Aircraft flight time control method suitable for low-altitude economy

Abstract

The invention discloses an aircraft flight time control method suitable for low-altitude economy, and relates to the technical field of aircraft control, and the method comprises the steps: S1, data acquisition, S2, atmospheric environment prediction and ground speed calculation, S3, flight time and scheme judgment, S4, flight time adjustment scheme calculation, and S5, flight process monitoring and adjustment. According to the method, the air route of the aircraft is automatically planned and adjusted through the computer, a traditional manual adjustment mode depending on a driver is replaced, the computer can automatically calculate the optimal adjustment scheme within the required precision through the method, the flight air route meets the adjustment requirement, the problems of inaccuracy, instability and the like caused by human factors are reduced, and meanwhile the adjustment accuracy is improved. Under the scene that multiple aircrafts share the air route, the flight time of each aircraft can be controlled more accurately, potential safety hazards such as meeting in the air are avoided, and the overall flight efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft control, and in particular relates to a method for controlling the flight time of an aircraft suitable for low-altitude economy. Background Art

[0002] As the country continues to promote the development of the low-altitude economy, various unmanned aerial vehicles have begun to be widely used in production and life. With the continuous increase in the number of aircraft, how to ensure the safe flight of aircraft while improving flight efficiency is a new issue currently faced. Among them, the scenario of multiple aircraft sharing routes often occurs. For example, if two aircraft want to land at the same airport, they must use the same path to merge into the landing route. In order to avoid the aircraft meeting in the air, they must enter the landing route one after another. That is, the two aircraft must arrive at the starting point of the landing route in sequence. At this time, one or two of the aircraft may need to adjust the flight time to cooperate with each other.

[0003] Under the current technical means, to complete this operation, the aircraft pilot needs to manually adjust the flight route and flight speed based on experience, and constantly check and correct during the flight to meet the flight time requirements. Since the flight time is manually adjusted, the accuracy, rationality and safety of the adjustment cannot be guaranteed. There are many limitations and it cannot meet the needs of safe and efficient flight. Therefore, the following solutions are proposed to address the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for controlling the flight time of an aircraft suitable for low-altitude economy. The computer can automatically calculate the best adjustment plan so that the flight route meets the adjustment requirements, thereby solving the problem that the accuracy, rationality and safety of the adjustment cannot be guaranteed when the pilot of the existing aircraft manually adjusts the flight time.

[0005] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] The present invention is a method for controlling the flight time of an aircraft suitable for low-altitude economy, and the control method comprises the following steps:

[0007] Step S1, obtaining data: obtaining the current flight route, position, speed, weather data of the aircraft and the flight time to be adjusted;

[0008] Step S2, atmospheric environment prediction and ground speed calculation: predict atmospheric environment parameters and calculate the ground speed of the aircraft in combination with the corrected airspeed;

[0009] Step S3, flight time and plan judgment: calculate the flight time of the original route according to the acquired data, and compare it with the actual demand to determine whether to adjust the flight time;

[0010] Step S4, calculation of the adjustment plan for the flight time: calculating a new adjustment plan according to the result of the plan judgment and the algorithm for reducing or increasing the flight time;

[0011] Step S5, flight process monitoring and adjustment: monitor the flight speed in real time, decide whether to recalculate the turning point based on the deviation between the actual ground speed and the theoretical ground speed, monitor the meeting point coordinates and the remaining flight time during the final flight, and alarm to remind you to adjust the speed if the deviation between the actual ground speed and the theoretical ground speed exceeds the threshold.

[0012] Preferably, the calculation of the adjustment scheme of the flight time in step S4 is divided into two cases: the calculation of the adjustment scheme of reducing the flight time and the calculation of the adjustment scheme of increasing the flight time;

[0013] The calculation method of the adjustment scheme for reducing flight time is:

[0014] Flight speed calculation: Take the current flight speed as the default speed, consider the atmospheric environment and convert it into ground speed to calculate the straight-line distance from the current point to the target point Minimum flight time ,when More time than necessary , increase flight speed, recalculate ,until Less than or equal to , or the speed reaches the maximum speed allowed for safe flight of the aircraft ,When the maximum speed is reached and still not satisfied, the algorithm exits;

[0015] Flight distance calculation: determine the minimum distance from the current point to the target point and maximum distance ,in, The straight-line distance from the current position to the target point , is the sum of the distances of the remaining portion of the current route;

[0016] calculate and The arithmetic mean of , calculated according to specific flight requirements Corresponding flight time ;

[0017] Calculate the deviation ,when If it is less than the threshold, the new flight distance is determined and the algorithm ends; otherwise, according to and Update the size relationship and , return to continue calculation , through iteration Reach the compliance value;

[0018] Turning point calculation: Calculate the turning point from the current segment of the aircraft. Assuming that the aircraft has flown a certain distance in the current segment Arrive at the turning point, then turn and fly straight to the target point, after a distance After reaching the destination, , The straight-line distance from the current position to the target point Construct a triangle and calculate it according to the triangle cosine theorem , the formula is:

[0019] , where The angle between the line connecting the current position and the target point and the line connecting the current position and the turning point;

[0020] When sought If it is not greater than the length of the current segment, the turning point is on the current segment; otherwise, the aircraft is ordered to fly along the original segment to the next segment, and the turning point is calculated in the next segment until the second to last segment.

