Vehicle Cooperative Merging Control Method, Device and Storage Medium for Expressway Mixed Traffic Flow

Abstract

The present invention discloses a vehicle collaborative merging control method, device and storage medium for highway mixed traffic flow. The control method includes: determining the real-time merging sequence of vehicles; if there is no HDV in the merging sequence, based on the principle that CAV yields to CAV, controlling the collaborative merging between CAV-CAV through a speed control model; if there is HDV in the merging sequence but no continuous HDV, based on the principle that CAV yields to HDV, controlling the collaborative merging between CAV-HDV through a speed control model; if there is continuous HDV in the merging sequence, based on the principle that the ramp HDV yields to the main line HDV, prompting the HDV to travel at a preset speed through an intelligent variable speed indicator board, and guiding the HDV to merge smoothly. The present invention optimizes the merging order of vehicles in the merging area, and proposes a corresponding collaborative merging control algorithm, which improves the merging efficiency and reduces fuel consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent transportation control, and relates to a vehicle collaborative merging control method, device and storage medium for highway mixed traffic flow. Background Art

[0002] The ramp merging area is a high-incidence area of traffic congestion and traffic accidents, becoming a bottleneck restricting traffic operation. The development of vehicle-road collaborative technology provides a new method for alleviating the ramp merging problem. Connected and automated vehicles (CAVs) can coordinate the operation of vehicles in the merging area through vehicle-to-vehicle (V2V) communication and vehicle-to-infrastructure (V2X) communication, thereby improving traffic efficiency and reducing traffic accidents.

[0003] Currently, most domestic research on vehicle collaborative merging methods assumes a pure connected environment, that is, only considering the driving of CAVs on highways and using optimal control methods for modeling research. However, due to the limitations of communication and vehicle technology levels, the development of a pure connected environment requires a long time. The management of a mixed traffic scenario (that is, both CAVs and human-driven vehicles HDVs exist on the road) is an inevitable problem in the development of CAVs. Therefore, researching the control of intelligent connected vehicles in a mixed traffic scenario where intelligent connected vehicles and human-driven vehicles coexist has more significant practical significance. In a mixed traffic scenario, human-driven vehicles are not controlled and their information cannot be predicted in advance, which is an external disturbance to intelligent connected vehicles and brings difficulties to the ramp merging of intelligent connected vehicles. Under mixed traffic conditions, it is necessary to design a coordination strategy that can adapt to both CAVs and human-driven vehicles. Summary of the Invention

[0004] To solve the above problems, the present invention provides a vehicle collaborative merging control method for highway mixed traffic flow, which optimizes the merging order of vehicles in the merging area, solves the problem that the traditional fixed merging sequence cannot adapt to the random disturbance of HDV driving behavior, and proposes a corresponding cooperative merging control algorithm, improving the merging efficiency, reducing fuel consumption, and solving the problems existing in the prior art.

[0005] The second object of the present invention is to provide an electronic device.

[0006] The third object of the present invention is to provide a computer storage medium.

[0007] The technical solution adopted by the present invention is a vehicle collaborative merging control method for highway mixed traffic flow, including the following steps:

[0008] Step 1: Determine the real-time vehicle merging sequence;

[0009] Step 2: If there is no HDV in the merging sequence, based on the principle that CAV yields to CAV, control the cooperative merging between CAV-CAV through the speed control model; if there is HDV in the merging sequence but no consecutive HDV, based on the principle that CAV yields to HDV, control the cooperative merging between CAV-HDV through the speed control model to enable the ramp vehicles to smoothly merge into the main line; if there is consecutive HDV in the merging sequence, based on the principle that the ramp HDV yields to the main line HDV, prompt the HDV to travel at the preset speed through the intelligent variable speed indicator board to guide the HDV to merge smoothly.

[0010] Further, in the above Step 1, determining the real-time vehicle merging sequence specifically includes:

[0011] When the ramp vehicle enters the cooperative control area, the roadside unit collects vehicle information. If the ramp vehicle arriving at the merging decision point is a CAV and the main line vehicle in the cooperative control area is a CAV, compare the time for the main line vehicle and the ramp vehicle to reach the merging point, and the one with the shorter time obtains the right of way; if the ramp vehicle arriving at the merging decision point is a CAV and the main line vehicle in the cooperative control area is not a CAV, the main line vehicle obtains the right of way; if the ramp vehicle arriving at the merging decision point is not a CAV and the main line vehicle in the cooperative control area is a CAV, the ramp vehicle obtains the right of way; if the ramp vehicle arriving at the merging decision point is not a CAV and the main line vehicle in the cooperative control area is not a CAV, the main line vehicle obtains the right of way; traverse all vehicles according to the above rules, output the merging sequence, and determine the position of the ramp vehicle in the merging sequence; update the merging sequence at regular time intervals to reduce the influence of HDV volatility.

