Cooperative passing method and system for automatic driving motorcade at non-signalized intersection

Abstract

The invention relates to the technical field of intelligent traffic, and discloses a non-signalized intersection fleet cooperative passing method and system, and the method and system comprise the following steps: firstly constructing an intersection scene; information of all motorcades in the intersection area is obtained through the central controller; then establishing a vehicle passing and variable speed limit strategy process; calculating the optimal passing sequence of the motorcade in the control area by using the information according to a rolling time domain algorithm; meanwhile, the motorcade in the variable speed limit area receives a controller instruction to adjust the motorcade and the speed according to the passing time of the front motorcade and the reserved gap, and after entering the control area, the motorcade calculates the passing sequence according to a rolling time domain algorithm to sequentially pass through; compared with the prior art, the method solves the problem of conflict when vehicles at the entrance lanes of the non-signalized intersection enter the intersection at the same time, guarantees the integrity of the vehicle fleet, improves the capacity, passing efficiency and safety of the intersection, reduces the waiting and stagnation of the vehicles, and provides a high-efficiency system architecture for the cooperative passing of the vehicle fleet at the non-signalized intersection.

Description

Technical Field

[0001] The invention relates to the field of intelligent transportation technology, and mainly discloses a method and system for coordinated traffic of fleets at an unsignalized intersection. Background Art

[0002] As people's living standards improve, higher traffic demands have brought huge challenges to urban transportation systems. The increasing number of traditional human-driven vehicles (HVs) will further escalate serious traffic problems such as collision risks, traffic delays, and energy consumption. The impact of these problems is amplified as the traffic conditions at intersections become more complex. Therefore, in order to improve the safety and operation efficiency of intersections, intersection management has attracted widespread attention from academia and industry. In recent years, the emergence of connected autonomous vehicles (CAVs) has provided an opportunity to solve the above traffic problems. How to better integrate CAVs into intersections is a major research point. At the same time, compared with signalized intersections, signalless control is superior to traditional signal control. While ensuring safety, it allows vehicles to pass through the gaps between conflicting flows, passing through the intersection without collision or conflict, thereby reducing waiting in front of the stop line. Compared with controlling the passage order of individual CAVs, controlling CAV queues at signalless intersections is more complicated, and both centralized control and decentralized control must be considered. It can provide more benefits to the central controller because it has the following characteristics: (1) Reduced communication burden: The intersection management controller only communicates with the queue leader, not all individual CAVs; (2) Higher operating efficiency: Each CAV is required to have closed and inserted prohibited vehicle following behaviors.

[0003] Moreover, incorporating platooning and coordination into a central management controller is challenging but worthy of detailed investigation. Although many efforts have been made in previous studies to verify the reliability and effectiveness of platooning and coordination, these studies still have some limitations: (1) Few studies have attempted to incorporate coordination measures into CAV platoon control; (2) Most existing CAV platoon control models adopt inefficient platoon release rules; (3) The coordination models proposed in most previous studies lack rigor and are only applicable to limited traffic conditions. Based on the above limitations, they cannot achieve efficient coordination and reduce conflicts and collisions at intersections.

[0004] Therefore, the method and system for coordinated traffic of a fleet at an unsignalized intersection proposed in the present invention is very necessary, which can solve the problem of offsetting potential conflict points at the above-mentioned unsignalized intersection and the problem of continuous traffic of vehicles without stopping, which can not only improve the traffic efficiency of the intersection but also reduce the occurrence of accidents and enhance the driving safety of vehicles or fleets. Summary of the invention

[0005] The present invention relates to the field of intelligent transportation and automatic driving control, and in particular to a method and system for cooperative passage of an automatic driving fleet at an unsignalized intersection, which is dedicated to solving the above-mentioned limitations, facilitating the CAV queue to quickly pass through the intersection under the coordination of a central controller, reducing the occurrence of intersection conflict accidents, and realizing continuous non-stop passage of the fleet.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method and system for cooperative passage of an autonomous driving fleet at an unsignalized intersection, comprising the following steps:

[0008] Step S1, first construct an intersection scene model and classify the entire intersection area into functional areas;

[0009] The intersection scene constructed in step S1 is as follows: the intersection is symmetrical, and each entrance road is denoted as N, S, W, and E, and has three lanes respectively, denoted as left turn, straight, and right turn; the intersection is divided into a free driving zone denoted as FZ, a variable speed limit zone denoted as VLZ, a central control zone denoted as CZ, and a coordination zone denoted as COZ. The central control zone ranges from each entrance road segment to the intersection center within a radius of L. The area enclosed by the stop lines of each entrance road is called the coordination zone, which is square and has a width of W. The variable speed limit zone ranges from the intersection section within a radius of Lv from the central control zone, and the area outside the variable speed limit zone is the free driving zone; an intersection management controller is set at the intersection center of the central control zone, denoted as the central controller. The controller is a system that optimizes intersection traffic flow through automation and intelligent technology, and aims to improve the urban traffic environment by reducing traffic congestion and improving traffic safety and efficiency.

