Hoverboards: Self-Balancing Tech & PID

A hoverboard (or a Segway, or a Onewheel) looks impossible. It has two wheels on the same axis. If you stand on steps, it should tip over instantly. Yet, you lean forward, and it zooms forward. You lean back, it stops. You stand still, and it feels rock solid. It is solving one of the most classic physics problems in history: The Inverted Pendulum.

The Broomstick Analogy

Balance a broomstick vertically on the palm of your hand.

• If the broom tips forward, what do you do? You run forward.
• By moving the base under the center of gravity, you catch the fall. This is exactly what the hoverboard does.

1. Sensor: The internal Gyroscope/IMU detects: “I am tipping forward by 1 degree.”
2. Controller: The computer calculates: “I need to speed up the wheels to catch the fall.”
3. Actuator: The motors spin forward.

This happens 100 times a second. The board is constantly “falling,” and the motors are constantly “catching” it.

The PID Loop (The Secret Sauce)

To make this smooth (so you don’t jitter back and forth violently), engineers use a PID Controller. It stands for Proportional - Integral - Derivative.

• P (Proportional): “I’m tipping a little? Move a little. I’m tipping a lot? Move fast!”
• I (Integral): “I’m carrying a heavy backpack and I’m still slightly tilted? Add more power to fix this steady error.”
• D (Derivative): “Whoa, I’m returning to vertical really fast! Slow down so I don’t overshoot and fall backward!”

Without the “D” term, the hoverboard would wobble violently and throw you off. The D term acts as a “Software Shock Absorber.”

Robotics Application

We rarely build balancing robots in competition (too risky; if the battery dies, the robot falls over). But we use this exact same math for Lift Control.

• Scenario: We have a heavy claw on an arm. We want to hold it exactly 20 inches in the air.
• Gravity: Tries to pull it down.
• PID: The code fights gravity. If the arm droops 1mm, the motor power increases slightly to push it back.

If you can tune a PID loop, you can make anything stable—whether it’s a 30lb robot stacking cones, or a $200 toy from the mall keeping you unrelated.