Multi-method unmanned aerial vehicle simulation satellite control system under evaluation strategy

Abstract

The invention provides a multi-method unmanned aerial vehicle simulation satellite control system under an evaluation strategy, and the system comprises a satellite orbit prediction module which is used for carrying out the satellite orbit prediction, and transmitting the orbit prediction information to an unmanned aerial vehicle route planning module; the unmanned aerial vehicle flight path planning module is used for receiving the orbit prediction information, performing unmanned aerial vehicle flight path planning according to working scene requirements, and generating flight path points; and the simulation precision evaluation module is used for receiving the flight path points sent by the unmanned aerial vehicle flight path planning module and carrying out evaluation by adopting unmanned aerial vehicle flight control errors, if the precision requirement is not met, the information that the requirement is not met is sent to the unmanned aerial vehicle flight path planning module, and the unmanned aerial vehicle flight path planning module modifies parameters and regenerates the flight path points. According to the invention, the problem of incomplete consideration of maneuvering characteristic constraints of the unmanned aerial vehicle is effectively solved, and the application range of the method for simulating satellite transit by the unmanned aerial vehicle is enlarged; a precision evaluation strategy is provided to guide calculation of track points, and the accuracy and feasibility of the unmanned aerial vehicle simulation satellite are improved.

Description

Technical Field

[0001] This invention relates to the field of satellite remote sensing technology, specifically to a multi-method unmanned aerial vehicle (UAV) simulation satellite control system under an evaluation strategy. Background Technology

[0002] Satellite remote sensing, as a core technology for Earth observation, has wide applications in environmental monitoring, geological exploration, agriculture, and national defense due to its unique advantages in air-to-ground observation. In satellite remote sensing imaging missions, ground control stations are crucial ground support for ensuring stable satellite operation, data communication, and the implementation of various satellite applications. Operational training at ground control stations is an indispensable part of satellite remote sensing missions. However, training based on real, in-orbit satellites faces multiple bottlenecks: satellite resources are highly limited, practical training is easily constrained by international space regulations, and the scheduling cycle for high-value satellites is long and risk management is difficult, making it hard to meet the needs of high-frequency, multi-scenario training; real satellite transit trajectories are fixed, making it impossible to flexibly reproduce operational scenarios in complex environments, resulting in insufficient relevance and repeatability of training scenarios. Unmanned aerial vehicles (UAVs), with their maneuverability, cost-effectiveness, and customizable payloads, can dynamically reproduce satellite orbital motion in designated airspace, achieving more flexible and higher-quality remote sensing imaging, making them an ideal platform for simulating satellite transits.

[0003] However, existing drone simulation training systems have significant technical shortcomings:

[0004] (1) Failure to consider UAV maneuverability constraints: Traditional methods are mainly based on trajectory planning methods at fixed flight altitudes and distance scaling methods based on quadratic function relationships. The former fails to consider UAV maneuverability constraints. When simulating at lower altitudes, even small disturbances of the UAV can exceed the field of view of the ground control station's monitoring equipment. When simulating at higher altitudes, the UAV may be too fast during the simulated satellite approach and exit phases. Although the latter considers UAV maneuverability constraints, this method is prone to large differences in the approach and exit distance scaling coefficients due to factors such as different UAV ascent and descent capabilities and large differences in the slant ranges of approaching and exiting satellites. This causes the fitted quadratic function to have a larger slant range R and a smaller k within a certain range, and even a negative k value. As a result, the distance r=R / k between the UAV and the ground control station during approach and exit will be larger or even impossible to find. This leads to either the UAV trajectory being unable to be calculated or the slant range and flight speed remaining large during approach and exit, making the UAV flight trajectory more complex. Moreover, this method fails to consider the limitations of the UAV's maximum yaw angle, maximum pitch angle, and maximum distance.

[0005] (2) The trajectory planning method is simplistic and does not consider the impact of UAV control accuracy: Such systems employ a single trajectory planning method, generally providing only one simulation approach, which is insufficient to meet the needs of UAVs simulating satellites in different scenarios. Moreover, current systems directly plan trajectories without considering the impact of UAV control accuracy on ground control station observations. When UAV control accuracy is poor and flight paths fluctuate drastically, the planned trajectory may exceed the observation range of the ground control station. This issue is often only discovered after actual flight testing, requiring continuous adjustments and test flights, wasting significant resources and limiting the system's accuracy and feasibility to some extent. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a multi-method UAV simulated satellite control system under an evaluation strategy, comprising: a satellite orbit prediction module, a UAV trajectory planning module, and a simulation accuracy evaluation module, wherein...

[0007] The satellite orbit prediction module is used to predict satellite orbits and transmit the orbit prediction information to the UAV trajectory planning module.

[0008] The UAV trajectory planning module is used to receive trajectory prediction information, plan the UAV trajectory according to the needs of the work scenario, and generate waypoints.

[0009] The simulation accuracy assessment module receives the waypoints sent by the UAV trajectory planning module and evaluates them using UAV flight control errors. If the accuracy requirements are not met, it sends a message indicating that the requirements are not met to the UAV trajectory planning module, which then modifies the parameters and regenerates the waypoints. If the accuracy requirements are met, it sends a message indicating that the requirements are met to the UAV trajectory planning module, which then transmits the waypoints to the UAV flight control system.

[0010] Furthermore, the UAV trajectory planning module includes a UAV simulated satellite unit and a coordinate calculation unit. The UAV simulated satellite unit calculates the UAV's coordinates relative to the ground control station in a station-centered polar coordinate system, while the coordinate calculation unit converts these coordinates to geodetic coordinates. Within the UAV simulated satellite unit, when there are no special requirements for distance, speed, or altitude, an improved distance scaling method is used to obtain UAV trajectory points that meet the constraints and accuracy requirements of UAV maneuverability. The method includes:

[0011] Set constraints on the maneuverability of the drone:

[0012] ,

[0013] In the formula, 'a' represents redundancy, 'φ' represents the UAV's yaw angle, and φ max θ is the maximum yaw angle of the UAV, and θ is the pitch angle of the UAV. maxH is the maximum pitch angle of the drone. max With H min These are the maximum and minimum flight altitudes of the drone, V max With V min These are the maximum and minimum flight speeds of the drone, Vup max Vdown max These represent the maximum climb and descent speeds of the drone, Vup min Vdown min L represents the minimum speed for the drone's ascent and descent, respectively. max The distance to the furthest flight point of the UAV, h, v, v up v down 1 and 2 represent the drone's altitude, flight speed, climb rate, descent rate, and waypoint distance, respectively.

