A highway vehicle platoon control and merging simulation method

Abstract

The present invention provides a method for simulating a vehicle formation control and merging on a highway, comprising the following steps: S1, a ramp vehicle broadcasts a message during ramp driving; S2, a roadside unit integrates the position and speed information of the ramp vehicle closest to the intersection merging point with the position coordinates of the roadside unit and broadcasts it; S3, in a simulation program environment, a main road vehicle instance is generated according to a predefined vehicle formation generation logic; a vehicle formation control is performed on the vehicles predetermined as an automatic driving formation, the acceleration of the leading vehicle is adjusted by controlling the spacing, and the following vehicles follow the IDM model to form a vehicle formation; S4, the main road vehicle formation merges with the ramp vehicle according to the control logic. By controlling the deceleration of the main road vehicles, the main road vehicles can make appropriate adjustment behaviors according to the driving conditions of the ramp vehicles when approaching the intersection area, thereby improving the smoothness and safety of road traffic.

Description

Technical Field

[0001] The invention relates to the field of intelligent transportation systems, and in particular to a highway vehicle formation control and merging simulation method. Background Art

[0002] With the continuous growth of global car ownership and the acceleration of urbanization, the demand for road traffic continues to rise, and traffic congestion and accident risks have become increasingly serious problems. Against this background, intelligent transportation systems (ITS) have emerged, which use advanced communication technologies, vehicle control strategies and traffic management methods to improve road traffic efficiency, safety and sustainability. However, although intelligent transportation systems have achieved remarkable results in many aspects, they still face some challenges in the merging area of ​​highways.

[0003] Traditional traffic management methods have limitations in the application of highway merging areas, such as difficulty in speed coordination between ramp and main road vehicles and inaccurate distance control during merging. These problems may lead to increased traffic congestion and even potential traffic accidents. Therefore, it is necessary to develop a highway vehicle platoon control and merging simulation solution based on a cloud control platform to solve these problems and improve the performance of the entire traffic system. Summary of the invention

[0004] The present invention aims to provide a highway vehicle formation control and merging simulation method to solve the above problems.

[0005] The technical solution of the present invention is: a highway vehicle formation control and merging simulation method, comprising:

[0006] S1, while driving on the ramp, the ramp vehicle combines its own vehicle position and speed information into a message and broadcasts the message with a time granularity of 0.5s;

[0007] S2, the roadside unit (RSU) receives the messages broadcast by ramp vehicles through the IEEE 802.11p interface, integrates the messages, extracts the position and speed information of the ramp vehicle closest to the intersection merging point, and encapsulates it together with the position coordinates of the roadside unit (RSU) into a new message and broadcasts it at a time granularity of 1 second;

[0008] S3, in the simulation program environment, generate a main road vehicle instance according to the predefined vehicle formation generation logic. The vehicle instance types include a vehicle formation consisting of three autonomous driving networked vehicles and other vehicles except the vehicle formation. Among them, the other vehicles except the vehicle formation are background traffic flow. The vehicle formation includes the head vehicle of the formation and the following vehicles in the formation. After the main road vehicles are generated, enter the vehicle formation stage, perform vehicle formation control on the vehicles pre-determined as the autonomous driving formation, adjust the acceleration of the head vehicle by controlling the spacing, and the following vehicles adopt the IDM model to follow and form a vehicle formation.

[0009] S4: After the main road vehicle formation is formed, it travels on the main road according to the formation mode until it enters the merging stage. After the head vehicle of the vehicle formation receives the message broadcast by the roadside unit (RSU), it determines whether it needs to slow down and performs deceleration control according to the defined deceleration logic. At the same time, the non-head vehicles of the formation follow and merge with the vehicles on the ramp.

[0010] Preferably, the specific steps of step S2 include:

[0011] S21, when the ramp vehicle is driving, it broadcasts its own position to the surrounding area at a certain interval through the networked wireless channel, so as to realize communication and coordination between ramp vehicles; after the roadside unit (RSU) receives the position and speed information of the ramp vehicle, it predicts and judges the running trajectory of the ramp vehicle through the ramp curve equation, so as to issue control decisions for vehicle merging; before the formal simulation begins, a pre-simulation is performed to let the ramp vehicle output its own position every 0.1s, and the discrete coordinate points of the ramp curve are obtained according to the position coordinates. The ramp curve is fitted with a cubic polynomial function to obtain the curve equation:

[0012] y=1.577577312e -7 x 3 -0.002335491864x 2 +11.52445032x-18954.3547 (1)

[0013] In formula (1), x and y represent the x-axis and y-axis of the top view of the ramp curve, respectively;

[0014] S22, after receiving the message broadcast by the ramp vehicle, the roadside unit (RSU) calculates the distance between the ramp vehicle and the intersection merging point based on the ramp curve equation, the curve arc length formula and the definite integral trapezoidal formula, and extracts the position and speed information of the vehicle closest to the intersection merging point on the ramp;

[0015]

[0016] Formula (2) is the arc length formula of the curve, s is the arc length of the curve, dx is the differential element of the x-axis variable, and y' is the first-order derivative of y;

[0017] Formula (3) is the definite integral trapezoidal formula, where a and b are the upper and lower limits of the integral, n is the number of equally divided trapezoids, and f(x) is the integrand.

