Handheld UXO Sensor Improvements to Facilitate UXO/Clutter Discrimination. Volume 2: Signal Processing for Handheld UXO Improvements

Abstract

Abstract : The goal of this work is to develop robust algorithms to precisely determine the position of a handheld UXO sensor as it is swept above a suspected UXO object. It is critical that the sensor position be known precisely because research results have established that one of the most important factors in using UXO sensor data to characterize buried targets is precise knowledge of the sensor location and attitude while the data are being collected. To assist in tracking the sensor position, an inertial measurement unit (IMU) is integrated with the sensor to record the sensor motion. Specifically, the sensor accelerations in the x-, y-, and z-coordinate directions are recorded, as well as the rotation rates about those axes. The algorithms under development are intended to determine the position and attitude of the handheld UXO sensor using the information recorded by the IMU. The IMU accelerometers and angular rate sensor are most accurate during different types of motion and have different limitations. The accelerometer measurements are quite stable over long time periods, but are prone to errors due to saturation in response to very quick motions. The angular rate sensors, on the other hand, are quite accurate over short time periods, including during quick motions, but tend to suffer from drift over long time periods. Thus, the angular rate sensor can be used to compensate for the accelerometer saturation during quick motions and the accelerometer can be used to compensate for the angular rate sensor drift over long time periods. Adaptive error mitigation algorithms, which exploit these differences in the accelerometers and angular rate sensors are developed. These algorithms employ a feedback loop to use the more accurate sensor (accelerometer or angular rate) to mitigate errors in the less accurate sensor (accelerometer or angular rate).