A method for filtering and correcting takeoff and landing sideslip errors based on a piecewise coordinate system

Abstract

This invention relates to the field of aircraft parameter reliability identification, specifically a method for filtering and correcting takeoff and landing sideslip errors based on a segmented coordinate system. This invention uses a segmented airport coordinate system to continuously update the sideslip displacement of the UAV relative to the runway centerline, effectively reducing the accumulated sideslip error, smoothing error spikes, and keeping the sideslip estimation error within a tolerable range. This effectively mitigates the high risks caused by large errors in key parameters during the takeoff and landing phases of high-speed UAVs. It can also effectively reduce the runway lateral offset error caused by coordinate system transformation. This provides effective protection for the safety of large high-speed UAVs during takeoff and landing, reducing the possibility of the aircraft entering abnormal flight control logic due to false alarms caused by excessive runway lateral offset errors. This method is verified through simulation based on telemetry data from real UAVs.

Description

Technical Field

[0001] This invention relates to the field of aircraft parameter reliability identification, and specifically to a method for filtering and correcting takeoff and landing sideslip error values ​​based on a segmented coordinate system. Background Technology

[0002] High-speed unmanned aerial vehicles (UAVs) are playing an increasingly important role in the aviation field. Compared to manned aircraft, pilots cannot directly perceive the lateral offset of the aircraft relative to the runway centerline (with the takeoff point as the origin, the other end of the runway as positive, and the vertical direction to the left). This offset is a key parameter that pilots observe during takeoff and landing safety phases at ground stations, directly affecting their judgment of the mission. Furthermore, incorrect judgments of this value can trigger the onboard software to automatically terminate the mission or enter an incorrect operating mode, impacting mission execution and flight safety.

[0003] In the current mission environment, the differential BeiDou reference equipment in the ground command and control system transmits satellite navigation correction information to the aircraft in real time. The UAV collects satellite navigation and positioning information through its onboard satellite navigation and positioning equipment and calculates its current corrected real-time position P (longitude, latitude, and altitude) by combining it with the differential correction information. This information is then transmitted to the ground command and control system via a wireless link. The ground command and control system uses pre-measured precise coordinate information of both ends of the runway (latitude, longitude, and altitude information of the two ends of the available runway length) and an approximate transformation formula from the geographic coordinate system to the airport runway coordinate system to calculate the lateral offset of the aircraft relative to the runway system. This information is then updated and displayed to the pilot in real time.

[0004] The approximation of the sideslip will introduce errors as the aircraft moves away from the origin of the runway coordinate system. Actual experiments have shown that this conversion formula produces approximately 3 meters of sideslip error for every 3000 meters of a standard civil aviation runway. A typical runway is 50 meters wide with a maximum sideslip of 25 meters. For medium to large aircraft, the control law provides a safe sideslip of approximately 7-10 meters. However, considering the combined effects of runway physical smoothness, short-term wind speed and direction changes, wind shear, and other disturbances, the short-term lateral deviation of the aircraft may exceed 5 meters. Summary of the Invention

[0005] Purpose of the invention

[0006] In this situation, the lateral bias caused by formula errors is approaching the acceptable threshold for both the airborne system and the pilot. A method needs to be designed to reduce and smooth the approximation errors caused by coordinate system transformation.

[0007] Technical solution

[0008] A method for filtering and correcting takeoff and landing sideslip error values ​​based on a segmented coordinate system is proposed. This invention uses a segmented airport coordinate system to continuously update the sideslip displacement of the UAV relative to the runway centerline, which can effectively reduce the cumulative sideslip error, smooth error spikes, and keep the sideslip estimation error within a tolerable range, effectively mitigating the high risks caused by large errors in key parameters during the takeoff and landing phase of high-speed UAVs.

[0009] Includes the following steps:

[0010] Step 1: Determine the number of airport segments and the offset accuracy requirements by comprehensively considering the number of calibration points and the accuracy requirements. For a fixed airport, the available distance of the airport runway centerline is divided into N segments in our environment using satellite positioning calibration equipment.

[0011] Step 2: Use differential calibration equipment to obtain the longitude, latitude, and altitude location information of the point to be calibrated in advance, establish an airport coordinate system, and obtain the runway orientation information according to the runway heading approximation calculation formula. This completes the preparatory work for calculating the aircraft's sideslip relative to the runway centerline.

