Disclosure of Invention
The invention aims to provide a conflict resolution-based multi-objective optimization method for traffic decision of urban intersections of vehicles. The vehicle crossing interactive relation judgment model is based on a fuzzy logic method, comprehensively considers the crossing desire of two interactive parties and the types of drivers of other vehicles, and the cooperation competition degree between vehicles is subjected to fuzzy reasoning, and a mapping relation between a fuzzy reasoning output value and an interactive relation prediction result is established so as to analyze vehicle-vehicle interactive behaviors under mixed conditions, help unmanned vehicles to understand and judge the behaviors of people in the periphery, and lay a foundation for realizing multi-vehicle cooperative driving.
The invention aims to provide a conflict resolution-based multi-objective optimization method for a traffic decision of an urban intersection of a vehicle, which converts the conflict resolution problem of the intersection into a constrained multi-objective optimization problem (MOP). The model is supported by a virtual simulation experiment, a decision rule for analyzing and extracting mutual avoidance of manned vehicles and unmanned vehicles at the intersection is taken as a research entry point, the maximization of the overall driving benefit of the system is taken as a target, the acceleration is taken as a decision variable, a multi-objective optimization model for conflict resolution of vehicles at the intersection is established, and a solid foundation is provided for a decision system of intelligent driving vehicles.
The invention provides a conflict resolution-based multi-objective optimization method for traffic decision of urban intersections of vehicles, which comprises the following steps:
the vehicle crossing interaction model is characterized in that a fuzzy logic method is applied to establish a vehicle crossing interaction relationship judgment model according to crossing intention of crossing target vehicles and driving types of conflicting vehicles, the degree of cooperation competition between two interactive parties and the types of drivers of other vehicles is considered, and the mapping relationship between a fuzzy reasoning output value and an interaction relationship prediction result is established to represent the cooperation and competition relationship of other vehicles in the interaction process; by analyzing the vehicle-vehicle interaction behavior under the mixed-driving condition, the unmanned vehicle is helped to understand and judge the behavior of the vehicles with people around;
based on the establishment of a decision model for intersection conflict resolution, the vehicle is controlled by taking acceleration as a decision variable, the intersection conflict resolution problem is converted into a multi-objective optimization problem with constraint, the maximization of the overall driving income of the system is taken as a target, the acceleration is taken as the decision variable, the multi-objective optimization model for intersection vehicle conflict resolution is established, and the optimization of the unmanned vehicle action generation result under different interaction modes of the intersection is completed by introducing a variable cooperation coefficient;
and solving the Pareto optimal solution set by adopting an improved non-inferiority genetic algorithm NSGA-II, then carrying out multi-attribute decision analysis on the Pareto optimal solution set by adopting entropy weight TOPSIS, and selecting the optimal solution according to the preference of a decision maker.
Furthermore, the level of the vehicle crossing interactive relation model and the crossing target vehicle crossing willingness is related to the following two factors:
(1) pressure of conflict P
Due to reasons such as traffic regulations, traffic conflicts can be generated at intersections, overlapping areas can be generated on spatial tracks, and traffic accidents are easy to cause; therefore, the vehicles with conflicts need to adjust the time of passing through the overlapping area, so as to realize conflict resolution; as the driver approaches the conflict point, the sensed conflict pressure increases, and the desire to cross the intersection as soon as possible also increases with increasing pressure, increasing the probability of crossing.
(2) Severity of conflict Tc
Whether the target vehicle passes through or not needs to consider the possibility of collision with the collision vehicle, and T is usedcEvaluating the degree of danger of vehicle collision at the intersection; assuming there are conflicting points or planes between traffic participants, the time difference across the conflicting points or planes is Tc;
In the formula LCSV(t) is the distance (m) of the target vehicle CSV from the conflict point; l isCFV(t) is the distance (m) of the collision vehicle CFV from the conflict point; v. ofCSV(t) is the speed (m/s) of the target vehicle CSV; v. ofCFV(t) is the speed of the conflicting vehicle CFV (m/s);
the greater the collision pressure P, the greater the collision severity TcThe smaller, the more likely the driver is to choose to cross over to get better driving conditions; conversely, the smaller the collision pressure P, the greater the degree of collision TcThe larger the more likely the driver is to cross.