[0012] Further, in the above Step 2, controlling the cooperative merging between CAV-CAV specifically includes:

[0013] At any time t, when the current vehicle is a CAV i the time t merge,i for it to reach the merging area can be accurately obtained, and the time t i+1 for the following CAV merge,i+1 to reach the merging area can also be accurately obtained;

[0014] When the CAV i reaches the merging area, with the help of the mutual communication between CAVs, the speeds of the front and rear CAVs are made as equal as possible while ensuring a safe distance, that is, satisfying Equation (1):

[0015]

[0016] where is the CAV vehicle i at time tmerge,i The speed at time is the speed of CAV vehicle i at time t merge,i The position at time is the position of CAV vehicle i + 1 at time t merge,i The speed at time is the position of CAV vehicle i + 1 at time t merge,i The time; t merge,i is the time when CAV vehicle i arrives at the merging area, t merge,i+1 is the time when CAV vehicle i + 1 arrives at the merging area;

[0017] If t merge,i+1 -t merge,i ≤T min,1 , that is, when the time difference between the two vehicles passing through the merging point is less than the minimum headway time when the main - line and ramp vehicles merge, to avoid a collision between CAV i+1 and CAV i , CAV i+1 chooses to decelerate and leave enough safety distance. The acceleration a i+1 of CAV i+1 is determined by Equation (2):

[0018] a i+1 = min{min(a merge , d comfort ), a norm} (2)

[0019] where a norm is the conventional acceleration determined by the driving rules, d comfort is the comfortable acceleration, and a merge is the acceleration required for merging determined according to the motion equation, as shown in Equation (3):

[0020]

[0021] T min,1 represents the minimum headway time when the main - line CAV and the ramp CAV merge.

[0022] Furthermore, in the second step, controlling the collaborative merging between CAV - HDV is specifically as follows:

[0023] When the leading vehicle is an HDV n , estimate the arrival time of the HDV n through the roadside unit or the surrounding CAVs, as shown in Equation (4);

[0024]

[0025] where t merge is the estimated arrival time of the nth vehicle, i.e., the HDVn , the time to reach the merging area; t0 is the time when the vehicle is detected by the detector, p n,t0 is the HDV n is the position of the HDV from the starting point of the cooperative control area at time t0, v n,t0 is the HDV n is the speed at time t0; L is the length of the cooperative control area;

[0026] Time t merge of the CAV i+1 position is determined by the position and speed detected at the detection time t0, see Equation (5):

[0027]

[0028] represents the position of the CAV at time t0 i+1 position, represents the position of the CAV at time t0 i+1 speed;

[0029] The ramp vehicle at time t merge relative to the main-line vehicle CAV i+1 merging safety area and the vehicle CAV i+1 speed is related:

[0030]

[0031] Among them, x up , x down are the upstream and downstream boundaries of the merging safety area of the vehicle CAV i+1 respectively, x merge is the upstream boundary of the merging area, T min,2 is the minimum headway time when the CAV and HDV merge;

[0032] When falls into the interval [x up , x down , to avoid collision between the CAV i+1 and the vehicle in front, the CAV i+1 chooses to decelerate and give enough safety distance. The speeds of the main-line vehicle and the ramp vehicle should be as equal as possible, that is, satisfy Equation (7):

[0033]

[0034] Among them, is the HDV n at time t merge speed, is the CAV i+1 at time tmerge The speed at

[0035] CAV i+1 The acceleration a i+1 Is determined by Equation (8):

[0036]

[0037] Wherein, a norm Is the conventional acceleration determined by the driving rules, d comfort Is the comfort acceleration, a merge Is the acceleration required for merging determined according to the motion equation, see Equation (9):

[0038]

[0039] Wherein, Is the time t merge When the HDV n Position.

[0040] Furthermore, in the second step, the method for determining the preset speed prompted by the intelligent variable speed sign for the HDV:

[0041] Vehicles driving on the main line regard the vehicle in front as the leading vehicle and follow the car-following model until reaching the merging area; once entering the merging area, the vehicle driver evaluates whether there are vehicles merging in front. If there are merging vehicles, the merging vehicle serves as the new leading vehicle; the speed of the main line vehicle HDV m-1 And the ramp vehicle HDV m Should be ensured to be as equal as possible, that is, satisfy Equation (10):

[0042]

[0043] Wherein, Is the speed of the main line vehicle HDV m-1 At time t merge,m-1 When, Is the speed of the ramp vehicle HDV m At time t merge,m-1 When, t merge，m-1 Is the speed of the main line vehicle HDV m-1 Time to reach the merging area;

[0044] To ensure safety between vehicles, the time for the ramp vehicle HDV m To reach the merging area needs to be greater than or equal to Δt, that is, when the ramp vehicle HDV m Reaches the merging area, the new leading vehicle has passed through the merging area and satisfies the safety distance; Δt is determined by Equation (11):

[0045] Δt = t merge,m-1 + Tmin,3 +t f (11)

[0046] where, Δt represents the safe time when the ramp vehicle HDV m arrives at the merging area without collision; T min,3 is the minimum headway time when the mainline HDV and the ramp HDV merge, and t f is the reaction time required for the driver of the HDV to receive information and make a reaction;

[0047] If the ramp vehicle HDV m arrives at the merging area at a time greater than or equal to Δt, the acceleration of the ramp vehicle HDV m is determined by Equation (12):

[0048] a m = min{min(a merge , d comfort ), a norm} (12)

[0049] where, a m represents the acceleration of the ramp vehicle HDV m arriving at the merging area to ensure safety between vehicles and avoid collisions; a norm is the conventional acceleration determined by the driving rules, d comfort is the comfort acceleration, and a merge is the acceleration required for merging determined according to the motion equation, see Equation (13):

[0050]

[0051] is the position of the mainline vehicle HDV m-1 at time t merge,m-1 , is the position of the ramp vehicle HDV m at time t merge,m-1 , and t0 is the time when the vehicle is detected by the detector;

[0052] Since the driver cannot guarantee the acceleration of vehicle driving, the speed limit of HDV is determined according to Equations (12) and (13):

[0053]

[0054] where, v limit is the speed limit of the ramp vehicle HDV m , and it is assumed that the HDV travels at the speed and acceleration proposed by the control algorithm; t merge，m is the time when the ramp vehicle HDV m arrives at the merging area.

[0055] An electronic device implements vehicle collaborative merging control by using the above method.

