Calibration of the Thermal Model of an Inertial Measurement Unit with Three Angular Rate Sensors

The paper considers the techniques developed for calibration of an inertial measurement unit (IMU) containing three angular rate sensors (ARS). Calibration is performed on a two-axis calibration turntable with a thermal chamber. For instrumental errors of ARS measurements, a priori parametric model is introduced, which includes biases, scale factor errors, small angles of nonorthogonality of sensitivity axes, and coefficients of temperature dependence for all these measurement errors. The problem of determining parameters of the parametric model is reduced to the problem of optimal estimation of the linear dynamic system state vector. In this context, the measurement vector is the vector of a small rotation between the model orientation of the IMU (calculated from the ARS readings) and the model orientation of the turntable faceplate (calculated from the turntable measurements). The approach proposed for formalization of the calibration problem is a modification of the method for calibration of an IMU as a whole inseparable unit, using a single-axis turntable with the horizontal axis of rotation, previously developed in the Laboratory of Control and Navigation of Lomonosov Moscow State University. The calibration experiment consists in a sequence of horizontal rotations about each of the ARS sensitivity axes. The results of numerical simulation and covariance analysis are considered.