Unpowered accurate landing autonomous navigation method for fixed-wing unmanned aerial vehicle

Abstract

The present invention relates to an unpowered accurate landing autonomous navigation method for a fixed-wing unmanned aerial vehicle. The method comprises: during an aerial flight process, after an engine is shut down, a fixed-wing unmanned aerial vehicle flying, in a glide manner, to an aerial position above an extension line of a runway of a present airport; performing a hover descent flight according to a hover diameter R; when descending to a glide ratio decision height H-j, obtaining a radius variation decision height of hover descent of a final lap of the unmanned aerial vehicle and the radius of the final lap on the basis of a real height variation of a complete lap, the distance L between a landing point and a heading interception point of the runway, and a tail-end downward sliding height at the heading interception point; the unmanned aerial vehicle performing hover descent of the final lap on the basis of the radius of the final lap, entering the heading interception point, and tracking a tail-end downward sliding route; finally, realizing accurate landing on the basis of a rated downward sliding speed and a safe landing attitude. The present invention is a more accurate autonomous navigation landing method, and involves a relatively broad industrial application prospect.

Description

An autonomous navigation method for unpowered precision landing of fixed-wing UAV Technical Field

[0001] The present invention belongs to the technical field of unpowered recovery of unmanned aerial vehicles (UAVs), and relates to an autonomous navigation method for unpowered precise landing of a fixed-wing UAV. Background Art

[0002] Currently, for autonomous navigation methods for taxiing takeoff and landing fixed-wing UAVs performing unpowered emergency landings after engine shutdown, some drones use the concept of a circular landing zone, requiring a wide landing area and scattered landing points, which is not conducive to precise landings. Other drones use a high-angle descent to track the route from the engine shutdown point, which results in a long route. This makes the planned route susceptible to external interference such as wind shear during long-term, high-angle tracking, increasing flight safety risks. Alternatively, during the return to the airport runway, they use speed reduction and altitude reduction methods such as "figure-eight" turns, resulting in excessive maneuvers that are detrimental to flight safety. Therefore, how can a taxiing takeoff and landing fixed-wing UAV maintain a low speed, a landing attitude that meets flight quality requirements, and a precise landing point after gliding to land without power? This paper proposes an autonomous navigation method for unpowered, precise landings of taxiing takeoff and landing fixed-wing UAVs.

[0003] Summary of the Invention

[0004] Technical problems to be solved

[0005] In order to avoid the shortcomings of the existing technology, the present invention proposes an autonomous navigation method for the unpowered precise landing of a fixed-wing UAV, which can achieve a safer and precise landing on the local runway when the fixed-wing UAV engine stops abnormally.

[0006] Technical Solution

[0007] A method for unpowered precision landing of a fixed-wing UAV is provided, characterized by the following steps:

[0008] Step 1: During the flight of a fixed-wing UAV, after the engine is shut down during takeoff and landing, the UAV glides from the engine stop point to the top of the runway extension line at the rated safety speed while maintaining a fixed descent angle.

[0009] Step 2: Above the runway extension line, perform a circling flight with a radius of R and a decreasing altitude. The process is as follows:

[0010] During the circling and descending flight, the aircraft flies according to the rated safety speed and a fixed descent angle in step 1, and the circling radius R is maintained, where the roll angle of the UAV satisfies the maximum roll angle constraint φ≤φ. max ;

[0011] Step 3: When descending to the glide ratio decision altitude H-j When , record the height change ΔH for a complete circle:

[0012] Calculate the change in radius of the last circle of the drone's circling and descending, and the decision height is H -max : H -max =H -xh +2*ΔH

[0013] Where: Terminal glide height H at the heading entry point -xh equal:

[0014] Where: K is the glide ratio of the UAV before landing, L is the horizontal distance between the runway landing point and the heading entry point;

[0015] Step 4: When the UAV passes the heading entry point height H and is lower than the radius change decision height H -max , the radius R' of the last circle is calculated online in real time:

[0016] The drone performs a final circle and descends in altitude according to the changed radius R';

[0017] Step 5: The drone performs a final circle and descends to H according to the changed radius R'. -xh Autonomous navigation enters the heading entry point and tracks the terminal glide path;

[0018] Finally, a precise landing is achieved according to the rated descent speed and safe landing posture.

[0019] The height change of a complete circle ΔH=H up -H down , where: H up 、H down The altitude at which the UAV circles and descends for the first time and passes the heading entry point S on the runway extension line at the decision altitude, and the altitude at which the UAV circles and descends for the second time and passes the heading entry point on the runway extension line.

[0020] The height H up 、H down The change is directly obtained by the height sensor.

[0021] The glide ratio is based on the ratio between the circumference of the drone's circle and the amount of altitude reduction during the circle. Calculate the glide ratio K of the drone before landing.

