Swerve Sürüş Odometrisi

Bir kullanıcı gerçekleştirmek için swerve sürücü kinematik sınıflarını kullanabilir odometry. WPILib, sahada bir Swerve sürüş robotunun konumunu izlemek için kullanılabilecek bir SwerveDriveOdometry sınıfı içerir.

Not

Bu yöntem yalnızca kodlayıcılar ve bir jiroskop kullandığından, robotun sahadaki konumunun tahmini, özellikle oyun sırasında diğer robotlarla temas kurduğunda zamanla kayacaktır. Bununla birlikte, odometri genellikle özerk dönemde çok doğrudur.

Odometri nesnesini oluşturma

The SwerveDriveOdometry<int NumModules> class constructor requires one template argument (only C++), three mandatory arguments, and one optional argument. The template argument (only C++) is an integer representing the number of swerve modules.

The mandatory arguments are:

  • The kinematics object that represents your swerve drive (as a SwerveDriveKinematics instance)

  • The angle reported by your gyroscope (as a Rotation2d)

  • The initial positions of the swerve modules (as an array of SwerveModulePosition). In Java, this must be constructed with each wheel position in meters. In C++, the units library must be used to represent your wheel positions. It is important that the order in which you pass the SwerveModulePosition objects is the same as the order in which you created the kinematics object.

The fourth optional argument is the starting pose of your robot on the field (as a Pose2d). By default, the robot will start at x = 0, y = 0, theta = 0.

Not

0 degrees / radians represents the robot angle when the robot is facing directly toward your opponent’s alliance station. As your robot turns to the left, your gyroscope angle should increase. The Gyro interface supplies getRotation2d/GetRotation2d that you can use for this purpose. See Coordinate System for more information about the coordinate system.

// Locations for the swerve drive modules relative to the robot center.
Translation2d m_frontLeftLocation = new Translation2d(0.381, 0.381);
Translation2d m_frontRightLocation = new Translation2d(0.381, -0.381);
Translation2d m_backLeftLocation = new Translation2d(-0.381, 0.381);
Translation2d m_backRightLocation = new Translation2d(-0.381, -0.381);

// Creating my kinematics object using the module locations
SwerveDriveKinematics m_kinematics = new SwerveDriveKinematics(
  m_frontLeftLocation, m_frontRightLocation, m_backLeftLocation, m_backRightLocation
);

// Creating my odometry object from the kinematics object and the initial wheel positions.
// Here, our starting pose is 5 meters along the long end of the field and in the
// center of the field along the short end, facing the opposing alliance wall.
SwerveDriveOdometry m_odometry = new SwerveDriveOdometry(
  m_kinematics, m_gyro.getRotation2d(),
  new SwerveModulePosition[] {
    m_frontLeftModule.getPosition(),
    m_frontRightModule.getPosition(),
    m_backLeftModule.getPosition(),
    m_backRightModule.getPosition()
  }, new Pose2d(5.0, 13.5, new Rotation2d()));

// Locations for the swerve drive modules relative to the robot center.
frc::Translation2d m_frontLeftLocation{0.381_m, 0.381_m};
frc::Translation2d m_frontRightLocation{0.381_m, -0.381_m};
frc::Translation2d m_backLeftLocation{-0.381_m, 0.381_m};
frc::Translation2d m_backRightLocation{-0.381_m, -0.381_m};

// Creating my kinematics object using the module locations.
frc::SwerveDriveKinematics<4> m_kinematics{
  m_frontLeftLocation, m_frontRightLocation,
  m_backLeftLocation, m_backRightLocation
};

// Creating my odometry object from the kinematics object. Here,
// our starting pose is 5 meters along the long end of the field and in the
// center of the field along the short end, facing forward.
frc::SwerveDriveOdometry<4> m_odometry{m_kinematics, m_gyro.GetRotation2d(),
  {m_frontLeft.GetPosition(), m_frontRight.GetPosition(),
  m_backLeft.GetPosition(), m_backRight.GetPosition()},
  frc::Pose2d{5_m, 13.5_m, 0_rad}};

