The output angular velocity of the gyroscope is instantaneous. Generally, the angular velocity balance cannot be directly used. Most inertial navigation systems require angle signals. Therefore, the angular velocity and time integral are needed to calculate the angle. The obtained angular variation is added to the initial angle. The target angle, in which the smaller the integration time Dt is, the more accurate the output angle is, but the principle of the gyroscope determines that its measurement reference is itself, and there is no absolute reference object outside the system. Plus Dt is impossible to be infinitely small, so the integral The cumulative error increases rapidly over time, eventually causing the output angle to be inconsistent with the actual, so the gyroscope can only operate on a relatively short time scale.
The acceleration measurement is the direction of gravity. There is an absolute reference object “gravity axis” outside the system. In the case of no external force acceleration, the ROLL/PITCH two-axis attitude angle can be accurately output, and there is no cumulative error in this angle. The time scale is accurate. However, the acceleration sensor has a disadvantage in measuring the angle. The acceleration sensor actually uses MEMS technology to detect the small deformation caused by the inertial force. The inertial force and the essence of gravity are one thing, so it does not distinguish between the acceleration of gravity and the acceleration of external force. When the three-dimensional space is doing the shifting motion, its output is not correct. Unfortunately, most systems that require an inertial attitude angle are not working at rest.
Therefore, on the basis of no other reference objects, to obtain a more realistic attitude angle, it is necessary to develop strengths and avoid weaknesses, combine the advantages of both, and the simplest way to abandon their respective shortcomings is weighting. The design algorithm increases the gyroscope in a short time scale. Weight, increase the acceleration weight in a longer time scale, so the system output angle is more real.
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