Non-signalized intersection vehicle right-of-way decision and speed guidance method and system

Abstract

The invention discloses a non-signalized intersection vehicle right-of-way decision and speed guidance method. The method comprises the following steps: S1, collecting positions, speeds, accelerated speeds, vehicle types and intention information of all vehicles in a non-signalized intersection planning area; s2, determining a motorcade division scheme according to a formation rule combined with the vehicle intention; s3, establishing a road right optimization model of the non-signalized intersection, and determining the moment when each vehicle enters a confluence area of the non-signalized intersection and the allocated vehicle fleet occupation time of the non-signalized intersection; s4, constructing a speed suggestion algorithm, and inputting the moment when the vehicle enters the confluence area of the non-signalized intersection and vehicle state information; and S5, providing an on-line speed suggestion for the vehicle, and realizing conflict-free passing of the vehicle at the non-signalized intersection. The non-signalized intersection vehicle right-of-way decision and speed guidance method provided by the invention has stronger adaptability and can reduce the calculation complexity, and the vehicle passing efficiency and safety are improved.

Description

Technical Field

[0001] The present invention relates to the field of traffic engineering, and in particular to a method and system for vehicle right of way decision and speed guidance at an unsignalized intersection. Background Art

[0002] Intersections are often considered bottlenecks and accident-prone areas in traffic networks, where traffic from different directions converge and cause trajectory conflicts. Efficient traffic signal control strategies, such as adaptive signal control, have shown excellent performance in improving intersection throughput over traditional fully human-driven vehicle traffic. With the development of communication technology, connected vehicles can be guided to respond appropriately and improve traffic safety and efficiency without traffic signals, and vehicles in non-conflicting directions can occupy intersections at the same time.

[0003] Generally speaking, intersection management includes two main tasks: (1) right-of-way division; (2) speed guidance. There are two common methods for determining right-of-way to resolve conflicts: rule-based and optimization-based models. Many studies emphasize speed guidance methods, which use some simplified heuristic rules to determine the order of passing. Commonly used rules include first-come, first-served (FCFS), longest queue first (LQF), etc. Compared with rule-based methods, optimization-based methods have better performance in improving system efficiency and reducing individual travel costs. The commonly used method is the mixed integer linear programming model (MILP).

[0004] In recent years, the development of V2X technology has promoted real-time communication between vehicles and equipment, and between vehicles, which can achieve collaboration between vehicles and improve the efficiency of intersection traffic. Vehicle speed guidance can guide vehicles to pass at an appropriate speed without conflict based on the priority relationship between vehicles, while reducing delays, fuel consumption, the number of stops, and pollutant emissions. At present, the guidance of the speed of connected vehicles is mostly static and non-real-time, and human driving of vehicles is random, so real-time guidance is needed to reduce vehicle driving deviations. In addition, the existing speed guidance models are mostly determined based on the vehicle's own travel time, the vehicle's current position from the intersection, and the speed, without taking the status of conflicting vehicles into consideration. The safety of vehicle speed guidance and traffic efficiency need to be improved urgently. Summary of the invention

[0005] In order to solve the problem that the existing speed guidance method for unsignalized intersections does not take into account the randomness of human driving of vehicles, and the vehicle traffic efficiency and safety are low, the present invention proposes a vehicle right of way decision and speed guidance method and system for unsignalized intersections to solve the above problems.

[0006] The present application discloses a method for vehicle right of way decision and speed guidance at an unsignalized intersection, comprising the following steps:

[0007] S1. Divide the area within the communication range of the intersection into a planning area and a confluence area, wherein the confluence area is located inside the intersection, and collect the status information of all vehicles in the planning area, the vehicle status information includes the position, speed, acceleration and vehicle intention information;

[0008] S2. Determine the convoy division plan according to the convoy formation rules combined with the vehicle intentions;

[0009] S3. Establish a right-of-way optimization model for unsignalized intersections, and determine the optimal conflict-free passage sequence based on the conflict relationship between convoys, so as to determine the time when each vehicle enters the merging area of ​​the unsignalized intersection and the allocated convoy occupancy time of the unsignalized intersection;

[0010] S4, constructing a speed suggestion algorithm, inputting the time when the vehicle enters the merging area of ​​the unsignalized intersection and the vehicle status information into the vehicle speed suggestion algorithm;

[0011] S5. Based on the vehicle speed recommendation algorithm, provide online speed recommendations for the leading vehicle in the fleet to achieve conflict-free passage of vehicles at unsignalized intersections.

