A Traffic Flow Modeling Method for Global Path Planning

Abstract

The present invention is applicable to the technical field of traffic management, and provides a traffic flow modeling method for global path planning, comprising the following steps: using SUMO simulation software to establish a road network and traffic flow model: performing traffic flow generation, simulation parameter configuration and traffic flow model construction respectively, and then completing simulation output in SUMO software in combination with vehicle flow, simulation parameters and road network; establishing a SUMO / Matlab joint simulation platform: SUMO communicates through the TraCI interface to achieve joint simulation; establishing a road network mathematical model; generating a reachable path according to the road network mathematical model. The present invention uses simulation software to build a more realistic road network scene and traffic flow scene, and at the same time provides a road network mathematical model for global path planning, and builds a simulation platform through the TraCI communication interface, providing a simple and efficient method for subsequent path generation, which is suitable for promotion.

Description

Technical Field

[0001] The present invention belongs to the technical field of traffic management, and in particular relates to a traffic flow modeling method for global path planning. Background Art

[0002] With the development of information technology such as communication, sensing, and computing, and the continuous maturity of vehicle networking technology, vehicles, sensors, pedestrians, and traffic facilities are gradually integrated into a whole. Through terminal control, the interaction between individuals is realized to achieve the purpose of improving the load capacity and traffic efficiency of the road network. Traffic simulation is the process of using modern computer technology to simulate the real traffic system and establish a mathematical calculation model. It is an important technical approach for research in the field of transportation and the main means of current research on intelligent connected vehicle technology. According to the difference in model size, traffic simulation models mainly include macro models, micro models, and meso models. The objects of the macro model are mainly integrated traffic variables, such as traffic flow, vehicle density, average speed, etc.; the micro model studies traffic dynamics from the perspective of individual drivers. The driver's behavior includes following the car, changing lanes, and route selection. The movement of each vehicle in the simulation model generally assumes that the vehicle behavior depends on both the physical properties of the vehicle and the control behavior of the driver.

[0003] Carrying out research and testing of the Internet of Vehicles in real scenarios requires a lot of manpower, material resources and financial resources, and the safety of personnel cannot be guaranteed. Therefore, most of the current research on Internet of Vehicles technology is conducted through computer software simulation technology. The existing simulation technology has matured in the development of vehicle dynamics and kinematics modeling, but lacks a modeling method for simulating real traffic flow. Existing traffic simulation models have certain limitations in obtaining road information in real time. The mathematical model of the road network based on path planning cannot fully include the individual information in the road network and the relationship between individuals. For this reason, we propose a traffic flow modeling method for global path planning. Summary of the invention

[0004] The purpose of the present invention is to provide a traffic flow modeling method for global path planning, aiming to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A traffic flow modeling method for global path planning includes the following steps:

[0007] Step S1, using SUMO simulation software to establish a road network and traffic flow model: generate traffic flow, configure simulation parameters and build a traffic flow model, and then complete the simulation output in SUMO software by combining traffic flow, simulation parameters and road network;

[0008] Step S2, establishing a SUMO / Matlab joint simulation platform: SUMO communicates through the TraCI interface to achieve joint simulation, and the TraCI interface uses the Matlab language;

[0009] Step S3, establishing a road network mathematical model;

[0010] Step S4: Generate a reachable path based on the road network mathematical model.

[0011] Furthermore, the specific operations of step S1 are:

[0012] a. Perform road network selection: select a road network area in the open source map, and export an editable road network file based on the road network area;

[0013] b. Complete map editing: edit and repair editable road network files;

[0014] c. Set the road network parameters: number the road network elements in order.

[0015] Furthermore, in step S2, SUMO includes a controller; Matlab includes a traffic data acquisition module and an optimization solution module.

[0016] Furthermore, the specific operations of step S2 are:

[0017] The traffic data acquisition module in Matlab obtains the data of road network elements from the traffic flow model through the TraCI.get series functions and inputs it into the optimization scheme module. After obtaining the optimization results, the controller controls the target vehicle through the TraCI.set series functions to form a closed-loop control.

