# US 2016/0259337 A1 · Method and Device for In-Flight Terrain Identification for Microdrone > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2016/0259337 A1 - Document ID: US20160259337A1 - Status: Published application - Kind: A1 - Application number: 15/030,351 - Filed: 2014-10-16 - Published: 2016-09-08 - Earliest claimed: 2013-10-18 - Assignees: Universite D'Aix-Marseille; Centre National De La Recherche Scientifique - Applicants: Universite d'Aix-Marseille; Centre national de la recherche scientifique - Inventors: Franck RUFFIER; Fabien EXPERT - Web page: https://patentgrep.com/patent/US20160259337A1 ## CPC - G05D 1/0607: {specially adapted for aircraft} - B64U 10/80: UAVs characterised by their small size, e.g. micro air vehicles [MAV] - B64U 50/19: using electrically powered motors - G01C 21/20: Instruments for performing navigational calculations (G01C21/24, G01C21/26 take precedence) - G01C 23/00: Combined instruments indicating more than one navigational value, e.g. for aircraft; Combined measuring devices for measuring two or more variables of movement, e.g. distance, speed or acceleration - G01F 1/00: Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow (measuring a proportion of the volume flow G01F5/00) - G05D 1/0094: {involving pointing a payload, e.g. camera, weapon, sensor, towards a fixed or moving target} - G05D 1/2435: {Extracting 3D information} - G05D 1/628: following the obstacle profile, e.g. a wall or undulated terrain - G05D 1/689: Pointing payloads towards fixed or moving targets (positioning towed, pushed or suspended implements G05D1/672) - G08G 5/74: for monitoring terrain - B64U 2101/55: for life-saving or rescue operations; for medical use - B64U 2201/10: autonomous, i.e. by navigating independently from ground or air stations, e.g. by using inertial navigation systems [INS] - G05D 2105/80: for information gathering, e.g. for academic research - G05D 2109/254: {Flying platforms, e.g. multicopters} - G05D 2111/10: Optical signals - G05D 2111/65: {taken successively, e.g. visual odometry or optical flow} - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - B64U: UNMANNED AERIAL VEHICLES [UAV]; EQUIPMENT THEREFOR - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - G08G: TRAFFIC CONTROL SYSTEMS (guiding railway traffic, ensuring the safety of railway traffic B61L; arrangement of road signs or traffic signals E01F9/00; radar or analogous systems, sonar systems, lidar systems specially adapted for traffic control G01S13/91, G01S15/88, G01S17/88; {radar or analogous systems, sonar systems, lidar systems specially adapted for anti-collision purposes G01S13/93, G01S15/93, G01S17/93}) ## Abstract The invention relates to a surface identification device for the movement of a vehicle at a distance from that surface, the device comprising a detection head, the head including at least one sensor of a property depending on the distance of the center of the head from the surface, each sensor covering a detection zone centered on a line of sight, an orientation system for the detection zone of each sensor, and a controller processing the signals from each sensor and controlling the system based on said signals. The controller estimates the direction of the perpendicular to the surface, and uses said system to rotate the line of sight of each sensor in a separate direction by a reorientation angle of the direction of said perpendicular. ## Claims ### Claim 1 A surface identification device for the autonomous movement of a moving vehicle at a distance from that surface, the surface identification device comprising: a) a surface detection head defining a coordinate system fixed to the detection head with an origin at the center of the detection head, an axis of advance, a drift axis, an ascent axis, the detection head including at least one sensor for a quantity depending on the distance of the center of the detection head from the surface, each sensor covering a detection zone centered on a line of sight; b) an orientation system for orienting the detection zone of each sensor by rotating the detection zone around the drift axis; and c) a controller suitable for receiving and processing the signals from each sensor and controlling the system for orienting the detection zone based on said signals, wherein the controller is configured for estimating the direction of the perpendicular to the surface in said coordinate system based on said signals, and for using said orientation system to rotate the line of sight of the viewing zone of each sensor into a direction separated by a determined reorientation angle from the direction of said perpendicular. ### Claim 2 (depends on 1) The device according to claim 1, wherein the reorientation angle is comprised between 0 and 90°. ### Claim 3 (depends on 1) The device according to claim 1, wherein each sensor is an optical flow sensor, and wherein the controller is configured for estimating the direction of the perpendicular to the surface by determining the maximum optical flow direction based on the signals delivered by each optical flow sensor. ### Claim 4 (depends on 3) The device according to claim 3, wherein the controller is configured for determining the maximum optical flow direction by carrying