[0012] Preferably, the fleet division scheme in S2 is as follows:

[0013] S21. For vehicle c in lane i, if the vehicle intends to comply with the speed recommendation, execute S22; otherwise, execute S24;

[0014] S22, determining whether the headway between the vehicle and the preceding vehicle exceeds a threshold, if not, executing S23, otherwise, executing S25;

[0015] S23, determine whether the vehicle exceeds the maximum capacity, if not, execute S24, otherwise execute S25;

[0016] S24, assigning the vehicle to the previous fleet;

[0017] S25. Assign the vehicle to the next convoy and use it as the lead vehicle.

[0018] Preferably, the calculation formula of the time interval threshold in S22 is:

[0019] t d =2t s +H / v * ;

[0020] Among them, t s is the safe headway in seconds, H is the vehicle length in meters, v * is the desired speed of the vehicle.

[0021] Preferably, the objective function of the road right optimization model is:

[0022]

[0023] Among them, t a (i,j) represents the time when the jth vehicle on the i-th lane enters the planning area of ​​the unsignalized intersection, t e (i,j) represents the time when the jth vehicle on the i-th lane plans to enter the merging area of ​​the unsignalized intersection, n i is the number of vehicles on the i-th lane, and I is the total number of lanes.

[0024] Preferably, the constraints of the right-of-way optimization model include:

[0025] The basic constraints of vehicle kinematics, that is, the position, velocity, and acceleration of the vehicle satisfy the second-order dynamic constraints:

[0026]

[0027] Where p(t) is the position of the vehicle at time t, v(t) is the speed of the vehicle at time t, and u(t) is the acceleration of the vehicle at time t;

[0028] Earliest arrival time constraint: The time for any vehicle to enter an unsignalized intersection is limited by the vehicle's current state and cannot be earlier than the earliest arrival time, that is:

[0029]

[0030] Among them, t e represents the time when any vehicle is scheduled to enter the unsignalized intersection, c is any vehicle within the range of the unsignalized intersection, Ψ s The vehicle set optimized for the unsignalized intersection, with the earliest arrival time T m satisfy:

[0031]

[0032] Among them, v max is the maximum speed limit of the vehicle, u max is the maximum acceleration limit of the vehicle, d(t) is the remaining distance of the vehicle at the unsignalized intersection at time t;

[0033] Team occupancy time constraint: The time a team occupies the merging area of ​​an unsignalized intersection is related to the number of vehicles in the team. Taking into account the vehicle start-up reaction time, the maximum team occupancy time is calculated. The team occupancy time is calculated using the team maximum occupancy time, that is:

[0034] T o =T s +(n-1)T r ;

[0035] Among them, T o is the occupancy time of the convoy at the unsignalized intersection, n is the number of vehicles in the convoy, T r is the vehicle’s reaction time, T s T is the time it takes for the last vehicle in the convoy to enter the unsignalized intersection after stopping at the merging area of ​​the unsignalized intersection. s satisfy:

[0036]

[0037] Among them, l s The distance between the parking position of the last vehicle in the convoy and the unsignalized intersection;

[0038] l s =L+H+(n-1)(H+s0);

[0039] Where L is the trajectory length of the vehicle's lane in the unsignalized intersection, H is the vehicle length, and s0 is the minimum vehicle spacing;

[0040] Convoy non-conflict constraint: Considering the conflict relationship between different lane trajectories, non-conflict trajectories are arranged for the convoy. Compatible convoys can occupy the unsignalized intersection merging area at the same time. Therefore, the rule for convoy passage order decision is that each convoy enters the unsignalized intersection later than the convoy with higher priority and incompatible with it, that is:

[0041]

[0042] in, It represents the time when the leading vehicle in the convoy on the i-th lane plans to enter the merging area of ​​the unsignalized intersection. Represented as the i-th ′ The time when the leading vehicle in the convoy on the lane plans to enter the merging area of ​​the unsignalized intersection, Indicates the i ′ The time that the first vehicle in the convoy on the i lane occupies the intersection merging area; if ′ The convoy on the lane has priority, then the binary variable ω ii′ is 1, otherwise the binary variable ω ii′ is 0; binary variable λ ii′ It is used to identify whether two convoys are compatible, that is, whether the trajectories of the two convoys conflict in the intersection merging area. If the two convoys are compatible, then λ ii′ =0, otherwise λ ii′ =1.

