A method and system for calculating the height from the ground during the landing phase of an unmanned aerial vehicle

Abstract

The present invention relates to a method and system for calculating the height above the ground during the landing phase of an unmanned aerial vehicle (UAV). A calculation device for resolving the real-time height above the ground of the aircraft through satellite position information and runway position information is provided. When the UAV does not have a height measurement device above the ground, or when the height measurement device above the ground is available but fails, the real-time height above the ground of the UAV is resolved, and the UAV is controlled to approach and land through a flight control system, effectively improving the landing point accuracy and avoiding aircraft damage caused by height information errors. The present invention effectively improves the landing point accuracy of the UAV and avoids situations such as the UAV running out of the runway due to insufficient runway distance during the landing phase, the aircraft bouncing up due to too high a landing speed, damage to the landing gear, and even damage to the aircraft. At the same time, for UAVs equipped with height measurement sensors above the ground, the resolved height information above the ground is used as a redundancy, and when the height measurement sensor above the ground fails, the calculation of the height above the ground is switched to, improving the reliability and safety of the UAV.

Description

Technical Field

[0001] The present invention belongs to the technical field of UAV landing control, and relates to a method and system for calculating the height above the ground during the landing phase of a UAV. It is a calculation device that can accurately calculate the height above the ground in real time through on-board sensor information, and controls the calculated height above the ground to achieve a smooth landing of the UAV. Background Technique

[0002] The height above the ground of a UAV is one of the important control variables during the landing process of a skid-type UAV. Some UAVs are equipped with a radio altimeter to measure the true height of the aircraft above the ground in real time. However, many existing small and medium-sized UAVs do not have a radio altimeter for reasons such as cost reduction, weight reduction, and structural layout, and only roughly calculate the real-time height above the ground through data from an atmospheric pressure sensor or a satellite positioning system. In fact, due to factors such as terrain, drainage, and construction costs, airport construction usually has a certain slope, which leads to a deviation between the calculated height and the true height. Assuming a runway length of 2000 meters and a runway slope of 1% (within the allowable range), the height difference between the two ends of the runway is 20 meters; assuming that the glide angle of the aircraft during the landing phase is -3 degrees (generally taken as -3.5 degrees to -2.5 degrees), a height measurement error of 1 meter can cause a longitudinal distance control deviation of 19 meters, which is extremely unfavorable for the UAV to land with high touchdown accuracy and even affects flight safety and causes damage to the aircraft. At this time, there is an urgent need to invent a calculation device that can accurately calculate the height above the ground during the approach and landing phases of the aircraft. By using the data of the existing sensors of the aircraft without adding new sensors to calculate the real-time height above the ground, the aircraft can land smoothly without a height measurement device, effectively avoiding accidents caused by errors in the height above the ground data and improving the safety of the UAV. Summary of the Invention

[0003] Technical Problems to be Solved

[0004] In order to avoid the deficiencies of the prior art, the present invention proposes a method and system for calculating the height above the ground during the landing phase of a UAV, which solves the problem of low accuracy in calculating the height above the ground data of the UAV due to the lack of a height measurement device on the UAV and the slope of the airport runway, resulting in low touchdown accuracy and even safety problems.

[0005] Technical Solution

[0006] A method for calculating the height above the ground during the landing phase of a UAV, characterized by the following steps:

[0007] Step 1: The ground station pre-measures the longitude, latitude, and height of each characteristic point on the runway center line. P(1) is the position of the lower point among the two end points of the runway center line; P(n) is the position of the higher point among the two end points of the runway center line; P(i) is the position of any characteristic point selected on the runway center line;

[0008] Step 2: When the current position of the aircraft is P, determine the interval where the projection of the current position of the aircraft on the runway is located;

[0009] The determination method is as follows: Calculate the sum of the distances from the current position of the aircraft to both endpoints of each runway interval respectively. The runway interval with the shortest distance sum is the runway interval segment P(i)P(j) where the aircraft position is located;

[0010] Step 3: Calculate the height above the ground of the current position of the aircraft, which is calculated as follows: The projection of the aircraft on the runway is located on the segment P(i)P(j), and the moving direction of the aircraft is from P(i) to P(j). The altitude of the projection point of the current position of the aircraft:

[0011]

[0012] The height above the ground after the aircraft enters the runway:

[0013]

[0014] Wherein, is the altitude of the projection point of the current position of the aircraft; L is the distance of the aircraft entering the current runway interval; L ij is the distance between P(i) and P(j); H i is the altitude of point i; H j is the altitude of point j, and H is the current altitude of the aircraft.

[0015] The characteristic point i of the runway center line satisfies i ≤ n - 1.

