WO2025020576A1 - Unpowered accurate landing autonomous navigation method for fixed-wing unmanned aerial vehicle - Google Patents

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

A method for autonomous navigation of fixed-wing UAV's precision landing without power Technical Field

The invention belongs to the technical field of unmanned aerial vehicle (UAV) unpowered recovery, and relates to an autonomous navigation method for unpowered precise landing of a fixed-wing UAV.

Background Art

At present, for the autonomous navigation method of emergency landing without power after the engine of the taxiing takeoff and landing fixed-wing UAV stops, some UAVs adopt the concept of circular landing area, which requires a wide landing range to be planned, and the landing points are relatively scattered, which is not conducive to precise landing; another part of the UAV adopts the method of tracking the route at a large angle from the engine stop point, and the planned route is long. During the long-term large-angle tracking of the route, it is susceptible to external interference such as wind shear, which increases the risk of flight safety; or in the process of returning to the airport runway, the "8" plate and other speed reduction and altitude reduction methods are used, and too many maneuvers are made, which is not conducive to flight safety. Therefore, how to ensure that the taxiing takeoff and landing fixed-wing UAV can maintain a low speed, a landing posture that meets the flight quality, and a precise landing point after gliding and landing without power, and propose a method of autonomous navigation for precise landing without power for taxiing takeoff and landing fixed-wing UAV.

Summary of the invention

Technical issues to be solved

In order to avoid the shortcomings of the prior art, the present invention proposes an autonomous navigation method for precision landing of a fixed-wing UAV without power, which can enable the fixed-wing UAV to land precisely on the runway more safely when the engine of the fixed-wing UAV stops abnormally.

Technical Solution

A method for autonomous navigation of a fixed-wing UAV for unpowered precise landing, characterized by the following steps:

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 extended runway 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 drone flies at a hovering radius R based on the rated safety speed and a fixed gliding angle in step 1, and the drone's roll angle satisfies the maximum roll angle constraint φ≤φ _max ;

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

Calculate the decision height of the last circle radius change of the drone as H _-max :
H _-max =H _-xh +2*ΔH

Where: The terminal glide height H _-xh at the heading entry point is equal to:

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 altitude H of the UAV’s heading entry point is lower than the radius change decision altitude H _-max , the radius R' of the last circle is calculated online and in real time:

The drone performs the final circle and descends according to the changed radius R';

Step 5: The drone performs the last circle and descends to the altitude of H _-xh according to the changed radius R', and autonomously navigates to 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.

The altitude change of a complete circle ΔH=H _up -H _down , wherein: H _up and H _down are the altitudes when the UAV hovers and descends over the heading entry point S on the runway extension line for the first time and the UAV hovers and descends over the heading entry point on the runway extension line for the second time at the decision altitude.

The changes in heights H _up and H _down are directly obtained by a height sensor.

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.

The roll angle Where _Vs is the tangential component of the rated safety speed.

Beneficial Effects

The present invention proposes an autonomous navigation method for precision landing of a fixed-wing UAV without power. When the engine of the fixed-wing UAV is stopped during aerial flight, the UAV glides to the sky above the extension line of the runway of the local field; the UAV performs circling and descending flight according to the circling radius R. When the gliding ratio is lowered to below the decision height H _-j , the decision height of the last circle radius change of the UAV circling and descending, and the radius of the last circle are obtained according to the actual height change of a complete circle, the distance L between the runway landing point and the heading entry point, and the terminal gliding height at the heading entry point. The UAV performs the last circle of circling and descending according to the last circle radius, enters the heading entry point, and tracks the terminal gliding route. Finally, a precise landing is achieved according to the rated gliding speed and safe landing posture.

Specific beneficial effects:

1. For the emergency scenario of the drone engine stopping and the drone gliding without power, a precise autonomous navigation control method for returning to the airport is proposed, which eliminates the concept of a circular landing area and will not cause multiple forced landings. From the parking point to the extended runway line of the return airport, there is no tracking route during the gliding process, which eliminates the large angle caused by the long route and is susceptible to the influence of high-altitude wind shear. At the same time, when tracking the runway route at the end of the heading cut-in, there is no need to perform large maneuvers such as the "8" turn to eliminate the situation where the speed and height of the cut-in point are inappropriate, thereby enhancing flight safety.

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

3. During the descent and hovering process, the radius transformation program is calculated online in real time, eliminating the influence of uncontrollable factors such as different psychological qualities or operating skills of different pilots, and realizing autonomous navigation control.

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.

5. For the emergency scenario of single-engine fixed-wing UAV engine shutdown and unpowered gliding, a more feasible autonomous navigation and landing method is proposed. It has a broad industry application prospect.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: Side view of autonomous navigation for precision landing

Figure 2: Schematic diagram of precise landing autonomous navigation from top view

Figure 3: Flow chart of the method of the present invention

DETAILED DESCRIPTION

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

The process is shown in Figure 3, and the specific implementation includes the following steps:

Step 1: After the engine of the fixed-wing UAV stops during flight, the horizontal tail elevator surface is controlled according to the rated safety speed. From the engine stop point, the fixed descent angle is maintained and the UAV glides to the air above the runway extension line of the airport;

Specifically: a fixed-wing UAV stops its engine during flight. The current stop altitude is 3000m. It glides from the engine stop point to the runway extension line at a rated safety speed of 130km/h, maintaining a fixed glide angle of -3 degrees.

