A cooperative traffic control method and system for unsignalized intersections

Abstract

The present invention discloses a traffic control method and system for cooperative signal-free intersections, which relates to the field of intelligent transportation technology. It mainly predicts future states with a key time estimation algorithm as the core and proposes a trajectory smoothing algorithm to induce vehicle speed, which can improve the traffic throughput of parking control intersections and reduce traffic congestion; at the same time, it adopts hierarchical control of vehicle-mounted units and roadside units, which can reduce the complexity of operations and the related risks and responsibilities of traffic operators. And the present invention can be applied to signal-free intersections of structured roads such as urban non-main roads, national and provincial roads, and unstructured roads such as parks, ports, and mines. In addition, the vehicle status information of the intersection is obtained through Internet technology, so as to intelligently decide the driving path and speed of each vehicle, avoid vehicle conflicts and parking waiting, thereby improving the overall efficiency of traffic flow, and providing an effective solution for traffic management of signal-free intersections.

Description

Technical Field

[0001] The present invention relates to the field of intelligent transportation technology, and more particularly to a cooperative traffic control method and system for an unsignalized intersection. Background Art

[0002] At present, Internet technology has been widely used in intersection traffic management applications on structured and unstructured roads. The cooperative traffic control system built by intelligent connected vehicles (CAV) and intelligent roadside units (RSU) maximizes the traffic efficiency and safety of intersections. There are two main types of cooperative intersection traffic control systems: one is a decentralized control system, that is, when an intelligent connected vehicle approaches a conflict area, it will formulate and optimize its trajectory based on the information of other CAVs; the other is a centralized control system, that is, the departure order and trajectory of all CAVs within the intersection are planned at one time. The decentralized control system requires a short communication distance, which can meet the maximum benefit of a single vehicle, but the global optimal benefit is reduced; the centralized control system can achieve the global optimal, but the calculation burden of the control scheme will be greatly increased, and the operation complexity and related risks will increase.

[0003] Therefore, how to intelligently decide the driving path and speed of each vehicle to avoid vehicle conflicts and parking and waiting, thereby improving the overall efficiency of traffic flow is an issue that technical personnel in this field urgently need to solve. Summary of the invention

[0004] In view of this, the present invention provides a cooperative traffic control method and system for signal-free intersections, which can be applied to signal-free intersections of structured roads such as urban non-main roads, national and provincial roads, and unstructured roads such as parks, ports, and mines. The vehicle status information at the intersection is obtained through Internet technology, so as to intelligently decide the driving path and speed of each vehicle, avoid vehicle conflicts and parking waiting, thereby improving the overall efficiency of traffic flow and providing an effective solution for traffic management at signal-free intersections.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A cooperative traffic control method for an unsignalized intersection, comprising:

[0007] S1. Obtain vehicle driving state quantity and roadside state quantity according to the vehicle driving state information collected in real time;

[0008] S2. According to the collected vehicle driving state quantities and roadside state quantities, the intersection area is divided into three parts: the control area, the conflict area and the free area. The vehicles passing through the corresponding control range are divided into four states, namely, arrival, parking, entry and departure;

[0009] S3. If there is no vehicle in the front conflict zone, the on-board unit directly calculates the first critical time point of the vehicle using the critical time estimation algorithm; otherwise, trajectory planning is performed for all conflicting vehicles to determine the second critical time point;

[0010] S4. According to the first key time point and the second key time point, the waiting time of the vehicle at the stop line is estimated, and the set speed value of the vehicle at the next moment is calculated through the trajectory smoothing algorithm, and the set speed value is compared with the preset safety threshold to obtain the optimal control speed of the vehicle at the next moment, thereby smoothing its trajectory.

[0011] Optionally, the vehicle driving state quantity includes speed, acceleration and driving direction; the roadside state quantity includes location information, driving time information and lane speed limit after the vehicle enters the control area.

[0012] Optionally, the specific process of dividing the intersection area into the control area, the conflict area and the free area is:

[0013] Control area: a fixed-length import road section where vehicles in the area reach the optimal control speed by adjusting vehicle speed and acceleration;

[0014] Conflict zone: bounded by the stop line and all boundary lines of the intersection corners, for vehicles behind the stop line to turn and pass;

[0015] Free zone: The exit road section where vehicles are no longer regulated by the roadside unit and resume free driving.

[0016] Optionally, the four states of vehicles in the intersection control area are specifically divided into:

[0017] Arriving vehicles: vehicles that enter the control area of ​​the intersection and cannot reach the stop line at the next moment;

[0018] Parked vehicles: the first vehicle behind the stop line of all entrance lanes waiting to enter the conflict zone;

[0019] Entering vehicles: Vehicles entering the conflict zone;

[0020] Leaving vehicles: Vehicles leaving the conflict zone and entering the free zone.