[0056] A computer storage medium stores at least one program instruction, and the at least one program instruction is loaded and executed by a processor to implement the above vehicle collaborative merging control method.

[0057] The beneficial effects of the present invention are as follows:

[0058] The present invention is directed to a traffic scenario where connected and autonomous vehicles (CAVs) and human-driven vehicles (HDVs) coexist, and proposes a method for vehicle collaborative merging control on highway on-ramps, including a hierarchical collaborative merging framework for highway on-ramps. This framework integrates real-time vehicle merging sequence scheduling and collaborative merging algorithms, optimizes the merging order of vehicles in the merging area through real-time vehicle merging sequence, and solves the problem that traditional fixed merging sequences cannot adapt to the random perturbations of HDV driving behaviors; it is adjusted in real time according to vehicle types and vehicle states, improving the flexibility and autonomy of vehicles during the merging process, and facilitating the guarantee of the safety of the on-ramp merging area in a mixed traffic environment.

[0059] The present invention separately establishes collaborative merging control algorithms for CAV-CAV, CAV-HDV, and HDV-HDV, describes the merging control under mixed traffic flow through a mathematical model, and improves the previous situation where only the merging of CAV-HDV and HDV-HDV under mixed traffic flow was simulated through simulation; the algorithm is simple, and while ensuring safety, it can effectively avoid the problem of computational explosion. The results show that the total delay and travel time of the merging control proposed by the present invention are both reduced, the operating efficiency during the merging process can be effectively improved, and there is a greater advantage in fuel economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0061] Figure 1 It is a diagram of the on-ramp merging scenario of a highway in a mixed traffic flow environment.

[0062] Figure 2 It is a hierarchical structure diagram of the vehicle collaborative merging method in a mixed traffic flow environment.

[0063] Figure 3 It is a flowchart of the merging sequence scheduling of the present invention.

[0064] Figure 4It is a schematic diagram of the scenario of cooperative merging between CAVs.

[0065] Figure 5 It is a schematic diagram of the scenario of cooperative merging between CAVs and HDVs.

[0066] Figure 6 It is a schematic diagram of the scenario of guiding the merging of HDVs.

[0067] Figure 7 It is a schematic diagram of the simulation scenario adopted in the embodiment of the present invention.

[0068] Figure 8a It is a vehicle trajectory diagram before using the merging strategy in the embodiment of the present invention.

[0069] Figure 8b It is a vehicle trajectory diagram after using the merging strategy in the embodiment of the present invention.

[0070] Figure 9a It is a main-line vehicle speed change diagram before using the merging strategy in the embodiment of the present invention.

[0071] Figure 9b It is a main-line vehicle speed change diagram after using the merging strategy in the embodiment of the present invention.

[0072] Figure 9c It is a ramp vehicle speed change diagram before using the merging strategy in the embodiment of the present invention.

[0073] Figure 9d It is a ramp vehicle speed change diagram after using the merging strategy in the embodiment of the present invention.

[0074] Figure 10a It is a main-line vehicle acceleration change diagram before using the merging strategy in the embodiment of the present invention.

[0075] Figure 10b It is a main-line vehicle acceleration change diagram after using the merging strategy in the embodiment of the present invention.

[0076] Figure 10c It is a ramp vehicle acceleration change diagram before using the merging strategy in the embodiment of the present invention.

[0077] Figure 10d It is a ramp vehicle acceleration change diagram after using the merging strategy in the embodiment of the present invention.

[0078] Figure 11 It is a vehicle total delay diagram comparing different merging strategies in the embodiment of the present invention.

[0079] Figure 12 It is a vehicle total travel time diagram comparing different merging strategies in the embodiment of the present invention.

[0080] Figure 13a is the average PM consumption graph for comparing different merging strategies in the embodiments of the present invention X Consumption graph

[0081] Figure 13b is the average NO consumption graph for comparing different merging strategies in the embodiments of the present invention X Consumption graph

[0082] Figure 13c is the average fuel consumption graph for comparing different merging strategies in the embodiments of the present invention

[0083] Figure 13d is the average CO2 consumption graph for comparing different merging strategies in the embodiments of the present invention

[0084] Figure 14 is the energy consumption graph for comparing different lengths of cooperative control areas in the embodiments of the present invention

[0085] Figure 15 is the energy consumption graph for comparing the desired headways between different HDVs in the embodiments of the present invention

[0086] Figure 16 is the energy consumption graph for comparing the desired headways between different CAVs in the embodiments of the present invention Detailed implementation manners

[0087] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention

[0088] Embodiment

[0089] A method for collaborative merging of on-ramp vehicles on a highway considering mixed traffic flow is as Figure 1-2 shown, and is specifically carried out according to the following steps

[0090] Step 1: Determination of the vehicle merging sequence

[0091] To determine the optimal order for vehicles to pass through the merging point, based on the "first in, first out" and "main line priority" rules and considering the characteristics of the dynamic changes in vehicle states, a method for determining the real-time merging sequence is proposed, as Figure 3As shown in the figure, when ramp vehicles enter the cooperative control area, the roadside unit collects vehicle information, starts calculating the time for the vehicle to reach the merging point, and compares it with the time for the main-line vehicles in the cooperative control area to reach the merging point. If the ramp vehicle arriving at the merging decision point is a CAV and the main-line vehicle in the cooperative control area is a CAV, compare the times for the main-line vehicle and the ramp vehicle to reach the merging point, and the one with the shorter time gets the right of way; if the ramp vehicle arriving at the merging decision point is a CAV and the main-line vehicle in the cooperative control area is not a CAV, the main-line vehicle gets the right of way; if the ramp vehicle arriving at the merging decision point is not a CAV and the main-line vehicle in the cooperative control area is a CAV, the ramp vehicle gets the right of way; if the ramp vehicle arriving at the merging decision point is not a CAV and the main-line vehicle in the cooperative control area is not a CAV, the main-line vehicle gets the right of way; traverse all vehicles according to the above rules, output the merging sequence, and determine the position of the ramp vehicle in the merging sequence. When both the main-line vehicle and the ramp vehicle are HDVs, according to the principle of "main line priority", the main-line vehicle gets the priority right of way. At the same time, to reduce the influence of the volatility of HDVs, the merging sequence will be adjusted in real time, that is, updated at regular time intervals.

