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

    • vx

      public double vx
      Velocity along the x-axis in meters per second. (Fwd is +)

    • vy

      public double vy
      Velocity along the y-axis in meters per second. (Left is +)

    • omega

      public double omega
      Angular velocity of the robot frame in radians per second. (CCW is +)

    • proto

      public static final ChassisSpeedsProto proto
      ChassisSpeeds protobuf for serialization.

    • struct

      public static final ChassisSpeedsStruct struct
      ChassisSpeeds struct for serialization.

  • Constructor Details

    • ChassisSpeeds

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

    • ChassisSpeeds

      public ChassisSpeeds(double vx, double vy, double omega)
      Constructs a ChassisSpeeds object.
      Parameters:
      vx - Forward velocity in meters per second.
      vy - Sideways velocity in meters per second.
      omega - Angular velocity in radians per second.

    • 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 dt)
      Creates a Twist2d from ChassisSpeeds.
      Parameters:
      dt - The duration of the timestep in seconds.
      Returns:
      Twist2d.

    • discretize

      public ChassisSpeeds discretize(double dt)
      Discretizes a continuous-time chassis speed.

      This function converts this 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:
      dt - The duration of the timestep in seconds the speeds should be applied for.
      Returns:
      Discretized ChassisSpeeds.

    • toRobotRelative

      public ChassisSpeeds toRobotRelative(Rotation2d robotAngle)
      Converts this field-relative set of speeds into a robot-relative ChassisSpeeds object.
      Parameters:
      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.

    • toFieldRelative

      public ChassisSpeeds toFieldRelative(Rotation2d robotAngle)
      Converts this robot-relative set of speeds into a field-relative ChassisSpeeds object.
      Parameters:
      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