A Traffic Flow Assignment Method for Urban Logistics Drones

Abstract

This invention discloses a traffic flow allocation method for urban logistics drones, with the following specific steps: Calculating the safety impedance of each segment of the airway network based on the safety impact of the logistics drone's flight on ground personnel; calculating the efficiency impedance of each segment of the airway network considering the maximum capacity of the airways and flight energy consumption; calculating the comprehensive impedance of the urban low-altitude public airway network segments by integrating safety and efficiency impedances; establishing a dynamic traffic flow allocation model for the urban low-altitude airway network and determining the constraints for traffic flow allocation; and finally, using a staged allocation method to complete the traffic flow allocation for the public airway network. This invention employs the above-mentioned traffic flow allocation method for urban logistics drones, which can ensure efficient and safe flight of low-altitude aircraft and improve the operational efficiency of low-altitude airspace traffic flow.

Description

Technical Field

[0001] This invention belongs to the field of low-altitude traffic management technology, and in particular, a traffic flow allocation method for urban logistics drones. Background Technology

[0002] With the increasing demand for diverse, large-scale, and high-density aircraft flights in low-altitude airspace, traditional air traffic management methods are unable to meet the growing low-altitude traffic flow. Current management methods for low-altitude aircraft operations are inadequate, lacking effective approaches to allocate airspace flight demand, which hinders low-altitude traffic flow management and monitoring. To improve the safety and efficiency of large-scale aircraft flights, distributing flight traffic fairly and evenly across the low-altitude public airway network can reduce network congestion and improve overall network traffic efficiency. Therefore, designing a traffic flow allocation method for urban logistics drones is necessary. Summary of the Invention

[0003] The purpose of this invention is to provide a traffic flow allocation method for urban logistics drones, which can fairly and evenly allocate traffic flow to various segments of the airway network, overcome the shortcomings of existing low-altitude traffic flow management methods, and help improve the overall traffic operation efficiency of the airway network.

[0004] To achieve the above objectives, the present invention provides a traffic flow allocation method for urban logistics drones, comprising the following steps:

[0005] S1. Set the safety impedance for public airway network segments;

[0006] S2. Set the efficiency impedance of the public airway network segments;

[0007] S3. Calculate the overall impedance of the public airway network segments;

[0008] S4. Establish a traffic flow allocation model for logistics drones and determine the constraints.

[0009] S5. Use the phased allocation method to complete the traffic flow allocation of the public airway network.

[0010] Preferably, the safety impedance setting for public airway network segments takes the safety impact on ground personnel caused by logistics aircraft during flight as the main consideration in the airway network security impedance function, that is:

[0011] r a =P uav N people F die

[0012] r a P is the safety impedance of road segment a; uavThe hourly crash rate of logistics aircraft is directly related to their reliability; N people The number of people involved in the collision with the logistics aircraft at the time of the accident; F die This represents the probability of death for ground personnel when struck by a logistics aircraft.

[0013] The number N of people who collided with the logistics aircraft at the time of the accident people The calculation method is shown in the following formula:

[0014] N people =Aρ people

[0015] In the formula, A is the impact area of ​​the logistics aircraft; ρ people The population density of the area traversed by flight segment a.

[0016] The probability of fatalities when a logistics aircraft collides with the ground (F) die The flight status of logistics aircraft is related to the ground environment, and the calculation method is shown in the following formula:

[0017]

[0018] In the formula, s is the shielding index, which is the degree of exposure of ground personnel in the flight path area of ​​the logistics aircraft; λ is the energy required for the mortality rate of ground personnel to reach 50% after being hit by the logistics aircraft when the shielding index S is 0.5; μ is the energy threshold required for ground personnel to be killed by the impact when the shielding index S approaches 0; E is the impact kinetic energy, which is calculated as follows:

[0019]

[0020] In the above formula, m is the mass of the logistics aircraft upon impact, including the aircraft's weight and the weight of the packages; q is the drag coefficient; ρ A ρ is the air density; h is the flight altitude of the logistics aircraft.

