Low-altitude air route planning method and system considering rotor failure backup descent safety

Abstract

The present application relates to the technical field of low-altitude operation safety of power-lifting aircraft, and particularly relates to a low-altitude air route planning method and system considering backup landing safety after rotor failure, which comprises the following steps: determining available low-altitude flight airspace, screening backup landing site construction areas in the available low-altitude flight airspace that meet the technical constraints of backup landing site construction and determining backup landing site positions; planning an initial air route and determining backup landing safety evaluation node information; calculating battery discharge power after rotor failure of the power-lifting aircraft at any position; taking total power consumption of the low-altitude air route as a target function, and planning a backup landing safety route of the power-lifting aircraft in a controllable flight state after rotor failure to meet the backup landing safety of the power-lifting aircraft after rotor failure. The present application evaluates the backup landing safety of the power-lifting aircraft after rotor failure at any position, makes up the missing backup landing safety analysis after rotor failure in planning a low-altitude air route, and ensures the safety of the planned low-altitude air route.

Description

Technical Field

[0001] This invention relates to the field of low-altitude operation safety technology for powered aircraft, and in particular to a low-altitude route planning method and system that takes into account the safety of emergency landing after rotor failure. Background Technology

[0002] Urban air mobility (UAM) can effectively alleviate urban ground traffic congestion. Powered-lift aircraft are one of the main transport vehicles for UAM, and the rational planning of low-altitude routes is crucial to ensuring operational safety and improving operational efficiency. Planning low-altitude routes that prioritize the safety of emergency landings in the event of rotor failure for powered-lift aircraft and aim to save on power consumption is of great significance for fully realizing the value of UAM.

[0003] Low-altitude airspace contains numerous restricted areas, placing high demands on the performance and reliability of powered aircraft and the planning of low-altitude routes. In planning low-altitude routes, it is crucial not only to consider bypassing these restricted areas, but also to assess the performance of powered aircraft in the event of rotor failure and the safety of emergency landings following rotor failure.

[0004] Existing research, when considering the safety of alternate landings after rotor failure in powered-lift aircraft, fails to provide clear criteria for alternate landing site selection, rendering the locations of alternate landing sites lacking rationality. Furthermore, existing research, such as Chinese invention patent application CN121113096A ("Method, Apparatus, Equipment and Storage Medium for Generating Low-Altitude Routes") and application CN120973000A ("A Dynamic Environment Adaptive Low-Altitude Route Planning Method and System"), while considering obstacle conditions and route endurance requirements, does not provide a detailed analysis of battery performance changes after rotor failure in powered-lift aircraft, lacking consideration for alternate landing safety. The absence of analysis of battery discharge power changes and alternate landing safety considerations after rotor failure will result in a lack of contingency plans for powered-lift aircraft after rotor failure, compromising the safety of planned low-altitude routes. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in related technologies. To this end, this invention provides a low-altitude route planning method and system that considers the safety of alternate landings after rotor failure, evaluates the safety of alternate landings after rotor failure at any position of a powered aircraft, fills the gap in the analysis of alternate landing safety after rotor failure in the planning of low-altitude routes, and ensures the safety of the planned low-altitude routes.

[0006] This invention provides a low-altitude route planning method that considers alternate landing safety after rotor failure, comprising:

[0007] S1: Extract the location information of low-altitude obstacles, delineate the obstacle area in the low-altitude navigation airspace based on the location information of low-altitude obstacles and the navigation deviation, and determine the available low-altitude navigation airspace based on the obstacle area.

[0008] S2: Screen available low-altitude airspace for alternative landing site construction areas that meet the technical constraints and transfer convenience, and determine the location of the alternative landing site based on the construction area.

[0009] S3: Plan the initial route within the available low-altitude airspace, and deploy landing safety assessment nodes at equal intervals along the centerline of the initial route within the alternate landing site;

[0010] S4: Calculate the percentage of remaining battery charge at each diversion safety assessment node based on the remaining battery charge of the powered aircraft at the start of cruise, the battery discharge power during the vertical takeoff and climb phases, and calculate the latitude and longitude coordinates of each diversion safety assessment node based on the geographic information system.

[0011] S5: Establish the optimal control model and the whole-aircraft stress model after rotor failure at any position of the powered lift aircraft. Apply optimal control theory to solve the optimal control model and combine it with the whole-aircraft stress model to obtain the emergency discharge power of the battery after rotor failure at any position of the powered lift aircraft.

[0012] S6: Calculate the controllable flight time after rotor failure based on the emergency discharge power of the battery after rotor failure at any position of the powered aircraft and the percentage of remaining battery charge at the alternate landing safety assessment node. By comparing the controllable flight time with the time required to reach the nearest alternate landing site, assess whether the powered aircraft meets the alternate landing safety requirements under controllable flight conditions after rotor failure.

[0013] S7: Using the total power consumption of low-altitude routes as the objective function and the safety of diversion in controllable flight after rotor failure as the constraint, the latitude and longitude coordinates of diversion safety assessment nodes are adjusted for routes that do not meet the diversion safety requirements, and the initial routes are replanned to obtain low-altitude routes that meet the diversion safety requirements after rotor failure.

[0014] Furthermore, step S1 includes:

[0015] S11: Extract obstacle location information from public data and geographic information service platforms. The obstacle location information includes the location of immovable cultural relics protection units and the location of restricted airspace within the low-altitude airspace.

[0016] S12: Delineate the obstacle area based on the location information of obstacles in the low-altitude airspace and the flight deviation. The obstacle area also includes a buffer area. The buffer area has a horizontal dimension equal to the width of the airway and a vertical dimension equal to the height of the airway.

[0017] S13: Obstacle areas, no-fly zones and surrounding warning airspace are removed from the existing low-altitude airspace to obtain usable low-altitude airspace.

[0018] Furthermore, the technical constraints for alternate landing site construction include constraints on the impact area and the height of obstacles;

[0019] The landing methods are divided into ballistic landing and uncontrolled sliding landing. The maximum value of the impact area of ​​ballistic landing and the impact area of ​​uncontrolled sliding landing is taken as the landing impact area constraint.

[0020] The usable area within the alternate landing site construction area is greater than the maximum value among the standards for the impact area of ​​a ballistic impact, the impact area of ​​an uncontrolled sliding impact, and the construction area of ​​the alternate landing site.