[0018] Furthermore, the specific operations of step S3 are:

[0019] Assumptions N are all drivable branches in the target area, the starting branch is 1, and the end branch is N ; Define the matrix is the relationship between the branches;

[0020] Among them, the matrix elements is a variable, indicating a branch i To branch road j Passability: If the branch i and branch roads j connected, and vehicles can directly take the branch road i Drive to the bypass j ,but Equal to branch i The number of the traffic intersection pointed to, otherwise is equal to 0.

[0021] Furthermore, the specific operations of step S4 are:

[0022] The current position of the target vehicle is recorded as , the target position is recorded as ;

[0023] The set of reachable paths is denoted as , the reachable path is represented by an array, recorded as , the target vehicle is on the road When , extract the matrix No. The vertical coordinates of the non-zero elements of a row are labeled ,Right now For the road A collection of passable branches;

[0024] like If it is an empty set, a new cycle starts again;

[0025] like Not an empty set, randomly selected An element in ,like Not present If it does not appear in , select the element For the collection middle The next element is recorded as ;like exist Appeared in Clear the element and select the next element at random;

[0026] When The selected branch is When for When , the loop ends and the reachable path is output ;remember is a set of reachable paths, if There is no The same elements, Merge into middle.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention uses simulation software to build more realistic road network scenarios and traffic flow scenarios, and provides a road network mathematical model for global path planning. As well as building a simulation platform through the TraCI communication interface, it not only constructs reasonable macro traffic information such as traffic flow speed, but also can obtain real-time micro traffic information such as vehicle speed, position, and traffic lights, and provides a simple and efficient method for subsequent path generation, which is suitable for promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the present invention.

[0030] Figure 2 This is a flow chart of traffic simulation in SUMO of the present invention.

[0031] Figure 3 It is the real road network in the open source map of the present invention.

[0032] Figure 4 This is a simple road network constructed in SUMO of the present invention.

[0033] Figure 5 This is the traffic flow generated with a frequency of 0.2 under the simple road network of the present invention.

[0034] Figure 6 This is the traffic flow generated with a frequency of 0.1 under the simple road network of the present invention.

[0035] Figure 7 This is the traffic flow generated with a frequency of 0.2 under the real road network of the present invention.

[0036] Figure 8 This is the traffic flow generated with a frequency of 0.1 under the real road network of the present invention.

[0037] Fig. 9 This is a schematic diagram of the joint simulation in the present invention.

[0038] Fig.10 This is a simplified model of a simple road network of the present invention.

[0039] Fig.11 Generate a reachable path flow chart for the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0042] like Figure 1As shown, a traffic flow modeling method for global path planning provided by an embodiment of the present invention includes the following steps:

[0043] Step S1: Use SUMO simulation software to establish a road network and traffic flow model: generate traffic flow, configure simulation parameters and build traffic flow model according to the needs, and then complete the simulation output in SUMO software by combining traffic flow, simulation parameters and road network (see Figure 2 );

[0044] Step S2, establishing a SUMO / Matlab joint simulation platform: SUMO communicates through the TraCI interface to achieve joint simulation, and the TraCI interface uses the Matlab language;

[0045] Step S3, establishing a road network mathematical model;

[0046] Step S4: Generate a reachable path based on the road network mathematical model.

[0047] As a preferred embodiment of the present invention, the specific operation of step S1 is:

[0048] a. Select the road network: select a road network area with many main roads, clear and crisscross layout, and reasonable density of traffic lights in the open source map, and extract the area to export an editable road network file;

[0049] b. Complete map editing: edit and repair the editable road network file, such as modifying the size, repairing the road, deleting irrelevant equipment, adding or removing constraints, etc., removing the pedestrian non-motorized vehicle lanes, and retaining the main roads accessible to motor vehicles, so that it can meet the modeling requirements;

[0050] c. Set road network parameters: number road networks elements such as roads, intersections, sensors, and traffic lights in an orderly manner.

[0051] In the embodiment of the present invention, by Figure 3 and Figure 4 It can be seen that the number of vehicles at the initial time and the end time is 0, and the traffic flow in the road network is similar to the normal distribution. This distribution is used to simulate the traffic flow in a real road network over a period of time. Figure 3 ) and the simple road network built in SUMO (such as Figure 4 ) Generate traffic flow with "frequency within 0~100 seconds is 0.2" and "frequency within 0~100 seconds is 0.1".