Further, the driving style of the conflicting vehicle:
for vehicles passing through the intersection, the willingness of the vehicles to select to accept or reject the crossing request is different for different driver types, and the fuzzy logic construction method of the conflicting vehicle driving types is similar to the construction method of other vehicle driver types in the lane changing.
Still further, mathematical models of multi-objective optimization problems are often represented in the form:
wherein the independent variable X ═ X1,x2,...,xn)TIs n-dimensional Euclidean space EnThe vector of (1); f (X) is the objective function hi(X) 0 and gj(X) ≧ 0 is a constraint.
For solving the maximum value problem of the revenue function, it can be converted into a minimum value problem of the negative function thereof, so that the mathematical description of the optimization problem is:
s.t.amin≤ai≤amax,i=1,2
vmin≤vi≤vmax,i=1,2
in the formula, amin,amaxFor vehicle acceleration limitation, vmin,vmaxIs a vehicle speed limit; p is a cooperative coefficient and takes a value of [ 0-1%]. When the vehicles are in complete competition relationship, p is 0; when the vehicles are in a complete cooperative relationship, p is 1.
For any group (a)1,a2) The speed change scheme of (2) needs to satisfy the following safety constraint conditions:
in the formula
L is the vehicle length and w is the vehicle width.
When the speed of a vehicle to be crossed is adjusted, the calculation formula of the motion state of the vehicle to be crossed is as follows:
in the formula, x
1(t),y
1(t) is the position coordinate at the moment t when the vehicle has speed regulation behavior, (x)
1(0),y
1(0) Is an initial position, v
1(0) At an initial speed, a
1(0) In order to be able to accelerate the vehicle,
is the heading angle.
For another vehicle to be crossed, when the speed is adjusted, the calculation formula of the motion state is as follows:
in the formula, x
2(t),y
2(t) is the position coordinate at the moment t when the vehicle has speed regulation behavior, (x)
2(0),y
2(0) Is an initial position, v
2(0) At an initial speed, a
2(0) In order to be able to accelerate the vehicle,
is the heading angle.
2) Due to the influence of the intersection lanes and the like, the speeds of the vehicles MV and UV cannot exceed the maximum limit speed at any moment, and the allowed minimum speed is zero (i.e., parking), and the speed constraint conditions are as follows:
0<vi(t)≤vmax
wherein v ismaxDepending on the maximum speed limit of the road and the intersection.
3) The acceleration of the vehicle in actual traffic is limited by the vehicle performance, and cannot be too large or too small, then for the acceleration constraint:
amin<ai(t)≤amax
wherein, amin、amaxThe magnitude of (d) depends on vehicle performance and driving comfort requirements;
the improved non-inferiority genetic algorithm (NSGA-II) proposed by Srinivas scholars is adopted, so that the algorithm calculation complexity is reduced; and an elite strategy is adopted to ensure the diversity of the population and improve the convergence and the operation precision of the algorithm.
The invention has the beneficial effects that:
(1) establishing a vehicle lane change interactive relation judgment model and an intersection crossing interactive relation judgment model based on a fuzzy logic method to analyze vehicle-vehicle interactive behaviors under mixed-driving conditions, and helping an unmanned vehicle to understand and judge the behavior of a peripheral vehicle; and several groups of road section and intersection driving data under the mixed running condition in the intelligent automobile competition of China are selected as input parameters of the model, the effectiveness of the vehicle lane changing interactive relationship and intersection crossing interactive relationship judgment model is verified, and the result shows that the accuracy of the fuzzy reasoning method for predicting the cooperative competition degree in the vehicle lane changing and intersection crossing process exceeds 87.3% and 91.6%, the more extreme the vehicle cooperation and competition degree is, the higher the accuracy is, the unmanned vehicle has the capability of understanding human behaviors, and the foundation is laid for realizing multi-vehicle cooperative driving.
