A FAULT TOLERANT, DATA FUSION SYSTEM FOR NAVIGATION APPLICATIONS TO A DUCTED FAN VTOL UAV

A Fault Tolerant, Data Fusion (FTDF) algorithm for a Ducted Fan Unmanned Aerial Vehicle (DFUAV) Navigation System is presented. The algorithm have two parts: Gradient Descent (GD) for the Attitude and Heading Reference System (AHRS) and an Interacting Multiple Model (IMM) for position estimation. The GD methodology was designed to fuse the gyroscope, accelerometer, and geomagnetic sensors. The IMM algorithm is able to identify and compensate for multiple sensors data failures. There are three parts in the presentation. Firstly, system identification and the Allan Variance method is used to build dynamic models and noise models for multiple Sensors and Actuators. Secondly, a GD filter is developed for application to the Inertial Measurement Unit (IMU) consisting of tri-axis gyroscopes, accelerometers and magnetometers. The GD filter implementation incorporates magnetic distortion and gyroscope bias drift compensation. The filter uses a quaternion representation, allowing accelerometer and magnetometer data to be used in an analytically derived and optimized algorithm to compute the direction of the gyroscope measurement error as a quaternion derivative. . Finally, the IMM algorithm is used to combine data from multiple sensors simultaneously. This filter uses multiple models that incorporate sensor failures. The probabilities of these models being correct is generated by the IMM. These probabilities can be used to identify sensor failures and compensate for these failures