A Synthetic Airdata System

Abstract

A method for estimating airspeed, angle of attack, and sideslip without using conventional airdata sensors or pitot-static system is presented. The method relies on measurements from GPS, inertial measurement unit (IMU) and low-delity model of the aircraft dynamics which are fused using two, cascaded Extended Kalman Filters. The rst lter uses information from the IMU and GPS to estimate the aircraft’s absolute velocity and attitude. These estimates are used as the measurement updates for the second lter. These measurements along with the aircraft dynamics model are used to estimate airspeed, angle of attack and sideslip. Issues associated with using correlated estimates from the rst lter as measurements in the second lter are discussed. Simulation and ight test results of the method are presented. Simulation results show that airspeed estimation error is less than 1 m/s RMS. The nominal error from the ight test on airspeed, angle of attack and sideslip are less than 2.5 m/s, 2 degrees, and 1 degree, respectively. Factors that aect the accuracy of the solution are discussed.