TrapezoidInterpolator	fixedDuration(Clock clock, double start, double end, double duration, double accelFraction) Factory method to make a fixed-duration TrapezoidInterpolator.
static TrapezoidInterpolator	fixedDuration(double start, double end, double duration) Factory method to make a fixed-duration TrapezoidInterpolator.
static TrapezoidInterpolator	fixedDuration(double start, double end, double duration, double accelFraction) Factory method to make a fixed-duration TrapezoidInterpolator.
static double	getDuration(double start, double end, double maxSpeed) Covers getDuration(double, double, double, double) but always uses DEFAULT_ACCEL_FRACTION.
static double	getDuration(double start, double end, double maxSpeed, double accelFraction) Compute a duration given maxSpeed(vona.time.Clock, double, double, double, double) and accelFraction.
static TrapezoidInterpolator	maxSpeed(Clock clock, double start, double end, double maxSpeed) Factory method to make a maximum speed TrapezoidInterpolator.
static TrapezoidInterpolator	maxSpeed(Clock clock, double start, double end, double maxSpeed, double accelFraction) Factory method to make a maximum speed TrapezoidInterpolator.
static TrapezoidInterpolator	maxSpeed(double start, double end, double maxSpeed) Factory method to make a maximum speed TrapezoidInterpolator.
static TrapezoidInterpolator	maxSpeed(double start, double end, double maxSpeed, double accelFraction) Factory method to make a maximum speed TrapezoidInterpolator.

Methods inherited from class vona.time.Interpolator

currentValue, reset

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_ACCEL_FRACTION

public static final double DEFAULT_ACCEL_FRACTION

Default accel fraction.

See Also:

Constant Field Values

cvsid

static final java.lang.String cvsid

CVS id.

See Also:

Constant Field Values

accelFraction

public final double accelFraction

Fraction in [0.0 0.5) to spend accelerating at the start and decelerating at the end (constant speed fraction is 1.0-2.0*accelFraction).

accel

public final double accel

The acceleration during ramp up/down.

maxVelocity

public final double maxVelocity

The velocity during the constant-speed phase.

accelTime

public final double accelTime

Time spent accelerating.

accelDistance

public final double accelDistance

Distance traveled accelerating.

Constructor Detail

TrapezoidInterpolator

public TrapezoidInterpolator(Clock clock,
                     double start,
                     double end,
                     double duration,
                     double accelFraction)

Create a new TrapezoidInterpolator.

Parameters:

clock - the time base, if null then use Interpolator.wallClock

start - the initial value

end - the final falue

duration - the duration in seconds according to clock

accelFraction - a fraction in [0.0 0.5) to spend accelerating at the start and decelerating at the end (constant speed fraction is 1.0-2.0*accelFraction)

TrapezoidInterpolator

public TrapezoidInterpolator(double start,
                     double end,
                     double duration,
                     double accelFraction)

Covers TrapezoidInterpolator(Clock, double, double, double, double) but always uses Interpolator.wallClock.

TrapezoidInterpolator

public TrapezoidInterpolator(Clock clock,
                     double start,
                     double end,
                     double duration)

Covers TrapezoidInterpolator(Clock, double, double, double, double) but always uses DEFAULT_ACCEL_FRACTION.

TrapezoidInterpolator

public TrapezoidInterpolator(double start,
                     double end,
                     double duration)

Covers TrapezoidInterpolator(Clock, double, double, double) but always uses Interpolator.wallClock.

Method Detail

getDuration

public static double getDuration(double start,
                 double end,
                 double maxSpeed,
                 double accelFraction)

Compute a duration given maxSpeed(vona.time.Clock, double, double, double, double) and accelFraction.

Parameters:

start - the initial value

end - the final falue

accelFraction - a fraction in [0.0 0.5) to spend accelerating at the start and decelerating at the end (constant speed fraction is 1.0-2.0*accelFraction)

getDuration

public static double getDuration(double start,
                 double end,
                 double maxSpeed)

Covers getDuration(double, double, double, double) but always uses DEFAULT_ACCEL_FRACTION.

fixedDuration

public static TrapezoidInterpolator fixedDuration(Clock clock,
                                  double start,
                                  double end,
                                  double duration,
                                  double accelFraction)

Factory method to make a fixed-duration TrapezoidInterpolator.

Covers TrapezoidInterpolator(Clock, double, double, double, double).

fixedDuration

public static TrapezoidInterpolator fixedDuration(double start,
                                  double end,
                                  double duration,
                                  double accelFraction)

Factory method to make a fixed-duration TrapezoidInterpolator.

Covers fixedDuration(Clock, double, double, double, double) but always uses Interpolator.wallClock.

fixedDuration

public static TrapezoidInterpolator fixedDuration(Clock clock,
                                  double start,
                                  double end,
                                  double duration)

Factory method to make a fixed-duration TrapezoidInterpolator.

Covers TrapezoidInterpolator(Clock, double, double, double).

fixedDuration

public static TrapezoidInterpolator fixedDuration(double start,
                                  double end,
                                  double duration)

Factory method to make a fixed-duration TrapezoidInterpolator.

Covers fixedDuration(Clock, double, double, double) but always uses Interpolator.wallClock.

maxSpeed

public static TrapezoidInterpolator maxSpeed(Clock clock,
                             double start,
                             double end,
                             double maxSpeed,
                             double accelFraction)

Factory method to make a maximum speed TrapezoidInterpolator.

Covers TrapezoidInterpolator(Clock, double, double, double, double) but computes duration with getDuration(double, double, double, double).

maxSpeed

public static TrapezoidInterpolator maxSpeed(double start,
                             double end,
                             double maxSpeed,
                             double accelFraction)

Factory method to make a maximum speed TrapezoidInterpolator.

Covers maxSpeed(Clock, double, double, double, double) but always uses Interpolator.wallClock.

maxSpeed

public static TrapezoidInterpolator maxSpeed(Clock clock,
                             double start,
                             double end,
                             double maxSpeed)

Factory method to make a maximum speed TrapezoidInterpolator.

Covers TrapezoidInterpolator(Clock, double, double, double) but computes duration with getDuration(double, double, double, double).

maxSpeed

public static TrapezoidInterpolator maxSpeed(double start,
                             double end,
                             double maxSpeed)

Factory method to make a maximum speed TrapezoidInterpolator.

Covers maxSpeed(Clock, double, double, double) but always uses Interpolator.wallClock.

currentValue

protected double currentValue(double when)

Hook for subclasses to implement different interpolation schemes.

Interpolator.currentValue() calls this to compute intermediate values between Interpolator.start and Interpolator.end.

This impl computes the trapezoid.

For when < accelTime computes ramp-up at accel.

Otherwise, for when < duration-accelTime computes const-ant-speed.

Otherwise computes ramp-down.

Overrides:

currentValue in class Interpolator

Parameters:

when - the time in seconds according to Interpolator.clock since the start of the interpolation

Returns:

the value of the interpolation at when