Ramp confluence area vehicle confluence trajectory planning method considering multi-objective optimization in pure network connection environment

Abstract

The invention discloses a ramp confluence area vehicle confluence trajectory planning method considering multi-objective optimization in a pure network connection environment, and the method comprises the steps: if a main line has a safety gap and a ramp vehicle can safely confluence into the safety gap, according to the positions and speeds of vehicles in front of and behind the safety gap and the starting point position of an acceleration lane, determining the vehicle confluence trajectory in the ramp confluence area; determining the position when the ramp vehicle enters the acceleration lane, sampling an afflux starting point and an afflux ending point, and calculating an afflux trajectory set according to the afflux starting point and the afflux ending point; selecting an afflux trajectory matched with the collision relational expressions of the ramp vehicle, the front vehicle, the rear vehicle and the tail end of the acceleration lane to obtain a safe trajectory set; and establishing a multi-objective optimization model of the afflux trajectory to calculate all trajectories of the safe trajectory set, and controlling the ramp vehicle to drive into the main line along the afflux trajectory with the minimum function value. According to the method, the safe vehicle confluence track in the ramp confluence area can be effectively planned, the traffic safety and the passing efficiency are greatly improved, and the method has corresponding practical value.

Description

Technical Field

[0001] The present invention relates to the field of traffic control, and in particular to a vehicle merging trajectory planning method for a ramp merging area considering multi-objective optimization in a pure network environment. Background Art

[0002] The merging area of ​​the highway ramp is a bottleneck area that limits the traffic capacity of the highway and is prone to traffic congestion and accidents. There are two main reasons why the merging area becomes a bottleneck: on the one hand, due to the limitations of road conditions, vehicles may have blind spots in the merging area, making it difficult to accurately judge the distance between vehicles; in addition, due to different road speed limits, the speed of ramp vehicles is often lower than that of mainline vehicles, so it is very easy to collide during the lane change process; on the other hand, due to the driver's operating characteristics, whether the vehicle can successfully merge depends largely on whether the driver's operation is reasonable. During the merging process, the driver of the ramp vehicle needs to comprehensively consider the surrounding environment, judge the speed and distance of the mainline vehicle, and then accelerate or decelerate to complete the merging, while the mainline vehicle needs to adjust the speed or change lanes to cooperate with the ramp vehicle. If the driver operates improperly, a traffic accident is likely to occur. In addition, different drivers have great differences in driving ability and driving style. Some drivers are too aggressive and merge when there is a gap without considering the safety of the vehicle spacing, which will force the mainline vehicle to slow down and affect vehicle safety; some drivers are too conservative and delay merging, which will cause ramp congestion. The uncertainty and information asynchrony of human drivers make the ramp merging area problem difficult to properly solve.

[0003] The application of intelligent networked vehicles is expected to improve the traffic conditions in ramp merging areas. Vehicles can communicate with each other to eliminate blind spots and the influence of human drivers. In the merging process, vehicles can cooperate with each other to make optimal decisions and control, thereby planning non-conflicting vehicle trajectories, which can avoid accidents to a certain extent and improve the traffic efficiency of merging areas. Therefore, in the merging area of ​​the highway, planning the merging trajectory of intelligent networked vehicles is very meaningful to improve the safety and efficiency of the ramp merging area.

[0004] At present, there are two main methods for planning vehicle merging trajectories in ramp merging areas:

[0005] 1. Optimization method for merging vehicle trajectories based on conflict elimination. For example, the invention patent application with publication number CN114863681A proposes a vehicle trajectory optimization method for conflict elimination in the main line entrance ramp merging area, which takes the maximum average speed of the entire vehicle as the optimization goal, considers vehicle constraints, safety constraints and merging constraints, uses a linear programming algorithm to express the model, and solves the problem to control the speed of each vehicle at each moment, and obtains the trajectory of the controlled vehicle.

[0006] 2. Multi-objective control method for ramp merging based on artificial intelligence. For example, the invention patent application with publication number CN114241778A proposes a multi-objective optimization control method and system for highway network-connected vehicles to coordinate ramp merging. The method solves the optimal control under multiple objectives by adjusting the acceleration of the merging vehicle and the auxiliary vehicle according to the selected guide vehicle, and ensures the energy consumption optimization of the merging vehicle and the efficient and safe passage of the road while achieving the successful merging of the merging vehicle into the main line.

[0007] However, the existing technical research focuses on the process of ramp vehicles merging into lanes, and there is little mention of the vehicle state adjustment before merging. When determining the merging gap, it is usually assumed that ramp vehicles can merge safely into the gap, which is inconsistent with the actual situation. In addition, when planning the trajectory, there is little consideration for the optimal choice of the merging starting point and merging end point, which are usually the starting and ending points of a given trajectory. At the same time, there is little consideration for the restriction of the length of the acceleration lane. Summary of the invention

[0008] The technical problem to be solved by the present invention is the insufficiency of the existing vehicle merging trajectory planning in the ramp merging area. In view of the above problems in the prior art, a vehicle merging trajectory planning method for the ramp merging area considering multi-objective optimization in a pure network environment is proposed, which comprehensively considers the actual situation of the gap on the main line, the movement state of the vehicle and the road structure of the merging area, and conducts a more in-depth study on the merging trajectory planning of the ramp vehicle.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0010] A vehicle merging trajectory planning method for a ramp merging area considering multi-objective optimization in a pure network environment includes the following steps:

[0011] Determine whether there is a safety gap on the main line and the ramp vehicle can merge into the safety gap safely, and if so, determine the safety gap as the target merging gap;

[0012] According to the vehicle positions and speeds of the gap front vehicle and the gap rear vehicle of the target merging gap, as well as the starting position of the acceleration lane, the positions of each vehicle when the ramp vehicle enters the acceleration lane are determined, and then the merging starting point and merging end point are sampled according to the position of the ramp vehicle when entering the acceleration lane. Finally, trajectory planning is performed based on the sampled merging starting point and merging end point to obtain a preliminary merging trajectory set;

[0013] The collision relations between the gap front vehicle, gap rear vehicle and the end of the acceleration lane in the process of ramp vehicle merging and the target merging gap are calculated respectively, and the merging trajectory that satisfies each collision relation is selected in the merging trajectory set. The merging starting point and merging end point of the selected merging trajectory are planned again to obtain the safe trajectory set.

[0014] Constraints and multi-objective optimization functions are set, and a multi-objective optimization model for the merging trajectory is established according to the constraints and the multi-objective optimization function. The multi-objective optimization model for the merging trajectory is used to respectively calculate the corresponding function values ​​of all merging trajectories in the safe trajectory set, and the merging trajectory with the smallest function value is selected as the optimal merging trajectory, and the ramp vehicles are controlled to enter the target merging gap along the optimal merging trajectory.

[0015] Furthermore, the safety gap specifically refers to a gap where the headway is greater than or equal to the minimum safety headway, and the expression is as follows:

[0016]

[0017] V V1 (t 0 )≥V V3 (t 0 )

[0018] Where T is the headway time; t 0 is the moment when the gap is selected; X V1 (t 0 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 0 The position at the moment; X V3 (t 0 ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t 0 The position at the moment; L is the length of the vehicle; V V3 (t 0 ) is the following vehicle V3 at t 0 The speed of time; T safe is the minimum safe headway; V V1 (t 0 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 0 The speed of time.