# Python requires using the right class for the number of modules you have
# For both the Kinematics and Odometry classes

from wpimath.geometry import Translation2d
from wpimath.kinematics import SwerveDrive4Kinematics
from wpimath.kinematics import SwerveDrive4Odometry
from wpimath.geometry import Pose2d
from wpimath.geometry import Rotation2d

class MyRobot:
  def robotInit(self):
    # Locations for the swerve drive modules relative to the robot center.
    frontLeftLocation = Translation2d(0.381, 0.381)
    frontRightLocation = Translation2d(0.381, -0.381)
    backLeftLocation = Translation2d(-0.381, 0.381)
    backRightLocation = Translation2d(-0.381, -0.381)

    # Creating my kinematics object using the module locations
    self.kinematics = SwerveDrive4Kinematics(
      frontLeftLocation, frontRightLocation, backLeftLocation, backRightLocation
    )

    # Creating my odometry object from the kinematics object and the initial wheel positions.
    # Here, our starting pose is 5 meters along the long end of the field and in the
    # center of the field along the short end, facing the opposing alliance wall.
    self.odometry = SwerveDrive4Odometry(
      self.kinematics, self.gyro.getRotation2d(),
      (
        self.frontLeftModule.getPosition(),
        self.frontRightModule.getPosition(),
        self.backLeftModule.getPosition(),
        self.backRightModule.getPosition()
      ),
      Pose2d(5.0, 13.5, Rotation2d()))

Robot duruşunu güncelleme

The update method of the odometry class updates the robot position on the field. The update method takes in the gyro angle of the robot, along with an array of SwerveModulePosition objects. It is important that the order in which you pass the SwerveModulePosition objects is the same as the order in which you created the kinematics object.

Bu update metodu periyodik olarak, tercihen periodic() metodunda bir Subsystem ile çağrılmalıdır. update metodu, robotun yeni güncellenmiş pozunu döndürür.

@Override
public void periodic() {
  // Get the rotation of the robot from the gyro.
  var gyroAngle = m_gyro.getRotation2d();

  // Update the pose
  m_pose = m_odometry.update(gyroAngle,
    new SwerveModulePosition[] {
      m_frontLeftModule.getPosition(), m_frontRightModule.getPosition(),
      m_backLeftModule.getPosition(), m_backRightModule.getPosition()
    });
}

void Periodic() override {
  // Get the rotation of the robot from the gyro.
  frc::Rotation2d gyroAngle = m_gyro.GetRotation2d();

  // Update the pose
  m_pose = m_odometry.Update(gyroAngle,
    {
      m_frontLeftModule.GetPosition(), m_frontRightModule.GetPosition(),
      m_backLeftModule.GetPosition(), m_backRightModule.GetPosition()
    };
  )
}

def periodic(self):
  # Get the rotation of the robot from the gyro.
  self.gyroAngle = self.gyro.getRotation2d()

  # Update the pose
  self.pose = self.odometry.update(self.gyroAngle,
      self.frontLeftModule.getPosition(), self.frontRightModule.getPosition(),
      self.backLeftModule.getPosition(), self.backRightModule.getPosition()
  )

Robot Duruşunu Sıfırlama

The robot pose can be reset via the resetPosition method. This method accepts three arguments: the current gyro angle, an array of the current module positions (as in the constructor and update method), and the new field-relative pose.

Önemli

If at any time, you decide to reset your gyroscope or wheel encoders, the resetPosition method MUST be called with the new gyro angle and wheel encoder positions.

Not

The implementation of getPosition() / GetPosition() above is left to the user. The idea is to get the module position (distance and angle) from each module. For a full example, see here: C++ / Java / Python

In addition, the GetPose (C++) / getPoseMeters (Java / Python) methods can be used to retrieve the current robot pose without an update.