WO2018231166A1

WO2018231166A1 - Laser system for aerial navigation and landing

Info

Publication number: WO2018231166A1
Application number: PCT/TR2017/050263
Authority: WO
Inventors: Oguz TANRISEVER
Original assignee: Tanrisever Oguz
Priority date: 2017-06-14
Filing date: 2017-06-14
Publication date: 2018-12-20

Abstract

A laser system comprised of a laser beacon (2) on the ground, a laser receiver on an unmanned multicopter (3) and methods for navigation and landing. A hollow conical beam generated by the ground laser beacon defines a zone (1) covered by the laser light geometry. As the multicopter enters the zone, laser beam is intercepted by the laser receiver. INS (Inertial Navigation System) of the multicopter executes the navigation method to navigate it to the center of the zone. Multicopter position is updated by the INS using known coordinates of the center of the zone. Multicopter may choose to use updated position information to proceed with its flight to next beacon location or alternatively may choose to land at the current beacon location by executing the landing method.

Description

LASER SYSTEM FOR AERIAL NAVIGATION AND LANDING Technical Field

The present invention relates to an aerial navigation and landing system with a laser beacon placed on the ground, a laser receiver on board an unmanned multicopter, a navigation method and a landing method integrated with the INS (Inertial Navigation System) of the multicopter.

Background Art Aerial vehicles in general, unmanned multicopters in particular, are increasingly used for a wide variety of civilian and military tasks including automated delivery of packages, surveillance and reconnaissance. Autonomous navigation and landing of the unmanned aerial vehicles are an integral and crucial part of these tasks. Unmanned aerial vehicles mostly use GPS assisted INS systems for the autonomous navigation.

Various systems and methods for autonomous landing of aerial vehicles are known from the prior art. US2012/0076397A1 uses a plurality of optical guide beams for landing on a platform. This requires complex image analysis software and a beam acquisition camera on board. KR101651600 (B l) describes a system using a stereo camera for landing. It also requires a camera and complex image analysis software. EP1388772 describes an electro-optical system using a large number of wide angle emitter LED's on the ground and a digital facet camera on board. This is used as an aid during the final phase of the landing and not intended for updating the coordinates of the aerial vehicle if landing is not desired.

Extra weight of a camera and gimbal used in some of these methods is an issue in many unmanned aerial vehicle applications where payload needs to be as light as possible for greater range and endurance. Some of these methods are also specialized for landing only which does not account for precise navigation and beacon function when landing is not desired.

Hence there is a need for a simpler combined navigation and precise landing system which does not require use of cameras and complex image processing software and has a working range and altitude greater than the present systems.

Summary The present invention is made in the light of the problems above and it is an object of the present invention to provide a laser system comprised of a laser ground beacon, a laser receiver on board the multicopter and methods for navigation and landing. Present invention combines the autonomous navigation and landing tasks in a single system that can also work without the GPS assistance. This may particularly be useful in locations where GPS access is denied or unreliable.

An unmanned multicopter flying towards this zone will first enter it and at some point in time will eventually exit it. Zone enter and zone exit points will be detected by the interception of the laser beam with the laser receiver on the multicopter. When the exit point is reached, multicopter will be rotated 180 degrees and navigate towards the enter point until it reaches to midpoint distance of the enter and exit points. At the midpoint, it will be rotated 90 degrees (clock wise or anti-clockwise) until it reaches another exit point. Using these 3 points, center and radius of the zone can be calculated geometrically and multicopter can navigate to the center of the zone. To navigate to the center of the zone, multicopter needs to be rotated 180 degrees and navigate for a radius distance.

Once the multicopter is at the center of the zone, its position coordinates (Latitude, longitude and altitude) will be updated. Latitude and longitude of the beacon is already known and the altitude can be precisely calculated using the conical zone angle and conical zone radius.

After its position coordinates are updated, multicopter may navigate to the next beacon location or proceed to land at the current beacon location using the landing method.

Brief Description of Drawings

FIG. 1 is a diagram showing a solid or scanned hollow conical zone, a ground based laser beacon and an unmanned multicopter approaching the zone.