[0021] Preferably, a common airway network segment efficiency impedance is set, that is, the efficiency impedance function of airway network segment a is calculated. The total cost caused by the selected segment can be expressed as:

[0022]

[0023] In the formula, d is the minimum interval requirement for aircraft, and t is the length of a unit time period.

[0024] Energy consumption E of flight segment a a The calculation method is shown in the following formula:

[0025] E a =U×SEC×L a ×m rel

[0026] In the formula, U is the unit cost of energy, SEC is the energy consumption ratio, and m rel The relative weights are calculated using the following formula:

[0027]

[0028] In the formula, m OWE For the mass of an empty aircraft, m MTOW The maximum takeoff and landing weight is LF, which represents the load factor.

[0029] Preferably, the calculation of the comprehensive impedance of the public airway network segment will combine steps S1 and S2 to construct the comprehensive impedance W of the urban low-altitude airway network segment a from both safety and efficiency perspectives. a The specific formula is shown below:

[0030] W a (t)=ωr a +(1-ω)t a

[0031] In the formula r a Let t be the safety impedance function for flight segment a. a Let ω be the efficiency impedance function and ω be the weighting function. Since different impedance functions have different ranges and magnitudes, this paper uses the min-max standardization method to standardize the data.

[0032]

[0033] Where q'(x) is the normalized value of each sub-impedance function, and q(x) is the actual value of each sub-impedance; q(x) min and q(x) max These are the minimum and maximum values ​​of each sub-impedance, respectively.

[0034] Preferably, in step S4, a dynamic traffic flow allocation model for the urban low-altitude airway network is established, constraints are determined, and traffic flow allocation for the public airway network is performed. This mainly includes the following steps:

[0035] S401. Set the objective function Q, the specific formula of which is shown below:

[0036]

[0037] In the formula x a (t) represents the traffic flow from point t to the destination on flight segment a, where A is the set of directed flight segments, and W... a (t) represents the traffic load x on flight segment a during time period t. a The total travel cost caused by (t).

[0038] S402, for The optimal model of a dynamic system will satisfy the following constraints:

[0039] Constraint 1, the basic constraint, is shown in the following formula:

[0040]

[0041]

[0042]

[0043] Where u a (t) and v a (t) are decision variables, representing the number of aircraft entering segment a at time t and the number of aircraft leaving segment a at time t, respectively. a (t) is a state variable representing the traffic volume on flight segment a at time t, and the number of aircraft exiting flight segment a at time t to reach destination s can be expressed as: and

[0044] Constraint 2: Non-negativity constraint, see the following formula for details:

[0045]

[0046]

[0047] That is, all the variables considered are non-negative. Let t be the entry quantity of an aircraft entering segment a at time t to reach its destination s. Let t be the distance an aircraft needs to travel from segment a to its destination s when it enters flight segment a at time t. Let be the traffic flow on segment a towards destination s at time t.

[0048] Constraint 3: Boundary constraint, see the following formula for details:

[0049]

[0050] That is, at any time t, there is a traffic volume of aircraft on segment a to destination s at time t that is 0; similarly, there is also a traffic volume of aircraft entering segment a at time t that is 0 to reach destination s.

[0051]

[0052] That is, at the initial moment, there is no traffic on the network and the outflow rate is 0.

[0053] Constraint 4: First-In-First-Out (FIFO) constraint, see the following formula:

[0054] The aircraft that enters segment a first must leave segment a first, i.e., satisfy the following equation:

[0055]

[0056] In the formula τ a (t) represents the actual impedance at time t, and τ a (t+Δt) represents the actual impedance at time t+Δt. The aircraft that enters segment a at time t departs at time t+Δt.

[0057] Constraint 5: Maximum number of aircraft allowed per flight segment, see the following formula for details:

[0058] x a (t)≤s am ×L a

[0059]

[0060] s am Maximum aircraft flight flow density (flights / km)

[0061] Constraint 6: Segment state constraint, see the following formula for details:

[0062]

[0063] Constraint 7: Node balance constraint, see the following formula for details:

[0064]

[0065] A l B represents the flow of traffic into node l. l This refers to the flow of traffic exiting node l. Let be the flow generated at node l at time t that is destined for destination s.

