Odometry.h

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// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
 
#pragma once
 
#include <wpi/SymbolExports.h>
 
#include "frc/geometry/Pose2d.h"
#include "frc/geometry/Rotation2d.h"
#include "frc/geometry/Translation2d.h"
#include "frc/kinematics/Kinematics.h"
 
namespace frc {
 
/**
 * Class for odometry. Robot code should not use this directly- Instead, use the
 * particular type for your drivetrain (e.g., DifferentialDriveOdometry).
 * Odometry allows you to track the robot's position on the field over a course
 * of a match using readings from your wheel encoders.
 *
 * Teams can use odometry during the autonomous period for complex tasks like
 * path following. Furthermore, odometry can be used for latency compensation
 * when using computer-vision systems.
 *
 * @tparam WheelSpeeds Wheel speeds type.
 * @tparam WheelPositions Wheel positions type.
 */
template <typename WheelSpeeds, typename WheelPositions>
class WPILIB_DLLEXPORT Odometry {
 public:
  /**
   * Constructs an Odometry object.
   *
   * @param kinematics The kinematics for your drivetrain.
   * @param gyroAngle The angle reported by the gyroscope.
   * @param wheelPositions The current distances measured by each wheel.
   * @param initialPose The starting position of the robot on the field.
   */
  explicit Odometry(const Kinematics<WheelSpeeds, WheelPositions>& kinematics,
                    const Rotation2d& gyroAngle,
                    const WheelPositions& wheelPositions,
                    const Pose2d& initialPose = Pose2d{})
      : m_kinematics(kinematics),
        m_pose(initialPose),
        m_previousWheelPositions(wheelPositions) {
    m_previousAngle = m_pose.Rotation();
    m_gyroOffset = (-gyroAngle).RotateBy(m_pose.Rotation());
  }
 
  /**
   * Resets the robot's position on the field.
   *
   * The gyroscope angle does not need to be reset here on the user's robot
   * code. The library automatically takes care of offsetting the gyro angle.
   *
   * @param gyroAngle The angle reported by the gyroscope.
   * @param wheelPositions The current distances measured by each wheel.
   * @param pose The position on the field that your robot is at.
   */
  void ResetPosition(const Rotation2d& gyroAngle,
                     const WheelPositions& wheelPositions, const Pose2d& pose) {
    m_pose = pose;
    m_previousAngle = pose.Rotation();
    m_gyroOffset = (-gyroAngle).RotateBy(m_pose.Rotation());
    m_previousWheelPositions = wheelPositions;
  }
 
  /**
   * Resets the pose.
   *
   * @param pose The pose to reset to.
   */
  void ResetPose(const Pose2d& pose) {
    m_gyroOffset =
        m_gyroOffset.RotateBy(-m_pose.Rotation()).RotateBy(pose.Rotation());
    m_pose = pose;
    m_previousAngle = pose.Rotation();
  }
 
  /**
   * Resets the translation of the pose.
   *
   * @param translation The translation to reset to.
   */
  void ResetTranslation(const Translation2d& translation) {
    m_pose = Pose2d{translation, m_pose.Rotation()};
  }
 
  /**
   * Resets the rotation of the pose.
   *
   * @param rotation The rotation to reset to.
   */
  void ResetRotation(const Rotation2d& rotation) {
    m_gyroOffset = m_gyroOffset.RotateBy(m_pose.Rotation()).RotateBy(rotation);
    m_pose = Pose2d{m_pose.Translation(), rotation};
    m_previousAngle = rotation;
  }
 
  /**
   * Returns the position of the robot on the field.
   * @return The pose of the robot.
   */
  const Pose2d& GetPose() const { return m_pose; }
 
  /**
   * Updates the robot's position on the field using forward kinematics and
   * integration of the pose over time. This method takes in an angle parameter
   * which is used instead of the angular rate that is calculated from forward
   * kinematics, in addition to the current distance measurement at each wheel.
   *
   * @param gyroAngle The angle reported by the gyroscope.
   * @param wheelPositions The current distances measured by each wheel.
   *
   * @return The new pose of the robot.
   */
  const Pose2d& Update(const Rotation2d& gyroAngle,
                       const WheelPositions& wheelPositions) {
    auto angle = gyroAngle.RotateBy(m_gyroOffset);
 
    auto twist =
        m_kinematics.ToTwist2d(m_previousWheelPositions, wheelPositions);
    twist.dtheta = (angle - m_previousAngle).Radians();
 
    auto newPose = m_pose.Exp(twist);
 
    m_previousAngle = angle;
    m_previousWheelPositions = wheelPositions;
    m_pose = {newPose.Translation(), angle};
 
    return m_pose;
  }
 
 private:
  const Kinematics<WheelSpeeds, WheelPositions>& m_kinematics;
  Pose2d m_pose;
 
  WheelPositions m_previousWheelPositions;
 
  // Always equal to m_pose.Rotation()
  Rotation2d m_previousAngle;
 
  Rotation2d m_gyroOffset;
};
 
}  // namespace frc