NextFTC Documentation

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Feedback Elements ​

A feedback element is any type of closed-loop (feedback) control. For example, a PID controller, SquID controller, and bang-bang controller are all feedback elements.

To add a feedback element, call the feedback function in a control system builder.

kotlin
controlSystem {
    feedback(/* feedback element */)
}

PID Element ​

To create a PID element, use the posPid or velPid functions in a control system builder. Pass either the three PID gains or a PIDCoefficients object.

kotlin
controlSystem {
    posPid(p, i, d)
}

SquID Element ​

SquID control is the same as PID control, but the output of the proportional component is square-rooted.

To create a SquID element, use the posSquid or velSquid functions in a control system builder. Pass either the three PID gains or a PIDCoefficients object.

kotlin
controlSystem {
    posSquid(p, i, d)
}

Bang Bang Element ​

TODO

Angular Element ​

When dealing with a continuous-angle system (one that can turn in a full circle, such as a robot's heading or a turret), you should use an angular element for position control. This allows it to always take the shortest path to the target.

IMPORTANT

Your position error must be in the provided unit. To do this, use a custom filter. You can see how to do this on the arms example page.

You pass the angle unit along with another feedback element for it to wrap. For example:

kotlin
controlSystem {
    angular(AngleType.DEGREES) {
        posPid(p, i, d)
    }
}

Custom Feedback Elements ​

To create a custom feedback element, implement the FeedbackElement interface and pass it to the feedback function in a control system builder. For example:

kotlin
class FullPowerFeedback : FeedbackElement {
    override fun calculate(error: KineticState): Double {
        return 1.0
    }
}

controlSystem {
    feedback(FullPowerFeedback())
}