转向驱动运动学

``SwerveDriveKinematics’’类是一个有用的工具，可在``ChassisSpeeds’’对象和几个``SwerveModuleState’’对象之间进行转换，该对象包转向驱动机器人的每个速度模块的速度和角度。

备注

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

转向模块状态类

``SwerveModuleState’’类包含有关转向驱动单个模块的速度和角度的信息。 ``SwerveModuleState’’的构造函数接受两个参数，即车轮在模块上的速度和模块的角度。

备注

In Java / Python, the velocity of the wheel must be in meters per second. In C++, the units library can be used to provide the velocity using any linear velocity unit.

备注

角度0对应于面向前方的模块。

构造运动学对象

``SwerveDriveKinematics’’类接受可变数量的构造函数参数，每个参数都是相对于机器人中心的转向模块的位置（作为``Translation2d’’。构造函数参数的数量与转向的数量相对应模块。

备注

转向驱动必须具有2个或更多模块。

备注

在C ++中，该类以模块数量为模板。因此，在将“ SwerveDriveKinematics”对象构造为类的成员变量时，必须将多个模块作为模板参数传入。例如，对于具有四个模块的典型转向驱动，运动学对象必须按以下方式构造：``frc :: SwerveDriveKinematics <4> m_kinematics {…}’’。

模块的位置必须相对于机器人的中心。正的x值表示朝着机器人的前端移动，而正的y值表示朝着机器人的左侧移动。

JAVA

// 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
);

C++

// 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};

PYTHON

# Python requires using the right class for the number of modules you have
from wpimath.geometry import Translation2d
from wpimath.kinematics import SwerveDrive4Kinematics
# 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
)

将模块状态转换为底盘速度

One can also use the kinematics object to convert an array of SwerveModuleState objects to a singular ChassisSpeeds object. The toChassisSpeeds(SwerveModuleState... states) (Java / Python) / ToChassisSpeeds(SwerveModuleState... states) (C++) method can be used to achieve this.

JAVA

// Example module states
var frontLeftState = new SwerveModuleState(23.43, Rotation2d.fromDegrees(-140.19));
var frontRightState = new SwerveModuleState(23.43, Rotation2d.fromDegrees(-39.81));
var backLeftState = new SwerveModuleState(54.08, Rotation2d.fromDegrees(-109.44));
var backRightState = new SwerveModuleState(54.08, Rotation2d.fromDegrees(-70.56));
// Convert to chassis speeds
ChassisSpeeds chassisSpeeds = kinematics.toChassisSpeeds(
  frontLeftState, frontRightState, backLeftState, backRightState);
// Getting individual speeds
double forward = chassisSpeeds.vxMetersPerSecond;
double sideways = chassisSpeeds.vyMetersPerSecond;
double angular = chassisSpeeds.omegaRadiansPerSecond;

C++

// Example module States
frc::SwerveModuleState frontLeftState{23.43_mps, Rotation2d(-140.19_deg)};
frc::SwerveModuleState frontRightState{23.43_mps, Rotation2d(-39.81_deg)};
frc::SwerveModuleState backLeftState{54.08_mps, Rotation2d(-109.44_deg)};
frc::SwerveModuleState backRightState{54.08_mps, Rotation2d(-70.56_deg)};
// 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(
  frontLeftState, frontRightState, backLeftState, backRightState);

PYTHON

from wpimath.kinematics import SwerveModuleState
from wpimath.geometry import Rotation2d
# Example module states
frontLeftState = SwerveModuleState(23.43, Rotation2d.fromDegrees(-140.19))
frontRightState = SwerveModuleState(23.43, Rotation2d.fromDegrees(-39.81))
backLeftState = SwerveModuleState(54.08, Rotation2d.fromDegrees(-109.44))
backRightState = SwerveModuleState(54.08, Rotation2d.fromDegrees(-70.56))
# Convert to chassis speeds
chassisSpeeds = self.kinematics.toChassisSpeeds(
  frontLeftState, frontRightState, backLeftState, backRightState)
# Getting individual speeds
forward = chassisSpeeds.vx
sideways = chassisSpeeds.vy
angular = chassisSpeeds.omega

Module state visualization with AdvantageScope

By recording a set of swerve module states using NetworkTables or WPILib data logs, AdvantageScope can be used to visualize the state of a swerve drive. The code below shows how a set of SwerveModuleState objects can be published to NetworkTables.

JAVA

public class Example {
  private final StructArrayPublisher<SwerveModuleState> publisher;
  public Example() {
    // Start publishing an array of module states with the "/SwerveStates" key
    publisher = NetworkTableInstance.getDefault()
      .getStructArrayTopic("/SwerveStates", SwerveModuleState.struct).publish();
  }
  public void periodic() {
    // Periodically send a set of module states
    publisher.set(new SwerveModuleState[] {
      frontLeftState,
      frontRightState,
      backLeftState,
      backRightState
    });
  }
}

C++

class Example {
  nt::StructArrayPublisher<frc::SwerveModuleState> publisher
 public:
  Example() {
    // Start publishing an array of module states with the "/SwerveStates" key
    publisher = nt::NetworkTableInstance::GetDefault()
      .GetStructArrayTopic<frc::SwerveModuleState>("/SwerveStates").Publish();
  }
  void Periodic() {
    // Periodically send a set of module states
    swervePublisher.Set(
      std::vector{
        frontLeftState,
        frontRightState,
        backLeftState,
        backRightState
      }
    );
  }
};

PYTHON

import ntcore
from wpimath.kinematics import SwerveModuleState
# get the default instance of NetworkTables
nt = ntcore.NetworkTableInstance.getDefault()
# Start publishing an array of module states with the "/SwerveStates" key
topic = nt.getStructArrayTopic("/SwerveStates", SwerveModuleState)
self.pub = topic.publish()
def periodic(self):
  # Periodically send a set of module states
  self.pub.set([frontLeftState,frontRightState,backLeftState,backRightState])

See the documentation for the swerve tab for more details on visualizing this data using AdvantageScope.

Screenshot of an AdvantageScope window displaying a swerve visualization.

转向驱动运动学

转向模块状态类

构造运动学对象

将底盘速度转换为模块状态

模块角度优化

Cosine compensation

定向驱动

使用自定义旋转中心

将模块状态转换为底盘速度

Module state visualization with AdvantageScope