[0012] Step 3: During the mission, the UAV collects satellite navigation and positioning information through its onboard satellite navigation and positioning equipment and calculates its current corrected real-time position by combining it with differential correction information. The corrected position is then sent to the ground command and control system via a wireless link.

[0013] Step 4: Based on the real-time location information of the UAV and the origin location information of the pre-calibrated runway coordinate system group, select the calibration coordinate system closest to the UAV's location as the current matching runway coordinate system.

[0014] Step 5, according to the approximate conversion formula Δ y =-(R+h)cos(θ)cos(L) j The lateral deviation Δ of the aircraft relative to the runway centerline is calculated in real time as )×δλ+(R+h)sin(θ)×δL. y In the formula, R represents the local Earth radius (ignoring eccentricity), h represents the aircraft altitude, θ represents the airport runway direction, and L... j δλ represents the latitude of calibration point j, δλ represents the longitude error of the aircraft's real-time position relative to the current calibration point, and δL represents the latitude error of the aircraft's real-time position relative to the current calibration point.

[0015] Furthermore, step 6 also includes the following uses: providing the drone pilot with real-time information on the aircraft's lateral deflection relative to the runway centerline, providing the pilot with a more accurate and intuitive aircraft position, which can be used for visual display, mission planning, and landing instruction.

[0016] Furthermore, prior to step 1, the aircraft should have real-time positioning capabilities, and the takeoff and landing airport runways should be known.

[0017] Furthermore, the N segments in step 1 are specifically: if the 3000m long track is divided into 300m segments, then N=10, and a total of 11 calibration points need to be calibrated.

[0018] Furthermore, the selection of the number of segments N in step 1 follows the following principle: the longer the runway, the more segments, and the denser the calibration points, the more frequently the offset error is corrected, the more the divergence is suppressed, and the greater the pre-calibration workload and real-time calculation workload.

[0019] Furthermore, the establishment of the coordinate system in step 2 specifically involves calibrating N+1 points O. j Position coordinates (λ) j L j h j ), where λ j For O j Longitude value, L j For O j Point longitude value, h j For O j Longitude value of the point. (O) j With the origin as the coordinate system, the runway centerline determines the X-axis, the aircraft's flyby direction is positive, the direction perpendicular to the left of the positive X-axis is the positive Y-axis, and the direction perpendicular to the X-axis and Y-axis upwards is the Z-axis, thus establishing the runway coordinate system O. j XYZ.

[0020] Furthermore, prior to step 4, the aircraft should be in the approach glide phase or flyby phase, which is when there is a need to calculate the sideslip to assist the aircraft in aligning with the centerline of the target airport.

[0021] Furthermore, before step 4, the aircraft should have already passed at least one calibration point, that is, the aircraft should be located in the positive X-axis interval of at least one calibration coordinate system, and only then will the sideslip correction be performed.

[0022] Furthermore, one method for selecting a matching calibration coordinate system in step 4 is to select the calibration point closest to the aircraft as the current matching calibration coordinate system.

[0023] Furthermore, in step 4, the UAV will pass through runway system 1 to N in sequence during the take-off and landing phase, and may stop on a certain runway system midway. The lateral displacement is calculated based on the currently matched calibration runway system, and P(λL h) represents the position coordinates of the UAV.

[0024] Furthermore, in step 5, even if the real-time position information of the UAV and the pre-calibrated origin position information of the runway coordinate system are completely accurate, errors will still be introduced in the lateral deviation calculation due to coordinate system transformation, which is also the suppression target of this method.

[0025] The beneficial effects of this application are as follows:

[0026] Simulation tests show that this method can reduce the maximum error caused by the approximate transformation to one-tenth of the original error, effectively reducing the error of the lateral offset relative to the runway centerline in the real-time calculation of the UAV take-off and landing safety critical stage by the ground command and control system.

[0027] It is worth mentioning that a denser division method can further reduce lateral offset error, but it will increase the initial calibration workload. In practical applications, the number of airport segments can be determined by comprehensively considering the number of calibration points, airport environment, and offset accuracy requirements. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating one embodiment of the segmented lateral deviation error correction method of the present invention.