[0010] Furthermore, in the method and system for cooperative passage of an autonomous driving fleet at a signal-free intersection, the fleet can change lanes under safe conditions when it is in a free driving area, and when it is in a variable speed limit area, not only the speed but also the size of the fleet can be changed. However, individual vehicles cannot change lanes at will in this area and can only move longitudinally. At the same time, the fleet enters the central control area at a constant speed to avoid conflict points and pass through the intersection.

[0011] Step S2: Obtain all fleet information in the intersection area through the central controller:

[0012] All autonomous vehicles entering the intersection are equipped with wireless communicators, dedicated short-range communication autonomous vehicles and cellular devices to support vehicle communication. In the present invention, the headway, headway distance, speed and other status information between vehicles in the convoy are always consistent and the status information is changed synchronously. Therefore, the convoy is regarded as a rectangular block, denoted as Compared with ordinary vehicles that only change in length, the leader of the fleet will use the fleet size, such as the number of vehicles or vehicle length, fleet speed, acceleration, and position - using the position of the lead vehicle to represent the position of the entire fleet, and then broadcast it to the central controller through the communication system to store and classify all available information.

[0013] Step S3: Establishing fleet traffic and variable speed limit strategy process:

[0014] The basic parameters for the optimal traffic order calculation and variable speed limit control of the fleet are as follows:

[0015] 1) The length and width of each vehicle in the convoy are denoted as ι and w, and each vehicle or convoy satisfies the following second-order dynamics:

[0016]

[0017] In the formula represents the displacement of the vehicle's front bumper between the entrance to the control area and the current position, where d represents the four entrance lanes d = {N, S, W, E}, and the lane indexes of the entrance lanes are recorded from right to left as: r∈R = {0, 1, 2}, i∈I = {0, 1, 2, ···, p r} represents the i-th team or vehicle, represents the convoy speed, represents the convoy acceleration;

[0018] 2) There are three special moments when each formation enters the coordination zone from the central control zone. It is the moment when the front bumper of the leading vehicle enters the central control area. The moment when the front bumper enters the coordination zone, that is, the moment when the leading vehicle crosses the stop line. is the moment when the rear bumper of the last vehicle in the convoy leaves the coordination area, The interval between the three moments is described as: waiting time: Collaboration time: Driving time:

[0019] 3) Within the specified coordination time interval t∈[T, T+Δt], the number of convoys p on each entrance lane r∈R={0,1,2} d,r , use p d,r,i Indicates that according to the arrival sequence i∈I={0,1,2,···,p r}, each import channel d = {N, S, W, E} is polled.

[0020] And the coordination process to ensure the safety and efficiency of the fleet is described as:

[0021] 1) First of all, we must ensure that there is no preemption between convoys on the same entrance road section: convoys in the same lane cannot enter the control area at the same time. And convoys at different entrances entering the control area need to pay attention to conflicts, so there are Note that the right-turning convoys on the entrance lanes are not considered at this time, and will not affect other convoys. Also, d, d′, d″, d″′={N, S, W, E}, u, i′, `i, i″, i″ respectively correspond to different convoys on the corresponding entrance lanes, where i′, `i represent convoys on different lanes of the same entrance lane.

[0022] 2) There is a time gap between the front and rear convoys in the same lane, which is calculated by the central controller after the previous convoy passes the intersection and is recorded as And the gap between convoys from different directions is recorded as:

[0023] 3) The recommended speed for the fleet in the variable speed limit zone is Then the delay time of the convoy is described as the difference between the actual time when the convoy arrives at the central control area and the theoretical arrival time, which is calculated as follows:

[0024]

[0025] 4) The maximum time required to coordinate all vehicles at an intersection is defined as:

[0026]

[0027] 5) The maximum time required for coordination must meet the following requirements:

[0028] C max ≤ΔT+T min ,

[0029] In the coordination time interval t∈[T,T+Δt], T min is the minimum time interval between the arrival and start of each convoy.

