CN114495556A - Method for setting optimal formation length for automatic driving under constraint of ramp spacing of expressway - Google Patents
Method for setting optimal formation length for automatic driving under constraint of ramp spacing of expressway Download PDFInfo
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Abstract
The invention relates to a method for setting the optimal formation length for automatic driving under the constraint of ramp spacing of a highway, which comprises the following steps: s1, obtaining the distance L between the ramp a and the ramp b of the expressway, and the running state parameters of the automatic driving traffic flow of the main line at the upstream of the ramp a, including the number n of the vehicles in the prior formation1The existing formation stable running speed
S2, simulating the marshalling and ungrouping process between the on-ramp vehicle and the existing formation vehicle through computer simulation; s3, selecting the shortest stable running time t of vehicle formation1(ii) a S4, limiting L according to the ramp distance and limiting t according to the shortest stable operation time length1Calculating the maximum number n of vehicles to be combined2And obtaining the optimal formation length of the automatic driving traffic flow running on the highway. The invention has guarantee effectSimple and convenient rate and calculation, energy consumption saving, safety, reliability and the like.
Description
Technical Field
The invention relates to the technical field of traffic control systems of road vehicles, in particular to a method for setting the optimal formation length of automatic driving under the constraint of ramp spacing of a highway.
Background
The automatic driving vehicle fleet grouping technology is characterized in that vehicle-to-vehicle cooperative communication or vehicle-to-road cooperative communication is utilized in the driving process of automatic driving vehicle flows, so that the distance between vehicle heads of the automatic driving vehicle flows is reduced, the driving speed is kept consistent, and limited road resources can be better utilized.
However, in the process of grouping, as the length of a vehicle fleet increases, the overall driving safety is reduced, and the fluctuation of grouping is increased, so that the automatic driving traffic grouping has an optimal grouping length in consideration of the influence of various factors on the grouping process.
Taking an expressway environment as an example, since vehicles may enter and exit through ramps on an expressway, assuming that the entering vehicles will exit on the next ramp, and a train of vehicles on the expressway is still running, the entering vehicles on the ramps need to consider whether to join the train according to various limiting conditions, such as running distance, stable running time, and the like.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for setting the optimal formation length for automatic driving under the constraint of the ramp distance of the expressway, which has the advantages of efficiency guarantee, simple and convenient calculation, energy consumption saving, safety and reliability.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method for setting the optimal formation length for automatic driving under the restriction of the ramp spacing of a highway is constructed, and comprises the following steps:
s1, obtaining the distance L between the ramp a and the ramp b of the expressway, and the running state parameters of the automatic driving traffic flow of the main line at the upstream of the ramp a, including the number n of the vehicles in the prior formation1The existing formation stable running speed v-;
s2, simulating the marshalling and ungrouping process between the on-ramp vehicle and the existing formation vehicle through computer simulation;
s3, selecting the shortest stable running time t of vehicle formation1；
S4, limiting L according to the ramp distance and performing shortest stable operationLine duration limit t1Calculating the maximum number n of vehicles to be combined2And obtaining the optimal formation length of the automatic driving traffic flow running on the highway.
According to the above scheme, the core method in the simulation process in step S2 is:
s201, separately controlling the longitudinal and transverse distances between vehicles, and respectively controlling the transverse distance between the vehicles to be coordinated to 0 and the longitudinal distance to be coordinated to an ideal distance;
s202, establishing an attraction and repulsion model between vehicles, avoiding collision in the process of carrying out cooperation, and establishing an attraction-repulsion function;
and S203, generating a vehicle formation.