[0014] The relationship between the distance scaling factor and the distance function is as follows:

[0015] k = aR + b,

[0016] In the formula, k is the range scaling factor, and R is the distance (slant range) between the satellite and the ground control station. The coefficients a and b are obtained by fitting the three sets of range scaling factors and slant ranges for approach, overpass, and exit from the station using the least squares method.

[0017] Furthermore, methods for determining the range scaling factor during simulated satellite approach include:

[0018] The constraints for entering the station are set as follows:

[0019] ,

[0020] In the formula, h0, v0, v up0 l0 represents the altitude, flight speed, climb rate, and waypoint distance at the time of approach;

[0021] First, take the distance scaling factor as an arbitrary value, calculate the UAV trajectory, and obtain the parameters of the UAV simulating satellite approach. By iterating continuously according to the constraints, the minimum distance scaling factor k0 that satisfies the conditions can be obtained.

[0022] Furthermore, methods for determining the range scaling factor when simulating satellite departure include:

[0023] The constraints for satellite departure are set as follows:

[0024] ,

[0025] First, take the distance scaling factor as an arbitrary value, and after calculating the UAV's flight path, the altitude h of the UAV simulating satellite departure can be obtained. Δt Flight speed v Δt descent speed vdownΔt Distance from trackpoint l Δt By iteratively applying the constraints, the minimum distance scaling factor k that satisfies the conditions can be obtained. Δt .

[0026] Furthermore, methods for determining the range scaling factor during simulated satellite overhead passage include:

[0027] Set the constraints as follows:

[0028] ,

[0029] In the formula, h Δt / 2 v represents the flight altitude of the drone when it passes overhead. Δt / 2 Δt represents the flight speed of the drone when it passes overhead, and Δt represents the satellite's transit time.

[0030] First, take an arbitrary distance scaling factor, and after calculating the UAV's trajectory, the altitude h of the UAV simulating satellite overhead can be obtained. Δt / 2 Flight speed v Δt / 2 Distance from trackpoint l Δt / 2 The minimum value k that satisfies the constraints is obtained by iteratively applying the constraints. Δt / 2 .

[0031] Furthermore, after obtaining the functional relationship of k, the pitch angle of the UAV is calculated. If the pitch angle requirement is not met, k is incremented step by step at predetermined intervals when passing over the top. Δt / 2 The value of k is used to refit the functional relationship of k, and then the pitch angle of the UAV is calculated again until the pitch angle requirement is met.

[0032] Calculate the yaw angle φ. If the yaw angle is greater than the UAV's maximum yaw angle, decrease the value of b in the function expression at predetermined intervals. Then recalculate whether the UAV's yaw angle satisfies the constraints and check whether it meets the constraints of altitude, flight speed, descent speed, waypoint distance, and pitch angle. Continue until a linear function relationship with respect to k that satisfies all constraints is found, and output the linear function relationship with respect to k. If the yaw angle cannot be simultaneously satisfied with the constraints of altitude, flight speed, descent speed, waypoint distance, and pitch angle, return the indicators that the UAV can satisfy, so that a high-performance UAV can be replaced.

[0033] Furthermore, in the UAV-simulated satellite unit, based on the orbit prediction information, the UAV and the satellite are set to have the same azimuth and elevation angles relative to the ground control station, and the distance between the UAV and the ground control station is r=R / k. The station-centered polar coordinates of the UAV relative to the ground control station are then calculated.

[0034] Furthermore, in the UAV simulation satellite unit, when it is necessary to minimize the speed change of the UAV during flight, a fixed scaling method is used to obtain the UAV waypoints, including:

[0035] The scaling factor k is arbitrarily set, and the slant distance r of the UAV relative to a fixed point on the ground is obtained using the formula:

[0036] ,

[0037] Where k is the scaling factor, the next step is to calculate the UAV's waypoints to obtain various parameters of the UAV, and then compare whether they are within the constraints of the UAV's maneuverability performance indicators. The constraints are:

[0038] ,

[0039] If the value is lower than the minimum boundary value, the value of k is continuously decreased by a predetermined step size. If the value is higher than the maximum boundary value, the value of k is continuously increased by a certain step size until the constraint conditions are met and a suitable value of k is obtained. If the UAV flight index is within the range of UAV maneuverability constraints under this value of k, the simulation accuracy is evaluated. If the evaluation result is within the specified accuracy range, the waypoint is output. If it is not within the specified accuracy range, the value of k is continuously decreased by a predetermined step size until both the UAV maneuverability constraints and the simulation accuracy requirements are met.

[0040] Furthermore, in the UAV simulation satellite unit, when the UAV's takeoff and landing capabilities are weak or maneuverability in altitude control is difficult, an improved fixed-altitude method is used to calculate the UAV's slant range, including:

[0041] By arbitrarily setting the drone altitude h, the slant distance r of the drone can be calculated using the following formula:

[0042] ,

[0043] In the formula, E is the elevation angle of the satellite relative to the ground control station. The UAV's flight path points are calculated to obtain UAV parameter information, which is then compared to see if it falls within the constraints of the UAV's maneuverability performance indicators. The constraints are:

[0044] ,

[0045] If the value is lower than the minimum boundary value, the h value is continuously increased by a predetermined step size. If the value is higher than the maximum boundary value, the h value is continuously decreased by a predetermined step size until the constraint requirements are met and a suitable h value is obtained. If the UAV flight index is within the UAV maneuverability constraint conditions under this h value, the simulation accuracy is evaluated. If the evaluation result is within the specified accuracy range, the waypoint is output. If it is not within the specified accuracy range, the h value is continuously increased by a predetermined step size until both the UAV maneuverability constraint requirements and the simulation accuracy requirements are met.