Step 2: As shown in Figures 1 and 2, the drone flies in a spiral with a given radius R above the runway extension line. During this process, the drone still maintains a fixed glide 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 .

The roll angle satisfies the following formula:

Where _Vs is the tangential component of the rated safety speed.

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

During the hovering and descending flight, according to the rated safety speed of 130km/h and the fixed glide angle of -3 degrees in step 1, the flight is carried out according to the hovering radius R = 500m, and the roll angle of the UAV meets the maximum roll angle constraint φ≤30°;

Step 3: When the drone descends in the process of circling according to step 2, when the flight altitude of the drone drops below the glide ratio decision altitude H _-j , record the actual circling altitude decrease ΔH for a complete circle.
ΔH＝H _up -H _down

Among them, H _up and H _down are the heights when the UAV hovers and descends for the first time and the second time after the UAV flight altitude meets the glide ratio decision altitude, passing the heading entry point S on the runway extension line. The height change is directly obtained by the altitude sensor, and the wind field conditions before the glide landing have been considered when acquiring the data.

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.

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

Calculate the decision height of the last circle radius change of the drone as H _-max :
H _-max =H _-xh +2*ΔH＝80+2×210＝500m

Where: The terminal glide height H _-xh at the heading entry point is equal to:

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;

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

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:

The UAV performs the final circle and descends according to the changed radius R' = 810m;

Step 5: According to Step 3 and Step 4, the actual hovering height reduction ΔH and the terminal gliding height H _-xh are obtained, and then the calculation is made. The decision height of the last radius change of the drone's rotation and descent is H _-max , which satisfies H _-max = H _-xh +2*ΔH;

When the altitude H of the UAV’s heading entry point is lower than the radius change decision altitude H _-max calculated in step 5, the radius R' of the last circle is calculated online in real time to meet

The UAV performs the final circle and descends according to the changed radius R'.

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

After accurately calculating the last circle trajectory of the drone in real time online according to step 6, the drone accurately descends to the terminal descent height and autonomously enters the heading entry point to track the terminal descent route. Finally, it achieves precise landing at the rated descent speed and safe landing posture.

Specifically, the UAV performs the last circle and descends to the altitude of H _-xh = 80m according to the changed radius R' = 810m, and then autonomously navigates to 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.

The present invention proposes a precise autonomous navigation method for returning to the field for the emergency scenario of the UAV engine stopping and returning to the field without power, eliminating the concept of a circular landing area and causing multiple forced landings. From the parking point to the extended runway line of the return field, there is no tracking route during the gliding process, eliminating the large angle caused by the long route, which is susceptible to the influence of high-altitude wind shear, etc. At the same time, when the heading cuts into the end of the runway route, there is no need to perform large maneuvers such as the "8" plate to eliminate the situation where the speed and height of the cut-in point are not suitable, thereby enhancing flight safety. When calculating the glide ratio of the UAV during the current flight, factors such as the wind speed and environmental weather before landing are considered, and it is not affected by wind interference, ensuring that the gliding mode is observable and controllable, and achieving precise landing. During the gliding and hovering process, the radius change program is calculated online in real time, eliminating the influence of different pilots on uncontrollable factors such as different psychological qualities or operating skills, and realizing autonomous navigation control. When the method enters the terminal navigation line tracking, the height and speed control accuracy is high, which guarantees the accuracy of the final landing point and the safety of touching the ground in advance.

The present invention provides a method for the scenario in which the engine of a fixed-wing UAV stops abnormally in the air and glides without power for landing during taxiing takeoff and landing. A more accurate autonomous navigation and landing method has been developed, which has a broad prospect for industry application.

Claims (5)

A method for autonomous navigation of a fixed-wing UAV for unpowered precise landing, characterized by the following 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 drone flies at a hovering radius R based on the rated safety speed and a fixed gliding angle in step 1, and the drone's roll angle satisfies the maximum roll angle constraint φ≤φ _max ; Step 3: When descending to the glide ratio decision altitude H _-j , record the altitude change ΔH for a complete circle: Calculate the decision height of the last circle radius change of the drone as H _-max :
H _-max =H _-xh +2*ΔH Where: The terminal glide height H _-xh at the heading entry point is equal to:
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 altitude H of the UAV’s heading entry point is lower than the radius change decision altitude H _-max , the radius R' of the last circle is calculated online and in real time:
The drone performs the final circle and descends according to the changed radius R'; Step 5: The drone performs the last circle and descends to the altitude of H _-xh according to the changed radius R', and autonomously navigates to 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. According to claim 1, the fixed-wing UAV unpowered precision landing autonomous navigation method is characterized in that: the altitude change of a complete circle ΔH=H _up -H _down , wherein: H _up and H _down are the altitudes of the first time the UAV hovers and descends to pass the heading entry point S on the runway extension line and the second time the UAV hovers and descends to pass the heading entry point on the runway extension line at the decision altitude. According to the fixed-wing UAV unpowered precision landing autonomous navigation method of claim 2, it is characterized in that the changes in the heights H _up and H _down are directly obtained by a height sensor. According to claim 1, the fixed-wing UAV unpowered precision landing autonomous navigation method is characterized in that: the glide ratio is based on the relationship between the circumference of the UAV circling a circle and the circling height reduction Calculate the glide ratio K of the drone before landing. According to the fixed-wing UAV unpowered precision landing autonomous navigation method according to claim 1, it is characterized in that: the roll angle Where _Vs is the tangential component of the rated safety speed.