[0021] Preferably, the calculation of the adjustment scheme for increasing the flight time specifically includes:

[0022] Set the aircraft speed to the minimum speed and calculate the time it takes to reach the target location along the original route at the minimum speed. Is the latest time met? , and the time it takes to fly to the destination in a straight line Is the flight time shorter than required? ;

[0023] When both conditions are met, the turning point is calculated using the method of calculating the turning point when reducing the flight time, and the aircraft is allowed to fly along the new route; when both conditions are not met, the speed is increased and the calculation continues until the target speed is found or the speed is increased to the current actual speed and still cannot meet the requirements, the algorithm exits.

[0024] Preferably, the specific calculation method of the atmospheric environment prediction in step S2, atmospheric environment prediction and ground speed calculation is:

[0025] Temperature estimation: Low-altitude aircraft flying in the troposphere, use the formula Calculate the temperature, where is the flight altitude, is the international standard atmospheric sea level temperature, To correct the temperature;

[0026] Air density estimation: In the troposphere, according to the formula Calculate the air density, where Obtained by the temperature estimation algorithm, , is the acceleration due to gravity, is the rate of change of standard atmospheric temperature with altitude, R is the real gas constant of air, is the air density at sea level;

[0027] Air pressure estimation: The relationship between air pressure and altitude in the troposphere is given by the formula Indicates that, is the standard atmospheric sea level pressure, Obtained by the temperature estimation algorithm, , is the acceleration due to gravity, is the rate of change of standard atmospheric temperature with altitude, is the real gas constant of air;

[0028] Wind speed estimation: using spline fitting algorithm, using five different heights The actual wind speed value under is taken as the node, where and They are the lower and upper limits of wind speed respectively. In the geodetic coordinate system, the wind speed is decomposed into and In both directions, the wind speed at each node is recorded as and , the position of the aircraft at any time and The wind speeds in the two directions are and Indicates that the wind speed in the direction parallel to the aircraft's flight path is calculated and vertical wind speed , define a cubic polynomial:

[0029] ,

[0030] In the formula, is the spline function coefficient of wind speed at each height, is the flight altitude, ,when hour, ,according to Determine the interval , let the polynomial coefficients satisfy the wind speed value at the node equal to the true wind speed, and the polynomial at Internal continuity, polynomial first-order derivative in Internal continuity, polynomial second-order derivatives in Internal continuity, natural spline boundary conditions are used for boundary conditions, and the second-order derivative of wind speed at the node is obtained by solving the linear equation system. , and then find the spline function coefficients of wind speed at each height:

[0031] , , , ;

[0032] In the formula, The second derivative of wind speed is at the node The value at , The second derivative of wind speed is at the node The value at and They represent different height nodes and adjacent nodes used to calculate wind speed. and Respectively, in the node and nodes The wind speed value at and Direction solving.

[0033] Preferably, the ground speed calculation method in step S2, atmospheric environment prediction and ground speed calculation is:

[0034] Aircraft true speed Corrected airspeed By the formula:

[0035] calculate,

[0036] In the formula, , is the isentropic expansion coefficient of air, is the air density at sea level, is the standard atmospheric sea level pressure, is the air density at standard atmospheric sea level, and P is the theoretically calculated air pressure value at the current position of the aircraft;

[0037] After obtaining the true airspeed, use the ground speed formula Calculate ground speed, where is the pitch angle of the aircraft, and They respectively represent the wind speed in the direction parallel to the aircraft's flight path and the wind speed in the direction perpendicular to it.

[0038] Preferably, the specific method for monitoring the flight speed in the step S5, flight process monitoring and adjustment, is:

[0039] Receive the real-time airspeed and weather information of the aircraft, use the real weather information to update the algorithm data, calculate the real ground speed, and judge the real ground speed Theoretical ground speed The deviation is calculated and the turning point is recalculated.

[0040] Preferably, the specific calculation method of the meeting point coordinates in step S5, flight process monitoring and adjustment, is:

[0041] When the aircraft reaches the turning point and turns to enter the final route, due to the speed deviation, it does not directly reach the target point but merges into the route after the target point. The heading angle of the deviation route is , the heading angle of the route after reaching the target point is , take the target point coordinates as , take the current position coordinate point as , the equation of the straight line after reaching the target point is , the straight line equation of the deviation route is , combine the two straight line equations, let , solve for the coordinates of the entry point for:

[0042] .

[0043] Preferably, the specific calculation method of the remaining flight time in the step S5, flight process monitoring and adjustment, is:

[0044] Calculate the distance from the meeting point to the target point ,when When it is less than the threshold, the aircraft heading is within the acceptable range, and the remaining range is calculated. , calculate the remaining flight time based on the current actual ground speed ,when When the deviation from the required arrival time is less than the threshold, the current flight speed of the aircraft is within an acceptable range. When the deviation is greater than the threshold, the algorithm alarm reminds the pilot to adjust the aircraft speed to the theoretical value calculated by the algorithm.

[0045] The present invention has the following beneficial effects:

[0046] 1. The present invention uses a computer to automatically plan and adjust the aircraft route, replacing the traditional manual adjustment method by the pilot. The computer can automatically calculate the best adjustment plan within the required accuracy through this method, so that the flight route meets the adjustment requirements, reducing the inaccuracy and instability caused by human factors. At the same time, in the scenario where multiple aircraft share the route, the flight time of each aircraft can be controlled more accurately to avoid safety hazards such as encounters in the air, thereby improving the overall efficiency of the flight.

