A signal-free intersection vehicle speed dynamic planning method based on roadside guidance

Abstract

The application belongs to the technical field of traffic control, and specifically discloses a kind of vehicle speed dynamic planning method of signal intersection based on road side guidance, comprising the following steps: S1 road right distribution problem modeling, S2 state transition equation construction and solution, S3 vehicle speed guidance;With the following points: reduce the scale of state space, reduce the calculation complexity of model solution, improve the solution speed;Consider vehicle dynamics, vehicle following behavior and vehicle obstacle avoidance behavior, while making the vehicle driving behavior consistent with the actual situation, taking into account the safety of road section and intersection two aspects;By solving the time point and combining the speed guidance strategy, conditional automatic driving is realized to a certain extent, the control difficulty is reduced, and the safety of vehicle driving is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of traffic control, in particular to a vehicle speed dynamic planning method based on road side guidance for a signal-free intersection. BACKGROUND

[0002] The mine intersection is different from the urban intersection in terms of lane composition and traffic characteristics. First, in terms of lane composition, the mine road is generally not divided into lanes because it is constantly updated as the mining process progresses. Here, we regard the mine road as an omnidirectional lane, i.e., a vehicle can drive from the lane to any direction allowed to pass. In terms of traffic characteristics, first, the vehicles in the mine area are mainly composed of large mine trucks, which are mainly distinguished by the loading state. Second, because the production plan of the mine area is fixed, the equipment needed is relatively limited, so the traffic flow of the mine intersection is much smaller than that of the urban intersection. Overall, the scale of the road right control problem of the mine intersection is smaller than that of the urban intersection, but the safety and accuracy requirements are much higher than those of the urban intersection.

[0003] The current road right control scheme of the intersection mainly includes road right control in the signal intersection environment and road right control in the signal-free intersection environment. The road right control in the signal intersection environment mainly optimizes the signal parameters such as signal timing, phase sequence, and phase difference to achieve the control of the intersection, and the control object is mainly the traffic facilities such as traffic lights. The signal-free intersection mainly targets the intersection in the network environment, so that the vehicle can pass through the intersection efficiently and orderly by controlling the trajectory and speed of the vehicle. On the one hand, signal control requires corresponding infrastructure construction, such as signal control machines, which is difficult to achieve in the mine area. On the other hand, due to the closed characteristics of the mine area, the control center can realize network automatic driving by obtaining real-time vehicle driving information, including speed, position, and vehicle path, and controlling the vehicle through the vehicle control unit and the road side unit.

[0004] However, there are several deficiencies in controlling the mine intersection by traditional methods, mainly including the following aspects:

[0005] (1) Most traditional signal-free intersection road right control schemes mainly target high-traffic urban intersections. By using methods such as reinforcement learning or game optimization, a near-optimal solution is obtained, which is a good result in a high-traffic urban intersection. However, for a mine intersection with fewer vehicles, the near-optimal solution is difficult to meet the control accuracy.

[0006] (2) The existing methods mainly control the vehicle trajectory dynamically, which requires high communication and vehicle response speed, and the real hardware conditions and safety requirements are difficult to meet. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the present application aims to provide a vehicle speed dynamic planning method for a signal-free intersection based on road-side guidance, which takes into account the characteristics of low traffic flow and high safety requirements at mine intersections, and solves the deficiencies of the original control method in terms of solution accuracy, solution speed and safety performance consideration by comprehensively considering the unique dynamic performance of mine vehicles, following vehicle safety and conflict avoidance and other factors, while combining with appropriate speed guidance strategies to reduce the complexity of vehicle control and increase the feasibility of engineering implementation.

[0008] Therefore, the first aspect of the present application provides a vehicle speed dynamic planning method for a signal-free intersection based on road-side guidance.

[0009] The first aspect of the present application provides a vehicle speed dynamic planning method for a signal-free intersection based on road-side guidance, which comprises the following steps: S1, road right allocation problem modeling: taking the passing time as the objective function and the safety of vehicle driving as the vehicle passing constraint, the vehicle passing constraint includes vehicle dynamics, safe following and conflict avoidance, to obtain a mixed integer programming model; S2, state transition equation construction and solution: the vehicle driving data is sent to the road-side device for correction through the vehicle-mounted device, and the road-side device transmits the corrected vehicle driving data to the control center; the control center constructs the state transition equation for the vehicle with driving direction conflict, and solves the time point when the vehicle enters the intersection according to the mixed integer programming model, sorts the vehicles according to the order of the time points, and issues them to the road-side device; S3, vehicle speed guidance: according to the time point and the current speed of the vehicle, it is judged whether the vehicle arrives at the intersection on time, if yes, the speed is not changed, if no and too early, the road-side device controls the vehicle to uniformly decelerate, and if no and too late, the road-side device controls the vehicle to accelerate.