(2) According to the characteristic that unmanned driving and manned driving are mixed at the intersection, a multi-objective optimization model for intersection conflict resolution is provided, and when the model is adopted for cooperative driving, the efficiency of conflict vehicles passing through the intersection is effectively improved, so that the running time and the running speed of the conflict vehicles are optimized, and the behavior decision level of the intelligent driving vehicle is improved.
Detailed Description
The invention adopts a fuzzy logic method to establish a vehicle crossing interactive relationship judgment model, the model comprehensively considers the crossing intention of two interactive parties and the types of drivers of other vehicles, the cooperation competition degree between the vehicles is subjected to fuzzy reasoning, and the mapping relationship between the output value of the fuzzy reasoning and the interactive relationship prediction result is established to represent the cooperation and competition relationship of other vehicles in the interactive process. By analyzing the vehicle-vehicle interaction behavior under the mixed-driving condition, the unmanned vehicle is helped to understand and judge the behavior of the people around the unmanned vehicle.
The behavior reaction of the opposite side when the two sides conflict for the 1 st time is taken as a judgment criterion, and the Crossing behavior is divided into Cooperative Crossing (COC) and Competitive Crossing (CMC).
Cooperative ride through behavior: that is, vehicle CSV sends a crossing request, vehicle CFV decelerates to avoid and allows it to cross, and then vehicle CFV completes the crossing.
Competitive crossing behavior: the vehicle CSV issues a cross-over request, which is either held at speed or accelerated to reject, forcing the vehicle CSV to make a compromise until the next gap allows it to cross over again.
According to the interaction relation, in order to complete crossing safely, drivers of two parties have a choice of cooperation and competition, and finally, the drivers give a gift to the crossing result of the other party to safely pass through, and complete competition or compromise between the drivers can cause traffic accidents or reduce traffic efficiency, so that the cooperative driving of vehicles at the crossing can ensure safety and improve traffic efficiency.
First, vehicle crossing interactive relation model
And similarly, a vehicle crossing interactive relation judgment model is established according to the crossing intention of the target vehicle at the intersection and the driving types of the conflicting vehicles, and the cooperation degree between the vehicles is deduced by using a fuzzy logic method.
1. Level of target vehicle crossing will
Whether a vehicle can pass through an intersection is mainly related to the collision pressure and the collision severity sensed by the vehicle, namely the intersection collision pressure P and the collision severity TcAnd as the input quantity of the model, the output variable is the crossing willingness degree. The level of the crossing target vehicle's willingness to cross is generally related to two factors:
(1) pressure of conflict P
Generally, due to traffic regulations and other reasons, traffic conflicts may occur at intersections, for example, straight-going and left-turning vehicles may form a cross conflict, and a coincidence area is generated on a spatial trajectory, which is very likely to cause traffic accidents. Therefore, the vehicles that generate the conflict need to adjust the time for passing through the overlapping area, so as to resolve the conflict. As the driver approaches the conflict point, the sensed conflict pressure increases, and the desire to cross the intersection as soon as possible also increases with increasing pressure, increasing the probability of crossing. To better describe the magnitude of the collision pressure, assuming that a vehicle enters the intersection effective communication range at 150m, the collision pressure is set to 0, the pressure to the collision point is set to 1, and the collision pressure expression is:
p-conflict pressure;
Li(t) — the distance (m) of the ith vehicle from the conflict point.
Constructing a membership function of the conflict pressure, setting the domain scope of the conflict pressure P as {0.1, 0.3, 0.5, 0.7, 0.9}, and setting the fuzzy set as { Very Small (VS), small (S), medium (M), large (L) and Very Large (VL) }.