[0066] Constraint 8: Maximum flight distance constraint, see the following formula for details:

[0067] Flight time should not exceed the maximum flight time of the aircraft:

[0068]

[0069] Preferably, in step S5, the traffic flow allocation of the public airway network is completed using the phase allocation method, which mainly includes the following steps:

[0070] S501, Average traffic volume corresponding to the m-th time period. Traffic flow is allocated to obtain the average traffic volume for each flight segment.

[0071] S502, Updated Flight Segment Impedance As the initial impedance for allocation;

[0072] S503, the difference traffic volume Δq for the i-th discrete time period. a (Δt m Traffic flow is allocated to obtain the differential average traffic volume Δx for each flight segment. a (Δt m );

[0073] S504, Calculation The traffic volume allocated to each flight segment in discrete time periods is obtained;

[0074] S505. Determine if the allocation of all time periods between OD pairs is complete: If not, increment the counter variable m, and increment the counter variable t. a (Δt m )=t a (x a (Δt m After allocation is complete, proceed to step S506.

[0075] S506. End the loop and output the dynamic traffic volume distribution for each flight segment.

[0076] Therefore, the present invention adopts the above-mentioned traffic flow allocation method for urban logistics drones, which can fairly and evenly allocate traffic flow to each segment of the airway network, overcome the shortcomings of existing low-altitude traffic flow management methods, and help improve the overall traffic operation efficiency of the airway network.

[0077] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0078] Figure 1 This is a flowchart of a traffic flow allocation method for urban logistics drones according to the present invention. Detailed Implementation

[0079] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0080] The present invention provides a traffic flow allocation method flowchart for urban logistics drones, as shown in the embodiment of the present invention. Figure 1 As shown, it includes the following steps:

[0081] S1. Set the safety impedance for public airway network segments;

[0082] The aforementioned setting of public airway network segment safety impedance takes the safety impact on ground personnel caused by logistics aircraft during flight as the main consideration in the airway network security impedance function, namely:

[0083] r a =P uav Npeople F die

[0084] r a P is the safety impedance of road segment a; uav The hourly crash rate of logistics aircraft is directly related to their reliability; N people The number of people involved in the collision with the logistics aircraft at the time of the accident; F die This represents the probability of death for ground personnel when struck by a logistics aircraft.

[0085] The number N of people who collided with the logistics aircraft at the time of the accident people The calculation method is shown in the following formula:

[0086] N people =Aρ people

[0087] In the formula, A is the impact area of ​​the logistics aircraft; ρ people The population density of the area traversed by flight segment a.

[0088] The probability of fatalities when a logistics aircraft collides with the ground (F) die The flight status of logistics aircraft is related to the ground environment, and the calculation method is shown in the following formula:

[0089]

[0090] In the formula, s is the shielding index, which is the degree of exposure of ground personnel in the flight path area of ​​the logistics aircraft; λ is the energy required for the mortality rate of ground personnel to reach 50% after being hit by the logistics aircraft when the shielding index S is 0.5; μ is the energy threshold required for ground personnel to be killed by the impact when the shielding index S approaches 0; E is the impact kinetic energy, which is calculated as follows:

[0091]

[0092] In the above formula, m is the mass of the logistics aircraft upon impact, including the aircraft's weight and the weight of the packages; q is the drag coefficient; ρ A ρ is the air density; h is the flight altitude of the logistics aircraft.

[0093] S2. Set the efficiency impedance of the public airway network segments;

[0094] The setting of the efficiency impedance of a public airway network segment refers to calculating the efficiency impedance function of airway network segment a. The total cost incurred by the selected segment can be expressed as follows:

[0095]

[0096] In the formula, d is the minimum interval requirement for aircraft, and t is the length of a unit time period.

[0097] Energy consumption E of flight segment a a The calculation method is shown in the following formula:

[0098] E a =U×SEC×L a ×m rel

[0099] In the formula, U is the unit cost of energy, SEC is the energy consumption ratio, and m rel The relative weights are calculated using the following formula:

[0100]

[0101] In the formula, m OWE For the mass of an empty aircraft, m MTOW The maximum takeoff and landing weight is LF, which represents the load factor.

