Package edu.wpi.first.math.trajectory

Class TrapezoidProfile

java.lang.Object

edu.wpi.first.math.trajectory.TrapezoidProfile

public class TrapezoidProfile
extends Object

A trapezoid-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 trapezoidal velocity constraints. To compute the reference obeying this constraint, do the following.

Initialization:

 TrapezoidProfile.Constraints constraints =
   new TrapezoidProfile.Constraints(kMaxV, kMaxA);
 TrapezoidProfile.State previousProfiledReference =
   new TrapezoidProfile.State(initialReference, 0.0);
 TrapezoidProfile profile = new TrapezoidProfile(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 class	TrapezoidProfile.Constraints	Profile constraints.
static class	TrapezoidProfile.State	Profile state.

Constructor Summary

Constructors

Constructor	Description
TrapezoidProfile(TrapezoidProfile.Constraints constraints)	Constructs a TrapezoidProfile.

Method Summary

Modifier and Type	Method	Description
TrapezoidProfile.State	calculate(double t, TrapezoidProfile.State current, TrapezoidProfile.State goal)	Calculates the position and velocity for the profile at a time t where the current state is at time t = 0.
boolean	isFinished(double t)	Returns true if the profile has reached the goal.
double	timeLeftUntil(double target)	Returns the time left until a target distance in the profile is reached.
double	totalTime()	Returns the total time the profile takes to reach the goal.

Methods inherited from class java.lang.Object

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

Constructor Details

TrapezoidProfile

public TrapezoidProfile(TrapezoidProfile.Constraints constraints)

Constructs a TrapezoidProfile.

Parameters:

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

Method Details

calculate

public TrapezoidProfile.State calculate(double t,
 TrapezoidProfile.State current,
 TrapezoidProfile.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.

timeLeftUntil

public double timeLeftUntil(double target)

Returns the time left until a target distance in the profile is reached.

Parameters:

target - The target distance.

Returns:

The time left until a target distance in the profile is reached.

totalTime

public double totalTime()

Returns the total time the profile takes to reach the goal.

Returns:

The total time the profile takes to reach the goal.

isFinished

public boolean isFinished(double t)

Returns true if the profile has reached the goal.

The profile has reached the goal if the time since the profile started has exceeded the profile's total time.

Parameters:

t - The time since the beginning of the profile.

Returns:

True if the profile has reached the goal.