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()`.

  • 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.