> For the complete documentation index, see [llms.txt](https://docs.cb21829.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cb21829.org/ftc-java-advanced-guide/feedback-control-pid-and-pidf.md).

# Feedback control: PID and PIDF

Everything advanced builds on feedback control. You measure the current state, compare it to the target, and command an output that reduces the error.

### The idea

A PID controller has three terms:

* **P** — reacts to current error.
* **I** — accumulates error over time.
* **D** — reacts to how fast the error changes.

```
output = Kp·error + Ki·∫error·dt + Kd·(d error / dt)
```

### A reusable PID controller

```java
import com.qualcomm.robotcore.util.ElapsedTime;

public class PIDController {
    private double kP, kI, kD;
    private double integralSum = 0;
    private double lastError = 0;
    private boolean hasRun = false;
    private final ElapsedTime timer = new ElapsedTime();

    public PIDController(double kP, double kI, double kD) {
        this.kP = kP; this.kI = kI; this.kD = kD;
    }

    public double calculate(double target, double state) {
        double error = target - state;

        if (!hasRun) {
            lastError = error;
            timer.reset();
            hasRun = true;
        }

        double dt = timer.seconds();
        double derivative = (error - lastError) / dt;
        integralSum += error * dt;

        double output = (kP * error) + (kI * integralSum) + (kD * derivative);

        lastError = error;
        timer.reset();
        return output;
    }

    public void reset() {
        integralSum = 0; lastError = 0; hasRun = false;
    }
}
```

Example use on a lift:

```java
PIDController liftPID = new PIDController(0.01, 0.0, 0.0004);

while (opModeIsActive()) {
    double power = liftPID.calculate(targetTicks, lift.getCurrentPosition());
    lift.setPower(power);
}
```

### Adding F with feedforward

Feedback reacts after error appears. Feedforward predicts the needed output before the error grows.

Common feedforward terms:

* `kG` for gravity
* `kV` for velocity
* `kA` for acceleration

```java
double power = liftPID.calculate(target, lift.getCurrentPosition()) + kG;
lift.setPower(power);
```

### Practical tuning

1. Set `kI = 0` and `kD = 0`.
2. Raise `kP` until the mechanism reaches target quickly.
3. Add `kD` to reduce overshoot.
4. Add a little `kI` only if steady-state error remains.

Use FTC Dashboard for live tuning when possible.

`RUN_TO_POSITION` is fine for simple cases. Use your own PIDF when you need custom behavior, feedforward, or motion profiling.


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