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Author: Admin | 2025-04-28
Velocity feed forward (kF) is different from the Arbitrary Feed Forward in that it is a specialized feed forward designed to approximate the needed motor output to achieve a specified velocity.Do I need to calculate kF?If using any of the control modes, we recommend calculating the kF:Velocity Closed Loop: kF is multiplied by target velocity and added to output.Current (Draw) Closed Loop: kF is multiplied by the target current-draw and added to output.MotionMagic/ MotionProfile / MotionProfileArc: kF is multiplied by the runtime-calculated target and added to output.NoteWhen using position closed loop, it is generally desired to use a kF of ‘0’. During this mode target position is multiplied by kF and added to motor output. If providing a feedforward is necessary, we recommend using the arbitrary feed forward term (4 param Set) to better implement this.How to calculate kFUsing Tuner (Self-test Snapshot or Plotter), we’ve measured a peak velocity of 9326 native units per 100ms at 100% output. This can also be retrieved using getSelectedSensorVelocity (routine or VI).However, many mechanical systems and motors are not perfectly linear (though they are close). To account for this, we should calculate our feed forward using a measured velocity around the percent output we will usually run the motor.For our mechanism, we will typically be running the motor ~75% output. We then use Tuner (Self-test Snapshot or Plotter) to measure our velocity - in this case, we measure a velocity of 7112 native units per 100ms.Now let’s calculate a Feed-forward gain so that 75%
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