According to the above scheme, the attraction-repulsion function established in step S202 is:
three adjacent vehicles respectively form three different longitudinal acting forces according to respective longitudinal intervals
Gradually adjusting the motion of the vehicles by the longitudinal force to coordinate the longitudinal spacing between the vehicles to be consistent, wherein the attraction-repulsion function of the longitudinal spacing between the vehicles is as follows:
in the formula: the polyfit function is a self-defined S-shaped function when h is1Close to 0, the value is 1, at h1The value is 0 near r; h is1The ratio of the longitudinal distance between the vehicles after the function transformation and the ideal distance after the function transformation is obtained; r is a constant;
three adjacent vehicles are subjected to different transverse forces
By gradually adjusting the transverse movement of the vehicle by the transverse force, the transverse position of the vehicle is coordinated to the center line of the lane, and the suction-discharge of the transverse interval is establishedThe function of repulsion is,
in the formula: h is2Is the value of the transverse distance between the vehicles after the functional transformation; r is2Is a constant.
According to the scheme, the step of generating the vehicle formation in the step S203 comprises the following steps:
s20301, inputting the number n of the vehicles in the formation1Randomly generating the position and speed of the initial vehicle, wherein the position of the initial randomly generated vehicle is within the designated area size, and avoiding too close proximity between the vehicles;
s20302, giving the state of the virtual leader: when the vertical coordinate of the virtual leader is generated, the vertical coordinate is consistent with the size, the horizontal coordinate is the position of the center line of the lane, then the formation stable running speed v-is given to the virtual leader, and the motion acceleration of the virtual leader is as follows:
controlling acceleration to [ -5,3]m/s2Within a, and aleaderIs subjected to vleaderThe feedback effect of (2).
According to the scheme, the specific steps of the step S4 are as follows:
s401, setting the number n of vehicles in the vehicle group on the ramp2An initial value of (1);
s402, calculating the distance L when the two fleets complete the cooperation and reach the stability1Carrying out envelope fitting on the speed change in the fluctuation process by utilizing the right part of the log-normal distribution curve, and considering that the stable state is achieved when the distance between envelope lines is less than 0.3m/s of a threshold value;
the formula inserted into the right-hand curve of log-normal distribution is:
in the formula: a. b and c are parameters to be solved, and when x is equal to ebWhen f (x) takes a peak value, so when x ≧ ebThen the right curve of the lognormal distribution can be taken;
s403, calculating the running distance L under the stable running time2Wherein
S404, calculating the running distance L in the process of fleet decomposition and compilation3The completion of the solution editing means that the speed difference of the vehicles in two different fleets is within 0.3m/s, the distance difference between the vehicle heads is within 0.3m, and the absolute value of the acceleration difference is within 0.1m/s2Within, L3The calculation of (2) is from the time of starting the decompiling to the time of finishing the decompiling;
s405, judging L1+L2+L3Whether the length limit L is exceeded;
s406, increasing n by taking '1' as a step length when the number of the N-numbered blocks is not reached2；
S407, repeating the step S406 until the last n is obtained2At this time n1+n2Namely the optimal formation length of the automatic driving traffic flow under the restriction of the ramp distance of the expressway.
According to the scheme, the ramp of the expressway comprises an expressway lane, a ramp entrance of the expressway and a ramp exit of the expressway.
According to the scheme, the shortest stable running time t of the vehicle formation is selected in the step S31Was 1 minute.
According to the above scheme, the step S4 further includes the following steps: the horizontal axis of the plane coordinate system is taken as time, the vertical axis of the plane coordinate system is taken as travel distance, and the number n of different vehicles is plotted2The lower curve cluster.
The method for setting the optimal formation length for automatic driving under the constraint of the ramp spacing of the expressway has the following beneficial effects:
the invention provides a method for setting the optimal formation length of automatic driving under the constraint of the ramp spacing of a highway, which is characterized in that the initial running state of the existing motorcade is obtained, the displacement in the processes of regrouping, stable running and decompiling is respectively calculated, and the number of vehicles which are imported on the ramp is adjusted through feedback, so that the optimal formation length of an automatic driving traffic flow is obtained, the overall thought is simpler, and the complex mathematical calculation is avoided.