[0046] Furthermore, in the simulation accuracy evaluation module, the coordinate data of the UAV in the vertical measurement coordinate system of the ground telemetry station is received from the UAV trajectory planning module. The errors in the x, y, and z directions in the vertical measurement coordinate system are set as follows:

[0047] ,

[0048] Where n represents the UAV flight control accuracy, and i is the track point number; by introducing the three directional errors and transforming the vertical measurement coordinate system into the station center coordinate system, the formula is:

[0049] ,

[0050] ,

[0051] Compare the azimuth angle A and pitch angle E with the initial azimuth angle and pitch angle of the UAV, and obtain the difference between A and E respectively. Compare the difference between the azimuth angle and pitch angle with the field of view of the ground monitoring equipment. If the difference between the azimuth angle and pitch angle is less than the field of view of the monitoring equipment, the simulation accuracy meets the monitoring requirements; otherwise, the simulation accuracy does not meet the standards.

[0052] Compared with the prior art, the trajectory planning method provided by the present invention has the following beneficial effects:

[0053] (1) Four methods were proposed: improved distance scaling method, fixed scaling method, fixed distance method and improved fixed height method, so as to enable flexible selection in multiple scenarios and meet diverse simulation needs.

[0054] (2) The improved distance scaling method effectively solves the problem that the existing methods do not take into account or do not fully take into account the constraints on the maneuverability of UAVs, and increases the applicability of the UAV simulated satellite transit method.

[0055] (3) Propose an accuracy assessment strategy to guide the calculation of waypoints, so as to improve the accuracy and feasibility of UAV-based satellite simulation. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the structure of a multi-method UAV simulated satellite control system under an evaluation strategy according to an embodiment of the present invention;

[0057] Figure 2 This is a schematic diagram illustrating the principle of a simulated trajectory according to an embodiment of the present invention;

[0058] Figure 3 This is a schematic diagram of the workflow of the improved distance scaling method of the present invention;

[0059] Figure 4 This is a schematic diagram illustrating the flight trajectory effects of the four methods of the present invention;

[0060] Figure 5 A comparison chart of flight trajectory, altitude, speed, and slant distance before and after the improvement using the distance scaling method (the method before the improvement did not report any errors);

[0061] Figure 6 This is a comparison chart of flight trajectory, altitude, speed, and slant distance before and after the improvement using the distance scaling method (error information for the method before improvement). Detailed Implementation

[0062] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] The multi-method UAV simulation satellite control system under the evaluation strategy proposed in this invention, such as Figure 1 As shown, it includes a satellite orbit prediction module, a UAV trajectory planning module, and a simulation accuracy evaluation module.

[0064] The satellite orbit prediction module is used to predict satellite orbits. Specifically, it includes: obtaining the relative position coordinates of the satellite with respect to the ground control station when it passes over the ground, based on the geographical coordinates of the ground control station, the number of two rows of satellite orbits, the start and end times, the calculation step size, and the minimum observation angle requirement for satellite overpass; calculating the azimuth, elevation angle, and slant range of the satellite with respect to the ground control station; and transmitting this data to the UAV trajectory planning module.

[0065] The UAV trajectory planning module is used to plan trajectories based on the requirements of the work scenario, generate waypoints, and send the waypoints to the simulation accuracy evaluation module for evaluation. If the simulation accuracy evaluation module returns information indicating that the accuracy requirements are not met, the parameters are modified and the waypoints are regenerated; if the requirements are met, the planned waypoints are transmitted to the UAV flight controller for flight.

[0066] The simulation accuracy assessment module is used for feasibility and accuracy evaluation after trajectory planning. It analyzes the UAV flight control error, specifically the difference between the UAV's current position and a preset position. The preset position is the planned trajectory position, while the actual flight position is the UAV's position when flying according to the preset position. The difference between the two is the flight control error, which is generally a fixed value obtained through statistical analysis of the UAV's past flight data. For example, the flight control error of a UAV equipped with RTK is generally below 0.1m, so the control error of this UAV is taken as 0.1m. In one embodiment, a sine wave is introduced into the actual UAV flight control error to obtain the UAV's position deviation after the error is introduced. This deviation is then converted into azimuth and pitch angle deviation data from the ground control station. If the deviation exceeds a set threshold, the trajectory planning module is not informed that the accuracy requirements are not met; otherwise, the accuracy requirements are met.

[0067] In one embodiment, the UAV-simulated satellite control system further includes a flight accuracy evaluation module. This module, after trajectory planning is completed and the UAV has flown, compares the UAV's flight position information (longitude, latitude, and altitude) with the planned trajectory points and performs coordinate transformation to obtain the deviation of the UAV's azimuth and pitch angles. The magnitude of this deviation is used to evaluate flight quality and the accuracy of the UAV's simulated satellite transit. This result can be compared with the deviation data from the simulation accuracy evaluation module. If the two evaluation results are consistent, it indicates that the flight control error introduced by the simulation accuracy evaluation module is reasonable; otherwise, it is necessary to recalculate the control error based on previous flight data or change the flight environment, such as flying in lower wind speeds and better weather conditions.

[0068] The following is a detailed explanation of each module.

[0069] In the satellite orbit prediction module, based on the satellite's two-line elements (TLE elements), the geographic coordinates of the ground control station, the start and end times, the calculation step size, and the minimum observation angle requirement for satellite transit, the SGP4 satellite orbit prediction model is used to calculate the satellite's transit time information and its position relative to the ground control station during transit. This yields the satellite's polar coordinates relative to the ground control station (azimuth A, elevation E, and slant distance R). The two-line elements (TLE elements) are known and readily available, containing all initial information about the satellite's orbital motion. The geographic coordinates of the ground control station are measured and include longitude, latitude, and altitude. The start and end times and calculation step size are set autonomously. The start and end times must include the satellite transit time, so they need to be set to a relatively long period, typically one day or more. The minimum observation angle for satellite transit is set based on the minimum elevation observation angle of the ground observation station's equipment. The SGP4 satellite orbit prediction model is a commonly used low-Earth orbit (LEO) satellite prediction model.