[0029] Figure 2 This is a schematic diagram of a runway model for an airport.

[0030] Figure 3 This is a simulation diagram of the algorithm based on the segmented lateral deviation error correction method of this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described in more detail below. In the examples, the same or similar reference numerals denote the same or similar components or elements having the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of this invention. The embodiments described below with reference to reference are exemplary and intended to explain this invention, and should not be construed as limiting the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The embodiments of this invention will be described in detail below.

[0032] This invention employs a segmented airport coordinate system to continuously update the UAV's lateral displacement. For a fixed airport, the available distance of the airport runway centerline is divided using satellite positioning calibration equipment. In our environment, this is divided into 9 segments, requiring the calibration of 10 points O. j Position coordinates (λ) j L j h j ), where λ j For O j Longitude value, L j For O j Point longitude value, h j For O j Longitude value of the point. (O)j With the origin as the coordinate system, the runway centerline determines the X-axis, and the aircraft's nose direction is positive. The positive Y-axis is defined by the direction perpendicular to the left of the positive X-axis, and the Z-axis is defined by the direction perpendicular to both the X-axis and Y-axis. This establishes the runway coordinate system O. j XYZ.

[0033] During takeoff and landing, the UAV will pass through runway systems 1 to 10 in sequence (it may stop on a runway system along the way). The UAV will determine in real time where it is located on the positive X-axis of the nearest runway system and calculate the lateral displacement based on this runway system. P(λLh) represents the position coordinates of the UAV.

[0034] Neglecting eccentricity and assuming that the Earth's radius is approximately equal in the local area, i.e. The coordinate information can be used to establish the representation of each point in the geocentric rectangular coordinate system (ECEF system, abbreviated as e-system), taking point P(λL h) as an example:

[0035]

[0036] This can now be represented using latitude and longitude, showing the aircraft's position relative to a certain coordinate O. j The offset of the origin is

[0037] To better represent lateral slip, the offset Δ needs to be... j Represented in the runway coordinate system:

[0038]

[0039] Among them, l j Department representative O j The runway coordinate system O with the origin j XYZ, n j Department representative O j The local geographic coordinate system with the origin (using the Northeast-Right-Handed Coordinate System) is used.

[0040] Airport runway orientation is usually fixed at θ, where θ is the angle between the runway and the geographic north.

[0041] At this point, the local geographic coordinate system n can be established. j To the runway coordinate system l j Transformation matrix of the system:

[0042]

[0043] The transformation matrix established at each calibration point is the same and is written uniformly.

[0044] Establish e-system to n j Transformation matrix of the system:

[0045]

[0046] Therefore, the real-time position P(λL h) of the aircraft and the position O of the calibration point in the local airport coordinate system can be represented using only two points: latitude and longitude. j (λ j L j h j Offset between ).

[0047] Now let δλ j =λ-λ j ,δL j =LL j ,δh j =hh j .

[0048] When aircraft P has just passed the calibration point O j At that time, δλ j δL j δh j Since all quantities are small, we can ignore higher-order small quantities and simplify the aircraft's sideslip relative to the runway centerline as follows:

[0049] Δ y =-(R+h)cos(θ)cos(L) j )×δλ+(R+h)sin(θ)×δL

[0050] Obviously, as the distance between aircraft P and calibration point O increases... j The greater the distance, the more errors will be introduced into the lateral deviation calculation:

[0051] (1) Due to δλ j δL j δh j The inherent error in the model is caused by a small number of incorrect assumptions.

[0052] (2)Δ y It will itself follow δλ j δL j It increases with the increase of.

[0053] The error calculated by the segmented side-bias filtering correction method used in this invention is:

[0054] Δ=Δ j When the aircraft P is located at O j The X-axis of XYZ is positive and coincides with O. j Closest distance.

[0055] At this point, by increasing the number of calibration points, once the aircraft is matched to the next calibration track system, the coordinates of the new calibration system origin are used as the observation input to correct the lateral deviation error and avoid δλ. j δLj δh j The random object's position is increased indefinitely while maintaining the model's accuracy.

[0056] Please see Figure 1 , Figure 1 This is a flowchart illustrating one embodiment of the segmented lateral deviation error correction method of the present invention.

