Package swervelib.math

Class SwerveKinematics2

java.lang.Object
edu.wpi.first.math.kinematics.SwerveDriveKinematics
swervelib.math.SwerveKinematics2
public class SwerveKinematics2 extends edu.wpi.first.math.kinematics.SwerveDriveKinematics
Clone of WPI SwerveKinematics, which implements second order kinematics when calculating modules states from chassis speed. Makes use of SwerveModuleState2 to add the angular velocity that is required of the module as an output.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private final org.ejml.simple.SimpleMatrix
    bigInverseKinematics
    Second order kinematics inverse matrix.
    private final org.ejml.simple.SimpleMatrix
    m_forwardKinematics
    Forward kinematics matrix.
    private final org.ejml.simple.SimpleMatrix
    m_inverseKinematics
    Inverse kinematics matrix.
    private final edu.wpi.first.math.geometry.Translation2d[]
    m_modules
    Location of each swerve module in meters.
    private final SwerveModuleState2[]
    m_moduleStates
    Swerve module states.
    private final int
    m_numModules
    Number of swerve modules.
    private edu.wpi.first.math.geometry.Translation2d
    m_prevCoR
    Previous CoR

  • Constructor Summary

    Constructors
    Constructor
    Description
    SwerveKinematics2(edu.wpi.first.math.geometry.Translation2d... wheelsMeters)
    Constructs a swerve drive kinematics object.

  • Method Summary

    Modifier and Type
    Method
    Description
    static void
    desaturateWheelSpeeds(SwerveModuleState2[] moduleStates, double attainableMaxSpeedMetersPerSecond)
    Renormalizes the wheel speeds if any individual speed is above the specified maximum.
    static void
    desaturateWheelSpeeds(SwerveModuleState2[] moduleStates, edu.wpi.first.math.kinematics.ChassisSpeeds currentChassisSpeed, double attainableMaxModuleSpeedMetersPerSecond, double attainableMaxTranslationalSpeedMetersPerSecond, double attainableMaxRotationalVelocityRadiansPerSecond)
    Renormalizes the wheel speeds if any individual speed is above the specified maximum, as well as getting rid of joystick saturation at edges of joystick.
    edu.wpi.first.math.kinematics.ChassisSpeeds
    toChassisSpeeds(SwerveModuleState2... wheelStates)
    Performs forward kinematics to return the resulting chassis state from the given module states.
    SwerveModuleState2[]
    toSwerveModuleStates(edu.wpi.first.math.kinematics.ChassisSpeeds chassisSpeeds)
    Performs inverse kinematics.
    SwerveModuleState2[]
    toSwerveModuleStates(edu.wpi.first.math.kinematics.ChassisSpeeds chassisSpeeds, edu.wpi.first.math.geometry.Translation2d centerOfRotationMeters)
    Performs inverse kinematics to return the module states from a desired chassis velocity.
    edu.wpi.first.math.geometry.Twist2d
    toTwist2d(edu.wpi.first.math.kinematics.SwerveModulePosition... wheelDeltas)
    Performs forward kinematics to return the resulting chassis state from the given module states.

    Methods inherited from class edu.wpi.first.math.kinematics.SwerveDriveKinematics

    desaturateWheelSpeeds, desaturateWheelSpeeds, toChassisSpeeds

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • m_inverseKinematics

      private final org.ejml.simple.SimpleMatrix m_inverseKinematics
      Inverse kinematics matrix.

    • m_forwardKinematics

      private final org.ejml.simple.SimpleMatrix m_forwardKinematics
      Forward kinematics matrix.

    • bigInverseKinematics

      private final org.ejml.simple.SimpleMatrix bigInverseKinematics
      Second order kinematics inverse matrix.

    • m_numModules

      private final int m_numModules
      Number of swerve modules.

    • m_modules

      private final edu.wpi.first.math.geometry.Translation2d[] m_modules
      Location of each swerve module in meters.

    • m_moduleStates

      private final SwerveModuleState2[] m_moduleStates
      Swerve module states.

    • m_prevCoR

      private edu.wpi.first.math.geometry.Translation2d m_prevCoR
      Previous CoR

  • Constructor Details

    • SwerveKinematics2

      public SwerveKinematics2(edu.wpi.first.math.geometry.Translation2d... wheelsMeters)
      Constructs a swerve drive kinematics object. This takes in a variable number of wheel locations as Translation2ds. The order in which you pass in the wheel locations is the same order that you will receive the module states when performing inverse kinematics. It is also expected that you pass in the module states in the same order when calling the forward kinematics methods.
      Parameters:
      wheelsMeters - The locations of the wheels relative to the physical center of the robot.

  • Method Details

    • desaturateWheelSpeeds

      public static void desaturateWheelSpeeds(SwerveModuleState2[] moduleStates, double attainableMaxSpeedMetersPerSecond)
      Renormalizes the wheel speeds if any individual speed is above the specified maximum.