Drawings
FIG. 1 is a schematic diagram of vehicle force analysis during the grouping and compiling process of the present invention;
FIG. 2 is a schematic diagram of an automatic driving traffic stream formation process on a ramp of a highway according to the invention, which is a formation initial process;
FIG. 3 is a schematic diagram of a regrouping process of an automatic driving traffic stream formation process on a ramp of a highway according to the present invention;
FIG. 4 is a schematic illustration of a steady driving process of an autonomous driving traffic stream formation process on a freeway ramp according to the present invention;
FIG. 5 is a schematic diagram of the de-compilation process of the formation process of the autonomous driving traffic on the ramp of the expressway in the present invention;
FIG. 6 is a functional image of the polipit function of the present invention;
FIG. 7 shows n in the present invention2When the value is 4, judging the stability by using a logarithmic normal envelope curve;
FIG. 8 shows the difference n in the present invention2A corresponding driving curve;
FIG. 9 is a flow chart of the method of the present invention.
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
As shown in fig. 9, the method for determining the optimal formation length of the autonomous driving traffic flow under the restriction of the ramp distance of the expressway of the invention comprises the following steps:
s1, obtaining the distance L between the ramp a and the ramp b of the expressway and the running state parameters of the automatic driving traffic flow of the main line at the upstream of the ramp a, including the number n of the vehicles in the prior formation1The existing formation is stableConstant running speed
As shown in fig. 2, the expressway ramp includes an expressway lane, a ramp entrance of the expressway, and a ramp exit of the expressway;
s2, simulating the process of marshalling and ungrouping between the vehicles on the ramp and the existing formation vehicles by means of computer simulation, wherein the core method in the simulation process is as follows:
s201, separately controlling the longitudinal and transverse distances between vehicles, and respectively controlling the transverse distance between the vehicles to be coordinated to 0 and the longitudinal distance to be coordinated to an ideal distance;
s202, an attraction and repulsion model between vehicles needs to be established, collision and other situations in the process of cooperation are avoided, the longitudinal distance needs to be coordinated to an ideal distance, and therefore an attraction-repulsion function as in the formula (2-1) is established, when the longitudinal distance between the vehicles is shorter, the generated impedance is larger, collision between the vehicles is avoided, when the distance is moderate, attraction between the vehicles is generated, and when the distance is larger, the vehicles cannot be influenced mutually. As shown in FIG. 1, when the longitudinal distances between the vehicles are not coordinated to be consistent, different longitudinal forces are generated between the vehicles according to the longitudinal distances, and three vehicles respectively generate three different longitudinal forces according to the respective longitudinal distances
The movement of the vehicles is gradually adjusted by the longitudinal force, so that the longitudinal spacing between the vehicles is coordinated to be uniform. The attraction-repulsion function for the longitudinal spacing between the vehicles at this time is:
in the formula: the polyfit function is a self-defined S-shaped function when h is1Close to 0 the value is 1, at h1This value is 0 near r, see FIG. 3; h is1For longitudinal spacing between vehicles by functional transformationThe ratio of the ideal spacing after functional transformation; r is a constant;
when the vehicle initially moves, the transverse positions on the lane are not all on the lane central line, as shown in fig. 1, in order to form a complete cooperative queue, the transverse distance of the vehicle needs to be coordinated to 0, namely, the vehicle keeps running at the lane central line position, when the vehicle is far away from the lane central line, the vehicle is influenced by the transverse acting force to be close to the lane central line, and in fig. 1, three vehicles are influenced by different transverse acting forces
Gradually adjusting the transverse movement of the vehicle by the transverse acting force, so that the transverse position of the vehicle is coordinated to the central line of the lane. Therefore, as shown in equation (2-2), the attraction-repulsion function for establishing the lateral distance is such that when the lateral distances between the vehicles are very close, the vehicles do not affect each other, and when the lateral distance is larger in a certain range, the attraction generated is larger, thereby accelerating the cooperation between the vehicles. The transverse spacing of the vehicle is maintained to fluctuate within a small range by the model, and the transverse spacing can be approximately considered to be coordinated to be consistent.
