AHRS is commonly known as Attitude and Heading Reference System. AHRS is composed of an accelerometer, a magnetic field meter, and a gyroscope. The true reference of AHRS comes from the earth’s gravity field and the earth’s magnetic field measurement accuracy, and the gyro determines his dynamic performance. AHRS cannot work without Earth’s gravity and magnetic fields. Moreover, the more orthogonal the magnetic and gravitational fields, the better the attitude and attitude measurement. That is to say, if the magnetic field and the gravity field are parallel, for example, in the geomagnetic north and south poles, the magnetic field here and the gravity field are in the same direction. At this time, the route crossing cannot be measured. This is the flaw of the attitude and attitude system. At high latitudes, the line angle error will become larger and larger.
The university theoretical mechanics tells us that all motions can be decomposed into a linear motion and a rotational motion, so this inertial measurement unit measures these two types of motion, linear motion can be measured by an accelerometer, and rotational motion can be measured by a gyroscope. Assuming that the IMU’s gyroscope and accelerometer are measured without any error, then the gyroscope can accurately measure the attitude of the object. Accelerometers can be used to integrate the displacements to achieve a complete 6DOF, which means that the current attitude and relative displacement of the object can be known based on the IMU, and is not limited to any field.