[0016] A system for implementing the method for calculating the height above the ground during the landing phase of the unmanned aerial vehicle, characterized by including a satellite positioning system, a ground station, a flight control computer, an airborne sensor, and a height above the ground calculation module; the satellite positioning system, the height above the ground calculation module, the flight control computer, and the airborne sensor are installed on the unmanned aerial vehicle; the satellite positioning system measures the position information of the unmanned aerial vehicle and outputs the position information to the height above the ground calculation module; the ground station enters and uploads the position information of the aircraft on the runway to the height above the ground calculation module; after receiving the position information of the unmanned aerial vehicle and the position information of the aircraft on the runway, the height above the ground calculation module calculates the height above the ground of the aircraft in real time and outputs it to the flight control module of the flight control computer; the flight control module receives the height above the ground of the aircraft calculated in real time by the height above the ground calculation module, and calculates the control amounts of each control surface and the throttle, and drives the aircraft to approach and land according to the expected flight path; the position information includes longitude, latitude, and altitude.

[0017] If the aircraft is not equipped with a radio altimeter, the calculated height is used as the main signal of the height above the ground. If the aircraft is equipped with a radio altimeter, the calculated height is used as the backup signal of the height above the ground and is used when the radio altimeter fails.

[0018] Beneficial effects

[0019] A method and system for calculating the height above the ground during the landing phase of an unmanned aerial vehicle (UAV). A calculating device for solving the real-time height above the ground of the aircraft through satellite position information and runway position information. When the UAV does not have a device for measuring the height above the ground, or the device for measuring the height above the ground fails, the real-time height above the ground of the UAV is solved, and the flight control system is used to control the UAV to approach and land, effectively improving the landing point accuracy and avoiding aircraft damage caused by height information errors.

[0020] By accurately solving the height above the ground of the UAV when it enters the airspace above the runway, the present invention effectively improves the landing point accuracy of the UAV and avoids situations such as the UAV running out of the runway due to insufficient runway distance during the landing phase, the aircraft bouncing up due to too high a landing speed, damage to the landing gear, and even damage to the aircraft. At the same time, for UAVs equipped with height above the ground measurement sensors, the solved height above the ground information is used as redundancy, and when the height above the ground measurement sensor fails, it switches to calculating the height above the ground, improving the reliability and safety of the UAV. Description of the drawings

[0021] Figure 1 : Schematic diagram of the system for calculating the height above the ground during the landing phase of an unmanned aerial vehicle

[0022] Figure 2 : Top view schematic diagrams of various positions for calculating the height above the ground during the landing phase of an unmanned aerial vehicle

[0023] Figure 3 : Side view schematic diagrams of various positions for calculating the height above the ground during the landing phase of an unmanned aerial vehicle

[0024] Figure 4 : Side view schematic diagram of the position of the embodiment for calculating the height above the ground during the landing phase of an unmanned aerial vehicle Detailed implementation manners

[0025] Now, the present invention will be further described in combination with embodiments and drawings:

[0026] A device for calculating the height above the ground during the landing phase of an unmanned aerial vehicle, characterized in that: based on the airport position information obtained before the flight test and the position information of the UAV collected by the on-board sensors during the flight test, a device for calculating the landing height above the ground is designed. The hardware involved includes a satellite positioning system (Beidou / GPS), a ground station, and a flight control computer; the satellite positioning system measures the position information (longitude, latitude, and height) of the UAV; the ground station enters and uploads the position information (longitude, latitude, and height) of the aircraft on the runway to the height above the ground calculation module; the flight control computer receives the real-time calculation of the height above the ground of the aircraft by the height above the ground calculation module, and calculates the control amounts of each control surface and throttle, and drives the aircraft to approach and land according to the desired flight path.

[0027] AsFigure 1 As shown, the hardware of the control system involves a satellite positioning system (Beidou / GPS), a ground station, and a flight control computer. The satellite positioning system measures the longitude, latitude, and altitude of the UAV. The ground station inputs and uploads the longitude, latitude, and altitude information of each characteristic point of the runway centerline measured in advance to the altitude above ground calculation module of the flight control computer. Since the runway slope is not always constant, the selection of characteristic points should include but not be limited to the two endpoints of the runway, and generally 3 to 5 points are taken. The ground station for loading the runway position information should have a storage function, and the runway position information only needs to be measured once for each type of aircraft flying at a certain airport. The flight control computer is used to collect information from various sensors, including but not limited to: inertial navigation, attitude measurement components, atmospheric pressure sensors, satellite positioning systems, electronic fuel injection control units, perform redundancy management and control allocation according to the current flight state of the UAV, perform the calculation of corresponding control modes, obtain the control quantities of each control surface and throttle, and drive the aircraft to approach and land according to the desired trajectory. The altitude above ground calculation module is located inside the flight control computer, collects the position measurement information of the satellite positioning system, calculates the altitude of the aircraft above ground in real time, and transmits it to the redundancy management module. If the aircraft is not equipped with a radio altimeter, the calculated altitude is used as the main signal for the altitude above ground. If the aircraft is already equipped with a radio altimeter, the calculated altitude is used as the backup signal for the altitude above ground and is used when the radio altimeter fails. In Figure 1 , \(H_g\) is the altitude command; \(y_g\) is the trajectory command; \(v_g\) is the speed command; \(\delta_e\) is the elevator control quantity; \(\delta_a\) is the aileron control quantity; \(\delta_r\) is the rudder control quantity; \(\delta_t\) is the throttle control quantity; \(v\) is the flight speed; \(\phi\) is the roll angle; \(\theta\) is the pitch angle; \(\psi\) is the yaw angle; \(H\) ref is the altitude above ground at the current position of the aircraft; \(P\) is the current position of the aircraft; \(P(1)\) is the position of the lower point among the two endpoints of the runway centerline; \(P(n)\) is the position of the higher point among the two endpoints of the runway centerline; \(P(i)\) is the position of a certain characteristic point selected on the runway centerline, where \(i\leq n - 1\).

