Package edu.wpi.first.math.kinematics

Class ChassisSpeeds

java.lang.Object
edu.wpi.first.math.kinematics.ChassisSpeeds
All Implemented Interfaces:
ProtobufSerializable, StructSerializable, WPISerializable
public class ChassisSpeeds extends Object implements ProtobufSerializable, StructSerializable
Represents the speed of a robot chassis. Although this class contains similar members compared to a Twist2d, they do NOT represent the same thing. Whereas a Twist2d represents a change in pose w.r.t to the robot frame of reference, a ChassisSpeeds object represents a robot's velocity.

A strictly non-holonomic drivetrain, such as a differential drive, should never have a dy component because it can never move sideways. Holonomic drivetrains such as swerve and mecanum will often have all three components.

  • Field Details

  • Constructor Details

    • ChassisSpeeds

      public ChassisSpeeds()
      Constructs a ChassisSpeeds with zeros for dx, dy, and theta.

    • ChassisSpeeds

      public ChassisSpeeds(double vxMetersPerSecond, double vyMetersPerSecond, double omegaRadiansPerSecond)
      Constructs a ChassisSpeeds object.
      Parameters:
      vxMetersPerSecond - Forward velocity.
      vyMetersPerSecond - Sideways velocity.
      omegaRadiansPerSecond - Angular velocity.

    • ChassisSpeeds

      public ChassisSpeeds(LinearVelocity vx, LinearVelocity vy, AngularVelocity omega)
      Constructs a ChassisSpeeds object.
      Parameters:
      vx - Forward velocity.
      vy - Sideways velocity.
      omega - Angular velocity.

  • Method Details

    • toTwist2d

      public Twist2d toTwist2d(double dtSeconds)
      Creates a Twist2d from ChassisSpeeds.
      Parameters:
      dtSeconds - The duration of the timestep.
      Returns:
      Twist2d.

    • discretize

      public static ChassisSpeeds discretize(double vxMetersPerSecond, double vyMetersPerSecond, double omegaRadiansPerSecond, double dtSeconds)
      Discretizes a continuous-time chassis speed.

      This function converts a continuous-time chassis speed into a discrete-time one such that when the discrete-time chassis speed is applied for one timestep, the robot moves as if the velocity components are independent (i.e., the robot moves v_x * dt along the x-axis, v_y * dt along the y-axis, and omega * dt around the z-axis).

      This is useful for compensating for translational skew when translating and rotating a holonomic (swerve or mecanum) drivetrain. However, scaling down the ChassisSpeeds after discretizing (e.g., when desaturating swerve module speeds) rotates the direction of net motion in the opposite direction of rotational velocity, introducing a different translational skew which is not accounted for by discretization.

      Parameters:
      vxMetersPerSecond - Forward velocity.
      vyMetersPerSecond - Sideways velocity.
      omegaRadiansPerSecond - Angular velocity.
      dtSeconds - The duration of the timestep the speeds should be applied for.
      Returns:
      Discretized ChassisSpeeds.

    • discretize

      public static ChassisSpeeds discretize(LinearVelocity vx, LinearVelocity vy, AngularVelocity omega, Time dt)
      Discretizes a continuous-time chassis speed.

      This function converts a continuous-time chassis speed into a discrete-time one such that when the discrete-time chassis speed is applied for one timestep, the robot moves as if the velocity components are independent (i.e., the robot moves v_x * dt along the x-axis, v_y * dt along the y-axis, and omega * dt around the z-axis).

      This is useful for compensating for translational skew when translating and rotating a holonomic (swerve or mecanum) drivetrain. However, scaling down the ChassisSpeeds after discretizing (e.g., when desaturating swerve module speeds) rotates the direction of net motion in the opposite direction of rotational velocity, introducing a different translational skew which is not accounted for by discretization.

      Parameters:
      vx - Forward velocity.
      vy - Sideways velocity.
      omega - Angular velocity.
      dt - The duration of the timestep the speeds should be applied for.
      Returns:
      Discretized ChassisSpeeds.

    • discretize

      public static ChassisSpeeds discretize(ChassisSpeeds continuousSpeeds, double dtSeconds)
      Discretizes a continuous-time chassis speed.

      This function converts a continuous-time chassis speed into a discrete-time one such that when the discrete-time chassis speed is applied for one timestep, the robot moves as if the velocity components are independent (i.e., the robot moves v_x * dt along the x-axis, v_y * dt along the y-axis, and omega * dt around the z-axis).

      This is useful for compensating for translational skew when translating and rotating a holonomic (swerve or mecanum) drivetrain. However, scaling down the ChassisSpeeds after discretizing (e.g., when desaturating swerve module speeds) rotates the direction of net motion in the opposite direction of rotational velocity, introducing a different translational skew which is not accounted for by discretization.

      Parameters:
      continuousSpeeds - The continuous speeds.
      dtSeconds - The duration of the timestep the speeds should be applied for.
      Returns:
      Discretized ChassisSpeeds.

    • fromFieldRelativeSpeeds

      public static ChassisSpeeds fromFieldRelativeSpeeds(double vxMetersPerSecond, double vyMetersPerSecond, double omegaRadiansPerSecond, Rotation2d robotAngle)
      Converts a user provided field-relative set of speeds into a robot-relative ChassisSpeeds object.
      Parameters:
      vxMetersPerSecond - The component of speed in the x direction relative to the field. Positive x is away from your alliance wall.
      vyMetersPerSecond - The component of speed in the y direction relative to the field. Positive y is to your left when standing behind the alliance wall.
      omegaRadiansPerSecond - The angular rate of the robot.
      robotAngle - The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.
      Returns:
      ChassisSpeeds object representing the speeds in the robot's frame of reference.

