Determining angular altitude of airborne vehicle using infrared roll sensor

Abstract

Roll is the movement of airborne vehicle relative to longitudinal horizontal axis of inertia. A great while the problem of airborne vehicle orientation was solved by using mechanical gyroscopes that are bulky, heavy, labor-consuming devices for manufacturing and tuning. Run-down time of these devices is often insufficient for a long flight. MEMS technology development gave an option by way of MEMS gyroscopes. Yet, MEMS gyroscopes build up an error during their operation and it needs to be occasionally reset using another device. Thus, the task to develop the required sensor for using in airborne vehicles is very critical. Resetting such an orientation error requires getting information about airborne vehicle orientation by the way other than mechanical one: magnetic, optical, or thermometric ones. In the first instance, the sensor operates using Earth magnetic field and upon that having no adequate accuracy and thus no interest for the problem under consideration. In the second instance, analysis of the image is used from camera-equipped airborne vehicle where skyline slant is determined. This method enables to guide airborne vehicle with high accuracy, but it needs a powerful computing system capable of processing algorithm in real time. In the third instance, temperature contrast between Nadir and Zenith paths is used, which can be defined using non-contact temperature sensors, such as thermocouples or pyroelectric detectors. When reviewing methods to determine the roll for follow-up research, the roll sensor was selected as best suited to solve the problem as it uses temperature contrast between Nadir and Zenith paths. The operation principle of this roll sensor is described in detail. The impact of optical window design on IR sensors’ readings is made clear, and assessment of heating effect of body frame and ambient gases on thermocouples’ readings is given. The effect of weather conditions and underlying surface on the sensor is revealed as well. Results-based conclusion was drawn that IR sensors have a number of advantages as compared to other types of sensors, and they can be used to obtain data when guiding airborne vehicle.