[0028] Judge the interval where the projection of the current position of the aircraft on the runway is located. Project the aircraft position onto the geodetic plane in the inertial system. The schematic diagram is as Figure 2 shown. Calculate the sum of the distances from the current position of the aircraft to the two endpoints of each runway interval respectively. The runway interval with the shortest sum of distances is the runway interval where the aircraft position is located.

[0029] As Figure 3 shown, given the information of the current position of the aircraft and \(n\) characteristic points on the runway, a general method for calculating the altitude of the aircraft above ground can be summarized. The projection of the aircraft on the runway is located in the section \(P(i)P(j)\), and the aircraft movement direction is from \(P(i)\) to \(P(j)\), then:

[0030]

[0031] The takeoff height of the aircraft after entering the runway can be obtained as follows:

[0032]

[0033] Among them, is the altitude of the projection point of the current position of the aircraft; L is the distance of the aircraft entering the current runway section; L ij is the distance between P(i) and P(j); H i is the height of point i; H j is the height of point j, and H is the current altitude of the aircraft.

[0034] As Figure 4 shown, three characteristic points are selected on the runway. Given the current position of the aircraft, the takeoff height of the aircraft can be solved in real time. After judgment, the projection of the aircraft on the runway is located in the P(2)P(3) section, then the takeoff height of the aircraft at this time

Claims

1. A method for calculating the height from the ground during the landing phase of an unmanned aerial vehicle, characterized in that The steps are as follows: Step 1: The ground station pre-measures the longitude, latitude, and altitude of each feature point on the runway center line. P(1) is the position of the lower point among the two end points of the runway center line; P(n) is the position of the higher point among the two end points of the runway center line; P(i) is the position of any feature point selected on the runway center line. Step 2: When the current position of the aircraft is P, judge the interval where the projection of the current position of the aircraft on the runway is located. The judgment method is: calculate the sum of the distances from the current position of the aircraft to the two end points of each runway interval respectively. The runway interval with the shortest sum of distances is the runway interval P(i)P(j) where the aircraft is located; P(j) is the position of the feature point adjacent to and in front of P(i) on the runway center line. Step 3: Calculate the height above the ground of the current position of the aircraft as follows: When the projection of the aircraft on the runway is located in the section P(i)P(j), and the movement direction of the aircraft is from P(i) to P(j), the altitude of the projection point of the current position of the aircraft. The height above the ground after the aircraft enters the runway: Among them, is the altitude of the projection point of the current position of the aircraft; L is the distance of the aircraft entering the current runway section; L ij is the distance between P(i) and P(j); H i is the altitude of point i; H j is the altitude of point j, and H is the current altitude of the aircraft.

2. The method for calculating the ground clearance of the drone during the landing phase according to claim 1, wherein: For the feature points on the runway center line, i ≤ n - 1.

3. A system for implementing the method for calculating the height from the ground during the landing phase of the drone according to claim 1 or 2, characterized in that It includes a satellite positioning system, a ground station, a flight control computer, an on-board sensor, and a height-above-ground calculation module; the satellite positioning system, the height-above-ground calculation module, the flight control computer, and the on-board sensor are installed on the UAV; the satellite positioning system measures the position information of the UAV and outputs the position information to the height-above-ground calculation module; the ground station enters and uploads the position information of the aircraft on the runway to the height-above-ground calculation module; after receiving the position information of the UAV and the position information of the aircraft on the runway, the height-above-ground calculation module calculates the height above the ground of the aircraft in real time and outputs it to the flight control module of the flight control computer; the flight control module receives the height above the ground of the aircraft calculated in real time by the height-above-ground calculation module and calculates the control amounts of each control surface and throttle, and drives the aircraft to approach and land according to the desired flight path; the position information includes longitude, latitude, and altitude.

4. The system according to claim 3, characterized in that: If the aircraft is not equipped with a radio altimeter, the calculated height is used as the main signal for the height above the ground. If the aircraft is equipped with a radio altimeter, the calculated height is used as the backup signal for the height above the ground and is used when the radio altimeter fails.

Images