[0043] Preferably, the speed suggestion algorithm is as follows:

[0044] S41, obtaining the current distance d(t) of the vehicle from the intersection merging area, the current speed v(t), and the remaining time t for entering the intersection merging area e -t;

[0045] S42, calculating the speed adjustment time, the calculation formula is:

[0046]

[0047] Where a is the recommended speed adjustment rate, a(+) is the maximum speed adjustment rate, a(-) is the minimum speed adjustment rate, and v * is the desired speed of the vehicle.

[0048] S43, if t e -t<Δt1, execute S44, otherwise, execute S48;

[0049] S44: If the collision risk intensity between the leading vehicle of the convoy and the trailing vehicle of the preceding convoy is greater than the threshold E k , execute S45, otherwise, execute S46;

[0050] S45, the recommended speed adjustment rate is the minimum speed adjustment rate, that is, a=a(-), and execute 4313;

[0051] S46, the recommended speed adjustment rate is 0, that is, a=0, and S413 is executed;

[0052] S47, calculating the remaining time after adjusting to the expected speed, the calculation formula is:

[0053] Δt2=(t e -t)-Δt1;

[0054] Calculate the distance that can be traveled at a constant speed after speed adjustment. The calculation formula is:

[0055]

[0056] S48, if Execute S49, otherwise, execute S410;

[0057] S49, the recommended speed adjustment rate is the minimum speed adjustment rate, that is, a=a(-), and S413 is executed;

[0058] S410, if Where n is the proposed threshold, execute S411, otherwise, execute S412;

[0059] S411, the recommended speed adjustment rate is 0, that is, a=0, and S413 is executed;

[0060] S412, the recommended speed adjustment rate is the maximum speed adjustment rate, that is, a=a(+), and S413 is executed;

[0061] S413: Output the recommended speed adjustment rate a.

[0062] Preferably, the collision risk intensity calculation formula in S44 is:

[0063]

[0064] Among them, M is the virtual mass, T is the influence coefficient of vehicle type on vehicle collision risk, and R is the influence coefficient of road conditions on vehicle collision risk. is the influence coefficient of vehicle acceleration on collision risk, K is the constant coefficient, u is the vehicle acceleration, G and δ are the control coefficients, θ is the angle between vehicle speed and pseudo distance, r ′ Pseudo-distance between vehicles;

[0065] The calculation formula of virtual mass is:

[0066] M=m(1.566×10 -14 v 6.687 +0.3354);

[0067] Where m is the actual mass of the vehicle and v is the speed of the vehicle.

[0068] Preferably, the pseudo distance is calculated as follows:

[0069] If the rear vehicle of the front convoy does not pass the conflict point, the pseudo distance is the distance from the vehicle to the conflict point minus the distance from the rear vehicle of the front convoy to the conflict point.

[0070] If the rear vehicle of the front convoy has passed the conflict point, the pseudo distance is the distance from the vehicle to the conflict point + the distance from the rear vehicle of the front convoy to the conflict point.

[0071] The present application also discloses a vehicle right-of-way decision and speed guidance system for an unsignalized intersection, including a roadside sensing device, a roadside computing unit and a vehicle-mounted unit;

[0072] Roadside sensing equipment: used to collect the position, speed, acceleration and vehicle intention information of all vehicles in the unsignalized intersection planning area, and transmit the collected information to the roadside computing unit;

[0073] Roadside computing unit: As the management center of the unsignalized intersection, it determines the fleet division plan based on the received vehicle information and the vehicle formation rules, and determines the conflict-free passage order based on the road right optimization model, so as to plan the time for each fleet to enter the unsignalized intersection merging area and the allocated occupancy time of the unsignalized intersection merging area, and transmits it to the vehicle-mounted unit;

[0074] On-board unit: Provides online speed recommendations for vehicles based on the time and vehicle speed recommendation algorithm planned by the roadside computing unit, enabling conflict-free passage of vehicles at unsignalized intersections.

[0075] Beneficial effects of the present invention:

[0076] (1) The present invention organizes vehicles in an unsignalized intersection to pass through in a convoy, and combines simple rules with an optimization model to propose a vehicle right-of-way decision and speed guidance method for an unsignalized intersection that has greater adaptability and can reduce computational complexity.