[0092] Step 2: Vehicle merging sequence scheduling algorithm, as Figure 2 shown, if there is no HDV in the merging sequence, based on the principle that CAV yields to CAV, control the cooperative merging between CAV-CAV through the speed control model; if there is an HDV in the merging sequence but no consecutive HDVs, based on the principle that CAV yields to HDV, control the cooperative merging between CAV-HDV through the speed control model, so that the ramp vehicle smoothly merges into the main line and achieves efficient and stable merging; if there are consecutive HDVs in the merging sequence (HDV is followed by HDV in the merging sequence), based on the principle that the ramp HDV yields to the main-line HDV, prompt the HDV to travel at the preset speed through the intelligent variable speed indicator board, guide the HDV to merge smoothly, avoid the influence of the volatility of HDVs on merging, and improve the merging efficiency.

[0093] The cooperative merging between CAV-CAV, as Figure 4 shown:

[0094] At any time t, when the current vehicle is a CAV i its time t merge,i to reach the merging area can be accurately obtained. The following CAV i+1 's time t merge,i+1 to reach the merging area can also be accurately obtained.

[0095] When the CAV i reaches the merging area, to ensure safety and improve efficiency, with the help of the mutual communication between CAVs, the speeds of the front and rear CAVs should be as equal as possible and a safe distance should be ensured, that is, the following formula is satisfied:

[0096]

[0097] wherein, is the speed of CAV vehicle i (CAV i ) at time t merge,i , is the position of CAV vehicle i at time t merge,i , T min,1 is the minimum headway when the main-line CAV and ramp CAV merge; is the speed of CAV vehicle i+1 (CAV i+1 ) at time t merge,i , is the position of CAV vehicle i+1 at time t merge,i , t merge,i is the time when CAV vehicle i reaches the merging area, t merge,i+1 is the time when CAV vehicle i+1 reaches the merging area. Due to the characteristics of CAV, the time when it reaches the merging area can be accurately obtained without repeated prediction.

[0098] If t merge,i+1 - t merge,i ≤ T min,1 , that is, when the time difference between the front and rear vehicles passing through the merging point is less than the minimum headway when the main-line and ramp vehicles merge, to avoid a collision between CAV i+1 and CAV i , CAV i+1 has two options: Option 1, decelerate to leave enough safety distance; Option 2, accelerate to pass through the merging safety area in advance. However, in actual operation, although CAV i+1 can transmit acceleration information to the vehicle in front and accelerate together with the vehicle in front, in a mixed traffic situation, the vehicle in front is not necessarily a CAV and may not be able to accept the information transmitted by CAV i+1 . Therefore, it is difficult to ensure enough acceleration distance. So only Option 1 is considered.

[0099] To achieve Option 1, the acceleration a i+1 of CAV i+1 is determined by the following formula:

[0100] a i+1 = min{min(a merge , d comfort ), a norm} (2)

[0101] wherein, a norm is the conventional acceleration determined by the driving rules, d comfort is the comfortable acceleration, a mergeThe acceleration required for the merging flow determined according to the motion equation is as shown in Equation (3):

[0102]

[0103] Equation (3) is used to determine the acceleration to avoid collisions between two consecutive CAVs.

[0104] The cooperative merging between CAV and HDV is as Figure 5 shown:

[0105] When the leading vehicle is an HDV n the roadside unit or surrounding CAVs are used to estimate the arrival time of the HDV n as shown in Equation (4). Since it is difficult to predict the speed of the HDV for a long time, the arrival time of the HDV at the merging area needs to be re-evaluated at regular time intervals.

[0106]

[0107] where t merge is the predicted arrival time of the nth vehicle (HDV n ) at the merging area. Since it is difficult to predict the speed of the HDV for a long time, the arrival time of the HDV at the merging area needs to be re-evaluated at regular time intervals; t0 is the time when the vehicle is detected by the detector, is the position of vehicle n from the starting point of the cooperative control area at time t0, is the speed of vehicle n at time t0; L is the length of the cooperative control area.

[0108] The position of the CAV merge at time t i+1 can be determined by its position and speed detected at time t0, as shown in Equation (5):

[0109]

[0110] represents the position of the CAV i+1 at time t0,

[0111] i+1 represents the speed of the CAV

[0112] The merging safety zone of the ramp vehicle relative to the mainline vehicle CAV merge at time t i+1 is related to the speed of the vehicle CAV i+1 :

[0112]

[0113] where x up 、xdown are the upstream and downstream boundaries of the merging safety zone of vehicle CAV i+1 , x is the upstream boundary of the merging area, and T merge is the minimum headway when CAV and HDV merge. min,2 When

[0114] falls into the interval [x , x up , x down , to avoid collision between CAV i+1 and the vehicle in front, CAV i+1 also faces similar choices and problems as in "cooperative merging between CAV-CAV". Therefore, it will not be elaborated here, and only option one is considered.