[0030] The process and specific steps for establishing the fleet traffic strategy and variable speed limit strategy described in step S3 are as follows:

[0031] Step S301: The fleet traffic strategy calculates the traffic order of each entrance road in the central control area according to the proposed rolling time domain algorithm:

[0032] The central controller calculates the optimal passage order of the fleet in the control area based on the rolling time domain algorithm. This part aims to minimize the maximum coordination time and maximum delay, obtain the time when the fleet enters the coordination area, and optimize the subsequent fleet speed recommendations and fleet size calculation plan;

[0033] Step a: Define the decision variable as the moment when the fleet enters the coordination zone: Lane number index r∈R={0,1,2}, lane fleet index i∈I={0,1,2,···,p r}; In addition, define the pass order as an intermediate variable:

[0034]

[0035] Step b: Define constraints:

[0036] 1) Different convoys on the same entrance and lane cannot enter the central control area at the same time, and the following conditions must be met:

[0037]

[0038] 2) To avoid lateral collisions, the following constraints must be met:

[0039] Letz=Z i,i′,`i,i″,i″′ ,

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046] In the formula Indicates the current moment of the fleet that first enters the coordination area in the next time domain;

[0047] 3) The intermediate variables satisfy the following constraints:

[0048]

[0049]

[0050] Where T inn and T iax Arrival time and start time Minimum and maximum time interval between: M max represents the maximum number of vehicles in a convoy. Note that T iax Used to prevent the vehicle from stopping, that is, to avoid the undesirable phenomenon of stop-and-go;

[0051] Step c: Setting the objective function. When considering the dual-criteria optimization problem of the maximum completion time of the intersection coordination solution and the maximum delay of all fleets, the following function expression is established:

[0052]

[0053] Step d: Use an exact algorithm to solve the combinatorial optimization problem and calculate That is, the moment when the convoy enters the coordination zone, and the convoy enters the center of the intersection and passes through it according to the sequence at that moment;

[0054] Step S302: After the convoy closest to the stop line of the intersection passes through the intersection according to the traffic order calculated in step S301, the central controller will obtain the available time slot and the corresponding status information of the next convoy on other entrance roads. The central controller integrates this information to obtain the recommended size and speed of the next convoy; the leader of the next convoy in the variable speed limit area synchronizes the adjustment command to the following vehicles through the roadside unit communication according to the adjustment status command broadcast by the central controller:

[0055] Step a: Determine the fleet size in the variable speed limit zone:

[0056] 1) When the minimum headway between vehicles in a convoy is set to h d , vehicle length ι, then each team p r,i The number of vehicles is:

[0057]

[0058] in It's the team p r,i The length of the lane number index r∈R={0,1,2}, the lane fleet index i∈I={1,2,···,p r}, so for all vehicles in the intersection area As a single individual, it can be recorded as V r,n ,

[0059] 2) The central controller transmits the recommended convoy size information to each leading vehicle and broadcasts it to the trailing vehicle. The trailing vehicles decelerate and disintegrate according to the information. The following formula can be used to represent the number of vehicles in the convoy:

[0060]

[0061]

[0062] Step b: Adjust the speed of the new fleet in the variable speed limit zone:

[0063] After receiving the speed suggestion, the leading vehicle will accelerate or decelerate to the target speed according to the situation of the team / vehicle in front, which is mainly divided into the following situations:

[0064] 1) Situation 1: When there are other convoys in the variable speed limit zone, the new convoy slows down to avoid collision. After the convoy ahead of it exits the variable speed limit zone, it accelerates to the recommended speed at maximum acceleration and then drives at a constant speed into the central control zone and passes through the intersection according to the calculated traffic order.

[0065]

[0066] Where v d,r,i-1 represents the original speed of the fleet in the variable speed limit area, a represents the original acceleration of the current fleet, Indicates the distance between the current convoy and the center of the intersection;

[0067] 2) Situation 2: When there are no other convoys in the variable speed limit zone, the new convoy only needs to adjust its speed and pass through at a constant speed;

[0068]

[0069] 3) Situation 3: There is no convoy blocking the variable speed limit area, but the convoy has already driven to the central control area, so it needs to slow down to pass;

[0070]

[0071] Step S303, the two steps mentioned above can be executed simultaneously and the subsequent convoy can be executed cyclically to obtain the optimal traffic order and the optimal convoy size and speed, ensuring that the convoy passes through the intersection safely and efficiently.

[0072] Compared with the existing intersection autonomous driving vehicle coordinated traffic control technology, the present invention has the following outstanding features:

[0073] 1. The present invention considers that vehicles pass through an unsignalized intersection in the form of a convoy, uses a polling algorithm, and calculates the convoy's passage order based on the evaluation indicators of convoy safety, efficiency, and low latency, which has practical application value.