[0047] 2. The present invention can monitor relevant data in real time through a computer during flight, and predict the atmospheric environment through this method, so that the aircraft can better adapt to changes in the atmospheric environment, ensure that the flight trajectory meets expectations, and compare the actual ground speed with the theoretical ground speed in real time. When the deviation exceeds the threshold, the turning point can be recalculated. In the monitoring of the final flight route, the coordinates of the meeting point and the remaining flight time can be calculated, and the deviation can be judged and processed, so as to timely discover and correct abnormal situations during the flight process and ensure that the aircraft arrives at the target point safely.

[0048] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0050] Figure 1 It is a schematic diagram of the steps of the present invention;

[0051] Figure 2 is a flow chart of the present invention;

[0052] Figure 3 A schematic diagram of the flight route of an aircraft of the present invention;

[0053] Figure 4 is a flow chart of the flight time reduction algorithm of the present invention;

[0054] Figure 5 A flow chart of the flight speed calculation of the present invention;

[0055] Figure 6 A flow chart of the flight distance calculation of the present invention;

[0056] Figure 7 A schematic diagram of a flight route of an aircraft in the turning point calculation process of the present invention;

[0057] Figure 8 A schematic diagram of the second flight route of the aircraft in the turning point calculation process of the present invention;

[0058] Fig. 9 A flow chart of an algorithm for increasing flight time of the present invention;

[0059] Fig.10 is a flow chart of the flight speed monitoring of the present invention;

[0060] Fig.11A schematic diagram of the flight route of the aircraft in calculating the merging point coordinates of the present invention;

[0061] Fig.12 A schematic diagram of the flight path angle of the aircraft in calculating the meeting point coordinates of the present invention;

[0062] Fig.13 The flowchart of the present invention is to calculate the remaining flight time. DETAILED DESCRIPTION

[0063] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] See also Figure 1-13 As shown, the present invention is a method for controlling the flight time of an aircraft suitable for low-altitude economy, and the control method comprises the following steps:

[0065] Step S1, obtaining data: obtaining the current flight route, position, speed, weather data of the aircraft and the flight time to be adjusted;

[0066] Step S2, atmospheric environment prediction and ground speed calculation: predict atmospheric environment parameters and calculate the ground speed of the aircraft in combination with the corrected airspeed;

[0067] Step S3, flight time and plan judgment: calculate the flight time of the original route according to the acquired data, and compare it with the actual demand to determine whether to adjust the flight time;

[0068] Step S4, calculation of the adjustment plan for the flight time: calculating a new adjustment plan according to the result of the plan judgment and the algorithm for reducing or increasing the flight time;

[0069] Step S5, flight process monitoring and adjustment: monitor the flight speed in real time, decide whether to recalculate the turning point based on the deviation between the actual ground speed and the theoretical ground speed, monitor the meeting point coordinates and the remaining flight time during the final flight, and alarm to remind you to adjust the speed if the deviation between the actual ground speed and the theoretical ground speed exceeds the threshold.

[0070] Step S4, the calculation of the adjustment scheme of the flight time is divided into two cases: the calculation of the adjustment scheme of reducing the flight time and the calculation of the adjustment scheme of increasing the flight time;

[0071] The calculation method for the adjustment plan to reduce flight time is:

[0072] Flight speed calculation: Take the current flight speed as the default speed, consider the atmospheric environment and convert it into ground speed to calculate the straight-line distance from the current point to the target point Minimum flight time ,when More time than necessary , increase flight speed, recalculate ,until Less than or equal to , or the speed reaches the maximum speed allowed for safe flight of the aircraft ,When the maximum speed is reached and still not satisfied, the algorithm exits;

[0073] Flight distance calculation: determine the minimum distance from the current point to the target point and maximum distance ,in, The straight-line distance from the current position to the target point , is the sum of the distances of the remaining portion of the current route;

[0074] calculate and The arithmetic mean of , calculated according to specific flight requirements Corresponding flight time ;

[0075] Calculate the deviation ,when If it is less than the threshold, the new flight distance is determined and the algorithm ends; otherwise, according to and Update the size relationship and , return to continue calculation , through iteration Reach the compliance value;

[0076] Turning point calculation: Calculate the turning point from the current segment of the aircraft. Assuming that the aircraft has flown a certain distance in the current segment Arrive at the turning point, then turn and fly straight to the target point, after a distance After reaching the destination, , The straight-line distance from the current position to the target point Construct a triangle and calculate it according to the triangle cosine theorem , the formula is:

[0077] , where The angle between the line connecting the current position and the target point and the line connecting the current position and the turning point;

[0078] When sought If it is not greater than the length of the current segment, the turning point is on the current segment; otherwise, the aircraft is ordered to fly along the original segment to the next segment, and the turning point is calculated in the next segment until the second to last segment.

[0079] The calculation of the adjustment plan to increase flight time specifically includes:

[0080] Set the aircraft speed to the minimum speed and calculate the time it takes to reach the target location along the original route at the minimum speed. Is the latest time met? , and the time it takes to fly to the destination in a straight line Is the flight time shorter than required? ;

[0081] When both conditions are met, the turning point is calculated using the method of calculating the turning point when reducing the flight time, and the aircraft is allowed to fly along the new route; when both conditions are not met, the speed is increased and the calculation continues until the target speed is found or the speed is increased to the current actual speed and still cannot meet the requirements, the algorithm exits.