[0018] Preferably, the specific steps of step S3 include:

[0019] S31, generation of predefined vehicle formation and background traffic flow;

[0020] S32, during the vehicle formation process, a vehicle formation control event is scheduled through a self-message with a small sending interval, and different behaviors are performed for different types of vehicles.

[0021] Preferably, the specific steps of step S31 include:

[0022] The formation of vehicle formation and background traffic flow is based on the pre-set vehicle type array vehTypeArray, and the array elements may take values ​​0, 1, 2, 3;

[0023] Among them, 0 represents that the vehicle is in the background traffic flow, 1, 2, and 3 represent the leading vehicle and the following vehicle of the three-vehicle formation respectively; when the vehicle is initialized, the attribute vehType is added to the vehicle to mark the vehicle.

[0024] Preferably, the specific steps of step S32 include:

[0025] ① The leading vehicle in a platoon: vehType is 1; if there is no other vehicle within 80m ahead of the vehicle, it will drive freely; otherwise, it needs to maintain a safe distance from the vehicle ahead;

[0026] First, obtain the module ID of the preceding vehicle, and obtain the position p of the preceding vehicle based on the module application layer. front and speed information v front , calculate the expected speed of the leading vehicle in the vehicle formation according to the following formula:

[0027]

[0028] In formula (4), dist(·) represents the distance between two points on the curve, v desire is the expected speed of the current vehicle, t adjust is the spacing adjustment time, s obj is the expected distance from the vehicle ahead;

[0029] Since the time granularity of the adjustment interval is small, it is assumed that the vehicle ahead maintains a constant speed within the adjustment interval. The expected acceleration of the current vehicle in the platooning phase is:

[0030]

[0031] In formula (5), v0 is the current speed of the vehicle;

[0032] At the same time, the vehicle must meet the maximum acceleration and maximum deceleration limits, so the expected acceleration of the vehicle in the formation phase needs to be corrected to:

[0033]

[0034] In formula (6), and They represent the maximum acceleration and maximum deceleration of vehicle braking respectively; the leading vehicle on the main road at time t adjust By adjusting its own acceleration, it can achieve the desired distance with the vehicle in front.

[0035] Formulas (4)-(6) describe the control logic of the leading vehicle in the vehicle platooning stage. The driving state of the leading vehicle affects the following vehicles in the platoon and controls the driving state of the entire platoon. It controls the driving behaviors between vehicle platoons and between vehicle platoons and background traffic flows, and finally forms a vehicle platoon.

[0036] ② Following vehicle in the vehicle formation: vehType is 2 or 3; the following behavior of the following vehicle is controlled by the IDM motion equation:

[0037]

[0038] In formulas (7)-(8), α is the sensitivity coefficient, v is the current speed of the vehicle, and v max is the maximum speed of the vehicle, s * (·) is the expected minimum vehicle distance, Δv is the speed difference between the vehicle and the front vehicle, Δx is the distance between the vehicle and the front vehicle, s0 is the minimum vehicle distance, T s is the safe headway, a m is the maximum acceleration, b n is the expected deceleration;

[0039] S33, background traffic flow: vehType is 0; the background traffic flow is other vehicles on the main road except the vehicle formation. Their behavior is not actively changed during the simulation and is managed by the SUMO vehicle controller TraCI.

[0040] Preferably, the specific steps of step S4 include:

[0041] S41, control of the leading vehicle during the merging phase;

[0042] After the leading vehicle in the main road vehicle formation receives the broadcast information from the roadside unit (RSU), it first determines whether the leading vehicle has reached the intersection merging point within 50m. If it has reached the range, it will slow down according to the merging principle.

