1. The urban multipoint circulating emergency evacuation and simulation deduction method based on the variable cells is characterized by comprising the following steps of:

s1, initializing a traffic evacuation road network, designating a plurality of parking points, a plurality of evacuation points and a plurality of safety points, and acquiring a traffic state;

s2, mapping the actual road network and the evacuation scene to a virtual road network based on a variable cell transmission model;

s3, establishing a path selection model of vehicle many-to-many cycle reciprocating evacuation, modeling, and carrying out parameter solution to obtain an evacuation path and minimum evacuation time of the vehicle;

s4, performing real-time simulation rehearsal evaluation on the evacuation path solved under the determined scene in the virtual road network, wherein the simulation rehearsal evaluation comprises evaluation indexes;

s5, diagnosing whether an evacuation bottleneck exists according to the simulation preview evaluation, and outputting an evacuation path and an evaluation index if the evacuation bottleneck does not exist; repeating the steps S2-S4 after the bottleneck is optimized until the evacuation bottleneck is eliminated or the evacuation target is reached, wherein D is delayed when the section is delayed_xlIntersection delay D_ycRespectively exceed the set threshold value D_x0、D_y0And when the evacuation target is not reached, the evacuation bottleneck is judged to exist.

2. The method according to claim 1, wherein S1 comprises the following sub-steps:

s101, determining an evacuation scene;

s102, defining static characteristic parameters of a road network;

s103, acquiring the dynamic traffic flow state of the evacuation road network.

3. The method according to claim 1, wherein the step S2 includes:

s201, corresponding the attribute characteristics of an actual road section and an intersection to a virtual road network;

s202, corresponding the attribute characteristic change of the evacuation scene to a virtual road network.

4. The method according to claim 1, wherein in step S2, the actual road network is mapped to the simulated road network according to the definition of the variable cells;

variable cell means that the length of the cell is variable, and the length of the cell is l_iWith a given standard cell length l₀Satisfies the following conditions:

l₀≤l_i≤2l₀

the maximum number of vehicles Q that can flow into or out of the cells is determined by the design traffic capacity of the one-way road segment:

Q＝N_a×N_b×N_c×N_d×T

N_adetermining the traffic capacity of a next lane at the speed of the vehicle; n is a radical of_bThe road classification coefficient is the type of the lane; n is a radical of_cClassifying coefficients for the number of lanes; n is a radical of_dIs an intersection correction coefficient; t is a time interval;

the maximum capacity N of the unit cell satisfies:

N＝k_j×l_i×l_n

k_ja vehicle jam density; l_nThe number of lanes corresponding to the cells;

when a variable cellular transmission model is established, a road section is firstly divided into a plurality of small sections according to different lane numbers, and if the small sections do not meet the condition of l₀≤l_i≤2l₀Then divide the small section into several segments with length l₀And a length of l_iIf the cell is satisfied, marking the cell as a cell; and when the last cell has a vehicle needing to be steered and the phase runs in the valid green light time, the vehicle turns to the first cell of other road sections.

5. The method according to claim 1, wherein the step S3 specifically comprises:

s301, let the evacuation network be G ═ P, E, S, R, P ═ P (P₁，P₂，…，P_m) Is a set of limited parking spots; e ═ E (E)₁，E₂，…，E_n) Is a collection of limited evacuation points; (S) ═ S₁，S₂，…，S_q) Is a set of limited security points, and R is a set of limited arcs in the network;

s302, based on the variable cell transmission model, establishing a path selection model for vehicle many-to-many cycle evacuation with the minimum total evacuation time as a target;

s303, solving the path selection model to obtain the complete evacuation path and the minimum evacuation time of the vehicle.

6. The method according to claim 5, wherein the total evacuation time in the path selection model is obtained by multiplying the total traffic by the time interval, wherein the objective function of the total traffic is:

Z₁is the sum of the flow rates of the cells in all time periods, T is a time interval, C represents a set of cells, C_RA set of cells representing a parking spot and a safety spot,the flow on cell i is at time t;

wherein the content of the first and second substances,

in the formula (I), the compound is shown in the specification,the flow on cell i is at time t;the flow rate on the cell i in the t-1 time period;the flow from cell p to cell i for a time period of t-1;the flow from cell i to cell j for a time period t;the flow from cell i to cell j for a time period of t-1; c represents a set of cells; gamma-shaped^-1(i) Is the upstream adjacent cell set of cell i; gamma-shaped(i) A set of downstream neighboring cells that are cell i; l₀Is the standard cell length; l_iIs the length of the cell i, l_jIs the cell j length;the maximum number of vehicles that can flow into or out of cell i for a period t,the maximum number of vehicles that can flow into or out of cell j for a period t;the value of w/v of the cellular j in the period t, v is the free flow speed, and w is the back propagation speed in congestion;the maximum capacity of cell j for time period t;the flow on cell j for time period t.

