Calibration and Initial Alignment of Low Cost MEMS Inertial Navigation Sensors for UAV Application

Abstract

This work deals with an simple approach to calibrate low cost six degree of freedom MEMS inertial Navigation system to be used in Unmanned Air Vehicle (UAV). The accelerometer and gyroscope are modelled with inter axis misalignment correction. To determine calibration parameters of a tri axis accelerometer at least nine equations will be required to solve for nine unknowns (3 scale factor, 3 zero bias, 3 misalignment angles). In this simple approach three new linear equations were formulated to determine the calibration parameters thereby reducing number of positions needed in multi position test. The formulated methodology for accelerometer is validated by conducting twelve position tests. All combination of positions were attempted iteratively. After identifying the singularities, the study on the results suggests that only six positions are enough to solve nine unknowns. Similar methodology was applied to calibrate tri axial Gyroscope in rate test. Rate test results were studied and analysed with standard values provided my sensor manufacturer. A strap down inertial navigation system (SINS) error model is introduced, and the observability of the SINS error model is analyzed. Then on the basis of this SINS error model and a kalman filter is used to estimate the states of the error models. Based on the analysis of computer simulation results, a fast and precision initial alignment method is proposed for SINS on stationary base.