[0074] Second, the present invention considers pure CAV formation, which is simple to control. It only needs to transmit and broadcast the control command to the leader of the fleet to achieve the state control of the entire fleet. In addition, it is very likely that autonomous driving vehicles with 100% penetration rate will appear on the road in the near future, so the present invention has future practical significance. The invention considers that the available gap calculated by the polling algorithm can adjust the subsequent fleet size change and vehicle speed, so as to control or guide the vehicle to pass through the unsignaled intersection with higher efficiency, control the minimization of the maximum delay and the maximum coordination time, and resolve the conflict points and reduce the collision between fleets inside the intersection.

[0075] The collaborative traffic method designed in the present invention can effectively plan the traffic efficiency and traffic safety of the fleets on each entrance road, and can minimize the delay or even stagnation caused by other fleets when the fleet is on the way and entering the center area of ​​the intersection. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 The present invention is a flowchart of a method and system for cooperative traffic of fleets at an unsignalized intersection in the implementation of the present invention.

[0077] Figure 2 The length and name of each partition of the unsignalized intersection in the embodiment of the present invention.

[0078] Figure 3 Schematic diagram of important time nodes in an embodiment of the present invention.

[0079] Figure 4 Schematic diagram of each entrance lane and conflict point in an embodiment of the present invention. DETAILED DESCRIPTION

[0080] Next, the embodiments of the present invention are explained and described in detail in conjunction with the accompanying drawings of the present invention.

[0081] The present invention relates to the field of intelligent transportation and automatic driving control, and in particular to a method and system for cooperative passage of an automatic driving fleet at an unsignalized intersection, which is dedicated to solving the above-mentioned limitations, facilitating the CAV queue to quickly pass through the intersection under the coordination of a central controller, reducing the occurrence of intersection conflict accidents, and realizing continuous non-stop passage of the fleet.

[0082] To achieve the above object, the present invention adopts the following technical solutions:

[0083] A method and system for cooperative passage of an autonomous driving fleet at an unsignalized intersection, such as Figure 1 As shown, the following steps are included:

[0084] Step S1 is to first construct an intersection scene model and classify the entire intersection area into functional areas;

[0085] Step S2 is to obtain all fleet information in the intersection area through the central controller;

[0086] Step S3 is to establish the fleet passage and variable speed limit strategy process. The central controller calculates the optimal passage order of the fleet in the control area based on the rolling time domain algorithm. Then the fleet in the variable speed limit area receives the control command of the central controller to adjust the fleet and vehicle speed according to the passage time of the front fleet and the gap left.

[0087] Step S4 is to enter the control area and pass through the control area in sequence according to the rolling time domain algorithm.

[0088] In the embodiment of the present invention, step S1 first constructs an intersection scene model, and classifies the entire intersection area into functional areas, such as Figure 2 As shown, it specifically includes the following contents:

[0089] The constructed intersection scenario is as follows: the intersection is symmetrical, and each entrance road is denoted by N, S, W, and E, with three lanes respectively, denoted by left turn, straight go, and right turn; the intersection is divided into a free driving zone denoted by FZ, a variable speed limit zone denoted by VLZ, a central control zone denoted by CZ, and a coordination zone denoted by COZ. The central control zone ranges from each entrance road segment to the intersection center within a radius of L. The area enclosed by the stop lines of each entrance road is called the coordination zone, which is square and has a width of W. The variable speed limit zone ranges from the intersection section within a radius of Lv from the central control zone, and the area outside the variable speed limit zone is the free driving zone; an intersection management controller is set at the intersection center of the central control zone, denoted by the central controller. Intersection management control is a system that optimizes intersection traffic flow through automation and intelligent technology, and aims to improve the urban traffic environment by reducing traffic congestion, improving traffic safety and efficiency.

[0090] Furthermore, in the method and system for cooperative passage of an autonomous driving fleet at a signal-free intersection, when the fleet is in a variable speed limit zone, not only the speed but also the size of the fleet can be changed, but individual vehicles cannot change lanes at will in this area and can only move longitudinally. At the same time, the fleet enters the central control area at a constant speed to avoid conflict points and pass through the intersection.