7. The method according to claim 5, wherein in step S302, the vehicle route is selected according to an evacuation plan, and the formula is as follows:

wherein m is_kThe number of vehicles arriving for each safety point; n is_lThe number of vehicles required for each evacuation point; gamma-shaped^-1(i) Is the upstream adjacent cell set of cell i;p represents an upstream neighboring cell of the cell i;the flow from cell p to cell i for a period of t; Γ (i) is a set of downstream neighboring cells of cell i; j represents a downstream neighboring cell of the cell i;the flow from cell i to cell j for a time period t; n is_iThe number of vehicles required by the cell i is the number of the vehicles required by the cell i, and the cell i is positioned at an evacuation point; c_eIs a set of cells representing evacuation points.

8. The method according to claim 5, wherein the path is optimized by using a-algorithm to establish a cost estimation function in step S302, wherein the estimation function is as follows:

F(i)＝G(i)+H(i)i∈C

wherein, F (i) represents the cost estimated value from the evacuation starting point to the cell i and then to the evacuation destination, G (i) represents the cost actual consumption value from the evacuation starting point to the cell i, and H (i) represents the cost estimated value from the cell i to the evacuation destination; c. C_i1Representing a predicted value of the distance from a cell i to an evacuation starting point; d_iRepresenting the distance from the cell i to the evacuation starting point; d_(i)maxRepresenting the maximum distance from the cell i to the evacuation starting point; c. C_i2Representing a predicted value of the distance from a cell i to an evacuation destination; s_iRepresenting the distance from the cell i to the evacuation destination; s_(i)maxRepresenting the maximum distance from the cell i to the evacuation destination; c. C_i3Representing a congestion degree estimated value of a cell i caused by existing vehicles in a road network; w_iThe number of the existing vehicles of the cell i is represented, and the vehicles do not comprise planned vehicles; n is a radical of_(i)maxRepresenting the number of vehicles which can be accommodated by the cell i at maximum; c. C_i4The estimated value of the crowdedness of the cell i caused by the z-1 planned vehicles when the next path of the z-th vehicle is planned at the time k is shown; sigma w_ziRepresenting the total number of planned vehicles that cell i has entered;denotes c_i1The coefficient of (a);denotes c_i2The coefficient of (a);denotes c_i3The coefficient of (a);denotes c_i4The coefficient of (a);

the optimized objective function is that the cost estimated value is minimum: minZ₂＝F(i)。

9. The city multipoint circulation type emergency evacuation and simulation deduction method based on variable cells as claimed in claim 1, wherein the evaluation indexes comprise travel time, delay time, parking time, average speed, and queuing condition of evacuation vehicles.

10. The method for variable-cell-based urban multipoint circulating emergency evacuation and simulation deduction according to any one of claims 1 to 9, wherein the evacuation bottleneck at S5 comprises any one of a road bottleneck, an intersection bottleneck and a traffic bottleneck.

Background

In recent years, a large city hosts or undertakes more and more activities such as large-scale sports meetings, events and the like, and has dense urban population distribution, complex transportation system, large travel demand and limited emergency resources.

An accident event which is raised to emergency evacuation can be regarded as a systematic disaster with uncertain and rapid increase of traffic volume in a limited space-time range, and a public transport system (such as ground buses, rail transit and the like) is bound to become a most suitable urban emergency evacuation tool with the advantages of large capacity, less occupied road resources, high reliability and strong controllability under the background that urban traffic congestion is increasingly serious. Due to the sudden, unpredictable nature of the accident, the area of the accident often does not have enough buses available to evacuate the large population to a safe point. Generally, a bus is required to go to an event occurrence area from an adjacent bus station, then carry evacuation personnel to a safe area, and finally return to the bus station. Thus, the emergency evacuation process can be described as a research and distribution problem for properly allocating vehicles and setting rescue routes under limited resource conditions.

In the present stage, the emergency evacuation problem solving is roughly divided into two modes of simulation and theoretical optimization, and the simulation model can be divided into three categories of macroscopic, mesoscopic and microscopic. Compared with a theoretical model, the simulation model can enable a researcher to clearly and intuitively observe the whole emergency evacuation process, can quickly find exposed local problems, and cannot necessarily find the optimal solution of an evacuation path. The theoretical model can be divided into different types according to research scenes and optimization targets, most of the theoretical models can obtain optimal solutions, but the problems of local road networks cannot be found, and the situation that the road network requirements and the running condition dynamically fluctuate is difficult to adapt to. A large number of scholars at home and abroad research the problem of emergency evacuation by using buses from the aspects of route planning and the like, but the following problems are not considered:

(1) the problems of synchronous evacuation of the evacuation areas, the capacity of safety points and multiple points are less considered, for example, the overall research is carried out on a many-to-many circulating type evacuation process that buses arrive at multiple accident areas from multiple bus stations, go to multiple safety areas after waiting for evacuation personnel to get on the bus and the buses can return to the accident areas for multiple times;

(2) the method has the advantages that the road network failure superposition risk conditions are less considered, such as the interference of actual traffic road conditions in the evacuation process and the failure of evacuation roads and nodes, which are common in the actual scene;

(3) a complete set of optimization mechanism and method is not provided, for example, key technologies such as evacuation path selection result, simulation preview evaluation and emergency evacuation measure optimization are combined into a whole to form a complete evacuation method system, so that decision support is provided for relevant departments.