In the formula: h is2Is the value of the transverse distance between the vehicles after the functional transformation; r is2Is a constant.
Since the adjustment target of the lateral distance between the vehicles is 0, unlike the longitudinal distance, it is necessary to change the lateral speed feedback coefficient and the lateral position feedback coefficient between the vehicles, but the larger the coefficient is, the better, but the smaller the coefficient is, the speed of lateral convergence can be made faster.
S203, generating a vehicle formation;
the concrete steps for generating the formation are as follows:
s20301, inputting the number n of the vehicles in the formation1Randomly generating the position and velocity of the initial vehicleWherein the location of the initial randomly generated vehicles needs to be within the specified zone size and avoid too close proximity between vehicles;
s20302, giving the state of the virtual leader: the vertical coordinate of the virtual leader is consistent with the size when being generated, the horizontal coordinate is the position of the center line of the lane, and then the formation is carried out at a stable running speed
And assigning to the virtual leader, wherein the motion acceleration of the virtual leader is as follows:
controlling acceleration to [ -5,3]m/s2Within a, and aleaderIs subjected to vleaderThe feedback effect of (2).
S3, selecting the shortest stable running time t of vehicle formation1Selecting the shortest stable operation time t1Is 1 minute;
s4, limiting L according to the ramp distance and limiting t according to the shortest stable operation time length1Calculating the maximum number n of vehicles capable of being combined2Thereby obtaining the optimal formation length of the automatic driving traffic flow running on the expressway. The method comprises the following specific steps:
s401, setting the number n of vehicles in the vehicle group on the ramp2An initial value of (1);
s402, calculating the distance L when the two fleets complete the cooperation and reach the stability1As shown in fig. 3. The present invention defines "steady state" as: the speed difference between the vehicles is within 0.3m/s, the distance difference between the vehicle heads is within 0.3m, and the absolute value difference of the acceleration is within 0.1m/s2Within. Because the cooperative motion process of the vehicle is a fluctuating process, the right part of the lognormal distribution curve is used for carrying out envelope fitting on the speed change in the fluctuating process, and when the distance between envelope lines is less than a threshold value of 0.3m/s, the stable state is considered to be achieved, as shown in fig. 7;
the formula inserted into the right-hand curve of log-normal distribution is:
in the formula: a. b and c are parameters to be solved, and when x is equal to ebWhen f (x) takes a peak value, so when x ≧ ebThe right curve of the log normal distribution can be taken.
S403, calculating the running distance L under the stable running time2As shown in FIG. 4, wherein
S404, calculating the running distance L in the process of fleet decomposition and compilation3As shown in FIG. 5, the completion of the de-compilation means that the speed difference of each vehicle in two different fleets is within 0.3m/s, the distance difference between the vehicle heads is within 0.3m, and the absolute value of the acceleration difference is within 0.1m/s2Within, L3The calculation of (2) is from the time of starting the decompilation to the time of completing the decompilation.
S405, judging L1+L2+L3Whether the length limit L is exceeded;
s406, increasing n by taking '1' as a step length when the number of the N-numbered blocks is not reached2；
S407, repeating the step S6 until the last n is obtained2At this time n1+n2The optimal formation length of the automatic driving traffic flow under the restriction of the ramp distance of the expressway is obtained;
s408, drawing the number n of different vehicles by taking time as the horizontal axis of the plane coordinate system and taking the running distance as the vertical axis of the plane coordinate system2Lower cluster of curves, as shown in fig. 8.