[0082] The specific calculation method of atmospheric environment prediction in step S2, atmospheric environment prediction and ground speed calculation is:

[0083] Temperature estimation: Low-altitude aircraft flying in the troposphere, use the formula Calculate the temperature, where is the flight altitude, is the international standard atmospheric sea level temperature, To correct the temperature;

[0084] Air density estimation: In the troposphere, according to the formula Calculate the air density, where Obtained by the temperature estimation algorithm, , is the acceleration due to gravity, is the rate of change of standard atmospheric temperature with altitude, is the real gas constant for air, is the air density at sea level;

[0085] Air pressure estimation: The relationship between air pressure and altitude in the troposphere is given by the formula Indicates that, is the standard atmospheric sea level pressure, Obtained by the temperature estimation algorithm, , is the acceleration due to gravity, is the rate of change of standard atmospheric temperature with altitude, is the real gas constant of air;

[0086] Wind speed estimation: using spline fitting algorithm, using five different heights The actual wind speed value under is taken as the node, where and They are the lower and upper limits of wind speed respectively. In the geodetic coordinate system, the wind speed is decomposed into and In both directions, the wind speed at each node is recorded as and , the position of the aircraft at any time and The wind speeds in the two directions are and Indicates that the wind speed in the direction parallel to the aircraft's flight path is calculated and vertical wind speed , define a cubic polynomial:

[0087] , where is the spline function coefficient of wind speed at each height, is the flight altitude, ,when hour, ,according to Determine the interval , let the polynomial coefficients satisfy the wind speed value at the node equal to the true wind speed, and the polynomial at Internal continuity, polynomial first-order derivative in Internal continuity, polynomial second-order derivatives in Internal continuity, natural spline boundary conditions are used for boundary conditions, and the second-order derivative of wind speed at the node is obtained by solving the linear equation system. , and then find the spline function coefficients of wind speed at each height:

[0088] , , ;

[0089] In the formula, The second derivative of wind speed is at the node The value at , The second derivative of wind speed is at the node The value at They represent different height nodes and adjacent nodes used to calculate wind speed. and Respectively, in the node and nodes The wind speed value at Direction solving.

[0090] Step S2: The ground speed calculation method in atmospheric environment prediction and ground speed calculation is:

[0091] Aircraft true speed Corrected airspeed By the formula: calculate,

[0092] In the formula, , is the isentropic expansion coefficient of air, is the air density at sea level, is the standard atmospheric sea level pressure, is the standard atmospheric sea level air density, The air pressure value theoretically calculated for the current position of the aircraft;

[0093] After obtaining the true airspeed, use the ground speed formula Calculate ground speed, where is the pitch angle of the aircraft, They respectively represent the wind speed in the direction parallel to the aircraft's flight path and the wind speed in the direction perpendicular to it.

[0094] Step S5: The specific method for monitoring the flight speed during flight process monitoring and adjustment is as follows:

[0095] Receive the real-time airspeed and weather information of the aircraft, use the real weather information to update the algorithm data, calculate the real ground speed, and judge the real ground speed Theoretical ground speed The deviation is calculated and the turning point is recalculated.

[0096] Step S5: The specific calculation method of the meeting point coordinates in the flight process monitoring and adjustment is:

[0097] When the aircraft reaches the turning point and turns to enter the final route, due to the speed deviation, it does not directly reach the target point but merges into the route after the target point. The heading angle of the deviation route is , the heading angle of the route after reaching the target point is , take the target point coordinates as , take the current position coordinate point as , the equation of the straight line after reaching the target point is , the straight line equation of the deviation route is , combine the two straight line equations, let , solve for the coordinates of the entry point for:

[0098] .

[0099] Step S5: The specific calculation method of the remaining flight time in the flight process monitoring and adjustment is:

[0100] Calculate the distance from the meeting point to the target point ,when When it is less than the threshold, the aircraft heading is within the acceptable range, and the remaining range is calculated. , calculate the remaining flight time based on the current actual ground speed ,when When the deviation from the required arrival time is less than the threshold, the current flight speed of the aircraft is within an acceptable range. When the deviation is greater than the threshold, the algorithm alarm reminds the pilot to adjust the aircraft speed to the theoretical value calculated by the algorithm.

[0101] A specific application of this embodiment is: When an aircraft is flying along a predetermined route, it may encounter a situation where it needs to reach a certain point on the route on time. In this case, the route needs to be adjusted. The present invention provides a method for automatically planning an adjustment plan using a computer and monitoring the execution of the plan in real time, so that the aircraft can reach the target point on time.

[0102] refer to Figure 3 , Figure 3 It is a schematic diagram of the flight route of an aircraft. The aircraft is currently at point A on the route and plans to fly along points B, C, and D to the target point E. If the time to fly to point E needs to be adjusted at this time, this method will calculate a turning point T on the route. When the aircraft flies to point T, the original flight plan is terminated and then it flies directly to point E, so that it can reach the target point at the required time. After calculating the best solution, the computer will automatically monitor the flight process through the real-time flight information obtained by the aircraft. When the actual flight parameters of the aircraft deviate too much from the calculated values ​​due to changes in the atmospheric environment (such as changes in wind force and wind direction), the algorithm will recalculate the appropriate turning point according to the actual situation. In addition, when the aircraft turns and flies directly to the target point, the algorithm will calculate in real time whether the flight speed, direction and other data meet the requirements. If not, an alarm will be issued.