    • fromFieldRelativeSpeeds

      public static ChassisSpeeds fromFieldRelativeSpeeds(LinearVelocity vx, LinearVelocity vy, AngularVelocity omega, Rotation2d robotAngle)
      Converts a user provided field-relative set of speeds into a robot-relative ChassisSpeeds object.
      Parameters:
      vx - The component of speed in the x direction relative to the field. Positive x is away from your alliance wall.
      vy - The component of speed in the y direction relative to the field. Positive y is to your left when standing behind the alliance wall.
      omega - The angular rate of the robot.
      robotAngle - The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.
      Returns:
      ChassisSpeeds object representing the speeds in the robot's frame of reference.

    • fromFieldRelativeSpeeds

      public static ChassisSpeeds fromFieldRelativeSpeeds(ChassisSpeeds fieldRelativeSpeeds, Rotation2d robotAngle)
      Converts a user provided field-relative ChassisSpeeds object into a robot-relative ChassisSpeeds object.
      Parameters:
      fieldRelativeSpeeds - The ChassisSpeeds object representing the speeds in the field frame of reference. Positive x is away from your alliance wall. Positive y is to your left when standing behind the alliance wall.
      robotAngle - The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.
      Returns:
      ChassisSpeeds object representing the speeds in the robot's frame of reference.

    • fromRobotRelativeSpeeds

      public static ChassisSpeeds fromRobotRelativeSpeeds(double vxMetersPerSecond, double vyMetersPerSecond, double omegaRadiansPerSecond, Rotation2d robotAngle)
      Converts a user provided robot-relative set of speeds into a field-relative ChassisSpeeds object.
      Parameters:
      vxMetersPerSecond - The component of speed in the x direction relative to the robot. Positive x is towards the robot's front.
      vyMetersPerSecond - The component of speed in the y direction relative to the robot. Positive y is towards the robot's left.
      omegaRadiansPerSecond - The angular rate of the robot.
      robotAngle - The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.
      Returns:
      ChassisSpeeds object representing the speeds in the field's frame of reference.

    • fromRobotRelativeSpeeds

      public static ChassisSpeeds fromRobotRelativeSpeeds(LinearVelocity vx, LinearVelocity vy, AngularVelocity omega, Rotation2d robotAngle)
      Converts a user provided robot-relative set of speeds into a field-relative ChassisSpeeds object.
      Parameters:
      vx - The component of speed in the x direction relative to the robot. Positive x is towards the robot's front.
      vy - The component of speed in the y direction relative to the robot. Positive y is towards the robot's left.
      omega - The angular rate of the robot.
      robotAngle - The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.
      Returns:
      ChassisSpeeds object representing the speeds in the field's frame of reference.

    • fromRobotRelativeSpeeds

      public static ChassisSpeeds fromRobotRelativeSpeeds(ChassisSpeeds robotRelativeSpeeds, Rotation2d robotAngle)
      Converts a user provided robot-relative ChassisSpeeds object into a field-relative ChassisSpeeds object.
      Parameters:
      robotRelativeSpeeds - The ChassisSpeeds object representing the speeds in the robot frame of reference. Positive x is towards the robot's front. Positive y is towards the robot's left.
      robotAngle - The angle of the robot as measured by a gyroscope. The robot's angle is considered to be zero when it is facing directly away from your alliance station wall. Remember that this should be CCW positive.
      Returns:
      ChassisSpeeds object representing the speeds in the field's frame of reference.

    • plus

      public ChassisSpeeds plus(ChassisSpeeds other)
      Adds two ChassisSpeeds and returns the sum.

      For example, ChassisSpeeds{1.0, 0.5, 0.75} + ChassisSpeeds{2.0, 1.5, 0.25} = ChassisSpeeds{3.0, 2.0, 1.0}

      Parameters:
      other - The ChassisSpeeds to add.
      Returns:
      The sum of the ChassisSpeeds.

    • minus

      public ChassisSpeeds minus(ChassisSpeeds other)
      Subtracts the other ChassisSpeeds from the current ChassisSpeeds and returns the difference.

      For example, ChassisSpeeds{5.0, 4.0, 2.0} - ChassisSpeeds{1.0, 2.0, 1.0} = ChassisSpeeds{4.0, 2.0, 1.0}

      Parameters:
      other - The ChassisSpeeds to subtract.
      Returns:
      The difference between the two ChassisSpeeds.

    • unaryMinus

      public ChassisSpeeds unaryMinus()
      Returns the inverse of the current ChassisSpeeds. This is equivalent to negating all components of the ChassisSpeeds.
      Returns:
      The inverse of the current ChassisSpeeds.

    • times

      public ChassisSpeeds times(double scalar)
      Multiplies the ChassisSpeeds by a scalar and returns the new ChassisSpeeds.

      For example, ChassisSpeeds{2.0, 2.5, 1.0} * 2 = ChassisSpeeds{4.0, 5.0, 1.0}

      Parameters:
      scalar - The scalar to multiply by.
      Returns:
      The scaled ChassisSpeeds.

    • div

      public ChassisSpeeds div(double scalar)
      Divides the ChassisSpeeds by a scalar and returns the new ChassisSpeeds.

      For example, ChassisSpeeds{2.0, 2.5, 1.0} / 2 = ChassisSpeeds{1.0, 1.25, 0.5}

      Parameters:
      scalar - The scalar to divide by.
      Returns:
      The scaled ChassisSpeeds.

    • hashCode

      public final int hashCode()
      Overrides:
      hashCode in class Object

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object