Disclosure of Invention

The invention aims to provide a Variable Cell Transmission Model (VCTM) -based urban multipoint circulating emergency evacuation and simulation deduction method, which is used for researching a multi-to-multi complex evacuation problem which is more suitable for actual vehicles to go to a plurality of evacuation areas from a plurality of stations and then to a plurality of safety areas, and the shortest total travel time on the premise of finishing evacuation tasks. The variable cellular transmission model provided by the invention is characterized in that a road section is divided into a plurality of small sections with different lengths, called cells, the time is dispersed into uniform time periods, and the traffic flow state of the cells is updated once every time period. VCTM-based emergency relief systems are embodied as follows: the actual road network is mapped to the simulation road network according to the definition of the variable cells; the algorithm for solving the vehicle path selection follows the transmission rule of the variable cells; simulation deduction is based on the principle of variable cell transmission to evaluate evacuation paths and diagnose potential bottlenecks.

The simulation deduction is based on a variable cell transmission model, can simulate the running conditions of vehicles according to the optimized evacuation route under different traffic states, road network node failure and traffic control measure (reverse lane and intersection control) implementation scenes, and can obtain the real-time change condition of the road network traffic volume and the evacuation time and route of each evacuation vehicle in the evacuation process. The simulation deduction can be widely suitable for the change of urban road structures, and the obtained evaluation indexes are verified to have higher reliability.

In order to achieve the purpose of the invention, the urban multipoint circulating emergency evacuation and simulation deduction method based on the variable cellular transmission model comprises the following steps:

s1, initializing a traffic evacuation road network, designating a plurality of parking points, a plurality of evacuation points and a plurality of safety points, and acquiring a traffic state;

s2, mapping the actual road network and the evacuation scene to a virtual road network based on a variable cell transmission model;

s3, establishing a path selection model of vehicle many-to-many cycle reciprocating evacuation, modeling, and carrying out parameter solution to obtain an evacuation path and minimum evacuation time of the vehicle;

s4, performing real-time simulation rehearsal evaluation on the evacuation path solved under the determined scene in the virtual road network, wherein the simulation rehearsal evaluation comprises evaluation indexes;

s5, diagnosing whether an evacuation bottleneck exists according to the simulation preview evaluation, and outputting an evacuation path and an evaluation index if the evacuation bottleneck does not exist; repeating the steps S2-S4 after the bottleneck is optimized until the evacuation bottleneck is eliminated or the evacuation target is reached, wherein D is delayed when the section is delayed_xlIntersection delay D_ycRespectively exceed the set threshold value D_x0、D_y0And when the evacuation target is not reached, the evacuation bottleneck is judged to exist.

Further, step S1 includes the following sub-steps:

s101, determining an evacuation scene;

s102, defining static characteristic parameters of a road network;

s103, acquiring the dynamic traffic flow state of the evacuation road network.

Further, step S2 includes the following sub-steps:

s201, corresponding the attribute characteristics of an actual road section and an intersection to a virtual road network;

s202, corresponding the attribute characteristic change of the evacuation scene to a virtual road network.

Further, in the step S2, the actual road network is mapped to the simulated road network according to the definition of the variable cell;

variable cell means that the length of the cell is variable, and the length of the cell is l_iWith a given standard cell length l₀Satisfies the following conditions:

l₀≤l_i≤2l₀

the maximum number of vehicles Q that can flow into or out of the cells is determined by the design traffic capacity of the one-way road segment:

Q＝N_a×N_b×N_c×N_d×T

N_adetermining the traffic capacity of a next lane at the speed of the vehicle; n is a radical of_bThe road classification coefficient is the type of the lane; n is a radical of_cClassifying coefficients for the number of lanes; n is a radical of_dIs an intersection correction coefficient; t is a time interval;

the maximum capacity N of the unit cell satisfies:

N＝k_j×l_i×l_n

k_ja vehicle jam density; l_nThe number of lanes corresponding to the cells;

when a variable cellular transmission model is established, a road section is firstly divided into a plurality of small sections according to different lane numbers, and if the small sections do not meet the condition of l₀≤l_i≤2l₀Then divide the small section into several segments with length l₀And a length of l_iIf the cell is satisfied, marking the cell as a cell; and when the last cell has a vehicle needing to be steered and the phase runs in the valid green light time, the vehicle turns to the first cell of other road sections.

Further, the S3 specifically includes:

s301, let the evacuation network be G ═ P, E, S, R, P ═ P (P₁，P₂，…，P_m) Is a set of limited parking spots; e ═ E (E)₁，E₂，…，E_n) Is a collection of limited evacuation points; (S) ═ S₁，S₂，…，S_q) Is a set of limited security points, and R is a set of limited arcs in the network;

s302, based on the variable cell transmission model, establishing a path selection model for vehicle many-to-many cycle evacuation with the minimum total evacuation time as a target;

s303, solving the path selection model to obtain the complete evacuation path and the minimum evacuation time of the vehicle.