[0070] The UAV trajectory planning module includes a UAV satellite simulation unit and a coordinate transformation unit. The principle of UAV satellite simulation is to position the UAV and the satellite at the same azimuth and elevation angles relative to the ground control station. Since the ground control station uses a ground turntable to track and monitor the satellite, the turntable exhibits identical movements when tracking both the UAV and the satellite. This allows ground operators to perform identical operations while tracking both the satellite and the UAV, thus simulating the UAV's observation of a satellite transit. Because calculating the UAV's trajectory coordinates also requires knowing the UAV's slant range *r*, the UAV satellite simulation unit obtains different slant ranges *r* using various methods, such as... Figure 2 As shown, completely different UAV flight paths are obtained, greatly enriching the application scenarios of UAV satellite simulation. The coordinate transformation unit is used to receive the UAV station-centered polar coordinates (A,E,r) transmitted by the UAV satellite simulation unit, and then obtain the UAV geodetic coordinates through coordinate transformation, that is, the UAV flight path points. The UAV flight paths obtained by different methods in this module with the same data input from the satellite orbit prediction module are shown in the figure. Figure 4 As shown.

[0071] (1) In the UAV simulated satellite unit, when there are no special requirements for distance, speed, altitude, etc., the improved distance scaling method is used to obtain the UAV waypoints, such as... Figure 3 As shown, the trajectory that best meets the constraints of the UAV's maneuverability and accuracy requirements is obtained.

[0072] The improved distance scaling method refers to obtaining the UAV's slant range by multiplying the satellite slant range by a scaling factor k. A larger value of this scaling factor k indicates that the UAV is closer to the telemetry and control station, has a lower flight altitude, and a slower flight speed. This factor is not fixed but determined through a functional relationship with the satellite slant range. To improve the feasibility of the UAV trajectory, the calculation of this factor needs to consider the constraints of the UAV's maneuverability (including yaw and pitch angles, flight altitude, flight speed, climb rate, descent rate, and trajectory distance), ensuring that the planned trajectory meets the UAV's maneuverability constraints. Furthermore, the UAV's maneuverability should have a certain redundancy relative to the actual planned trajectory, with a redundancy of 'a' (generally 20%~30%). That is, the maximum maneuverability of the UAV is 1-a, and the minimum is 1+a. The following constraints must be met:

[0073] ,

[0074] In the formula, 'a' represents redundancy, 'φ' represents the UAV's yaw angle, and φ max θ is the maximum yaw angle of the UAV, and θ is the pitch angle of the UAV. max H is the maximum pitch angle of the drone. max With H min These are the maximum and minimum flight altitudes of the drone, Vmax With V min These are the maximum and minimum flight speeds of the drone, Vup max Vdown max These represent the maximum climb and descent speeds of the drone, Vup min Vdown min L represents the minimum speed for the drone's ascent and descent, respectively. max The distance to the furthest flight point of the UAV, h, v, v up v down 1 and 2 represent the drone's altitude, flight speed, climb rate, descent rate, and waypoint distance, respectively. The maximum value of these indicators considers the drone's maximum maneuverability, while the minimum value considers the minimum altitude and speed required for safe flight due to terrain and environmental factors. In scenarios without specific requirements, these values ​​can be 0.

[0075] The relationship between the distance scaling factor and the distance function given in this invention is as follows:

[0076] k=aR+b

[0077] In the formula, k is the range scaling factor, and R is the distance (slant range) between the satellite and the ground control station. Then, the coefficients a and b are fitted using the least squares method through three sets of range scaling factors and slant ranges for approach, overpass, and exit.

[0078] The effects of using this function include: (1) Except for cases where the flight limit of the UAV is extremely low, the distance scaling factor obtained is positively correlated with the distance, that is, the farther the distance, the larger the distance scaling factor. In this way, the slant distance of the UAV when simulating entering and leaving the station will be effectively reduced within the maneuverability of the UAV, while maintaining the maximum long-distance flight at other positions such as overhead to reduce flight error. Thus, while ensuring flight accuracy, the maximum utilization of the maneuverability of the UAV is achieved. (2) When the flight limit of the UAV is extremely low, when the fitting shows a negative correlation, since the flight limit is low at this time, the speed when entering and leaving the station is far from the speed limit of the UAV. At this time, the fitted function relationship will lead to a longer distance when entering and leaving the station, thus achieving long-distance flight within the speed limit and reducing the error.

[0079] The specific process for obtaining the distance scaling factor is as follows:

[0080] 1) Methods for determining the range scaling factor when simulating satellite approach to the station include:

[0081] The constraints upon entering the station are:

[0082] ,

[0083] In the formula, h0, v0, v up0l0 represents the altitude, flight speed, climb rate, and waypoint distance at the time of approach to the station. First, the distance scaling factor is set to an arbitrary value. After calculating the UAV's flight path, various parameters of the UAV simulating satellite approach to the station can be obtained. By iteratively applying the constraints, the minimum distance scaling factor that satisfies the conditions can be obtained, which is k0.

[0084] The specific iterative method includes: taking the initial value of the scaling factor as k. 01 The polar coordinates of the UAV at the station center were calculated for a period of time before and after the satellite entered the station, and then the scaling factor k was calculated. 01 The altitude h of the satellite during the simulated arrival at the station by the drone 01 Speed ​​v 01 Climb speed v up01 Distance from trackpoint l 01 Compare according to the constraints of the above formula: if h 01 v 01 v up01 l 01 If there exists a value less than the minimum boundary or all constraints satisfying the formula with some redundancy, then the scaling factor is determined by k. 01 Decrease the values ​​in increments at regular intervals, recalculate the altitude, speed, and climb rate of the simulated satellite approaching the station, and compare the calculated results with the constraints again. Repeat this process until h0, v0, v up0 If l0 just satisfies the boundary conditions, then the scaling factor at this point is the minimum value that satisfies the conditions.

[0085] If h 01 v 01 v up01 l 01 If any value in the above parameters is greater than the maximum boundary (the above indicators are consistent, meaning that two values ​​will not simultaneously reach their maximum and minimum values ​​respectively), then the scaling factor is determined by k. 01 The parameters are incremented at regular intervals, and the altitude, speed, and climb rate of the UAV simulating satellite approach are recalculated. The results are then compared with the constraints. This process is repeated until h0, v0, v up0 If l0 exactly satisfies all the constraints, then the scaling factor at this point is the minimum value that satisfies the conditions.