[0019] Further, when determining whether there is a safety gap on the main line and the ramp vehicle can safely merge into the safety gap, the step of determining whether the ramp vehicle can safely merge into the safety gap includes:

[0020] The speed of the ramp vehicle is adjusted to be close to the speed of the designated mainline vehicle, and the position of each vehicle at the moment when the ramp vehicle speed adjustment is completed is calculated. If the positions of the ramp vehicle and the vehicle in front of the gap both meet the safe merging condition, the ramp vehicle can safely merge into the safe gap. The safe merging condition expression is as follows:

[0021] X V2 (t 1 )≤X end

[0022] X V2 (t 1 )>XV3 (t 1 )+L

[0023]

[0024] Among them, t 1 is the time when the ramp vehicle speed adjustment ends; X V1 (t 1 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 1 The position at the moment; X V2 (t 1 ) is the ramp vehicle V2 at t 1 The position at the moment; X V3 (t 1 ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t 1 The position at the moment; X end The end point of the acceleration lane.

[0025] Furthermore, the method further includes a step of adjusting the gap when there is no safety gap on the main line or the ramp vehicle cannot safely merge into the safety gap, specifically including:

[0026] If there is no safety gap on the main line, or the ramp vehicle cannot merge safely into the safety gap, the speed of the main line vehicle corresponding to the ramp vehicle is adjusted, including: the vehicle in front of the gap maintains a constant speed and the vehicle behind the gap decelerates, or the vehicle in front of the gap accelerates and the vehicle behind the gap maintains a constant speed, or the vehicle in front of the gap accelerates and the vehicle behind the gap decelerates;

[0027] If the main line vehicle meets the specified conditions after speed adjustment, continue to determine whether there is a safety gap in the main line and whether the ramp vehicle can safely merge into the safety gap. The specified condition expression is as follows: <t ad <t c1

[0028]

[0029] V V1 (t ad )≥V V3 (t ad )

[0030] Among them, t ad is the gap adjustment time; t c1 The maximum time for the ramp vehicle to accelerate; X V1 (t ad ) is the gap between the front vehicle V1 and the front vehicle V1 at t ad Position after seconds; X V3 (t ad ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t ad Position after seconds; V V1 (t ad) is the gap between the front vehicle V1 and the front vehicle V1 at t ad The speed of the vehicle after seconds; V V3 (t ad ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t ad The speed of the vehicle after seconds.

[0031] Furthermore, the calculation formula for the position of each vehicle when the ramp vehicle enters the acceleration lane is as follows:

[0032]

[0033] X V2 (t 2 )=X start

[0034] X V1 (t 2 )=X V1 (t 1 )+V V1 (t 1 )×t 2

[0035] X V3 (t 2 )=X V3 (t 1 )+V V3 (t 1 )×t 2

[0036] Among them, t 2 is the time taken by the ramp vehicle V2 to move to the starting point of the acceleration lane after the speed adjustment is completed; V1 (t 2 ), X V3 (t 2 ) are the positions of the gap front vehicle V1 and the gap rear vehicle V3 when the ramp vehicle V2 drives to the acceleration lane; X V2 (t 2 ) is the position of the ramp vehicle V2 when it drives to the acceleration lane; t 1 The time when the vehicle status adjustment is completed; X V1 (t 1 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 1 The position at the moment; X V2 (t 1 ) is the ramp vehicle V2 at t 1 The position at the moment; X V3 (t 1 ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t 1 The position at the moment; V V1 (t 1 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 1The vehicle speed after time; V V2 (t 1 ) is the ramp vehicle V2 at t 1 The vehicle speed after time; V V3 (t 1 ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t 1 The speed after time; X start The starting point of the acceleration lane.

[0037] Furthermore, sampling the merging starting point and merging end point according to the position of the ramp vehicle when entering the acceleration lane includes: sampling at equal intervals between the position of the ramp vehicle when entering the acceleration lane and the end point of the acceleration lane to obtain sampling points of the merging starting point, and then sampling the merging end point for each merging starting point, and the calculation formula is as follows:

[0038]

[0039] in, is the position of each confluence starting point; S 1 is the sampling interval of the inlet starting point; t 2 is the time taken by the ramp vehicle V2 to move to the starting point of the acceleration lane after the speed adjustment is completed; V2 (t 2 ) is the position of ramp vehicle V2 when it drives to the acceleration lane, X end The end of the acceleration lane; is the position of each confluence terminal; S 2 S is the sampling interval of the inlet end point; ′ To ensure the distance the vehicle moves forward during the lane change process; S is the maximum longitudinal movement distance calculated based on the speed of the ramp vehicle V2 and the maximum allowable acceleration.

[0040] Furthermore, when calculating the collision relationship between the front vehicle in the gap, the rear vehicle in the gap, and the end of the acceleration lane during the ramp vehicle merging process, the collision relationship between the ramp vehicle and the rear vehicle in the gap, the collision relationship between the ramp vehicle and the front vehicle in the gap, and the collision relationship between the ramp vehicle and the end of the acceleration lane are calculated based on the rectangular model and the col function, where:

[0041] The collision relationship between the ramp vehicle and the vehicle behind in the gap is as follows:

[0042]

[0043] Where τ is the duration of inflow; X V2 (t), Y V2 (t) are the vertex horizontal and vertical coordinates of ramp vehicle V2, X V2a (t), X V2b (t), XV2c (t), X V2d (t) are the horizontal coordinates of the four vertices of the ramp vehicle V2, Y V2a (t), Y V2b (t), Y V2c (t), Y V2d (t) are the vertical coordinates of the four vertices of the ramp vehicle V2; V3 (t), Y V3 (t) are the horizontal and vertical coordinate sets of the vertices of the vehicle V3 behind the gap, X V3a (t), X V3b (t), X V3c (t), X V3d (t) are the horizontal coordinates of the four vertices of the vehicle V3 behind the gap, Y V3a (t), Y V3b (t), Y V3c (t), Y V3d (t) are the vertical coordinates of the four vertices of the vehicle V3 behind the gap;

[0044] The collision relationship between the ramp vehicle and the gap front vehicle is as follows:

[0045]

[0046] Among them, X V1 (t), Y V1 (t) The horizontal and vertical coordinates of the vertex of the gap front vehicle V1, X V1a (t), X V1b (t), X V1c (t), X V1d (t) are the horizontal coordinates of the four vertices of the front vehicle V1 in the gap, Y V1a (t), Y V1b (t), Y V1c (t), Y V1d (t) are the vertical coordinates of the four vertices of the gap front vehicle V1;

[0047] The collision relationship between the ramp vehicle and the end of the acceleration lane is as follows:

[0048]

[0049] Among them, X p , Y p are the horizontal and vertical coordinate sets of the two endpoints of the end segment of the acceleration lane, respectively. p1 , X p2 are the horizontal coordinates of the two endpoints of the end segment of the acceleration lane, Y p1 , Y p2 They are the ordinates of the two endpoints of the end segment of the acceleration lane.

[0050] Furthermore, the constraint condition calculation formula is as follows:

[0051] v min ≤v 9 (t)≤v max

[0052] |a x (t)| <min{a xmax ,μg}

[0053]

[0054] k p (t)≤k max

[0055]

[0056] TTC i (t)≥TTC Safe orTTC i (t)≤0

[0057]

[0058] Among them, v p (t) is the velocity corresponding to each discrete point on the trajectory; v max is the maximum speed limit; v min is the minimum speed limit; a x (t) is the longitudinal acceleration of each discrete point on the trajectory; a y (t) is the lateral acceleration of each discrete point on the trajectory; a xmax is the maximum longitudinal acceleration limit; a ymax is the maximum lateral acceleration limit; μ is the road adhesion coefficient; g is the gravitational acceleration; k p (t) is the curvature of each discrete point; k max is the maximum curvature limit; x(t e ) is the target longitudinal position of the vehicle; y(t e ) is the target lateral position of the vehicle; is the initial longitudinal velocity of the vehicle; TTC safe is the minimum safe TTC value; TTC 1 (t) is the collision time between the ramp vehicle V2 and the gap vehicle V3; TTC 2 (t) is the collision time between the ramp vehicle V2 and the gap front vehicle V1; TTC 3 (t) is the collision time between the ramp vehicle V2 and the end of the acceleration lane; X V1 (t), X V3 (t) is the position of the gap front vehicle V1 and the gap rear vehicle V3 at time t; XV2 (t) is the position of ramp vehicle V2 at time t; V V1 (t), V V2 (t), V V3 (t) are the speeds of the gap front vehicle V1, ramp vehicle V2, and gap rear vehicle V3 at time t; X end The end of the acceleration lane.