In a preferred embodiment of the present invention, the method comprises the following steps:
s1, obtaining the running state parameters of the automatic driving traffic flow running on the highway, including the number n of the existing formation vehicles1Current formation stable driving speed of 5 ═ 5
Setting the length L of the entrance and exit of the ramp of the expressway to be 3 km;
s2, forming the existing automatic driving fleet by a computer simulation method;
the step S2 specifically includes the following steps:
s201: and (3) performing separate control on the longitudinal and transverse distances between the vehicles, and respectively controlling the transverse distance between the vehicles to be coordinated to 0 and the longitudinal distance to be coordinated to an ideal distance.
S202: an attraction and repulsion model between vehicles needs to be established to avoid the situations of collision and the like in the cooperative process, because the longitudinal distance needs to be coordinated to the ideal distance, an attraction-repulsion function of the following formula 2-1 is established, when the longitudinal distance between the vehicles is shorter, the generated impedance is larger, so that the collision between the vehicles is avoided, when the distance is moderate, the attraction between the vehicles is generated, and when the distance is larger, the vehicles cannot be influenced mutually. The attractive-repulsive function for the longitudinal spacing between vehicles is:
in the formula: the polyfit function is a self-defined S-shaped function when h is1Close to 0 the value is 1, at h1This value is 0 near r, as shown in FIG. 2; h is1The ratio of the longitudinal distance between the vehicles after the function transformation and the ideal distance after the function transformation is obtained; r is constant, and r is 0.9.
When the vehicle initially moves, the transverse positions on the lane are not all on the lane center line, and in order to form a complete cooperative queue, the vehicle needs to be coordinated to have a transverse distance of 0, namely the vehicle keeps running at the lane center line position. Therefore, as shown in equation 2-2, the attraction-repulsion function for establishing the lateral distance is such that when the lateral distances between the vehicles are very close, the vehicles do not affect each other, and when the lateral distance is larger in a certain range, the attraction generated is larger, thereby accelerating the cooperation between the vehicles. The transverse spacing of the vehicle is maintained to fluctuate within a small range by the model, and the transverse spacing can be approximately considered to be coordinated to be consistent.
In the formula: h is a total of2Is the value of the transverse distance between the vehicles after the functional transformation; r is2Take 0.01.
Since the adjustment target of the lateral distance between the vehicles is 0, unlike the longitudinal distance, the speed feedback coefficient and the position feedback coefficient between the vehicles need to be changed, but the speed of longitudinal convergence can be increased by making the coefficient smaller rather than the larger the better the coefficient is.
S203, generating a vehicle formation;
the concrete steps for generating the formation are as follows:
s20301, inputting the number n of the vehicles in the formation1Randomly generating the position and speed of the initial vehicle, wherein the position of the initial randomly generated vehicle needs to be 100 × 100m at a specified area size2And avoid too close proximity between vehicles;
s20301, given the state of the virtual leader: the vertical coordinate of the virtual leader is consistent with the size when being generated, the horizontal coordinate is the position of the center line of the lane, and then the formation is carried out at a stable running speed
And assigning to the virtual leader, wherein the motion acceleration of the virtual leader is as follows:
the acceleration is controlled to be [ -5,3 ] by the formula]m/s2Within a, and aleaderIs subjected to vleaderThe feedback effect of (2).
S3, selecting the shortest stable operation time length t1＝60s；
S4, according toRamp spacing constraint limit L and shortest stable operation duration limit t1The number n of vehicles which can be combined is calculated2Thereby obtaining the optimal formation length of the automatic driving traffic flow running on the expressway.
The step S4 specifically includes the following steps:
s401, setting the number n of vehicles in the vehicle group on the ramp2Initial value of 2;
s402, calculating the distance L when the two fleets complete the cooperation and reach the stability1The definition of the invention is stable, namely that the speed difference between vehicles is within 0.3m/s, the distance difference between the vehicle heads is within 0.3m, and the absolute value difference of the acceleration is within 0.1m/s2The vehicle cooperative motion process is a fluctuating process, the right part of envelope lines of the log-normal distribution are used for fitting the speed change in the fluctuating process, and when the space between the envelope lines meets the requirement, the stable state is considered to be achieved;
the formula inserted into the right-hand curve of log-normal distribution is:
in the formula: a. b and c are parameters to be solved, and when x is more than or equal to ebThe right curve of the log normal distribution can be taken. The solving of the parameters is carried out by data fitting, and corresponding parameters can be obtained by carrying out data fitting on the maximum value in the speed fluctuation process.