[0086] 2) Methods for determining the range scaling factor when simulating satellite departure include:

[0087] When simulating satellite departure from the UAV, under the constraints of satellite departure, the minimum range scaling factor is selected as the range scaling factor for simulating satellite departure. The constraints for satellite departure are as follows:

[0088] ,

[0089] First, take the distance scaling factor as an arbitrary value, and after calculating the UAV's flight path, the altitude h of the UAV simulating satellite departure can be obtained. Δt Flight speed v Δt descent speed v downΔt Distance from trackpoint l Δt By iterating through the constraints, the minimum distance scaling factor that satisfies the conditions can be obtained, which is k. Δt This iterative method is similar to the iterative method used when simulating station entry.

[0090] 3) Methods for determining the range scaling factor when simulating satellite overhead passage include:

[0091] When the UAV's flight time is between 0 and Δt / 2, the maximum climb speed limits the vertical height difference, which must not exceed [a certain value]. When simulating a satellite passing overhead, the vertical velocity is at its minimum and will not exceed the maximum ascent or descent velocity. Therefore, the constraint condition at this time is:

[0092] ,

[0093] In the formula, h Δt / 2 v represents the flight altitude of the drone when it passes overhead. Δt / 2 Let Δt be the flight speed of the UAV when it passes overhead, and Δt be the satellite's transit time. Similarly, by first taking an arbitrary distance scaling factor and calculating the UAV's trajectory, we can obtain the altitude h of the UAV simulating the satellite's overhead passage. Δt / 2 Flight speed v Δt / 2 Distance from trackpoint l Δt / 2 By iterating through the constraints, we can obtain the minimum value that satisfies the constraints, which is k. Δt / 2 This iterative method is similar to the iterative method used when simulating station entry.

[0094] 4) Based on the distance scaling coefficients k0 and k1 corresponding to the three points of entry, overpass, and exit obtained above, Δt / 2 k Δt And the corresponding satellite distances R0 and R Δt / 2 R Δt Using the least squares method, the fitting coefficients a and b are calculated, thus obtaining the relationship between the range scaling coefficient k and the satellite distance R. After obtaining the functional relationship of k, the pitch angle θ of the UAV throughout the entire phase is calculated. 01 If the pitch angle requirement is not met, then the overpass time k will be increased incrementally at predetermined intervals. Δt / 2The value of b is calculated (e.g., a step value of 5 can be set) until the pitch angle requirement is met. If the pitch angle requirement is met, the yaw angle φ is calculated. If the yaw angle is greater than the maximum yaw angle of the UAV, the value of b in the linear function expression is decreased at predetermined intervals (e.g., a step value of 5 can be set). After each decrease, it is calculated whether the constraints of altitude H, flight speed V, descent speed V, and waypoint distance l are still satisfied, until a function relationship that simultaneously satisfies the above conditions is found, and the function relationship of k is output. If the constraints of yaw angle, altitude, flight speed, descent speed, waypoint distance, and pitch angle cannot be satisfied simultaneously, the indicators that the UAV can satisfy are returned, so that a high-performance UAV can be replaced.

[0095] Based on the polar coordinates of the satellite's position relative to the ground control station transmitted by the satellite orbit prediction module, assuming the UAV and the satellite share the same azimuth and elevation angles relative to the ground control station, and the distance between the UAV and the ground control station is r = R / k, a series of station-centered polar coordinates (A, E, r) of the UAV relative to the ground control station can be obtained. Then, this series of coordinates is transformed using a coordinate transformation unit to obtain the UAV's geodetic coordinates, and a series of UAV perpendicular measurement coordinates (x, y, r) are obtained during the coordinate transformation process. v y v , z v The data is sent to the simulation accuracy evaluation module for accuracy assessment. If the simulation accuracy module reports that the accuracy requirements are met, the waypoints are directly output. If the expected accuracy requirements are not met, the UAV maneuverability constraints are continuously increased at predetermined intervals (generally 5%) within the UAV's maximum maneuverability range. This means the redundancy 'a' value is continuously decreased at predetermined intervals. The steps of approaching, overpassing, exiting, fitting the function, coordinate transformation, and simulation accuracy evaluation are then repeated until the expected accuracy requirements are met. If the requirements are ultimately not met, the accuracy evaluation unit provides feasible UAV performance parameters to guide the replacement with a high-performance UAV.

[0096] (2) When it is necessary to minimize the speed change of the UAV during flight, the fixed scaling method is used to obtain the UAV track points. The resulting UAV track speed change is minimal, usually less than 0.1 m / s within a height of 300 m.

[0097] The fixed scaling method also uses the azimuth and pitch angle data of the satellite relative to a fixed point on the ground to make the UAV fly with the same azimuth and pitch angle changes in order to simulate the satellite.

[0098] The scaling factor in this method is fixed. First, the scaling factor is arbitrarily set, and then the slant distance r of the UAV relative to a fixed point on the ground is obtained through the formula:

[0099] ,

[0100] Where k is the scaling factor, the next step is to calculate the UAV's waypoints to obtain various parameters of the UAV, and then compare whether they are within the constraints of the UAV's maneuverability performance indicators. The constraints are:

[0101] ,

[0102] If the value is lower than the minimum boundary value, the value of k is continuously decreased by a certain step size. If the value is higher than the maximum boundary value, the value of k is continuously increased by a certain step size until the constraint conditions are met and a suitable value of k is obtained. If the UAV flight index is within the UAV maneuverability constraint conditions under this value of k, the simulation accuracy is evaluated. If the evaluation result is within the specified accuracy range, the waypoint is output. If it is not within the specified accuracy range, the value of k is continuously decreased by a certain step size until the UAV maneuverability constraint requirements and simulation accuracy requirements are met simultaneously. If the two cannot be met simultaneously, the achievable UAV maneuverability index parameters are output or other methods are used.

[0103] (3) When it is necessary to keep the distance between the UAV and the ground control station constant during the flight, the fixed distance method is adopted. The distance of the UAV track obtained by this method remains unchanged, which is suitable for monitoring of some stations or flight testing of UAVs.

