Class ExponentialProfile

java.lang.Object

org.wpilib.math.trajectory.ExponentialProfile

public class ExponentialProfile
extends Object

A exponential curve-shaped velocity profile.

While this class can be used for a profiled movement from start to finish, the intended usage is to filter a reference's dynamics based on state-space model dynamics. To compute the reference obeying this constraint, do the following.

Initialization:

ExponentialProfile.Constraints constraints =
  ExponentialProfile.Constraints.fromCharacteristics(kMaxV, kV, kA);
ExponentialProfile.State previousProfiledReference =
  new ExponentialProfile.State(initialReference, 0.0);
ExponentialProfile profile = new ExponentialProfile(constraints);

Run on update:

previousProfiledReference =
profile.calculate(timeSincePreviousUpdate, previousProfiledReference, unprofiledReference);

where `unprofiledReference` is free to change between calls. Note that when the unprofiled reference is within the constraints, `calculate()` returns the unprofiled reference unchanged.

Otherwise, a timer can be started to provide monotonic values for `calculate()` and to determine when the profile has completed via `isFinished()`.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	ExponentialProfile.Constraints	Profile constraints.
static class	ExponentialProfile.ProfileTiming	Profile timing.
static class	ExponentialProfile.State	Profile state.

Constructor Summary

Constructors

Constructor	Description
ExponentialProfile(ExponentialProfile.Constraints constraints)	Constructs an ExponentialProfile.

Method Summary

Modifier and Type	Method	Description
ExponentialProfile.State	calculate(double t, ExponentialProfile.State current, ExponentialProfile.State goal)	Calculates the position and velocity for the profile at a time t where the current state is at time t = 0.
ExponentialProfile.State	calculateInflectionPoint(ExponentialProfile.State current, ExponentialProfile.State goal)	Calculates the point after which the fastest way to reach the goal state is to apply input in the opposite direction.
ExponentialProfile.ProfileTiming	calculateProfileTiming(ExponentialProfile.State current, ExponentialProfile.State goal)	Calculates the time it will take for this profile to reach the inflection point, and the time it will take for this profile to reach the goal state.
double	timeLeftUntil(ExponentialProfile.State current, ExponentialProfile.State goal)	Calculates the time it will take for this profile to reach the goal state.

Methods inherited from class Object

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

Constructor Details

ExponentialProfile

public ExponentialProfile(ExponentialProfile.Constraints constraints)

Constructs an ExponentialProfile.

Parameters:

constraints - The constraints on the profile, like maximum input.

Method Details

calculate

public ExponentialProfile.State calculate(double t,
 ExponentialProfile.State current,
 ExponentialProfile.State goal)

Calculates the position and velocity for the profile at a time t where the current state is at time t = 0.

Parameters:

t - How long to advance from the current state toward the desired state.

current - The current state.

goal - The desired state when the profile is complete.

Returns:

The position and velocity of the profile at time t.

calculateInflectionPoint

public ExponentialProfile.State calculateInflectionPoint(ExponentialProfile.State current,
 ExponentialProfile.State goal)

Calculates the point after which the fastest way to reach the goal state is to apply input in the opposite direction.

Parameters:

current - The current state.

goal - The desired state when the profile is complete.

Returns:

The position and velocity of the profile at the inflection point.

timeLeftUntil

public double timeLeftUntil(ExponentialProfile.State current,
 ExponentialProfile.State goal)

Calculates the time it will take for this profile to reach the goal state.

Parameters:

current - The current state.

goal - The desired state when the profile is complete.

Returns:

The total duration of this profile.

calculateProfileTiming

public ExponentialProfile.ProfileTiming calculateProfileTiming(ExponentialProfile.State current,
 ExponentialProfile.State goal)

Calculates the time it will take for this profile to reach the inflection point, and the time it will take for this profile to reach the goal state.

Parameters:

current - The current state.

goal - The desired state when the profile is complete.

Returns:

The timing information for this profile.