TAWS operation stage judgment method suitable for eVTOL

Abstract

The invention provides a TAWS operation stage determination method suitable for eVTOL, and belongs to the technical field of electric vertical take-off and landing aircrafts, and the method specifically comprises the steps: calculating elevation data ASL higher than the sea level and elevation data AGL higher than the ground through an air pressure altitude value, a GNSS elevation value and a radio altitude in combination with a runway / terrain / obstacle database; the vertical speeds of an inertial navigation system I RS, an atmospheric data computer ADC and a global navigation satellite system GNSS are fused to calculate the aircraft climbing rate; the current stage of the aircraft is comprehensively judged by referring to a flight stage state machine, the multi-scene availability of an algorithm is improved, data loss, data calculation offset and the like are included, the redundancy of data is increased, and therefore the operation logic confidence of equipment is improved.

Description

Technical Field

[0001] The present application relates to the field of electric vertical take-off and landing aircraft, and in particular to a TAWS operation phase determination method applicable to eVTOL. Background Art

[0002] The mainstream aircraft equipped with terrain awareness and warning systems are divided into manned helicopters and manned fixed-wing aircraft, and their corresponding product standards are CTSO-C194 and CTSO-C151d. Most products on the market have complete functional supporting functions and mature technical applications. However, with the outbreak of "low-altitude economy" demand such as urban air traffic, sightseeing tourism, cargo transportation, emergency rescue, etc., the demand for TAWS for aircraft such as eVTOL is also increasing. However, due to the special flight profile of eVTOL aircraft, that is, it has both the vertical take-off and landing stage of multi-rotor aircraft and the cruising and level flight stage of fixed-wing aircraft, the international community has not yet released TAWS equipment development standards for eVTOL aircraft.

[0003] The operating characteristic of TAWS is that it automatically activates the corresponding function according to the flight phase of the aircraft, thereby reminding the pilot that the current flight situation has the threat of collision with the ground. The determination of the flight phase is the core logic of TAWS. The flight phase of eVTOL is obviously different from that of helicopters and fixed-wing aircraft, and there is currently no TAWS equipment suitable for eVTOL in the world. If the existing flight phase judgment criteria of helicopters or fixed-wing aircraft are simply used, there will be certain limitations. Specifically, the difference in aircraft configuration and flight profile is easy to cause confusion in enabling logic. In addition, the data transmission of low-altitude sensors is easy to be lost or mutated, which will also cause incorrect judgment of the flight phase. Summary of the invention

[0004] In view of this, the present application provides a TAWS operation phase determination method suitable for eVTOL, which solves the problems in the prior art, improves the multi-scenario availability of the algorithm, including data loss, data calculation offset, etc., increases data redundancy, and thus improves the operating logic confidence of the equipment.

[0005] The present application provides a TAWS operation phase determination method applicable to eVTOL using the following technical solution:

[0006] A TAWS operation phase determination method applicable to eVTOL, comprising:

[0007] Step 1, obtain the onboard avionics sensor data and perform validity processing, calculate and obtain the elevation parameter H0 and the data validity matrix A of the multi-source vertical rate in the radio altitude invalid state;

[0008] Step 2: Calculate the distance between the current position and the runway based on the GNSS coordinates and the runway database position data to determine the positional relationship between the aircraft and the airport. If the aircraft is in the vicinity of the airport, execute step 3; otherwise, execute step 4.

[0009] Step 3: Use the elevation data of the runway database of the Terrain Awareness and Warning System (TAWS) to calculate the height H of the aircraft above the ground when the radio altitude is valid or invalid. AGL ;

[0010] Step 4: Calculate the elevation data when GNSS is valid or invalid based on terrain / obstacle data, RNP, ANP, and satellite number information. Calculate the height H above sea level of the aircraft in the non-runway area by using the time accuracy maintenance characteristics of avionics parameters and combining with pressure altitude compensation. ASL , where terrain / obstacle data is obtained from the Terrain Awareness and Warning System TAWS;

[0011] Step 5, defining the data influencing factor based on the data update cycle, and calculating the aircraft climb rate by weighted fusion of the data validity matrix A of the multi-source vertical rate;

[0012] Step 6: Calculate the altitude data of the aircraft above the ground in all scenarios, and obtain the current TAWS-determined operation phase through the designed flight phase state machine diagram.