[0021] Optionally, S2 further includes:

[0022] S21. Define a state set for the vehicle at each moment:

[0023] ;

[0024] In the formula, n is the vehicle ID, tis a moment in time. is the ID set of all vehicles at time t, is the ID set of all DDs at time t, is the ID set of all TCs at time t, is the ID set of all JRs at time t, is the ID set of all SLs at time t; DDs, TCs, JRs, and SLs represent the sets corresponding to arriving vehicles, parking vehicles, entering vehicles, and leaving vehicles, respectively. DD is an arriving vehicle, TC is a parking vehicle, JR is an entering vehicle, and SL is a leaving vehicle.

[0025] S22. The length of the control area is related to the initial speed of the vehicle. It should satisfy the requirement that there is enough time and space for speed adjustment when entering the control area at any initial speed, so as to obtain the shortest length of the control area. Therefore, the range constraint of the control area is:

[0026] ;

[0027] In the formula, L is the length of the regulatory region, is the maximum speed limit for vehicles within the intersection control area. is the acceleration of vehicle n when the speed is adjusted, where n is the vehicle ID within the intersection control range;

[0028] S23. Determine the earliest stopping time when DD reaches the stop line according to the length of the control area:

[0029] Calculate the distance required for DD to accelerate to the maximum speed limit at maximum acceleration and then decelerate to zero at maximum deceleration:

[0030] ;

[0031] In the formula, The distance required for DD to accelerate to the maximum speed limit at the maximum acceleration and then decelerate to zero at the maximum deceleration. For the current lane The maximum speed limit, is the speed of vehicle n at time t, is the maximum comfortable acceleration of vehicle n, is the maximum comfortable deceleration of vehicle n;

[0032] Calculate the acceleration, deceleration and cruising time of DD:

[0033] ;

[0034] In the formula, is the estimated acceleration time of vehicle n at time t, is the estimated deceleration time of vehicle n at time t, is the estimated cruising time of vehicle n at time t;

[0035] Estimate the earliest stopping time of DD to reach the stop line:

[0036] ;

[0037] In the formula, is the earliest estimated parking time of vehicle n at the stop line at time t. The estimated parking time of DD must be greater than or equal to the earliest estimated parking time. EST .

[0038] Optionally, the S3 is specifically:

[0039] S31: There is no vehicle in the conflict zone ahead. The onboard unit calculates the first critical time point of the vehicle through the critical time estimation algorithm, including the parking time of the arriving vehicle reaching the stop line, the time when the parked vehicle enters the conflict zone, and the time when the entering vehicle leaves the conflict zone. The vehicle directly executes according to the corresponding first critical time point;

[0040] S32: There is a vehicle in the conflict zone ahead. The roadside unit plans the vehicle trajectories in all the conflict zones, calculates the second critical time point of the vehicle, and the vehicle executes according to the corresponding second critical time point.

[0041] Optionally, the key time estimation algorithm is specifically:

[0042] The on-board unit receives the motion status information of all DDs, TCs and JRs in the communication area in real time. Then, an integer position index in the departure sequence is assigned to each TC according to the actual parking time sequence. The position index of the TC is updated by estimating the time when other TCs enter the conflict area and the time when JRs leave the conflict area, subtracting the number of JR vehicles that leave the conflict area and join the SL set at the current time from the previous time. Finally, the TC is granted the right to enter the conflict area according to its estimated entry time.

[0043] If the position index is 0 at the current time t, it will start to enter the conflict area. Otherwise, it can only enter after all the TCs in the conflicting direction have left the conflict area. If there is no conflict with the previous TC in the departure sequence, TC n has the opportunity to enter the conflict area at the same time as the previous TC, and it must not enter the conflict area earlier than its previous TC to meet the first-come-first-out rule.

[0044] The time it takes a vehicle to leave the conflict zone is estimated by calculating the time it takes to pass through the conflict zone and reach the free zone plus its estimated entry time;

[0045] If the estimated time of TC n to enter the conflict zone is equal to the current time t, it is granted the permission to enter the intersection conflict zone;

[0046] Estimate the stopping time of the DD when it reaches the stop line based on the status information of other DDs ahead and all existing TCs and JRs on the same lane;

[0047] If DD n is the first vehicle on the lane and there is no stop line and no TC behind it, DD n will arrive at the stop line first and stop. If there is a TC, DD n can only arrive at the stop line and stop after TC m enters the conflict zone. If there are other DDs in front of DD n in the lane, it can only wait for the DD in front to arrive. Enter the conflict zone to reach the stop line to stop; TC n represents the parked vehicle with vehicle ID n; DD n represents the arriving vehicle with vehicle ID n; TC m represents the parked vehicle with vehicle ID m; DD Indicates that the vehicle ID is Arrival vehicles;

[0048] Then, the time of entering the conflict zone is estimated based on the estimated parking time;

[0049] Finally, it is necessary to calculate the time it takes to pass through the conflict zone and reach the free zone plus its estimated entry time to estimate the time it takes to leave the conflict zone.