[0091] In the embodiment of the present invention, step S2, obtaining all fleet information in the intersection area through the central controller, specifically includes the following:

[0092] All autonomous vehicles entering the intersection are equipped with wireless communicators, dedicated short-range communication autonomous vehicles and cellular devices to support vehicle communication. At the same time, it is assumed that there is no delay in communication between vehicles and between the central controller and the head vehicle of the team. In the present invention, the headway, headway distance, speed and other status information between vehicles in the team are always consistent and the status information is changed synchronously. Therefore, the team is regarded as a rectangular block, recorded as Compared to ordinary vehicles, which only change in length, the leader of the convoy broadcasts the convoy size - the number of vehicles or vehicle length, convoy speed, acceleration, and position - with the position of the lead vehicle representing the position of the entire convoy - to the central controller through the communication system, and the central controller stores and classifies all the acquired information.

[0093] The specific process of step S3, establishing a fleet traffic and variable speed limit strategy in the embodiment of the present invention is described as follows:

[0094] The basic parameters for the optimal traffic order calculation and variable speed limit control of the fleet are as follows:

[0095] 1) The length and width of each vehicle in the convoy are denoted as ι and w, and each vehicle or convoy satisfies the following second-order dynamics:

[0096]

[0097] In the formula represents the displacement of the vehicle's front bumper between the entrance to the control area and the current position, where d represents the four entrance lanes d = {N, S, W, E}, and the lane indexes of the entrance lanes are recorded from right to left as: r∈R = {0, 1, 2}, i∈I = {0, 1, 2, ···, p r} represents the i-th team or vehicle, Indicates speed, represents acceleration;

[0098] 2) There are three special moments when each formation enters the coordination zone from the central control zone. It is the moment when the front bumper of the leading vehicle enters the central control area. The moment when the front bumper enters the coordination zone, that is, the moment when the leading vehicle crosses the stop line. is the moment when the rear bumper of the last vehicle in the convoy leaves the coordination area, The interval between the three moments is described as: waiting time: Collaboration time: Driving time:

[0099] 3) Within the specified coordination time interval t∈[T, T+Δt], the number of convoys p on each entrance lane r∈R={0,1,2} d,r , use p d,r,i Indicates that according to the arrival sequence i∈I={0,1,2,···,p r}, each import channel d = {N, S, W, E} is polled.

[0100] In addition, the coordination process ensures the safety and efficiency of the convoy. Potential conflict points for convoys entering intersections include: Figure 4 As shown, eliminating conflict points is specifically described as:

[0101] 1) First of all, we must ensure that there is no preemption between convoys on the same entrance road section: convoys in the same lane cannot enter the control area at the same time. And convoys at different entrances entering the control area need to pay attention to conflicts, so there are Note that the right-turning convoys on the entrance lanes are not considered at this time, and will not affect other convoys. Also, d, d′, d″, d″′={N, S, W, E}, u, i′, `i, i″, i″ respectively correspond to different convoys on the corresponding entrance lanes, where i′, `i represent convoys on different lanes of the same entrance lane.

[0102] 2) There is a time gap between the front and rear convoys in the same lane, which is calculated by the central controller after the previous convoy passes the intersection and is recorded as And the gap between convoys from different directions is recorded as:

[0103] 3) The recommended speed for the fleet in the variable speed limit zone is Then the delay time of the convoy is described as the difference between the actual time when the convoy arrives at the central control area and the theoretical arrival time, which is calculated as follows:

[0104]

[0105] 4) The maximum time required to coordinate all vehicles at an intersection is defined as:

[0106]

[0107] 5) The maximum time required for coordination must meet the following requirements:

[0108] C max ≤ΔT+T min ,

[0109] In the coordination time interval t∈[T,T+Δt], T min is the minimum time interval between the arrival and start of each convoy.

[0110] The fleet traffic strategy and variable speed limit strategy establishment process and specific steps described in step S3 in the embodiment of the present invention are as follows:

[0111] Step S301: The fleet traffic strategy calculates the traffic order of each entrance road in the central control area according to the proposed rolling time domain algorithm:

[0112] The central controller calculates the optimal passage order of the fleet in the control area based on the rolling time domain algorithm. This part aims to minimize the maximum coordination time and maximum delay, obtain the time when the fleet enters the coordination area, and optimize the subsequent fleet speed recommendations and fleet size calculation plan;

[0113] Step a: Define the decision variable as the moment when the fleet enters the coordination zone: Lane number index r∈R={0,1,2}, lane fleet index i∈I={0,1,2,···,p r}; In addition, define the pass order as an intermediate variable:

[0114]

[0115] Step b: Define constraints:

[0116] 1) Different convoys on the same entrance and lane cannot enter the central control area at the same time, and the following conditions must be met:

[0117]

[0118] 2) To avoid lateral collisions, the following constraints must be met:

[0119] Letz=Z i,i′,`i,i″,i″′ ,

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126] In the formula Indicates the current moment of the fleet that first enters the coordination area in the next time domain;