[0077] (2) The present invention takes into account the intention of the driver of the connected human-driven vehicle, provides online speed recommendations for the connected human-driven vehicle, and takes into account the risk of collision between the vehicle and the conflicting vehicle, while considering time and space, further improving the efficiency and safety of vehicle traffic. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 A flow chart of a vehicle right-of-way decision and speed guidance method at an unsignalized intersection according to an embodiment of the present invention;

[0079] Figure 2 A schematic diagram of an unsignalized intersection according to an embodiment of the present invention;

[0080] Figure 3 A schematic diagram of conflicts between lanes at an unsignalized intersection according to an embodiment of the present invention;

[0081] Figure 4 Schematic diagram of average vehicle delay under different strategies according to an embodiment of the present invention. DETAILED DESCRIPTION

[0082] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples.

[0083] The present application embodiment discloses a method for vehicle right of way decision and speed guidance at an unsignalized intersection, the process of which is as follows: Figure 1 As shown, considering the fully connected environment, all vehicles are connected human-driven vehicles, using vehicle-road cooperative technology to collect vehicle information within the intersection range, and considering the vehicle driving intention to determine the vehicle traffic order of each entrance lane of the unsignalized intersection, including the following steps:

[0084] S1. Divide the area within the communication range of the intersection into a planning area and a confluence area, where the confluence area is located inside the intersection. The roadside sensing device collects the status information of all vehicles in the planning area of ​​the unsignalized intersection. The vehicle status information includes the position, speed, acceleration, and vehicle intention (whether the speed recommendation is followed) and transmits it to the roadside computing unit through the roadside communication device;

[0085] S2. Determine the fleet division plan based on the formation rules combined with the vehicle intentions. The specific fleet division plan is as follows:

[0086] S21. For vehicle c in lane i, if the vehicle intends to comply with the speed recommendation, execute S22; otherwise, execute S24.

[0087] S22, determine whether the headway between the vehicle and the preceding vehicle exceeds a threshold value, if not, execute S23, otherwise, execute S25.

[0088] The calculation formula of the time interval threshold is:

[0089] t d =2t s +H / v * ;

[0090] Among them, t s is the safe headway in seconds, H is the vehicle length in meters, v * is the desired speed of the vehicle.

[0091] S23, determine whether the vehicle exceeds the maximum capacity, if not, execute S24, otherwise execute S25;

[0092] S24. Assign the vehicle to the previous fleet.

[0093] S25. Assign the vehicle to the next convoy and use it as the lead vehicle.

[0094] S3. Establish a right-of-way optimization model for unsignalized intersections, and determine the optimal conflict-free passage order based on the conflict relationship between convoys, so as to determine the time when each vehicle enters the merging area of ​​the unsignalized intersection and the allocated convoy occupancy time of the unsignalized intersection. If the leading vehicles in the convoy are all vehicles willing to comply with speed recommendations, the traffic efficiency can be optimized through the right-of-way optimization model; if the vehicles do not comply with speed recommendations, the convoy order is based on the first-come, first-served rule.

[0095] The objective function of the right-of-way optimization model is:

[0096]

[0097] Among them, t a (i,j) represents the time when the jth vehicle on the i-th lane enters the planning area of ​​the unsignalized intersection, t e (i,j) represents the time when the jth vehicle on the i-th lane plans to enter the merging area of ​​the unsignalized intersection, n i is the number of vehicles on the i-th lane, and i is the total number of lanes.

[0098] The constraints of the right-of-way optimization model include:

[0099] The basic constraints of vehicle kinematics, that is, the position, velocity, and acceleration of the vehicle satisfy the second-order dynamic constraints:

[0100]

[0101] Where p(t) is the position of the vehicle at time t, v(t) is the speed of the vehicle at time t, and u(t) is the acceleration of the vehicle at time t;

[0102] Earliest arrival time constraint: The time for any vehicle to enter an unsignalized intersection is limited by the vehicle's current state and cannot be earlier than the earliest arrival time, that is:

[0103]

[0104] Among them, t e represents the time when any vehicle is scheduled to enter the unsignalized intersection, c is any vehicle within the range of the unsignalized intersection, Ψ s The vehicle set optimized for the unsignalized intersection, with the earliest arrival time T m satisfy:

[0105]

[0106] Among them, v max is the maximum speed limit of the vehicle, u max is the maximum acceleration limit of the vehicle, d(t) is the remaining distance of the vehicle at the unsignalized intersection at time t;

[0107] Team occupancy time constraint: The time a team occupies the merging area of ​​an unsignalized intersection is related to the number of vehicles in the team. Taking into account the vehicle start-up reaction time, the maximum team occupancy time is calculated. The team occupancy time is calculated using the team maximum occupancy time, that is:

[0108] T o =T s +(n-1)T r ;