(2) Severity of conflict Tc
Target vehicleWhether to cross or not needs to consider the possibility of collision with the collision vehicle, and T is usedcThe degree of risk of vehicle collision at the intersection is evaluated. Assuming there are conflicting points or planes between traffic participants, the time difference across the conflicting points or planes is Tc。
In the formula LCSV(t) -distance (m) of the target vehicle CSV from the conflict point; l isCFV(t) is the distance (m) of the collision vehicle CFV from the conflict point; v. ofCSV(t) -speed of target vehicle CSV (m/s); v. ofCFV(t) -speed of conflicting vehicle CFV (m/s).
Combining the measured data with the existing research to determine the conflict severity TcThe domain scope of (c) is set as {0, 3, 5, 7, 10}, and the fuzzy set is { Very Large (VL), large (L), medium (M), small (S), Very Small (VS) }.
(3) Fuzzy control rule
From the above analysis, it can be seen that the greater the collision pressure P, the greater the collision severity TcThe smaller, the more likely the driver is to choose to cross over to get better driving conditions; conversely, the smaller the collision pressure P, the greater the degree of collision TcThe larger the vehicle crossing will be, the less likely the driver will cross, and thus the vehicle crossing will fuzzy rule is determined as shown in table 3.5.
TABLE 3.5 pass-through willingness fuzzy logic rule Table
2. Driving type of conflicting vehicle
For vehicles passing through the intersection, the willingness of the vehicles to select to accept or reject the crossing request is different for different driver types, and the fuzzy logic construction method of the conflicting vehicle driving types is similar to the construction method of other vehicle driver types in the lane changing. Fuzzy rules for determining conflicting vehicle driving types based on expert experience and observation are shown in table 3.6.
TABLE 3.6 fuzzy logic rules Table
3. Fuzzy inference
And (4) taking the traversing intention of the target vehicle and the types of drivers of other vehicles obtained in the two steps as input variables, outputting the input variables as the cooperation degree of the vehicle traversing process, and constructing a vehicle traversing interactive relation judgment model. The vehicle cooperation degree values are expressed by language variables of high (H), medium (M) and low (L), and correspond to 3 results of the interaction relationship among other vehicles, namely cooperation relationship, ambiguity and competitive relationship, respectively, and the vehicle passing through the fuzzy logic rule of the interaction relationship is shown in a table 3.7.
TABLE 3.7 fuzzy logic rule Table for vehicle crossing interaction relationships
Similarly, the fuzzy implication relations of the partial fuzzy reasoning adopt the Mamdani rule, the ambiguity resolution adopts the gravity center method, the corresponding relation between the vehicle cooperation competition degree and the traversing intention and the driving type is obtained by calculation,
and performing defuzzification processing on the fuzzy inference output value, and expressing the output value of the vehicle cooperation degree by using p. And p takes a value between 0 and 1, the lower the quantized value of p is, the more intense the competition among the vehicles is, and conversely, the higher the quantized value of p is, the higher the cooperation degree among the vehicles is. Next, a mapping relationship between the fuzzy inference output value and the interactive relationship prediction result is established, as shown in the following formula, where 3 represents a cooperative relationship, 2 represents an ambiguous state, and 1 represents a competitive relationship. Through the prediction of the vehicle interaction relation, the vehicle-vehicle interaction behavior under the mixed-driving condition is analyzed, and the unmanned vehicle is helped to understand and judge the behavior of the people around the unmanned vehicle.
The vehicle crossing interaction model is characterized in that a vehicle crossing interaction relation judgment model is established according to the crossing intention of target vehicles at the crossing and the driving types of conflicting vehicles, and the cooperation degree between the vehicles is deduced by using a fuzzy logic method.