[0021] Obstacle height constraints stipulate that the height of obstacles around the alternate landing site must be lower than the obstacle height limit standard of the alternate landing site.

[0022] Furthermore, step S3, which involves planning the initial route within the available low-altitude airspace, includes:

[0023] A straight path is constructed between the starting point and the ending point. If the straight path is not within the available low-altitude airspace, the initial route is adjusted to a path that sequentially connects the starting point, the ending point, and the boundary points of the available airspace.

[0024] Furthermore, the calculation of the remaining battery capacity percentage for each alternate landing safety assessment node in step S4 includes:

[0025] S41: Both vertical takeoff and climb are considered as uniformly accelerated motions with the same acceleration.

[0026] S42: Calculate the time required for vertical takeoff and climb based on the aircraft's height above the ground and climb acceleration at the end of the vertical takeoff phase;

[0027] S43: The power consumption during the vertical takeoff and climb phases is obtained by integrating the battery discharge power over time. The upper limits of integration are the time required for vertical takeoff and the time required for climb, respectively.

[0028] S44: By subtracting the power consumed during the vertical takeoff and climb phases from the battery capacity, the remaining power of the power-lift aircraft's battery is obtained when cruise begins.

[0029] S45: The percentage of remaining battery charge at the alternate landing safety assessment node is obtained by subtracting the consumed charge from the remaining battery charge of the aircraft when cruise begins and dividing by the battery capacity.

[0030] Furthermore, the altitude of the alternate landing safety assessment node is a positive integer multiple of the route altitude, and is within the altitude range of the lower limit and upper limit of the available low-altitude airspace.

[0031] Furthermore, step S5 includes:

[0032] S51: Establish the optimal control model for a powered aircraft after rotor failure at any position;

[0033] S52: Apply optimal control theory to solve the optimal control model and obtain the horizontal and vertical thrust under optimal control after rotor failure at any position of a powered lift aircraft.

[0034] S53: Based on the aerodynamic layout and power system characteristics of powered lift aircraft, establish a whole-aircraft force model after rotor failure at any position of powered lift aircraft, and solve for time-related parameters.

[0035] S54: Calculate the horizontal and vertical rotor speeds based on time-related parameters and the horizontal and vertical thrust under optimal control after rotor failure at any position of the powered aircraft.

[0036] S55: Solve for the horizontal rotor torque and vertical rotor torque of a powered lift aircraft after rotor failure at any position, based on the horizontal rotor speed and vertical rotor speed.

[0037] S56: Calculate the discharge current of the battery at the horizontal rotor and the discharge current at the vertical rotor after the failure of the horizontal rotor of the powered lift aircraft, based on the horizontal rotor torque and the vertical rotor torque after the failure of the horizontal rotor of the powered lift aircraft.

[0038] S57: Calculate the emergency discharge power of the battery after the failure of the rotor at any position of the powered lift aircraft, based on the battery discharge voltage, the discharge current of the battery at the horizontal rotor and the discharge current at the vertical rotor after the failure of the rotor at any position of the powered lift aircraft.

[0039] Furthermore, the state variables of the optimal control model after rotor failure at any position of the powered aircraft include the horizontal and vertical speeds and the remaining battery percentage after rotor failure at any position of the powered aircraft.

[0040] The control variable is the thrust distribution command for the remaining rotors;

[0041] The goal is to minimize the total power consumption from the moment of failure to the moment controllable flight is achieved.

[0042] Furthermore, emergency landing safety after rotor failure includes:

[0043] The safe power reserve that can be used for emergency landing flights is obtained by subtracting the remaining battery power percentage at the alternate landing safety assessment node from the preset alarm power percentage and then multiplying it by the total battery capacity.

[0044] Divide the safe power reserve by the battery discharge power after the rotor fails at any position of the powered aircraft to obtain the controllable flight time after the rotor fails at any position of the powered aircraft.

[0045] If the controllable flight time after rotor failure at any position of a powered aircraft is greater than the time required to reach the nearest alternate landing site, then the powered aircraft can safely make an alternate landing while in a controllable flight state after rotor failure.

[0046] This invention also provides a low-altitude route planning system that considers emergency landing safety after rotor failure, for executing the aforementioned low-altitude route planning method that considers emergency landing safety after rotor failure, comprising:

[0047] The extraction module extracts the location information of low-altitude obstacles, delineates obstacle areas in the low-altitude navigation airspace based on the location information of low-altitude obstacles and navigation deviations, and determines the available low-altitude navigation airspace based on the obstacle areas.

[0048] The filtering module filters out alternate landing site construction areas within available low-altitude airspace that meet the technical constraints of alternate landing site construction and the convenience of transfer, and determines the location of the alternate landing site based on the alternate landing site construction area.

[0049] The planning module plans the initial route within the available low-altitude airspace and deploys landing safety assessment nodes at equal intervals along the centerline of the initial route within the alternate landing site.

[0050] The parameter calculation module calculates the percentage of remaining battery power at each diversion safety assessment node based on the remaining battery power of the powered aircraft at the start of cruise, the battery discharge power during the vertical takeoff and climb phases, and calculates the latitude and longitude coordinates of each diversion safety assessment node based on the geographic information system.

[0051] The power calculation module establishes the optimal control model and the whole-aircraft stress model after rotor failure at any position of the powered lift aircraft. It applies optimal control theory to solve the optimal control model and combines the whole-aircraft stress model to obtain the emergency discharge power of the battery after rotor failure at any position of the powered lift aircraft.

[0052] The evaluation module calculates the controllable flight time after rotor failure based on the emergency discharge power of the battery after rotor failure at any position of the powered aircraft and the percentage of remaining battery charge at the alternate landing safety evaluation node. By comparing the controllable flight time with the time required to reach the nearest alternate landing site, the module evaluates whether the powered aircraft meets the alternate landing safety requirements under controllable flight conditions after rotor failure.

[0053] The adjustment module uses the total power consumption of the low-altitude route as the objective function and the safety of the alternate landing in a controllable flight state after the rotor failure of the aircraft as the constraint. It adjusts the latitude and longitude coordinates of the alternate landing safety assessment nodes of the route that does not meet the alternate landing safety requirements and replans the initial route to obtain a low-altitude route that meets the alternate landing safety requirements after rotor failure.