[0043] Main road vehicle merging principle: In order to avoid collision between main road vehicles and ramp vehicles, the main road vehicle formation should slow down appropriately and keep a certain safe distance from the ramp vehicles when approaching the intersection merging point to ensure the safety and stability of the merging; according to the position and speed of the ramp vehicle closest to the intersection merging point, as well as the position and speed of the current vehicle, the acceleration of the leading vehicle of the main road vehicle formation during the merging stage is determined as:

[0044]

[0045] Among them, v1 and s1 are the speed of the ramp vehicle closest to the intersection merging point and the distance from the intersection, v2 and s2 are the speed of the leading vehicle in the main road vehicle formation and the distance from the intersection merging point, and s0 is the safe distance between the leading vehicle in the main road vehicle formation and the ramp vehicle;

[0046] S42, by using formula (9) to control the deceleration of the main road vehicle, the main road vehicle can make appropriate adjustments according to the driving conditions of the ramp vehicle when approaching the intersection area, thereby improving the smoothness and safety of road traffic; in this process, the main road vehicle can dynamically adjust its own speed and driving distance by receiving and analyzing the real-time information transmitted by the ramp vehicle.

[0047] The beneficial effects of the present invention are:

[0048] By decelerating the main road vehicles, the main road vehicles can make appropriate adjustments according to the driving conditions of the ramp vehicles when approaching the intersection area, thereby improving the smoothness and safety of road traffic. In this process, the main road vehicles can dynamically adjust their own speed and driving distance by receiving and analyzing the real-time information transmitted by the ramp vehicles. This method helps the main road vehicles to leave appropriate merging space for ramp vehicles without affecting their own speed, reducing the potential risk of traffic accidents caused by speed uncoordination during the merging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A method for platoon control and merging simulation of vehicles on a highway provided by an embodiment of the present invention; a framework design diagram involved in the method of the present invention;

[0050] Figure 2 A simplified control flow chart of a highway vehicle formation control and merging simulation method provided by an embodiment of the present invention;

[0051] Figure 3 A functional schematic diagram of component modules of a highway vehicle platoon control and merging simulation method provided by an embodiment of the present invention;

[0052] Figure 4A simplified diagram of a road traffic network model in a highway vehicle formation control and merging simulation method provided by an embodiment of the present invention;

[0053] Figure 5 A traffic efficiency graph obtained by calculating a simulation log in a highway vehicle formation control and merging simulation method provided by an embodiment of the present invention;

[0054] Figure 6 A speed standard deviation graph obtained by calculating a simulation log in a highway vehicle formation control and merging simulation method provided by an embodiment of the present invention;

[0055] Figure 7 A collision event (TTC) diagram of a vehicle and a preceding vehicle calculated from a simulation log in a highway vehicle formation control and merging simulation method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0056] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. The implementation methods of the present invention are not limited thereto.

[0057] Example 1

[0058] like Figure 1 As shown in the figure, it is the framework design diagram involved in the present invention. First, the mixed traffic flow is generated by initializing the following distance within the vehicle formation and between the formations and the traffic flow ratio. The ramp vehicle packages its own position and speed information and transmits it to the RSU, which then broadcasts this information. After receiving the broadcast information from the RSU, the main road vehicle makes a judgment and decelerates if the set logic is met. Finally, the simulation results are evaluated from the three aspects of safety, efficiency, and stability.

[0059] like Figure 2 The control flow chart of the present invention is shown in FIG. The main road section to be controlled is divided into a formation adjustment area and a deceleration area.

[0060] like Figure 3 The figure shows the functional diagram of the component modules involved in the present invention. The ramp vehicle module needs to send its own position and speed information to the RSU. The RSU module needs to extract the position and speed information of the first vehicle on the ramp and broadcast it. The main road vehicle module needs to receive the broadcast information from the RSU and decelerate if the deceleration logic is met.

[0061] like Figure 4 Shown is a simplified diagram of the road traffic network model involved in the present invention.

[0062] Figure 4It is a converging road network at a certain intersection. The vehicle formation in the mixed traffic flow of the main road: the background traffic flow = 3:1. The vehicle parameters are shown in Table 1

[0063]

[0064] Table 1

[0065] The above simulation scheme is based on OmNet++, Veins, and SUMO joint simulation to output simulation logs and calculate evaluation indicators.

[0066] like Figure 5 As shown in the figure, it is a comparison of the changes of highway traffic efficiency with simulation time under different fleet following distances. Highway traffic efficiency refers to the traffic volume completed on the highway section per unit time, which can be expressed as the product of traffic flow and average vehicle speed per unit time. It can be seen from the figure that when the simulation time is less than 300s, as the simulation time increases, the number of vehicles passing through the merging point is gradually increasing, and the traffic efficiency is also steadily increasing; when the simulation time is greater than 300s, the number of vehicles passing through the merging point is close to saturation, and the traffic efficiency tends to be stable and there is a slight decrease, which shows that the deceleration behavior of the fleet at the merging point has a certain impact on the overall traffic efficiency of the highway.