Further, the total evacuation time in the path selection model is obtained by multiplying the total flow by the time interval, wherein the objective function of the total flow is:

Z₁is the sum of the flow rates of the cells in all time periods, T is a time interval, C represents a set of cells, C_RA set of cells representing a parking spot and a safety spot,the flow on cell i is at time t;

wherein the content of the first and second substances,

in the formula (I), the compound is shown in the specification,the flow on cell i is at time t;the flow rate on the cell i in the t-1 time period;the flow from cell p to cell i for a time period of t-1;the flow from cell i to cell j for a time period t;the flow from cell i to cell j for a time period of t-1; c represents a set of cells; gamma-shaped^-1(i) Is the upstream adjacent cell set of cell i; Γ (i) is a set of downstream neighboring cells of cell i; l₀Is the standard cell length; l_iIs the length of the cell i, l_jIs the cell j length;the maximum number of vehicles that can flow into or out of cell i for a period t,the maximum number of vehicles that can flow into or out of cell j for a period t;the value of w/v of the cellular j in the period t, v is the free flow speed, and w is the back propagation speed in congestion;the maximum capacity of cell j for time period t;the flow on cell j for time period t.

Further, in S302, the vehicle route should be selected according to the evacuation plan, and the formula is as follows:

wherein m is_kThe number of vehicles arriving for each safety point; n is_lThe number of vehicles required for each evacuation point; gamma-shaped^-1(i) Is the upstream adjacent cell set of cell i; p represents an upstream neighboring cell of the cell i;the flow from cell p to cell i for a period of t; Γ (i) is a set of downstream neighboring cells of cell i; j represents a downstream neighboring cell of the cell i;the flow from cell i to cell j for a time period t; n is_iThe number of vehicles required by the cell i is the number of the vehicles required by the cell i, and the cell i is positioned at an evacuation point; c_eIs a set of cells representing evacuation points.

Further, in S302, a cost estimation function is established using the a-algorithm to optimize the path, where the estimation function is as follows:

F(i)＝G(i)+H(i) i∈C

wherein, F (i) represents the cost estimated value from the evacuation starting point to the cell i and then to the evacuation destination, G (i) represents the cost actual consumption value from the evacuation starting point to the cell i, and H (i) represents the cost estimated value from the cell i to the evacuation destination; c. C_i1Representing a predicted value of the distance from a cell i to an evacuation starting point; d_iRepresenting the distance from the cell i to the evacuation starting point; d_(i)maxRepresenting the maximum distance from the cell i to the evacuation starting point; c. C_i2Representing a predicted value of the distance from a cell i to an evacuation destination; s_iRepresenting the distance from the cell i to the evacuation destination; s_(i)maxRepresenting the maximum distance from the cell i to the evacuation destination; c. C_i3Representing a congestion degree estimated value of a cell i caused by existing vehicles in a road network; w_iThe number of the existing vehicles of the cell i is represented, and the vehicles do not comprise planned vehicles; n is a radical of_(i)maxRepresenting the number of vehicles which can be accommodated by the cell i at maximum; c. C_i4The estimated value of the crowdedness of the cell i caused by the z-1 planned vehicles when the next path of the z-th vehicle is planned at the time k is shown; sigma w_ziRepresenting the total number of planned vehicles that cell i has entered;denotes c_i1The coefficient of (a);denotes c_i2The coefficient of (a);denotes c_i3The coefficient of (a);denotes c_i4The coefficient of (a);

the optimized objective function is that the cost estimated value is minimum: min Z₂＝F(i)。

Further, the evaluation index includes travel time, delay time, parking time, average speed, and queuing condition of the evacuation vehicle.

Further, the evacuation bottleneck at S5 includes any one of a bottleneck of a road section, a bottleneck of an intersection, and a bottleneck of a traffic condition.

S501, a road section bottleneck can be realized by a reverse lane, including road sections and the number of lanes for realizing the reverse lane;

s502, intersection bottleneck, which can optimize intersection control, including canalization control and signal control;

s503, traffic road condition bottlenecks can control the social vehicles, reduce the right of passage of the social vehicles and ensure that the evacuation vehicles pass preferentially.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention has strong comprehensiveness and wide applicability. The vehicle emergency evacuation system integrates key technologies such as vehicle evacuation path selection, traffic simulation evaluation, evacuation bottleneck point diagnosis and the like, and can form a complete emergency evacuation planning method system. The invention can adapt to evacuation road networks under different scenes, thereby having stronger practicability.

(2) The vehicle many-to-many cycle evacuation process enriches evacuation scenes. The vehicle evacuation is suitable for the basic situation of high population and resource density in the city of China; the evacuation process from a plurality of vehicle parking points to a plurality of evacuation points and then to a plurality of safety points is suitable for increasingly complex evacuation scenes; the vehicles return to the evacuation point from the safety point to be evacuated circularly until all the people reach the safety point, and the condition that the evacuation vehicles are limited is considered. Naturally, the present invention is applicable to a situation simpler than the above scenario.