out the following steps: a) determining the function of the optical flow from the orientation of the line of sight of the detection zone in said coordinate system by regression analysis of the optical flow signals provided by each optical flow sensor; and b) determining the orientation of the line of sight of the detection zone for which said function has a maximum. ### Claim 5 (depends on 1) The device according to claim 1, wherein the controller is further configured for computing a confidence index based on said signals, and validating or rejecting the estimate of the direction of the perpendicular to the surface based on the value of the confidence index. ### Claim 6 (depends on 1) The device according to claim 1, wherein the detection head comprises four optical flow sensors, i.e., a front ventral sensor, a rear ventral sensor, a front dorsal sensor, and a rear dorsal sensor. ### Claim 7 (depends on 1) The device according to claim 1, wherein the detection zone orientation system comprises an actuator able to rotate the surface detection head around the drift axis. ### Claim 8 (depends on 1) The device according to claim 1, provided with an optical flow measuring assembly comprising a matrix of photodetectors covering a detection field of substantially 360°×60° around the drift axis, and wherein the orientation system of the detection zone is able to select one or more subsets of said photodetectors to represent each of said sensors. ### Claim 9 (depends on 1) The device according to claim 1, wherein the detection head is further equipped with at least one gyro-stabilization sensor of the detection head to compensate the rotational movements of said moving vehicle during flight. ### Claim 10 (depends on 7) An aerial microdrone with autonomous movement comprising a device according to claim 7, the controller being configured for controlling the actuator so as to align the axis of ascent of the detection head in the estimated direction of the perpendicular to the surface and thus to keep the axis of advance of the detection head parallel to the local slope of the surface overflown by the microdrone. ### Claim 11 (depends on 10) The microdrone according to claim 10, further comprising a gyrometer or an airspeed indicator or both for controlling the linear advance speed of the microdrone. ### Claim 12 A surface identification method during a movement at a distance from said surface, the method having the following steps: a) providing a detection zone centered on a line of sight; b) measuring a quantity depending on said distance from the surface in the provided detection zone; c) estimating the direction of the perpendicular to the surface and thus the minimum distance direction from the surface based on the measured quantity; and d) reorienting the line of sight of the detection zone in a direction separated by a determined reorientation angle from the direction of said perpendicular. ### Claim 13 (depends on 12) The method according to claim 12, wherein step b) consists of measuring the optical flow, and step c) comprises: i) determining the function of the optical flow of the orientation of the line of sight of the detection zone by regression analysis of the optical flow measurements; and ii) determining the orientation of the line of sight of the detection zone for which said function has a maximum. ### Claim 14 (depends on 12) The method according to claim 12, carried out with a surface identification device for the autonomous movement of a moving vehicle at a distance from that surface, the surface identification device comprising: a) a surface detection head defining a coordinate system fixed to the detection head with an origin at the center of the detection head, an axis of advance, a drift axis, an ascent axis, the detection head including at least one sensor for a quantity depending on the distance of the center of the detection head from the surface, each sensor covering a detection zone centered on a line of sight; b) an orientation system for orienting the detection zone of each sensor by rotating the detection zone around the drift axis; and c) a controller suitable for receiving and processing the signals from each sensor and controlling the system for orienting the detection zone based on said signals, wherein the controller is configured for estimating the direction of the perpendicular to the surface in said coordinate system based on said signals, and for using said orientation system to rotate the line of sight of the viewing zone of each sensor into a direction separated by a determined reorientation angle from the direction of said perpendicular. ### Claim 15 (depends on 4) The device according to claim 4, wherein step a) is carried out using the least squares method. ### Claim 16 (depends on 4) The device according to claim 4, wherein step b) is carried out by differentiation of said function. ### Claim 17 (depends on 7) The device according to claim 7, wherein the actuator is a stepping motor. ### Claim 18 (depends on 13) The method according to claim 13, wherein step i) is carried out using the least squares method. ### Claim 19 (depends on 13) The method according to claim 13, wherein step ii) is carried out by differentiation of said function.