[0109] Among them, T o is the occupancy time of the convoy at the unsignalized intersection, n is the number of vehicles in the convoy, T r is the vehicle’s reaction time, T s T is the time it takes for the last vehicle in the convoy to enter the unsignalized intersection after stopping at the merging area of ​​the unsignalized intersection. s satisfy:

[0110]

[0111] Among them, l s The distance between the parking position of the last vehicle in the convoy and the unsignalized intersection;

[0112] l s =L+H+(n-1)(H+s0);

[0113] Where L is the trajectory length of the vehicle's lane in the unsignalized intersection, H is the vehicle length, and s0 is the minimum vehicle spacing;

[0114] Convoy non-conflict constraint: Considering the conflict relationship between different lane trajectories, non-conflict trajectories are arranged for the convoy. Compatible convoys can occupy the unsignalized intersection merging area at the same time. Therefore, the rule for convoy passage order decision is that each convoy enters the unsignalized intersection later than the convoy with higher priority and incompatible with it, that is:

[0115]

[0116] in, It represents the time when the leading vehicle in the convoy on the i-th lane plans to enter the merging area of ​​the unsignalized intersection. Represented as the i-th ′ The time when the leading vehicle in the convoy on the lane plans to enter the merging area of ​​the unsignalized intersection, Indicates the i ′ The time that the first vehicle in the convoy on the i lane occupies the intersection merging area; if ′ The convoy on the lane has priority, then the binary variable ω ii′ is 1, otherwise the binary variable ω ii′ is 0; binary variable λ ii′ It is used to identify whether two convoys are compatible, that is, whether the trajectories of the two convoys conflict in the intersection merging area. If the two convoys are compatible, then λ ii′ =0, otherwise λ ii′ =1.

[0117] S4. Construct a speed suggestion algorithm, and input the time when the vehicle enters the merging area of ​​the unsignalized intersection and the vehicle status information into the vehicle speed suggestion algorithm.

[0118] Considering the randomness of vehicle driving, real-time speed recommendations are provided to the leading vehicle in the fleet. The vehicle speed recommendation algorithm is as follows:

[0119] S41, obtaining the current distance d(t) of the vehicle from the intersection merging area, the current speed v(t), and the remaining time t for entering the intersection merging area e -t.

[0120] S42, calculating the speed adjustment time, the calculation formula is:

[0121]

[0122] Where a is the recommended speed adjustment rate, a(+) is the maximum speed adjustment rate, a(-) is the minimum speed adjustment rate, and v * is the desired speed of the vehicle.

[0123] S43, if t e -t<Δt1, execute S44; otherwise, execute S48.

[0124] S44: To avoid a collision between two convoys, if the collision risk intensity between the leading vehicle of the convoy and the trailing vehicle of the preceding convoy is greater than the threshold E k , execute S45, otherwise, execute S46, in this implementation, the threshold E k Set to 300.

[0125] The calculation formula for collision risk intensity is:

[0126]

[0127] Among them, M is the virtual mass, T is the influence coefficient of vehicle type on vehicle collision risk, and R is the influence coefficient of road conditions on vehicle collision risk. is the influence coefficient of vehicle acceleration on collision risk, K is the constant coefficient, u is the vehicle acceleration, G and δ are the control coefficients, θ is the angle between vehicle speed and pseudo distance, r ′ Pseudo-distance between vehicles.

[0128] The calculation formula of virtual mass is:

[0129] M=m(1.566×10 -14 v 6.687 +0.3354);

[0130] Where m is the actual mass of the vehicle and v is the speed of the vehicle.

[0131] The calculation method of pseudo distance is:

[0132] If the rear vehicle of the front convoy does not pass the conflict point, the pseudo distance is the distance from the vehicle to the conflict point minus the distance from the rear vehicle of the front convoy to the conflict point.

[0133] If the rear vehicle of the front convoy has passed the conflict point, the pseudo distance is the distance from the vehicle to the conflict point + the distance from the rear vehicle of the front convoy to the conflict point.

[0134] S45. The recommended speed adjustment rate is the minimum speed adjustment rate, that is, a=a(-), and execute 4313.

[0135] S46. The recommended speed adjustment rate is 0, that is, a=0, and S413 is executed.

[0136] S47, calculating the remaining time after adjusting to the expected speed, the calculation formula is:

[0137] Δt2=(t e -t)-Δt1;

[0138] Calculate the distance that can be traveled at a constant speed after speed adjustment. The calculation formula is:

[0139]

[0140] S48, if Execute S49; otherwise, execute S410.