[0010] The present application provides a vehicle speed dynamic planning method for a signal-free intersection based on road-side guidance, which takes into account the characteristics of low traffic flow and high safety requirements at mine intersections, and proposes a solution method for the optimal passing sequence of the intersection based on dynamic programming, which breaks through the deficiencies of the original control method in terms of solution accuracy, solution speed and safety performance consideration;

[0011] In combination with the actual significance of vehicle motion, the connection between the states of vehicles with no conflict in driving direction is deleted, and only the vehicles with conflict in driving direction are considered, and because the right-turn vehicles have no influence, the right-turn vehicles are excluded from the consideration of the state space, which further reduces the size of the state space and the computational complexity of the model solution, and improves the solution speed;

[0012] The conditional automatic driving is realized by solving the time point and combining the speed guidance strategy, control difficulty is reduced, vehicle driving safety is improved, and operability of engineering implementation is enhanced.

[0013] Specifically, the conflict vehicle represents that trajectories of vehicles in the intersection overlap in space, and the non-conflict vehicle represents that trajectories of vehicles in the intersection do not overlap in space.

[0014] Specifically, the discrimination of the conflict vehicle is according to the order of the passing order, and the vehicle first reaching the intersection is determined as the first passing vehicle between the rear vehicle and the front vehicle, then the discrimination of the second passing vehicle is performed on the remaining arbitrary vehicle reaching the intersection, the discrimination of the conflict relationship with the first vehicle is performed, after the second passing vehicle is determined, the third passing vehicle is determined, and the conflict analysis is performed on the remaining vehicle and the second passing vehicle at this time, and the like is performed.

[0015] In addition, the technical scheme provided by the embodiment of the application can also have the following additional technical features.

[0016] In any of the above technical schemes, the mixed integer programming model is specifically as follows: min T, Wherein, T represents the total passing time, T stage represents the passing time of a certain stage, t assign,i represents the passing time to which the ith vehicle is allocated, M represents an infinite amount, a i,j represents a binary variable, and is 0 when two vehicles are in the same lane, otherwise is 1, Δt,gap represents the minimum headway between two vehicles in the same lane, b i,j represents a binary variable, and is 0 when the driving directions of two vehicles conflict, otherwise is 1, Δt,collision represents the minimum driving time to avoid collision between two vehicles, t min,i represents the time for a vehicle to drive to the intersection at the maximum speed allowed by the environment.

[0017] In the technical scheme, the total target of optimization is to make the total time of vehicles passing through the intersection as short as possible on the basis of ensuring passing safety, so that the passing time is taken as the objective function, and the safety of vehicle driving is taken as the vehicle passing constraint, and the vehicle passing constraint is determined from three dimensions of vehicle dynamics, safe following, and conflict avoidance.

[0018] The first is that the time for a vehicle to enter the intersection needs to meet the vehicle dynamics, and the vehicle cannot drive at a speed exceeding the dynamic performance of the vehicle itself, that is, t assign,i ≥ t min,i .

[0019] Second, the safe following distance between the front and rear vehicles in the same lane needs to be met, that is, the time difference of two vehicles passing through the same place needs to be limited, that is, t assign,i -t assign,j +M·a i,j ≥Δ t,gap ;

[0020] Third, if the time of the vehicles with conflicting directions entering the intersection is not constrained, the two vehicles may collide, that is, t assign,i -t assign,j +M·b i,j ≥Δ t,collision .

[0021] In any of the above technical solutions, the state transition equation is specifically as follows: s = f(s', i) wherein s represents the current state, s' represents the previous state, i represents the decision variable, that is, the approach lane to which the right-of-way is assigned, and f is a state transition function.