[0102] S3. Calculate the overall impedance of the public airway network segments;

[0103] The calculation of the comprehensive impedance of the public airway network segment will combine steps one and two to construct the comprehensive impedance W of the urban low-altitude airway network segment a from both safety and efficiency perspectives. a The specific formula is shown below:

[0104] W a (t)=ωr a +(1-ω)t a

[0105] In the formula r a Let t be the safety impedance function for flight segment a. a Let ω be the efficiency impedance function and ω be the weighting function. Since different impedance functions have different ranges and magnitudes, this paper uses the min-max standardization method to standardize the data.

[0106]

[0107] Where q'(x) is the normalized value of each sub-impedance function, and q(x) is the actual value of each sub-impedance; q(x) min and q(x) max These are the minimum and maximum values ​​of each sub-impedance, respectively.

[0108] S4. Establish a dynamic traffic flow allocation model for the urban low-altitude airway network, determine the constraints, and allocate traffic flow for the public airway network. This mainly includes the following steps:

[0109] S401. Set the objective function Q, the specific formula of which is shown below:

[0110]

[0111] In the formula x a (t) represents the traffic flow from point t to the destination on flight segment a, where A is the set of directed flight segments, and W... a (t) represents the traffic load x on flight segment a during time period t. a The total travel cost caused by (t).

[0112] S402, for The optimal model of a dynamic system will satisfy the following constraints:

[0113] Constraint 1, the basic constraint, is shown in the following formula:

[0114]

[0115]

[0116]

[0117] Where u a (t) and v a (t) are decision variables, representing the number of aircraft entering segment a at time t and the number of aircraft leaving segment a at time t, respectively. a (t) is a state variable representing the traffic volume on flight segment a at time t, and the number of aircraft exiting flight segment a at time t to reach destination s can be expressed as: and

[0118] Constraint 2: Non-negativity constraint, see the following formula for details:

[0119]

[0120]

[0121] That is, all the variables considered are non-negative. Let t be the entry quantity of an aircraft entering segment a at time t to reach its destination s. Let t be the distance an aircraft needs to travel from segment a to its destination s when it enters flight segment a at time t. Let be the traffic flow on segment a towards destination s at time t.

[0122] Constraint 3: Boundary conditions, see the following formula for details:

[0123]

[0124] That is, at any time t, there is a traffic volume of aircraft on segment a to destination s at time t that is 0; similarly, there is also a traffic volume of aircraft entering segment a at time t that is 0 to reach destination s.

[0125]

[0126] That is, at the initial moment, there is no traffic on the network and the outflow rate is 0.

[0127] Constraint 4: First-In-First-Out (FIFO) rule, see the following formula:

[0128] The aircraft that enters segment a first must leave segment a first, i.e., satisfy the following equation:

[0129]

[0130] In the formula τ a (t) represents the actual impedance at time t, and τ a (t+Δt) represents the actual impedance at time t+Δt. The aircraft that enters segment a at time t departs at time t+Δt.

[0131] Constraint 5: Maximum number of aircraft allowed on a flight segment, see the following formula for details:

[0132] x a (t)≤s am ×L a

[0133]

[0134] s am Maximum aircraft flight flow density (flights / km)

[0135] Constraint 6: Segment status, see the following formula for details:

[0136]

[0137] Constraint 7: Node balance constraint, see the following formula for details:

[0138]

[0139] A l B represents the flow of traffic into node l. l This refers to the flow of traffic exiting node l. Let be the flow generated at node l at time t that is destined for destination s.

[0140] Constraint 8: Maximum flight distance, see the following formula:

[0141] Flight time should not exceed the maximum flight time of the aircraft:

[0142]

[0143] S5. Using the phased allocation method, traffic flow allocation for the public airway network is completed, mainly including the following steps:

[0144] S501, Average traffic volume corresponding to the m-th time period. Traffic flow is allocated to obtain the average traffic volume for each flight segment.