The method comprises the steps of firstly constructing a vehicle intersection crossing interactive relation judgment model, establishing a decision model for intersection conflict resolution based on the model, controlling vehicles by taking acceleration as a decision variable because relevant states and actions of the vehicles in an intersection passing process are continuous values, converting an intersection conflict resolution problem into a constrained multi-objective optimization problem (MOP), maximizing the whole driving income of a system as a target, establishing the intersection vehicle conflict resolution multi-objective optimization model by taking the acceleration as the decision variable, and finishing optimization of unmanned vehicle action generation results under different interaction modes of the intersection by introducing variable cooperation coefficients. The Pareto optimal solution set is solved by adopting an improved non-inferiority genetic algorithm (NSGA-II), then multi-attribute decision analysis is carried out on the Pareto optimal solution set by adopting an entropy weight TOPSIS, the optimal solution is selected according to the preference of a decision maker, the benefits of safety and comfort are considered, the global optimality of an optimization result is ensured, and experimental verification is carried out on a virtual simulation platform.
The vehicle intersection crossing interactive relation judgment model is established based on crossing intention of crossing target vehicles and driving types of conflicting vehicles, and the cooperation degree between the vehicles is inferred by using a fuzzy logic method.
The multi-objective optimization model defines a model objective function, determines constraint conditions, and finally utilizes an improved non-inferiority genetic algorithm (NSGA-II) to solve, so that the algorithm computation complexity is reduced, population diversity is ensured by adopting an elite strategy, and the algorithm convergence and the operation precision are improved.
Mathematical models of multi-objective optimization problems are often represented in the form:
wherein the independent variable X ═ X1,x2,...,xn)TIs n-dimensional Euclidean space EnThe vector of (1); f (X) is the objective function hi(X) 0 and gj(X) ≧ 0 is a constraint.
For solving the maximum value problem of the revenue function, it can be converted into a minimum value problem of the negative function thereof, so that the mathematical description of the optimization problem is:
s.t.amin≤ai≤amax,i=1,2
vmin≤vi≤vmax,i=1,2
in the formula, amin、amaxFor vehicle acceleration limitation, vmin、vmaxIs a vehicle speed limit; p is a cooperative coefficient and takes a value of [ 0-1%]. When the vehicles are in complete competition relationship, p is 0; when the vehicles are in a complete cooperative relationship, p is 1.
For any group (a)1,a2) The speed change scheme of (2) needs to satisfy the following safety constraint conditions:
in the formula
L is the vehicle length and w is the vehicle width.
When the speed of a vehicle to be crossed is adjusted, the calculation formula of the motion state of the vehicle to be crossed is as follows:
in the formula, x
1(t)y
1(t) when there is a speed-governing action in the vehiclePosition coordinate at time t, (x)
1(0),y
1(0) Is an initial position, v
1(0) At an initial speed, a
1(0) In order to be able to accelerate the vehicle,
is the heading angle.
For another vehicle to be crossed, when the speed is adjusted, the calculation formula of the motion state is as follows:
in the formula, x
2(t),y
2(t) is the position coordinate at the moment t when the vehicle has speed regulation behavior, (x)
2(0),y
2(0) Is an initial position, v
2(0) At an initial speed, a
2(0) In order to be able to accelerate the vehicle,
is the heading angle.
2) Due to the influence of the intersection lanes and the like, the speeds of the vehicles MV and UV cannot exceed the maximum limit speed at any moment, and the allowed minimum speed is zero (i.e., parking), and the speed constraint conditions are as follows:
0<vi(t)≤vmax
wherein v ismaxDepending on the maximum speed limit of the road and the intersection.
3) The acceleration of the vehicle in actual traffic is limited by the vehicle performance, and cannot be too large or too small, then for the acceleration constraint:
amin<ai(t)≤amax
wherein, amin、amaxThe magnitude of (d) depends on vehicle performance and driving comfort requirements;
the improved non-inferiority genetic algorithm (NSGA-II) proposed by Srinivas scholars is adopted, so that the algorithm calculation complexity is reduced; and an elite strategy is adopted to ensure the diversity of the population and improve the convergence and the operation precision of the algorithm.
And (3) simulation experiment verification, namely, a vehicle interaction avoidance decision simulation verification platform under the intersection mixed condition is built by using the Pre Scan software and the Matlab/SimuLink software, the effectiveness of a multi-objective optimization model is verified, a multi-objective optimization conflict resolution algorithm well simulates cooperation and competition modes among vehicles, the robustness of a decision system is improved, and the hybrid driving scene has stronger adaptability.