[0050] Optionally, S4 is specifically:

[0051] S41, JRs accelerate to the maximum speed limit with the maximum comfortable acceleration in order to leave the conflict zone as soon as possible. At time t, JRs will determine its speed at the next moment according to the following formula:

[0052] ;

[0053] In the formula, is the speed of vehicle n at time t+1, is the maximum speed limit of the target road section, is the maximum comfortable acceleration of vehicle n, is the time step, is the speed of vehicle n at time t, For the collection of all moments;

[0054] To ensure safety, SLs uses the Krauß vehicle dynamics model, and the speed at the next moment Recommended by Krauß vehicle dynamics model;

[0055] S42, construct a segmented trajectory for DDs, which is divided into three sections: acceleration, constant speed and deceleration. Acceleration and deceleration are performed to control the vehicle speed with comfortable acceleration or deceleration to smooth the vehicle trajectory. Considering safety, the set value and the safety threshold are compared as the speed of the vehicle at the next moment, which is determined by the following formula:

[0056] ;

[0057] In the formula, is the speed of vehicle n at the next moment t+1, The speed recommended by the trajectory smoothing algorithm, The cruising speed recommended for the Krauß vehicle dynamics model, For the current lane Maximum speed limit;

[0058] Optionally, the estimated stopping time for DD to reach the stop line after one deceleration is divided into two cases, namely:

[0059] ;

[0060] In the formula, The stopping time of vehicle n arriving at time t after decelerating once to reach the stop line; is the distance from vehicle n to the lane stop line at time t, is the speed of vehicle n at time t;

[0061] A cooperative traffic control system for an unsignalized intersection, comprising:

[0062] The vehicle-mounted unit shares the collected vehicle driving status information with other vehicle-mounted units and roadside units in real time and receives feedback information from other vehicle-mounted units and roadside units to obtain vehicle driving status and roadside status;

[0063] The regional state division unit divides the intersection area into three parts: the control area, the conflict area and the free area, and divides the vehicles passing through the corresponding control range into four states: arrival, parking, entry and departure;

[0064] The key time point determination unit, if there is no vehicle in the conflict zone ahead, directly calculates the first key time point by using the key time estimation algorithm, including the time when the vehicle reaches the stop line, and the time when it enters and leaves the conflict zone; otherwise, trajectory planning is performed for all conflicting vehicles to determine the second key time point;

[0065] The trajectory smoothing unit estimates the waiting time of the vehicle at the stop line according to the first key time point and the second key time point, calculates the set speed value of the vehicle at the next moment through the trajectory smoothing algorithm, compares the set speed value with the preset safety threshold, and obtains the optimal control speed of the vehicle at the next moment, thereby smoothing its trajectory.

[0066] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a cooperative traffic control method and system for unsignalized intersections, which uses a critical time estimation algorithm as the core to predict future states and proposes a trajectory smoothing algorithm to induce vehicle speed, thereby improving traffic throughput at parking control intersections and reducing traffic congestion; at the same time, hierarchical control of on-board units and roadside units is adopted, which can reduce the complexity of operations and the related risks and responsibilities of traffic operators. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0068] Figure 1 A flow chart of the method provided by the present invention;

[0069] Figure 2 A hierarchical control framework diagram provided by the present invention;

[0070] Figure 3 A schematic diagram of a parking control intersection area provided by the present invention;

[0071] Figure 4 This is a schematic diagram of vehicle state conversion provided by the present invention. DETAILED DESCRIPTION

[0072] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0073] The embodiment of the present invention discloses a cooperative traffic control method for an unsignalized intersection, such as Figure 1 As shown, including:

[0074] S1, according to the vehicle-mounted unit, the vehicle driving state information collected is shared with other vehicle-mounted units and roadside units in real time and feedback information is received from other vehicle-mounted units and roadside units to obtain the vehicle driving state quantity and the roadside state quantity;

[0075] S2. According to the collected vehicle driving state quantities and roadside state quantities, the intersection area is divided into three parts: control area, conflict area and free area, and the vehicles passing through the corresponding control range are divided into four states, namely arrival, parking, entry and departure;