[0059] Furthermore, the specific formula of the multi-objective optimization function is as follows:

[0060]

[0061] J c =k d J d +k s J s

[0062]

[0063] In the formula, J u is the objective function of the inflow urgency of the trajectory with inflow starting point i as the inflow starting point; L 0 is the length of the acceleration lane; L si J is the distance from the merging starting point i to the end of the acceleration lane; safe is the security equilibrium objective function; TTC 1 (t) is the collision time between the ramp vehicle V2 and the gap vehicle V3; TTC 2 (t) is the collision time between the ramp vehicle V2 and the gap front vehicle V1; TTC 3 (t) is the collision time between the ramp vehicle V2 and the end of the acceleration lane; J c is the comfort objective function; τ is the duration of inflow; J d , J s are the longitudinal and lateral comfort weighting items respectively; k d , k s is the weight coefficient; are the longitudinal and lateral impacts of the vehicle respectively; J k is the smoothness objective function; k p (t) is the curvature of each discrete point on the trajectory; k pmax is the maximum curvature among all trajectory curves.

[0064] Furthermore, when a multi-objective optimization model of the input trajectory is established according to the constraint conditions and the multi-objective optimization function, it includes:

[0065] The constraint conditions are used as the constraint conditions of the multi-objective optimization model of the imported trajectory. After normalizing each objective function of the multi-objective optimization function, the objective function of the multi-objective optimization model of the imported trajectory is obtained. The expression of the multi-objective optimization model of the imported trajectory is as follows:

[0066]

[0067] Among them, J u is the objective function of the inflow urgency of the trajectory with inflow starting point i as the inflow starting point; J u,min and J u,max are the maximum and minimum values ​​of the input urgency objective function respectively; J safe is the security equilibrium objective function; J safe,min and J safe,max are the maximum and minimum values ​​of the security equilibrium objective function respectively; J c is the comfort objective function; J c,min and J c,max are the maximum and minimum values ​​of the comfort objective function respectively; J k is the smoothness objective function; J k,min and J k,max are the maximum and minimum values ​​of the smoothness objective function respectively; ω 1 ,ω 2 ,ω 3 ,ω 4 is the weight of each objective function, and ω 1 +ω 2 +ω 3 +ω 4 =1;v p (t) is the velocity corresponding to each discrete point on the trajectory; v max is the maximum speed limit; v min is the minimum speed limit; a x (t) is the longitudinal acceleration of each discrete point on the trajectory; a y (t) is the lateral acceleration of each discrete point on the trajectory; a xmax is the maximum longitudinal acceleration limit; a ymax is the maximum lateral acceleration limit; μ is the road adhesion coefficient; g is the gravitational acceleration; k p (t) is the curvature of each discrete point; k max is the maximum curvature limit; x(t e ) is the target longitudinal position of the vehicle; y(t e ) is the target lateral position of the vehicle; is the initial longitudinal velocity of the vehicle.

[0068] Compared with the prior art, the advantages of the present invention are:

[0069] The present invention proposes a safety gap search method and sets a safety gap evaluation standard. On the basis of the existence of a safety gap, the target speed of the ramp vehicle is set according to the actual movement of the vehicle, and the speed of the ramp vehicle is adjusted to determine whether the vehicle can merge into the safety gap, which lays a foundation for subsequent trajectory planning and makes up for the shortcomings of existing research on merging gap search in ramp merging areas.

[0070] In the merging trajectory planning stage, the present invention takes into account the selection of the merging starting point and the merging end point, and proposes a process of "initial trajectory planning" and "trajectory re-planning", which can achieve the goal of obtaining the optimal merging starting point on the one hand, and determine the safe end point area on the other hand to ensure the vehicle safety of the entire merging process, and the whole process is simple and easy to implement; at the same time, in the entire planning process, the limitation of the length of the acceleration lane is taken into consideration, and finally a trajectory with the best comprehensive performance is obtained, and it has the optimal merging starting point and end point, which makes up for the shortcomings of the existing research on merging trajectory planning in the merging area. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 is a flow chart of an embodiment of the present invention;

[0072] Figure 2 It is a trajectory planning strategy diagram imported into the embodiment of the present invention;

[0073] Figure 3 is a diagram of a process of determining an inlet gap in an embodiment of the present invention;

[0074] Figure 4 It is a graph of initial trajectory planning results imported into the embodiment of the present invention;

[0075] Figure 5 is a diagram of safety detection results in an embodiment of the present invention;

[0076] Figure 6 is an example diagram of the optimal trajectory in an embodiment of the present invention;

[0077] Figure 7 It is a diagram showing the vehicle state change results on the optimal trajectory in an embodiment of the present invention. DETAILED DESCRIPTION

[0078] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0079] This embodiment provides a vehicle merging trajectory planning method for a ramp merging area considering multi-objective optimization in a purely connected environment. On the basis of the existing merging trajectory planning strategy, the movement of mainline vehicles is considered, and combined with multi-objective optimization theory, the urgency of vehicle merging, safety balance, driver comfort and trajectory smoothness are considered in a purely connected environment. A safe, smooth, collision-free, and optimal merging trajectory is planned for ramp vehicles, and theoretical support is provided for the trajectory planning method of CAVs in the merging area of ​​highways.

[0080] like Figure 1 As shown, the method of this embodiment includes the following steps:

[0081] Step S1: Determine the target merging gap based on the headway and vehicle status adjustment;

[0082] Specifically, based on the headway time of the mainline vehicle, it is determined whether there is a safety gap on the mainline and the ramp vehicle can safely merge into the safety gap. If yes, the safety gap is determined as the target merging gap. Otherwise, after adjusting the speed of the mainline vehicle, it is determined again based on the headway time of the mainline vehicle whether there is a safety gap on the mainline and the ramp vehicle can safely merge into the safety gap.

[0083] Step S2: obtaining a preliminary vehicle merging trajectory based on a quintic polynomial planning algorithm;

[0084] Specifically, according to the vehicle positions and speeds of the gap front vehicle and the gap rear vehicle of the target merging gap, as well as the starting position of the acceleration lane, the positions of each vehicle when the ramp vehicle enters the acceleration lane are determined, and then the merging starting point and merging end point are sampled according to the position of the ramp vehicle when entering the acceleration lane. Finally, a quintic polynomial planning algorithm is used to perform trajectory planning based on the sampled merging starting point and merging end point to obtain a preliminary merging trajectory set.

[0085] Step S3: Based on the rectangular model and the col function, a safety check is performed on the vehicle merging trajectory to obtain a collision-free terminal area.

[0086] Specifically, based on the rectangular model and col function, the collision relations between the gap front vehicle, gap rear vehicle and the end of the acceleration lane in the process of ramp vehicle merging and the target merging gap are calculated respectively, and the merging trajectories matching each collision relation are selected from the merging trajectory set. The planning algorithm of the quintic polynomial is used again to perform trajectory planning again according to the merging starting point and merging end point of the matched merging trajectory to obtain the safe trajectory set.