[0104] The fixed-distance method sets the distance between the UAV and the ground control station to a fixed value, and the UAV's trajectory is an arc. Specifically, it involves: first, arbitrarily setting the UAV's slant distance *r*, calculating the UAV's waypoints to obtain various UAV parameters, and comparing whether these parameters fall within the constraints of the UAV's maneuverability performance indicators. The constraints are:

[0105] ,

[0106] If the value is below the minimum boundary value, the value of r is continuously increased by a certain step size. If the value is above the maximum boundary value, the value of r is continuously decreased by a certain step size until the constraint requirements are met and a suitable value of r is obtained. If the UAV flight index is within the UAV maneuverability constraint conditions under this value of r, the simulation accuracy is evaluated. If the evaluation result is within the specified accuracy range, the waypoint is output. If it is not within the specified accuracy range, the value of r is continuously increased by a certain step size until the UAV maneuverability constraint requirements and simulation accuracy requirements are met simultaneously. If the two cannot be met simultaneously, the achievable UAV maneuverability index parameters are output or other methods are used.

[0107] (4) When the UAV has weak take-off and landing capabilities or difficulty in maneuvering control of altitude, the improved fixed altitude method is adopted. The UAV trajectory altitude obtained by this method remains unchanged, the route is simple, and it is suitable for UAVs with weak take-off and landing capabilities and difficulty in maneuvering control of altitude.

[0108] The improved fixed-altitude method sets the drone's altitude above the ground to a fixed value, meaning the drone's flight altitude remains constant. Specifically, the drone's altitude *h* is arbitrarily set, and the slant distance *r* can be calculated using the following formula:

[0109] ,

[0110] Then, by calculating the UAV's waypoints, various parameter information of the UAV can be obtained, and it can be compared whether they are within the constraints of the UAV's maneuverability indicators. The constraints are as follows:

[0111] ,

[0112] If the value is lower than the minimum boundary value, the h value is continuously increased by a predetermined step size. If the value is higher than the maximum boundary value, the h value is continuously decreased by a predetermined step size until the constraint requirements are met and a suitable h value is obtained. If the UAV flight index is within the UAV maneuverability constraint conditions under this h value, the simulation accuracy is evaluated. If the evaluation result is within the specified accuracy range, the waypoint is output. If it is not within the specified accuracy range, the h value is continuously increased by a certain step size until both the UAV maneuverability constraint requirements and the simulation accuracy requirements are met. If both cannot be met simultaneously, the achievable UAV maneuverability index parameters are output or other methods are used.

[0113] In the coordinate transformation unit, a series of station-centered polar coordinates (A1,E1,r1), (A2,E2,r2)... of the UAV are converted to UAV geodetic coordinates (L1,B1,H1), (L2,B2,H2)..., to obtain the waypoints for UAV trajectory planning. The angle calculation rules used in this system are: azimuth is 0° with north as the geodetic direction, clockwise is positive, and the range is 0°~360°; pitch is 0° with the horizon as the horizon, upward is positive, and the range is 0°~90°. Therefore, the coordinate system transformation used in this method is slightly different from the transformation from the northeast-northeast coordinate system to the geodetic coordinate system. The specific implementation method includes:

[0114] First, the coordinates (A, E, r) of the UAV in the polar coordinate system at the station center are converted to the vertical measurement coordinate system (X) with the ground control station as the origin. v Y v Z v This coordinate system differs from the Northeast-Eastern Sky coordinate system; its origin O is... v Align the monitoring equipment with the axis rotation center (intersection of the three axes); Y v Axis is O v The plumb line pointing outwards from the Earth is positive; X v The axis is through O v The intersection of the astronomical meridian plane and the horizontal plane, pointing north to the Earth, is positive; Z v Axis - with X v Y vTo establish a right-handed coordinate system, the transformation formula is as follows:

[0115] ,

[0116] Next, convert the geodetic coordinates (L, B, H) of the ground control station to the geocentric coordinate system (x, y, z). The conversion formula is as follows:

[0117] ,

[0118] in:

[0119] a. Major axis of the Earth's ellipsoid; b. Minor axis of the Earth's ellipsoid;

[0120] The first eccentricity of the Earth's ellipsoid;

[0121] Let be the radius of curvature of the Earth's orbit around the Sun;

[0122] Then, using the UAV's vertical measurement coordinate system and the geocentric coordinates of the ground fixed point, the UAV coordinates are converted to the geocentric coordinate system. The conversion formula is as follows:

[0123]

[0124] Where: (x ov ,y ov ,z ov ) represents the origin point O of the measuring station. v Coordinates in the geocentric coordinate system; O is the origin of the measuring station. v Astronomical longitude and latitude.

[0125] in: The coordinate axes rotate counterclockwise around the z-axis. The matrix, Rotate the coordinate axes clockwise around the x-axis The matrix, It is a matrix whose coordinate axes are rotated 90° counterclockwise around the y-axis.

[0126] Total matrix for:

[0127] ,

[0128] Finally, the UAV's geocentric coordinate system is converted to a geodetic coordinate system to obtain the UAV's longitude L, latitude B, and altitude H. The formula is as follows:

[0129]

[0130]

[0131]

[0132] in,

[0133]

[0134] In the formula, a is the semi-major axis of the Earth ellipsoid, b is the semi-minor axis of the Earth ellipsoid, and e is the eccentricity of the Earth ellipsoid. To calculate geodetic coordinates (L, B, H) from geocentric coordinates (x, y, z), due to accuracy issues, the above three formulas cannot be used directly. An iterative method is required, with the initial value for the iteration being:

[0135]

[0136] Then, iteratively calculate according to the following formula until the error (B) is reached. i -B i−1 ) and (H i -H i−1 Until the error is less than the pre-given allowable error.

[0137]

[0138] In the simulation accuracy evaluation module, the coordinate data of the UAV in the vertical measurement coordinate system of the ground telemetry station is received from the UAV trajectory planning module. The magnitude of the UAV flight control error is obtained through past UAV flight data, and a sinusoidal law is introduced into the UAV flight control error, i.e., the errors in the x, y, and z directions in the vertical measurement coordinate system are respectively...

