  A simple approach to gyro and accelerometer bias estimation is proposed. It
does not involve Kalman filtering or similar formal techniques. Instead, it is
based on physical intuition and exploits a duality between gimbaled and
strapdown inertial systems. The estimation problem is decoupled into two
separate stages. At the first stage, inertial system attitude errors are
corrected by means of a feedback from an external aid. In the presence of
uncompensated biases, the steady-state feedback rebalances those biases and can
be used to estimate them. At the second stage, the desired bias estimates are
expressed in a closed form in terms of the feedback signal. The estimator has
only three tunable parameters and is easy to implement and use. The tests
proved the feasibility of the proposed approach for the estimation of low-cost
MEMS inertial sensor biases on a moving land vehicle.