[0087] Step S4: based on a multi-objective merging vehicle trajectory optimization method, obtaining an optimal trajectory for the ramp vehicle to merge;

[0088] Specifically, constraint conditions and a multi-objective optimization function are set, a multi-objective optimization model of the merging trajectory is established according to the constraint conditions and the multi-objective optimization function, the multi-objective optimization model of the merging trajectory is used to respectively calculate the corresponding function values ​​of all merging trajectories in the safe trajectory set, the merging trajectory with the smallest function value is selected as the optimal merging trajectory, and the ramp vehicles are controlled to enter the target merging gap along the optimal merging trajectory.

[0089] Through the above steps, the merging trajectory planning of the vehicle in the ramp merging area in a purely connected environment can be completed.

[0090] Step S5: Use MATLAB software to simulate and analyze the merging process to verify the effectiveness of the trajectory planning method.

[0091] Refer to the following Figure 2 , the above steps are explained in detail respectively.

[0092] Step S1 of this embodiment specifically includes the following steps:

[0093] Step S1.1: Safety gap determination.

[0094] This embodiment uses the headway time between mainline vehicles to determine whether the gap between mainline vehicles is safe. The gap that meets the condition is called a safe gap. The safe gap specifically refers to a gap where the headway time is greater than or equal to the minimum safe headway time. The expression is as follows:

[0095]

[0096] V V1 (t 0 )≥V V3 (t 0 )

[0097] Where T is the headway time; t 0 is the moment when the gap is selected; X V1 (t 0 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 0 The position at the moment; X V3 (t 0 ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t 0 The position at the moment; L is the length of the vehicle; V V3 (t 0 ) is the following vehicle V3 at t 0 The speed of time; T safe is the minimum safe headway; V V1 (t 0 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 0 The speed of time.

[0098] Before judging whether there is a safety gap on the main line and the ramp vehicle can merge safely into the safety gap, when gap selection is required, the gap with the maximum headway between the main line vehicles is preferentially selected for safety gap judgment. If it is a safety gap, subsequent vehicle merging judgment is performed;

[0099] Step S1.2: Vehicle merging judgment.

[0100] Before the ramp vehicle merges into the gap between the mainline vehicles, its speed needs to be adjusted to a speed close to that of the mainline vehicle. Then, the positions of the ramp vehicle and the mainline vehicle corresponding to the safety gap at the end of the speed adjustment are calculated. Based on the conditions that the ramp vehicle must meet to merge safely into the safety gap, it is determined whether the gap formed by the mainline vehicle's position allows the vehicle to merge safely. Specifically, the following steps are included:

[0101] Calculate the position of each vehicle at the end of ramp vehicle speed adjustment. When ramp vehicles accelerate, they need to consider the length of the acceleration lane, so it is necessary to compare the critical speed V of the vehicle moving at a constant acceleration to the end of the acceleration lane. c and the target speed set for ramp vehicle V2 The expression is as follows:

[0102]

[0103] Among them, X end is the end point of the acceleration lane, t acc For ramp vehicles from t 0 Time is accelerating at every moment;

[0104] right and These two situations are discussed in detail:

[0105] when , calculate the position of each vehicle at the moment when the ramp vehicle speed adjustment ends, that is:

[0106]

[0107] t 1 =t 0 +t c1

[0108] X V1 (t 1 )=V V1 (t 0 )×t 1 +X V1 (t 0 )

[0109] X V3 (t 1 )=VV3 (t 0 )×t 1 +X V3 (t 0 )

[0110]

[0111] Among them, t c1 is the maximum time of ramp vehicle acceleration, t 1 is the time when the vehicle state adjustment is completed, that is, the time when the ramp vehicle speed adjustment is completed, X V1 (t 1 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 1 The position at the moment; X V2 (t 1 ) is the ramp vehicle V2 at t 1 The position at the moment; X V3 (t 1 ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t 1 The position at the moment; a acc For maximum comfortable acceleration.

[0112] when , calculate the position of each vehicle at the moment when the ramp vehicle speed adjustment ends, that is:

[0113]

[0114] t 0 +t acc ≤t 1 ≤t 0 +t c2

[0115] X V1 (t 1 )=V V1 (t 0 )×t 1 +X V1 (t 0 )

[0116] X V3 (t 1 )=V V3 (t 0 )×t 1 +X V3 (t 0 )

[0117]

[0118] Among them, t c2 For ramp vehicles from t 0 The time it takes to reach the end of the acceleration lane.

[0119] After calculating the positions of the ramp vehicle and the corresponding mainline vehicle, the target merging gap is determined according to the conditions that the ramp vehicle must meet to merge safely into the safety gap. Specifically, if the positions of the ramp vehicle and the vehicle ahead of the gap both meet the safe merging conditions, the ramp vehicle can merge safely into the safety gap. The safe merging condition expression is as follows:

[0120] X V2 (t 1 )≤X end

[0121] X V2 (t 1 )>X V3 (t 1 )+L

[0122]

[0123] Among them, t 1 is the time when the ramp vehicle speed adjustment ends; X V1 (t 1 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 1 The position at the moment; X V2 (t 1 ) is the ramp vehicle V2 at t 1 The position at the moment; X V3 (t 1 ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t 1 The position at the moment; X end is the end point of the acceleration lane. If the ramp vehicle can meet the above safe merging conditions after speed adjustment, the selected gap is the target merging gap.

[0124] Step S1.3: Gap adjustment.

[0125] If the gaps between mainline vehicles are not safe gaps, or the selected safe gaps do not meet the requirements for ramp vehicles to merge safely, gap adjustments are required, including:

[0126] The speed of the mainline vehicles corresponding to the ramp vehicles (i.e., the front vehicle and the rear vehicle of the selected gap) is adjusted. In this embodiment, there are three schemes for adjusting the speed of the mainline vehicles. In order to reduce the interference to the mainline traffic flow, scheme 1 is given priority, followed by scheme 2, and finally scheme 3.

[0127] Solution 1: The front vehicle V1 in the gap maintains a constant speed, and the rear vehicle V3 in the gap slows down. The expression is as follows:

[0128] V V1 (t ad )=V V1(t 0 )

[0129] V V3 (t ad )=max(V min ,V V3 (t 0 )+a dec ×t ad )

[0130] X V1 (t ad )=V V1 (t ad )×t ad +X V1 (t 0 )

[0131] Solution 2: The front vehicle V1 accelerates, and the rear vehicle V3 maintains a constant speed. The expression is as follows:

[0132] V V1 (t ad )=min(V max ,V V1 (t 0 )+a acc ×t ad )

[0133] V V3 (t ad )=V V3 (t 0 )

[0134]

[0135] Solution 3: The front vehicle V1 in the gap accelerates, and the rear vehicle V3 in the gap decelerates. The expression is as follows:

[0136] The calculation of the speed and position of the vehicle V1 in the gap is consistent with that of Scheme 2, that is,

[0137] V V1 (t ad )=min(V max ,V V1 (t 0 )+a acc ×t ad )

[0138]

[0139] The speed and position calculation of the vehicle V3 behind the gap is consistent with that of Scheme 1, that is,

[0140] V V3 (t ad )=max(Vmin ,V V3 (t 0 )+a dec ×t ad )

[0141]

[0142] In the above formulas, V min The minimum speed limit for the main line; a dec is the vehicle deceleration; V max The maximum speed limit of the main line; t ad Adjust time for gap; X V1 (t ad ) is the gap between the front vehicle V1 and the front vehicle V1 at t ad Position after seconds; X V3 (t ad ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t ad Position after seconds; V V1 (t ad ) is the gap between the front vehicle V1 and the front vehicle V1 at t ad The speed of the vehicle after seconds; V V3 (t ad ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t ad The speed of the vehicle after seconds.