[0054] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0055] This invention ensures the safety and rationality of alternate landing sites by acquiring low-altitude airspace geographic information data and calculating the impact area of ​​a crash, thereby improving the basis for alternate landing site selection.

[0056] This invention takes into account the constraints of transfer convenience at alternate airports, ensuring that the walking time from the alternate airport to surrounding transportation hubs does not exceed 10 minutes, thus guaranteeing that passengers can choose other means to reach their destination after an emergency landing by a powered aircraft.

[0057] This invention systematically analyzes the change in battery discharge power after rotor failure at any position in a powered aircraft. The obtained battery discharge power after rotor failure has an error of no more than 0.5W compared with the actual observed value, which makes up for the lack of analysis on the change in battery discharge power after rotor failure in existing research when planning low-altitude routes.

[0058] This invention systematically evaluates the safety of alternate landings after rotor failure at any position in a powered aircraft, filling the gap in the analysis of alternate landing safety after rotor failure in planned low-altitude routes, and ensuring the safety of planned low-altitude routes.

[0059] This invention enables a comprehensive analysis of the low-altitude flight environment and is only applicable to planning low-altitude routes that ensure safe alternate landings in the event of rotor failure in powered aircraft.

[0060] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0061] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0062] Figure 1This is a flowchart illustrating a low-altitude route planning method that considers the safety of emergency landings after rotor failure, provided by the present invention.

[0063] Figure 2 This is a schematic diagram of the rotor speed change over time after the failure of the two horizontal rotors of a powered aircraft, calculated according to an embodiment of the present invention, and a schematic diagram of the battery discharge performance.

[0064] Figure 3 This is a low-altitude flight path map planned according to an embodiment of the present invention to ensure safe diversion after rotor failure of a powered aircraft.

[0065] Figure 4 This is a schematic diagram of a low-altitude route planning system that takes into account the safety of emergency landing after rotor failure, provided by the present invention.

[0066] Figure label:

[0067] 101. Extraction module; 102. Filtering module; 103. Planning module; 104. Parameter calculation module; 105. Power calculation module; 106. Evaluation module; 107. Adjustment module. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but cannot be used to limit the scope of this invention.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] The following is combined Figures 1 to 4 This invention describes a low-altitude flight path planning method and system that takes into account the safety of emergency landings after rotor failure.

[0071] like Figure 1As shown, a low-altitude route planning method considering emergency landing safety after rotor failure includes:

[0072] S1: Extract the location information of low-altitude obstacles, delineate the obstacle area in the low-altitude navigation airspace based on the location information of low-altitude obstacles and the navigation deviation, and determine the available low-altitude navigation airspace based on the obstacle area.

[0073] S11: Extract obstacle location information from public data and geographic information service platforms. The obstacle location information includes the location of immovable cultural relics protection units and the location of restricted airspace within the low-altitude airspace.

[0074] In some specific embodiments of the present invention, a total of 46 locations of immovable cultural relics protection units and airspace restriction zones within low-altitude airspace are extracted. See [link to specific locations]. Figure 3 .

[0075] S12: Delineate the obstacle zone based on the location information of obstacles in the low-altitude airspace and the flight deviation. The obstacle zone also includes a buffer zone.

[0076] Protected airspace with a radius of 2 km should be established at locations such as immovable cultural relics sites, chemical plants, and nuclear power plants; protected airspace with a radius of 5 km should be established at airports and no-fly zones; to prevent encroachment on the obstructed airspace of airports, immovable cultural relics sites, chemical plants, and nuclear power plants due to navigation errors, flight technique errors, or other factors during low-altitude flight routes.

[0077] The obstacle area should also include a buffer zone, the buffer zone being sized in the horizontal direction. equal to the width of the flight path Dimensions in the vertical direction equal to the altitude of the flight path route width with route altitude Navigation errors in the horizontal direction can be detected. Vertical navigation error Flight technical error (FTE) and communication delay Control center response delay Pilot or flight control system reaction delay maneuver delay The calculation expression is:

[0078]

[0079]

[0080] in, To increase the radius of the aircraft's circumsphere, To power and increase the aircraft's cruising speed;

[0081] Navigation error is the input parameter, while flight technique error can be determined based on the maximum vertical speed that the human body can withstand. The maximum vertical acceleration that the human body can withstand. Passenger reaction time to changes in acceleration The calculation expression is:

[0082]

[0083] In some specific embodiments of the present invention, navigation error in the vertical direction The horizontal navigation error is set at 2 m. Set to 6.2 m, communication delay Set to 0.06 s; Control center response delay Set to 5 seconds; pilot or flight control system reaction delay Set to 1 second; maneuver delay Set to 0.05s; the maximum vertical speed that the human body can withstand. Set to 10 m / s²; the maximum vertical acceleration that the human body can withstand. Set to 5m / s 2 Passenger reaction time to changes in acceleration If we set it to 2s, then the width of the low-altitude airway is 615.25 m; the altitude of the low-altitude airway is 30.5 m.

[0084] S13: Obstacle areas, no-fly zones and surrounding warning airspace are removed from the existing low-altitude airspace to obtain usable low-altitude airspace.

[0085] S2: Screen available low-altitude airspace for alternative landing site construction areas that meet the technical constraints and transfer convenience, and determine the location of the alternative landing site based on the construction area.

[0086] Technical constraints on alternate landing site construction include constraints on the impact area and the height of obstacles.

[0087] The landing methods are divided into ballistic landing and uncontrolled sliding landing. The maximum value of the impact area of ​​ballistic landing and the impact area of ​​uncontrolled sliding landing is taken as the landing impact area constraint.

[0088] The calculation formula is as follows: The usable area within the alternate landing site construction area is greater than the maximum value among the ballistic impact area, the uncontrolled sliding impact area, and the alternate landing site construction area standards.

[0089]

[0090]

[0091] in, This refers to the area affected by the ballistic impact. Let be the radius of the circumscribed sphere of the aircraft. The average width of the human body The area affected by the out-of-control skidding and crash. The average human height It is a glide slope.

[0092] In some specific embodiments of the present invention, the circumscribing radius of the aircraft It is 7.25 m, the average width of a human body Set at 0.3 m, average human height Set to 1.7 m, glide angle Set at 7.125°, and set the standard for the construction area of ​​the alternate landing site. Set to 10,512.5 m 2 Area affected by aircraft ballistic impact It is 205.84 m 2 The area affected by the out-of-control skidding and crash is [missing information]. It is 786.61 m 2 The available area within the alternate landing site construction area is... >10,512.5 m 2 .

