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.