[0076] S3. If there is no vehicle in the conflict zone ahead, the onboard unit directly calculates the first key time point using the key time estimation algorithm, including the time when the vehicle stops at the stop line, and the time when it enters and leaves the conflict zone; otherwise, the roadside unit plans the trajectories of all conflicting vehicles, determines the second key time point, and feeds it back to the onboard unit;

[0077] S4. The on-board unit estimates the waiting time of the vehicle at the stop line according to the first key time point and the second key time point, and calculates the set speed value of the vehicle at the next moment through the trajectory smoothing algorithm, and compares the set speed value with the preset safety threshold to obtain the optimal control speed of the vehicle at the next moment, thereby smoothing its trajectory.

[0078] In a specific embodiment, the vehicle driving state includes speed, acceleration and driving direction; the roadside state includes the location information, driving time information and lane speed limit of the vehicle after entering the control area.

[0079] In a specific embodiment, the parking control intersection area and vehicle state transition diagram is as follows: Figure 3 and Figure 4 As shown in Figure 1, the specific process of dividing the intersection area into the control area, conflict area and free area is as follows:

[0080] Control area: a fixed-length import road section where vehicles in the area reach the optimal control speed by adjusting vehicle speed and acceleration;

[0081] Conflict zone: bounded by the stop line and all boundary lines of the intersection corners, for vehicles behind the stop line to turn and pass;

[0082] Free zone: The exit road section where vehicles are no longer regulated by the roadside unit and resume free driving.

[0083] In a specific embodiment, the four states of vehicles in the intersection control area are specifically divided into:

[0084] DD (arriving vehicle): a vehicle that enters the control area of ​​the intersection and cannot reach the stop line at the next moment;

[0085] TC (stopped vehicle): the first vehicle behind the stop line of all entrance lanes waiting to enter the conflict zone;

[0086] JR (entry vehicle): vehicle entering the conflict zone;

[0087] SL (Leaving Vehicle): Vehicles leaving the conflict zone and entering the free zone.

[0088] In a specific embodiment, S2 further includes:

[0089] S21. Define a state set for the vehicle at each moment:

[0090] ;

[0091] In the formula, n is the vehicle ID, t is a moment in time. is the ID set of all vehicles at time t, is the ID set of all DDs at time t, is the ID set of all TCs at time t, is the ID set of all JRs at time t, is the ID set of all SLs at time t; DDs, TCs, JRs, and SLs represent the sets corresponding to arriving vehicles, parking vehicles, entering vehicles, and leaving vehicles, respectively. DD is an arriving vehicle, TC is a parking vehicle, JR is an entering vehicle, and SL is a leaving vehicle.

[0092] S22. The length of the control area is related to the initial speed of the vehicle. It should satisfy the requirement that there is enough time and space for speed adjustment when entering the control area at any initial speed, so as to obtain the shortest length of the control area. Therefore, the range constraint of the control area is:

[0093] ;

[0094] In the formula, L is the length of the regulatory region, is the maximum speed limit for vehicles within the intersection control area. is the acceleration of vehicle n when the speed is adjusted, where n is the vehicle ID within the intersection control range;

[0095] S23. Determine the earliest stopping time when DD reaches the stop line according to the length of the control area:

[0096] Calculate the distance required for DD to accelerate to the maximum speed limit at maximum acceleration and then decelerate to zero at maximum deceleration:

[0097] ;

[0098] In the formula, The distance required for DD to accelerate to the maximum speed limit at the maximum acceleration and then decelerate to zero at the maximum deceleration. For the current lane The maximum speed limit, is the speed of vehicle n at time t, is the maximum comfortable acceleration of vehicle n, is the maximum comfortable deceleration of vehicle n;

[0099] Calculate the acceleration, deceleration and cruising time of DD:

[0100] ;

[0101] In the formula, is the estimated acceleration time of vehicle n at time t, is the estimated deceleration time of vehicle n at time t, is the estimated cruising time of vehicle n at time t;

[0102] Estimate the earliest stopping time of DD to reach the stop line:

[0103] ;

[0104] In the formula, is the earliest estimated parking time of vehicle n at the stop line at time t. The estimated parking time of DD must be greater than or equal to the earliest estimated parking time. EST .

[0105] In a specific embodiment, the hierarchical control framework diagram is as follows: Figure 2 As shown, S3 is specifically:

[0106] S31: There is no vehicle in the conflict zone ahead. The onboard unit calculates the first critical time point of the vehicle through the critical time estimation algorithm, i.e., the stopping time of DDs reaching the stop line, the time of TCs entering the conflict zone, and the time of JRs leaving the conflict zone. The vehicle directly executes according to the corresponding first critical time point.