[0022] In this technical solution, the right-of-way is taken as a discrete state variable, and the switching between the right-of-waves is the process of state transition. The state variable of the current state is determined by the variable of the previous state. The above relationship is established between the conflicting vehicles because the conflicting vehicles need to avoid each other and have an impact and connection with each other. However, the vehicles in non-conflicting phases often go their own way, so they will not have an impact on each other, that is, the right-of-way between two non-conflicting vehicles will not affect each other, but it violates the Markov property, and dynamic programming cannot be used. Therefore, for non-conflicting vehicles, the state transition equation is re-established, and the previous state is continuously pushed to move until a state that meets the Markov property is searched, and the relationship is re-established to complete the construction of the state space. Finally, the total passing time optimal passing sequence is solved through dynamic programming.

[0023] In any of the above technical solutions, the acceleration control is specifically calculated using the following formula: Wherein t' represents the time of acceleration, t represents the time allocated to enter the intersection, V now represents the current speed of the vehicle, a acc represents the acceleration of the vehicle, V target represents the target speed that needs to be accelerated, and l represents the distance from the entrance of the intersection.

[0024] In this technical solution, through the calculation formula of the acceleration control, the time of acceleration can be calculated according to the current speed of the vehicle, the target speed of acceleration, and the time allocated to enter the intersection, so as to control the speed of the vehicle and ensure that each vehicle can reach and pass through the intersection according to the established sequence.

[0025] In any of the technical solutions above, the deceleration control is specifically calculated according to the following formula:

[0026] In this technical solution, through the calculation formula of the deceleration control, the time for deceleration can be calculated according to the current speed of the vehicle, the target speed of deceleration and the time allocated for entering the intersection, so as to control the speed of the vehicle and ensure that each vehicle can reach and pass through the intersection according to the predetermined sequence.

[0027] In any of the technical solutions above, the planning step specifically includes: vehicle data collection: collecting vehicle driving data through a vehicle-mounted device and transmitting the data to a roadside device, and correcting the position and lane of the vehicle in combination with the roadside device; passage sequence solving: transmitting the corrected vehicle driving data to a control center by the roadside device, constructing a state transition equation and solving the optimal passage sequence of the intersection, and issuing the sequence to the roadside device; and roadside speed guidance: calculating the acceleration or deceleration of the vehicle according to the passage sequence, and issuing the target speed, acceleration and acceleration / deceleration time to the vehicle.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] In combination with the actual significance of vehicle motion, the connection between the vehicle states without conflict in driving direction is deleted, the right-turn vehicles are excluded from the consideration range of the state space according to the non-influence characteristics of the right-turn vehicles, the scale of the state space is further reduced, the calculation complexity of the model solving is reduced, the solving speed is improved, and the model has more practical application significance;

[0030] Considering the vehicle dynamics, the vehicle following behavior and the vehicle obstacle avoidance behavior, the vehicle driving behavior is made to conform to the actual situation, the safety of the road section and the intersection is taken into account, the headway is set on the road section to avoid rear-end accidents, and the time limit is set for the vehicles with conflicting driving directions in the intersection to ensure that the vehicles can be staggered with each other and avoid collision.

[0031] In the environment where the current automatic driving technology and the Internet of Vehicles technology still have communication delay, the control is realized in a relatively simple way, the conditional automatic driving is realized to a certain extent by solving the time point and combining the speed guidance strategy, the control difficulty is reduced, the safety of vehicle driving is improved, and the operability of engineering implementation is enhanced.

[0032] Additional aspects and advantages of embodiments according to the present application will become apparent from the following description with appropriate reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0034] Fig. 1 Structure diagram of the mine low-flow intersection optimal passing behavior control method based on dynamic programming of the application;

[0035] Fig. 2 Flow chart of the roadside guide engineering of the application. DETAILED DESCRIPTION

[0036] In order to more clearly understand the above-mentioned purposes, features and advantages of the application, the application will be further described in detail below in combination with the drawings and specific embodiments. It should be noted that the embodiments of the application and the features in the embodiments can be combined with each other without conflict.

[0037] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the application, however, the application can also be implemented in other manners different from those described herein, therefore, the protection scope of the application is not limited by the specific embodiments disclosed below.