[0103] This method divides the operation of adjusting the flight time of the aircraft into two situations: reducing the flight time and increasing the flight time. When the flight time needs to be reduced, the adjustment plan will be directly calculated. When the flight time needs to be increased, this method will first convert the demand for increasing the flight time into the demand for reducing the flight time by reducing the flight speed of the aircraft, and then calculate the adjustment plan. The specific steps are as follows: Step S1, obtain data: clarify the flight path of the aircraft and determine the current position of the aircraft in the path (such as Figure 3 A in the figure), and the path planning along points B, C, and D to the target point E, obtain the current flight speed of the aircraft (corrected airspeed ), meteorological data (including wind speed, temperature, air pressure, etc.) and flight time that needs to be adjusted;

[0104] Step S2: Atmospheric environment prediction and ground speed calculation:

[0105] Atmospheric environment prediction: When calculating the flight time of an aircraft, the ground speed of the aircraft is required. In addition to the aircraft's air speed, the ground speed of the aircraft is also affected by environmental factors such as wind speed and temperature. Therefore, when calculating the ground speed of an aircraft, it is necessary to predict and estimate parameters such as wind speed and temperature.

[0106] Temperature estimation:

[0107] The present invention is aimed at low-altitude aircraft flying in the troposphere, so its temperature is calculated using the following formula:

[0108]

[0109] in:

[0110] is the altitude at which the aircraft is flying;

[0111] is the international standard atmospheric sea level temperature, ;

[0112] is the corrected temperature, which is calculated by measuring the temperature at a certain local altitude;

[0113] Air density estimation:

[0114] In the troposphere, the relationship between air density and altitude is expressed by the following formula:

[0115]

[0116] in:

[0117] is a function of height, obtained by the algorithm given in the previous section,

[0118] is the sea surface temperature, ;

[0119] is the acceleration due to gravity, ;

[0120] is the rate of change of standard atmospheric temperature with altitude, ;

[0121] is the real gas constant for air, ;

[0122] is the air density at sea level, which is calculated as: , where is the standard atmosphere sea level air density, ;

[0123] Air pressure estimation:

[0124] The relationship between air pressure and altitude in the troposphere is expressed by the following formula:

[0125] ,

[0126] In the formula, is the standard atmospheric sea level pressure, ;

[0127] Wind speed estimation:

[0128] At different heights in the troposphere, the wind speed (including size and direction) will be very different and cannot be simply calculated using a linear formula. Here is a spline fitting algorithm to estimate the wind speed at different heights;

[0129] The algorithm uses five different heights The actual wind speed value under is used as the node for calculating the spline function, where are the lower and upper limit heights of the wind speed to be calculated. Since the wind speed is a vector, the wind speed is decomposed into and In two directions, the wind speed at each node is recorded as: ;

[0130] The wind speed at the aircraft's location at any time is expressed as The wind speed in the direction parallel to the aircraft's flight path is and the wind speed perpendicular to the aircraft's flight path They are:

[0131] ,

[0132] ;

[0133] Then, define a cubic polynomial to fit any height Wind speed at The formula is consistent in direction):

[0134] ,

[0135] In the formula, ,and:

[0136] when ;

[0137] when ;

[0138] when ;

[0139] when ;

[0140] Let the coefficients of the polynomial satisfy the following conditions:

[0141] when hour,

[0142] The values ​​of the polynomial are connected in Continued;

[0143] The first-order derivative of a polynomial is Internal continuity;

[0144] The second derivative of a polynomial is Internal continuity;

[0145] Assume that the value of the second-order derivative of wind speed at the node is ,Right now:

[0146]

[0147] The edge conditions use natural spline edge conditions, let: ;

[0148] According to the continuity and boundary conditions of the polynomial, we can get The linear equations must be satisfied:

[0149]

[0150] All the equations in this system These are all known values ​​and can be solved by computer. ;

[0151] It should be noted that the wind speed Two directions need to be solved separately;

[0152] Solved Then, substitute the coefficient formula below to obtain the spline function coefficient of wind speed at each height:

[0153] , ;

[0154] Aircraft ground speed calculation:

[0155] The ground speed of the aircraft is calculated from the true airspeed of the aircraft and the wind speed. Corrected airspeed given by the aircraft It is obtained by the following formula:

[0156]

[0157] In the formula, ;

[0158] and is the isentropic expansion coefficient of air, ;

[0159] After obtaining the true airspeed, calculate the ground speed using the following formula: :

[0160] ;

[0161] In the formula, is the pitch angle of the aircraft, which is used to calculate the horizontal component of airspeed;

[0162] Step S3, flight time and plan judgment: according to the acquired flight route and speed data, the flight time along the original route to the target point E is calculated, and it is judged whether the flight time needs to be adjusted. If adjustment is required, it is further judged whether to reduce or increase the flight time;

[0163] Step S4: Calculation of the adjustment plan for flight time:

[0164] When the operation to adjust the aircraft's flight time is to reduce the flight time, the specific calculation method is as follows:

[0165] The flight time reduction algorithm consists of three parts: flight speed calculation, flight distance calculation and turning point calculation;

[0166] The flight speed calculation is responsible for calculating the reasonable flight speed of the aircraft, the flight distance calculation is responsible for calculating the flight distance at a reasonable speed so that the flight time meets the requirements, and the turning point calculation is responsible for calculating a point on the route to ensure that the time it takes for the aircraft to reach the target point after flying to the target point meets the requirements. The three parts are executed in sequence to complete the work, such as Figure 4 ;

[0167] Flight speed calculation:

[0168] The default flight speed uses the current flight speed, but there is a shortest distance for the aircraft to fly from the current point to the target point, which is the straight-line distance between the two points. If the aircraft uses the default speed, the flight distance Time Still longer than necessary , it means that the default speed cannot meet the time requirement. In this case, you need to increase the flight speed by one unit (default 1 m / s) and then calculate Does it meet the requirements? If not, continue to calculate until the appropriate speed is found. If the speed increases to the maximum speed allowed for safe flight of the aircraft, If the appropriate speed is still not found, it means that the required time cannot be achieved and the algorithm exits;