[0067] like Figure 6 As shown in the figure, the comparison of the speed standard deviation of mixed traffic flow with simulation time under different convoy following distances is shown. The speed standard deviation of mixed traffic flow is used to reflect the degree of dispersion of vehicles in mixed traffic flow and characterize the driving stability of traffic flow. As can be seen from the figure, the speed standard deviation fluctuates to a certain extent at any following distance. When the following distance is small, the speed standard deviation fluctuates less with the increase of simulation time, indicating that the acceleration control between convoys is relatively smooth and the traffic flow can be kept in a steady state; when the following distance is large, the speed standard deviation fluctuates more, which is not conducive to the coordinated control between convoys and the traffic flow state is unstable.

[0068] like Figure 7 The figure shows the comparison of the time to collision (TTC) with simulation time under different following distances of different fleets. TTC refers to the time required for the rear vehicle to continue to travel and collide with the front vehicle when the front and rear vehicles do not change their driving speed at a certain moment. It is equal to the ratio of the following distance to the relative speed. As can be seen from the figure, TTC fluctuates to a certain extent at any following distance. When the following distance is small, the vehicle needs to adjust the speed in time; when the following distance is large, the adjustment time and space are larger.

[0069] Those skilled in the art can understand that the accompanying drawings are only schematic diagrams of an embodiment, and the processes in the accompanying drawings are not necessarily required to implement the present invention.

Claims

1. A highway vehicle formation control and merging simulation method, characterized in that: The steps include: S1, while driving on the ramp, the ramp vehicle combines its own vehicle position and speed information into a message and broadcasts the message with a time granularity of 0.5s; S2, the roadside unit (RSU) receives the messages broadcast by ramp vehicles through the IEEE 802.11p interface, integrates the messages, extracts the position and speed information of the ramp vehicle closest to the intersection merging point, and encapsulates it together with the position coordinates of the roadside unit (RSU) into a new message and broadcasts it at a time granularity of 1 second; S3, in the simulation program environment, generate a main road vehicle instance according to the predefined vehicle formation generation logic. The vehicle instance types include a vehicle formation consisting of three autonomous driving networked vehicles and other vehicles except the vehicle formation. Among them, the other vehicles except the vehicle formation are background traffic flow. The vehicle formation includes the head vehicle of the formation and the following vehicles in the formation. After the main road vehicles are generated, enter the vehicle formation stage, perform vehicle formation control on the vehicles pre-determined as the autonomous driving formation, adjust the acceleration of the head vehicle by controlling the spacing, and the following vehicles adopt the IDM model to follow and form a vehicle formation. S4: After the main road vehicle formation is formed, it drives on the main road in the formation mode until it enters the merging stage. After the leading vehicle of the vehicle formation receives the message broadcast by the roadside unit (RSU), it determines whether it needs to slow down and performs deceleration control according to the defined deceleration logic. At the same time, the non-leading vehicles of the formation follow and merge with the vehicles on the ramp. The specific steps of step S2 include: S21, when the ramp vehicle is driving, it broadcasts its own position to the surrounding area at a certain interval through the networked wireless channel, so as to realize communication and coordination between ramp vehicles; after the roadside unit (RSU) receives the position and speed information of the ramp vehicle, it predicts and judges the running trajectory of the ramp vehicle through the ramp curve equation, so as to issue control decisions for vehicle merging; before the formal simulation begins, a pre-simulation is performed to let the ramp vehicle output its own position every 0.1s, and the discrete coordinate points of the ramp curve are obtained according to the position coordinates. The ramp curve is fitted with a cubic polynomial function to obtain the curve equation: y=1.577577312e -7 x 3 -0.002335491864x 2 +11.52445032x-18954.3547 (1) In formula (1), x and y represent the x-axis and y-axis of the top view of the ramp curve, respectively; S22, after receiving the message broadcast by the ramp vehicle, the roadside unit (RSU) calculates the distance between the ramp vehicle and the intersection merging point based on the ramp curve equation, the curve arc length formula and the definite integral trapezoidal formula, and extracts the position and speed information of the vehicle closest to the intersection merging point on the ramp; Formula (2) is the arc length formula of the curve, s is the arc length of the curve, dx is the differential element of the x-axis variable, and y' is the first-order derivative of y; Formula (3) is the definite integral trapezoidal formula, where a and b are the upper and lower limits of the integral, n is the number of equally divided trapezoids, and f(x) is the integrand.

