Patent ID: 8599646
Filing Date: 2013-12-03
Classification: G01S

Abstract:
1. A method of estimating a distance by ultrasonic telemetry, said method being implemented by a drone (D 1 ), in particular for measuring the altitude (h) of the drone, comprising: a) emitting, from a time origin, an ultrasound burst, said burst being repeated at a predetermined recurrence frequency; b) after the end of each emission and over the duration of a time frame (n−1, n, n+1, . . . ) separating two consecutive emissions, receiving a plurality of successive signal peaks appearing at respective times of arrival during the same frame, wherein said successive signal peaks include spurious peaks (E′ characterized in that: c) for two consecutive frames, comparing the times of arrival of the p signal peaks of the current frame with the times of arrival of the q signal peaks of the previous frame, and determining, for each of the p.q pairs of peaks, a corresponding relative time gap; d) applying to the p.q relative time gaps determined at step c) at least one criterion of selection making it possible to retain only one peak of the current frame, wherein the step d) includes, as another criterion of selection, a filtering by which are retained only the peaks of the current frame for which the relative time gap with the peaks of the previous frame is lower than a predetermined threshold; and e) estimating the distance based on the time of arrival of the peak retained at step d) with respect to the time of emission of the last burst, wherein the respective recurrence frequencies of the considered drone (D 1 ) and of the other drone (D 2 ) are adjusted so that the difference between these frequencies verifies the following relation: wherein: F F V c is the velocity of sound propagation, W is the time width of the burst, and F