In an FPV drone, the PID controller makes sure your stick inputs are executed as precisely and stably as possible. Imagine you push the stick forward. The controller constantly compares what you want (the setpoint) with what the drone is actually doing (the actual value). The difference between them is called the error, and the PID controller works to correct this error using three parts: P, I, and D.

• Proportional (P): Reacts directly to the current error. The bigger the difference between the desired and actual position, the stronger P corrects it. This makes the drone feel immediate and responsive. If the P value is too high, the drone may shake or oscillate during movements. If it’s too low, the drone feels sluggish or “soft.”
• Integral (I): Adds up small errors over time. For example, if the drone drifts slightly because of wind or extra weight, like a GoPro, I gradually corrects this long-term deviation. Without I, the drone would slowly drift. Too much I, however, makes control feel soft and can cause slow oscillations.
• Derivative (D): Looks not at the error itself, but at how fast the error is changing. It works like a shock absorber, preventing overshoot when the drone moves quickly or stops abruptly. D adds stability and smooths the response. If D is too low, the drone overshoots during movements. If it’s too high, the drone feels jittery, and the motors may sound rough because the system is over-correcting.

Together, P, I, and D create a control loop that makes the drone responsive, precise, and stable—a balance between speed, accuracy, and damping.