[0013] Optionally, the step 1 specifically includes:

[0014] Step 1.1, collect aircraft and flight status data from multi-source avionics. The collected data include latitude and longitude, altitude, ground speed, celestial speed from the global satellite navigation system GNSS, pressure altitude change rate and pressure altitude of the atmospheric data computer ADC, required navigation performance RNP and actual navigation performance ANP of the flight management system FMS, and radio altitude H of the radio altimeter LLRA. ra , the air-ground signal of the flight control system FCS, and the inertial vertical velocity and three-axis acceleration of the inertial navigation system IRS;

[0015] Step 1.2, determine the validity of the radio altitude data based on the periodic refresh status and value of the radio altitude. The criterion for determining the validity of the data is that if any of the following conditions are met, the data is invalid: the altitude value of 5 cycles is not refreshed, the value range exceeds the effective range, if it is determined to be invalid, the altitude parameter H0 = H press , H press Indicates the pressure altitude from ADC;

[0016] Step 1.3, respectively determine the validity of the celestial velocity from GNSS, the pressure altitude change rate from ADC, and the inertial vertical velocity from IRS. The criteria for determining invalid data are: the value has not been refreshed for more than 5 cycles or the value exceeds the effective range. A matrix A with 1 row and 3 columns is used to represent the data validity. The first column represents the celestial velocity, the second column represents the pressure altitude change rate, and the third column represents the inertial vertical velocity. If valid, the corresponding value is set to 1, otherwise it is set to 0.

[0017] Optionally, the step 2 specifically includes:

[0018] According to the GNSS coordinate position, combined with the runway database position data, calculate the distance Dis between the current position and the runway, and select the minimum distance Dis min Determine whether you are currently above the runway. min <k dis When the aircraft is determined to be above the runway, step 3 is executed; otherwise, step 4 is executed, where k dis It is a coefficient whose size is determined by the characteristics of the airport.

[0019] Optionally, the step 3 specifically includes:

[0020] Step 3.1, parse the contents of the runway database, index the elevation position information, and obtain the runway elevation H of the area where the aircraft is located runway , through the radio altitude H ra The calculated height of the aircraft above sea level is H = H ra +H runway ;

[0021] Step 3.2, combined with step 1.2, obtain the height of the aircraft above sea level when the aircraft is in the runway periphery when the radio altitude is valid or invalid, thereby calculating the height H of the aircraft above the ground when the aircraft is in the runway periphery AGL , when radio altitude data is valid H AGL =HH runway , that is, H AGL =H ra , when radio altitude data is invalid H AGL =H0-H runway .

[0022] Optionally, step 4 specifically includes:

[0023] Step 4.1, parse terrain / obstacle data, obtain terrain elevation information, and assemble and process map blocks according to RNP data. The specific method is: when RNP>k rnp , the map blocks are assembled in a 3x3 manner, and the average of the elevation data of the 9 blocks of maps is calculated as the elevation value H in this area terr ; When RNP≤krnp , you need to index the elevation of the map block currently involved as H terr , where k rnp is the coefficient, indicating the specific value, k rnp Dynamically adjust according to the scene;

[0024] Step 4.2, introduce ANP to calculate the navigation error err = ANP-RNP, and combine the number of GNSS satellites to determine the value of the height element parameter H1. The specific conditions are: when the number of satellites is less than k or err is greater than 0, it is considered that the data accuracy of the navigation source GNSS does not meet the requirements. At this time, the radio altitude H is used. ra We get H1=H ra +H terr Otherwise, use GNSS height data H gnss As H1, that is, H1=H gnss , where k comes directly from GNSS;

[0025] Step 4.3, using H press Compensate the elevation data H1 calculated in step 4.2 to obtain the height H of the aircraft above sea level after using the pressure altitude compensation at the current time t ASL , Where τ is the filtering time constant at time t, and S is the Laplace operator.

