Flight guidance method of high altitude unmanned aerial vehicle for station keeping

Abstract

Disclosed is an automatic climbing and gliding method of a high altitude unmanned aerial vehicle (UAV). The disclosed method includes setting a cylindrical virtual flight region so that the high altitude UAV climbs and glides, setting a first target point on an end of a first flight radius which is vertically arranged to form the virtual flight region, setting second to Nth target points at arbitrary second to Nth flight radii sequentially arranged above or below the first flight radius, having the target points have a predetermined plane slope angle, and allowing the UAV to climb along a straight path line sequentially connecting each of the target points.

Claims

1. A flight guidance method of a high altitude unmanned aerial vehicle (UAV) for station keeping, the method comprising: setting a cylindrical virtual flight region so that the high altitude UAV climbs and glides; setting a first target at an arbitrary first flight radius from a plurality of flight radii vertically arranged to form the virtual flight region; setting second to N.sup.th target points at second to N.sup.th flight radii sequentially arranged above or below the first flight radius; and allowing the UAV to climb along straight path lines sequentially connecting each of the target points; wherein, when the UAV climbs and a flight direction of the UAV is turned to a direction facing a wind by a lateral direction wind, the target point is modified in the turned flight direction.

2. The method of claim 1; wherein the path lines have a predetermined plane slope angle therebetween.

3. The method of claim 2, wherein the plane slope angle is 090.

4. The method of claim 1, wherein a connecting shape of the path lines is a line, a polygon or a star shape as seen in a plane view.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 is a flight trajectory diagram of climbing and gliding of a high altitude unmanned aerial vehicle (UAV) according to the present invention.

(2) FIG. 2 is a diagram illustrating a flight direction when a high altitude UAV according to the present invention is positioned inside and outside a flight radius.

(3) FIG. 3A is a perspective diagram illustrating a first type diagram of a straight flight of a high altitude UAV according to the present invention.

(4) FIG. 3B is a plan diagram of FIG. 3A.

(5) FIG. 4 is a second type diagram of a straight flight of a high altitude UAV according to the present invention.

(6) FIG. 5 is a third type diagram of a straight flight of a high altitude UAV according to the present invention.

(7) FIGS. 6A, 6B, 6C and 6D are diagrams illustrating various types of flight paths when a flight radius is viewed from the top.

(8) FIGS. 7A, 7B and 7C are path correction diagrams when a high altitude UAV according to the present invention is affected by wind.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

(9) The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms a, an, and the, are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprises and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

(10) Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

(11) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(12) FIG. 1 is a flight trajectory diagram of climbing and gliding of a high altitude unmanned aerial vehicle (hereinafter, abbreviated as UAV) according to the present invention.

(13) Referring to FIG. 1, a flight region (a flight radius) of a high altitude UAV 10 according to the present invention is defined as a center and a radius, and the region is in a circular shape.

(14) The UAV 10 gradually climbs and glides or cruise while flying straight along a predetermined numbers of target points in the flight region. Likewise, when the UAV 10 flies straight in the flight region, a climbing speed and gliding speed are increased compared to a conventional turning flight, and thereby fatigue of a control surface may be decreased and energy consumption may be decreased.

(15) Further, when the UAV 10 flies straight in the flight region, even in the case of being pushed by a strong wind, such as a jet stream, because the UAV 10 has a target point, the UAV 10 may climb or glide while heading to the target point without drifting. As described in the above method, when the UAV 10 passes through the jet stream and the intensity of the wind decreases, the UAV 10 may reach the target point again.

(16) FIG. 2 is a diagram illustrating a flight direction when a high altitude UAV according to the present invention is positioned inside and outside a flight radius.

(17) Referring to FIG. 2, in a state in which an operational mode of the UAV 10 is set and the UAV 10 is positioned inside the flight radius, the UAV 10 flies toward a target point on the end center of the flight radius while maintaining a current flight direction, and when the UAV 10 is positioned outside the flight radius, the UAV 10 is led toward a center O of the flight radius, and as a result is positioned inside the flight radius.

(18) As described above, even when the UAV 10 is positioned inside or outside the flight radius, because the UAV 10 is set to induce flying straight toward the target point on the end of flight radius or the center O thereof, the flight path may be shortened compared to a conventional turning flight.

(19) FIGS. 3A, 3B, 4 and 5 illustrate types of straight flights of a high altitude UAV according to the present invention inside a flight radius.

(20) First, FIG. 3A is a perspective diagram illustrating a first type diagram of a straight flight of a high altitude UAV according to the present invention, and FIG. 3B is a plan diagram of FIG. 3A.