[0107] S32: There is a vehicle in the conflict zone ahead. The roadside unit plans the vehicle trajectories in all the conflict zones, calculates the second critical time point of the vehicle, and the vehicle executes according to the corresponding second critical time point.

[0108] In a specific embodiment, the critical time estimation algorithm is specifically:

[0109] The on-board unit receives the motion status information of all DDs, TCs and JRs in the communication area in real time. Then, an integer position index in the departure sequence is assigned to each TC according to the actual parking time sequence. The position index of the TC is updated by estimating the time when other TCs enter the conflict area and the time when JRs leave the conflict area, subtracting the number of JR vehicles that leave the conflict area and join the SL set at the current time from the previous time. Finally, the TC is granted the right to enter the conflict area according to its estimated entry time, as shown in the following formula:

[0110] ;

[0111] In the formula, for t Time Vehicle n Estimated time of entry into the conflict zone, is the ID of the previous TC of TC n in the departure sequence, For vehicles m exist t -1 moment estimated time to leave the conflict zone, , is the position index of the vehicle at time t, and are the actual parking time of vehicles m and n at the stop line at time t, , and are vehicles m, n, The priority of the moving direction;

[0112] If the position index is 0 at the current time t, it will start to enter the conflict zone. Otherwise, it can only enter after all the TCs in the conflicting direction have left the conflict zone. If there is no conflict with the previous TC in the departure sequence, TC n has the opportunity to enter the conflict zone at the same time as the previous TC, and it must not enter the conflict zone earlier than its previous TC to meet the first-come-first-out rule. In addition, it is necessary to estimate the time it takes to leave the conflict zone by calculating the time it takes to reach the free zone through the conflict zone plus its estimated entry time:

[0113] ;

[0114] ;

[0115] In the formula, is the estimated time for vehicle n to leave the intersection conflict zone at time t, is the gap time for vehicles to pass through the intersection conflict zone, is the maximum comfortable acceleration, k is the lane ID, is the maximum speed limit of lane k, is the length of the k lane, For all lane ID sets.

[0116] If the estimated time of TC n to enter the conflict zone is equal to the current time t, it is granted permission to enter the intersection conflict zone:

[0117] ;

[0118] In the formula, is a binary variable for whether vehicle n can enter the intersection conflict zone, TC Once the access right to the intersection conflict zone is obtained, the JR set will be added to the intersection conflict zone at the next time t+1.

[0119] Estimate the stopping time of the DD at the stop line based on the status information of other DDs ahead and all existing TCs and JRs on the same lane:

[0120] ;

[0121] In the formula, is the estimated parking time of DD n to reach the stop line at time t, is the front DDs in the same lane of DD n at time t, is the ID of the DD in front of DD n. If DD n is the first vehicle in the lane and there is no TC behind the stop line, DD n can arrive at the stop line first and stop. If there is a TC, DD n can arrive at the stop line and stop only after TC m enters the conflict zone. If there are other DDs in front of the lane where DD n is located, it can only wait for the DD in front. Enter the conflict zone to reach the stop line and stop. Among them, TC n represents the parked vehicle with vehicle ID n; DD n represents the arriving vehicle with vehicle ID n; TC m represents the parked vehicle with vehicle ID m; DD Indicates that the vehicle ID is Arrival vehicles;

[0122] Then, estimate the time it will take to enter the conflict zone based on the estimated parking time:

[0123] ;

[0124] In the formula, is the estimated time for DD n to enter the conflict zone at time t. Finally, it is necessary to calculate the time it takes to pass through the conflict zone and reach the free zone plus its estimated entry time to estimate the time it takes to leave the conflict zone, as shown in the following formula:

[0125] ;

[0126] In a specific embodiment, S4 is specifically:

[0127] S41, JRs accelerate to the maximum speed limit with the maximum comfortable acceleration in order to leave the conflict zone as soon as possible. At time t, JRs will determine its speed at the next moment according to the following formula:

[0128] ;

[0129] In the formula, is the speed of vehicle n at time t+1, is the maximum speed limit of the target road section, is the maximum comfortable acceleration of vehicle n, is the time step, is the speed of vehicle n at time t, For the collection of all moments;

[0130] To ensure safety, SLs uses the Krauß vehicle dynamics model, and the speed at the next moment Recommended by Krauß vehicle dynamics model;

[0131] S42, construct a segmented trajectory for DDs, which is divided into three sections: acceleration, constant speed and deceleration. Acceleration and deceleration are performed to control the vehicle speed with comfortable acceleration or deceleration to smooth the vehicle trajectory. Considering safety, the set value and the safety threshold are compared as the speed of the vehicle at the next moment, which is determined by the following formula:

[0132] ;

[0133] In the formula, is the speed of vehicle n at the next moment t+1, The speed recommended by the trajectory smoothing algorithm, The cruising speed recommended for the Krauß vehicle dynamics model, For the current lane Maximum speed limit;

[0134] In a specific embodiment, the estimated stopping time of the DD reaching the stop line after one deceleration is divided into two cases, namely:

[0135] ;

[0136] In the formula, The stopping time of vehicle n arriving at time t after decelerating once to reach the stop line; is the distance from vehicle n to the lane stop line at time t, is the speed of vehicle n at time t;

[0137] Scenario 1 : DD n has at least one cruise or acceleration segment before deceleration, and its smooth trajectory is found by the following set of equations:

[0138]

[0139] ;

[0140] In the formula, For comfortable acceleration, For comfortable deceleration, For the acceleration time interval, is the cruising time interval, is the deceleration time interval, is the vehicle speed at the acceleration / deceleration transition point, The first two equations specify the speed and position of the vehicle at the end of the acceleration phase. The third and fourth equations represent the speed and position of the vehicle at the end of the deceleration phase (i.e., the parking situation at the stop line). The fifth equation ensures that the vehicle stops at the stop line at the expected stopping time. The last equation assumes that the ratio of acceleration and deceleration is always the same as the ratio of maximum comfortable acceleration and deceleration. In order to ensure the uniqueness of the solution, the vehicle is first assumed to not require a cruise phase (i.e., ), use the following formula to calculate the speed at the acceleration / deceleration stage transition point :

[0141] ;

[0142] In the formula, ;

[0143] when The trajectory obtained when is feasible; when When the vehicle is in a state of acceleration and deceleration, a cruising section with a maximum speed is required to ensure that the vehicle speed does not exceed the speed limit. Therefore, the present invention relaxes the assumption that there is no cruising section and sets the speed at the transition point of the acceleration and deceleration section to the maximum speed limit, that is, , the following formula calculates the trajectory variables for these two cases:

[0144] ;

[0145] Based on the planned trajectory of case 1, the speed of the vehicle at the next time point is calculated as follows:

[0146] ;

[0147] In the formula, is the speed recommended by the trajectory smoothing algorithm;

[0148] Scenario 2 ( ): DD n first decelerates sharply until it can decelerate smoothly at the next moment and catch up with the estimated parking time. To this end, the approximate setting is estimated at the next moment. Required deceleration:

[0149] ;

[0150] In this example, DD n sets its deceleration to ,if , then set ,Right now:

[0151] ;

[0152] Finally, in order to avoid a collision, a suggested speed is given from the set Krauss vehicle dynamics model, using The vehicle then compares these two speeds with the maximum speed limit and chooses the lower speed to ensure safety, i.e.:

[0153] .

[0154] A cooperative traffic control system for an unsignalized intersection, comprising:

[0155] The vehicle-mounted unit shares the collected vehicle driving status information with other vehicle-mounted units and roadside units in real time and receives feedback information from other vehicle-mounted units and roadside units to obtain vehicle driving status and roadside status;

[0156] The regional state division unit divides the intersection area into three parts: the control area, the conflict area and the free area, and divides the vehicles passing through the corresponding control range into four states: arrival, parking, entry and departure;

[0157] The key time point determination unit, if there is no vehicle in the conflict zone ahead, directly calculates the first key time point by using the key time estimation algorithm, including the time when the vehicle reaches the stop line, and the time when it enters and leaves the conflict zone; otherwise, trajectory planning is performed for all conflicting vehicles to determine the second key time point;

[0158] The trajectory smoothing unit estimates the waiting time of the vehicle at the stop line according to the first key time point and the second key time point, calculates the set speed value of the vehicle at the next moment through the trajectory smoothing algorithm, compares the set speed value with the preset safety threshold, and obtains the optimal control speed of the vehicle at the next moment, thereby smoothing its trajectory.

