what is the difference between AHRS and IMU?

In fact, AHRS has one more magnetic field sensor than IMU. Why is the level of AHRS lower than IMU and it depends on gravity and magnetic field? This is determined by the sensor device architecture. AHRS sensors are usually low cost MEMS sensors. The noise of this kind of sensor’s gyroscope and accelerometer is relatively large. Take the planar gyroscope as an example, the integration of ADI’s gyroscope will drift about 2 degrees in one minute. If there is no magnetic field and gravity field to correct the With the axis gyroscope, the actual attitude and measured output attitude of the object will be completely changed after 3 minutes. Therefore, the field vector must be used for correction under the architecture of this low-cost gyroscope and accelerometer.

IMU is actually the same. Because we know that there are no absolutely accurate sensors, only relatively accurate sensors. IMUs use fiber optic gyroscopes or mechanical gyroscopes and accelerometer. This type of gyroscope with high cost. The accuracy is also relatively high compared to the MEMS gyroscope. High accuracy does not mean accuracy. The attitude accuracy parameter of the IMU is usually how many degrees an hour drifts.

The biggest difference between AHRS and IMU is that IMU is a measurement relative to the ideal attitude or relative attitude, and AHRS is a attitude measurement relative to the ground level. In the universe, there is no fixed counterpart for attitude reference. The measurement attitude using IMU can only be measured and described relative to the initial attitude or ideal attitude of the aircraft. AHRS is relative to the geoid and perpendicular to the level The gravity vertical line is used to measure and describe the attitude of the measured object, so the error is high in high latitudes. In short, I think that AHRS should be a special application of IMU and a subset of IMU applications.