Class SimpleMotorFeedforward

java.lang.Object
org.wpilib.math.controller.SimpleMotorFeedforward
All Implemented Interfaces:
ProtobufSerializable, StructSerializable, WPISerializable
public class SimpleMotorFeedforward extends Object implements ProtobufSerializable, StructSerializable
A helper class that computes feedforward outputs for a simple permanent-magnet DC motor.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final SimpleMotorFeedforwardProto
    proto
    SimpleMotorFeedforward protobuf for serialization.
    static final SimpleMotorFeedforwardStruct
    struct
    SimpleMotorFeedforward struct for serialization.

  • Constructor Summary

    Constructors
    Constructor
    Description
    SimpleMotorFeedforward(double ks, double kv)
    Creates a new SimpleMotorFeedforward with the specified gains.
    SimpleMotorFeedforward(double ks, double kv, double ka)
    Creates a new SimpleMotorFeedforward with the specified gains and period.
    SimpleMotorFeedforward(double ks, double kv, double ka, double dt)
    Creates a new SimpleMotorFeedforward 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 reference assuming continuous control (acceleration is assumed to be zero).
    double
    calculate(double currentVelocity, double nextVelocity)
    Calculates the feedforward from the gains and references assuming discrete control.
    double
    getDt()
    Returns the period in seconds.
    double
    getKa()
    Returns the acceleration gain in V/(units/s²).
    double
    getKs()
    Returns the static gain in volts.
    double
    getKv()
    Returns the velocity gain in V/(units/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
    setKs(double ks)
    Sets the static gain.
    void
    setKv(double kv)
    Sets the velocity gain.

    Methods inherited from class Object

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

  • Field Details

  • Constructor Details

    • SimpleMotorFeedforward

      public SimpleMotorFeedforward(double ks, double kv, double ka, double dt)
      Creates a new SimpleMotorFeedforward with the specified gains and period.

      The units should be radians for angular systems and meters for linear systems.

      Parameters:
      ks - The static gain in volts.
      kv - The velocity gain in V/(units/s).
      ka - The acceleration gain in V/(units/s²).
      dt - The period in seconds.
      Throws:
      IllegalArgumentException - for kv < zero.
      IllegalArgumentException - for ka < zero.
      IllegalArgumentException - for period ≤ zero.

    • SimpleMotorFeedforward

      public SimpleMotorFeedforward(double ks, double kv, double ka)
      Creates a new SimpleMotorFeedforward with the specified gains and period. The period is defaulted to 20 ms.

      The units should be radians for angular systems and meters for linear systems.

      Parameters:
      ks - The static gain in volts.
      kv - The velocity gain in V/(units/s).
      ka - The acceleration gain in V/(units/s²).
      Throws:
      IllegalArgumentException - for kv < zero.
      IllegalArgumentException - for ka < zero.

    • SimpleMotorFeedforward

      public SimpleMotorFeedforward(double ks, double kv)
      Creates a new SimpleMotorFeedforward with the specified gains. Acceleration gain is defaulted to zero. The period is defaulted to 20 ms.

      The units should be radians for angular systems and meters for linear systems.

      Parameters:
      ks - The static gain in volts.
      kv - The velocity gain in V/(units/s).
      Throws:
      IllegalArgumentException - for kv < zero.

  • Method Details

    • setKs

      public void setKs(double ks)
      Sets the static gain.

      This setter is intended for online tuning only. Feedforward gains are assumed constant, so gain scheduling means the system was not correctly modeled.

      Parameters:
      ks - The static gain in volts.

    • setKv

      public void setKv(double kv)
      Sets the velocity gain.

      This setter is intended for online tuning only. Feedforward gains are assumed constant, so gain scheduling means the system was not correctly modeled.

      Parameters:
      kv - The velocity gain in V/(units/s).

    • setKa

      public void setKa(double ka)
      Sets the acceleration gain.

      This setter is intended for online tuning only. Feedforward gains are assumed constant, so gain scheduling means the system was not correctly modeled.

      Parameters:
      ka - The acceleration gain in V/(units/s²).

    • getKs

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

    • getKv

      public double getKv()
      Returns the velocity gain in V/(units/s).

      The units should be radians for angular systems and meters for linear systems.

      Returns:
      The velocity gain in V/(units/s).

    • getKa

      public double getKa()
      Returns the acceleration gain in V/(units/s²).

      The units should be radians for angular systems and meters for linear systems.

      Returns:
      The acceleration gain in V/(units/s²).

    • 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 reference assuming continuous control (acceleration is assumed to be zero).
      Parameters:
      velocity - The velocity reference.
      Returns:
      The computed feedforward.

    • calculate

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

      Note this method is inaccurate when the velocity crosses 0.

      Parameters:
      currentVelocity - The current velocity reference.
      nextVelocity - The next velocity reference.
      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.

      The units should be radians for angular systems and meters for linear systems.

      Parameters:
      maxVoltage - The maximum voltage that can be supplied to the motor, in volts.
      acceleration - The acceleration of the motor, in (units/s²).
      Returns:
      The maximum possible velocity in (units/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.

      The units should be radians for angular systems and meters for linear systems.

      Parameters:
      maxVoltage - The maximum voltage that can be supplied to the motor, in volts.
      acceleration - The acceleration of the motor, in (units/s²).
      Returns:
      The maximum possible velocity in (units/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.

      The units should be radians for angular systems and meters for linear systems.

      Parameters:
      maxVoltage - The maximum voltage that can be supplied to the motor, in volts.
      velocity - The velocity of the motor, in (units/s).
      Returns:
      The maximum possible acceleration in (units/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.

      The units should be radians for angular systems and meters for linear systems.

      Parameters:
      maxVoltage - The maximum voltage that can be supplied to the motor, in volts.
      velocity - The velocity of the motor, in (units/s).
      Returns:
      The maximum possible acceleration in (units/s²) at the given velocity.