Squid Controller

The Squid Controller is a variant of the PIDF Controller that square roots the output. The reason for this is the simple kinematic equation \({v_f}^2 = {v_i}^2 + 2ad \), where \(v_f\) is the final velocity, \(v_i\) is the initial velocity, \(a\) is the acceleration, and \(d\) is the displacement.

If we take the square root of both sides, we get \(v_f = \sqrt{{v_i}^2 + 2ad} \), which is the equation for the final velocity. Note that in a PID controller, we are minimizing the error by incorporating the position, velocity, and acceleration, which are the three terms in the equation above.

Since setting motor power effectively sets velocity¹, the output of the Squid Controller will be more kinematically accurate than the output of the PIDF Controller.

Another benefit of the Squid Controller is that it is nonlinear, which means that it can be more accurate than a linear controller in some cases. For example, a linear controller might not be able to accurately control a motor at low speeds, but a Squid Controller can.

Using SquidController

Using the SquidController is very similar to using the PIDFController. You can create an instance of it with the same constructor as the PIDFController, and the update method works the same way as the update method in the PIDFController.

Here is an example of how you might use the SquidController in an OpMode:

class MyOpMode : OpMode {
    private val motor by lazy { hardwareMap.get(DcMotorEx::class.java, "motor") }
    private val squidController by lazy { SquidController(PIDCoefficients(1.0, 0.0, 0.0)) } 
    //the coefficients are just placeholders, you should tune them to your motor

    override fun init() {
        squidController.targetPosition = 1000 //set the target position to 1000
    }

    override fun loop() {
        motor.power = squidController.update(motor.currentPosition)
        //update the motor power based on the current position *every loop*
    }
}

Actions that use the SquidController could thus be built in the same way as actions that use the PIDFController; since the SquidController is a subclass of the PIDFController, you can actually pass a SquidController object into an action that expects a PIDFController, such as the PIDFAction and PIDFActionEx from the Base Actions section.