(3) The emergency evacuation system of the present invention takes into account traffic conditions and road carrying capacity when selecting vehicle evacuation paths. And the evacuation vehicles are induced to avoid possible traffic jam points, so that the situation that all the evacuation vehicles select the same shortest evacuation path to exceed the road bearing capacity to cause congestion is avoided, and the overall optimization is realized by minimizing the total evacuation time.

(4) The simulation deduction of the invention can immediately preview the evacuation process, and the potential evacuation bottleneck is found through quantitative evaluation indexes, thereby providing decision support for subsequent evacuation rescue.

Drawings

FIG. 1 is a flow chart of a city multi-point circulating emergency evacuation system based on variable cells;

FIG. 2 is a schematic diagram of variable cell partitioning;

FIG. 3 is a schematic diagram of a path of a vehicle traveling in a many-to-many cycle in an evacuation network;

fig. 4 is a flow chart of a-algorithm path selection of the fused cell transmission model;

FIG. 5 is an exemplary illustration of a visual simulation interface for evacuation process;

fig. 6 is a decision flow chart of setting a reverse lane for the evacuation road network.

Detailed Description

In order to more clearly illustrate the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

Fig. 1 is a flow chart of the present invention, and proposes a method for deriving urban multipoint circulating emergency evacuation and simulation based on variable cells, which comprises the following steps:

s1, initializing a traffic evacuation road network, designating a plurality of parking points, a plurality of evacuation points and a plurality of safety points, and acquiring traffic states.

Step S1 specifically includes the following substeps:

s101, determining an evacuation scene including an evacuation range, expected time, a vehicle running mode and the like;

in one embodiment of the invention, a plurality of parking points, a plurality of evacuation points and a plurality of safety points are designated in the selected evacuation range. Selected evacuation parameters include: evacuation population, vehicle capacity, number of vehicles required, vehicle free flow speed, back propagation speed in congestion, predetermined evacuation time, time interval. The designated evacuation process is: the vehicle departs from a plurality of parking points to a plurality of evacuation points, the person to be evacuated gets to a plurality of safety points after getting on the vehicle, and the vehicle is evacuated in a circulating way between the evacuation points and the safety points until all the persons are evacuated.

S102, defining static characteristic parameters of a road network;

in one embodiment of the present invention, the road network features include: the road section number, the total length of the road section, the change condition of the number of lanes of the road section, the number of intersections, the properties of the intersections (three-way intersection, crossroads and the like), and a signal timing scheme (signal phase and timing time). The road section is considered from the intersection a to the intersection b, and the road section is considered from the intersection b to the intersection a.

S103, acquiring the dynamic traffic flow state of the evacuation road network.

In one embodiment of the present invention, considering the influence of the traffic flow state of the road network on the vehicle path planning during evacuation, the traffic flow state of the road network is obtained and updated at a certain time interval, so that the evacuation vehicle avoids or at least partially passes through the congested road segment. The traffic flow state can be represented in any form of density, vehicle number and the like on the road section.

In one embodiment of the invention, it is difficult to obtain real-time traffic flow conditions within an evacuation area when an accident occurs suddenly, and even if it is obtained, it is not time to put the vehicle evacuation path into practice. The historical traffic flow status of the evacuation area is therefore used as the traffic flow status within the current evacuation network for planning the evacuation path of the vehicle.

And S2, mapping the actual road network and the evacuation scene to a virtual road network based on the variable cell transmission model.

Step S2 specifically includes:

s201, corresponding the attribute characteristics of an actual road section and an intersection to a virtual road network;

in one embodiment of the present invention, the actual road segments and intersections are numbered, and the road segments and intersections of the virtual road network are numbered. The virtual road network is divided into cells with variable lengths, so that static or dynamic characteristic parameters in the actual road network can be converted into attributes of the cells, and a basis is provided for solving evacuation paths and real-time simulation. Attributes of a cell include, but are not limited to: cell length, maximum number of vehicles that can flow into or out of the cell, maximum capacity of the cell, number of vehicles already in the cell, and number of the cell.

In one embodiment of the invention, the variable cellular is that the cellular length is variable, the variable cellular is used for adapting to the complex canalization condition of urban roads, the model precision is reduced when the cellular length is too large in difference, and the cellular length l_iWith a given standard cell length l₀The method comprises the following steps:

l₀≤l_i≤2l₀ (1)

the maximum number of vehicles Q that can flow into or out of the cells is determined by the design traffic capacity (pcu/h) of the one-way road segment:

Q＝N_a×N_b×N_c×N_d×T (2)

N_ato determine the traffic capacity (pcu/h) of the next lane at vehicle speed; n is a radical of_bThe road classification coefficient is the type of the lane; n is a radical of_cClassifying coefficients for the number of lanes; n is a radical of_dIs an intersection correction coefficient; t is the time interval(s).

The maximum capacity N of the unit cell satisfies:

N＝k_j×l_i×l_n (3)

k_jvehicle jam density (vehicle/km); l_nThe number of lanes corresponding to the cells.