[0093] Obstacle height constraints stipulate that the height of obstacles around the alternate landing site must be lower than the obstacle height limit standard of the alternate landing site.

[0094] In some specific embodiments of the present invention, the obstacle height limit standard is set to 30 m. If any obstacle in the alternate landing site construction area exceeds the obstacle height limit standard of 30 m, the alternate landing site construction area should be deleted.

[0095] The construction area of ​​an alternate airport that meets the technical constraints for alternate airport construction should also meet the requirements for convenient transfer between alternate airports; the walking time from the alternate airport construction area to the surrounding transportation hubs should be included, and the walking time should not exceed the maximum acceptable walking time obtained from the survey.

[0096] In some specific embodiments of the present invention, the maximum acceptable walking time t st The time t is 10 minutes, which is the walking time t from the alternate landing site construction area to the surrounding transportation hub. w The time should not exceed 10 minutes. Ultimately, an alternate landing site will be established in an area that simultaneously meets the technical constraints of the Xuzhou alternate landing site construction and the convenience of transfers.

[0097] S3: Plan the initial route within the available low-altitude airspace, and deploy landing safety assessment nodes at equal intervals along the centerline of the initial route within the alternate landing site;

[0098] A straight path is constructed between the starting point and the ending point. If the straight path is not within the available low-altitude airspace, the initial route is adjusted to a broken path that connects the starting point, the ending point, and the boundary points of the available airspace in sequence.

[0099] Alternate landing safety assessment nodes are deployed at equal intervals along the flight path centerline, with the interval set to 1 / x of the flight length, where x is the number of alternate landing safety assessment nodes. The core parameter of each alternate landing safety assessment node is the remaining battery percentage.

[0100] S4: Calculate the percentage of remaining battery charge at each diversion safety assessment node based on the remaining battery charge of the powered aircraft at the start of cruise, the battery discharge power during the vertical takeoff and climb phases; calculate the latitude and longitude coordinates of each diversion safety assessment node based on the geographic information system.

[0101] The calculation of the remaining battery percentage includes:

[0102] S41: The vertical takeoff and climb processes of powered aircraft are both considered as uniformly accelerated motions with the same acceleration.

[0103] S42: Calculate the time required for vertical takeoff and climb based on the aircraft's height above ground and climb acceleration at the end of the vertical takeoff phase. The calculation expression is:

[0104]

[0105]

[0106] in, The time required for vertical takeoff. To increase the aircraft's altitude above the ground at the end of the vertical takeoff phase. For climbing acceleration, Time required for ascent, To power and increase the aircraft's cruising speed.

[0107] The expression for calculating the acceleration due to climb is:

[0108]

[0109] in, To increase the aircraft's altitude from the ground during the climb phase, The ascent angle.

[0110] S43: The power consumption during the vertical takeoff and climb phases is obtained by integrating the battery discharge power over time. The upper limits of integration are the time required for vertical takeoff and the time required for climb, respectively.

[0111] S44: By subtracting the power consumed during the vertical takeoff and climb phases from the battery capacity, the remaining power of the power-lift aircraft's battery is obtained when cruise begins.

[0112] S45: The percentage of remaining battery charge at the alternate landing safety assessment node is obtained by subtracting the consumed charge from the remaining battery charge of the aircraft when cruise begins and dividing by the battery capacity.

[0113] Longitude of the alternate landing safety assessment node ,latitude The coordinates are obtained by mapping using a geographic information system.

[0114] In some specific embodiments of the present invention, there are six takeoff and landing sites, named A, B, C, D, E, and F respectively; a total of 15 initial flight routes are planned. Each low-altitude flight route is divided into 5 equal parts according to the flight distance, and a backup landing safety assessment node is determined at every 1 / 5 of the flight distance, i.e., x=5. In this embodiment, there are a total of 60 backup landing safety assessment nodes on the 15 initial flight routes. Some backup landing safety assessment nodes share a single backup landing safety assessment node. The locations of the safety assessment nodes are shown below. Figure 3 .

[0115] The altitude of the alternate landing safety assessment node should be a positive integer multiple of the route altitude, in order to reserve vertical maneuvering space for potential failures; the altitude in the spatial coordinates of the alternate landing safety assessment node must be within the altitude range between the lower limit and the upper limit of the available low-altitude airspace.

[0116] In some specific embodiments of the present invention, the upper limit of the usable low-altitude airspace is 1000 m, and the lower limit is 300 m. The low-altitude route altitude is 30.58 m, and the altitude of the alternate landing safety assessment node should be 10 times the route altitude, so the altitude of each alternate landing safety assessment node on the initial route is 305.8 m.

[0117] S5: Establish the optimal control model and the whole-aircraft stress model after rotor failure at any position of the powered lift aircraft. Apply optimal control theory to solve the optimal control model and combine it with the whole-aircraft stress model to obtain the emergency discharge power of the battery after rotor failure at any position of the powered lift aircraft.

[0118] The calculation expressions for the battery discharge current during normal cruise in normal flight conditions and the battery discharge current during normal vertical takeoff of a powered-lift aircraft are as follows:

[0119]

[0120]

[0121] in, This refers to the discharge current of the battery when powering the aircraft during normal cruise. This refers to the equivalent voltage of the battery when it powers the aircraft during normal cruise. This refers to the equivalent current of the battery when powering the aircraft during normal cruise. The internal resistance is the electronically adjustable; To increase the number of horizontal rotors in an aircraft, and to increase the battery discharge voltage during normal flight. , To increase the battery discharge current during normal vertical takeoff of the aircraft, This refers to the equivalent voltage of the motor from the battery during the normal vertical takeoff of the aircraft. The battery provides the equivalent current to the motor during normal vertical takeoff of the aircraft. To increase the number of vertical rotors in an aircraft;

[0122] , , , The calculation expression is:

[0123]

[0124]

[0125]

[0126]

[0127] in, To increase the rotor torque during aircraft cruise, This refers to the nominal no-load kV value of the motor. This refers to the nominal no-load voltage of the motor. This refers to the motor's nominal no-load current. The internal resistance of the motor, For horizontal rotor speed, To enable the aircraft to take off vertically under power, This refers to the vertical rotor speed;

[0128] and The calculation expression is:

[0129]

[0130]

[0131] in, This is the rotor torque coefficient. air density, This is the rotor diameter.