And the vehicle crossing interactive relation judgment model is verified, effective vehicle motion parameters are obtained by combining video processing of the intelligent automobile competition and GPS data, and intersection driving data under intersection mixed conditions are selected as input parameters of the model and are used for verifying the effectiveness of the intersection vehicle crossing interactive relation judgment model.
Examples
As shown in fig. 1, the driving states of the unmanned vehicle and the manned vehicle are acquired based on the environment sensing module, a vehicle interaction relation determination model is established by using fuzzy reasoning, and the unmanned vehicle decision is made according to the prediction result obtained by the fuzzy reasoning.
As shown in fig. 2, a vehicle crossing interactive relationship determination model is established according to the crossing intention of the target vehicle at the intersection and the driving types of the conflicting vehicles, and the cooperation degree between the vehicles is inferred by using a fuzzy logic method.
As shown in fig. 3, 120 sets of intersection crossing data samples are selected to classify the degree of vehicle cooperation and competition, where 3 is a cooperation relationship indicating the intention of the other vehicle to yield, 2 is an ambiguity indicating an uncertain state of the other vehicle, and 1 is a competition relationship indicating the intention of the other vehicle to not yield. From the figure, it is understood that 38 samples of cooperation relationship, 35 samples of undefined state and 37 samples of competition relationship are correctly identified by the model, and the total number of correct identifications is 110, and the detection accuracy is 91.6%. The accuracy of the fuzzy inference method for predicting the cooperation degree of the vehicle exceeds 90%, which shows that the unmanned vehicle has the capability of understanding human behaviors and lays a foundation for the cooperation of the unmanned vehicle and the manned vehicle.
As shown in FIG. 4, taking a two-lane signalless intersection as an example, an unmanned vehicle may go straight and turn right, straight and left to turn a manned vehicleForming confluence conflict and cross conflict, and the track coincidence area is C in spaceABCDTherefore, traffic accidents are easily caused.
As shown in fig. 5, people and unmanned vehicles having conflicts at the intersection are regarded as a multi-vehicle cooperation system, a conflict vehicle set is obtained through conflict analysis in an internet of vehicles environment, diversity simulation of types of drivers of other vehicles is added, profits of all actions to be selected are calculated, actions corresponding to the maximum profits are output, and cooperation optimization of conflict resolution of people and unmanned vehicles at the intersection is achieved.
As shown in fig. 6, a vehicle interactive avoidance decision simulation verification platform under the intersection mixed-row condition is set up, and the platform relates to four parts of concept design, model design, code generation and system verification in a V cycle.
As shown in fig. 7, for two vehicles having a potential conflict at an intersection, it is first determined whether a conflict exists, and if no conflict exists, a game is not needed, and the vehicle can normally travel. Once the conflict area is entered, the game is started and conflict resolution is achieved through the game.
As shown in fig. 8, the types of drivers are divided into an impulse type (a), a normal type (N), and a conservative type (C), the driving style of the unmanned vehicle is set to 2 types of conservative type and normal conservative type, taking the example that the driving acceleration degree of two vehicles is a conservative-conservative type game, the vehicle MV and UV always perform 4 strategies of acceleration-acceleration, acceleration-deceleration, deceleration-acceleration, and deceleration-deceleration in a game time period, and the variation trend of utility function values of the unmanned vehicle and the manned vehicle is obtained.
As shown in fig. 9, in the whole game process, the unmanned vehicle UV adjusts its behavior strategy according to the behavior of the opposite driver MV, and the behavior decision is greatly different from that in the conflict game process of different types of drivers.
As shown in fig. 10 and 11, the vehicles MV and UV in group a pass through the conflict point at 11s and 14s, respectively, and the vehicles MV and UV in group B pass through the conflict point at 13s and 18s, respectively. Compared with the group B, the group A has shorter average passing time, so that the delay of the intersection is reduced, and the passing efficiency of the intersection is improved.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.