[0115] Meanwhile, to ensure merging efficiency and safety, it is desired that the speeds of the main-road vehicles and ramp vehicles should be as equal as possible during the merging time, that is, the following formula is satisfied:

[0116]

[0117] where is the speed of HDV n at time t merge , and is the speed of CAV i+1 at time t merge .

[0118] When falls into the interval [x up , x down , CAV i+1 decelerates and yields, and its acceleration is determined by the following formula:

[0119] a i+1 = min{min(a merge , d comfort ), a norm} (8)

[0120] where a merge is the acceleration required for merging determined according to the motion equation, as shown in the following formula.

[0121]

[0122] where is the position of HDV merge at time t n .

[0123] The ramp HDV yields to the main-road HDV. As Figure 6 shown, the merging control algorithm for HDV:

[0124] The vehicle driving on the main line regards the vehicle in front as a leading vehicle and follows the car-following model until it reaches the merging area; once it enters the merging area, the vehicle driver evaluates whether there are vehicles merging in front. If there are merging vehicles, the merging vehicle becomes its new leading vehicle; the HDV driving on the ramp will consider the vehicle in front of it as its leader until it reaches the cooperative control area. After arrival, the roadside unit determines the merging control strategy of the HDV based on the vehicle merging sequence information. The driver receives the acceleration and deceleration information transmitted by the roadside unit through methods such as in-vehicle broadcasts and roadside variable speed limit signs, and conducts vehicle speed control guidance.

[0125] From the vehicle merging sequence, it can be seen that the ramp HDV follows the "main road priority" principle. Therefore, the new leading vehicle of the ramp vehicle HDV m must be an HDV. To ensure the efficiency of merging, the speeds of the main line HDV m-1 and the ramp HDV m should be kept as equal as possible, that is, satisfying the following formula:

[0126]

[0127] To ensure the safety between vehicles, the time t for the ramp vehicle HDV m to reach the merging area needs to satisfy the constraint t≥Δt, that is, when the ramp vehicle HDV m reaches the merging area, the new leading vehicle has already passed through the merging area and satisfied the safety distance. The solution of Δt is as follows:

[0128] Δt = t merge,m-1 +T min,3 +t f (11)

[0129] Among them, Δt represents the safety time when there is no collision when the ramp vehicle HDV m reaches the merging area; t merge,m-1 is the time for the main line vehicle HDV m-1 to reach the merging area, T min,3 is the minimum headway time when the main line HDV and the ramp HDV merge, and t f is the reaction time required for the driver of the HDV to receive information and make a reaction.

[0130] If the constraint t≥Δt is satisfied, the acceleration of the ramp vehicle HDV m is determined by the following formula:

[0131] a m = min{min(a merge ,d comfort ),a norm} (12)

[0132] Among them, a mIt is shown that to ensure safety between vehicles and avoid collisions, the ramp vehicle HDV m reaches the acceleration at the merging area.

[0133] a merge is the acceleration required for merging determined according to the motion equation, as follows:

[0134]

[0135] is the mainline vehicle HDV m-1 at time t merge,m-1 position, is the ramp vehicle HDV m at time t merge,m-1 position, t0 is the time when the vehicle is detected by the detector;

[0136] Since the driver cannot guarantee the acceleration of the vehicle, the HDV speed limit is determined according to Eqs. (12) and (13):

[0137]

[0138] where, v limit is the vehicle speed limit of the ramp vehicle HDV m , and it is assumed that the HDV travels at the speed and acceleration proposed by the control algorithm, t merge，m is the time when the ramp vehicle HDV m reaches the merging area.

[0139] If the vehicle does not follow the guidance information, the ramp vehicle may not be able to safely pass through the merging point, and can only decelerate and stop to avoid lateral collisions, waiting for the next available gap to re-evaluate the merging conditions. Once the vehicle merges, it continues to follow the car-following model to try to maintain a safe distance from the new leading vehicle on the main road.

[0140] T min,1 、T min,2 、T min,3 The difference is the different time headways required for different vehicle groups to ensure safe merging between the front and rear vehicles; the differences between the three control algorithms are reflected in Eqs. (3), (9) and (13). Since the vehicle groups and vehicle types for cooperative merging are different, different factors need to be considered according to the characteristics between their vehicles, and the calculation formulas for their required safe accelerations are different.

[0141] Embodiments of the present invention are directed to a traffic scenario where connected and automated vehicles (CAVs) and human-driven vehicles (HDVs) are mixed, and a hierarchical cooperative merging framework for highway on-ramps is proposed. This framework integrates a merging sequence scheduling algorithm and a cooperative merging algorithm, and adjusts them in real time according to vehicle types and vehicle states. With merging safety as a constraint condition and efficiency improvement as the goal, cooperative merging control algorithms for CAV-CAV, CAV-HDV, and HDV-HDV are established respectively. The algorithms are simple, can effectively avoid the problem of computational explosion, avoid the significant increase in computational cost as the number of vehicles increases, have strong controllability, and solve the problem that traditional fixed merging sequences cannot adapt to the random perturbations of HDV driving behaviors. The cooperative merging algorithm includes a speed control model and a speed guidance model. The speed control model is used for cooperative merging between CAV-CAV and CAV-HDV, and by controlling the speed of CAVs, smooth merging of ramp vehicles into the main line is achieved. The speed guidance model is used for merging between HDV-HDV, and HDVs are prompted to drive at this speed through intelligent variable speed signs, and then merge smoothly. Embodiments of the present invention overcome the problems that the prior art rarely considers human-driven vehicles and the research based on a pure connected environment is too idealistic; it also overcomes the problem that current technologies for mixed traffic flow only consider trajectory optimization and do not consider merging sequence optimization.