[0143] If the mainline vehicle meets the specified conditions after speed adjustment, it is further determined whether there is a safety gap in the mainline and the ramp vehicle can safely merge into the safety gap. The specified condition, i.e., the conditional expression of the gap adjustment, is as follows: <t ad <t c1

[0144]

[0145] V V1 (t ad )≥V V3 (t ad )

[0146] Among them, t ad is the gap adjustment time; t c1 The maximum time for the ramp vehicle to accelerate; X V1 (t ad ) is the gap between the front vehicle V1 and the front vehicle V1 at t ad Position after seconds; X V3 (t ad ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t ad Position after seconds; V V1 (t ad ) is the gap between the front vehicle V1 and the front vehicle V1 at t ad The speed of the vehicle after seconds; V V3 (t ad) is the gap between the rear vehicle V3 and the rear vehicle V3 at t ad The speed of the vehicle after seconds.

[0147] It should be noted that when continuing to determine whether there is a safety gap on the main line and the ramp vehicle can safely merge into the safety gap, the ramp vehicle can safely merge into the safety gap only if the following conditions are met:

[0148] X V2 (t ad )≤X end

[0149] X V2 (t ad )>X V3 (t ad )+L

[0150]

[0151] Ramp vehicle V2 is V V2 (t 0 ) Accelerate to Need c3 seconds, need to be based on t c3 With t ad Small relation calculation X V2 (t ad ) size.

[0152] When t c3 ≤t ad hour,

[0153]

[0154] When t c3 >t ad hour,

[0155]

[0156] In the formula, is the target speed of V2; X V2 (t ad ) is V2 at t ad Position after seconds; t c3 Yes V V2 (t 0 ) Accelerate to The time required; V V2 (t 0 ) is the ramp vehicle V2 at t 0 Speed ​​of time; X V2 (t 0 ) Ramp vehicle V2 at t 0 The position at the moment.

[0157] If the mainline vehicles corresponding to the selected gap can form a safety gap after speed adjustment, and the ramp vehicles can merge into the safety gap after speed adjustment, then the selected gap is the target gap.

[0158] like Figure 3 As shown, the mainline vehicles V1 and V3 before and after the selected gap can form a safe gap after the state adjustment in step S1, and the ramp vehicle V2 can merge into the gap after speed adjustment.

[0159] The specific steps of step S2 of this embodiment are as follows:

[0160] Step S2.1: Vehicle position determination.

[0161] In order to ensure that the ramp vehicle has entered the acceleration lane, it is necessary to determine the position of the merging vehicle when it enters the acceleration lane. Based on the position and speed of each vehicle at the end of the speed adjustment obtained in the target merging gap determination stage, as well as the starting position of the acceleration lane, the position and speed information of the ramp vehicle and the main line vehicle when the ramp vehicle enters the acceleration lane can be determined. The calculation formula is as follows:

[0162] When X V2 (t 1 ) <X start When , the vehicles on the ramp move at a constant speed.

[0163]

[0164] X V2 (t 2 )=X start

[0165] X V1 (t 2 )=X V1 (t 1 )+V V1 (t 1 )×t 2

[0166] X 53 (t 2 )=X 53 (t 1 )+V V3 (t 1 )×t 2

[0167] Among them, t 2 is the time taken by the ramp vehicle V2 to move to the starting point of the acceleration lane after the speed adjustment is completed; V1 (t 2 ), X V3 (t 2) are the positions of the gap front vehicle V1 and the gap rear vehicle V3 when the ramp vehicle V2 drives to the acceleration lane; X V2 (t 2 ) is the position of the ramp vehicle V2 when it drives to the acceleration lane; t 1 The time when the vehicle status adjustment is completed; X V1 (t 1 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 1 The position at the moment; X V2 (t 1 ) is the ramp vehicle V2 at t 1 The position at the moment; X V3 (t 1 ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t 1 The position at the moment; V V1 (t 1 ) is the gap between the front vehicle V1 and the front vehicle V1 at t 1 The vehicle speed after time; V V2 (t 1 ) is the ramp vehicle V2 at t 1 The vehicle speed after time; V V3 (t 1 ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t 1 The speed after time; X start The starting point of the acceleration lane.

[0168] Step S2.2: Sampling the start point and the end point.

[0169] When the ramp vehicle reaches the target speed and reaches the acceleration lane, it can start merging at any position on the acceleration lane. Before planning the merging trajectory, it is necessary to determine the merging start point and the merging end point. Therefore, when sampling the merging start point and the merging end point according to the position of the ramp vehicle when it enters the acceleration lane, it includes: sampling at equal intervals between the position of the ramp vehicle when it enters the acceleration lane and the end point of the acceleration lane, such as Figure 2 As shown in the schematic diagram of the sampling of the inlet starting point, the sampling points constitute the sampling of the inlet starting point. Then, the sampling of the inlet end point is performed for each inlet starting point i, and the sampling end point j i Construct the sampling set J corresponding to the sampling starting point i i , the calculation formula is as follows:

[0170]

[0171] in, is the position of each confluence starting point; S 1 is the sampling interval of the inlet starting point; t 2 is the time taken by the ramp vehicle V2 to move to the starting point of the acceleration lane after the speed adjustment is completed; V2 (t2 ) is the position of ramp vehicle V2 when it drives to the acceleration lane, X end The end of the acceleration lane; is the position of each confluence terminal; S 2 S is the sampling interval of the inlet end point; ′ To ensure the distance the vehicle moves forward during the lane change process; S is the maximum longitudinal movement distance calculated based on the speed of the ramp vehicle V2 and the maximum allowable acceleration.

[0172] Step S2.3: Import trajectory planning.

[0173] For each starting sampling point i, there is a corresponding set of end sampling points J i , matching starting point i and each end point j i , using the quintic polynomial programming algorithm in the Frenet coordinate system, the inflow trajectory is generated, such as Figure 2 As shown in the initial trajectory planning diagram, each pair of starting point i and sampling end point j i can generate corresponding alternative trajectories. The calculation formula is:

[0174]

[0175] In the formula, a i 、b i , i=0,1,…,5 are the coefficients of the polynomial; x(t), y(t), are the displacement, velocity and acceleration in the longitudinal and lateral directions respectively; t is the lane changing time.

[0176] Through steps S2.1 and S2.2, the starting and ending states of the vehicle can be obtained. Combined with the formula of step S2.3, a i and b i Solve it, and then get the incoming trajectory and add it to the incoming trajectory set. The planning result of the incoming trajectory in the incoming trajectory set is as follows Figure 4 shown.

[0177] The specific steps of step S3 of this embodiment are as follows:

[0178] Step S3.1: Calculate the collision risk with the vehicle behind in the gap.

[0179] First, consider the collision relationship between the ramp vehicle and the vehicle behind in the gap. The collision relationship between the ramp vehicle and the vehicle behind in the gap is as follows:

[0180]

[0181]

[0182] Where τ is the duration of inflow; XV2 (t), Y V2 (t) are the vertex horizontal and vertical coordinates of ramp vehicle V2, X V2a (t), C V2p (t), x V2c (t), X V2d (t) are the horizontal coordinates of the four vertices of the ramp vehicle V2, Y V2a (t), Y V2b (t), Y V2c (t), Y V2d (t) are the vertical coordinates of the four vertices of the ramp vehicle V2; V3 (t), Y V3 (t) are the horizontal and vertical coordinate sets of the vertices of the vehicle V3 behind the gap, X V3a (t), X V3b (t), X V3c (t), X V3d (t) are the horizontal coordinates of the four vertices of the vehicle V3 behind the gap, Y V3a (t), Y V3b (t), Y V3c (t), Y V3d (t) are the vertical coordinates of the four vertices of the vehicle V3 behind the gap.

[0183] The above formula is used to construct a rectangular model for the ramp vehicle and the corresponding gap rear vehicle on the main line. As long as the two rectangles overlap during the merging process, the two vehicles have collided, such as Figure 2 As shown in the schematic diagram of trajectory safety detection, the candidate trajectories generated by each sampling starting point are traversed according to the collision relationship. When a trajectory satisfies the above formula, then the trajectory is a safe trajectory. According to the position distribution of the sampling end point of the safe trajectory, the collision-free end point candidate area Θ of the current sampling starting point i can be obtained i1 .

