Delay compensation in global estimation of rigid-body attitude under biased velocity measurement

Time delay in attitude determination systems is caused by low-quality date sampling, poor sensor synchronization, momentary sensor outage or operational restrictions of sensors. Despite, time delay can significantly degrade performance of attitude determination systems, the existing methods for attitude estimation neglect measurement delay. In this paper, we propose an asymptotically convergent attitude observer in presence of time delay in attitude measurements. We assume that only one vector measurement is available and furthermore the output of the rate gyro is contaminated by an unknown bias. The observer gain is calculated by solving a delay-dependent and time-varying linear matrix differential equation. A uniform observability condition is derived for ensuring solvability of the differential equation. A parameter adaptation law is used to estimate the gyro bias. Performance of the proposed observer is examined in case of a satellite system where the single delayed vector measurement is provided by a magnetometer.