Optoelectronic speed measuring altimeters based on semiconductor lasers for UAV

Abstract

Considerations are being proposed to the new class of airborne laser facilities for unmanned aerial vehicle (UAV), specifically concerning to the on-board laser altimeter and vertical speed gauge (LASG) combined in one device. LASG is designed on the base of conventional units of a laser rangefinder. Distinguishing constructional peculiarities of LASG and its application features are shown. LASG implements the two methods of speed measuring. The first method comprises non-coherent accumulation of receiving signals with calculating the speed as a difference of two measured ranges divided by interval of time between them. The second method employs the linear regression method by finding the straight line that provides the least squares fitting to a series of distances measured in the monopulse mode. The last method could be applied at low altitudes of UAV (< 200 m), giving most accurate results, while the first method is more appropriate for high altitudes (up to 1000 m), where monopulse mode is rather energetically deficient. The ways to optimize these methods are discussed for various flight stages with regard to a function to be performed. The prototype of LASG is described.