[0169] The current speed here is the corrected airspeed of the aircraft , while the algorithm uses ground speed to calculate flight time, the conversion from corrected airspeed to ground speed needs to consider the influence of atmospheric environmental conditions. This method gives a prediction algorithm for the atmospheric environment in the above steps;

[0170] The process of flight speed calculation can be referred to Figure 5 It should be noted that the flight speed of the aircraft is not constant, but will be adjusted according to various restrictions (such as terrain, weather, etc.). The flight speed mentioned in the algorithm is the maximum speed that can be achieved during the flight. In addition, the calculation method of the flight time also needs to be adjusted according to the specific flight requirements (constant speed flight or accelerated or decelerated flight, etc.), rather than a fixed calculation method;

[0171] Flight distance calculation:

[0172] Because the flight route is not determined when calculating the new flight distance, the closed form formula cannot be used to calculate the flight distance. This method uses an iterative method to calculate the flight distance.

[0173] First determine the minimum distance from the current point to the target point and maximum distance , because the new flight time is required to be shorter than the original flight time, so is the sum of the distances of the remaining parts of the current route, is the straight-line distance from the current position of the aircraft to the target point ;

[0174] When the initial and Then start calculating the distance of the new route The specific algorithm flow is as follows: Figure 6 ;

[0175] The new distance is calculated by and The arithmetic mean of is:

[0176]

[0177] Flight time The calculation method is not fixed and needs to be determined according to specific flight requirements;

[0178] Since the flight parameters of aircraft obtained through instruments, radars, etc. are subject to error, and the flight process of real aircraft cannot be controlled with high precision, Compliance When the two are equal, we cannot simply measure whether they are equal, but we must have an allowable error range. Here we use a deviation degree To express the deviation between the calculated result and the required value, the calculation formula is:

[0179]

[0180] when When it is less than a threshold, it is considered It meets the requirements. Here, 0.025 is selected as the threshold. When It meets the requirements, that is, a suitable new flight distance is found, and the algorithm ends.

[0181] when If the requirements are not met, the program will update the flight distance , and then continue to iterate, the updated logic is:

[0182] if but:

[0183]

[0184] if but:

[0185]

[0186] After the update is completed, the program will return to continue calculation , so that through continuous iteration, Continuously approaching the required value from both sides, so that Getting closer and closer to the right length, and finally reaching The accuracy requirements;

[0187] Turning point calculation:

[0188] After obtaining the distance the aircraft needs to fly, the turning point can be calculated to make the aircraft's flight distance consistent with the calculated distance. The calculation of the turning point starts from the current segment of the aircraft. Assuming that the aircraft flies a distance of Arrive at the turning point, then turn and fly straight to the target point, passing the distance After reaching the target point, , The straight-line distance from the current position of the aircraft to the target point Form a triangle , where the angle The angle of Figure 7 As shown in the middle triangle;

[0189] According to the triangle cosine theorem:

[0190]

[0191] And there are:

[0192]

[0193] You can get:

[0194]

[0195] If you obtain If the length L of the current segment AB is not greater than the current segment, the turning point T is on the current segment. Otherwise, the aircraft is ordered to fly along the original segment to the next segment BC and calculate the turning point in the next segment. Figure 8 As shown in the middle triangle;

[0196] The calculation principle remains the same, but the distance and angle need to be updated:

[0197]

[0198] Then, find the distance of the new turning point The formula is:

[0199]

[0200] Similarly, if the turning point is not on this segment, the calculation will continue on the next segment, and so on until the second to last segment;

[0201] The turning point will not appear in the last segment, because if it appears in the last segment, it means that there will be a broken line connecting the two end points of the segment on the last segment, and the length of the broken line is shorter than the length of the segment, which violates the axiom that the straight line is the shortest distance between two points, so it cannot exist;

[0202] When the operation to adjust the aircraft's flight time is to increase the flight time, the specific algorithm is:

[0203] The above is the calculation method of the turning point when the flight time needs to be reduced. On the contrary, if the flight time needs to be increased, this situation can be converted into a situation of reducing the flight time, and then the calculation is performed as follows:

[0204] If the flight time needs to be reduced, it means that the current speed of the aircraft is faster than the required speed. In this case, the speed of the aircraft can be set to the minimum speed allowed (usually higher than the minimum speed the aircraft can fly), and then the time to reach the target location along the original route at this speed can be calculated. Whether the latest allowed time is met (Because there may be other aircraft behind this aircraft that also need to fly to the same point, there is a lower limit on the time it takes to reach the target point, and it cannot be delayed at will). At the same time, if this speed is used to fly in a straight line to the target location, is the time it takes shorter than the required flight time? Travel time If both of the above conditions are met, then at this speed, the turning point can be calculated using the method described in the previous section, and the aircraft can fly along the new route to reach the destination at the required time.

