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.trajectory.constraint;
006
007import edu.wpi.first.math.geometry.Pose2d;
008import edu.wpi.first.math.kinematics.ChassisSpeeds;
009import edu.wpi.first.math.kinematics.DifferentialDriveKinematics;
010
011/**
012 * A class that enforces constraints on the differential drive kinematics. This can be used to
013 * ensure that the trajectory is constructed so that the commanded velocities for both sides of the
014 * drivetrain stay below a certain limit.
015 */
016public class DifferentialDriveKinematicsConstraint implements TrajectoryConstraint {
017  private final double m_maxSpeedMetersPerSecond;
018  private final DifferentialDriveKinematics m_kinematics;
019
020  /**
021   * Constructs a differential drive dynamics constraint.
022   *
023   * @param kinematics A kinematics component describing the drive geometry.
024   * @param maxSpeedMetersPerSecond The max speed that a side of the robot can travel at.
025   */
026  public DifferentialDriveKinematicsConstraint(
027      final DifferentialDriveKinematics kinematics, double maxSpeedMetersPerSecond) {
028    m_maxSpeedMetersPerSecond = maxSpeedMetersPerSecond;
029    m_kinematics = kinematics;
030  }
031
032  /**
033   * Returns the max velocity given the current pose and curvature.
034   *
035   * @param poseMeters The pose at the current point in the trajectory.
036   * @param curvatureRadPerMeter The curvature at the current point in the trajectory.
037   * @param velocityMetersPerSecond The velocity at the current point in the trajectory before
038   *     constraints are applied.
039   * @return The absolute maximum velocity.
040   */
041  @Override
042  public double getMaxVelocityMetersPerSecond(
043      Pose2d poseMeters, double curvatureRadPerMeter, double velocityMetersPerSecond) {
044    // Create an object to represent the current chassis speeds.
045    var chassisSpeeds =
046        new ChassisSpeeds(
047            velocityMetersPerSecond, 0, velocityMetersPerSecond * curvatureRadPerMeter);
048
049    // Get the wheel speeds and normalize them to within the max velocity.
050    var wheelSpeeds = m_kinematics.toWheelSpeeds(chassisSpeeds);
051    wheelSpeeds.desaturate(m_maxSpeedMetersPerSecond);
052
053    // Return the new linear chassis speed.
054    return m_kinematics.toChassisSpeeds(wheelSpeeds).vxMetersPerSecond;
055  }
056
057  /**
058   * Returns the minimum and maximum allowable acceleration for the trajectory given pose,
059   * curvature, and speed.
060   *
061   * @param poseMeters The pose at the current point in the trajectory.
062   * @param curvatureRadPerMeter The curvature at the current point in the trajectory.
063   * @param velocityMetersPerSecond The speed at the current point in the trajectory.
064   * @return The min and max acceleration bounds.
065   */
066  @Override
067  public MinMax getMinMaxAccelerationMetersPerSecondSq(
068      Pose2d poseMeters, double curvatureRadPerMeter, double velocityMetersPerSecond) {
069    return new MinMax();
070  }
071}