Mecanum Drive Kinematik

MecanumDriveKinematics sınıfı, bir ChassisSpeeds nesnesi ile bir mecanum sürücüsündeki dört tekerleğin her biri için hızları içeren bir MecanumDriveWheelSpeeds nesnesi arasında dönüşüm sağlayan kullanışlı bir araçtır.

Not

Mecanum kinematics uses a common coordinate system. You may wish to reference the Coordinate System section for details.

Kinematik Nesnesinin Oluşturulması

MecanumDriveKinematics sınıfı dört constructor argümanı kabul eder, her argüman robot merkezine göre bir tekerleğin konumu olur (Translation2d olarak). Argümanların sırası sol ön, sağ ön, sol arka ve sağ arka şeklindedir. Tekerleklerin yerleri, robotun merkezine göre olmalıdır. Pozitif x değerleri robotun önüne doğru hareket etmeyi temsil ederken, pozitif y değerleri robotun soluna doğru hareket etmeyi temsil eder.

// Locations of the wheels 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 wheel locations.
MecanumDriveKinematics m_kinematics = new MecanumDriveKinematics(
  m_frontLeftLocation, m_frontRightLocation, m_backLeftLocation, m_backRightLocation
);

// Locations of the wheels 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 wheel locations.
frc::MecanumDriveKinematics m_kinematics{
  m_frontLeftLocation, m_frontRightLocation, m_backLeftLocation,
  m_backRightLocation};

from wpimath.geometry import Translation2d
from wpimath.kinematics import MecanumDriveKinematics

# Locations of the wheels 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 wheel locations.
self.kinematics = MecanumDriveKinematics(
  frontLeftLocation, frontRightLocation, backLeftLocation, backRightLocation
)

Şasi Hızlarını Tekerlek Hızlarına Dönüştürme

The toWheelSpeeds(ChassisSpeeds speeds) (Java / Python) / ToWheelSpeeds(ChassisSpeeds speeds) (C++) method should be used to convert a ChassisSpeeds object to a MecanumDriveWheelSpeeds object. This is useful in situations where you have to convert a forward velocity, sideways velocity, and an angular velocity into individual wheel speeds.

// Example chassis speeds: 1 meter per second forward, 3 meters
// per second to the left, and rotation at 1.5 radians per second
// counterclockwise.
ChassisSpeeds speeds = new ChassisSpeeds(1.0, 3.0, 1.5);

// Convert to wheel speeds
MecanumDriveWheelSpeeds wheelSpeeds = kinematics.toWheelSpeeds(speeds);

// Get the individual wheel speeds
double frontLeft = wheelSpeeds.frontLeftMetersPerSecond
double frontRight = wheelSpeeds.frontRightMetersPerSecond
double backLeft = wheelSpeeds.rearLeftMetersPerSecond
double backRight = wheelSpeeds.rearRightMetersPerSecond

// Example chassis speeds: 1 meter per second forward, 3 meters
// per second to the left, and rotation at 1.5 radians per second
// counterclockwise.
frc::ChassisSpeeds speeds{1_mps, 3_mps, 1.5_rad_per_s};

// Convert to wheel speeds. Here, we can use C++17's structured
// bindings feature to automatically split up the MecanumDriveWheelSpeeds
// struct into it's individual components
auto [fl, fr, bl, br] = kinematics.ToWheelSpeeds(speeds);

from wpimath.kinematics import ChassisSpeeds

# Example chassis speeds: 1 meter per second forward, 3 meters
# per second to the left, and rotation at 1.5 radians per second
# counterclockwise.
speeds = ChassisSpeeds(1.0, 3.0, 1.5)

# Convert to wheel speeds
frontLeft, frontRight, backLeft, backRight = self.kinematics.toWheelSpeeds(speeds)

Field-oriented / Saha-odaklı sürüş

Recall bir ChassisSpeeds nesnesinin istenen saha odaklı hızlardan oluşturulabileceğini hatırlayın. Bu özellik, istenen saha odaklı hızlardan tekerlek hızları elde etmek için kullanılabilir.

