The initial alignment solves the problem of establishing the navigation coordinate system; the compensation of apparent motion solves the problem of maintaining the navigation coordinate system; the compensation of harmful accelerations solves the problem of navigation calculation.
There are many ways of initial alignment. According to whether reference information needs to be introduced from the outside, it can be divided into autonomous alignment and non-autonomous alignment. The alignment achieved by relying only on the earth's gravity vector (measurement signal from the accelerometer) and the earth's rotation angular rate vector (measurement signal from the gyroscope) is called autonomous alignment, or self-alignment. Alignment that requires external equipment to provide reference information is called involuntary alignment, or external alignment. Outer alignment mainly refers to azimuth alignment (determining the initial heading). It is necessary to use optical or electromechanical means to introduce externally provided northbound reference information into the navigation computer of the inertial navigation system, and then the navigation computer controls the platform to achieve alignment. Although the accuracy of external alignment is very high, the equipment is quite complicated and the alignment time is long. It is only suitable for inertial navigation systems of long-range strategic missiles.
In addition, according to whether the carrier is moving, it can be divided into static base alignment and moving base alignment. The static base alignment is performed when the carrier is stationary with respect to the earth. Because the carrier is stationary, only the acceleration component of gravity is included in the output of the accelerometer, and it is aligned as an error signal. The alignment process is a process in which the acceleration component of gravity gradually approaches zero. The alignment accuracy depends on the acceleration. Meter zero. The moving base is aligned on a moving carrier.
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