Package edu.wpi.first.math.controller

Class ElevatorFeedforward

java.lang.Object
edu.wpi.first.math.controller.ElevatorFeedforward
All Implemented Interfaces:
ProtobufSerializable, StructSerializable, WPISerializable
public class ElevatorFeedforward extends Object implements ProtobufSerializable, StructSerializable
A helper class that computes feedforward outputs for a simple elevator (modeled as a motor acting against the force of gravity).

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final ElevatorFeedforwardProto
    proto
    ElevatorFeedforward protobuf for serialization.
    static final ElevatorFeedforwardStruct
    struct
    ElevatorFeedforward struct for serialization.

  • Constructor Summary

    Constructors
    Constructor
    Description
    ElevatorFeedforward(double ks, double kg, double kv)
    Creates a new ElevatorFeedforward with the specified gains.
    ElevatorFeedforward(double ks, double kg, double kv, double ka)
    Creates a new ElevatorFeedforward with the specified gains.
    ElevatorFeedforward(double ks, double kg, double kv, double ka, double dt)
    Creates a new ElevatorFeedforward with the specified gains and period.

  • Method Summary

    Modifier and Type
    Method
    Description
    double
    calculate(double velocity)
    Calculates the feedforward from the gains and velocity setpoint assuming continuous control (acceleration is assumed to be zero).
    double
    calculate(double currentVelocity, double nextVelocity)
    Calculates the feedforward from the gains and setpoints assuming discrete control.
    double
    getDt()
    Returns the period in seconds.
    double
    getKa()
    Returns the acceleration gain in V/(m/s²).
    double
    getKg()
    Returns the gravity gain in volts.
    double
    getKs()
    Returns the static gain in volts.
    double
    getKv()
    Returns the velocity gain in V/(m/s).
    double
    maxAchievableAcceleration(double maxVoltage, double velocity)
    Calculates the maximum achievable acceleration given a maximum voltage supply and a velocity.
    double
    maxAchievableVelocity(double maxVoltage, double acceleration)
    Calculates the maximum achievable velocity given a maximum voltage supply and an acceleration.
    double
    minAchievableAcceleration(double maxVoltage, double velocity)
    Calculates the minimum achievable acceleration given a maximum voltage supply and a velocity.
    double
    minAchievableVelocity(double maxVoltage, double acceleration)
    Calculates the minimum achievable velocity given a maximum voltage supply and an acceleration.
    void
    setKa(double ka)
    Sets the acceleration gain.
    void
    setKg(double kg)
    Sets the gravity gain.
    void
    setKs(double ks)
    Sets the static gain.
    void
    setKv(double kv)
    Sets the velocity gain.

    Methods inherited from class java.lang.Object

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

  • Field Details

  • Constructor Details

    • ElevatorFeedforward

      public ElevatorFeedforward(double ks, double kg, double kv, double ka, double dt)
      Creates a new ElevatorFeedforward with the specified gains and period.
      Parameters:
      ks - The static gain in volts.
      kg - The gravity gain in volts.
      kv - The velocity gain in V/(m/s).
      ka - The acceleration gain in V/(m/s²).
      dt - The period in seconds.
      Throws:
      IllegalArgumentException - for kv < zero.
      IllegalArgumentException - for ka < zero.
      IllegalArgumentException - for period ≤ zero.

    • ElevatorFeedforward

      public ElevatorFeedforward(double ks, double kg, double kv, double ka)
      Creates a new ElevatorFeedforward with the specified gains. The period is defaulted to 20 ms.
      Parameters:
      ks - The static gain in volts.
      kg - The gravity gain in volts.
      kv - The velocity gain in V/(m/s).
      ka - The acceleration gain in V/(m/s²).
      Throws:
      IllegalArgumentException - for kv < zero.
      IllegalArgumentException - for ka < zero.

    • ElevatorFeedforward

      public ElevatorFeedforward(double ks, double kg, double kv)
      Creates a new ElevatorFeedforward with the specified gains. Acceleration gain is defaulted to zero. The period is defaulted to 20 ms.
      Parameters:
      ks - The static gain in volts.
      kg - The gravity gain in volts.
      kv - The velocity gain in V/(m/s).
      Throws:
      IllegalArgumentException - for kv < zero.

  • Method Details

    • setKs

      public void setKs(double ks)
      Sets the static gain.
      Parameters:
      ks - The static gain in volts.

    • setKg

      public void setKg(double kg)
      Sets the gravity gain.
      Parameters:
      kg - The gravity gain in volts.

    • setKv

      public void setKv(double kv)
      Sets the velocity gain.
      Parameters:
      kv - The velocity gain in V/(m/s).

    • setKa

      public void setKa(double ka)
      Sets the acceleration gain.
      Parameters:
      ka - The acceleration gain in V/(m/s²).

    • getKs

      public double getKs()
      Returns the static gain in volts.
      Returns:
      The static gain in volts.

    • getKg

      public double getKg()
      Returns the gravity gain in volts.
      Returns:
      The gravity gain in volts.

    • getKv

      public double getKv()
      Returns the velocity gain in V/(m/s).
      Returns:
      The velocity gain.

    • getKa

      public double getKa()
      Returns the acceleration gain in V/(m/s²).
      Returns:
      The acceleration gain.

    • getDt

      public double getDt()
      Returns the period in seconds.
      Returns:
      The period in seconds.

    • calculate

      public double calculate(double velocity)
      Calculates the feedforward from the gains and velocity setpoint assuming continuous control (acceleration is assumed to be zero).
      Parameters:
      velocity - The velocity setpoint in meters per second.
      Returns:
      The computed feedforward.

    • calculate

      public double calculate(double currentVelocity, double nextVelocity)
      Calculates the feedforward from the gains and setpoints assuming discrete control.

      Note this method is inaccurate when the velocity crosses 0.

      Parameters:
      currentVelocity - The current velocity setpoint in meters per second.
      nextVelocity - The next velocity setpoint in meters per second.
      Returns:
      The computed feedforward.

    • maxAchievableVelocity

      public double maxAchievableVelocity(double maxVoltage, double acceleration)
      Calculates the maximum achievable velocity given a maximum voltage supply 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 elevator, in volts.
      acceleration - The acceleration of the elevator, in (m/s²).
      Returns:
      The maximum possible velocity in (m/s) at the given acceleration.

    • minAchievableVelocity

      public double minAchievableVelocity(double maxVoltage, double acceleration)
      Calculates the minimum achievable velocity given a maximum voltage supply 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 elevator, in volts.
      acceleration - The acceleration of the elevator, in (m/s²).
      Returns:
      The maximum possible velocity in (m/s) at the given acceleration.

    • maxAchievableAcceleration

      public double maxAchievableAcceleration(double maxVoltage, double velocity)
      Calculates the maximum achievable acceleration given a maximum voltage supply 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 elevator, in volts.
      velocity - The velocity of the elevator, in (m/s)
      Returns:
      The maximum possible acceleration in (m/s²) at the given velocity.

    • minAchievableAcceleration

      public double minAchievableAcceleration(double maxVoltage, double velocity)
      Calculates the minimum achievable acceleration given a maximum voltage supply 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 elevator, in volts.
      velocity - The velocity of the elevator, in (m/s)
      Returns:
      The maximum possible acceleration in (m/s²) at the given velocity.