// The desired field relative speed here is 2 meters per second
// toward the opponent's alliance station wall, and 2 meters per
// second toward the left field boundary. The desired rotation
// is a quarter of a rotation per second counterclockwise. The current
// robot angle is 45 degrees.
ChassisSpeeds speeds = ChassisSpeeds.fromFieldRelativeSpeeds(
  2.0, 2.0, Math.PI / 2.0, Rotation2d.fromDegrees(45.0));

// Now use this in our kinematics
MecanumDriveWheelSpeeds wheelSpeeds = kinematics.toWheelSpeeds(speeds);

// The desired field relative speed here is 2 meters per second
// toward the opponent's alliance station wall, and 2 meters per
// second toward the left field boundary. The desired rotation
// is a quarter of a rotation per second counterclockwise. The current
// robot angle is 45 degrees.
frc::ChassisSpeeds speeds = frc::ChassisSpeeds::FromFieldRelativeSpeeds(
  2_mps, 2_mps, units::radians_per_second_t(std::numbers::pi / 2.0), Rotation2d(45_deg));

// Now use this in our kinematics
auto [fl, fr, bl, br] = kinematics.ToWheelSpeeds(speeds);

from wpimath.kinematics import ChassisSpeeds
import math
from wpimath.geometry import Rotation2d

# The desired field relative speed here is 2 meters per second
# toward the opponent's alliance station wall, and 2 meters per
# second toward the left field boundary. The desired rotation
# is a quarter of a rotation per second counterclockwise. The current
# robot angle is 45 degrees.
speeds = ChassisSpeeds.fromFieldRelativeSpeeds(
  2.0, 2.0, math.pi / 2.0, Rotation2d.fromDegrees(45.0))

# Now use this in our kinematics
wheelSpeeds = self.kinematics.toWheelSpeeds(speeds)

Özel döndürme merkezlerini kullanma

Bazen, belirli bir kaçamak manevraları için belirli bir köşenin etrafında dönmek istenebilir. Bu tür davranış, WPILib sınıfları tarafından da desteklenir. Aynı ToWheelSpeeds()'' yöntemi, dönüş merkezi için ikinci bir parametre kabul eder (``Translation2d olarak). Tıpkı tekerlek konumları gibi, dönme merkezini temsil eden Translation2d de robot merkezine göre olmalıdır.

Not

Tüm robotlar sabit bir çerçeve olduğundan, ChassisSpeeds nesnesinden sağlanan vx ve vy hızları, robotun tamamı için geçerli olmaya devam edecektir. Bununla birlikte, ChassisSpeeds nesnesindeki omega, dönüş merkezinden ölçülecektir.

Örneğin, belirli bir tekerlek üzerinde dönme merkezi ayarlanabilir ve sağlanan ChassisSpeeds nesnesi sıfır olan bir vx ve vy ye ve sıfır olmayan bir omega ya sahipse, robot, o tekerleğin etrafında dönüyormuş gibi görünecektir.

Tekerlek hızlarını şasi hızlarına dönüştürme

One can also use the kinematics object to convert a MecanumDriveWheelSpeeds object to a singular ChassisSpeeds object. The toChassisSpeeds(MecanumDriveWheelSpeeds speeds) (Java / Python) / ToChassisSpeeds(MecanumDriveWheelSpeeds speeds) (C++) method can be used to achieve this.

// Example wheel speeds
var wheelSpeeds = new MecanumDriveWheelSpeeds(-17.67, 20.51, -13.44, 16.26);

// Convert to chassis speeds
ChassisSpeeds chassisSpeeds = kinematics.toChassisSpeeds(wheelSpeeds);

// Getting individual speeds
double forward = chassisSpeeds.vxMetersPerSecond;
double sideways = chassisSpeeds.vyMetersPerSecond;
double angular = chassisSpeeds.omegaRadiansPerSecond;

// Example wheel speeds
frc::MecanumDriveWheelSpeeds wheelSpeeds{-17.67_mps, 20.51_mps, -13.44_mps, 16.26_mps};

// Convert to chassis speeds. Here, we can use C++17's structured bindings
// feature to automatically break up the ChassisSpeeds struct into its
// three components.
auto [forward, sideways, angular] = kinematics.ToChassisSpeeds(wheelSpeeds);

from wpimath.kinematics import MecanumDriveWheelSpeeds

# Example wheel speeds
wheelSpeeds = MecanumDriveWheelSpeeds(-17.67, 20.51, -13.44, 16.26)

# Convert to chassis speeds
chassisSpeeds = self.kinematics.toChassisSpeeds(wheelSpeeds)

# Getting individual speeds
forward = chassisSpeeds.vx
sideways = chassisSpeeds.vy
angular = chassisSpeeds.omega