[0127] 3) The intermediate variables satisfy the following constraints:

[0128]

[0129]

[0130] Where T inn and T ia x represents the arrival time and start time Minimum and maximum time interval between: M max represents the maximum number of vehicles in a convoy. Note that T max Used to prevent the vehicle from stopping, that is, to avoid the undesirable phenomenon of stop-and-go;

[0131] For example, there is a group i=1 consisting of 5 vehicles on lane r. and there are i=2 convoys of four vehicles behind in the same lane The reorganization information received now is three and four vehicles, so m r =2, recorded as {0, 1, 2} and {3, 4, 0, 1}, so That is V r,0 , V r,1 , V r,2 A new team was formed, and V r,3 , V r,4 Disintegrate from the original convoy and slow down, the V in the convoy behind r,0 , V r,1 At the same time from Add V to accelerate the disintegration r,3 , V r,4 A new team is then reorganized, and this method is then applied to other teams to reorganize and mark the team;

[0132] At this time, the fleet length is updated to

[0133] Step c: Setting the objective function. When considering the dual-criteria optimization problem of the maximum completion time of the intersection coordination solution and the maximum delay of all fleets, the following function expression is established:

[0134]

[0135] Step d: Use an exact algorithm to solve the combinatorial optimization problem and calculate That is, the moment when the convoy enters the coordination zone, and the convoy enters the center of the intersection and passes through it according to the sequence at that moment;

[0136] Step S302: After the convoy closest to the stop line of the intersection passes through the intersection according to the traffic order calculated in step S301, the central controller will obtain the available time slot and the corresponding status information of the next convoy on other entrance roads. The central controller integrates this information to obtain the recommended size and speed of the next convoy; the leader of the next convoy in the variable speed limit area synchronizes the adjustment command to the following vehicles through the roadside unit communication according to the adjustment status command broadcast by the central controller:

[0137] Step a: Determine the fleet size in the variable speed limit zone:

[0138] 1) When the minimum headway between vehicles in a convoy is set to h d , vehicle length ι, then each team p r,i The number of vehicles is:

[0139]

[0140] in It's the team p r,i The length of the lane number index r∈R={0,1,2}, the lane fleet index i∈I={1,2,···,p r}, so for all vehicles in the intersection area As a single individual, it can be recorded as

[0141] 2) The central controller transmits the recommended convoy size information to each leading vehicle and broadcasts it to the trailing vehicle. The trailing vehicles decelerate and disintegrate according to the information. The following formula can be used to represent the number of vehicles in the convoy:

[0142]

[0143]

[0144] Step b: Adjust the speed of the new fleet in the variable speed limit zone:

[0145] After receiving the speed suggestion, the leading vehicle will accelerate or decelerate to the target speed according to the situation of the team / vehicle in front, which is mainly divided into the following situations:

[0146] 1) Situation 1: When there are other convoys in the variable speed limit zone, the new convoy slows down to avoid collision. After the convoy ahead of it exits the variable speed limit zone, it accelerates to the recommended speed at maximum acceleration and then drives at a constant speed into the central control zone and passes through the intersection according to the calculated traffic order.

[0147]

[0148] Where v d,r,i-1 represents the original speed of the fleet in the variable speed limit area, a represents the original acceleration of the current fleet, Indicates the distance between the current convoy and the center of the intersection;

[0149] 2) Situation 2: When there are no other convoys in the variable speed limit zone, the new convoy only needs to adjust its speed and pass through at a constant speed;

[0150]

[0151] 3) Situation 3: There is no convoy blocking the variable speed limit area, but the convoy has already driven to the central control area, so it needs to slow down to pass;

[0152]

[0153] Step S303, the two steps mentioned above can be executed simultaneously and the subsequent convoy can be executed cyclically to obtain the optimal traffic order and the optimal convoy size and speed, ensuring that the convoy passes through the intersection safely and efficiently.

Claims

1. A method and system for cooperative passage of an autonomous driving fleet at an unsignalized intersection, characterized in that: The step S1 is to first construct an intersection scene model and classify the entire intersection area into functional areas; the step S2 is to obtain all fleet information in the intersection area through the central controller; the step S3 is to establish a fleet passage and variable speed limit strategy process, and the central controller calculates the optimal passage order of the fleet in the control area according to the rolling time domain algorithm, and then the fleet in the variable speed limit area receives the control command of the central controller to adjust the fleet and vehicle speed according to the passage time of the front fleet and the reserved gap; the step S4 is to pass through the control area in sequence according to the passage order calculated by the rolling time domain algorithm.

