Package org.chsrobotics.lib.models

Class DoubleJointedArmKinematics

java.lang.Object
org.chsrobotics.lib.models.DoubleJointedArmKinematics
public class DoubleJointedArmKinematics extends Object
Class for performing forward and inverse kinematic operations to determine the configuration of an arm with 2 revolute (rotational) degrees of freedom.

Units of linear distance in this class are not specified, but must be consistent.

  • Field Details

    • localLength

      public final double localLength
      Length of the local segment (the segment closest to the root).

    • distalLength

      public final double distalLength
      Length of the distal segment (the segment closest to the end effector).

  • Constructor Details

    • DoubleJointedArmKinematics

      public DoubleJointedArmKinematics(double localLength, double distalLength)
      Constructs a DoubleJointedArmKinematics.

      If either of the below are zero or less, this class's methods will return null.

      Parameters:
      localLength - Length of the local segment (the segment closest to the root).
      distalLength - Length of the distal segment (the segment closest to the end effector).

  • Method Details

    • forwardKinematics

      public DoubleJointedArmKinematics.RRConfiguration forwardKinematics(double localAngle, double distalAngle)
      Determines the position of the end effector in 2-dimensional space, given the angles of the joints.
      Parameters:
      localAngle - Angle of the local joint (the joint connected to the root), in radians, from (counterclockwise) the horizontal (or the positive x-axis in non-vertically oriented setups).
      distalAngle - Angle of the distal joint (the joint between arm segments), in radians, from (counterclockwise) parallel with the local joint.
      Returns:
      A RRConfiguration describing the orientation.

    • inverseKinematics

      public Tuple2<DoubleJointedArmKinematics.RRConfiguration> inverseKinematics(double endEffectorX, double endEffectorY)
      Returns a tuple of 2 RRConfigurations with the joint angles required for the end effector to reach a certain position in a Cartesian frame.

      Two returned RRConfigurations are needed because there are 2 inverse kinematic solutions to most possible cases. When only one solution exists, it is returned twice.

      If the goal point is (0,0), there are either 0 or an infinite number of solutions, depending on arm lengths, so a tuple of nulls is returned.

      This will also return nulls if there are no solutions to reach the goal position. This happens when sqrt(x^2 + y^2) > lenA + lenB, or sqrt(x^2 + y^2) < |lenA - lenB|.

      No guarantees are made about the actual feasibility of these configurations on hardware.

      Parameters:
      endEffectorX - The x-position of the end effector in Cartesian space.
      endEffectorY - The y-position of the end effector in Cartesian space.
      Returns:
      A Tuple2 of up to 2 (possibly 0!) unique valid inverse kinematic solutions.