Class ChassisVelocities

java.lang.Object
org.wpilib.math.kinematics.ChassisVelocities
All Implemented Interfaces:
Interpolatable<ChassisVelocities>, ProtobufSerializable, StructSerializable, WPISerializable
public class ChassisVelocities extends Object implements ProtobufSerializable, StructSerializable, Interpolatable<ChassisVelocities>
Represents robot chassis velocities.

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 ChassisVelocities object represents a robot's velocities.

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 ChassisVelocitiesProto proto
      ChassisVelocities protobuf for serialization.

    • struct

      public static final ChassisVelocitiesStruct struct
      ChassisVelocities struct for serialization.

  • Constructor Details

    • ChassisVelocities

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

    • ChassisVelocities

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

    • ChassisVelocities

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

  • Method Details

    • toTwist2d

      public Twist2d toTwist2d(double dt)
      Creates a Twist2d from ChassisVelocities.
      Parameters:
      dt - The duration of the timestep in seconds.
      Returns:
      Twist2d.

    • discretize

      public ChassisVelocities discretize(double dt)
      Discretizes continuous-time chassis velocities.

      This function converts these continuous-time chassis velocities into discrete-time ones such that when the discrete-time chassis velocities are 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 ChassisVelocities after discretizing (e.g., when desaturating swerve module velocities) 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 velocities should be applied for.
      Returns:
      Discretized ChassisVelocities.

    • toRobotRelative

      public ChassisVelocities toRobotRelative(Rotation2d robotAngle)
      Converts this field-relative set of velocities into a robot-relative ChassisVelocities 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:
      ChassisVelocities object representing the velocities in the robot's frame of reference.

    • toFieldRelative

      public ChassisVelocities toFieldRelative(Rotation2d robotAngle)
      Converts this robot-relative set of velocities into a field-relative ChassisVelocities 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:
      ChassisVelocities object representing the velocities in the field's frame of reference.

    • plus

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

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

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

    • minus

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

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

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

    • unaryMinus

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

    • times

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

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

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

    • div

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

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

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

    • interpolate

      public ChassisVelocities interpolate(ChassisVelocities endValue, double t)
      Description copied from interface: Interpolatable
      Return the interpolated value. This object is assumed to be the starting position, or lower bound.
      Specified by:
      interpolate in interface Interpolatable<ChassisVelocities>
      Parameters:
      endValue - The upper bound, or end.
      t - How far between the lower and upper bound we are. This should be bounded in [0, 1].
      Returns:
      The interpolated value.

    • 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