The theoretical basis is Newton’s second law: According to basic physical principles, within a system, the speed cannot be measured, but its acceleration can be measured. If the initial velocity is known, the linear velocity can be calculated through integration, and then the linear displacement can be calculated, so it is actually an acceleration sensor that uses the principle of inertia. When the inclination sensor is stationary, that is, there is no acceleration in the lateral and vertical directions, then only the acceleration of gravity acts on it. The angle between the vertical axis of gravity and the sensitive axis of the acceleration sensor is the tilt angle. The inclination sensor in the general sense is static measurement or quasi-static measurement. Once there is external acceleration, the acceleration measured by the acceleration chip includes the external acceleration, so the calculated angle is not accurate. Therefore, the common method is to increase the mems gyroscope. Chip, and uses the priority Kalman filter algorithm. There are 3 axes of acceleration and 3 axes of gyroscope. All the products here are also called 6-axis or VG (vertical gyro).