S403, calculating the running distance L under the stable running time2Wherein
S404, calculating the running distance L in the process of fleet decomposition and compilation3The completion of the solution editing means that the speed difference of the vehicles in two different fleets is within 0.3m/s, the distance difference of the vehicle heads is within 0.3m, and the absolute value of the acceleration difference is within 0.1m/s2Within, L3Is de-compiled from the beginningUntil the decompilation is completed.
S405, judging L1+L2+L3Whether the length limit L is exceeded;
s406, increasing n by taking '1' as a step length when the number of the N-numbered blocks is not reached2；
S407, repeating the step S406 until the last n is obtained2When n is equal to 31+n2And 8, the optimal formation length of the automatic driving traffic flow considering the expressway ramp is obtained.
S408, drawing the number n of different vehicles by taking time (iteration times) as a horizontal axis of a plane coordinate system and taking the running distance as a vertical axis of the plane coordinate system2The lower curve cluster.
In the invention, fig. 1 is a vehicle stress analysis diagram in the marshalling and the un-marshalling process, when the longitudinal and transverse distances of the vehicle are not coordinated to be consistent, the influence of the longitudinal and transverse acting force is received, and finally the transverse distance is coordinated to be 0, and the longitudinal distance is coordinated to be an ideal distance. FIG. 5 shows the difference n in the present invention2Corresponding driving curve when n2When the running distance of the whole re-grouping and de-compiling process does not reach the ramp spacing constraint limit, the grouping is not sufficient; when n is2When the distance between the whole re-grouping and the de-grouping process is 3, the running distance almost reaches the ramp spacing constraint limit, and the grouping length reaches the limit; when n is2The total distance traveled for the entire regrouping and decompiling process has exceeded the ramp spacing constraint at 4, at which time the consist length has exceeded the limit.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (8)
1. A method for setting the optimal formation length for automatic driving under the restriction of the ramp distance of a highway is characterized by comprising the following steps:
s1, obtaining the distance L between the ramp a and the ramp b of the expressway, and the running state parameters of the automatic driving traffic flow of the main line at the upstream of the ramp a, wherein the running state parameters comprise the number n of the vehicles in the prior formation1The existing formation stable running speed
S2, simulating the marshalling and ungrouping process between the on-ramp vehicle and the existing formation vehicle through computer simulation;
s3, selecting the shortest stable running time t of vehicle formation1；
S4, limiting L according to the ramp distance and limiting t according to the shortest stable operation time length1Calculating the maximum number n of vehicles to be combined2And obtaining the optimal formation length of the automatic driving traffic flow running on the highway.
2. The method for setting the optimal formation length for automatic driving under the constraint of the ramp distance of the expressway according to claim 1, wherein the core method in the simulation process in the step S2 is as follows:
s201, separately controlling the longitudinal and transverse distances between vehicles, and respectively controlling the transverse distance between the vehicles to be coordinated to 0 and the longitudinal distance to be coordinated to an ideal distance;
s202, establishing an attraction and repulsion model between vehicles, avoiding collision in the process of carrying out cooperation, and establishing an attraction-repulsion function;
and S203, generating a vehicle formation.