[0141] S49. The recommended speed adjustment rate is the minimum speed adjustment rate, that is, a=a(-), and S413 is executed.

[0142] S410, if Wherein η is a proposed threshold value, and in this implementation, η is set to 30, and S411 is executed; otherwise, S412 is executed.

[0143] S411. The recommended speed adjustment rate is 0, that is, a=0, and S413 is executed.

[0144] S412: The recommended speed adjustment rate is the maximum speed adjustment rate, that is, a=a(+), and then S413 is executed.

[0145] S413: Output the recommended speed adjustment rate a.

[0146] S5. Based on the vehicle speed recommendation algorithm, an online speed recommendation is provided to the leading vehicle of the convoy to achieve conflict-free passage of vehicles at unsignalized intersections. After the tail vehicle of the convoy passes through the merging area, the convoy is disbanded.

[0147] The embodiment of the present application also discloses a vehicle right-of-way decision and speed guidance system at an unsignalized intersection, including a roadside sensing device, a roadside computing unit and a vehicle-mounted unit;

[0148] Roadside sensing equipment: used to collect the position, speed, acceleration and vehicle intention information of all vehicles in the unsignalized intersection planning area, and transmit the collected information to the roadside computing unit;

[0149] Roadside computing unit: As the management center of the unsignalized intersection, it determines the fleet division plan based on the received vehicle information and the vehicle formation rules, and determines the conflict-free passage order based on the road right optimization model, so as to plan the time for each fleet to enter the unsignalized intersection merging area and the allocated occupancy time of the unsignalized intersection merging area, and transmits it to the vehicle-mounted unit;

[0150] On-board unit: Provides online speed recommendations for vehicles based on the time and vehicle speed recommendation algorithm planned by the roadside computing unit, enabling conflict-free passage of vehicles at unsignalized intersections.

[0151] In a specific embodiment, the schematic diagram of the unsignalized intersection is as follows: Figure 2 As shown in Figure 1, there are 8 lanes in total. The length of the vehicle trajectory in each lane is fixed. Lanes 1, 3, 5, and 7 are left-turn lanes, and lanes 2, 4, 6, and 8 are through lanes. The length of the planned area for the unsignalized intersection is 300 meters, and the length of the confluence area is 50 meters. The conflict relationship between the lanes is as follows: Figure 3 shown.

[0152] The platooning rules considering vehicle intentions determine the platoon division. In this embodiment, the safe headway t s = 2s, vehicle length L = 5m, vehicle expected speed v * =5m / s, the maximum capacity of the fleet is m=6.

[0153] In the unsignalized intersection vehicle right-of-way optimization model, the goal is to minimize the vehicle delay in the unsignalized intersection planning area, where the maximum vehicle speed v max =20m / s, maximum acceleration u max =3m / s 2 Through the right-of-way optimization model, the conflict-free passage of the convoy in the merging area of ​​the unsignalized intersection can be achieved, and the time for the head vehicle of each convoy to enter the merging area of ​​the intersection can be obtained. The optimization model can be solved using Gurobi software.

[0154] Based on the time of entering the intersection merging area, provide real-time speed suggestions for the leading vehicle of the convoy and give speed suggestions for the next period. In the speed guidance model of the leading vehicle of the convoy, the maximum speed adjustment rate a(+)=2m / s 2 , minimum speed adjustment rate a(-)=-3m / s 2 In the calculation of collision risk intensity, the control coefficient G=0.5, δ=1.2, the influence coefficient of vehicle type on vehicle collision risk T=1, the influence coefficient of road conditions on vehicle collision risk R=1, and the constant coefficient K=5.

[0155] For connected human-driven vehicles that are not the lead vehicle in the convoy and the lead vehicle that provides speed recommendations, the vehicle behavior adopts the Gipps following model that takes into account randomness, and its randomness is expressed as:

[0156] u(t)=a(t)+bq(t)r(t)

[0157] Where a(t) represents the acceleration generated by the model at time t, b represents the standard deviation under different accelerations, q(t) is a uniformly distributed random number between 0 and 1, r(t) is 1 or -1 with a probability of 50%, and u(t) is the actual acceleration.