[0026] Optionally, step 5 specifically includes:

[0027] Step 5.1, calculate the data influence factor matrix Δ derived from the celestial velocity of GNSS, the pressure altitude change rate of ADC, and the inertial vertical velocity of IRS according to the data update cycle; Δ is a matrix of 1 row and 3 columns, the first column represents the celestial velocity, the second column represents the pressure altitude change rate, and the third column represents the inertial vertical velocity. The specific calculation formula is: Where i represents the data source selection - 1, 2, and 3 represent the vertical rates of GNSS, ADC, and IRS transmissions, respectively. freshness It is the data refresh cycle;

[0028] Step 5.2, combined with step 1.3, calculate the weighted coefficient ω = Δ × A that comprehensively considers the data influencing factors and data validity. The calculation formula for the weighted average of the aircraft's final vertical climb rate is as follows:

[0029]

[0030] Among them, V n-GNSS 、V n-ADC 、V n-IRS Represent the vertical rates from GNSS, ADC, and IRS respectively.

[0031] Optionally, step 6 specifically includes:

[0032] Step 6.1, calculate the height H of the aircraft above the ground in the non-runway area according to step 4.3 AGL =H ASL -H terr ; From step 3, we can know that the height of the aircraft above the ground around the runway is H AGL , get the altitude data of the aircraft above the ground in the whole scene;

[0033] Step 6.2, starting from the eVTOL flight profile, combined with the aircraft performance and mission altitude, design the flight phase state machine transition relationship;

[0034] Step 6.3, substitute the parameter reference calculated in steps 5.2 and 6.1 into the flight phase state machine transition relationship in step 6.2 to obtain the operation phase determined by TAWS at the current moment.

[0035] In summary, this application includes the following beneficial technical effects:

[0036] The method of this application is designed to be directional and highly specific. Compared with the traditional TAWS equipment flight phase judgment method, this application fully considers the flight characteristics and scenario categories of eVTOL aircraft, and develops a flight phase conversion mechanism with eVTOL-specific attributes.

[0037] The method of this application integrates data at the data level and has high availability. This application mainly designs algorithms for two important elements of flight phase determination, namely, altitude above the ground and aircraft climb rate, and comprehensively considers factors such as the period, long-term accuracy, and short-term accuracy of avionics data. Finally, the new avionics elements are obtained by fusion calculation. This method can significantly improve the availability of data while accurately calculating the required parameters.

[0038] The method of this application is classified and divided into scenarios, and has excellent execution. This application calculates the required avionics parameters in parallel, and the lag of one path does not affect the remaining operations. The introduction of a pre-designed flight phase state machine module in the final flight phase solution can speed up the execution efficiency of the algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 This is a flow chart of the TAWS operation phase determination method applicable to eVTOL in this application;

[0041] Figure 2 This is the flight phase state machine transition diagram for this application;

[0042] Figure 3 This is the architecture diagram of the flight phase determination algorithm of the terrain perception and warning system for this application. DETAILED DESCRIPTION

[0043] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0044] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0045] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0046] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show the components related to the present application rather than being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed at will, and the component layout may also be more complicated.

[0047] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0048] An embodiment of the present application provides a TAWS operation phase determination method applicable to eVTOL.

[0049] like Figure 1 As shown, a TAWS operation phase determination method applicable to eVTOL includes:

[0050] Step 1: Obtain the onboard avionics sensor data and perform validity processing, and calculate the data validity matrix A of the altitude parameter H0 and the multi-source vertical rate under the invalid radio altitude state.

[0051] Step 2: Calculate the distance between the current position and the runway based on the GNSS coordinates and the runway database position data to determine the positional relationship between the aircraft and the airport. If the aircraft is in the vicinity of the airport, execute step 3; otherwise, execute step 4.

[0052] Step 3: Use the elevation data of the runway database of the Terrain Awareness and Warning System (TAWS) to calculate the height H of the aircraft above the ground when the radio altitude is valid or invalid. AGL .

[0053] Step 4: Calculate the elevation data when GNSS is valid or invalid based on terrain / obstacle data, RNP, ANP, and satellite number information. Calculate the height H above sea level of the aircraft in the non-runway area by using the time accuracy maintenance characteristics of avionics parameters and combining with pressure altitude compensation. ASL , where terrain / obstacle data is obtained from the Terrain Awareness and Warning System TAWS.