[0022] The roll angle Among them, V s is the tangential component of the rated safety speed. Beneficial effects

[0023] The present invention proposes an autonomous navigation method for precise landing of a fixed-wing UAV without power. When the fixed-wing UAV is in flight, after the engine is shut down, it glides to the top of the runway extension line. It then performs a circling and descending flight according to the circling radius R. When the gliding ratio decision height H is reached, the fixed-wing UAV is -j During descent, the actual altitude change over a complete circle, the distance L between the runway touchdown point and the course cut-off point, and the final glide height at the course cut-off point are used to determine the decision altitude for the final radius change and the final radius. The drone then descends according to the final radius, enters the course cut-off point, and tracks the final glide path. Ultimately, a precise landing is achieved at the rated glide speed and in a safe landing attitude.

[0024] Specific beneficial effects:

[0025] 1. For emergency scenarios involving a UAV engine shutdown and unpowered descent, a precise autonomous navigation control method for returning to the home runway has been developed, eliminating the concept of a circular landing zone and preventing multiple forced landings. From the parking point to the extended runway back to the home runway, there is no tracking route during the glide, eliminating the steep angles associated with long routes and potential susceptibility to high-altitude wind shear. Furthermore, when tracking the runway route at the end of the heading intercept, there is no need for large maneuvers such as a figure-eight turn, eliminating situations where the speed and altitude at the intercept point are inappropriate, thus enhancing flight safety.

[0026] 2. When calculating the glide ratio of the drone during a flight, factors such as the wind speed and ambient weather before landing are taken into account. It is not affected by wind interference, ensuring that the glide mode is observable and controllable, and achieving precise landing.

[0027] 3. During the descent and circling process, the radius transformation program performs online real-time calculations, eliminating the influence of uncontrollable factors such as different psychological qualities or operating skills of different pilots, and realizing autonomous navigation control.

[0028] 4. When this method enters the terminal guidance line tracking, the height and speed control accuracy is high, which ensures the accuracy of the final landing point and the safety of touching the ground in advance.

[0029] 5. For the emergency scenario of a single-engine fixed-wing UAV with engine failure and unpowered gliding, a feasible autonomous navigation and landing method is proposed. This method has broad industry application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1: Side view of autonomous navigation for precise landing

[0031] Figure 2: Schematic diagram of precise landing autonomous navigation from above

[0032] Figure 3: Flowchart of the method of the present invention DETAILED DESCRIPTION

[0033] The present invention will now be further described with reference to the embodiments and accompanying drawings:

[0034] The process is shown in Figure 3. The specific implementation includes the following steps:

[0035] Step 1: After the engine of the fixed-wing UAV is shut down during flight, the horizontal tail elevator surface is controlled according to the rated safety speed. From the engine shutdown point, a fixed descent angle is maintained and the UAV glides to the top of the runway extension line.

[0036] Specifically, a fixed-wing UAV stopped its engine during flight at an altitude of 3,000 meters. It glided from the engine stop point at a rated safety speed of 130 km / h, maintaining a fixed glide angle of -3 degrees, to the runway extension line.

[0037] Step 2: As shown in Figures 1 and 2, the drone flies in a circle with a given radius R over the runway extension line. During this process, it still maintains a fixed descent angle based on the rated safety speed. When flying within the tracking radius R, the drone's roll angle satisfies the maximum roll angle constraint φ≤φ max .

[0038] The roll angle satisfies the following formula:

[0039] Among them, V s is the tangential component of the rated safety speed.

[0040] Specifically: above the runway extension line, perform a circling flight with a radius of R = 500m and a decreasing altitude. The process is as follows:

[0041] During the circling and descending flight, the aircraft shall fly at a rated safety speed of 130 km / h and a fixed glide angle of -3 degrees according to step 1, with a circling radius of R = 500 m, and the UAV roll angle shall meet the maximum roll angle constraint of φ ≤ 30°;

[0042] Step 3: The drone is circling and descending according to step 2. When the drone's flight altitude drops to the glide ratio decision height H -j When descending, record the actual height reduction ΔH for a complete circle. ΔH=H up -H down

[0043] Among them, H up 、H downThis is the altitude at which the drone flies past the runway extension line's heading entry point S after its first and second turns, after the drone's flight altitude meets the glide ratio decision altitude. This altitude change is directly acquired by the altitude sensor, and the wind conditions before the glide landing are taken into account when acquiring the data.

[0044] If the UAV's flight altitude does not meet the glide ratio decision altitude, the UAV will circle and descend according to the tracking radius R in step 2 until the conditions are met, and then proceed to step 3.

[0045] Specifically: when descending to the glide ratio decision altitude H -j =1000m, record the altitude change of one complete circle ΔH = 210m:

[0046] Calculate the change in radius of the last circle of the drone's circling and descending, and the decision height is H -max : H -max =H -xh +2*ΔH=80+2×210=500m

[0047] Where: Terminal glide height H at the heading entry point -xh equal:

[0048] in: is the glide ratio of the UAV before landing, L = 1200m is the horizontal distance between the runway landing point and the heading entry point;

[0049] Step 4: Calculate the glide ratio K of the drone before landing based on the ratio of the height reduction of the drone during one circle and the circumference of one circle. Based on the glide ratio, determine the distance L between the runway landing point and the heading entry point and the terminal glide height H at the heading entry point. -xh , satisfying H -xh =K*L;

[0050] Specifically: When the UAV passes the heading entry point height H = 420m and is lower than the radius change decision height H -max =500m, the radius R' of the last circle is calculated online in real time:

[0051] The drone performs a final circle and descends in altitude according to the changed radius R' = 810m;

[0052] Step 5: Obtain the actual circling height reduction ΔH and terminal descent height H according to steps 3 and 4 -xh Calculate the decision height of the last circle radius change of the drone as H -max , satisfying H -max =H -xh +2*ΔH;

[0053] When the altitude H of the UAV passing the heading entry point is lower than the radius change decision altitude H calculated in step 5 -max When the radius R' of the last circle is calculated online in real time, it satisfies

[0054] The drone performs a final circle and descends according to the changed radius R'.