[0184] Step S3.2: Calculate the collision risk with the vehicle ahead in the gap.

[0185] When a ramp vehicle merges, it may not only collide with the vehicle behind it, but also with the vehicle in front of it. The collision relationship between the ramp vehicle and the vehicle in front of it is as follows:

[0186]

[0187] Among them, X V1 (t), Y V1 (t) The horizontal and vertical coordinates of the vertex of the gap front vehicle V1, X V1a (t), X V1b (t), X V1c (t), X V1d(t) are the horizontal coordinates of the four vertices of the front vehicle V1 in the gap, Y V1a (t), Y V1b (t), Y V1c (t), Y V1d (t) are the vertical coordinates of the four vertices of the vehicle V1 in the gap.

[0188] The above formula is used to construct a rectangular model for the ramp vehicle and the gap ahead vehicle on the main line. As long as the two rectangles overlap during the merging process, the two vehicles have collided, such as Figure 2 As shown in the schematic diagram of the middle trajectory safety detection, in the collision-free end point candidate area Θ i1 Based on this, the trajectory generated by each sampling starting point i is subjected to collision detection of the gap vehicle in front. When the above formula is satisfied, it is a collision-free trajectory. According to the position distribution of the sampling end point of the collision-free trajectory, the collision-free end point candidate area Θ of the current sampling starting point i can be obtained. i2 .

[0189] Step S3.3: Calculate the collision risk with the end of the acceleration lane.

[0190] If the distance between the vehicle's merging point and the end of the acceleration lane is too close, the vehicle may collide with the end of the acceleration lane when merging. The collision relationship between the ramp vehicle and the end of the acceleration lane is as follows:

[0191]

[0192] Among them, X p , Y p are the horizontal and vertical coordinate sets of the two endpoints of the end segment of the acceleration lane, respectively. p1 , X p2 are the horizontal coordinates of the two endpoints of the end segment of the acceleration lane, Y p1 , Y p2 They are the ordinates of the two endpoints of the end segment of the acceleration lane.

[0193] The end of the acceleration lane is simplified into a line segment, and collision detection is performed between the ramp vehicle and the end of the acceleration lane according to the collision detection function operation principle of rectangle and line segment, such as Figure 2 As shown in the schematic diagram of the middle trajectory safety detection, in the collision-free end point candidate area Θ i2 Based on this, the trajectory generated by each sampling starting point i is subjected to safety detection at the end of the acceleration lane. When the above formula is satisfied, there is no collision, and the collision-free end point candidate area Θ of the current sampling starting point i is obtained. i3 .

[0194] Combining the above three aspects of collision detection, the final collision-free end area can be obtained, which is Θ i1 , Θ i2 , Θi3 The intersection area of ​​. Figure 2 As shown in the trajectory re-planning diagram, i1 , Θ i2 , Θ i3 The sampling end point and the corresponding sampling starting point of the intersection area are used to generate the merging trajectory again using the fifth-order polynomial programming algorithm in the Frenet coordinate system, as shown in Figure 5 shown.

[0195] The specific steps of step S4 of this embodiment are as follows:

[0196] Step S4.1: Design constraints.

[0197] In this embodiment, the five indicators of speed, acceleration, curvature, vehicle rollover prevention, and safety are constrained respectively. The five constraints of speed, acceleration, curvature, vehicle rollover prevention, and safety of ramp vehicles are set to ensure the smooth merging of vehicles. The calculation formula is as follows:

[0198] v min ≤v p (t)≤v max

[0199] |a x (t)| <min{a xmax ,μg}

[0200]

[0201] k p (t)≤k max

[0202]

[0203] TTC i (t)≥TTC safe orTTC i (t)≤0

[0204]

[0205] Among them, v p (t) is the velocity corresponding to each discrete point on the trajectory; v max is the maximum speed limit; v min is the minimum speed limit; a x (t) is the longitudinal acceleration of each discrete point on the trajectory; a y (t) is the lateral acceleration of each discrete point on the trajectory; a xmax is the maximum longitudinal acceleration limit; a ymax is the maximum lateral acceleration limit; μ is the road adhesion coefficient; g is the gravitational acceleration; k p(t) is the curvature of each discrete point; k max is the maximum curvature limit; x(t e ) is the target longitudinal position of the vehicle; y(t e ) is the target lateral position of the vehicle; is the initial longitudinal velocity of the vehicle; TTC safe is the minimum safe TTC value; TTC 1 (t) is the collision time between the ramp vehicle V2 and the gap vehicle V3; TTC 2 (t) is the collision time between the ramp vehicle V2 and the gap front vehicle V1; TTC 3 (t) is the collision time between the ramp vehicle V2 and the end of the acceleration lane; X V1 (t), X V3 (t) is the position of the gap front vehicle V1 and the gap rear vehicle V3 at time t; X V2 (t) is the position of ramp vehicle V2 at time t; V V1 (t), V V2 (t), V V3 (t) are the speeds of the gap front vehicle V1, ramp vehicle V2, and gap rear vehicle V3 at time t; X end The end of the acceleration lane.

[0206] Step S4.2: Design objective function:

[0207] In this embodiment, a multi-objective optimization function is designed based on four indicators: urgency of ramp vehicle merging, safety balance, comfort, and trajectory smoothness, so as to obtain the optimal merging trajectory under the current environment. The specific formula is as follows:

[0208]

[0209] J c =k d J d +k s K s

[0210]

[0211] In the formula, J u is the objective function of the inflow urgency of the trajectory with inflow starting point i as the inflow starting point; L 0 is the length of the acceleration lane; L si J is the distance from the merging starting point i to the end of the acceleration lane; safe is the security equilibrium objective function; TTC 1 (t) is the collision time between the ramp vehicle V2 and the gap vehicle V3; TTC 2 (t) is the collision time between the ramp vehicle V2 and the gap front vehicle V1; TTC3 (t) is the collision time between the ramp vehicle V2 and the end of the acceleration lane; J d , J s are the longitudinal and lateral comfort weighting items respectively; k d , k s is the weight coefficient; J c is the comfort objective function; τ is the duration of inflow; are the longitudinal and lateral impacts of the vehicle respectively; J k is the smoothness objective function; k p (t) is the curvature of each discrete point on the trajectory; k pmax is the maximum curvature among all trajectory curves.

[0212] Step S4.3: Establish a multi-objective optimization model for the incoming trajectory.

[0213] The above constraints and multiple optimization objectives are integrated to establish a multi-objective optimization model for the imported trajectory. Specifically, the constraints are used as constraints for the multi-objective optimization model for the imported trajectory. After normalizing each objective function of the multi-objective optimization function, the objective function of the multi-objective optimization model for the imported trajectory is obtained. The expression of the multi-objective optimization model for the imported trajectory is as follows:

[0214]

[0215] Among them, J u is the objective function of the inflow urgency of the trajectory with inflow starting point i as the inflow starting point; J u,min and J u,max are the maximum and minimum values ​​of the input urgency objective function respectively; J safe is the security equilibrium objective function; J safe,min and J safe,max are the maximum and minimum values ​​of the security equilibrium objective function respectively; J c is the comfort objective function; J c,min and J c,max are the maximum and minimum values ​​of the comfort objective function respectively; J k is the smoothness objective function; J k,min and J k,max are the maximum and minimum values ​​of the smoothness objective function respectively; ω 1 ,ω 2 ,ω 3 ,ω 4 is the weight of each objective function, and ω 1 +ω 2 +ω 3 +ω 4 =1;v p (t) is the velocity corresponding to each discrete point on the trajectory; vmax is the maximum speed limit; v min is the minimum speed limit; a x (t) is the longitudinal acceleration of each discrete point on the trajectory; a y (t) is the lateral acceleration of each discrete point on the trajectory; a xmax is the maximum longitudinal acceleration limit; a ymax is the maximum lateral acceleration limit; μ is the road adhesion coefficient; g is the gravitational acceleration; k p (t) is the curvature of each discrete point; k max is the maximum curvature limit; x(t e ) is the target longitudinal position of the vehicle; y(t e ) is the target lateral position of the vehicle; is the initial longitudinal velocity of the vehicle.

