001// Copyright (c) FIRST and other WPILib contributors.
002// Open Source Software; you can modify and/or share it under the terms of
003// the WPILib BSD license file in the root directory of this project.
004
005package edu.wpi.first.math.controller;
006
007import edu.wpi.first.math.geometry.Pose2d;
008import edu.wpi.first.math.geometry.Rotation2d;
009import edu.wpi.first.math.kinematics.ChassisSpeeds;
010import edu.wpi.first.math.trajectory.Trajectory;
011import edu.wpi.first.math.util.Units;
012
013/**
014 * This holonomic drive controller can be used to follow trajectories using a holonomic drivetrain
015 * (i.e. swerve or mecanum). Holonomic trajectory following is a much simpler problem to solve
016 * compared to skid-steer style drivetrains because it is possible to individually control forward,
017 * sideways, and angular velocity.
018 *
019 * <p>The holonomic drive controller takes in one PID controller for each direction, forward and
020 * sideways, and one profiled PID controller for the angular direction. Because the heading dynamics
021 * are decoupled from translations, users can specify a custom heading that the drivetrain should
022 * point toward. This heading reference is profiled for smoothness.
023 */
024public class HolonomicDriveController {
025  private Pose2d m_poseError = new Pose2d();
026  private Rotation2d m_rotationError = new Rotation2d();
027  private Pose2d m_poseTolerance = new Pose2d();
028  private boolean m_enabled = true;
029
030  private final PIDController m_xController;
031  private final PIDController m_yController;
032  private final ProfiledPIDController m_thetaController;
033
034  private boolean m_firstRun = true;
035
036  /**
037   * Constructs a holonomic drive controller.
038   *
039   * @param xController A PID Controller to respond to error in the field-relative x direction.
040   * @param yController A PID Controller to respond to error in the field-relative y direction.
041   * @param thetaController A profiled PID controller to respond to error in angle.
042   */
043  public HolonomicDriveController(
044      PIDController xController, PIDController yController, ProfiledPIDController thetaController) {
045    m_xController = xController;
046    m_yController = yController;
047    m_thetaController = thetaController;
048    m_thetaController.enableContinuousInput(0, Units.degreesToRadians(360.0));
049  }
050
051  /**
052   * Returns true if the pose error is within tolerance of the reference.
053   *
054   * @return True if the pose error is within tolerance of the reference.
055   */
056  public boolean atReference() {
057    final var eTranslate = m_poseError.getTranslation();
058    final var eRotate = m_rotationError;
059    final var tolTranslate = m_poseTolerance.getTranslation();
060    final var tolRotate = m_poseTolerance.getRotation();
061    return Math.abs(eTranslate.getX()) < tolTranslate.getX()
062        && Math.abs(eTranslate.getY()) < tolTranslate.getY()
063        && Math.abs(eRotate.getRadians()) < tolRotate.getRadians();
064  }
065
066  /**
067   * Sets the pose error which is considered tolerance for use with atReference().
068   *
069   * @param tolerance The pose error which is tolerable.
070   */
071  public void setTolerance(Pose2d tolerance) {
072    m_poseTolerance = tolerance;
073  }
074
075  /**
076   * Returns the next output of the holonomic drive controller.
077   *
078   * @param currentPose The current pose, as measured by odometry or pose estimator.
079   * @param trajectoryPose The desired trajectory pose, as sampled for the current timestep.
080   * @param desiredLinearVelocityMetersPerSecond The desired linear velocity.
081   * @param desiredHeading The desired heading.
082   * @return The next output of the holonomic drive controller.
083   */
084  public ChassisSpeeds calculate(
085      Pose2d currentPose,
086      Pose2d trajectoryPose,
087      double desiredLinearVelocityMetersPerSecond,
088      Rotation2d desiredHeading) {
089    // If this is the first run, then we need to reset the theta controller to the current pose's
090    // heading.
091    if (m_firstRun) {
092      m_thetaController.reset(currentPose.getRotation().getRadians());
093      m_firstRun = false;
094    }
095
096    // Calculate feedforward velocities (field-relative).
097    double xFF = desiredLinearVelocityMetersPerSecond * trajectoryPose.getRotation().getCos();
098    double yFF = desiredLinearVelocityMetersPerSecond * trajectoryPose.getRotation().getSin();
099    double thetaFF =
100        m_thetaController.calculate(
101            currentPose.getRotation().getRadians(), desiredHeading.getRadians());
102
103    m_poseError = trajectoryPose.relativeTo(currentPose);
104    m_rotationError = desiredHeading.minus(currentPose.getRotation());
105
106    if (!m_enabled) {
107      return ChassisSpeeds.fromFieldRelativeSpeeds(xFF, yFF, thetaFF, currentPose.getRotation());
108    }
109
110    // Calculate feedback velocities (based on position error).
111    double xFeedback = m_xController.calculate(currentPose.getX(), trajectoryPose.getX());
112    double yFeedback = m_yController.calculate(currentPose.getY(), trajectoryPose.getY());
113
114    // Return next output.
115    return ChassisSpeeds.fromFieldRelativeSpeeds(
116        xFF + xFeedback, yFF + yFeedback, thetaFF, currentPose.getRotation());
117  }
118
119  /**
120   * Returns the next output of the holonomic drive controller.
121   *
122   * @param currentPose The current pose, as measured by odometry or pose estimator.
123   * @param desiredState The desired trajectory pose, as sampled for the current timestep.
124   * @param desiredHeading The desired heading.
125   * @return The next output of the holonomic drive controller.
126   */
127  public ChassisSpeeds calculate(
128      Pose2d currentPose, Trajectory.State desiredState, Rotation2d desiredHeading) {
129    return calculate(
130        currentPose, desiredState.poseMeters, desiredState.velocityMetersPerSecond, desiredHeading);
131  }
132
133  /**
134   * Enables and disables the controller for troubleshooting problems. When calculate() is called on
135   * a disabled controller, only feedforward values are returned.
136   *
137   * @param enabled If the controller is enabled or not.
138   */
139  public void setEnabled(boolean enabled) {
140    m_enabled = enabled;
141  }
142}