[0054] Step 5: Define the data influencing factors based on the data update cycle, and calculate the aircraft climb rate by weighted fusion of the data validity matrix A of the multi-source vertical rate.

[0055] Step 6: Calculate the altitude data of the aircraft above the ground in all scenarios, and obtain the current TAWS-determined operation phase through the designed flight phase state machine diagram.

[0056] This application calculates the elevation data ASL above sea level and the elevation data AGL above the ground through the pressure altitude value, GNSS altitude value, and radio altitude, combined with the runway / terrain / obstacle database; uses the vertical speed of the inertial navigation system IRS, the atmospheric data computer ADC, and the global satellite navigation system GNSS to fuse and calculate the aircraft climb rate; and refers to the flight phase state machine to comprehensively judge the current phase of the aircraft to achieve the goal of improving data availability.

[0057] The operation phase of the TAWS calculation in this application is only provided for use of TAWS internal functions, which is different from the flight phase defined by the aircraft.

[0058] The step 1 specifically includes:

[0059] Step 1.1, collect aircraft and flight status data from multi-source avionics for calculation in subsequent steps. The collected data include latitude and longitude, altitude, ground speed, celestial speed from the global satellite navigation system GNSS, pressure altitude change rate and pressure altitude of the atmospheric data computer ADC, required navigation performance RNP and actual navigation performance ANP of the flight management system FMS, and radio altitude H of the radio altimeter LLRA. ra , the air-ground signal of the flight control system FCS, and the inertial vertical velocity and three-axis acceleration of the inertial navigation system IRS.

[0060] Step 1.2, determine the validity of the radio altitude data based on the periodic refresh status and value of the radio altitude. The criterion for determining the validity of the data is that if any of the following conditions are met, the data is invalid: the altitude value of 5 cycles is not refreshed, the value range exceeds the effective range, if it is determined to be invalid, the altitude parameter H0 = H press , H press Indicates the barometric altitude from ADC; the refresh period and range are defined by the device manufacturer.

[0061] Step 1.3, respectively determine the validity of the celestial velocity from GNSS, the pressure altitude change rate from ADC, and the inertial vertical velocity from IRS. The criteria for determining invalid data are: the value has not been refreshed for more than 5 cycles or the value exceeds the effective range. A matrix A with 1 row and 3 columns is used to represent the data validity. The first column represents the celestial velocity, the second column represents the pressure altitude change rate, and the third column represents the inertial vertical velocity. If valid, the corresponding value is set to 1, otherwise it is set to 0. The refresh cycle and effective range are defined by the equipment manufacturer.

[0062] The step 2 specifically includes: calculating the distance Dis between the current position and the runway according to the GNSS coordinate position and the runway database position data, and selecting the minimum distance Dis min Determine whether you are currently above the runway. min <k dis When the aircraft is determined to be above the runway, step 3 is executed; otherwise, step 4 is executed, where k dis It is a coefficient, and its size is determined by the characteristics of the airport. For example, a smaller value should be used for a general airport with a more general apron.

[0063] The step 3 specifically includes:

[0064] Step 3.1, parse the contents of the runway database, index the elevation position information, and obtain the runway elevation H of the area where the aircraft is located runway , through the radio altitude H ra The calculated height of the aircraft above sea level is H = Hra +H runway .

[0065] Step 3.2, combined with step 1.2, obtain the height of the aircraft above sea level when the aircraft is in the runway periphery when the radio altitude is valid or invalid, so as to calculate the height H of the aircraft above the ground when the aircraft is in the runway periphery AGL , when radio altitude data is valid H AGL =HH runway , that is, H AGL =H ra , when radio altitude data is invalid H AGL =H0-H runway .

[0066] The step 4 specifically includes:

[0067] Step 4.1, parse terrain / obstacle data, obtain terrain elevation information, and assemble and process map blocks according to RNP data to optimize computing resources. The specific method is: when RNP>k rnp , the map blocks are assembled in a 3x3 manner, and the average of the elevation data of the 9 blocks of maps is calculated as the elevation value H in this area terr ; When RNP≤k rnp , you need to index the elevation of the map block currently involved as H terr , where k rnp is the coefficient, indicating the specific value, k rnp Dynamically adjust according to the scene.