[0216] like Figure 2 As shown in the schematic diagram of obtaining the optimal trajectory, the multi-objective function of the multi-objective optimization model of the incoming trajectory is used to calculate the function value of all the incoming trajectories in the safe trajectory set. When the function value is the smallest, the incoming trajectory is optimal, thereby obtaining the incoming trajectory with the best comprehensive performance, as shown in Figure 6 shown.

[0217] The specific steps of step S5 of this embodiment are as follows:

[0218] Use MATLAB software to set up the merging scenario: the minimum speed limit of the main line is 60km / h, the maximum speed limit is 120km / h, the minimum speed limit of the ramp is 40km / h, the starting point of the control area is 300m upstream of the starting point of the acceleration lane, and the length of the acceleration lane is 200m. Taking the starting point of the control area as the origin of the coordinate axis, the horizontal coordinate of the starting point of the acceleration lane is 300, and the horizontal coordinate of the end point of the acceleration lane is 500. Design the initial position, initial speed, initial acceleration and other state parameters for the main line vehicles and ramp vehicles respectively. According to the speed and position relationship between the main line vehicles and ramp vehicles, adjust the vehicle state and make merging judgments to obtain the final target merging gap. Plan and simulate the merging trajectory of the ramp vehicle, and the vehicle state change results on the optimal trajectory are as follows: Figure 7 As shown, the simulation results show that at the beginning and completion of the merging, the simulation results of the ramp vehicle state values ​​are consistent with the actual lane changing scenario, and each state value is within the limit range. The method of this embodiment can obtain the optimal merging trajectory and meet the requirements of driver comfort and vehicle operation smoothness at the same time.

[0219] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment, characterized in that: The following steps are involved: Determine whether there is a safety gap on the main line and the ramp vehicle can merge into the safety gap safely, and if so, determine the safety gap as the target merging gap; According to the vehicle positions and speeds of the gap front vehicle and the gap rear vehicle of the target merging gap, as well as the starting position of the acceleration lane, the positions of each vehicle when the ramp vehicle enters the acceleration lane are determined, and then the merging starting point and merging end point are sampled according to the position of the ramp vehicle when entering the acceleration lane. Finally, trajectory planning is performed based on the sampled merging starting point and merging end point to obtain a preliminary merging trajectory set; The collision relations between the gap front vehicle, gap rear vehicle and the end of the acceleration lane in the process of ramp vehicle merging and the target merging gap are calculated respectively, and the merging trajectory that satisfies each collision relation is selected in the merging trajectory set. The merging starting point and merging end point of the selected merging trajectory are planned again to obtain the safe trajectory set. Constraints and multi-objective optimization functions are set, and a multi-objective optimization model for the merging trajectory is established according to the constraints and the multi-objective optimization function. The multi-objective optimization model for the merging trajectory is used to respectively calculate the corresponding function values ​​of all merging trajectories in the safe trajectory set, and the merging trajectory with the smallest function value is selected as the optimal merging trajectory, and the ramp vehicles are controlled to enter the target merging gap along the optimal merging trajectory.

2. The vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment according to claim 1 is characterized in that: The safety gap specifically refers to a gap where the headway is greater than or equal to the minimum safety headway, and the expression is as follows: V V1 (t0)≥V V3 (t0) Where T is the headway time; t0 is the time when the gap is selected; X V1 (t0) is the position of the front vehicle V1 at time t0; X V3 (t0) is the position of the rear vehicle V3 at time t0; L is the vehicle length; V V3 (t0) is the speed of the following vehicle V3 at time t0; T safe is the minimum safe headway; V V1 (t0) is the speed of the gap front vehicle V1 at time t0.

3. The vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment according to claim 1 is characterized in that: When judging whether there is a safety gap on the main line and whether the ramp vehicle can safely merge into the safety gap, the step of judging whether the ramp vehicle can safely merge into the safety gap includes: The speed of the ramp vehicle is adjusted to be close to the speed of the designated mainline vehicle, and the position of each vehicle at the moment when the ramp vehicle speed adjustment is completed is calculated. If the positions of the ramp vehicle and the vehicle in front of the gap both meet the safe merging condition, the ramp vehicle can safely merge into the safe gap. The safe merging condition expression is as follows: X V2 (t1)≤X end X V2 (t1)>X V3 (t1)+L Among them, t1 is the time when the ramp vehicle speed adjustment ends; X V1 (t1) is the position of the vehicle V1 in front of the gap at time t1; X V2 (t1) is the position of ramp vehicle V2 at time t1; X V3 (t1) is the position of the vehicle V3 behind the gap at time t1; X end The end point of the acceleration lane.

4. The vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment according to claim 1 is characterized in that: The step also includes adjusting the gap when there is no safety gap on the main line or the ramp vehicle cannot safely merge into the safety gap, specifically including: If there is no safety gap on the main line, or the ramp vehicle cannot merge safely into the safety gap, the speed of the main line vehicle corresponding to the ramp vehicle is adjusted, including: the vehicle in front of the gap maintains a constant speed and the vehicle behind the gap decelerates, or the vehicle in front of the gap accelerates and the vehicle behind the gap maintains a constant speed, or the vehicle in front of the gap accelerates and the vehicle behind the gap decelerates; If the mainline vehicle meets the specified conditions after speed adjustment, it is further determined whether there is a safety gap in the mainline and the ramp vehicle can safely merge into the safety gap. The specified condition expression is as follows: 0<t ad <t c1 V V1 (t ad )≥V V3 (t ad ) Among them, t ad is the gap adjustment time; t c1 The maximum time for the ramp vehicle to accelerate; X V1 (t ad ) is the gap between the front vehicle V1 and the front vehicle V1 at t ad Position after seconds; X V3 (t ad ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t ad Position after seconds; V V1 (t ad ) is the gap between the front vehicle V1 and the front vehicle V1 at t ad The speed of the vehicle after seconds; V V3 (t ad ) is the gap between the rear vehicle V3 and the rear vehicle V3 at t ad The speed of the vehicle after seconds.

5. The vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment according to claim 1, characterized in that: The calculation formula for the position of each vehicle when the ramp vehicle enters the acceleration lane is as follows: X V2 (t2)=X start X V1 (t2)=X V1 (t1)+V V1 (t1)×t2 X V3 (t2)=X V3 (t1)+V V3 (t1)×t2 Wherein, t2 is the time taken by ramp vehicle V2 to move to the starting point of the acceleration lane after the speed adjustment is completed; V1 (t2), X V3 (t2) are the positions of the gap front vehicle V1 and the gap rear vehicle V3 when the ramp vehicle V2 drives to the acceleration lane; V2 (t2) is the position of the ramp vehicle V2 when it drives to the acceleration lane; t1 is the moment when the vehicle state adjustment is completed; X V1 (t1) is the position of the vehicle V1 in front of the gap at time t1; X V2 (t1) is the position of ramp vehicle V2 at time t1; X V3 (t1) is the position of the vehicle V3 behind the gap at time t1; V V1 (t1) is the speed of the vehicle V1 in front of the gap after time t1; V V2 (t1) is the speed of ramp vehicle V2 after time t1; V V3 (t1) is the speed of the vehicle V3 behind the gap after time t1; X start The starting point of the acceleration lane.

