ABSTRACT
An inertial navigation system (INS) is a navigation aid that utilizes motion sensors (accelerometers), rotation sensors (gyroscopes) and a navigation processor to continuously calculate via dead reckoning the position, velocity, and orientation of a moving object. The principle of inertial navigation is simple. With precise knowledge of the initial position and attitude of a vehicle, at any time, single and double integration of the accelerometer outputs will provide velocity and position information, respectively, and the attitude can be obtained by integrating rotational rated from gyro measurements ([156]). In the process of calculating navigation parameters, attitude errors accumulate with time extendibility and induce other navigation errors because the attitude angle terms are integrated for velocity and position. Therefore, one of the most important problems for INS is initial alignment and calibration, which affects the navigation accuracy directly. The purpose of initial alignment of strapdown INS (SINS) is to determine the attitude matrix from body frame to navigation frame and to compensate for misalignment angles based on estimated values. The principle of initial alignment of SINS is similar to that of gimbaled INS (GINS), in both of which filtering is widely utilized as one of the key technologies.