[0055] If the UAV's flight altitude does not meet the radius change decision altitude, the UAV will circle and descend according to the tracking radius R in step 2; until the conditions are met, proceed to step 6.

[0056] After accurately calculating the drone's final descent trajectory in real time online according to step six, the drone accurately descends to the final descent altitude and autonomously enters the heading entry point to track the final descent path. Finally, it achieves a precise landing at the rated descent speed and in a safe landing attitude.

[0057] Specifically: the UAV performs the final circle and descends to the height of H according to the changed radius R'=810m. -xh =80m autonomous navigation into the heading entry point and tracking the terminal glide path;

[0058] Finally, a precise landing is achieved according to the rated descent speed and safe landing posture.

[0059] This invention proposes a precise autonomous navigation method for returning to the home runway in the event of a UAV engine shutdown and power failure, eliminating the concept of a circular landing zone and the need for multiple forced landings. From the parking point to the extended runway back to the home runway, no flight path is tracked during the glide process, eliminating the steep angles associated with long flight paths and potential susceptibility to high-altitude wind shear. Furthermore, when entering the terminal runway tracking route, no drastic maneuvers such as a figure-eight turn are required, eliminating situations where the speed and altitude at the entry point are inappropriate, thus enhancing flight safety. The glide ratio calculation for the UAV during the flight considers factors such as the wind speed and ambient weather before landing, ensuring an observable and controllable glide mode and a precise landing without being affected by wind interference. During the descent and circling process, a radius change program is calculated online in real time, eliminating the influence of uncontrollable factors such as pilot psychological qualities and operational skills, thus achieving autonomous navigation control. This method achieves high-precision altitude and speed control during terminal guidance line tracking, ensuring the accuracy of the final landing point and a safe touchdown.

[0060] This invention proposes a more accurate autonomous navigation landing method for unpowered gliding landing scenarios in which the engine of a fixed-wing UAV undergoes an abnormal mid-air engine shutdown during taxiing takeoff and landing. This method has broad industry application prospects.

Claims

1. A method for autonomous navigation of a fixed-wing UAV for precision landing without power, characterized in that Here are the steps: Step 1: During the flight of the fixed-wing UAV, after the engine stops during the taxiing takeoff and landing, the UAV glides from the engine stop point to the air above the runway extension line at the rated safety speed while maintaining a fixed descent angle; Step 2: Above the runway extension line, perform a circling flight with a radius of R and a decreasing altitude. The process is as follows: During the hovering and descending flight, the rated safety speed in step 1 and the fixed gliding angle are maintained, and the flight is carried out according to the hovering radius R, where the roll angle of the UAV satisfies the maximum roll angle constraint φ≤φ max ; Step 3: When descending to the glide ratio decision altitude H -j When , record the height change ΔH for a complete circle: Calculate the change in radius of the last circle of the drone's circling and descending, and the decision height is H -max : H -max =H -xh +2*ΔH Where: The terminal glide height H at the heading entry point -xh equal: Where: K is the glide ratio of the drone before landing, L is the horizontal distance between the runway landing point and the heading entry point; Step 4: When the drone passes the heading entry point height H and is lower than the radius change decision height H -max , the radius R' of the last circle is calculated online in real time: The drone performs the final circle and descends according to the changed radius R'; Step 5: The drone performs a final circle of circling according to the changed radius R', descending to H -xh Autonomous navigation enters the heading entry point and tracks the terminal glide path; Finally, a precise landing is achieved according to the rated descent speed and safe landing posture.

2. The method for unpowered precise landing of a fixed-wing UAV according to claim 1 is characterized by: The height change of a complete circle ΔH=H up -H down , where: H up , H down The decision altitude is the altitude when the UAV hovers and descends for the first time and passes the heading entry point S on the runway extension line, and the altitude when the UAV hovers and descends for the second time and passes the heading entry point on the runway extension line.

3. The method for unpowered precise landing of a fixed-wing UAV according to claim 2 is characterized in that: The height H up , H down The change is directly obtained by the height sensor.

4. The method for unpowered precise landing of a fixed-wing UAV according to claim 1 is characterized in that: The glide ratio is based on the ratio between the circumference of a circle of the UAV and the height reduction of the circle. Calculate the glide ratio K of the drone before landing.

5. The method for unpowered precise landing of a fixed-wing UAV according to claim 1 is characterized by: The roll angle Among them, V s is the tangential component of the rated safety speed.

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