[0068] Step 4.2, introduce ANP to calculate the navigation error err = ANP-RNP, and combine the number of GNSS satellites to determine the value of the height element parameter H1. The specific conditions are: when the number of satellites is less than k or err is greater than 0, it is considered that the data accuracy of the navigation source GNSS does not meet the requirements. At this time, the radio altitude H is used. ra We get H1=H ra +H terr Otherwise, use GNSS height data H gnss As H1, that is, H1=H gnss , where k are directly from GNSS.

[0069] Step 4.3, taking into account the pressure height H press The long-term accuracy of H press Compensate the elevation data H1 calculated in step 4.2 to obtain the height H of the aircraft above sea level after using the pressure altitude compensation at the current time t ASL , Where τ is the filtering time constant at time t, and S is the Laplace operator.

[0070] The step 5 specifically includes:

[0071] Step 5.1, calculate the data influence factor matrix Δ derived from the celestial velocity of GNSS, the pressure altitude change rate of ADC, and the inertial vertical velocity of IRS according to the data update cycle; Δ is a matrix of 1 row and 3 columns, the first column represents the celestial velocity, the second column represents the pressure altitude change rate, and the third column represents the inertial vertical velocity. The specific calculation formula is: Where i represents the data source selection - 1, 2, and 3 represent the vertical rates of GNSS, ADC, and IRS transmissions, respectively. freshness It is the data refresh cycle, which is defined by the device manufacturer.

[0072] Step 5.2, combined with step 1.3, calculate the weighted coefficient ω = Δ × A that comprehensively considers the data influencing factors and data validity. The calculation formula for the weighted average of the aircraft's final vertical climb rate is as follows:

[0073] Among them, V n-GNSS 、V n-ADC 、V n-IRS Represent the vertical rates from GNSS, ADC, and IRS respectively.

[0074] The step 6 specifically includes:

[0075] Step 6.1, calculate the height H of the aircraft above the ground when the aircraft is not around the runway according to step 4.3 AGL =H ASL -H terr ; From step 3, we know that the aircraft is at the height H above the ground around the runway AGL , and obtain the altitude data of the aircraft above the ground in the whole scene.

[0076] Step 6.2, starting from the eVTOL flight profile, combined with the aircraft performance and mission altitude, design the flight phase state machine transition relationship, such as Figure 2As shown in FIG. 1 , the specific logic of the flight phase state machine transition diagram is as follows: the aircraft is described as starting from the ground and then returning to the ground after taking off. When the aircraft is in the ground phase, it is determined whether the aircraft has reached the vertical take-off phase based on the air-to-ground signal, radio altitude, climb rate and ground speed; after the aircraft is in the vertical take-off phase, it is determined whether the aircraft has reached the climb transition phase based on the AGL altitude, ground speed and forward acceleration; when the aircraft is in the climb transition phase, it is determined whether the aircraft has reached the climb phase based on the airspeed and climb, and at the same time, it is determined whether the aircraft has reached the landing transition phase based on the ground speed and forward acceleration; when the aircraft is in the climb phase, it is determined whether the aircraft has reached the cruise phase based on the AGL altitude, and at the same time, it is determined whether the aircraft has reached the landing transition phase based on the vertical acceleration and forward acceleration. The forward acceleration is used to determine whether the aircraft has reached the landing transition stage. When the aircraft is in the cruising stage, the AGL altitude is used to determine whether the aircraft has reached the descent stage. When the aircraft is in the descent stage, the AGL altitude is used to determine whether the aircraft has reached the cruising stage, and at the same time, the climb rate and forward acceleration are used to determine whether the aircraft has reached the landing transition stage. When the aircraft is in the landing transition stage, the radio altitude and ground speed are used to determine whether the aircraft has reached the vertical landing stage, and at the same time, the ground speed and forward acceleration are used to determine whether the aircraft has reached the climb transition stage. When the aircraft is in the vertical landing stage, the air-to-ground signal, radio altitude and climb rate are used to determine whether the aircraft has reached the ground stage, where the AGL altitude is the height of the aircraft above the ground.