2. A highway vehicle formation control and merging simulation method according to claim 1, characterized in that: The specific steps of step S3 include: S31, generation of predefined vehicle formation and background traffic flow; S32, during the vehicle platooning process, a self-message with a small sending interval is used to schedule the vehicle platooning control event, and different behaviors are performed for different types of vehicles.

3. A highway vehicle formation control and merging simulation method according to claim 2, characterized in that: The specific steps of step S31 include: The formation of vehicle formation and background traffic flow is based on the pre-set vehicle type array vehTypeArray, and the array element values ​​are 0, 1, 2, 3; Among them, 0 represents that the vehicle is in the background traffic flow, 1, 2, and 3 represent the leading vehicle and the following vehicle of the three-vehicle formation respectively; when the vehicle is initialized, the attribute vehType is added to the vehicle to mark the vehicle.

4. A highway vehicle formation control and merging simulation method according to claim 2, characterized in that: The specific steps of step S32 include: ① The leading vehicle in a platoon: vehType is 1; if there is no other vehicle within 80m ahead of the vehicle, it will drive freely; otherwise, it needs to maintain a safe distance from the vehicle ahead; First, obtain the module ID of the preceding vehicle, and obtain the position p of the preceding vehicle based on the module application layer. front and speed information v front , calculate the expected speed of the leading vehicle in the vehicle formation according to the following formula: In formula (4), dist(·) represents the distance between two points on the curve, v desire is the expected speed of the current vehicle, t adjust is the spacing adjustment time, s obj is the expected distance from the vehicle ahead; Since the time granularity of the adjustment interval is small, it is assumed that the vehicle ahead maintains a constant speed within the adjustment interval. The expected acceleration of the current vehicle in the platooning phase is: In formula (5), v0 is the current speed of the vehicle; At the same time, the vehicle must meet the maximum acceleration and maximum deceleration limits, so the expected acceleration of the vehicle in the formation phase needs to be corrected to: In formula (6), and They represent the maximum acceleration and maximum deceleration of vehicle braking respectively; the leading vehicle on the main road at time t adjust By adjusting its own acceleration, it can achieve the desired distance with the vehicle in front. Formulas (4)-(6) describe the control logic of the leading vehicle in the vehicle platooning stage. The driving state of the leading vehicle affects the following vehicles in the platoon and controls the driving state of the entire platoon. It controls the driving behaviors between vehicle platoons and between vehicle platoons and background traffic flows, and finally forms a vehicle platoon. ② Following vehicle in the vehicle formation: vehType is 2 or 3; the following behavior of the following vehicle is controlled by the IDM motion equation: In formulas (7)-(8), α is the sensitivity coefficient, v is the current speed of the vehicle, and v max is the maximum speed of the vehicle, s * (·) is the expected minimum vehicle distance, Δv is the speed difference between the vehicle and the front vehicle, Δx is the distance between the vehicle and the front vehicle, s0 is the minimum vehicle distance, T s is the safe headway, a m is the maximum acceleration, b n is the expected deceleration; S33, background traffic flow: vehType is 0; the background traffic flow is other vehicles on the main road except the vehicle formation. Their behavior is not actively changed during the simulation and is managed by the SUMO vehicle controller TraCI.

5. A highway vehicle formation control and merging simulation method according to claim 1, characterized in that: The specific steps of step S4 include: S41, control of the leading vehicle during the merging phase; After the leading vehicle in the main road vehicle formation receives the broadcast information from the roadside unit (RSU), it first determines whether the leading vehicle has reached the intersection merging point within 50m. If it has reached the range, it will slow down according to the merging principle. Main road vehicle merging principle: In order to avoid collision between main road vehicles and ramp vehicles, the main road vehicle formation should slow down appropriately and keep a certain safe distance from the ramp vehicles when approaching the intersection merging point to ensure the safety and stability of the merging; according to the position and speed of the ramp vehicle closest to the intersection merging point, as well as the position and speed of the current vehicle, the acceleration of the leading vehicle of the main road vehicle formation during the merging stage is determined as: Among them, v1 and s1 are the speed of the ramp vehicle closest to the intersection merging point and the distance from the intersection, v2 and s2 are the speed of the leading vehicle in the main road vehicle formation and the distance from the intersection merging point, and s0 is the safe distance between the leading vehicle in the main road vehicle formation and the ramp vehicle; S42, by using formula (9) to control the deceleration of the main road vehicle, the main road vehicle can make appropriate adjustments according to the driving conditions of the ramp vehicle when approaching the intersection area, thereby improving the smoothness and safety of road traffic; in this process, the main road vehicle can dynamically adjust its own speed and driving distance by receiving and analyzing the real-time information transmitted by the ramp vehicle.

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