SquIDF

package com.seattlesolvers.solverslib.controller

A SquIDF controller is a variation of the PIDF controller that square roots the positional error term. Effectively, it extends the PIDF class, and overrides the calculateOutput method. This modification changes how the controller responds to errors of different magnitudes.

Key Differences from PIDF

Aspect	PIDF	SquIDF
Proportional Response	Linear with error	Square root of error
Large Errors	Stronger correction	Moderate correction
Small Errors	Generally weaker correction	Stronger correction
Response Curve	Straight line	Curved (sub-linear)

SquIDF helps reduces overshoot (since the square root dampens aggressive corrections when initial error is high), and generally gives a smoother approach. However, like a PID/PIDF, tuning is critical. The controller is only as good as you can tune it.

Usage Example

// Create SquIDF controller with same gains as PIDF
SquIDFController squidfController = new SquIDFController(
    1.0,  // kP
    0.1,  // kI
    0.05, // kD
    0.2   // kF
);

// Use just like a PIDF controller
squidfController.setSetPoint(targetPosition);
double output = squidfController.calculate(currentPosition);

Tuning Notes

• kP values will typically need to be higher than in PIDF since √(e) < e for errors > 1

• Start with your PIDF gains and increase kP gradually

• The I, D, and F terms work pretty much identically to PIDF