Engineering
How a PID Controller Stabilizes a Drone's Hover
Quick fact
A typical consumer drone runs its PID loop at around 400 Hz—that's 400 corrections every second—to keep itself from tumbling out of the sky.
Why this is interesting
Ever wondered how a drone holds perfectly still in the air? The secret is a humble algorithm that corrects its mistakes hundreds of times per second.
Read the full explanation
Understanding How a PID Controller Stabilizes a Drone's Hover
Imagine balancing a broomstick on your palm. You constantly feel it tilting and move your hand to keep it upright. A drone does the same, but with rotors. The PID controller is the 'brain' that decides how to adjust each rotor's speed based on the error—the difference between where the drone is and where it should be. It has three parts: the proportional term reacts to the current size of the error, the integral term accounts for past errors that haven't been fully corrected, and the derivative term predicts future errors by looking at how fast the error is changing. Each term contributes a correction, and the sum is sent to the motors to push the drone back toward the target.
A deeper explanation
The PID controller works in a continuous feedback loop. Sensors (gyroscopes and accelerometers) measure the drone's orientation and position. The error is computed, and the PID algorithm calculates an output. The proportional term scales with the error (Kp × error), giving a strong immediate push for large errors. The integral term sums up accumulated error over time (Ki × ∫error dt), eliminating steady-state errors like a constant wind pushing the drone. The derivative term predicts the error's slope (Kd × d(error)/dt), damping oscillations and preventing overshoot. The weighted sum is converted to motor commands, adjusting rotor speeds. When the drone tilts, the controller increases the speed of rotors on the low side and decreases on the high side, generating a corrective torque. This loop runs at high frequency, continuously refining adjustments to maintain a stable hover despite disturbances.