In one embodiment of the present invention, the variable cell division is schematically shown in FIG. 2, where a given standard cell length l is set₀100m, the road section is divided into a plurality of small sections according to different lane numbers, and if the small sections do not satisfy the formula(1) Then divide the small section into several segments with length l₀A length of l_iIf the small segment satisfies formula (1), it is marked as a cell. And recording a preset vehicle steering proportion by taking the cell closest to the intersection entrance road as the last cell of the road section, wherein the number of actually steered vehicles is comprehensively determined by the steering proportion, the number of vehicles of the last cell and a signal lamp. And when the last cell has a vehicle needing to be steered and the phase operates in the valid green time, the vehicle turns to the first cell of other road sections.

S202, corresponding the attribute characteristic change of the evacuation scene to a virtual road network.

In one embodiment of the invention, the evacuation scenario is a many-to-many cycle evacuation of vehicles, which specifies a plurality of parking points in the virtual road network, points generated for vehicles; a plurality of evacuation points, which are points for evacuating people to get on the vehicle; and the plurality of safety points are points for evacuating people to get off the vehicle. Evacuation control measures such as reverse lane and intersection signal optimization implemented in an actual road network can be mapped into a virtual road network through cell attribute change.

S3, establishing a path selection model of vehicle many-to-many cycle evacuation, modeling, and performing parameter solution to obtain the evacuation path and the minimum evacuation time of the vehicle.

Step S3 specifically includes:

s301, problem description, wherein the actual emergency evacuation process is abstracted and represented by concise letters and parameters;

in one embodiment of the present invention, let G ═ (P, E, S, R). In the formula: p ═ P₁，P₂，…，P_m) Is a set of limited parking spots, E ═ E₁，E₂，…，E_n) Is a set of finite points to evacuate, S ═ S₁，S₂，…，S_q) R is a set of finite security points and R is a set of finite arcs in the network. The connection between them is shown in figure 3, the vehicle is from the parking lot to different evacuation points, and after the people to be evacuated get on the vehicle, the vehicle goes toAnd at a safety point, the vehicle returns to the parking lot after the whole evacuation process is finished.

S302, establishing a model, namely establishing a path selection model for vehicle many-to-many cycle evacuation with the minimum total evacuation time as a target;

in one embodiment of the present invention, the path selection model is built on the variable cell transmission model, so that the vehicle should follow the flow conservation formula of the cells when selecting the path, as follows:

wherein the content of the first and second substances,the flow on cell i is at time t;the flow rate on the cell i in the t-1 time period;the flow from cell p to cell i for a time period of t-1;the flow from cell i to cell j for a time period t;the flow from cell i to cell j for a time period of t-1; c represents a set of cells; gamma-shaped^-1(i) Is the upstream adjacent cell set of cell i; Γ (i) is a set of downstream neighboring cells of cell i; l₀Is the standard cell length; l_iIs the length of the cell i, l_jIs the cell j length;the maximum number of vehicles that can flow into or out of cell i for a period t,the maximum number of vehicles that can flow into or out of cell j for a period t;the value of w/v of the cellular j in the period t, v is the free flow speed, and w is the back propagation speed in congestion;the maximum capacity of cell j for time period t;the flow on cell j for time period t.

Equation (4) indicates that the number of vehicles in a cell at a certain time is equal to the number of vehicles in the cell at the previous time plus the number of vehicles entering the cell at the previous time and minus the number of vehicles exiting the cell. Equation (5) indicates that the vehicle flowing into cell j from cell i takes the minimum value among "the total number of vehicles that cell i can move to the next cell, the maximum outflow of cell i, the maximum inflow of cell j, and the remaining load-carrying capacity of cell j".

When the vehicle selects the route, the vehicle evacuation plan is followed, and the formula is as follows:

wherein m is_kFor each number of vehicles arriving at a safe point, k ═ m₁，m₂，…，m_m)，n_lThe number of vehicles required for each evacuation point, l ═ n₁，n₂，…，n_n)，C_eTo represent the cell set of the evacuation point, i.e. the formula (6) represents the arrival safetyThe total number of the evacuated vehicles of the points is equal to the total number of the vehicles required by the evacuation points, and the vehicles can reach the safety points by circularly evacuating for multiple times, so that the total number of the evacuated vehicles in the road network can be less than the total number of the vehicles required by the evacuation points;

Γ^-1(i) is an upstream neighboring cell set of cell i, p represents an upstream neighboring cell of cell i,for the traffic from cell p to cell i for the period t, Γ (i) is the set of downstream neighboring cells of cell i, j denotes the downstream neighboring cell of cell i,for a flow from cell i to cell j during a period t, n_iThe number of vehicles required by the cell i is the number of the vehicles required by the cell i, and the cell i is positioned at an evacuation point; c_eIs a set of cells representing evacuation points. That is, equation (7) shows how many vehicles are needed at each evacuation point, how many vehicles should be reached, and the vehicles must arrive at and leave the evacuation point.

The objective function is expressed asI.e. the sum of the flow rates of the cells over all time periods Z₁Minimum, the total evacuation time is determined by multiplying the total flow by the time interval (e.g., 10 s). Wherein C is_RIs a set of cells representing a parking spot and a safety spot.

