Package frc.lib.math

Class ArmFeedForwardTunable

java.lang.Object
frc.lib.math.ArmFeedForwardTunable
public class ArmFeedForwardTunable extends Object
A helper class that computes feedforward outputs for a simple arm (modeled as a motor acting against the force of gravity on a beam suspended at an angle).

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    double
    ka
     
    double
    kg
     
    double
    ks
     
    double
    kv
     

  • Constructor Summary

    Constructors
    Constructor
    Description
    ArmFeedForwardTunable(double ks, double kg, double kv)
    Creates a new ArmFeedforward with the specified gains.
    ArmFeedForwardTunable(double ks, double kg, double kv, double ka)
    Creates a new ArmFeedforward with the specified gains.

  • Method Summary

    Modifier and Type
    Method
    Description
    double
    calculate(double positionRadians, double velocity)
    Calculates the feedforward from the gains and velocity setpoint (acceleration is assumed to be zero).
    double
    calculate(double positionRadians, double velocityRadPerSec, double accelRadPerSecSquared)
    Calculates the feedforward from the gains and setpoints.
    double
    maxAchievableAcceleration(double maxVoltage, double angle, double velocity)
    Calculates the maximum achievable acceleration given a maximum voltage supply, a position, and a velocity.
    double
    maxAchievableVelocity(double maxVoltage, double angle, double acceleration)
    Calculates the maximum achievable velocity given a maximum voltage supply, a position, and an acceleration.
    double
    minAchievableAcceleration(double maxVoltage, double angle, double velocity)
    Calculates the minimum achievable acceleration given a maximum voltage supply, a position, and a velocity.
    double
    minAchievableVelocity(double maxVoltage, double angle, double acceleration)
    Calculates the minimum achievable velocity given a maximum voltage supply, a position, and an acceleration.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • ks

      public double ks

    • kg

      public double kg

    • kv

      public double kv

    • ka

      public double ka

  • Constructor Details

    • ArmFeedForwardTunable

      public ArmFeedForwardTunable(double ks, double kg, double kv, double ka)
      Creates a new ArmFeedforward with the specified gains. Units of the gain values will dictate units of the computed feedforward.
      Parameters:
      ks - The static gain.
      kg - The gravity gain.
      kv - The velocity gain.
      ka - The acceleration gain.

    • ArmFeedForwardTunable

      public ArmFeedForwardTunable(double ks, double kg, double kv)
      Creates a new ArmFeedforward with the specified gains. Acceleration gain is defaulted to zero. Units of the gain values will dictate units of the computed feedforward.
      Parameters:
      ks - The static gain.
      kg - The gravity gain.
      kv - The velocity gain.

  • Method Details

    • calculate

      public double calculate(double positionRadians, double velocityRadPerSec, double accelRadPerSecSquared)
      Calculates the feedforward from the gains and setpoints.
      Parameters:
      positionRadians - The position (angle) setpoint. This angle should be measured from the horizontal (i.e. if the provided angle is 0, the arm should be parallel with the floor). If your encoder does not follow this convention, an offset should be added.
      velocityRadPerSec - The velocity setpoint.
      accelRadPerSecSquared - The acceleration setpoint.
      Returns:
      The computed feedforward.

    • calculate

      public double calculate(double positionRadians, double velocity)
      Calculates the feedforward from the gains and velocity setpoint (acceleration is assumed to be zero).
      Parameters:
      positionRadians - The position (angle) setpoint. This angle should be measured from the horizontal (i.e. if the provided angle is 0, the arm should be parallel with the floor). If your encoder does not follow this convention, an offset should be added.
      velocity - The velocity setpoint.
      Returns:
      The computed feedforward.

    • maxAchievableVelocity

      public double maxAchievableVelocity(double maxVoltage, double angle, double acceleration)
      Calculates the maximum achievable velocity given a maximum voltage supply, a position, and an acceleration. Useful for ensuring that velocity and acceleration constraints for a trapezoidal profile are simultaneously achievable - enter the acceleration constraint, and this will give you a simultaneously-achievable velocity constraint.
      Parameters:
      maxVoltage - The maximum voltage that can be supplied to the arm.
      angle - The angle of the arm. This angle should be measured from the horizontal (i.e. if the provided angle is 0, the arm should be parallel with the floor). If your encoder does not follow this convention, an offset should be added.
      acceleration - The acceleration of the arm.
      Returns:
      The maximum possible velocity at the given acceleration and angle.

    • minAchievableVelocity

      public double minAchievableVelocity(double maxVoltage, double angle, double acceleration)
      Calculates the minimum achievable velocity given a maximum voltage supply, a position, and an acceleration. Useful for ensuring that velocity and acceleration constraints for a trapezoidal profile are simultaneously achievable - enter the acceleration constraint, and this will give you a simultaneously-achievable velocity constraint.
      Parameters:
      maxVoltage - The maximum voltage that can be supplied to the arm.
      angle - The angle of the arm. This angle should be measured from the horizontal (i.e. if the provided angle is 0, the arm should be parallel with the floor). If your encoder does not follow this convention, an offset should be added.
      acceleration - The acceleration of the arm.
      Returns:
      The minimum possible velocity at the given acceleration and angle.

    • maxAchievableAcceleration

      public double maxAchievableAcceleration(double maxVoltage, double angle, double velocity)
      Calculates the maximum achievable acceleration given a maximum voltage supply, a position, and a velocity. Useful for ensuring that velocity and acceleration constraints for a trapezoidal profile are simultaneously achievable - enter the velocity constraint, and this will give you a simultaneously-achievable acceleration constraint.
      Parameters:
      maxVoltage - The maximum voltage that can be supplied to the arm.
      angle - The angle of the arm. This angle should be measured from the horizontal (i.e. if the provided angle is 0, the arm should be parallel with the floor). If your encoder does not follow this convention, an offset should be added.
      velocity - The velocity of the arm.
      Returns:
      The maximum possible acceleration at the given velocity.

    • minAchievableAcceleration

      public double minAchievableAcceleration(double maxVoltage, double angle, double velocity)
      Calculates the minimum achievable acceleration given a maximum voltage supply, a position, and a velocity. Useful for ensuring that velocity and acceleration constraints for a trapezoidal profile are simultaneously achievable - enter the velocity constraint, and this will give you a simultaneously-achievable acceleration constraint.
      Parameters:
      maxVoltage - The maximum voltage that can be supplied to the arm.
      angle - The angle of the arm. This angle should be measured from the horizontal (i.e. if the provided angle is 0, the arm should be parallel with the floor). If your encoder does not follow this convention, an offset should be added.
      velocity - The velocity of the arm.
      Returns:
      The minimum possible acceleration at the given velocity.