Package edu.wpi.first.wpilibj.simulation

Class SingleJointedArmSim

java.lang.Object
edu.wpi.first.wpilibj.simulation.LinearSystemSim<N2,N1,N2>
edu.wpi.first.wpilibj.simulation.SingleJointedArmSim
public class SingleJointedArmSim extends LinearSystemSim<N2,N1,N2>
Represents a simulated single jointed arm mechanism.

  • Constructor Details

    • SingleJointedArmSim

      public SingleJointedArmSim(LinearSystem<N2,N1,N2> plant, DCMotor gearbox, double gearing, double armLength, double minAngleRads, double maxAngleRads, boolean simulateGravity, double startingAngleRads, double... measurementStdDevs)
      Creates a simulated arm mechanism.
      Parameters:
      plant - The linear system that represents the arm. This system can be created with LinearSystemId.createSingleJointedArmSystem(DCMotor, double, double).
      gearbox - The type of and number of motors in the arm gearbox.
      gearing - The gearing of the arm (numbers greater than 1 represent reductions).
      armLength - The length of the arm in meters.
      minAngleRads - The minimum angle that the arm is capable of.
      maxAngleRads - The maximum angle that the arm is capable of.
      simulateGravity - Whether gravity should be simulated or not.
      startingAngleRads - The initial position of the Arm simulation in radians.
      measurementStdDevs - The standard deviations of the measurements. Can be omitted if no noise is desired. If present must have 1 element for position.

    • SingleJointedArmSim

      public SingleJointedArmSim(DCMotor gearbox, double gearing, double j, double armLength, double minAngleRads, double maxAngleRads, boolean simulateGravity, double startingAngleRads, double... measurementStdDevs)
      Creates a simulated arm mechanism.
      Parameters:
      gearbox - The type of and number of motors in the arm gearbox.
      gearing - The gearing of the arm (numbers greater than 1 represent reductions).
      j - The moment of inertia of the arm in kg-m²; can be calculated from CAD software.
      armLength - The length of the arm in meters.
      minAngleRads - The minimum angle that the arm is capable of.
      maxAngleRads - The maximum angle that the arm is capable of.
      simulateGravity - Whether gravity should be simulated or not.
      startingAngleRads - The initial position of the Arm simulation in radians.
      measurementStdDevs - The standard deviations of the measurements. Can be omitted if no noise is desired. If present must have 1 element for position.

  • Method Details

    • setState

      public final void setState(double angleRadians, double velocityRadPerSec)
      Sets the arm's state. The new angle will be limited between the minimum and maximum allowed limits.
      Parameters:
      angleRadians - The new angle in radians.
      velocityRadPerSec - The new angular velocity in radians per second.

    • wouldHitLowerLimit

      public boolean wouldHitLowerLimit(double currentAngleRads)
      Returns whether the arm would hit the lower limit.
      Parameters:
      currentAngleRads - The current arm height.
      Returns:
      Whether the arm would hit the lower limit.

    • wouldHitUpperLimit

      public boolean wouldHitUpperLimit(double currentAngleRads)
      Returns whether the arm would hit the upper limit.
      Parameters:
      currentAngleRads - The current arm height.
      Returns:
      Whether the arm would hit the upper limit.

    • hasHitLowerLimit

      public boolean hasHitLowerLimit()
      Returns whether the arm has hit the lower limit.
      Returns:
      Whether the arm has hit the lower limit.

    • hasHitUpperLimit

      public boolean hasHitUpperLimit()
      Returns whether the arm has hit the upper limit.
      Returns:
      Whether the arm has hit the upper limit.

    • getAngle

      public double getAngle()
      Returns the current arm angle.
      Returns:
      The current arm angle in radians.

    • getVelocity

      public double getVelocity()
      Returns the current arm velocity.
      Returns:
      The current arm velocity in radians per second.

    • getCurrentDraw

      public double getCurrentDraw()
      Returns the arm current draw.
      Returns:
      The arm current draw in amps.

    • setInputVoltage

      public void setInputVoltage(double volts)
      Sets the input voltage for the arm.
      Parameters:
      volts - The input voltage.

    • estimateMOI

      public static double estimateMOI(double length, double mass)
      Calculates a rough estimate of the moment of inertia of an arm given its length and mass.
      Parameters:
      length - The length of the arm in m.
      mass - The mass of the arm in kg.
      Returns:
      The calculated moment of inertia in kg-m².

    • updateX

      protected Matrix<N2,N1> updateX(Matrix<N2,N1> currentXhat, Matrix<N1,N1> u, double dt)
      Updates the state of the arm.
      Overrides:
      updateX in class LinearSystemSim<N2,N1,N2>
      Parameters:
      currentXhat - The current state estimate.
      u - The system inputs (voltage).
      dt - The time difference between controller updates in seconds.
      Returns:
      The new state.