In one embodiment of the present invention, the vehicle should follow the a-algorithm to optimize the route, and the use of the a-algorithm requires the establishment of an evaluation function, which is expressed as follows:

F(i)＝G(i)+H(i) i∈C (8)

h (i) represents a cost pre-estimated value from a cell i to an evacuation destination, A (i) the quality of the algorithm depends on whether the established H (i) function can accurately pre-estimate the cost from the cell i to the evacuation destination, F (i) represents a cost pre-estimated value from an evacuation starting point to the cell i to the evacuation destination, and G (i) represents an actual cost consumption value from the evacuation starting point to the cell i. c. C_i1Representing a predicted value of the distance from a cell i to an evacuation starting point; d_iRepresenting the distance from the cell i to the evacuation starting point; d_(i)maxRepresenting the maximum distance from the cell i to the evacuation starting point; c. C_i2Representing a predicted value of the distance from a cell i to an evacuation destination; s_iRepresenting the distance from the cell i to the evacuation destination; s_(i)maxRepresenting the maximum distance from the cell i to the evacuation destination; c. C_i3Representing a congestion degree estimated value of a cell i caused by existing vehicles in a road network; w_iThe number of the existing vehicles of the cell i is represented, and the vehicles do not comprise planned vehicles; n is a radical of_(i)maxRepresenting the number of vehicles which can be accommodated by the cell i at maximum; c. C_i4The estimated value of the crowdedness of the cell i caused by the z-1 planned vehicles when the next path of the z-th vehicle is planned at the time k is shown; sigma w_ziRepresenting the total number of planned vehicles that cell i has entered;denotes c_i1The coefficient of (a) is between 0 and 1;denotes c_i2At a coefficient ofTaking values between 0 and 1;denotes c_i3The coefficient of (a) is between 0 and 1;denotes c_i4The coefficient (b) is between 0 and 1.

The objective function is expressed as minZ₂F (i), that is, the cell that the vehicle z should reach at the time k +1 is determined according to the principle that the estimated cost value is the minimum.

Equation (9) shows that the cost estimate under consideration is divided into four aspects, and the summation is weighted according to different weights. The formula (10) indicates that the vehicle should select the cell j far away from the evacuation starting point as possible at the cell i as the next route. Equation (11) indicates that the vehicle should select the cell j as close to the evacuation end point as possible at the cell i as the next route. Equations (12) and (13) indicate that the vehicle should select the cell j with the small crowdedness as possible at the cell i as the next route.

And S303, solving the model to obtain the complete evacuation path and the minimum evacuation time of the vehicle.

In one embodiment of the present invention, the movement of traffic in the road network is described by the definition of the cellular transmission model, global path optimization is performed on each vehicle by the a-x algorithm, the evacuation paths of all vehicles can be combined into the traffic flow in the road network, and the flow of the path selection model formed by combining the two is shown in fig. 4.

Assuming that the predetermined evacuation time is k and the number of vehicles for evacuation is z, all the conditions are initialized when k is 0. When k is 1, firstly, z is 1, whether the z-th vehicle reaches the pre-intersection is judged, if not, the vehicle advances by the distance of one cell and the change of the cell attribute is recorded, and if yes, the next path planning is carried out according to the A-algorithm and the change of the cell attribute is recorded. And judging whether the path planning of all vehicles is finished, if not, moving all vehicles to a preset cellular according to the planned path, and if so, moving all vehicles to the preset cellular. And judging whether all vehicles reach the safety point, if not, updating the cell attributes in the road network according to the planning result determined at the k-th moment and the acquired road network traffic flow state, circulating the flow, and if so, ending the route selection and outputting the evacuation route and the evacuation time.

And S4, performing real-time simulation rehearsal evaluation on the evacuation path solved under the determined scene in the virtual road network to obtain a simulation result.

In one embodiment of the present invention, all the vehicle paths solved in step S3 are summarized and integrated into a limited number of paths, and a visual simulation is performed in the virtual road network to evaluate the traffic index condition of the evacuation road network in the whole evacuation process. The visual evacuation simulation is helpful for intuitively feeling the path selection result, and the quantitative evaluation index is helpful for analyzing the influence and possible defects of the evacuation path on the road network, so as to perform corresponding signal optimization and take necessary control measures.

In one embodiment of the invention, simulation evaluation is divided into two aspects of visualization simulation and evaluation index:

(1) and (6) visual simulation. The simulation process can record the change of the number of the evacuated vehicles in the road network at each moment and can record the change of the signal lamp state of the intersection. As shown in the simulation of fig. 5, the line segment corresponds to a road segment in the road network, the number on the road segment represents the number of vehicles, and the number of the square positions on the road segment represents the number of cells on the road segment; the circles correspond to the intersections and the numbers in the intersections in the road network, and the running conditions of the signal lamps are identified. In the embodiment, the road network simulation mainly reflects the running condition of the evacuation vehicle and does not reflect the attributes of the actual road network such as the length of the road section, the number of the lanes and the like. As shown in the simulation case when T is 2, 6 and 11 respectively indicate that there are 6 vehicles and 11 vehicles on the link; the road section of 6 vehicles is provided with 6 cells, and the road section of 11 vehicles is provided with 4 cells; the numbers above the circles indicate that the signals in the east-west direction are matched, the number 1 indicates that the east-west direction can be rotated to the left, the number 2 indicates that the east-west direction can be straightly moved, and the number 3 indicates that the east-west direction can be rotated to the right; the numbers below the circles indicate the timing of signals in the north-south direction, the number 1 indicates that the north-south direction can be rotated to the left, the number 2 indicates that the north-south direction can be moved straight, and the number 3 indicates that the north-south direction can be rotated only to the right.