[0159] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0160] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A cooperative traffic control method for an unsignalized intersection, characterized in that: include: S1. Obtain vehicle driving state quantity and roadside state quantity according to the vehicle driving state information collected in real time; S2. According to the collected vehicle driving state quantities and roadside state quantities, the intersection area is divided into three parts: control area, conflict area and free area, and the vehicles passing through the corresponding control range are divided into four states, namely arrival, parking, entry and departure; S3. If there is no vehicle in the front conflict zone, the on-board unit directly calculates the first critical time point of the vehicle using the critical time estimation algorithm; otherwise, trajectory planning is performed for all conflicting vehicles to determine the second critical time point; S4. According to the first key time point and the second key time point, the waiting time of the vehicle at the stop line is estimated, and the set speed value of the vehicle at the next moment is calculated by a trajectory smoothing algorithm, and the set speed value is compared with a preset safety threshold to obtain the optimal control speed of the vehicle at the next moment, thereby smoothing its trajectory; The S2 further includes: S21. Define a state set for the vehicle at each moment: Where n is the vehicle ID, t is a certain moment in the time period, is the ID set of all vehicles at time t, D t is the ID set of all DDs at time t, T t is the ID set of all TCs at time t, J t is the ID set of all JRs at time t, S t is the ID set of all SLs at time t; DDs, TCs, JRs, and SLs represent the set of arriving vehicles, parking vehicles, entering vehicles, and leaving vehicles, respectively. DD is an arriving vehicle, TC is a parking vehicle, JR is an entering vehicle, and SL is a leaving vehicle. S22. The length of the control area is related to the initial speed of the vehicle. It should satisfy the requirement that there is enough time and space for speed adjustment when entering the control area at any initial speed, so as to obtain the shortest length of the control area. Therefore, the range constraint of the control area is: Where L is the length of the regulatory region, v max is the maximum speed limit of vehicles in the intersection control area, a n is the acceleration of vehicle n when the speed is adjusted, where n is the vehicle ID within the intersection control range; S23. Determine the earliest stopping time when DD reaches the stop line according to the length of the control area: Calculate the distance required for DD to accelerate to the maximum speed limit at maximum acceleration and then decelerate to zero at maximum deceleration: In the formula, Δx′ nt The distance required for DD to accelerate to the maximum speed limit at the maximum acceleration and then decelerate to zero at the maximum deceleration. For the current lane The maximum speed limit, v nt is the speed of vehicle n at time t, is the maximum comfortable acceleration of vehicle n, a n is the maximum comfortable deceleration of vehicle n; Calculate the acceleration, deceleration and cruising time of DD: In the formula, is the estimated acceleration time of vehicle n at time t, is the estimated deceleration time of vehicle n at time t, is the estimated cruising time of vehicle n at time t; Estimate the earliest stopping time of DD to reach the stop line: In the formula, EST nt is the earliest estimated parking time of vehicle n at the stop line at time t. The estimated parking time of DD must be greater than or equal to the estimated earliest parking time EST; The key time estimation algorithm is as follows: The on-board unit receives the motion status information of all DDs, TCs and JRs in the communication area in real time. Then, an integer position index in the departure sequence is assigned to each TC according to the actual parking time sequence. The position index of the TC is updated by estimating the time when other TCs enter the conflict area and the time when JRs leave the conflict area, subtracting the number of JR vehicles that leave the conflict area and join the SL set at the current time from the previous time. Finally, the TC is granted the right to enter the conflict area according to its estimated entry time. If the position index is 0 at the current time t, it will start to enter the conflict area. Otherwise, it can only enter after all the TCs in the conflicting direction have left the conflict area. If there is no conflict with the previous TC in the departure sequence, TCn has the opportunity to enter the conflict area at the same time as the previous TC, and it must not enter the conflict area earlier than its previous TC to meet the first-come-first-out rule. The time it takes a vehicle to leave the conflict zone is estimated by calculating the time it takes to pass through the conflict zone and reach the free zone plus its estimated entry time; If the estimated time of TCn to enter the conflict zone is equal to the current time t, it is granted the permission to enter the intersection conflict zone; Estimate the stopping time of the DD when it reaches the stop line based on the status information of other DDs ahead and all existing TCs and JRs on the same lane; If DDn is the first vehicle on the lane and there is no stop line and no TC behind it, DDn will arrive at the stop line first and stop. If there is a TC, DDn can only arrive at the stop line and stop after TCm enters the conflict zone. If there are other DDs in front of DDn in the lane, DDn can only arrive at the stop line and stop after TCm enters the conflict zone. Enter the conflict zone to reach the stop line to stop; TCn represents the parked vehicle with vehicle ID n; DDn represents the arriving vehicle with vehicle ID n; TCm represents the parked vehicle with vehicle ID m; DD Indicates that the vehicle ID is Arrival vehicles; Then, the time of entering the conflict zone is estimated based on the estimated parking time; Finally, it is necessary to calculate the time it takes to pass through the conflict zone and reach the free zone plus its estimated entry time to estimate the time it takes to leave the conflict zone.

2. A cooperative traffic control method for an unsignalized intersection according to claim 1, characterized in that: The vehicle driving state includes speed, acceleration and driving direction; the roadside state includes the location information, driving time information and lane speed limit of the vehicle after entering the control area.

