Abstract
Self-alignment (or initial alignment) is the process by which the Inertial Navigation System (INS) is aligned using only measurements from the inertial sensors and the reference navigation information in the stationary state. The main purpose of self-alignment is to calculate the initial attitude of the INS. The accuracy of self-alignment is determined by the performance grade of the inertial sensors, for instance, the accuracy of the horizontal attitude by the horizontal accelerometer and the accuracy of the vertical attitude by the East-axis gyro. Therefore, uncertain errors in the inertial sensors degrade the performance of self-alignment. The focus of this paper is the temperature stabilizing error of accelerometers, a form of uncertain error. An analysis is presented of how the temperature stabilizing error affect the accuracy of self-alignment. From the analysis, a method is proposed to improve performance by curve fitting the horizontal control rates. This is then verified experimentally.
Highlights
An Inertial Navigation System (INS) provides position, velocity, attitude, angular velocity, and the acceleration of a vehicle by integrating measurements from the system’s Inertial Measurement Unit (IMU), which is essentially a set of accelerometers and gyros
We present an analysis of how errors in the temperature stabilizing state of the accelerometer affect the accuracy of self-alignment theoretically and in a simulation
To improve self-alignment performance, we suggest using the curve fitting method, which includes the construction of a measurement equation and estimation of a first-order coefficient using the Least
Summary
An Inertial Navigation System (INS) provides position, velocity, attitude, angular velocity, and the acceleration of a vehicle by integrating measurements from the system’s Inertial Measurement Unit (IMU), which is essentially a set of accelerometers and gyros. Unlike a radio navigation system, which calculates its position and velocity via position fixing, the INS relies on dead reckoning and must know its initial condition before starting calculation of the navigation information This process is called self-alignment, or initial alignment, and is used to obtain the initial attitude of the INS using measurements from the inertial sensors only, in the stationary state. This provides the essential initial condition from which to perform the subsequent recursive calculation of navigation information.
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