[0132] and The solution can be obtained by analyzing the forces acting on a powered aircraft during normal vertical takeoff and cruise:

[0133] The calculation expression for a powered aircraft where only the horizontal rotor rotates during cruise is:

[0134]

[0135] in, To improve the drag factor of fixed-wing aircraft, To increase the fixed-wing area of ​​aircraft, This is the rotor thrust coefficient. The rotor diameter;

[0136] If a powered aircraft has a tiltrotor, during normal vertical takeoff, the tiltrotor converts into a vertical rotor and maintains the same rotor speed as the other vertical rotors. Then there is

[0137]

[0138] in, To increase the weight of the aircraft, It is the acceleration due to gravity. For climbing acceleration, It is a time variable;

[0139] If a powered lift aircraft does not have a tiltrotor, and only the vertical rotor rotates during normal vertical takeoff, then:

[0140]

[0141] If the powered aircraft has a tiltrotor, during vertical takeoff, the tiltrotor, which was originally a horizontal rotor, and the vertical rotor together provide the lift required for vertical takeoff; this must be considered simultaneously in the calculation. and If the powered aircraft does not have a tiltrotor, then only the vertical rotor provides the lift required for vertical takeoff. To improve calculation speed and reduce computational complexity, the original drag formula is modified. Simplified to .

[0142] The formula for calculating the battery discharge power during the climbing phase is:

[0143]

[0144] in, This refers to the battery discharge power during the climb phase. To enhance the battery discharge power during vertical takeoff of aircraft, The time required for vertical takeoff The ascent angle.

[0145] In some specific embodiments of the present invention, the parameters of the powered lift aircraft are shown in Table 1, which specifies the height of the powered lift aircraft above the ground at the end of the vertical takeoff phase. Set at 30 m, the aircraft's height above the ground is boosted by power at the end of the climb phase. That is, the initial cruising altitude is 305.8 m, and the climb angle is... The angle is 7.125°. Air density. It is 1.21 kg / m³; the gravitational acceleration g is 10 m / s². 2 Substituting the above parameters, we obtain the battery discharge power during normal cruise of the powered aircraft. It is 39.92 kWh.

[0146] When all horizontal rotors of the powered aircraft are tiltrotors, the calculated battery discharge power during normal vertical takeoff is... The calculation expression is:

[0147]

[0148] Where t is the time variable;

[0149] Power increases the battery discharge power during the aircraft's climb phase The calculation expression is:

[0150]

[0151] Table 1 Parameters of Powered Lift Aircraft

[0152]

[0153] In order to maintain controllable flight after rotor failure at any position, the following control methods are required for a powered aircraft:

[0154] S51: Establish the optimal control model for a powered aircraft after rotor failure at any position;

[0155] The flight process of a powered aircraft after rotor failure at any position is modeled as an optimal control problem.

[0156] The state variables of the optimal control model include the horizontal and vertical velocities of the powered aircraft after rotor failure at any position and the remaining battery percentage; the control variables are the thrust distribution commands for the remaining rotors; the objective is to minimize the total power consumption from the moment of failure to achieving controllable flight.

[0157] S52: Apply optimal control theory to solve the optimal control model and obtain the horizontal and vertical thrust under optimal control after rotor failure at any position of a powered lift aircraft.

[0158] Applying optimal control theory to solve the optimal control problem, we obtain the horizontal and vertical velocities of the powered lift aircraft after rotor failure at any position, and the horizontal and vertical thrust under optimal control after rotor failure at any position. The calculation expressions are as follows:

[0159]

[0160]

[0161]

[0162]

[0163] in, To improve the horizontal thrust under optimal control after rotor failure at any position of the aircraft. To improve the vertical thrust of an aircraft under optimal control after rotor failure at any position. To increase the horizontal speed of an aircraft after rotor failure at any position, To improve the vertical speed of an aircraft after rotor failure at any position. For parameters related to the first-time variables, For parameters related to the second time variable, For parameters related to the third time variable, For parameters related to the fourth time variable, For parameters related to the fifth time variable, For parameters related to the sixth time variable;

[0164] S53: Based on the aerodynamic layout and power system characteristics of powered lift aircraft, establish a whole-aircraft force model after rotor failure at any position of powered lift aircraft, and solve for time-related parameters.

[0165] The expression for calculating the horizontal state is:

[0166]

[0167] in, The magnitude of the horizontal velocity of the aircraft instantly increased by the power at the moment of rotor failure at any position is equal to the cruise speed of the aircraft increased by the power. The magnitude of the horizontal rotor thrust of an aircraft at the instant of rotor failure at any position.

[0168] The expression for calculating the vertical state is:

[0169]

[0170] in, The magnitude of the vertical rotor thrust of the aircraft at the instant of rotor failure at any position.

[0171] S54: Calculate the horizontal and vertical rotor speeds based on time-related parameters and the optimal control under horizontal and vertical thrust after rotor failure at any position of the powered aircraft. The calculation expressions are as follows:

[0172]

[0173]

[0174] in, The number of damaged horizontal rotor blades. This represents the number of damaged vertical rotor blades.

[0175] S55: Based on the horizontal and vertical rotor speeds, calculate the horizontal rotor torque and vertical rotor torque of a powered lift aircraft after rotor failure at any position. The calculation expressions are as follows:

[0176]

[0177]

[0178] in, To improve the torque of the horizontal rotor after rotor failure at any position on an aircraft, To improve the torque of the vertical rotor after the horizontal rotor of an aircraft fails;

[0179] S56: Calculate the discharge current of the battery at the horizontal rotor and the discharge current at the vertical rotor after the failure of the horizontal rotor of the powered lift aircraft, based on the horizontal rotor torque and the vertical rotor torque after the failure of the horizontal rotor of the powered lift aircraft.

[0180] Power-assisted calculation of the equivalent voltage and equivalent current of the motor at the horizontal rotor after rotor failure at any position in an aircraft. The equivalent voltage of the motor at the vertical rotor after rotor failure at any position in an aircraft. With equivalent current The calculation expression is:

[0181]

[0182]

[0183]

[0184]

[0185] Power increases the discharge current of the battery at the horizontal rotor after rotor failure at any position in an aircraft. With the discharge current at the vertical rotor The calculation expression is:

[0186]

[0187]

[0188] S57: Calculate the emergency discharge power of the battery after the rotor fails at any position in a powered lift aircraft, based on the battery discharge voltage, the discharge current of the battery at the horizontal rotor and the discharge current at the vertical rotor after the rotor fails at any position in a powered lift aircraft.