2. A method and system for cooperative passage of an autonomous driving fleet at an unsignalized intersection according to claim 1, characterized in that: The intersection scene constructed in step S1 is as follows: the intersection is symmetrical, each entrance road is marked as N, S, W, and E, and has three lanes respectively, marked as left turn, straight, and right turn; the intersection is divided into a free driving zone marked as FZ, a variable speed limit zone marked as VLZ, a central control zone marked as CZ, and a coordination zone marked as COZ. The range of the central control zone is within a radius of L from each entrance road segment to the center of the intersection. The area enclosed by the stop lines of each entrance road is called the coordination zone, which is square and has a width of W. The range of the variable speed limit zone is L from the central control zone on the intersection segment. v The area within the radius and outside the variable speed limit zone is a free driving zone.

3. The method and system for cooperative passage of an autonomous driving fleet at an unsignalized intersection according to claim 1, characterized in that: An intersection management controller is set at the intersection center of the central control area, denoted as the central controller. Intersection management control is a system that optimizes intersection traffic flow through automation and intelligent technology, aiming to improve the urban traffic environment by reducing traffic congestion, improving traffic safety and efficiency.

4. A method and system for cooperative passage of an autonomous driving fleet at an unsignalized intersection according to claim 2, characterized in that: When a convoy is in a variable speed limit zone, not only the speed but also the size of the convoy can be changed. However, individual vehicles cannot change lanes at will in this area and can only move longitudinally. At the same time, the convoy enters the central control area at a constant speed to avoid conflict points and pass intersections.

5. The method and system for cooperative passage of an autonomous driving fleet at an unsignalized intersection according to claim 1, characterized in that: In step S2, all the autonomous driving vehicles are equipped with wireless communication devices, dedicated short-range communication autonomous driving vehicles and cellular devices to support vehicle communication. In the present invention, the headway, headway distance, speed and other status information between the vehicles in the team are always consistent and the state information is changed synchronously. Therefore, the team is regarded as a rectangular block, which is recorded as Compared with ordinary vehicles that only change in length, the leader of the fleet will use the fleet size, such as the number of vehicles or vehicle length, fleet speed, acceleration, and position - using the position of the lead vehicle to represent the position of the entire fleet, and then broadcast it to the central controller through the communication system to store and classify all available information.

6. The method and system for cooperative passage of an autonomous driving fleet at an unsignalized intersection according to claim 1, characterized in that: The basic parameters for the optimal traffic order calculation and variable speed limit control of the fleet are as follows: 1) The length and width of each vehicle in the convoy are denoted as ι and w, and each vehicle or convoy satisfies the following second-order dynamics: In the formula represents the displacement of the front bumper of the leading vehicle in the convoy between the entrance of the control area and the current position, where d represents the four entrance lanes d = {N, S, W, E}, and the lane indexes of the entrance lanes are recorded from right to left as: r∈R = {0, 1, 2}, i∈I = {0, 1, 2, ···, p r } represents the i-th team, represents the convoy speed, represents the convoy acceleration; 2) There are three special moments when each formation enters the coordination zone from the central control zone. It is the moment when the front bumper of the leading vehicle enters the central control area. The moment when the front bumper enters the coordination zone, that is, the moment when the leading vehicle crosses the stop line. is the moment when the rear bumper of the last vehicle in the convoy leaves the coordination area, The interval between the three moments is described as: waiting time: Collaboration time: Driving time: 3) Within the specified coordination time interval t∈[T, T+Δt], the number of convoys p on each entrance lane r∈R={0,1,2} d,r , use p d,r,i Indicates that according to the arrival sequence i∈I={0,1,2,···,p r }, each import channel d = {N, S, W, E} is polled.

7. The method and system for cooperative passage of an autonomous driving fleet at an unsignalized intersection according to claim 1, characterized in that: The requirements for ensuring the safety and efficiency of the fleet during the coordination process are described as follows: 1) First of all, we must ensure that there is no preemption between convoys on the same entrance road section: convoys in the same lane cannot enter the control area at the same time. And convoys at different entrances entering the control area need to pay attention to conflicts, so there are Note that the right-turning convoys on the entrance lanes are not considered at this time, and will not affect other convoys. Also, d, d′, d″, d″′={N, S, W, E}, i, i′, `i, i″, i″ respectively correspond to different convoys on the corresponding entrance lanes, where i′, `i represent convoys on different lanes of the same entrance lane. 2) There is a time gap between the front and rear convoys in the same lane, which is calculated by the central controller after the previous convoy passes the intersection and is recorded as And the gap between convoys from different directions is recorded as: 3) The recommended speed for the fleet in the variable speed limit zone is Then the delay time of the convoy is described as the difference between the actual time when the convoy arrives at the central control area and the theoretical arrival time, which is calculated as follows: 4) The maximum time required to coordinate all vehicles at an intersection is defined as: 5) The maximum time required for coordination must meet the following requirements: C max ≤ΔT+T min , In the coordination time interval t∈[T,T+Δt], T min is the minimum time interval between the arrival and start of each convoy.