[0142] Test example,

[0143] Use the simulation scenario as shown in Figure 7 as the test scenario. Assume that the length of the cooperative control area is 300 m, the length of the merging area is 30 m, the speed limit of the road is 30 m / s, the desired speeds of CAVs and HDVs are both 27 m / s, and the maximum acceleration and deceleration are both 2 m / s 2 , and the comfortable acceleration and deceleration of the vehicle is 1 m / s 2 . The minimum headway of CAVs is set to 1 s, and the minimum headway of HDVs is 1.6 s. When CAVs merge with CAVs, a headway of 1.5 s is maintained between the front and rear vehicles; when CAVs merge with HDVs, a headway of 2 s is maintained between the front and rear vehicles; when HDVs merge with HDVs, a headway of 2 s is maintained between the front and rear vehicles. The vehicle-following model used in the simulation is the IDM model, and the vehicle lateral motion model is the LC2013 model. When a vehicle enters the cooperative control area, its initial headway is shown in Table 1:

[0144] Table 1 Vehicle Initial Headway Table

[0145]

[0146] In Table 1, a-b, b-c, c-d, e-f, f-g, and g-h respectively represent the vehicle groups formed by pairwise pairing of vehicles when the vehicle enters the cooperative control area. a-b represents the vehicle group formed by the pairing between vehicle a and vehicle b, b-c represents the vehicle group formed by the pairing between vehicle b and vehicle c, c-d represents the vehicle group formed by the pairing between vehicle c and vehicle d, e-f represents the vehicle group formed by the pairing between vehicle e and vehicle f, f-g represents the vehicle group formed by the pairing between vehicle f and vehicle g, and g-h represents the vehicle group formed by the pairing between vehicle g and vehicle h.

[0147] Figure 8a It shows the movement trajectories of vehicles without control. In this case, there is no information transmission between vehicles, and vehicles all follow the "main line priority" rule and drive at the fastest speed as much as possible, resulting in too small a distance between ramp vehicles and main line vehicles when the ramp vehicles reach the merging area, and emergency braking occurs. Figure 8b It shows the vehicle trajectory diagram after applying the merging strategy. A certain distance is maintained between the ramp vehicles and the main line vehicles, and merging can be quickly completed in the merging area without emergency braking or collision. Comparing Figure 8a and Figure 8b It can be seen that after using the merging strategy, the ramp vehicles can pass through the merging area faster, and at the same time reduce the possibility of emergency braking.

[0148] Figure 9a - Figure 9d It is the speed change diagram before and after using the merging control method of the embodiment of the present invention. Both the main line and ramp vehicles enter the cooperative control area at the maximum speed as much as possible. In the cooperative control area, the vehicle speeds change and change rapidly because the vehicle groups in cooperative merging start to execute the merging strategy to ensure a safe gap. After the vehicle group completes the merging process, the vehicles all pass through the merging area, the vehicle speeds increase, and finally reach a stable state. Compared with the speed change of the main line vehicles without control, the speed of the main line vehicles fluctuates more after using the merging strategy. Except for the last vehicle d, the final speeds of other vehicles are slightly higher than those without control. Compared with the speed change of the ramp vehicles without control, the speed of the ramp vehicles fluctuates less after using the merging strategy, and there is no situation of decelerating to near 0, but the finally stable speed is slightly lower than that without control.

[0149] Figure 10a - 10d It is the acceleration change diagram before and after using the merging strategy. When using the merging strategy, as Figure 10b , 10d shown, after entering the cooperative control area, the accelerations of the rear vehicles in the vehicle group are all less than 0 to create a safe gap for merging. After leaving the merging area, the vehicle accelerations are all greater than 0, and gradually accelerate to the maximum speed. When the vehicle reaches the maximum speed, the vehicle acceleration decreases to 0 and maintains a uniform motion. The vehicle acceleration curves in the figure all satisfy the previous cooperative merging algorithm and its constraints. In contrast, asFigure 10a , Figure 10c As shown, without control, the acceleration change of ramp vehicles fluctuates more greatly and emergency braking occurs. However, the acceleration fluctuation of mainline vehicles is smaller than the acceleration change under the merging strategy. This is because under the condition of no control, vehicles merge according to the rule of giving priority to the mainline. Ramp vehicles decelerate first and yield to mainline vehicles. Therefore, the merging impact on mainline vehicles is smaller.

[0150] As Figure 11 shown, in terms of the total delay, the total delay of the merging strategy proposed in the embodiment of the present invention is 2016.26 s, which is reduced by 21.66% and 39.88% compared with the "first in, first out" strategy and the no-control situation respectively. It can be concluded that the merging strategy proposed in the embodiment of the present invention can effectively improve the operation efficiency during the merging process.

[0151] As Figure 12 shown, in terms of the total travel time, under the merging strategy proposed in the embodiment of the present invention, the total travel time of vehicles is 571.5 s, which is reduced by 7.5 s compared with the "first in, first out" strategy and reduced by 38.8 s compared with the no-control condition. This is because under the no-control condition, ramp vehicles need to stop and yield to mainline vehicles, resulting in an increase in the total travel time. The other two strategies both adjust the vehicle speed, but the merging strategy proposed in the embodiment of the present invention is a real-time regulation, which is more superior compared with the "first in, first out" strategy.