[0038] Referring to Figs. 1-2 The first aspect of the application provides a vehicle speed dynamic programming method based on a signal-free intersection of roadside guide, comprising the following steps:

[0039] Firstly, a right-of-way allocation problem is modeled: the overall goal of optimization is to make the total time of vehicles passing through the intersection as short as possible on the basis of ensuring traffic safety, therefore, the passing time is taken as the objective function, and the safety of vehicle driving is taken as the vehicle passing constraint, which is determined from three dimensions of vehicle dynamics, safe following and conflict avoidance, the time of the first vehicle entering the intersection needs to meet the vehicle dynamics, and the vehicle cannot drive at a speed exceeding its own dynamic performance, the following vehicles in the same lane need to meet the safe following distance, that is, the time difference of two vehicles passing through the same place needs to be limited, and the vehicles in the opposite directions of travel that conflict with each other may collide if their entering times of the intersection are not restricted, and a mixed integer programming model is obtained after sorting;

[0040] Specifically, in the first step, the specific method of modeling the right-of-way allocation problem is as follows:

[0041] Taking the passing time as the optimization goal, the constraints are determined from three dimensions of vehicle dynamics, safe following and conflict avoidance, and the model is as follows:

[0042] minT,T stage =mint assign,i (1)

[0043]

[0044] where T denotes the total travel time, T stage denotes the travel time of a certain phase, t assign,i denotes the travel time to which the ith vehicle is assigned, M denotes an infinite amount, a i,j denotes a binary variable (0 when two vehicles are in the same lane, otherwise 1), Δt,gap denotes the minimum headway between two vehicles in the same lane, b i,j denotes a binary variable (0 when the driving directions of two vehicles conflict, otherwise 1), Δt,collision denotes the minimum driving time to avoid collision between two vehicles, t min,i denotes the time for a vehicle to drive to the intersection at the maximum speed allowed by the environment.

[0045] Second step, state space construction and solution: the right of way is taken as a discrete state variable, and the switching between the right of way is the process of state transition. The right-turn vehicles are excluded from the consideration of the state because they do not need to be additionally issued the right of way. The state variable of the current state is determined by the variable of the previous state. The above relationship is established between the conflict vehicles because the conflict vehicles need to avoid each other and have influence and connection with each other. However, the vehicles in the non-conflict phase often go their own way, so they will not have influence on each other, that is, the right of way between two non-conflict vehicles will not affect each other, but it violates the Markov property, so dynamic programming cannot be used. Therefore, for non-conflict vehicles, the state transition equation is re-constructed, and the state is continuously moved forward until the state meeting the Markov property is searched, and the connection is re-established to complete the construction of the state space. Finally, the total travel time optimal travel sequence is solved by dynamic programming.

[0046] Specifically, in the second step, the specific method of state space construction and solution is as follows:

[0047] The state variable is set as follows:

[0048] s(i|n1 n2 n3···n i ···) (3)

[0049] where i denotes the decision variable, which means that the ith entrance is given the right of way, n i denotes the number of vehicles to which the ith entrance has been given the right of way, and s denotes the state variable.

[0050] The state transition equation is as follows:

[0051] s = f(s', i) (4)

[0052] Wherein, s represents the current state, s' represents its front state, i represents the decision variable (import channel given the right of way), f is the state transition function.

[0053] Because its initial state is determined (s(0|0 0 0···)), it is calculated by the method of dynamic programming forward solution, the specific steps are:

[0054] First, from the initial state, a series of subsequent states are obtained by the state transition equation, each state is a process of issuing a right of way to a vehicle, and the order in which different vehicles obtain the right of way can be known according to the state transition;

[0055] Then, the mixed integer programming model established before is solved, and the optimal time of the two states before and after each state transition process is obtained, that is, the optimal time of the vehicle obtaining the right of way entering the intersection;

[0056] Through the continuous transition and recursion of the state, the order of all vehicles passing through the intersection and the time point of entering the intersection can be obtained, and the total time of all vehicles passing through the intersection can be minimized.

[0057] Third, vehicle speed guidance: the traffic sequence solves the time point of each vehicle entering the intersection, so it is necessary to guide the speed of the vehicle to realize the actual control, and to judge whether the vehicle can arrive at the intersection on time at the current speed, if it enters too early, the vehicle is uniformly decelerated until the target speed is reached, if the vehicle cannot arrive on time, the vehicle is accelerated;

[0058] Specifically, in the third step, the specific method of vehicle speed guidance is:

[0059] The final solution is the optimal time sequence of the vehicle entering the intersection, so that the vehicle can arrive on time through speed guidance, which is divided into acceleration guidance and deceleration guidance according to different conditions, if the vehicle cannot reach the intersection by continuously driving at the current speed, the vehicle needs to be accelerated, otherwise it needs to be decelerated:

[0060] Acceleration guidance:

[0061]

[0062] V target =V now +a acc ·t' (6)

[0063] Wherein, t' represents the time of acceleration, t represents the time of entering the intersection, V now represents the current speed of the vehicle, a acc represents the acceleration of the vehicle, Vtarget Vtarget represents the target speed that needs to be accelerated, l represents the distance from the entrance of the intersection.