[0205] If the set speed cannot meet the above requirements, the speed will be increased by one unit (default 1 m / s) and the calculation will continue until a suitable speed is found. If the speed is increased to the current actual speed and still cannot find a suitable speed, the given arrival time is unreasonable and the algorithm will exit directly. For the specific process, refer to Fig. 9 ;

[0206] Step S5: Flight process monitoring and adjustment:

[0207] Because the ground speed of the aircraft during flight is affected by the environment and the real environment often changes, its actual flight speed may deviate from the estimated speed and needs to be constantly checked. When the deviation is large, the turning point of the aircraft needs to be recalculated according to the actual speed;

[0208] After the aircraft uses the algorithm to calculate the turning point, during the flight, the algorithm will continuously compare the aircraft's real-time speed value with the theoretical value used in the calculation. Theoretical ground speed The difference is greater than the threshold (here set to ),Right now When the ground speed error is too large, the turning point needs to be recalculated. The specific process is as follows: Fig.10 As shown;

[0209] Final flight route monitoring: When the aircraft reaches the turning point and turns, it enters the newly planned route, which is also the last route before reaching the destination. During this route, the algorithm will calculate the remaining distance and arrival time in real time. If it is found that the current speed or route deviates from the original route by more than the threshold, a warning will be issued.

[0210] Calculate the coordinates of the rendezvous point: Due to the deviation of the aircraft's flight speed, it may not reach the target point directly, but merge into the route after the target point before or after the target point. Fig.11 As shown;

[0211] T is the target point, TB is the route the aircraft will fly after reaching point T. According to calculations, the aircraft should reach the target point along route AT, but due to flight deviation, the aircraft will merge into the reverse extension line of TB at point C. In this case, this method will calculate the coordinates of the convergence point C in real time, and calculate the remaining route length and flight time. If the deviation from the original planned time is within the allowable range, the current state will be maintained and the flight will not be changed. Because the speed of the aircraft is not easy to control accurately due to various factors, it is a reasonable choice to maintain the original flight state within the allowable range.

[0212] like Fig.12 Calculate the coordinates of point C:

[0213] First, let the heading angle of line AC be , the heading angle of the line BT is , then, take the coordinates of point T on BT as , then the equation of the line BT is:

[0214] ;

[0215] Take the coordinates of point A on AC as , then the equation of line AC is:

[0216] ;

[0217] Combine the two straight line equations and set: , solve for the coordinates of the meeting point C for:

[0218] ;

[0219] Calculate the remaining flight time:

[0220] After obtaining the coordinates of the confluence point, calculate the distance from the confluence point to the target point :

[0221]

[0222] if Less than a threshold (here set to ), it means the heading of the aircraft is within the acceptable range.

[0223] Then calculate the remaining distance :

[0224] ;

[0225] After getting the range, calculate the remaining flight time according to the current actual ground speed:

[0226] ;

[0227] if The deviation from the required arrival time is less than the threshold (here set to ) then the current flight speed of the aircraft is within an acceptable range;

[0228] If the aircraft flies at the current speed and the deviation is greater than the threshold, the algorithm alarm will remind the pilot to adjust the aircraft speed to the theoretical value calculated by the algorithm. The specific process of the detection algorithm is as follows: Fig.13 shown.

[0229] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0230] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for controlling the flight time of an aircraft suitable for low-altitude economy, characterized in that: The control method comprises the following steps: Step S1, obtaining data: obtaining the current flight route, position, speed, weather data of the aircraft and the flight time to be adjusted; Step S2, atmospheric environment prediction and ground speed calculation: predict atmospheric environment parameters and calculate the ground speed of the aircraft in combination with the corrected airspeed; Step S3, flight time and plan judgment: calculate the flight time of the original route according to the acquired data, and compare it with the actual demand to determine whether to adjust the flight time; Step S4, calculation of the adjustment plan for the flight time: calculating a new adjustment plan according to the result of the plan judgment and the algorithm for reducing or increasing the flight time; Step S5, flight process monitoring and adjustment: monitor the flight speed in real time, decide whether to recalculate the turning point based on the deviation between the actual ground speed and the theoretical ground speed, monitor the meeting point coordinates and the remaining flight time during the final flight, and alarm to remind you to adjust the speed if the deviation between the actual ground speed and the theoretical ground speed exceeds the threshold.

2. The method for controlling the flight time of an aircraft suitable for low-altitude economy according to claim 1, characterized in that: The step S4, the calculation of the adjustment scheme of the flight time is divided into two situations: the calculation of the adjustment scheme of reducing the flight time and the calculation of the adjustment scheme of increasing the flight time; The calculation method of the adjustment scheme for reducing flight time is: Flight speed calculation: Take the current flight speed as the default speed, consider the atmospheric environment and convert it into ground speed to calculate the straight-line distance from the current point to the target point Minimum flight time ,when More time than necessary , increase flight speed, recalculate ,until Less than or equal to , or the speed reaches the maximum speed allowed for safe flight of the aircraft ,When the maximum speed is reached and still not satisfied, the algorithm exits; Flight distance calculation: determine the minimum distance from the current point to the target point and maximum distance ,in, The straight-line distance from the current position to the target point , is the sum of the distances of the remaining portion of the current route; calculate and The arithmetic mean of , calculated according to specific flight requirements Corresponding flight time ; Calculate the deviation ,when If it is less than the threshold, the new flight distance is determined and the algorithm ends; otherwise, according to and Update the size relationship and , return to continue calculation , through iteration Reach the compliance value; Turning point calculation: Calculate the turning point from the current segment of the aircraft. Assuming that the aircraft has flown a certain distance in the current segment Arrive at the turning point, then turn and fly straight to the target point, after a distance After reaching the destination, , The straight-line distance from the current position to the target point Construct a triangle and calculate it according to the triangle cosine theorem , the formula is: , where The angle between the line connecting the current position and the target point and the line connecting the current position and the turning point; When sought If it is not greater than the length of the current segment, the turning point is on the current segment; otherwise, the aircraft is ordered to fly along the original segment to the next segment, and the turning point is calculated in the next segment until the second to last segment.