[0152] As Figure 13a - 13d shown, in terms of fuel economy, the results show that the average PM X , average NO X , average fuel consumption, and average CO2 of vehicles of the merging strategy proposed in the embodiment of the present invention are reduced by 6.26%, 7.11%, 5.16%, and 5.17% respectively compared with the "first in, first out" strategy; and are reduced by 11.76%, 18.74%, 7.62%, and 9.91% respectively compared with the no-control situation. It can be concluded that compared with the other two schemes, the merging strategy proposed in the embodiment of the present invention has greater advantages in fuel economy.

[0153] Figure 14Shows the energy consumption under different lengths of the cooperative control area. Research shows that within the range of 200m to 300m, the energy consumption decreases with the increase of distance and there is a minimum value. After reaching this minimum value, that is, after 300m, the energy consumption will gradually increase. Generally speaking, too long a length of the cooperative control area will not bring an improvement in fuel economy during the merging process. The reason is that as the cooperative control area grows, the traffic conditions faced by vehicles are more complex, and the vehicle merging sequence scheduling is more frequent, resulting in more frequent changes in vehicle speed. According to relevant literature, there is a monotonic relationship between energy consumption and acceleration. The frequent change in vehicle speed leads to a change in acceleration, which ultimately results in an increase in energy consumption.

[0154] Figure 15 Indicates that as the desired headway between HDVs increases, the energy consumption shows a downward trend. For every 0.5s increase in the desired headway between HDVs, the energy consumption decreases by approximately 0.7% to 3.4%. This is because as the headway between vehicles increases, during cooperative merging, the influence between the front and rear vehicles is smaller, resulting in smaller speed changes and thus reduced energy consumption.

[0155] As Figure 16 shown, as the desired headway between CAVs increases, the energy consumption also shows a downward trend. For every 0.5s increase in the desired headway between CAVs, the energy consumption decreases by approximately 0.2% to 1.3%. Comparing Figure 15 and Figure 16 it can be found that compared with the desired headway between HDVs, the influence of the desired headway between CAVs on fuel economy is less obvious. This may be because HDVs have random driving behavior disturbances and greater vehicle volatility. Increasing their headway can reduce the impact of the speed fluctuations of HDVs on other vehicles, bring greater traffic stability, and thus reduce the speed changes of other vehicles and energy consumption. While there is information exchange between CAVs, they can adjust their speeds collaboratively, and the impact of speed fluctuations on CAVs is smaller. Increasing the desired headway between CAVs will not bring greater changes.

[0156] In September 2020, China clearly put forward the goals of "carbon peak" in 2030 and "carbon neutrality" in 2060. In recent years, how to reduce carbon emissions in the transportation field has become a hot topic. Fuel economy can reflect the advantages of the present invention in reducing carbon emissions. For travelers, how to improve travel efficiency is their key concern, and delay and travel time are important evaluation indicators of travel efficiency. Therefore, the embodiments of the present invention use delay and travel time to evaluate vehicle travel efficiency.

[0157] When the vehicle collaborative merging control method described in the embodiments of the present invention is implemented in the form of software function modules and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the vehicle collaborative merging control method described in the embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, ROM, RAM, magnetic disks, or optical discs that can store program codes.

[0158] The foregoing is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are all included in the protection scope of the present invention.

Claims

1. A vehicle cooperative merging control method for highway mixed traffic flow, characterized in that Including the following steps: Step 1: Determine the real-time vehicle merging sequence; Step 2: If there is no HDV in the merging sequence, based on the principle that CAV yields to CAV, control the collaborative merging between CAV-CAV through the speed control model; if there is HDV in the merging sequence but no consecutive HDV, based on the principle that CAV yields to HDV, control the collaborative merging between CAV-HDV through the speed control model to enable the ramp vehicles to smoothly merge into the main line; If there is consecutive HDV in the merging sequence, based on the principle that the ramp HDV yields to the main line HDV, use the intelligent variable speed indicator to prompt the HDV to travel at the preset speed and guide the HDV to merge smoothly; CAV is a connected and autonomous vehicle, and HDV is a human-driven vehicle; In the above Step 1, to determine the real-time vehicle merging sequence, specifically: When the ramp vehicle enters the cooperative control area, the roadside unit collects vehicle information. If the ramp vehicle arriving at the merging decision point is a CAV and the main line vehicle in the cooperative control area is a CAV, compare the time for the main line vehicle and the ramp vehicle to reach the merging point, and the one with the shorter time obtains the right of way; if the ramp vehicle arriving at the merging decision point is a CAV and the main line vehicle in the cooperative control area is not a CAV, the main line vehicle obtains the right of way; if the ramp vehicle arriving at the merging decision point is not a CAV and the main line vehicle in the cooperative control area is a CAV, the ramp vehicle obtains the right of way; if the ramp vehicle arriving at the merging decision point is not a CAV and the main line vehicle in the cooperative control area is not a CAV, the main line vehicle obtains the right of way; Traverse all vehicles, output the merging sequence, and determine the position of the ramp vehicle in the merging sequence; Update the merging sequence at regular time intervals to reduce the influence of HDV volatility.

