Differential Drive Odometrisi

Bir kullanıcı, odometry gerçekleştirmek için diferansiyel sürücü kinematik sınıflarını kullanabilir . WPILib, sahada diferansiyel tahrik robotunun konumunu izlemek için kullanılabilecek bir DifferentialDriveOdometry sınıfı içerir.

Not

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

Odometri Nesnesini Oluşturma

The DifferentialDriveOdometry class constructor requires three mandatory arguments and one optional argument. The mandatory arguments are:

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

  • The initial left and right encoder readings. In Java / Python, these are a number that represents the distance traveled by each side in meters. In C++, the units library must be used to represent your wheel positions.

The 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.

// Creating my odometry 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.
DifferentialDriveOdometry m_odometry = new DifferentialDriveOdometry(
  m_gyro.getRotation2d(),
  m_leftEncoder.getDistance(), m_rightEncoder.getDistance(),
  new Pose2d(5.0, 13.5, new Rotation2d()));
// Creating my odometry 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::DifferentialDriveOdometry m_odometry{
  m_gyro.GetRotation2d(),
  units::meter_t{m_leftEncoder.GetDistance()},
  units::meter_t{m_rightEncoder.GetDistance()},
  frc::Pose2d{5_m, 13.5_m, 0_rad}};
from wpimath.kinematics import DifferentialDriveOdometry
from wpimath.geometry import Pose2d
from wpimath.geometry import Rotation2d

# Creating my odometry 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.
m_odometry = DifferentialDriveOdometry(
  m_gyro.getRotation2d(),
  m_leftEncoder.getDistance(), m_rightEncoder.getDistance(),
  Pose2d(5.0, 13.5, Rotation2d()))

Robot Duruşunu Güncelleme

Robotun sahadaki konumunu güncellemek için update yöntemi kullanılabilir. Bu yöntem periyodik olarak, tercihen periodic() yönteminde Subsystem ile çağrılmalıdır. update yöntemi, robotun yeni güncellenmiş konumunu döndürür. Bu yöntem, sol kodlayıcı mesafesi ve sağ kodlayıcı mesafesi ile birlikte robotun cayro açısını alır.

Not

If the robot is moving forward in a straight line, both distances (left and right) must be increasing positively – the rate of change must be positive.

@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,
    m_leftEncoder.getDistance(),
    m_rightEncoder.getDistance());
}
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,
    units::meter_t{m_leftEncoder.GetDistance()},
    units::meter_t{m_rightEncoder.GetDistance()});
}
def periodic(self):
  # Get the rotation of the robot from the gyro.
  gyroAngle = m_gyro.getRotation2d()

  # Update the pose
  m_pose = m_odometry.update(gyroAngle,
    m_leftEncoder.getDistance(),
    m_rightEncoder.getDistance())

Robot Duruşunu Sıfırlama

The robot pose can be reset via the resetPosition method. This method accepts four arguments: the current gyro angle, the left and right wheel positions, and the new field-relative pose.

Önemli

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

Not

A full example of a differential drive robot with odometry is available 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.