When a coin rotates, it not only rotates around its own axis, but also makes a conical motion around the vertical axis. In other words, the gyro "rotates" around its own axis and "revolves" around the vertical axis. The speed at which the gyro "rotates" around its own axis determines the swing angle of the gyro. The slower the rotation, the greater the swing angle, the worse the stability, the faster the rotation, and the smaller the swing angle, the better the stability. This is similar to the reason why people ride bicycles. The difference is that one is linear motion and the other is conic motion. When the gyro rotates at high speed, under the action of gravity couple, it does not tip in the direction of the couple, but makes a conical motion around the vertical axis of the fulcrum. This is the gyro principle.