[0189] Using battery discharge voltage The discharge current of the battery at the horizontal rotor after the rotor fails at any position in the aircraft. With the discharge current at the vertical rotor Calculate the emergency discharge power of the battery after rotor failure at any position on an aircraft. The calculation expression is:

[0190]

[0191] In some specific embodiments of the present invention, the failure scenario of the powered lift aircraft rotor is considered as: failure of both tiltrotor rotors, i.e. ; .based on ; From Table 1, we can solve for:

[0192]

[0193]

[0194]

[0195]

[0196]

[0197] .

[0198] After the failure of both horizontal rotors, the rotor speed changes over time as follows: Figure 2 As shown in Figure (a); the battery discharge performance of a powered aircraft after the failure of both horizontal rotors is as follows. Figure 2 As shown in Figure (b) of the document. Figure 2 The vertical rotor speed is along the x-axis; the horizontal rotor speed is along the y-axis; adjust any combination of speeds. The required adjustment time is along the z-axis. For example... Figure 2 In Figure (b), the vertical rotor speed is represented by the x-axis; the horizontal rotor speed by the y-axis; and the battery discharge power by the z-axis.

[0199] After the failure of both tilt rotors (i.e., at time 0), adjustments need to be made along the curved surface. Figure 2 The combination of rotational speeds at any point on the surface in figure (a) To maintain a stable sailing altitude during the adjustment process. Figure 2 Figure (b) is Figure 2 The combination of rotational speeds at any point on the surface in Figure (a) Corresponding to the emergency discharge power of the battery. Investigation revealed that after the failure of both tiltrotors of the powered aircraft selected in this embodiment, navigation was maintained by adjusting the tiltrotor speed. Ultimately, the tiltrotor speed was adjusted to 694.2 RPM, and the vertical rotor speed to 0 RPM. Figure 2 In Figure (a), the tiltrotor speed at a point on the curved surface is 693.9 RPM, and the vertical rotor speed is 0 RPM, with an error of only 0.3 RPM compared to the survey results. This result indicates that the present invention has high accuracy in calculating the emergency battery discharge power of this control method. The time required for the powered aircraft to adjust the tiltrotor speed to 693.9 RPM is 0.33702 s, and after adjusting to this speed, the battery discharge power increases to 31.9384 kW.

[0200] S6: Calculate the controllable flight time after rotor failure based on the emergency discharge power of the battery after rotor failure at any position of the powered aircraft and the percentage of remaining battery charge at the alternate landing safety assessment node. By comparing the controllable flight time with the time required to reach the nearest alternate landing site, assess whether the powered aircraft meets the alternate landing safety requirements under controllable flight conditions after rotor failure.

[0201] The safe power reserve that can be used for emergency landing flights is obtained by subtracting the remaining battery power percentage at the alternate landing safety assessment node from the preset alarm power percentage and then multiplying it by the total battery capacity.

[0202] Divide the safe power reserve by the battery discharge power after the rotor fails at any position of the powered aircraft to obtain the controllable flight time after the rotor fails at any position of the powered aircraft.

[0203] If the controllable flight time after rotor failure at any position of a powered aircraft is greater than the time required to reach the nearest alternate landing site, then the powered aircraft can safely make an alternate landing while in a controllable flight state after rotor failure.

[0204] If the requirements are not met, the location of the alternate landing safety assessment node needs to be adjusted and the entire low-altitude flight route needs to be replanned.

[0205] S7: Taking the total power consumption of low-altitude routes as the objective function and the safety of diversion in controllable flight after rotor failure as the constraint, the latitude and longitude coordinates of the diversion safety assessment nodes of routes that do not meet the diversion safety requirements are adjusted and the initial routes are replanned to obtain low-altitude routes that meet the diversion safety requirements after rotor failure.

[0206] With the total power consumption of the low-altitude route as the objective function and the safety of emergency landing after rotor failure as the constraint, the expressions are as follows:

[0207]

[0208]

[0209] in, To find the minimum value, The remaining battery charge percentage at the backup safety assessment node. To improve the controllable flight time of an aircraft in the event of rotor failure at any position. Time required to reach the nearest alternate airport

[0210] In some specific embodiments of the present invention, the percentage of alarm power relative to battery capacity is used. Set to 0.3, this represents the remaining battery charge percentage at the emergency landing safety assessment node after the failure of both horizontal rotors of the powered aircraft. and The relation is:

[0211]

[0212] Table 2 shows the routes and safety assessment points for diversions where powered aircraft do not meet the requirements for diversion safety.

[0213] Table 2. Routes and Diversion Safety Assessment Nodes Where Powered-Up Aircraft Do Not Meet Diversion Safety Requirements

[0214]

[0215] Table 2 shows that the time required for the remaining battery power of the powered aircraft on route CE to decrease to the alarm battery power at alternate landing safety assessment nodes Q2 and Q4 is less than the time it takes for the powered aircraft to reach the nearest alternate landing site to the current alternate landing safety assessment node, thus failing to meet the alternate landing safety requirements after rotor failure. Similarly, for route DE, the alternate landing safety requirements after rotor failure are not met at alternate landing safety assessment nodes Q2, Q3, and Q4, necessitating the replanning of low-altitude routes CE and DE. The adjusted alternate landing safety assessment nodes on low-altitude routes CE and DE are as follows. , , As shown in Table 3, all adjusted low-altitude routes meet the safety requirements for alternate landings after rotor failure. The final low-altitude routes that meet the safety requirements for alternate landings after rotor failure are as follows: Figure 3 As shown.

[0216] Table 3. Information on alternate landing safety assessment nodes on the adjusted low-altitude routes CE and DE.