[0052] in, Figure 5 This is the result of generating vehicles with a frequency of 0.2 (with a vehicle generation cycle of 1 second and 5 vehicles generated per second) within 0 to 100 seconds on a simple road network. Figure 6This is the result of generating vehicles with a frequency of 0.1 (1 second as the vehicle generation cycle and 10 vehicles per second) within 0 to 100 seconds on a simple road network. Figure 7 This is the result of generating vehicles with a frequency of 0.2 (with a vehicle generation cycle of 1 second and 5 vehicles generated per second) within 0 to 100 seconds on a real road network. Figure 8 This is the result of generating vehicles at a frequency of 0.1 (with 1 second as the vehicle generation cycle and 10 vehicles generated per second) within 0 to 100 seconds on a real road network.

[0053] By comparison, it can be seen that no matter in a real road network or a simple road network, the above method can simulate the traffic flow model of the total number of vehicles in the road network that changes over time and approximates the Poisson distribution, thereby simulating the total number of vehicles in the real traffic flow.

[0054] As a preferred embodiment of the present invention, in step S2, SUMO includes a controller; Matlab includes a traffic data acquisition module and an optimization scheme module; the optimization scheme module can generate several paths based on the acquired real-time traffic information, the vehicle's current location information and the destination, and apply the reachable path generation rules; then solve the vehicle's global "optimal" driving path according to the preset algorithm in the optimization scheme module.

[0055] The specific operations of step S2 are:

[0056] The traffic data acquisition module in Matlab obtains data of road network elements such as roads, intersections, sensors, and traffic lights from the traffic flow model through the TraCI.get series of functions, and inputs them into the optimization scheme module. After obtaining the optimization results, the controller controls the target vehicle through the TraCI.set series of functions to form a closed-loop control (see Fig. 9 ).

[0057] In an embodiment of the present invention, SUMO as a traffic simulation software can realize the simulation of many actual traffic scenes. When SUMO is used as a test platform for intelligent traffic control algorithms, there is a need for two-way communication with the optimization scheme. The user-defined optimization scheme can obtain real-time traffic information from SUMO, and then control variables such as vehicle speed in real time. The data in the SUMO traffic simulation environment can be obtained through the TraCI interface, and real-time modification and control can be performed. At present, the interface supports a variety of mainstream languages, including python, C++, .NET, MATLAB and Java. The Matlab language is selected in the present invention, and the TraCI4Matlab function used is shown in Table 1.

[0058] Table 1 TraCI4Matlab function

[0059]

[0060] As a preferred embodiment of the present invention, in step S2, the present invention realizes bidirectional communication by combining SUMO and TraCI, and obtains a large amount of data from the traffic flow model through the TraCI.get series of functions, but it is difficult to efficiently process the data obtained through TraCI to obtain a description of the relationship between roads in the entire road network. In order to quickly generate multiple reachable paths and realize an intuitive description of the relationship between road networks in Matlab, the present invention establishes a mathematical model of the road network, which is expressed by a two-dimensional matrix.

[0061] Similar to other path planning studies, the traffic network can be simplified into nodes and branches. Nodes represent intersections or forks, and branches represent the passable sections between nodes. Fig.10 As an example, the figure shows a simplified node-branch model. Arrows indicate the direction of vehicle travel. Numbers correspond to numbers. ①~⑨ represent intersections 1 to 9. The starting point and the end point are diagonal roads "1-26" respectively. Determine the target area. Assume N are all drivable branches in the target area, the starting branch is 1, and the end branch is N ; Define the matrix is the relationship between the branches; among them, the element is a matrix variable, representing the branch i To branch road j Passability: If the branch i and branch roads j connected, and vehicles can directly take the branch road i Drive to the bypass j ,but Equal to branch i The number of the traffic intersection pointed to, otherwise is equal to 0.