(21) As illustrated in FIG. 3A, in the present invention, a first target point P.sub.1 is set on the end of a virtual first flight radius C.sub.1 and second to N target points P.sub.22 to P.sub.n are designed cross point (intended turning back angle line with flight radii) on the ends of second to N flight radii C.sub.22 to C.sub.n which are sequentially disposed above or below the first flight radius C.sub.1 and are then vertically arranged to form a cylindrical flight region, and target points have a certain planar reflection angle between sequential target points, thereby allowing the UAV 10 to climb or glide according to a straight flight path sequentially connecting the target points.

(22) Referring to FIG. 3B, when the UAV 10 continuously flies straight within the first flight radius C.sub.1 and reaches an opposite point of the end of the second flight radius C.sub.2, the UAV 10 is turned in a direction that is a reflected direction which is perpendicular to or an acute angle with a tangent line at the reached point, and flies straight. When the UAV 10 reaches the end of another flight radius again, the UAV 10 is turned in the same manner as described above. Therefore, the UAV 10 remains within the flight radius and flies straight in the form of zigzag.

(23) Here, an angle between a virtual incident line L.sub.1 heading to the first target point P.sub.1 of the target points and a reflected line L.sub.2 heading from the first target point P.sub.1 to the second target point P.sub.2 being 090 is preferable.

(24) When the angle between the incident line L.sub.1 and the reflected line L.sub.2 is greater than 90, because the flight trajectory of the UAV 10 is close to a circle, fatigue may be accumulated on a control surface and an actuator as in the above described conventional problem, and a problem in that energy consumption is increased occurs. Therefore, a reflected angle should preferably be limited so that the sum of an incident angle and a reflected angle is smaller than 90.

(25) FIG. 4 illustrates a method of modifying a path to be perpendicular (at a right angles) to a tangent line when the UAV 10 reaches a tangent section of the circumference of the flight radius which is a planar flight region. In this case, the UAV 10 reciprocates along a diameter line inside the flight radius.

(26) FIG. 5 illustrates a method of modifying a path by adding a predetermined acute angle (.sub.0<<90) to an angle (.sub.90) perpendicular with the tangent line when the UAV 10 reaches the tangent section of the end of the flight radius.

(27) FIGS. 6A, 6B, 6C and 6D illustrate various types of flight paths when a flight radius is viewed from the top.

(28) FIG. 6A is a case in which the UAV 10 flies back and forth to alternate two target points when the two target points are designated. FIG. 6B is a case in which the UAV 10 flies across the trajectory thereof in the form of a star shape when five target points are designated. FIGS. 6C and 6D is a case in which the UAV 10 flies along a line trajectory connecting target points when four or more target points are designated.

(29) These cases implement various types of flight cases according to the number of target points and changes in positions of the target points.

(30) As the method described above is a basic operation mode which does not consider a variable of wind, when the intensity of wind increases, it is necessary to modify the path with respect to the wind by modifying the path to the nose of the UAV 10. A detailed description regarding this will be as follows. FIGS. 7A, 7B and 7C are schematic diagrams illustrating a method for modification of a path with respect to wind.

(31) As illustrated in FIG. 7A, when the intensity of wind increases, the UAV 10 veers away from an existing path W.sub.0 and a nose of the UAV 10 is naturally turned in a direction of the wind due to an effect of a vertical stabilizer.

(32) When the wind is greater than a predetermined speed (for example, 50% or more of a cruise velocity), a path angle error is greater than a predetermined angle (for example, an azimuth error angle of 45 or more), or a path error distance is greater than a predetermined distance (for example, 10 times a wing width), the target point P.sub.1 is changed to a current direction W.sub.1 of the nose of the UAV 10.

(33) When the UAV 10 reaches a changed target point P.sub.1, a target point P.sub.2 which is 180 behind the UAV 10 is reset unlike a case in which the wind is weak. Likewise, when the wind is strong, the UAV 10 flies alternately to target points P.sub.1, P.sub.2, and P.sub.3 as illustrated in FIGS. 7A, 7B and 7C.

(34) Meanwhile, although it is not illustrated in the drawings, a buffer region is additionally set outside the flight region. The buffer region is a region which is set to prevent the UAV 10 from mistakenly sensing that it has left the flight region even when it is positioned at the boundary area of the flight region.

(35) The present invention has been described in detail with reference to the exemplary embodiments. However, the exemplary embodiments should be considered in a descriptive sense only, and the invention is not limited thereto. It should be apparent to those skilled in the art that various modifications and improvements within the scope of the invention may be made.

(36) Simple modifications and alterations of the present invention fall within the scope of the present invention and the scope of the present invention is defined by the accompanying claims.