      Sometimes, after inverse kinematics, the requested speed from one or more modules may be above the max attainable speed for the driving motor on that module. To fix this issue, one can reduce all the wheel speeds to make sure that all requested module speeds are at-or-below the absolute threshold, while maintaining the ratio of speeds between modules.

      Parameters:
      moduleStates - Reference to array of module states. The array will be mutated with the normalized speeds!
      attainableMaxSpeedMetersPerSecond - The absolute max speed that a module can reach.

    • desaturateWheelSpeeds

      public static void desaturateWheelSpeeds(SwerveModuleState2[] moduleStates, edu.wpi.first.math.kinematics.ChassisSpeeds currentChassisSpeed, double attainableMaxModuleSpeedMetersPerSecond, double attainableMaxTranslationalSpeedMetersPerSecond, double attainableMaxRotationalVelocityRadiansPerSecond)
      Renormalizes the wheel speeds if any individual speed is above the specified maximum, as well as getting rid of joystick saturation at edges of joystick.

      Sometimes, after inverse kinematics, the requested speed from one or more modules may be above the max attainable speed for the driving motor on that module. To fix this issue, one can reduce all the wheel speeds to make sure that all requested module speeds are at-or-below the absolute threshold, while maintaining the ratio of speeds between modules.

      Parameters:
      moduleStates - Reference to array of module states. The array will be mutated with the normalized speeds!
      currentChassisSpeed - The current speed of the robot
      attainableMaxModuleSpeedMetersPerSecond - The absolute max speed that a module can reach
      attainableMaxTranslationalSpeedMetersPerSecond - The absolute max speed that your robot can reach while translating
      attainableMaxRotationalVelocityRadiansPerSecond - The absolute max speed the robot can reach while rotating

    • toSwerveModuleStates

      public SwerveModuleState2[] toSwerveModuleStates(edu.wpi.first.math.kinematics.ChassisSpeeds chassisSpeeds, edu.wpi.first.math.geometry.Translation2d centerOfRotationMeters)
      Performs inverse kinematics to return the module states from a desired chassis velocity. This method is often used to convert joystick values into module speeds and angles.

      This function also supports variable centers of rotation. During normal operations, the center of rotation is usually the same as the physical center of the robot; therefore, the argument is defaulted to that use case. However, if you wish to change the center of rotation for evasive maneuvers, vision alignment, or for any other use case, you can do so.

      In the case that the desired chassis speeds are zero (i.e. the robot will be stationary), the previously calculated module angle will be maintained.

      Overrides:
      toSwerveModuleStates in class edu.wpi.first.math.kinematics.SwerveDriveKinematics
      Parameters:
      chassisSpeeds - The desired chassis speed.
      centerOfRotationMeters - The center of rotation. For example, if you set the center of rotation at one corner of the robot and provide a chassis speed that only has a dtheta component, the robot will rotate around that corner.
      Returns:
      An array containing the module states. Use caution because these module states are not normalized. Sometimes, a user input may cause one of the module speeds to go above the attainable max velocity. Use the DesaturateWheelSpeeds function to rectify this issue.

    • toSwerveModuleStates

      public SwerveModuleState2[] toSwerveModuleStates(edu.wpi.first.math.kinematics.ChassisSpeeds chassisSpeeds)
      Performs inverse kinematics. See toSwerveModuleStates(ChassisSpeeds, Translation2d) toSwerveModuleStates for more information.
      Overrides:
      toSwerveModuleStates in class edu.wpi.first.math.kinematics.SwerveDriveKinematics
      Parameters:
      chassisSpeeds - The desired chassis speed.
      Returns:
      An array containing the module states.

    • toChassisSpeeds

      public edu.wpi.first.math.kinematics.ChassisSpeeds toChassisSpeeds(SwerveModuleState2... wheelStates)
      Performs forward kinematics to return the resulting chassis state from the given module states. This method is often used for odometry -- determining the robot's position on the field using data from the real-world speed and angle of each module on the robot.
      Parameters:
      wheelStates - The state of the modules (as a SwerveModuleState type) as measured from respective encoders and gyros. The order of the swerve module states should be same as passed into the constructor of this class.
      Returns:
      The resulting chassis speed.

    • toTwist2d

      public edu.wpi.first.math.geometry.Twist2d toTwist2d(edu.wpi.first.math.kinematics.SwerveModulePosition... wheelDeltas)
      Performs forward kinematics to return the resulting chassis state from the given module states. This method is often used for odometry -- determining the robot's position on the field using data from the real-world speed and angle of each module on the robot.
      Overrides:
      toTwist2d in class edu.wpi.first.math.kinematics.SwerveDriveKinematics
      Parameters:
      wheelDeltas - The latest change in position of the modules (as a SwerveModulePosition type) as measured from respective encoders and gyros. The order of the swerve module states should be same as passed into the constructor of this class.
      Returns:
      The resulting Twist2d.