[0057] It should be noted that the segmented lateral deviation error correction method described in this embodiment may include, but is not limited to, the following steps.

[0058] Step 1: Determine the number of airport segments and the number of calibration points by comprehensively considering the number of calibration points, airport environment, and offset accuracy requirements, and determine the calibration points to be determined.

[0059] Step 2: Use differential calibration equipment to obtain the longitude, latitude, and altitude location information of the point to be calibrated in advance, establish an airport coordinate system, and obtain the runway orientation information according to the runway heading approximation calculation formula. This completes the preparatory work for calculating the aircraft's sideslip relative to the runway centerline.

[0060] Step 3: During the mission, the UAV collects satellite navigation and positioning information through its onboard satellite navigation and positioning equipment and calculates its current corrected real-time position by combining it with differential correction information. The corrected position is then sent to the ground command and control system via a wireless link.

[0061] Step 4: Based on the real-time location information of the UAV and the pre-calibrated origin location information of the runway coordinate system group, select the runway coordinate system that is closest to the UAV and where the UAV is located in the positive X-axis direction as the current reference runway coordinate system.

[0062] Step 5: Calculate the aircraft's lateral deviation relative to the runway centerline in real time using the approximate conversion formula.

[0063] It is worth mentioning that this invention does not require the addition of extra sensors; it optimizes the approximate calculation of the lateral deviation amount only from an algorithmic perspective.

[0064] It is worth mentioning that this invention does not significantly increase the amount of computation, but only increases the number of pre-calibrated points before the task, and will not cause significant computational burden during the actual task.

[0065] Please see Figure 2 , Figure 2 This is a schematic diagram of a runway model for an airport.

[0066] like Figure 2 Ten coordinate systems were evenly divided along the runway centerline, resulting in 11 calibration points. Each calibration point O was designated as a coordinate system. jWith the origin as the coordinate system, the runway centerline determines the X-axis, and the aircraft's nose direction is positive. The positive Y-axis is defined by the direction perpendicular to the left of the positive X-axis, and the Z-axis is defined by the direction perpendicular to both the X-axis and Y-axis. This establishes the runway coordinate system O. j XYZ.

[0067] During takeoff and landing, the aircraft will move sequentially along the runway centerline from coordinate system O1X1Y1Z1 to coordinate system O 10 X 10 Y 10 Z 10 The runway is approximately 4000m long.

[0068] In practical applications, the runway division density can be determined by considering factors such as runway length, whether the take-off and landing environment is ideal, and the amount of calibration work.

[0069] Please see Figure 3 , Figure 3 This is a simulation diagram of the algorithm based on the segmented lateral deviation error correction method of this invention.

[0070] like Figure 3 The blue line represents the side deviation calculated using the traditional approximation method. As the distance between the UAV and the origin of the airport coordinate system increases, the error in the calculated side deviation increases rapidly.

[0071] like Figure 3 The red line represents the sideslip amount calculated using the segmented sideslip error correction method proposed in this invention. The sideslip error increases within the current coordinate system, but once the aircraft enters the next coordinate system, the sideslip error is significantly corrected.

[0072] like Figure 3 Simulation results for a runway of approximately 4 kilometers show that the traditional approximation method has a lateral deviation error of 0.857601m. In actual missions, considering factors such as crosswinds and line of sight, the lateral deviation error is even greater. However, the method proposed in this invention calculates a lateral deviation error of only 0.085751m, which is 90% lower than the traditional method.

[0073] Furthermore, unless otherwise defined, the technical or scientific terms used in this application description shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "upper," "lower," "left," "right," "center," "vertical," "horizontal," "inner," and "outer," etc., used in this application description to indicate relative direction or positional relationship are used only to indicate relative orientation or positional relationship, and do not imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. When the absolute position of the described object changes, its relative positional relationship may also change accordingly, and therefore should not be construed as a limitation on this application. The terms "first," "second," "third," and similar terms used in this application description are used only for descriptive purposes to distinguish different components, and should not be construed as indicating or implying relative importance. The terms "a," "one," or "the," etc., used in this application description should not be construed as an absolute limitation on quantity, but should be construed as indicating the existence of at least one. The terms "including," "comprising," etc., used in this application description mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, without excluding other elements or objects.