[0139] ,

[0140] Where n is the UAV flight control accuracy, i.e., the general difference between the UAV's actual flight position and the preset position, obtained from the UAV's past flight data, and this value is a fixed value; i is the sequence number of a series of waypoints, i.e., the first waypoint is 1, the second waypoint is 2, and so on. Introducing the three directional errors and transforming the vertical measurement coordinate system into the station center coordinate system, the formula is:

[0141] ,

[0142] ,

[0143] After the above transformation, the azimuth angle A and pitch angle E in the station center coordinates (A,R,E) are compared with the initial azimuth angle and pitch angle. The difference between A and E is obtained. This difference is the difference between the actual flight angle and the theoretical angle. The difference between the azimuth angle and pitch angle is compared with the field of view of the ground monitoring equipment. If the difference between the azimuth angle and pitch angle is less than the field of view of the monitoring equipment, the simulation accuracy meets the monitoring requirements. Otherwise, the simulation accuracy does not meet the standard and the simulation parameters need to be adjusted.

[0144] The actual flight accuracy evaluation module compares the actual flight position information of the UAV with the planned flight path position information. This comparison is performed between a vertical measurement coordinate system and a station-centered polar coordinate system. First, the geographical location is transformed into coordinates, and then the comparison is made between the vertical measurement coordinate system and the station-centered polar coordinate system to obtain the deviations in x, y, z, azimuth, and pitch angles. The azimuth and pitch angle deviations can be verified with ground monitoring results (whether the UAV is within the field of view of ground monitoring equipment) to ensure data accuracy and provide quantitative analysis of ground monitoring. This result can be compared with the simulation accuracy evaluation module. If the two evaluation results are consistent, it indicates that the flight control error introduced by the simulation accuracy evaluation module is reasonable; otherwise, it is necessary to recalculate the control error based on previous flight data or change the flight environment, such as flying in lower wind speeds and better weather conditions. The specific implementation process of the actual flight accuracy evaluation module is as follows:

[0145] The formula for converting geodetic coordinates (L, B, H) to geocentric coordinates (x, y, z) is as follows:

[0146] ,

[0147] in:

[0148] a. Major axis of the Earth's ellipsoid; b. Minor axis of the Earth's ellipsoid;

[0149] The first eccentricity of the Earth's ellipsoid;

[0150] Let be the radius of curvature of the Earth's orbit around the Sun;

[0151] Transforming the Earth-centered, Earth-fixed coordinate system into a vertical measurement coordinate system:

[0152] ,

[0153] Where: (x ov ,y ov ,z ov ) represents the origin point O of the measuring station. v Coordinates in the geocentric coordinate system; O is the origin of the measuring station. v Astronomical longitude and latitude. Among them: Rotate the coordinate axes clockwise around the z-axis The matrix, Rotate the coordinate axes counterclockwise around the x-axis The matrix, This is a matrix whose coordinate axes are rotated 90° clockwise around the y-axis.

[0154] Formula for converting a perpendicular measurement coordinate system to a station-centered polar coordinate system:

[0155] ,

[0156] verify:

[0157] (1) Under the same UAV maneuverability constraints, the system uses the improved distance scaling method for trajectory planning. Compared with the existing distance scaling method, for example... Figure 5 As shown, the trajectory planned by this system is smoother and simpler, while the existing methods are more complex and make it difficult for drones to perform actual flights.

[0158] (2) Under the same UAV maneuverability constraints, the system still uses the improved distance scaling method for trajectory planning and compares it with the route planned by the existing distance scaling method, such as... Figure 6 As shown, this system can still plan a feasible trajectory, while the existing method's quadratic fitting results show negative trajectory altitudes and errors in coordinate transformation calculation, making it unable to plan a trajectory. The calculation results are compared below: this system works normally, while the existing method's calculation is abnormal.

[0159] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-method unmanned aerial vehicle (UAV) simulated satellite control system under an evaluation strategy, characterized in that, include: The module includes a satellite orbit prediction module, a UAV trajectory planning module, and a simulation accuracy evaluation module. The satellite orbit prediction module is used to predict satellite orbits and transmit the orbit prediction information to the UAV trajectory planning module. The UAV trajectory planning module is used to receive trajectory prediction information, plan the UAV trajectory according to the needs of the work scenario, and generate waypoints. The simulation accuracy assessment module receives the waypoints sent by the UAV trajectory planning module and evaluates them using UAV flight control errors. If the accuracy requirements are not met, it sends a message indicating that the requirements are not met to the UAV trajectory planning module, which then modifies the parameters and regenerates the waypoints. If the accuracy requirements are met, it sends a message indicating that the requirements are met to the UAV trajectory planning module, which then transmits the waypoints to the UAV flight control system.

2. The UAV-simulated satellite control system according to claim 1, characterized in that, The UAV trajectory planning module includes a UAV simulated satellite unit and a coordinate calculation unit. The simulated satellite unit calculates the UAV's coordinates relative to the ground control station in a station-centered polar coordinate system, while the coordinate calculation unit converts these coordinates to geodetic coordinates. Within the simulated satellite unit, when there are no special requirements for distance, speed, or altitude, an improved distance scaling method is used to obtain UAV waypoints that meet the constraints and accuracy requirements of UAV maneuverability. The method includes: Set constraints on the maneuverability of the drone: , In the formula, 'a' represents redundancy, 'φ' represents the UAV's yaw angle, and φ max θ is the maximum yaw angle of the UAV, and θ is the pitch angle of the UAV. max H is the maximum pitch angle of the drone. max With H min These are the maximum and minimum flight altitudes of the drone, V max With V min These are the maximum and minimum flight speeds of the drone, Vup max Vdown max These represent the maximum climb and descent speeds of the drone, Vup min Vdown min L represents the minimum speed for the drone's ascent and descent, respectively. max The distance to the furthest flight point of the UAV, h, v, v up v down 1 and 2 represent the drone's altitude, flight speed, climb rate, descent rate, and waypoint distance, respectively. The relationship between the distance scaling factor and the distance function is as follows: k = aR + b, In the formula, k is the distance scaling factor, and R is the distance between the satellite and the ground control station. The coefficients a and b are obtained by fitting the three sets of distance scaling factors and slant ranges for the satellite's entry, overpass, and exit from the station using the least squares method.