3. The method for setting the optimal formation length for automatic driving under the constraint of the ramp distance of the expressway according to claim 2, wherein the attraction-repulsion function established in the step S202 is as follows:
three adjacent vehicles respectively form three different longitudinal acting forces according to respective longitudinal intervals
Gradually adjusting the motion of the vehicles by longitudinal force to coordinate the longitudinal spacing between the vehicles to be consistent, wherein the attraction-repulsion function of the longitudinal spacing between the vehicles is as follows:
in the formula: the polyfit function is a self-defined S-shaped function when h is1Close to 0 the value is 1, at h1The value is 0 near r; h is1The ratio of the longitudinal distance between the vehicles after the function transformation and the ideal distance after the function transformation is obtained; r is a constant;
three adjacent vehicles are subjected to different transverse forces
The transverse movement of the vehicle is gradually adjusted through the transverse acting force, so that the transverse position of the vehicle is coordinated to the central line of the lane, an attraction-repulsion function of the transverse distance is established,
in the formula: h is2Is the value of the transverse distance between the vehicles after the functional transformation; r is2Is a constant.
4. The method for setting the optimal formation length for automatic driving under the constraint of the ramp distance of the expressway according to claim 2, wherein the step S203 for generating the vehicle formation comprises the steps of:
s20301, inputting the number n of the vehicles in the formation1Randomly generating the position and speed of the initial vehicle, wherein the position of the initial randomly generated vehicle is within a specified zone size to avoid excessive proximity between the vehicles;
s20302, giving the state of the virtual leader: maintaining with size while generating the vertical coordinate of the virtual leaderThe transverse coordinate is the position of the center line of the lane, and then the formation is carried out to stabilize the driving speed
And assigning to the virtual leader, wherein the motion acceleration of the virtual leader is as follows:
controlling acceleration to [ -5,3]m/s2Therein, a is aleaderIs subjected to vleaderThe feedback effect of (c).
5. The method for setting the optimal formation length for automatic driving under the constraint of the ramp distance of the expressway according to claim 1, wherein the specific steps of the step S4 are as follows:
s401, setting the number n of vehicles in the vehicle group on the ramp2An initial value of (1);
s402, calculating the distance L when the two fleets complete the cooperation and reach the stability1Enveloping and fitting the speed change in the fluctuation process by utilizing the right part of the log-normal distribution curve, and considering that the stable state is achieved when the distance between the enveloping lines is less than 0.3 m/s;
the formula inserted into the right-hand curve of log-normal distribution is:
in the formula: a. b and c are parameters to be solved, and when x is equal to ebWhen f (x) takes a peak value, so when x ≧ ebThen the right curve of the lognormal distribution can be taken;
s403, calculating the running distance L under the stable running time2Wherein
S404, calculating the running distance L in the process of fleet decomposition and compilation3The completion of the solution editing means that the speed difference of the vehicles in two different fleets is within 0.3m/s, the distance difference between the vehicle heads is within 0.3m, and the absolute value of the acceleration difference is within 0.1m/s2Interior, L3The calculation of (2) is from the time of starting the decompiling to the time of finishing the decompiling;
s405, judging L1+L2+L3Whether the length limit L is exceeded;
s406, increasing n by taking '1' as a step length when the number of the N-numbered blocks is not reached2；
S407, repeating the step S406 until the last n is obtained2At this time n1+n2Namely the optimal formation length of the automatic driving traffic flow under the restriction of the ramp distance of the expressway.
6. The method for setting the optimal formation length for autopilot under the restriction of the inter-ramp distance of the expressway according to claim 1, wherein the expressway inter-ramp comprises an expressway lane, an expressway inter-ramp entrance, and an expressway inter-ramp exit.
7. The method for setting the optimal formation length for automatic driving under the constraint of the ramp distance of the expressway of claim 1, wherein the time length t for the shortest stable operation of the formation of vehicles is selected in the step S31Was 1 minute.
8. The method for setting the optimal formation length under the restriction of the ramp distance of the expressway of claim 1, wherein the step S4 further comprises the following steps: the horizontal axis of the plane coordinate system is taken as time, the vertical axis of the plane coordinate system is taken as travel distance, and the number n of different vehicles is plotted2The lower curve cluster.
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