[0077] Step 6.3, substitute the parameter reference calculated in steps 5.2 and 6.1 into the flight phase state machine transition relationship in step 6.2, and the operation phase determined by TAWS at the current moment can be obtained.

[0078] This application can be used in terrain perception and warning systems carried on manned aircraft platforms such as eVTOL or combined wings with both helicopter and fixed-wing flight profiles to provide protection for the safe flight of aircraft. It can also be used as a reference method for avionics equipment data fusion processing.

[0079] like Figure 3 As shown, the embodiment of the present application also discloses a terrain perception and warning system flight phase determination algorithm system, the system includes a terrain elevation calculation module, an AGL calculation module and a flight phase decision module, the terrain elevation calculation module and the AGL calculation module collect aircraft and flight status data from multi-source avionics, the terrain elevation calculation module performs, runway data processing, terrain data processing, obstacle data processing, the AGL calculation module performs multi-source altitude calculation, multi-source vertical speed error calculation, AGS and vertical speed calculation; the flight phase decision module executes step 6.3 to output the operation phase determined by TAWS at the current moment.

[0080] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A TAWS operation phase determination method applicable to eVTOL, characterized in that: include: Step 1, obtain the onboard avionics sensor data and perform validity processing, calculate and obtain the elevation parameter H0 and the data validity matrix A of the multi-source vertical rate in the radio altitude invalid state; Step 2: Calculate the distance between the current position and the runway based on the GNSS coordinates and the runway database position data to determine the positional relationship between the aircraft and the airport. If the aircraft is in the vicinity of the airport, execute step 3; otherwise, execute step 4. Step 3: Use the elevation data of the runway database of the Terrain Awareness and Warning System (TAWS) to calculate the height H of the aircraft above the ground when the radio altitude is valid or invalid. AGL ; Step 4: Calculate the elevation data when GNSS is valid or invalid based on terrain / obstacle data, RNP, ANP, and satellite number information. Calculate the height H above sea level of the aircraft in the non-runway area by using the time accuracy maintenance characteristics of avionics parameters and combining pressure altitude compensation. ASL , where terrain / obstacle data is obtained from the Terrain Awareness and Warning System TAWS; Step 5, defining the data influencing factor based on the data update cycle, and calculating the aircraft climb rate by weighted fusion of the data validity matrix A of the multi-source vertical rate; Step 6: Calculate the altitude data of the aircraft above the ground in all scenarios, and obtain the current TAWS-determined operation phase through the designed flight phase state machine diagram.

2. The TAWS operation phase determination method applicable to eVTOL according to claim 1, characterized in that: The step 1 specifically includes: Step 1.1, collect aircraft and flight status data from multi-source avionics. The collected data include latitude and longitude, altitude, ground speed, celestial speed from the global satellite navigation system GNSS, pressure altitude change rate and pressure altitude of the atmospheric data computer ADC, required navigation performance RNP and actual navigation performance ANP of the flight management system FMS, and radio altitude H of the radio altimeter LLRA. ra , the air-ground signal of the flight control system FCS, and the inertial vertical velocity and three-axis acceleration of the inertial navigation system IRS; Step 1.2, determine the validity of the radio altitude data based on the periodic refresh status and value of the radio altitude. The criterion for determining the validity of the data is that if any of the following conditions are met, the data is invalid: the altitude value of 5 cycles is not refreshed, the value range exceeds the effective range, if it is determined to be invalid, the altitude parameter H0 = H press , H press Indicates the pressure altitude from ADC; Step 1.3, respectively determine the validity of the celestial velocity from GNSS, the pressure altitude change rate from ADC, and the inertial vertical velocity from IRS. The criteria for determining invalid data are: the value has not been refreshed for more than 5 cycles or the value exceeds the effective range. A matrix A with 1 row and 3 columns is used to represent the data validity. The first column represents the celestial velocity, the second column represents the pressure altitude change rate, and the third column represents the inertial vertical velocity. If valid, the corresponding value is set to 1, otherwise it is set to 0.

