Package edu.wpi.first.wpilibj.trajectory

Class TrapezoidProfile

java.lang.Object

edu.wpi.first.wpilibj.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);
 

Run on update:

 TrapezoidProfile profile =
   new TrapezoidProfile(constraints, unprofiledReference, previousProfiledReference);
 previousProfiledReference = profile.calculate(timeSincePreviousUpdate);
 

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
static class	TrapezoidProfile.State

Constructor Summary

Constructors

Constructor	Description
TrapezoidProfile(TrapezoidProfile.Constraints constraints, TrapezoidProfile.State goal)	Construct a TrapezoidProfile.
TrapezoidProfile(TrapezoidProfile.Constraints constraints, TrapezoidProfile.State goal, TrapezoidProfile.State initial)	Construct a TrapezoidProfile.

Method Summary

Modifier and Type	Method	Description
TrapezoidProfile.State	calculate(double t)	Calculate the correct position and velocity for the profile at a time t where the beginning of the profile was 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, TrapezoidProfile.State goal, TrapezoidProfile.State initial)

Construct a TrapezoidProfile.

Parameters:

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

goal - The desired state when the profile is complete.

initial - The initial state (usually the current state).

TrapezoidProfile

public TrapezoidProfile(TrapezoidProfile.Constraints constraints, TrapezoidProfile.State goal)

Construct a TrapezoidProfile.

Parameters:

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

goal - The desired state when the profile is complete.

Method Details

calculate

public TrapezoidProfile.State calculate(double t)

Calculate the correct position and velocity for the profile at a time t where the beginning of the profile was at time t = 0.

Parameters:

t - The time since the beginning of the profile.

timeLeftUntil

public double timeLeftUntil(double target)

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

Parameters:

target - The target distance.

totalTime

public double totalTime()

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.