[0217]

[0218] In planning low-altitude routes, it is necessary to first determine the available low-altitude airspace, and then plan a low-altitude route within the available airspace that meets the safety requirements for alternate landings after rotor failure. The route width and altitude are calculated, and the available low-altitude airspace is determined. Alternate landing sites that meet the technical constraints for construction are selected within the available low-altitude airspace. The feasibility of alternate landing sites is assessed from the perspective of transfer convenience, and alternate landing sites are determined in areas that simultaneously meet both the technical constraints and transfer convenience requirements. An initial route is planned within the available low-altitude airspace. The battery discharge performance after the failure of both horizontal rotors of a powered aircraft is calculated. The planned low-altitude route should be able to reach the alternate landing site for an alternate landing after the failure of both horizontal rotors of the powered aircraft, thus meeting the safety requirements for alternate landings after rotor failure.

[0219] like Figure 4 As shown, a low-altitude route planning system considering emergency landing safety after rotor failure is used to execute the aforementioned low-altitude route planning method considering emergency landing safety after rotor failure, comprising:

[0220] The extraction module 101 extracts the location information of low-altitude obstacles, delineates the obstacle area in the low-altitude navigation airspace based on the location information of low-altitude obstacles and the navigation deviation, and determines the available low-altitude navigation airspace based on the obstacle area.

[0221] The screening module 102 filters the available low-altitude airspace for alternative landing site construction areas that meet the technical constraints and transfer convenience requirements for alternative landing site construction, and determines the location of the alternative landing site based on the alternative landing site construction area.

[0222] Planning module 103 plans the initial route within the available low-altitude airspace and deploys landing safety assessment nodes at equal intervals along the centerline of the initial route within the alternate landing site;

[0223] The parameter calculation module 104 calculates the percentage of remaining battery power at each diversion safety assessment node based on the remaining battery power of the powered aircraft at the start of cruise, the battery discharge power during the vertical takeoff phase and the climb phase, and calculates the latitude and longitude coordinates of each diversion safety assessment node based on the geographic information system.

[0224] The power calculation module 105 establishes the optimal control model and the whole-aircraft stress model after rotor failure at any position of the powered lift aircraft. It applies the optimal control theory to solve the optimal control model and combines the whole-aircraft stress model to obtain the emergency discharge power of the battery after rotor failure at any position of the powered lift aircraft.

[0225] The evaluation module 106 calculates the controllable flight time after rotor failure based on the emergency discharge power of the battery after rotor failure at any position of the powered aircraft and the percentage of remaining battery charge at the alternate landing safety evaluation node. By comparing the controllable flight time with the time required to reach the nearest alternate landing site, it evaluates whether the powered aircraft meets the alternate landing safety requirements under controllable flight conditions after rotor failure.

[0226] The adjustment module 107 uses the total power consumption of the low-altitude route as the objective function and the safety of the alternate landing in a controllable flight state after the power booster aircraft rotor failure as the constraint. It adjusts the latitude and longitude coordinates of the alternate landing safety assessment nodes of the route that does not meet the alternate landing safety requirements and replans the initial route to obtain a low-altitude route that meets the alternate landing safety requirements after rotor failure.

[0227] Through the collaborative work of the above modules, the safety of alternate landing after rotor failure at any position of the powered aircraft was evaluated, which filled the gap in the analysis of alternate landing safety after rotor failure in the planned low-altitude routes and ensured the safety of the planned low-altitude routes.

[0228] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-altitude flight path planning method considering emergency landing safety after rotor failure, characterized in that, include: S1: Extract the location information of low-altitude obstacles, delineate the obstacle area in the low-altitude navigation airspace based on the location information of low-altitude obstacles and the navigation deviation, and determine the available low-altitude navigation airspace based on the obstacle area. S2: Screen available low-altitude airspace for alternative landing site construction areas that meet the technical constraints and transfer convenience, and determine the location of the alternative landing site based on the construction area. S3: Plan the initial route within the available low-altitude airspace, and deploy landing safety assessment nodes at equal intervals along the centerline of the initial route within the alternate landing site; S4: Calculate the percentage of remaining battery charge at each diversion safety assessment node based on the remaining battery charge of the powered aircraft at the start of cruise, the battery discharge power during the vertical takeoff and climb phases, and calculate the latitude and longitude coordinates of each diversion safety assessment node based on the geographic information system. S5: Establish the optimal control model and the whole-aircraft stress model after rotor failure at any position of the powered lift aircraft. Apply optimal control theory to solve the optimal control model and combine it with the whole-aircraft stress model to obtain the emergency discharge power of the battery after rotor failure at any position of the powered lift aircraft. S6: Calculate the controllable flight time after rotor failure based on the emergency discharge power of the battery after rotor failure at any position of the powered aircraft and the percentage of remaining battery charge at the alternate landing safety assessment node. By comparing the controllable flight time with the time required to reach the nearest alternate landing site, assess whether the powered aircraft meets the alternate landing safety requirements under controllable flight conditions after rotor failure. S7: Using the total power consumption of low-altitude routes as the objective function and the safety of diversion in controllable flight after rotor failure as the constraint, the latitude and longitude coordinates of diversion safety assessment nodes are adjusted for routes that do not meet the diversion safety requirements, and the initial routes are replanned to obtain low-altitude routes that meet the diversion safety requirements after rotor failure.

2. The low-altitude flight path planning method considering alternate landing safety after rotor failure as described in claim 1, characterized in that, Step S1 includes: S11: Extract obstacle location information from public data and geographic information service platforms. The obstacle location information includes the location of immovable cultural relics protection units and the location of restricted airspace within the low-altitude airspace. S12: Delineate the obstacle area based on the location information of obstacles in the low-altitude airspace and the flight deviation. The obstacle area also includes a buffer area. The buffer area has a horizontal dimension equal to the width of the airway and a vertical dimension equal to the height of the airway. S13: Obstacle areas, no-fly zones and surrounding warning airspace are removed from the existing low-altitude airspace to obtain usable low-altitude airspace.

3. The low-altitude flight path planning method considering alternate landing safety after rotor failure according to claim 1, characterized in that, Technical constraints on alternate landing site construction include constraints on the impact area and the height of obstacles. The landing methods are divided into ballistic landing and uncontrolled sliding landing. The maximum value of the impact area of ​​ballistic landing and the impact area of ​​uncontrolled sliding landing is taken as the landing impact area constraint. The usable area within the alternate landing site construction area is greater than the maximum value among the standards for the impact area of ​​a ballistic impact, the impact area of ​​an uncontrolled sliding impact, and the construction area of ​​the alternate landing site. Obstacle height constraints stipulate that the height of obstacles around the alternate landing site must be lower than the obstacle height limit standard of the alternate landing site.