FIG. 2 is a functional block and schematic diagram of the laser system. FIG.3 is a diagram showing the navigation method for centering the unmanned multicopter in the conical zone.

FIG.4 is a diagram showing the landing method.

Detailed Description of the Invention

Using ground optical beams for navigation and landing is governed by a trade-off between emitter power output and 3D volume coverage. Power of an optical beam cannot be increased beyond a certain level for practical and safety reasons.

Unlike other applications where the beam is a cone, this invention uses a thin hollow conical beam zone where the beam power is present only at the boundaries of the 3D zone. It acts as a geofence and does not require any beam intensity variation across the 3D volume coverage. Hollowness of the conical beam zone concentrates available emitter power only at the boundaries of the zone which effectively increases the working range and altitude of the navigation and landing system. A thin hollow conical beacon zone is defined by solid or scanned laser beam geometry. A solid beam geometry has a continuous beam shape without any temporal or spatial discontinuities in the conical zone. A scanned beam geometry has rotational discontinuities but generates a higher laser power density in the conical zone for a given laser output power.

It will be known to a person skilled in the art that when the beam is not solid, but scanned at a constant rate, angular scan rate needs to be higher than a minimum rate to prevent the misdetection of the laser beam between rotations of the beam. This minimum rate can be calculated by the values of the speed range of the multicopter, beam thickness and the receiver aperture diameter.

A laser emitter coupled to a beam shaping optics can be used to generate a solid or scanned hollow conical zone. Beam shaping optics can be realized by various means. One such example of a beam shaping optics is a cone mirror. Other such beam shaping optics may be used consistent with the spirit of the invention, including but not limited to, using a rotating wedge (risley) prism, or a XY Galvanometer, or an axicon lens/mirror, or a rotating mirror or by rotating the laser emitter itself.

In an embodiment of the invention, laser beam may be modulated by a high frequency pulse to minimize adverse effects of direct and indirect radiation from other light sources on the receiver. Yet in another embodiment of the invention, laser beam may be encoded with the location coordinates or an identification number of the laser system which are stored in the laser beacon memory.

FIG.l schematically illustrates a solid or scanned hollow conical zone (1) of radius r, altitude a, cone half angle of Θ, and thickness t. Hollow conical zone is generated by the ground based laser beacon (2). An unmanned multicopter (3) with an onboard laser receiver (4) approaches the zone using its INS with or without GPS assistance.

FIG.2 schematically illustrates the ground based laser beacon (2) and the laser receiver (4) on board the multicopter (3). Laser beacon (2) is comprised of a laser module (7) which generates the solid or scanned hollow conical beam (1), a radio receiver (8) which can receive an activation/deactivation signal from the unmanned multicopter (3), a power supply module (9) and a controller module (10) which controls the overall operation of the laser beacon (2). Laser receiver (4) is comprised of a laser receiver module (5) for reception of laser pulses and a radio transmitter (6) which is used to transmit an activation/deactivation signal to the laser beacon (2).

Laser beacon (2) can be configured to run continuously as a dummy beacon but this consumes power when there is no multicopter (3) approaching the zone (1). To save power, laser module (7) is initially turned off. Radio transmitter (6) sends an activation signal while approaching but before entering the zone boundary. Controller module (10) then turns on the laser module (7) after reception of the activation signal by the radio receiver (8). To save power, controller module (10) can turn off the laser module (7) upon reception of a deactivation signal by the radio receiver (8) or after a certain set time has elapsed.

FIG.3 schematically illustrates the navigation method. Following the activation of the laser beacon (2), multicopter (3) enters the hollow conical zone (1) at point A where the laser pulses are first detected by the laser receiver (4) and then proceeds to point B where the laser pulses are detected a second time. Multicopter (3) is then rotated 180 degrees and proceeds to point O which is midway between points A and B. OB line distance is calculated by dividing the distance travelled between points A and B by 2. At point O, multicopter (3) is rotated 90 degrees (clockwise or counter clockwise). Assuming a counter clockwise rotation, multicopter (3) proceeds to point C where the laser pulses are detected by the laser receiver (4).