[0158] Matlab software is used for simulation to obtain evaluation indicators of vehicle right-of-way decision-making and vehicle speed guidance methods, including traffic efficiency indicators: vehicle evaluation delay, and safety indicators: vehicle collision time (TTC). Figure 4 The average vehicle delay under different strategies is shown, where AIMH_O represents the method proposed in this application, AIMH_I represents the strategy that does not adopt the speed guidance method based on collision, FCFS_O represents the strategy that adopts the speed guidance method based on collision based on the first-come-first-served rule, and FCFS_I represents the strategy that does not adopt the speed guidance method based on collision based on the first-come-first-served rule. Figure 4 It can be seen that when the traffic flow is small, the average delay under each strategy is not much different. As the traffic flow increases, the method proposed in this application can effectively reduce the average vehicle delay.

[0159] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A vehicle right-of-way decision and speed guidance method at an unsignalized intersection, characterized in that: The following steps are involved: S1. Divide the area within the intersection communication range into a planning area and a confluence area, and collect the status information of all vehicles in the planning area. The vehicle status information includes the position, speed, acceleration, and vehicle intention information; S2. Determine the convoy division plan according to the convoy formation rules combined with the vehicle intentions; S3. Establish a right-of-way optimization model for unsignalized intersections, and determine the optimal conflict-free passage sequence based on the conflict relationship between convoys, so as to determine the time when each vehicle enters the merging area of ​​the unsignalized intersection and the allocated convoy occupancy time of the unsignalized intersection; S4, constructing a speed suggestion algorithm, inputting the time when the vehicle enters the merging area of ​​the unsignalized intersection and the vehicle status information into the vehicle speed suggestion algorithm; S5. Based on the vehicle speed recommendation algorithm, provide online speed recommendations for the leading vehicle in the fleet to achieve conflict-free passage of vehicles at unsignalized intersections.

2. The vehicle right-of-way decision and speed guidance method at an unsignalized intersection according to claim 1, characterized in that: The fleet division scheme in S2 is as follows: S21. For vehicle c in lane i, if the vehicle intends to comply with the speed recommendation, execute S22; otherwise, execute S24; S22, determining whether the headway between the vehicle and the preceding vehicle exceeds a threshold, if not, executing S23, otherwise, executing S25; S23, determine whether the vehicle exceeds the maximum capacity, if not, execute S24, otherwise execute S25; S24, assigning the vehicle to the previous fleet; S25. Assign the vehicle to the next convoy and use it as the lead vehicle.

3. The vehicle right-of-way decision and speed guidance method at an unsignalized intersection according to claim 2, characterized in that: The calculation formula of the time interval threshold in S22 is: t d =2t s +H / v * ; Among them, t s is the safe headway in seconds, H is the vehicle length in meters, v * is the desired speed of the vehicle.

4. The vehicle right-of-way decision and speed guidance method at an unsignalized intersection according to claim 3, characterized in that: The objective function of the right-of-way optimization model is: Among them, t a (i,j) represents the time when the jth vehicle on the i-th lane enters the planning area of ​​the unsignalized intersection, t e (i,j) represents the time when the jth vehicle on the i-th lane plans to enter the merging area of ​​the unsignalized intersection, n i is the number of vehicles on the i-th lane, and i is the total number of lanes.

5. The vehicle right-of-way decision and speed guidance method at an unsignalized intersection according to claim 4, characterized in that: The constraints of the right-of-way optimization model include: Basic constraints of vehicle kinematics: Where p(t) is the position of the vehicle at time t, v(t) is the speed of the vehicle at time t, and u(t) is the acceleration of the vehicle at time t; Earliest arrival time constraint: Among them, t e represents the time when any vehicle is scheduled to enter the unsignalized intersection, c is any vehicle within the range of the unsignalized intersection, Ψ s The vehicle set optimized for the unsignalized intersection, with the earliest arrival time T m satisfy: Among them, v max is the maximum speed limit of the vehicle, u max is the maximum acceleration limit of the vehicle, d(t) is the remaining distance of the vehicle at the unsignalized intersection at time t; Fleet occupancy time constraints: T o =T s +(n-1)T r ; Among them, T o is the occupancy time of the convoy at the unsignalized intersection, n is the number of vehicles in the convoy, T r is the vehicle’s reaction time, T s T is the time it takes for the last vehicle in the convoy to enter the unsignalized intersection after stopping at the merging area of ​​the unsignalized intersection. s satisfy: Among them, l s The distance between the parking position of the last vehicle in the convoy and the unsignalized intersection; l s =L+H+(n-1)(H+s0); Where L is the trajectory length of the vehicle's lane in the unsignalized intersection, H is the vehicle length, and s0 is the minimum vehicle spacing; Convoy non-conflicting constraints: in, It represents the time when the leading vehicle in the convoy on the i-th lane plans to enter the merging area of ​​the unsignalized intersection. It is the time when the leading vehicle in the convoy on the i′th lane plans to enter the merging area of ​​the unsignalized intersection. represents the time that the leading vehicle in the convoy on the i′th lane occupies the intersection merging area; if the convoy on the i′th lane has priority, the binary variable ω ii′ is 1, otherwise the binary variable ω ii′ is 0; binary variable λ ii′ It is used to identify whether two convoys are compatible, that is, whether the trajectories of the two convoys conflict in the intersection merging area. If the two convoys are compatible, then λ ii′ =0, otherwise λ ii′ =1.