8. The method and system for cooperative traffic of an autonomous driving fleet at an unsignalized intersection according to claim 1, characterized in that: The process and specific steps for establishing the fleet traffic strategy and variable speed limit strategy described in step S3 are as follows: Step S301: The fleet traffic strategy calculates the traffic order of each entrance road in the central control area according to the proposed rolling time domain algorithm: The central controller calculates the optimal passage order of the fleet in the control area based on the rolling time domain algorithm. This part aims to minimize the maximum coordination time and maximum delay, obtain the time when the fleet enters the coordination area, and optimize the subsequent fleet speed recommendations and fleet size calculation plan; Step a: Define the decision variable as the moment when the fleet enters the coordination zone: Lane number index r∈R={0,1,2}, lane fleet index i∈I={0,1,2,···,p r }; In addition, define the pass order as an intermediate variable: Step b: Define constraints: 1) Different convoys on the same entrance and lane cannot enter the central control area at the same time, and the following conditions must be met: 2) To avoid lateral collisions, the following constraints must be met: Letz=Z i,i′,`i,i″,i″′ 。 In the formula Indicates the current moment of the fleet that first enters the coordination area in the next time domain; 3) The intermediate variables satisfy the following constraints: Where T min and T max Arrival time and start time Minimum and maximum time interval between: M max represents the maximum number of vehicles in a fleet. Note that T max Used to prevent the vehicle from stopping, that is, to avoid the undesirable phenomenon of stop-and-go; Step c: Setting the objective function. When considering the dual-criteria optimization problem of the maximum completion time of the intersection coordination solution and the maximum delay of all fleets, the following function expression is established: Step d: Use an exact algorithm to solve the combinatorial optimization problem and calculate That is, the moment when the convoy enters the coordination zone, and the convoy enters the center of the intersection and passes through it according to the sequence at that moment; Step S302: After the convoy closest to the stop line of the intersection passes through the intersection according to the traffic order calculated in step S301, the central controller will obtain the available time slot and the corresponding status information of the next convoy on other entrance roads. The central controller integrates this information to obtain the recommended size and speed of the next convoy; the leader of the next convoy in the variable speed limit area synchronizes the adjustment command to the following vehicles through the roadside unit communication according to the adjustment status command broadcast by the central controller: Step a: Determine the fleet size in the variable speed limit zone: 1) When the minimum headway between vehicles in a convoy is set to h d , vehicle length ι, then each team p r,i The number of vehicles is: in It's the team p r,i The length of the lane number index r∈R={0,1,2}, the lane fleet index i∈I={1,2,···,p r }, so for all vehicles in the intersection area As a single individual, it can be recorded as 2) The central controller transmits the recommended convoy size information to each leading vehicle and broadcasts it to the trailing vehicle. The trailing vehicles decelerate and disintegrate according to the information. The following formula can be used to represent the number of vehicles in the convoy: Step b: Adjust the speed of the new fleet in the variable speed limit zone: After receiving the speed suggestion, the leading vehicle will accelerate or decelerate to the target speed according to the situation of the team / vehicle in front, which is mainly divided into the following situations: 1) Situation 1: When there are other convoys in the variable speed limit zone, the new convoy slows down to avoid collision. After the convoy ahead of it exits the variable speed limit zone, it accelerates to the recommended speed at maximum acceleration and then drives at a constant speed into the central control zone and passes through the intersection according to the calculated traffic order. Where v d,r,i-1 represents the original speed of the fleet in the variable speed limit area, a represents the original acceleration of the current fleet, Indicates the distance between the current convoy and the center of the intersection; 2) Situation 2: When there are no other convoys in the variable speed limit zone, the new convoy only needs to adjust its speed and pass through at a constant speed; 3) Situation 3: There is no convoy blocking the variable speed limit area, but the convoy has already driven to the central control area, so it needs to slow down to pass; Step S303, the two steps mentioned above can be executed simultaneously and the subsequent convoy can be executed cyclically to obtain the optimal traffic order and the optimal convoy size and speed, ensuring that the convoy passes through the intersection safely and efficiently.

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