core::Feedforward Class Reference

#include <feedforward.h>

Inheritance diagram for core::Feedforward:

Public Member Functions
	Feedforward (double kS, double kV, double kA)
double	calculate (double v, double a) const
double	max_vel (double max_voltage) const
double	max_acc (double max_voltage) const

Detailed Description

Stores feedforward constants and allows computation of voltage from reference vel/acc.

Feedforward should be used in systsems that require smooth precise movements and have high inertia, such as drivetrains and lifts. It is also useful for flywheels since they're so simple.

The formula used is:

output = kS * sign(v) + kV * v + kA * a

where:

• kS is the static gain (voltage required to overcome static friction)
• kV is the velocity gain (voltage required to maintain a constant velocity)
• kA is the acceleration gain (voltage required to accelerate at a constant rate)

This is best used alongside a PID loop:

output = pid.calculate() + feedforward.calculate(vel, acc)

In this case the feedforward does the heavy lifting and the PID corrects for small errors.

For information about tuning feedforward, I reccommend looking at this post: https://www.chiefdelphi.com/t/paper-frc-drivetrain-characterization/160915 (yes I know it's for FRC but trust me, it's useful)

Author

Ryan McGee, Jack Cammarata

Date

6/13/2022, 6/27/2025

Constructor & Destructor Documentation

Feedforward()

core::Feedforward::Feedforward ( double kS, double kV, double kA )

inline

Constructs a Feedforward with the given parameters.

Parameters

kS	The static gain.
kV	The velocity gain.
kA	The acceleration gain.

Member Function Documentation

calculate()

double core::Feedforward::calculate ( double v, double a ) const

inline

Calculates the output voltage based on the velocity and acceleration commands.

Parameters

v	The current velocity command.
a	The current acceleration command.

Returns

The calculated output voltage.

max_acc()

double core::Feedforward::max_acc ( double max_voltage ) const

inline

Calculates the maximum acceleration that can be achieved with a given maximum voltage.

Parameters

max_voltage

The maximum voltage that can be applied.

Returns

The maximum acceleration that can be achieved.

max_vel()

double core::Feedforward::max_vel ( double max_voltage ) const

inline

Calculates the maximum velocity that can be achieved with a given maximum voltage.

Parameters

max_voltage

The maximum voltage that can be applied.

Returns

The maximum velocity that can be achieved.

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The documentation for this class was generated from the following file:

• math/controls/feedforward.h