[0074] Furthermore, it should be noted that, unless otherwise explicitly specified and limited, terms such as “installation,” “connection,” and “linkage” used in the description of this application should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can be a connection within two components. Those skilled in the art can understand its specific meaning in this application according to the specific circumstances.

[0075] The above description is merely a specific embodiment of the present invention and is not intended to limit the present invention. Within the spirit and principles of the present invention, any person skilled in the art may use the above-disclosed technical content to make changes or modifications to equivalent embodiments and apply them to other fields. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, as well as any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention.

Claims

1. A method for filtering and correcting takeoff and landing sideslip error values ​​based on a piecewise coordinate system, characterized in that, A segmented airport coordinate system is used to continuously update the lateral displacement of the UAV relative to the runway centerline; including the following steps: Step 1: Determine the number of airport segments and the offset accuracy requirements by comprehensively considering the number of calibration points and the calibration points; for a fixed airport, use satellite positioning calibration equipment to divide the available distance of the airport runway centerline into N segments in the environment. Step 2: Use differential calibration equipment to obtain the longitude, latitude, and altitude location information of the point to be calibrated in advance, establish an airport coordinate system group, and obtain the runway direction information according to the runway heading approximation calculation formula; This completes the preparatory work for calculating the aircraft's sideslip relative to the runway centerline. Step 3: During the mission, the UAV collects satellite navigation and positioning information through its onboard satellite navigation and positioning equipment and calculates its current corrected real-time position by combining it with differential correction information. The corrected position is then sent to the ground command and control system via a wireless link. Step 4: Based on the real-time location information of the UAV and the origin location information of the pre-calibrated runway coordinate system group, select the calibration coordinate system closest to the UAV's location as the current matching runway coordinate system; Step 5, according to the approximate conversion formula Δ y =-(R+h)cos(θ)cos(L) j The lateral deviation Δ of the aircraft relative to the runway centerline is calculated in real time as )×δλ+(R+h)sin(θ)×δL. y In the formula, R represents the local Earth radius (ignoring eccentricity), h represents the aircraft altitude, θ represents the airport runway direction, and L... j δλ represents the latitude of calibration point j, δλ represents the longitude error of the aircraft's real-time position relative to the current calibration point, and δL represents the latitude error of the aircraft's real-time position relative to the current calibration point.

2. The method as described in claim 1, characterized in that, It also includes the use of step 6: providing the drone pilot with real-time lateral deflection of the aircraft relative to the runway centerline, providing the pilot with the aircraft position, which can be used for visual display, mission planning and landing instruction.

3. The method as described in claim 1, characterized in that, Before step 1, the aircraft should have real-time positioning capabilities and the takeoff and landing airport runways should be known.

4. The method as described in claim 1, characterized in that, The N segments in step 1 are specifically: the 3000m long track is divided into 300m segments, so N=10, and a total of 11 calibration points need to be calibrated.

5. The method as described in claim 1, characterized in that, The establishment of the coordinate system in step 2 specifically involves calibrating N+1 points O. j Position coordinates (λ) j L j h j ), where λ j For O j Longitude value, L j For O j Point longitude value, h j For O j Point longitude value; with O j With the origin as the coordinate system, the runway centerline determines the X-axis, the aircraft's flyby direction is positive, the direction perpendicular to the left of the positive X-axis is the positive Y-axis, and the direction perpendicular to the X-axis and Y-axis upwards is the Z-axis, thus establishing the runway coordinate system O. j XYZ.

6. The method as described in claim 1, characterized in that, Before step 4, the aircraft should be in the approach glide phase or flyby phase, which means there is a need to calculate the sideslip to help the aircraft align with the centerline of the target airport. Before step 4, the aircraft should have already passed at least one calibration point, meaning the aircraft is in the positive X-axis interval of at least one calibration coordinate system, and only then will sideslip correction be performed. One method for selecting the matching calibration coordinate system in step 4 is to select the calibration point closest to the aircraft as the current matching calibration coordinate system.

7. The method as described in claim 1, characterized in that, In step 4, the UAV will pass through runway system 1 to N in sequence during the take-off and landing phase, and may stop on a certain runway system midway. The lateral displacement is calculated based on the currently matched calibration runway system, and P(λL h) represents the position coordinates of the UAV.

Images