4. The low-altitude flight path planning method considering alternate landing safety after rotor failure according to claim 1, characterized in that, Step S3, which involves planning the initial route within available low-altitude airspace, includes: A straight path is constructed between the starting point and the ending point. If the straight path is not within the available low-altitude airspace, the initial route is adjusted to a path that sequentially connects the starting point, the ending point, and the boundary points of the available airspace.

5. The low-altitude flight path planning method considering alternate landing safety after rotor failure according to claim 1, characterized in that, The calculation of the remaining battery capacity percentage at each backup safety assessment node in step S4 includes: S41: Both vertical takeoff and climb are considered as uniformly accelerated motions with the same acceleration. S42: Calculate the time required for vertical takeoff and climb based on the aircraft's height above the ground and climb acceleration at the end of the vertical takeoff phase; S43: The power consumption during the vertical takeoff and climb phases is obtained by integrating the battery discharge power over time. The upper limits of integration are the time required for vertical takeoff and the time required for climb, respectively. S44: By subtracting the power consumed during the vertical takeoff and climb phases from the battery capacity, the remaining power of the power-lift aircraft's battery is obtained when cruise begins. S45: The percentage of remaining battery charge at the alternate landing safety assessment node is obtained by subtracting the consumed charge from the remaining battery charge of the aircraft when cruise begins and dividing by the battery capacity.

6. The low-altitude flight path planning method considering alternate landing safety after rotor failure according to claim 1, characterized in that, The altitude of the alternate landing safety assessment node is a positive integer multiple of the route altitude and is located within the altitude range between the lower limit and the upper limit of the available low-altitude airspace.

7. The low-altitude flight path planning method considering alternate landing safety after rotor failure according to claim 1, characterized in that, The S5 steps include: S51: Establish the optimal control model for a powered aircraft after rotor failure at any position; S52: Apply optimal control theory to solve the optimal control model and obtain the horizontal and vertical thrust under optimal control after rotor failure at any position of a powered lift aircraft. S53: Based on the aerodynamic layout and power system characteristics of powered lift aircraft, establish a whole-aircraft force model after rotor failure at any position of powered lift aircraft, and solve for time-related parameters. S54: Calculate the horizontal and vertical rotor speeds based on time-related parameters and the horizontal and vertical thrust under optimal control after rotor failure at any position of the powered aircraft. S55: Solve for the horizontal rotor torque and vertical rotor torque of a powered lift aircraft after rotor failure at any position, based on the horizontal rotor speed and vertical rotor speed. S56: Calculate the discharge current of the battery at the horizontal rotor and the discharge current at the vertical rotor after the failure of the horizontal rotor of the powered lift aircraft, based on the horizontal rotor torque and the vertical rotor torque after the failure of the horizontal rotor of the powered lift aircraft. S57: Calculate the emergency discharge power of the battery after the failure of the rotor at any position of the powered lift aircraft, based on the battery discharge voltage, the discharge current of the battery at the horizontal rotor and the discharge current at the vertical rotor after the failure of the rotor at any position of the powered lift aircraft.

8. A low-altitude flight path planning method considering alternate landing safety after rotor failure, as described in claim 1, is characterized in that... The state variables of the optimal control model for a powered aircraft after rotor failure at any position include the horizontal and vertical speeds and the remaining battery percentage after rotor failure at any position. The control variable is the thrust distribution command for the remaining rotors; The goal is to minimize the total power consumption from the moment of failure to the moment controllable flight is achieved.

9. A low-altitude flight path planning method considering alternate landing safety after rotor failure, as described in claim 1, is characterized in that... Emergency landing safety measures after rotor failure include: The safe power reserve that can be used for emergency landing flights is obtained by subtracting the remaining battery power percentage at the alternate landing safety assessment node from the preset alarm power percentage and then multiplying it by the total battery capacity. Divide the safe power reserve by the battery discharge power after the rotor fails at any position of the powered aircraft to obtain the controllable flight time after the rotor fails at any position of the powered aircraft. If the controllable flight time after rotor failure at any position of a powered aircraft is greater than the time required to reach the nearest alternate landing site, then the powered aircraft can safely make an alternate landing while in a controllable flight state after rotor failure.

10. A low-altitude route planning system that considers emergency landing safety after rotor failure, characterized in that, A low-altitude route planning method considering alternate landing safety after rotor failure, as described in any one of claims 1 to 9, includes: The extraction module extracts the location information of low-altitude obstacles, delineates obstacle areas in the low-altitude navigation airspace based on the location information of low-altitude obstacles and navigation deviations, and determines the available low-altitude navigation airspace based on the obstacle areas. The filtering module filters out alternate landing site construction areas within available low-altitude airspace that meet the technical constraints of alternate landing site construction and the convenience of transfer, and determines the location of the alternate landing site based on the alternate landing site construction area. The planning module plans the initial route within the available low-altitude airspace and deploys landing safety assessment nodes at equal intervals along the centerline of the initial route within the alternate landing site. The parameter calculation module calculates the percentage of remaining battery power at each diversion safety assessment node based on the remaining battery power of the powered aircraft at the start of cruise, the battery discharge power during the vertical takeoff and climb phases, and calculates the latitude and longitude coordinates of each diversion safety assessment node based on the geographic information system. The power calculation module establishes the optimal control model and the whole-aircraft stress model after rotor failure at any position of the powered lift aircraft. It applies optimal control theory to solve the optimal control model and combines the whole-aircraft stress model to obtain the emergency discharge power of the battery after rotor failure at any position of the powered lift aircraft. The evaluation module calculates the controllable flight time after rotor failure based on the emergency discharge power of the battery after rotor failure at any position of the powered aircraft and the percentage of remaining battery charge at the alternate landing safety evaluation node. By comparing the controllable flight time with the time required to reach the nearest alternate landing site, the module evaluates whether the powered aircraft meets the alternate landing safety requirements under controllable flight conditions after rotor failure. The adjustment module uses the total power consumption of the low-altitude route as the objective function and the safety of the alternate landing in a controllable flight state after the rotor failure of the aircraft as the constraint. It adjusts the latitude and longitude coordinates of the alternate landing safety assessment nodes of the route that does not meet the alternate landing safety requirements and replans the initial route to obtain a low-altitude route that meets the alternate landing safety requirements after rotor failure.

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