At this point, sufficient information is gathered for calculating the radius of the zone (1) using the equations:

OA x OB = OC x OD , r = (OC+OD) / 2

The same equations also hold true for a clockwise rotation. Multicopter (3) is now rotated 180 degrees and proceeds to the center of the zone (1) by travelling a distance of r. Referring again to FIG.l, current altitude a can be calculated using the equation:

a = r / tan(0) At this stage, INS navigation coordinates can be updated with the coordinates of the center point of the zone (1). After the update is completed, multicopter (3) can navigate to another beacon location or descend and land at the current beacon (2) location. FIG.4 schematically illustrates the landing method. Landing method is basically a repetition of the navigation method at selected decreasing altitudes or when a laser pulse is detected by the laser receiver (4) at the boundaries of the zone (1) during descend. As long as the multicopter (3) is within the hollow cone zone (1), it is on the right track for landing. Whenever a laser pulse is detected by the laser receiver (4), multicopter (3) INS executes the said navigation method to navigate itself to the center of the zone (1), recalculates the altitude and continue with descend until the landing is completed. Descend speed of the multicopter (3) is gradually decreased directly proportional to decreasing altitude.

Claims

An aerial navigation and landing system comprising a ground based laser beacon;

wherein the laser beacon comprises a laser module, a controller module and a radio receiver;

wherein the said laser module has means for generating a solid or scanned hollow conical beam zone by using a laser emitter coupled to a beam shaping optics;

wherein the said laser module has means for modulating and coding a laser beam with geographical coordinates and an identification number of the laser beacon where the geographical coordinates and the identification number of the laser beacon are stored in the controller module ;

wherein the said radio receiver has means for receiving an activation /deactivation radio signal;

wherein the said controller module turns on the laser module upon receiving of the activation signal by the radio receiver and turns off the laser module upon receiving of the deactivation signal by the radio receiver or after a certain set time has elapsed.

An aerial navigation and landing system according to claim 1, further comprising a laser receiver;

wherein the laser receiver is placed on a multicopter and comprises a laser receiver module which has means for receiving the laser pulses emitted by the laser beacon and a radio transmitter for transmitting an activation /deactivation signal to the said radio receiver.

An aerial navigation and landing system according to claim 1, further comprising a navigation method which interacts with the multicopter INS (Inertial Navigation System), laser beacon and the laser receiver ;

wherein the navigation method comprises the steps:

navigating the multicopter in the direction of the laser beacon at a current altitude named a ;

transmitting an activation signal from the radio transmitter before entering the hollow conical zone;

turning on the laser module using the beacon controller module after receiving the activation signal by the radio receiver ;

receiving laser pulses by the laser receiver upon entering the hollow conical zone at an entry point named A;

navigating the multicopter in a straight line until receiving laser pulses by the laser receiver at a point named B on the exit boundary of the hollow conical zone;

thereafter calculating AB line length using the multicopter INS distance travelled data;

rotating multicopter 180 degrees and navigating the multicopter in a straight line to a point named O at half the AB line length distance;

rotating multicopter 90 degrees and navigating the multicopter in a straight line to a point named C where laser pulses are received by the laser receiver; calculating radius of the zone r using equations:

OA x OB = OC x OD , r = (OC+OD) / 2 where OA, OB, OC and OD are respective line lengths of associated point pairs and r is the radius of the zone;

calculating the current altitude a using equation:

a = r / tan(6)

where Θ is the cone half angle of the zone;

rotating the multicopter 180 degrees and navigating to center of the hollow cone zone in a straight line using the said radius information r;

updating INS navigation coordinates with coordinates of center point of the zone.

An aerial navigation and landing system according to claim 1 further comprising a landing method which interacts with the multicopter INS, laser beacon and the laser receiver ;

wherein landing method comprises the steps:

descending the multicopter until a laser pulse is detected by the laser receiver or a certain set altitude is reached: recentering the multicopter using the navigation method; repeating said descending and recentering steps until the multicopter has landed;

transmitting a deactivation signal from the radio transmitter; turning off the laser module using the beacon controller module after receiving the deactivation signal by the radio receiver.