[0145] S502, Updated Flight Segment Impedance As the initial impedance for allocation;

[0146] S503, the difference traffic volume Δq for the m-th discrete time period. a (Δt m Traffic flow is allocated to obtain the differential average traffic volume Δx for each flight segment. a (Δt m );

[0147] S504, Calculation The traffic volume allocated to each flight segment in discrete time periods is obtained;

[0148] S505. Determine if the allocation of all time periods between OD pairs is complete: If not, increment the counter variable m, and increment the counter variable t. a (Δt m )=t a (x a (Δt m After allocation is complete, proceed to step S506.

[0149] S506. End the loop and output the dynamic traffic volume distribution for each flight segment.

[0150] Therefore, the present invention adopts the above-mentioned traffic flow allocation method for urban logistics drones, which can fairly and evenly allocate traffic flow to each segment of the airway network, overcome the shortcomings of existing low-altitude traffic flow management methods, and help improve the overall traffic operation efficiency of the airway network.

[0151] 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A traffic flow allocation method for urban logistics drones, characterized in that, Includes the following steps: S1. Set the safety impedance for public airway network segments; S2. Set the efficiency impedance of the public airway network segments; S3. Calculate the overall impedance of the public airway network segments; The calculation of the comprehensive impedance of the public airway network segment will combine steps S1 and S2 to construct the comprehensive impedance of urban low-altitude airway network segment a from both safety and efficiency perspectives. The specific formula is shown below: ； In the formula Let be the safety impedance function for flight segment a. The efficiency impedance function, As the weighting function, and since different impedance functions have different ranges of magnitude, a min-max standardization method is used to standardize the data. ； in, These are the normalized values ​​of each sub-impedance function. These are the actual values ​​of each sub-impedance; and These are the minimum and maximum values ​​of each sub-impedance, respectively; S4. Establish a traffic flow allocation model for logistics drones, determine constraints, and perform traffic flow allocation on the public airway network, including the following steps: S401. Set the objective function Q, the specific formula of which is shown below: ； In the formula Let A be the traffic flow from route a to its destination during time period t, where A is the set of directed routes. This represents the traffic load during time period t on flight segment a. The total travel expenses incurred; S402, for , The optimal model of the dynamic system will satisfy the basic constraints, non-negativity constraints, boundary constraints, first-in-first-out constraints, maximum number of aircraft per segment constraints, segment state constraints, node balance constraints, and maximum flight distance constraints. S5. Using the phased allocation method, traffic flow allocation for the public airway network is completed, including the following steps: S501, Average traffic volume corresponding to the m-th time period. Traffic flow is allocated to obtain the average traffic volume for each flight segment. ; S502, Updated Flight Segment Impedance , as the initial impedance for allocation; S503, Traffic volume difference for the i-th discrete time period Traffic flow is allocated to obtain the differential average traffic volume for each flight segment. ; S504, Calculation This yields the traffic volume allocated to each flight segment during discrete time periods. S505. Determine if the allocation of all time periods between OD pairs is complete: If not, increment the counter variable m. Allocation complete, transfer to S506; S506. End the loop and output the dynamic traffic volume distribution for each flight segment.

2. The traffic flow allocation method for urban logistics drones according to claim 1, characterized in that, In step S1, the setting of the public airway network segment safety impedance takes the safety impact on ground personnel caused by logistics aircraft during flight as the main consideration factor in the airway network security impedance function, that is: ； Let the safe impedance be that of road segment a; The hourly crash rate of logistics aircraft is directly related to their reliability. The number of people involved in the collision with the logistics aircraft at the time of the accident; This represents the probability of death for ground personnel when struck by a logistics aircraft.

3. The traffic flow allocation method for urban logistics drones according to claim 1, characterized in that, In step S2, setting the efficiency impedance of a common airway network segment involves calculating the efficiency impedance function of airway network segment a. Specifically, the total cost incurred by the selected segment can be expressed as: ； In the formula, d is the minimum interval requirement for aircraft, and t is the length of a unit time period; Energy consumption of flight segment a The calculation method is shown in the following formula: ； In the formula, For energy unit cost, Energy efficiency ratio These are relative weights.

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