Admittance space stability analysis of power electronic systems

Instrument axes of line-of-sight sensors are normally boresighted to aircraft body axes through ground based techniques. Due to limitations in the boresight equipment, remaining residual errors result in degraded system performance. A method for a continuous in-flight calibration of the boresight residual errors is presented. This improves dramatically the accuracy of the line-of-sight pointing mechanization, and it also eliminates the need for periodic ground based recalibrations which tend to be labor intensive and expensive. The method utilizes a Kalman filter that estimates the boresight errors based on the difference between the expected and measured line of sight of a surveyed ground target. The aircraft position and the surveyed target location define the expected line of sight, and the azimuth and elevation angles of the sensor gimbals define the measured line of sight. The accuracy of a shipboard INS/GPS navigator is sufficient to make the analytic calibration practical. The benefits of the method are demonstrated through flight test results.