(2) And (4) evaluating the index. The evaluation indexes comprise the travel time, delay time, parking time, average speed and queuing condition of the evacuation vehicle. The running condition of each vehicle at each moment is recorded in the simulation process, so that corresponding time and speed indexes are calculated, and the queuing condition of the vehicles at the intersection or the bottleneck can be obtained according to the recorded vehicle number change of the cells at each moment.

Since the evacuation path of each vehicle has been optimized with the goal of minimizing the evacuation time in step S3, step S4 further optimizes the evacuation process by taking evacuation control measures by searching for key points and bottleneck points from the perspective of the entire evacuation road network through real-time simulation.

S5, diagnosing whether an evacuation bottleneck exists according to the simulation result, and outputting an evacuation path and an evaluation index if the evacuation bottleneck does not exist; if the bottleneck exists, the steps S2-S4 are repeated until the evacuation bottleneck is eliminated or the evacuation target is reached.

In one embodiment of the present invention, the manner for diagnosing whether there is an evacuation bottleneck according to the simulation result is as follows: recording road section delay D_xlThe sum of the delay time of all the evacuating vehicles passing through the road section on the road section, the intersection delay D_ycDelay D for road sections forming the crossing_xlAnd (4) summing. When the road section is delayed D_xlIntersection delay D_ycRespectively exceed the set threshold value D_x0、 D_y0And when the evacuation target is not reached, the evacuation bottleneck is judged to exist. When an evacuation bottleneck exists, in the road section x, the intersection y adopts a reverse lane and a control measure for optimizing signal timing so as to reduce delay.

In one embodiment of the present invention, the potential evacuation bottlenecks of step S5 include road segment bottlenecks, intersection bottlenecks, and traffic bottlenecks. Wherein:

(1) when the evacuation bottleneck is a bottleneck of a road section, a reverse lane can be implemented, wherein the reverse lane comprises the road section and the number of lanes for implementing the reverse lane;

in the embodiment of the application, the conditions that traffic flow is blocked and the running is slow due to insufficient traffic capacity of partial road sections are considered, the reverse lane passing lane reverse is set to improve the traffic capacity of the road, the method is suitable for the condition that the reverse lane can be set under the comprehensive condition of the road, the road is a bottleneck road section, and the setting difficulty is where to set and set the lane reverse.

Fig. 6 shows a decision flow for setting a reverse lane for an evacuation road network, in which first, it is determined whether a bottleneck road section exists according to an evacuation route simulation result without a control measure, if not, a reverse lane is not set, and if so, it is determined whether an opposite road section meets a condition for setting a reverse lane. If not, no reverse lane is set, and if yes, the number r of the reverse lanes is set to be 1, namely, one lane is set as the reverse lane. Step S2 is executed to map the actual road network and the evacuation scene to the virtual road network based on the variable cellular transmission model, step S3 is executed to establish a route selection model of vehicle many-to-many cycle reciprocating evacuation and solve, step S4 is executed to perform real-time simulation preview evaluation on the evacuation route solved under the determined scene in the virtual road network, and when the optimization effect of the evacuation vehicle is greater than the deterioration effect of other vehicles, the position and the number of the lanes of the set reverse lane are output. If "no", the reverse lane number r is set to r +1, and steps S2 to S4 are performed. After the reverse lane is arranged, the original traffic organization mode of a road network is usually changed, and the evacuation operation efficiency can be controlled only by matching with the intersection. In this case, the intersection signal may be a green time for changing one or more phases, or may be a phase or phases that are cancelled.

(2) When the evacuation bottleneck is an intersection bottleneck, intersection control including canalization control and signal control can be optimized;

in the embodiment of the application, evacuation delay or congestion caused by improper control of the intersection is considered. The intersection control comprises conflict elimination and signal control, wherein the intersection conflict elimination belongs to canalization control, is often optimized in combination with a reverse lane and corresponds to the change of the road section attribute in the step S2; intersection signal control optimization is often embodied in adjusting the signal phase scheme and phase timing, corresponding to the change in intersection attributes in step S2.

(3) When the evacuation bottleneck is the traffic road condition bottleneck, the social vehicles can be managed and controlled, the right of way is reduced, and the evacuation vehicles are guaranteed to pass preferentially.

In the embodiment of the application, the situation that the evacuation efficiency of vehicles is reduced when too many social vehicles are in an evacuation road network or a part of evacuation road sections is considered, and the situation is called as a bottleneck of traffic road conditions. Social vehicles entering an evacuation road network can be reduced through the induction of a closed lane or a closed path, and the evacuation efficiency is improved.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.