6. The vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment according to claim 1, characterized in that: When sampling the merging starting point and merging end point according to the position of the ramp vehicle when entering the acceleration lane, it includes: sampling at equal intervals between the position of the ramp vehicle when entering the acceleration lane and the end point of the acceleration lane to obtain the sampling points of the merging starting point, and then sampling the merging end point for each merging starting point. The calculation formula is as follows: in, is the position of each merging starting point; S1 is the sampling interval of the merging starting point; t2 is the time taken by the ramp vehicle V2 to move to the starting point of the acceleration lane after the speed adjustment is completed; X V2 (t2) is the position of ramp vehicle V2 when it drives to the acceleration lane, X end The end of the acceleration lane; is the position of each confluence end point; S2 is the sampling interval of the confluence end point; S ′ To ensure the distance the vehicle moves forward during the lane change process; S is the maximum longitudinal movement distance calculated based on the speed of the ramp vehicle V2 and the maximum allowable acceleration.

7. The vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment according to claim 1 is characterized in that: When calculating the collision relationship between the front vehicle in the gap, the rear vehicle in the gap, and the end of the acceleration lane during the ramp vehicle merging process, the collision relationship between the ramp vehicle and the rear vehicle in the gap, the collision relationship between the ramp vehicle and the front vehicle in the gap, and the collision relationship between the ramp vehicle and the end of the acceleration lane are calculated based on the rectangular model and the col function, where: The collision relationship between the ramp vehicle and the vehicle behind in the gap is as follows: Where τ is the duration of inflow; X V2 (t), Y V2 (t) are the vertex horizontal and vertical coordinates of ramp vehicle V2, X V2a (t), X V2b (t), X V2c (t), X V2d (t) are the horizontal coordinates of the four vertices of the ramp vehicle V2, Y V2a (t), Y V2b (t), Y V2c (t), Y V2d (t) are the vertical coordinates of the four vertices of the ramp vehicle V2; V3 (t), Y V3 (t) are the horizontal and vertical coordinate sets of the vertices of the vehicle V3 behind the gap, X V3a (t), X V3b (t), X V3c (t), X V3d (t) are the horizontal coordinates of the four vertices of the vehicle V3 behind the gap, Y V3a (t), Y V3b (t), Y V3c (t), Y V3d (t) are the vertical coordinates of the four vertices of the vehicle V3 behind the gap; The collision relationship between the ramp vehicle and the gap front vehicle is as follows: Among them, X V1 (t), Y V1 (t) The horizontal and vertical coordinates of the vertex of the front vehicle V1, respectively, V1a (t), X V1b (t), x V1c (t), X V1d (t) are the horizontal coordinates of the four vertices of the gap front vehicle V1, Y V1a (t), Y V1b (t), Y V1c (t), Y v1d (t) are the vertical coordinates of the four vertices of the vehicle V1 in front of the gap; The collision relationship between the ramp vehicle and the end of the acceleration lane is as follows: Among them, X p , Y p are the horizontal and vertical coordinate sets of the two endpoints of the end segment of the acceleration lane, respectively. p1 , X p2 are the horizontal coordinates of the two endpoints of the end segment of the acceleration lane, Y p1 , Y p2 They are the ordinates of the two endpoints of the end segment of the acceleration lane.

8. The vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment according to claim 1, characterized in that: The constraint condition calculation formula is as follows: v min ≤v p (t)≤v max |a x (t)|<min{a xmax ,μg} k p (t)≤k max TTC i (t)≥TTC safe or TTC i (t)≤0 Among them, v p (t) is the velocity corresponding to each discrete point on the trajectory; v max is the maximum speed limit; v min is the minimum speed limit; a x (t) is the longitudinal acceleration of each discrete point on the trajectory; a y (t) is the lateral acceleration of each discrete point on the trajectory; a xmax is the maximum longitudinal acceleration limit; a ymax is the maximum lateral acceleration limit; μ is the road adhesion coefficient; g is the gravitational acceleration; k p (t) is the curvature of each discrete point; k max is the maximum curvature limit; x(t e ) is the target longitudinal position of the vehicle; y(t e ) is the target lateral position of the vehicle; is the initial longitudinal velocity of the vehicle; TTC safe is the minimum safe TTC value; TTC1(t) is the collision time between the ramp vehicle V2 and the gap rear vehicle V3; TTC2(t) is the collision time between the ramp vehicle V2 and the gap front vehicle V1; TTC3(t) is the collision time between the ramp vehicle V2 and the end of the acceleration lane; X V1 (t), X V3 (t) is the position of the gap front vehicle V1 and the gap rear vehicle V3 at time t; X V2 (t) is the position of ramp vehicle V2 at time t; V V1 (t), V V2 (t), V V3 (t) are the speeds of the gap front vehicle V1, ramp vehicle V2, and gap rear vehicle V3 at time t; X end The end of the acceleration lane.

9. The vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment according to claim 1, characterized in that: The specific formula of the multi-objective optimization function is as follows: J c =k d J d +k s J s In the formula, J u is the merging urgency objective function of the trajectory with merging starting point i as the merging starting point; L0 is the length of the acceleration lane; L si J is the distance from the merging starting point i to the end of the acceleration lane; safe is the safety equilibrium objective function; TTC1(t) is the collision time between the ramp vehicle V2 and the gap rear vehicle V3; TTC2(t) is the collision time between the ramp vehicle V2 and the gap front vehicle V1; TTC3(t) is the collision time between the ramp vehicle V2 and the end of the acceleration lane; J c is the comfort objective function; τ is the duration of inflow; J d , J s are the longitudinal and lateral comfort weighting items respectively; k d , k s is the weight coefficient; are the longitudinal and lateral impacts of the vehicle respectively; J k is the smoothness objective function; k p (t) is the curvature of each discrete point on the trajectory; k pmax is the maximum curvature among all trajectory curves.

10. The vehicle merging trajectory planning method for ramp merging area considering multi-objective optimization in a pure network environment according to claim 1, characterized in that: When establishing a multi-objective optimization model for the input trajectory according to the constraint conditions and the multi-objective optimization function, it includes: The constraint conditions are used as the constraint conditions of the multi-objective optimization model of the imported trajectory. After normalizing each objective function of the multi-objective optimization function, the objective function of the multi-objective optimization model of the imported trajectory is obtained. The expression of the multi-objective optimization model of the imported trajectory is as follows: Among them, J u is the objective function of the inflow urgency of the trajectory with inflow starting point i as the inflow starting point; J u,min and J u,max are the maximum and minimum values ​​of the input urgency objective function respectively; J safe is the security equilibrium objective function; J safe,min and J safe,max are the maximum and minimum values ​​of the security equilibrium objective function respectively; J c is the comfort objective function; J c,min and J c,max are the maximum and minimum values ​​of the comfort objective function respectively; J k is the smoothness objective function; J k,min and J k,max are the maximum and minimum values ​​of the smoothness objective function respectively; ω1, ω2, ω3, ω4 are the weights of each objective function, and ω1+ω2+ω3+ω4=1; v p (t) is the velocity corresponding to each discrete point on the trajectory; v max is the maximum speed limit; v min is the minimum speed limit; a x (t) is the longitudinal acceleration of each discrete point on the trajectory; a y (t) is the lateral acceleration of each discrete point on the trajectory; a xmax is the maximum longitudinal acceleration limit; a ymax is the maximum lateral acceleration limit; μ is the road adhesion coefficient; g is the gravitational acceleration; k p (t) is the curvature of each discrete point; k max is the maximum curvature limit; x(t e ) is the target longitudinal position of the vehicle; y(t e ) is the target lateral position of the vehicle; is the initial longitudinal velocity of the vehicle.

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