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
    double ka
    The acceleration gain.
    double kg
    The gravity gain.
    double ks
    The static gain.
    double kv
    The velocity gain.
    static ElevatorFeedforwardProto proto
    ElevatorFeedforward protobuf for serialization.
    static 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.

  • Method Summary

    Modifier and Type Method Description
    double calculate​(double velocity)
    Calculates the feedforward from the gains and velocity setpoint (acceleration is assumed to be zero).
    double calculate​(double velocity, double acceleration)
    Calculates the feedforward from the gains and setpoints.
    double calculate​(double currentVelocity, double nextVelocity, double dtSeconds)
    Calculates the feedforward from the gains and setpoints.
    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.

    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)
      Creates a new ElevatorFeedforward 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.
      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. 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 velocity, double acceleration)
      Calculates the feedforward from the gains and setpoints.
      Parameters:
      velocity - The velocity setpoint.
      acceleration - The acceleration setpoint.
      Returns:
      The computed feedforward.

    • calculate

      public double calculate​(double currentVelocity, double nextVelocity, double dtSeconds)
      Calculates the feedforward from the gains and setpoints.

      Note this method is inaccurate when the velocity crosses 0.

      Parameters:
      currentVelocity - The current velocity setpoint.
      nextVelocity - The next velocity setpoint.
      dtSeconds - Time between velocity setpoints in seconds.
      Returns:
      The computed feedforward.

    • calculate

      public double calculate​(double velocity)
      Calculates the feedforward from the gains and velocity setpoint (acceleration is assumed to be zero).
      Parameters:
      velocity - The velocity setpoint.
      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.
      acceleration - The acceleration of the elevator.
      Returns:
      The maximum possible velocity 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.
      acceleration - The acceleration of the elevator.
      Returns:
      The minimum possible velocity 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.
      velocity - The velocity of the elevator.
      Returns:
      The maximum possible acceleration 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.
      velocity - The velocity of the elevator.
      Returns:
      The minimum possible acceleration at the given velocity.