2. The vehicle collaborative merging control method for highway mixed traffic flow according to claim 1, characterized in that, In the above Step 2, to control the collaborative merging between CAV-CAV, specifically: At any time t, when the current vehicle is a CAV i the time t when it reaches the merging area merge,i can be accurately obtained, and the time t i+1 when the following vehicle CAV reaches the merging area merge,i+1 can also be accurately obtained; When the CAV i reaches the confluence area, with the help of the mutual communication between CAVs, the speeds of the two adjacent CAVs are equal, and a safe distance is ensured, that is, the formula (1) is satisfied: wherein, is the speed of CAV vehicle i at time t merge,i ; is the position of CAV vehicle i at time t merge,i ; is the speed of CAV vehicle i + 1 at time t merge,i ; is the position of CAV vehicle i + 1 at time t merge,i ; t merge,i is the time when CAV vehicle i arrives at the merging area, and t merge,i+1 is the time when CAV vehicle i + 1 arrives at the merging area; If t merge,i+1 -t merge,i ≤T min,1 , that is, when the time difference between the front and rear vehicles passing through the merging point is less than the minimum headway time during the merging of main-line and ramp vehicles, to avoid a collision between CAV i+1 and CAV i , CAV i+1 chooses to decelerate and leave enough safety distance. The acceleration a i+1 of CAV i+1 is determined by Equation (2): a i+1 = min{min(a merge , d comfort ), a norm} (2) where a norm is the normal acceleration determined by the driving rules, d comfort is the comfort acceleration, a merge is the acceleration required for merging determined according to the motion equation, as shown in Equation (3): T min,1 Indicates the minimum headway when the main-line CAV and the ramp CAV merge.

3. The vehicle cooperative merging control method for highway mixed traffic flow according to claim 1, wherein In the above Step 2, to control the collaborative merging between CAV-HDV, specifically: When the leading vehicle is an HDV n the arrival time of the HDV is estimated by the roadside unit or surrounding CAVs n as shown in Equation (4); where t merge is the predicted arrival time of the nth vehicle, i.e., the HDV n at the merging area; t0 is the time when the vehicle is detected by the detector, is the position of the HDV n from the starting point of the cooperative control area at time t0, is the speed of the HDV n at time t0; L is the length of the cooperative control area; Time t merge CAV at i+1 position is determined by the position and velocity detected at the detection time t0, as shown in Equation (5): Indicates the position of the CAV at time t0 i+1 ; Indicates the speed of the CAV at time t0 i+1 ; The ramp vehicle at time t merge with respect to the mainline vehicle CAV i+1 the merging safety zone of i+1 is related to the speed of the vehicle CAV: Among them, x up , x down are respectively the upstream and downstream boundaries of the merging safety zone of vehicle CAV i+1 , x merge is the upstream boundary of the merging zone, and T min,2 is the minimum headway when CAV and HDV merge; When falls within the interval [x up , x down , to avoid a collision between the CAV i+1 and the vehicle in front, the CAV i+1 chooses to decelerate and leave enough safety distance, and the speeds of the main-line vehicle and the ramp vehicle are equal, that is, satisfying Equation (7): Among them, is the speed of HDV n at time t merge ; and is the speed of CAV i+1 at time t merge ; CAV i+1 acceleration a i+1 is determined by Equation (8): a i+1 = min{min(a merge , d comfort ), a norm} (8) where a norm is the conventional acceleration determined by the driving rules, d comfort is the comfort acceleration, a merge is the acceleration required for merging determined according to the motion equation, see Equation (9): wherein, is the time t merge when the position of HDV n is 4. The vehicle collaborative merging control method for highway mixed traffic flow according to claim 1, characterized in that, In the above Step 2, the method for determining the preset speed of the intelligent variable speed indicator to prompt the HDV: The vehicle driving on the main line regards the vehicle in front as the leading vehicle and follows the car-following model until it reaches the merging area; once it enters the merging area, the vehicle driver evaluates whether there is a vehicle merging in front. If there is a merging vehicle, the merging vehicle becomes the new leading vehicle; the main-line vehicle HDV m-1 and the ramp vehicle HDV m have equal speeds, that is, satisfy Equation (10): Among them, is the main-line vehicle HDV m-1 at time t merge,m-1 speed. For the ramp vehicle HDV m At time t merge,m-1 the speed at that time t merge，m-1 Main line vehicle HDV m-1 Time to reach the merging area; To ensure the safety between vehicles, the ramp vehicle HDV m needs to take a time greater than or equal to Δt to reach the merging area, that is, when the ramp vehicle HDV m reaches the merging area, the new lead vehicle has already passed through the merging area and meets the safety distance; Δt is determined by Equation (11): Δt = t merge,m-1 + T min,3 + t f (11) where Δt represents the safe time when the ramp vehicle HDV m does not collide when arriving at the merging area; T min,3 is the minimum headway when the mainline HDV and the ramp HDV merge, and t f is the reaction time required for the driver of the HDV to receive information and make a reaction; If the ramp vehicle HDV m arrives at the merging area at a time greater than or equal to Δt, the ramp vehicle HDV m acceleration is determined by Equation (12): a m = min{min(a merge , d comfort ), a norm}(12) Among them, a m represents the acceleration of the ramp vehicle HDV m to ensure safety between vehicles and avoid collisions when reaching the merging area; a norm is the conventional acceleration determined by the driving rules, d comfort is the comfort acceleration, a merge is the acceleration required for merging determined according to the motion equation, see Equation (13): is the position of the main-line vehicle HDV m-1 at time t merge,m-1 ; is the position of the ramp vehicle HDV m at time t merge,m-1 ; t0 is the time when the vehicle is detected by the detector Since the driver cannot guarantee the acceleration of the vehicle, the speed limit of the HDV is determined according to Equations (12) and (13): where, v limit is the speed limit of the ramp vehicle HDV m , and it is assumed that the HDV travels at the speed and acceleration proposed by the control algorithm; t merge，m is the time when the ramp vehicle HDV m reaches the merging area.

5. An electronic device, characterized in that, Implement vehicle collaborative merging control using the method described in any one of claims 1-4.

6. A computer storage medium, characterized in that, At least one program instruction is stored in the storage medium, and the at least one program instruction is loaded and executed by the processor to implement the vehicle collaborative merging control method described in any one of claims 1-4.

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