3. A cooperative traffic control method for an unsignalized intersection according to claim 1, characterized in that: The specific process of dividing the intersection area into the control area, the conflict area and the free area is as follows: Control area: a fixed-length import road section where vehicles in the area reach the optimal control speed by adjusting vehicle speed and acceleration; Conflict zone: bounded by the stop line and all boundary lines of the intersection corners, for vehicles behind the stop line to turn and pass; Free zone: The exit road section where vehicles are no longer regulated by the roadside unit and resume free driving.

4. A cooperative traffic control method for an unsignalized intersection according to claim 1, characterized in that: The four states of vehicles in the intersection control area are divided into: Arriving vehicles: vehicles that enter the control area of ​​the intersection and cannot reach the stop line at the next moment; Parked vehicles: the first vehicle behind the stop line of all entrance lanes waiting to enter the conflict zone; Entering vehicles: Vehicles entering the conflict zone; Leaving vehicles: Vehicles leaving the conflict zone and entering the free zone.

5. A cooperative traffic control method for an unsignalized intersection according to claim 1, characterized in that: The S3 is specifically: S31: There is no vehicle in the conflict zone ahead. The onboard unit calculates the first critical time point of the vehicle through the critical time estimation algorithm, including the parking time of the arriving vehicle reaching the stop line, the time when the parked vehicle enters the conflict zone, and the time when the entering vehicle leaves the conflict zone. The vehicle directly executes according to the corresponding first critical time point; S32: There is a vehicle in the conflict zone ahead. The roadside unit plans the vehicle trajectories in all the conflict zones, calculates the second critical time point of the vehicle, and the vehicle executes according to the corresponding second critical time point.

6. A cooperative traffic control method for an unsignalized intersection according to claim 1, characterized in that: S4 is specifically: S41, JRs accelerate to the maximum speed limit with the maximum comfortable acceleration in order to leave the conflict zone as soon as possible. At time t, JRs will determine its speed at the next moment according to the following formula: In the formula, v n(t+1) is the speed of vehicle n at time t+1, is the maximum speed limit of the target road section, is the maximum comfortable acceleration of vehicle n, δ is the time step, v nt is the speed of vehicle n at time t, is the set of all moments, J t is the ID set of all JRs at time t; To ensure safety, SLs adopts the Krauβ vehicle dynamics model, and the speed at the next moment Recommended by the Krauβ vehicle dynamics model; S42, construct a segmented trajectory for DDs, which is divided into three sections: acceleration, constant speed and deceleration. Acceleration and deceleration are performed to control the vehicle speed with comfortable acceleration or deceleration to smooth the vehicle trajectory. Considering safety, the set value and the safety threshold are compared as the speed of the vehicle at the next moment, which is determined by the following formula: In the formula, v n(t+1) is the speed of vehicle n at the next moment t+1, The speed recommended by the trajectory smoothing algorithm, The cruising speed recommended for the Krauβ vehicle dynamics model, is the current lane i n The maximum speed limit.

7. A cooperative traffic control method for an unsignalized intersection according to claim 1, characterized in that: According to the estimated stopping time of the arriving vehicle to reach the stop line after one deceleration, it is divided into two cases: and In the formula, The stopping time of vehicle n arriving at time t after decelerating once to reach the stop line; is the distance from vehicle n to the lane stop line at time t, v nt is the speed of vehicle n at time t; ST nt The parking time for the arriving vehicle to reach the stop line.

8. A cooperative traffic control system for unsignalized intersections, characterized in that: A method for cooperative traffic control at an unsignalized intersection according to any one of claims 1 to 7 is applied, comprising: The vehicle-mounted unit shares the collected vehicle driving status information with other vehicle-mounted units and roadside units in real time and receives feedback information from other vehicle-mounted units and roadside units to obtain vehicle driving status and roadside status; The regional state division unit divides the intersection area into three parts: the control area, the conflict area and the free area, and divides the vehicles passing through the corresponding control range into four states: arrival, parking, entry and departure; The critical time point determination unit, if there is no vehicle in the conflict zone ahead, directly uses the critical time estimation algorithm to calculate the vehicle's stopping time at the stop line, the time to enter and leave the conflict zone; otherwise, trajectory planning is performed for all conflicting vehicles to determine the critical time points; The trajectory smoothing unit estimates the waiting time of the vehicle at the stop line according to the key time points, and calculates the set speed value of the vehicle at the next moment through the trajectory smoothing algorithm. The set speed value is compared with the preset safety threshold to obtain the optimal control speed of the vehicle at the next moment, thereby smoothing its trajectory.

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