[0062] In the embodiment of the present invention, Fig.10 Take the branch road 13 in the figure as an example. The branch road 13 can go straight, turn right, turn left, and make a U-turn. That is, the road 13 is connected with the branch roads 12, 15, 9, and 18 through the intersection 5. Fig.10 middle G The 13th row of is [0 0 0 0 0 0 0 0 5 0 0 5 0 0 5 0 0 5 0 0 0 0 0 0 0], with a total of 26 dimensions, of which the 9th, 12th, 15th and 18th elements are 5, and the rest are 0.

[0063] As a preferred embodiment of the present invention, the specific operation of step S4 is:

[0064] According to the above road network mathematical model and "starting point-end point", the current position of the target vehicle is recorded as , the target position is recorded as . Road network matrix Describes the connection relationship between branches. In order to ensure the rationality of generating accessible paths, "each road can be passed at most once" is used as a constraint, such as Fig.11 The specific process is as follows:

[0065] The set of reachable paths is denoted as , the reachable path is represented by an array, recorded as , the target vehicle is on the road When , extract the matrix No. The vertical coordinates of the non-zero elements of a row are labeled ,Right now For the road A collection of passable branches;

[0066] like If it is an empty set, a new cycle starts again;

[0067] like Not an empty set, randomly selected An element in ,like Not present If it does not appear in , select the element For the collection middle The next element is recorded as ;like exist Appeared in Clear the element and select the next element at random;

[0068] When The selected branch is When for When , the loop ends and the reachable path is output ;remember is a set of reachable paths, if There is no The same elements, Merge into According to the above method, several reachable paths can be obtained when the "starting point-end point" is known.

[0069] The above are only preferred embodiments of the present invention. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These should also be regarded as the protection scope of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A traffic flow modeling method for global path planning, characterized in that: The following steps are involved: Step S1, using SUMO simulation software to establish a road network and traffic flow model: generate traffic flow, configure simulation parameters and build a traffic flow model, and then complete the simulation output in SUMO software by combining traffic flow, simulation parameters and road network; Step S2, establishing a SUMO / Matlab joint simulation platform: SUMO communicates through the TraCI interface to achieve joint simulation, and the TraCI interface uses the Matlab language; Step S3, establishing a road network mathematical model; Step S4, generating a reachable path according to the road network mathematical model; In step S2, SUMO includes a controller; Matlab includes a traffic data acquisition module and an optimization solution module; The specific operations of step S2 are: The traffic data acquisition module in Matlab obtains the data of road network elements from the traffic flow model through the TraCI.get series functions and inputs them into the optimization scheme module. After obtaining the optimization results, the controller controls the target vehicle through the TraCI.set series functions to form a closed-loop control. The specific operations of step S3 are: Assume that N is the drivable branch of all target areas, the branch where the starting point is located is 1, and the branch where the end point is located is N; define the matrix G = {g ij } N×N is the relationship between the branches; Among them, the matrix element g ij is a variable, indicating the passability from branch i to branch j: if branch i is connected to branch j, and the vehicle can travel directly from branch i to branch j, then g ij is equal to the number of the traffic intersection pointed to by branch i, otherwise g ij is equal to 0; The specific operations of step S4 are: The current position of the target vehicle is recorded as a0, and the target position is recorded as a E ; The reachable path set is denoted as B, and the reachable path is represented by an array as A = {a0, a1, ..., a E }, when the target vehicle is on road a0, the vertical coordinates of the non-zero elements of the a0th row of matrix G are extracted and marked as That is, w1, w2, ..., w i is the set of accessible branches of road a0; like If it is an empty set, a new cycle starts again; like Not an empty set, randomly selected An element w in i , if w i If it has not appeared in A, then select the element w i is the element after a0 in set A, denoted as a1; if w i Appeared in A, from Clear the element and select the next element at random; When the nth cycle, the selected branch is a E When n for a E When , the loop ends and the output reaches path A; let B = {A1, A2, ..., A m } is a set of reachable paths. If there is no element in B that is the same as that in A, then A is merged into B; In step S4, a constraint is imposed on the achievable path: each road can be passed at most once.

2. The traffic flow modeling method for global path planning according to claim 1, characterized in that: The specific operations of step S1 are: a. Perform road network selection: select a road network area in the open source map, and export an editable road network file based on the road network area; b. Complete map editing: edit and repair editable road network files; c. Set the road network parameters: number the road network elements in order.

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