3. The method for controlling the flight time of an aircraft suitable for low-altitude economy according to claim 2, characterized in that: The calculation of the adjustment plan for increasing the flight time specifically includes: Set the aircraft speed to the minimum speed and calculate the time it takes to reach the target location along the original route at the minimum speed. Is the latest time met? , and the time it takes to fly to the destination in a straight line Is the flight time shorter than required? ; When both conditions are met, the turning point is calculated using the method of calculating the turning point when reducing the flight time, and the aircraft is allowed to fly along the new route; when both conditions are not met, the speed is increased and the calculation continues until the target speed is found or the speed is increased to the current actual speed and still cannot meet the requirements, the algorithm exits.

4. The method for controlling the flight time of an aircraft suitable for low-altitude economy according to claim 1, characterized in that: The specific calculation method of atmospheric environment prediction in step S2, atmospheric environment prediction and ground speed calculation is: Temperature estimation: Low-altitude aircraft flying in the troposphere, use the formula Calculate the temperature, where h is the flight altitude, is the international standard atmospheric sea level temperature, To correct the temperature; Air density estimation: In the troposphere, according to the formula Calculate the air density, where Obtained by the temperature estimation algorithm, , g is the acceleration due to gravity, is the rate of change of standard atmospheric temperature with altitude, R is the real gas constant of air, is the air density at sea level; Air pressure estimation: The relationship between air pressure and altitude in the troposphere is given by the formula Indicates that, is the standard atmospheric sea level pressure, Obtained by the temperature estimation algorithm, , g is the acceleration due to gravity, is the rate of change of standard atmospheric temperature with altitude, R is the real gas constant of air; Wind speed estimation: using spline fitting algorithm, using five different heights The actual wind speed value under is taken as the node, where and are the lower and upper limits of wind speed respectively. In the geodetic coordinate system, the wind speed is decomposed into two directions, x and y. The wind speed at each node is recorded as and , the wind speeds in the x and y directions at the aircraft's position at any time are expressed as and Indicates that the wind speed in the direction parallel to the aircraft's flight path is calculated and vertical wind speed , define a cubic polynomial: , In the formula, is the spline function coefficient of wind speed at each height, h is the flight altitude, ,when hour, , determine i according to the interval where h is located, and let the polynomial coefficients satisfy the wind speed value at the node equal to the actual wind speed and the polynomial at Internal continuity, polynomial first-order derivative in Internal continuity, polynomial second-order derivatives in Internal continuity, natural spline boundary conditions are used for boundary conditions, and the second-order derivative of wind speed at the node is obtained by solving the linear equation system. , and then find the spline function coefficients of wind speed at each height:

5. In the formula, represents the value of the second-order derivative of wind speed at node i, , The second derivative of wind speed is at the node The value at and They represent different height nodes and adjacent nodes used to calculate wind speed. and Respectively represent the nodes at node i and node The wind speed value at the location; the wind speed needs to be solved in the x and y directions respectively.

6. The method for controlling the flight time of an aircraft suitable for low-altitude economy according to claim 1, characterized in that: The ground speed calculation method in step S2, atmospheric environment prediction and ground speed calculation is: Aircraft true speed Corrected airspeed By the formula: calculate, In the formula, , is the isentropic expansion coefficient of air, is the air density at sea level, is the standard atmospheric sea level pressure, is the air density at standard atmospheric sea level, and P is the theoretically calculated air pressure value at the current position of the aircraft; After obtaining the true airspeed, use the ground speed formula Calculate ground speed, where is the pitch angle of the aircraft, and They respectively represent the wind speed in the direction parallel to the aircraft's flight path and the wind speed in the direction perpendicular to it.

7. The method for controlling the flight time of an aircraft suitable for low-altitude economy according to claim 1, characterized in that: The specific method of monitoring the flight speed in the step S5, flight process monitoring and adjustment, is as follows: Receive the real-time airspeed and weather information of the aircraft, use the real weather information to update the algorithm data, calculate the real ground speed, and judge the real ground speed Theoretical ground speed The deviation is calculated and the turning point is recalculated.

8. The method for controlling the flight time of an aircraft suitable for low-altitude economy according to claim 6, characterized in that: The specific calculation method of the meeting point coordinates in step S5, flight process monitoring and adjustment, is: When the aircraft reaches the turning point and turns to enter the final route, due to the speed deviation, it does not directly reach the target point but merges into the route after the target point. The heading angle of the deviation route is , the heading angle of the route after reaching the target point is , take the target point coordinates as , take the current position coordinate point as , the equation of the straight line after reaching the target point is , the straight line equation of the deviation route is , combine the two straight line equations, let , solve for the coordinates of the confluence point for: 。 9. The method for controlling the flight time of an aircraft suitable for low-altitude economy according to claim 7, characterized in that: The specific calculation method of the remaining flight time in step S5, flight process monitoring and adjustment, is: Calculate the distance from the meeting point to the target point ,when When it is less than the threshold, the aircraft heading is within the acceptable range, and the remaining range is calculated. , calculate the remaining flight time based on the current actual ground speed ,when When the deviation from the required arrival time is less than the threshold, the current flight speed of the aircraft is within an acceptable range. When the deviation is greater than the threshold, the algorithm alarm reminds the pilot to adjust the aircraft speed to the theoretical value calculated by the algorithm.

Images