3. The UAV-simulated satellite control system according to claim 2, characterized in that, Methods for determining the range scaling factor during simulated satellite approach include: The constraints for entering the station are set as follows: , In the formula, h0, v0, v up0 l0 represents the altitude, flight speed, climb rate, and waypoint distance at the time of approach; First, take the distance scaling factor as an arbitrary value, calculate the UAV trajectory, and obtain the parameters of the UAV simulating satellite approach. By iterating continuously according to the constraints, the minimum distance scaling factor k0 that satisfies the conditions can be obtained.

4. The UAV-simulated satellite control system according to claim 2, characterized in that, Methods for determining the range scaling factor when simulating satellite departure include: The constraints for satellite departure are set as follows: ， First, take the distance scaling factor as an arbitrary value, and after calculating the UAV's flight path, the altitude h of the UAV simulating satellite departure can be obtained. Δt Flight speed v Δt descent speed v downΔt Distance from trackpoint l Δt By iteratively applying the constraints, the minimum distance scaling factor k that satisfies the conditions can be obtained. Δt .

5. The UAV-simulated satellite control system according to claim 2, characterized in that, Methods for determining the range scaling factor when simulating satellite overhead passage include: Set the constraints as follows: , In the formula, h Δt / 2 v represents the flight altitude of the drone when it passes overhead. Δt / 2 Δt represents the flight speed of the drone when it passes overhead, and Δt represents the time it takes for the satellite to pass overhead. First, take an arbitrary distance scaling factor, and after calculating the UAV's trajectory, the altitude h of the UAV simulating satellite overhead can be obtained. Δt / 2 Flight speed v Δt / 2 Distance from trackpoint l Δt / 2 The minimum value k that satisfies the constraints is obtained by iteratively applying the constraints. Δt / 2 .

6. The UAV-simulated satellite control system according to claim 2, characterized in that, After obtaining the functional relationship of k, the pitch angle of the UAV is calculated. If the pitch angle requirement is not met, k is incremented step by step at predetermined intervals when passing over the top. Δt / 2 The value of k is used to refit the functional relationship of k, and then the pitch angle of the UAV is calculated again until the pitch angle requirement is met. Calculate the yaw angle φ. If the yaw angle is greater than the maximum yaw angle of the UAV, decrease the value of b in the function expression at predetermined intervals. Then, recalculate whether the yaw angle of the UAV satisfies the constraints and check whether the constraints of altitude, flight speed, descent speed, waypoint distance, and pitch angle are satisfied. Continue until a linear function relationship with respect to k that satisfies all constraints is found and output the linear function relationship with respect to k.

7. The UAV-simulated satellite control system according to claim 2, characterized in that, In the UAV-simulated satellite unit, based on the orbit prediction information, the UAV and the satellite are set to have the same azimuth and elevation angles relative to the ground control station, and the distance between the UAV and the ground control station is r=R / k. The station-centered polar coordinates of the UAV relative to the ground control station are then calculated.

8. The UAV-simulated satellite control system according to claim 2, characterized in that, In a UAV simulation satellite unit, when it is necessary to minimize the speed change of the UAV during flight, a fixed-scale method is used to obtain the UAV waypoints, including: The scaling factor k is arbitrarily set, and the slant distance r of the UAV relative to a fixed point on the ground is obtained using the formula: , Where k is the scaling factor, the next step is to calculate the UAV's waypoints to obtain various parameters of the UAV, and then compare whether they are within the constraints of the UAV's maneuverability performance indicators. The constraints are: ， If the value is lower than the minimum boundary value, the value of k is continuously decreased by a certain step size. If the value is higher than the maximum boundary value, the value of k is continuously increased by a certain step size until the constraint conditions are met and a suitable value of k is obtained. If the UAV flight index is within the UAV maneuverability constraint conditions under this value of k, the simulation accuracy is evaluated. If the evaluation result is within the specified accuracy range, the waypoint is output. If it is not within the specified accuracy range, the value of k is continuously decreased by a predetermined step size until both the UAV maneuverability constraint requirements and the simulation accuracy requirements are met.

9. The UAV-simulated satellite control system according to claim 2, characterized in that, In a UAV simulation satellite unit, when the UAV's takeoff and landing capabilities are weak or altitude maneuver control is difficult, an improved fixed-altitude method is used to calculate the UAV's slant range, including: By arbitrarily setting the drone altitude h, the slant distance r of the drone can be calculated using the following formula: , In the formula, E is the elevation angle of the satellite relative to the ground control station. The UAV's flight path points are calculated to obtain UAV parameter information, which is then compared to see if it falls within the constraints of the UAV's maneuverability performance indicators. The constraints are: ， If the value is lower than the minimum boundary value, the h value is continuously increased by a certain step size. If the value is higher than the maximum boundary value, the h value is continuously decreased by a certain step size until the constraint requirements are met and a suitable h value is obtained. If the UAV flight index is within the UAV maneuverability constraint conditions under this h value, the simulation accuracy is evaluated. If the evaluation result is within the specified accuracy range, the waypoint is output. If it is not within the specified accuracy range, the h value is continuously increased by a predetermined step size until both the UAV maneuverability constraint requirements and the simulation accuracy requirements are met.

10. The UAV-simulated satellite control system according to claim 1, characterized in that, In the simulation accuracy evaluation module, the coordinate data of the UAV in the vertical measurement coordinate system of the ground telemetry station is received from the UAV trajectory planning module. The errors in the x, y, and z directions in the vertical measurement coordinate system are set as follows: , Where n represents the UAV flight control accuracy, and i is the track point number; introducing the three directional errors and transforming the perpendicular measurement coordinate system into the station center coordinate system, the formula is: , ， Compare the azimuth angle A and pitch angle E with the initial azimuth angle and pitch angle of the UAV, and obtain the difference between A and E respectively. Compare the difference between the azimuth angle and pitch angle with the field of view of the ground monitoring equipment. If the difference between the azimuth angle and pitch angle is less than the field of view of the monitoring equipment, the simulation accuracy meets the monitoring requirements; otherwise, the simulation accuracy does not meet the standards.

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