6. The vehicle right-of-way decision and speed guidance method at an unsignalized intersection according to claim 5, characterized in that: The speed suggestion algorithm is as follows: S41, obtaining the current distance d(t) of the vehicle from the intersection merging area, the current speed v(t), and the remaining time t for entering the intersection merging area e -t; S42, calculating the speed adjustment time, the calculation formula is: Where a is the recommended speed adjustment rate, a(+) is the maximum speed adjustment rate, a(-) is the minimum speed adjustment rate, and v * is the desired speed of the vehicle. S43, if t e -t<Δt1, execute S44, otherwise, execute S48; S44: If the collision risk intensity between the leading vehicle of the convoy and the trailing vehicle of the preceding convoy is greater than the threshold E k , execute S45, otherwise, execute S46; S45, the recommended speed adjustment rate is the minimum speed adjustment rate, that is, a=a(-), and execute 4313; S46, the recommended speed adjustment rate is 0, that is, a=0, and S413 is executed; S47, calculating the remaining time after adjusting to the expected speed, the calculation formula is: Δt2=(t e -t)-Δt1; Calculate the distance that can be traveled at a constant speed after speed adjustment. The calculation formula is: S48, if Execute S49, otherwise, execute S410; S49, the recommended speed adjustment rate is the minimum speed adjustment rate, that is, a=a(-), and S413 is executed; S410, if Where n is the proposed threshold, execute S411, otherwise, execute S412; S411, the recommended speed adjustment rate is 0, that is, a=0, and S413 is executed; S412, the recommended speed adjustment rate is the maximum speed adjustment rate, that is, a=a(+), and S413 is executed; S413: Output the recommended speed adjustment rate a.

7. The vehicle right-of-way decision and speed guidance method at an unsignalized intersection according to claim 6, characterized in that: The collision risk intensity calculation formula in S44 is: Among them, M is the virtual mass, T is the influence coefficient of vehicle type on vehicle collision risk, and R is the influence coefficient of road conditions on vehicle collision risk. is the influence coefficient of vehicle acceleration on collision risk, K is the constant coefficient, u is the vehicle acceleration, G and δ are the control coefficients, θ is the angle between vehicle speed and pseudo distance, and r′ is the pseudo distance between vehicles; The calculation formula of virtual mass is: M=m(1.566×10 -14 in 6.687 +0.3354); Among them, m is the actual mass of the vehicle and v is the speed of the vehicle.

8. The vehicle right-of-way decision and speed guidance method at an unsignalized intersection according to claim 7, characterized in that: The pseudo-range is calculated as follows: If the rear vehicle of the front convoy does not pass the conflict point, the pseudo distance is the distance from the vehicle to the conflict point minus the distance from the rear vehicle of the front convoy to the conflict point. If the rear vehicle of the front convoy has passed the conflict point, the pseudo distance is the distance from the vehicle to the conflict point + the distance from the rear vehicle of the front convoy to the conflict point.

9. A vehicle right-of-way decision and speed guidance system for an unsignalized intersection, used to implement the method described in any one of claims 1 to 8, characterized in that: Includes roadside sensing equipment, roadside computing unit and vehicle-mounted unit; Roadside sensing equipment: used to collect the position, speed, acceleration and vehicle intention information of all vehicles in the unsignalized intersection planning area, and transmit the collected information to the roadside computing unit; Roadside computing unit: As the management center of the unsignalized intersection, it determines the fleet division plan based on the received vehicle information and the vehicle formation rules, and determines the conflict-free passage order based on the road right optimization model, so as to plan the time for each fleet to enter the unsignalized intersection merging area and the allocated occupancy time of the unsignalized intersection merging area, and transmits it to the vehicle-mounted unit; On-board unit: Provides online speed recommendations for vehicles based on the time and vehicle speed recommendation algorithm planned by the roadside computing unit, enabling conflict-free passage of vehicles at unsignalized intersections.

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