3. The TAWS operation phase determination method applicable to eVTOL according to claim 1, characterized in that: The step 2 specifically includes: According to the GNSS coordinate position, combined with the runway database position data, calculate the distance Dis between the current position and the runway, and select the minimum distance Dis min Determine whether you are currently above the runway. min <k dis When the aircraft is determined to be above the runway, step 3 is executed; otherwise, step 4 is executed, where k dis It is a coefficient whose size is determined by the characteristics of the airport.

4. The TAWS operation phase determination method applicable to eVTOL according to claim 2, characterized in that: The step 3 specifically includes: Step 3.1, parse the contents of the runway database, index the elevation position information, and obtain the runway elevation H of the area where the aircraft is located runway , through the radio altitude H ra The calculated height of the aircraft above sea level is H = H ra +H runway ; Step 3.2, combined with step 1.2, obtain the height of the aircraft above sea level when the aircraft is in the runway periphery when the radio altitude is valid or invalid, thereby calculating the height H of the aircraft above the ground when the aircraft is in the runway periphery AGL , when radio altitude data is valid H AGL =HH runway , that is, H AGL =H ra , when radio altitude data is invalid H AGL =H0-H runway .

5. The TAWS operation phase determination method applicable to eVTOL according to claim 1, characterized in that: The step 4 specifically includes: Step 4.1, parse terrain / obstacle data, obtain terrain elevation information, and assemble and process map blocks according to RNP data. The specific method is: when RNP>k rnp , the map blocks are assembled in a 3x3 manner, and the average of the elevation data of the 9 blocks of maps is calculated as the elevation value H in this area terr ; When RNP≤k rnp , you need to index the elevation of the current map block as H terr , where k rnp is the coefficient, indicating the specific value, k rnp Dynamically adjust according to the scene; Step 4.2, introduce ANP to calculate the navigation error err = ANP-RNP, and combine the number of GNSS satellites to determine the value of the height element parameter H1. The specific conditions are: when the number of satellites is less than k or err is greater than 0, it is considered that the data accuracy of the navigation source GNSS does not meet the requirements. At this time, the radio altitude H is used. ra We get H1=H ra +H terr Otherwise, use GNSS height data H gnss As H1, that is, H1=H gnss , where k are directly from GNSS; Step 4.3, using H press Compensate the elevation data H1 calculated in step 4.2 to obtain the height H of the aircraft above sea level after using the pressure altitude compensation at the current time t ASL , Where τ is the filtering time constant at time t, and S is the Laplace operator.

6. The TAWS operation phase determination method applicable to eVTOL according to claim 4, characterized in that: The step 5 specifically includes: Step 5.1, calculate the data influence factor matrix Δ derived from the celestial velocity of GNSS, the pressure altitude change rate of ADC, and the inertial vertical velocity of IRS according to the data update cycle; Δ is a matrix of 1 row and 3 columns, the first column represents the celestial velocity, the second column represents the pressure altitude change rate, and the third column represents the inertial vertical velocity. The specific calculation formula is: Where i represents the data source selection - 1, 2, and 3 represent the vertical rates of GNSS, ADC, and IRS transmissions, respectively. freshness It is the data refresh cycle; Step 5.2, combined with step 1.3, calculate the weighted coefficient ω = Δ × A that comprehensively considers the data influencing factors and data validity. The calculation formula for the weighted average of the aircraft's final vertical climb rate is as follows: Among them, V n-GNSS 、V n-ADC 、V n-IRS Represent the vertical rates from GNSS, ADC, and IRS respectively.

7. The TAWS operation phase determination method applicable to eVTOL according to claim 6, characterized in that: The step 6 specifically includes: Step 6.1, calculate the height H of the aircraft above the ground in the non-runway area according to step 4.3 AGL =H ASL -H terr ; From step 3, we can know that the height of the aircraft above the ground around the runway is H AGL , get the altitude data of the aircraft above the ground in the whole scene; Step 6.2, starting from the eVTOL flight profile, combined with the aircraft performance and mission altitude, design the flight phase state machine transition relationship; Step 6.3, substitute the parameter reference calculated in steps 5.2 and 6.1 into the flight phase state machine transition relationship in step 6.2 to obtain the operation phase determined by TAWS at the current moment.

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