[0064] Deceleration guidance:

[0065]

[0066] V target = V now -a dec ·t' (8).

[0067] Fourth step, actual control: control multiple vehicles through the first step, the second step and the third step;

[0068] Specifically, in the fourth step, the specific process of control is:

[0069] First sub-step, vehicle data collection: first, the vehicle-mounted equipment collects the vehicle driving data and transmits it to the roadside equipment, and the roadside equipment corrects the position, lane and other information of the vehicle;

[0070] Second sub-step, passage sequence solving: the roadside equipment transmits the corrected vehicle data to the control center, models the intersection state, solves the optimal passage sequence of the intersection according to the calculation method proposed in the technical scheme, and issues the passage right information to the roadside equipment;

[0071] Third sub-step, roadside speed guidance: according to the passage right information issued by the control center, the speed guidance model is used to calculate whether the vehicle needs to accelerate or decelerate, and the target speed and acceleration / deceleration time are issued to the vehicle to realize the safe and orderly passage of the intersection.

[0072] In the description of the present application, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0073] The above-described embodiments are only preferred modes of the present application and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for dynamic planning of vehicle speed at a signal-free mine intersection based on roadside guidance, characterized by, Comprise the following steps: S1, right-to-use allocation problem modeling: the passing time as the objective function, the safety of vehicle travel as vehicle passing constraints, the vehicle passing constraints include: vehicle dynamics, safe following and conflict avoidance, get mixed integer programming model; S2, state transition equation construction and solution: through the vehicle-mounted device to send vehicle driving data to the roadside device for correction, the roadside device transmits the vehicle driving data corrected to the control center; the control center constructs the state transition equation for the vehicle with driving direction conflict, and solves the time point of the vehicle entering the intersection according to the mixed integer programming model, sorts the vehicles according to the order of the time point, and issues to the roadside device; S3, vehicle speed guidance: according to the time point and the current speed of the vehicle, judge whether the vehicle arrives at the intersection on time, if yes, do not change the speed, if no and too early, the roadside device controls the vehicle with uniform deceleration, if no and too late, the roadside device controls the vehicle with acceleration control; The mixed integer programming model is specifically as follows: where T denotes the total travel time, denotes the travel time of a certain stage, denotes the travel time to which the ith vehicle is assigned, and M denotes an infinite amount, denotes a binary variable and takes the value 0 when the two vehicles are in the same lane, and otherwise takes the value 1, denotes the minimum headway between two vehicles in the same lane, denotes a binary variable and takes the value 0 when the driving directions of the two vehicles conflict, and otherwise takes the value 1, denotes the minimum driving time to avoid a collision between two vehicles, denotes the time for a vehicle to drive to the intersection at the maximum speed allowed by the environment; The state transition equation is specifically as follows: wherein s denotes a current state, denotes its preceding state, i denotes the i-th entry lane to which the right-of-way is currently assigned, and f is a state transition function; The method for solving the time point of the vehicle entering the intersection in S2 is: First, start from the initial state, get a series of subsequent states through the state transition equation, each state is a process of issuing passing right to the vehicle, and the order of different vehicles obtaining passing right can be known according to state transition; Then, solve the mixed integer programming model established before, that is, the optimal time of the two states before and after each state transition process can be obtained, that is, the optimal time of the vehicle obtaining passing right entering the intersection; Through the continuous transition and recursion of the state, the order of all vehicles passing through the intersection and the time point of entering the intersection can be obtained, and the total time of all vehicles passing through the intersection can be the shortest.

2. The method of claim 1, wherein, The acceleration control specifically calculates as follows: wherein, denotes the time duration of the acceleration, t denotes the time assigned to enter the intersection, denotes the current speed of the vehicle, denotes the acceleration of the vehicle, denotes the target speed to which the acceleration is needed, denotes the distance to the entrance of the intersection.

3. The method of claim 1, wherein, The uniform deceleration control specifically calculates as follows: wherein t denotes the time assigned to enter the intersection, denotes the current speed of the vehicle, denotes the distance to the entrance of the intersection.

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