Detailed Description
Fig. 1 is a schematic diagram of eight lanes of traffic flow of a conventional intersection (note: the intersection is the simplest traffic flow model), and the concept in an operating system is used, and the intersection is a critical resource, that is, the intersection is used with mutual exclusivity, that is, only non-intersecting traffic flows are allowed to pass through at the same time. Mutual exclusivity and conflict existing between traffic flows are revealed as shown in fig. 2. Road junction
With flow of traffic f
x、f
yIf f is
xAnd f
yAnd if the intersection track is crossed, the conflict is recorded as: f. of
x∝f
y. Conversely, the relationship between traffic flows where trajectories do not intersect is called a parallel relationship, and is noted as:
The crossroad shown in FIG. 1 is denoted as crossroad
Is provided with
For traffic flow at intersections, i.e. complete set
Representing traffic flow x
iCan be connected with the traffic flow x at a certain intersection
iSet of all traffic flows in parallel.
Indicating the size of the corpus of traffic flow, in the present invention,
the traffic signal plays a role in coordinating orderly and safe use of intersections by a plurality of traffic flows. The purpose of time-sharing multiplexing of a plurality of traffic flows at an intersection can not be realized without traffic signals. However, the introduction of traffic signals introduces a loss of vehicle throughput, which is analyzed below.
To illustrate the problem more clearly, the intersection shown in fig. 1 is simplified to a one-way 1-lane intersection shown in fig. 3.
As shown in FIG. 3, C.Z is a Critical Zone (Critical Zone), f1And f2Is a pair of mutually exclusive traffic flows. Although, the traffic flow is difficult to be described by a mathematical model due to the high randomness, and quantitative calculation is achieved. However, the following quantitative calculation may be made. And setting the maximum speed of the traffic flow as v, the acceleration as a and the traffic flow density d. Analysis reveals that, for a certain traffic flow, for example, f1Traffic signal (i.e. pass signal)Green signal) time period, C.Z, the density and speed of traffic and the current traffic flow f1The same; stop-traffic (i.e. red signal) period, C.Z, where traffic density and speed are correlated with another flow of traffic f2Similarly, the throughput of the entire interface is not affected. However, in the signal switching (i.e., yellow signal) period, the traffic flow f1With the acceleration a decelerated to 0, the vehicle in region C.Z became empty, f gradually accelerated to the highest speed v, and normal vehicle density was restored in region C.Z.
Therefore, the vehicle passage loss caused by this switching process is at least: 2 v/ad.
Example 1
Fig. 6 shows a traffic flow control method for an intersection according to the present invention, which comprises the following steps,
step 1, numbering eight traffic flows in a crossroad in sequence, selecting any one traffic flow as a main flow for traffic control, calculating the numbers of three branch flows which can run in parallel with the main flow according to the numbers of the main flow and through a formula (1), a formula (2) and a formula (3), wherein the main flow and the three branch flows form a parallel flow control packet, and a symbol P for the parallel flow control packet is usedm=[m:b1,b2,b3]Represents:
wherein, b1、b2And b3Respectively the number of three branches, m is the number of the main stream, m, b1、b2And b3The value range of (1) is 0-7;
specifically, as shown in FIG. 1An existing traffic flow diagram for eight lanes of an intersection (note: the intersection is the simplest traffic flow model, including all necessary traffic flows, and other actual intersections can be described by the model. for example, FIG. 4, includes a right turn traffic flow. The crossroad shown in FIG. 1 is denoted as crossroad
Is provided with
For traffic flow at intersections, i.e. complete set
In this embodiment, eight traffic flows in the intersection are numbered sequentially from 0 to 7 in the clockwise direction, and each traffic flow is sequentially marked as f0、f1、f2、f3、f4、f5、f6And f7Selecting the traffic flow with the number of 0 as a main flow, calculating the numbers of three branches which can run in parallel with the main flow with the number of 0 as the number 1, the number 3 and the number 4 respectively through a formula (1), a formula (2) and a formula (3), and taking the four traffic flows with the numbers of 0,1,3 and 4 as a parallel flow control packet P0=[0:1,3,4]Controlling; the parallel operation means that two traffic flows do not intersect at the intersection, and for any one traffic flow in the intersection, three traffic flows (branch flows) and the traffic flow (main flow) can be calculated to operate in parallel, for example, f0Three parallel branches are respectively f1、f3And f4Is denoted by P0=[0:1,3,4]And f1Three parallel branches are respectively f0、f5And f6Is denoted by P1=[1:0,5,6]And f2Three parallel branches are respectively f3、f5And f6Is denoted by P2=[2:3,5,6]And f3Three parallel branches are respectively f7、f0And f2Is denoted by P3=[3:7,0,2]And f4Three parallel branches are respectively f5、f7And f0Is denoted by P4=[4:5,7,0]And f5Three parallel branches are respectively f1、f2And f4Is denoted by P5=[5:1,2,4]And f6Three parallel branches are respectively f7、f1And f2Is denoted by P6=[6:7,1,2]And f7Three parallel branches are respectively f3、f4And f6Is denoted by P7=[7:3,4,6]。
Step 2, acquiring a parallel flow control packet switching sequence table through a formula (4) according to the serial number of the main stream and the serial number of the tributary;
wherein:
to
Representing any group of parallel flow control packets in the parallel flow control packet switching sequence table; x is the number of
i、x
jA number indicating a main stream in the parallel flow control packet sequence;
representing traffic flow x
iA parallel set of (a);
representing a complete set of cross-road traffic flows, i.e.
f
0To f
7Representing the traffic flow at a crossroad;
specifically, in
step 2, the numbers of the main stream and the tributary in the first parallel flow control packet are obtained according to
step 1, and a parallel flow control packet sequence table can be obtained through calculation according to formula (4). The basic idea of this formula can be derived from four conditions: by
It can be seen that L is formed by taking all traffic flows at the intersection as main flows in turn. By
It can be known that, in the L chain, the main stream in the following control packet must be a certain sub-stream in the previous control packet. By
It can be seen that any two control packets in L are different. By "one cycle unit size of
Length of "known
Namely the total traffic flow at the intersection.
In this embodiment, a traffic flow numbered 0 is used as a main flow, and a parallel flow control packet sequence table obtained by a formula (4) is shown in fig. 7, where the parallel flow control packet sequence table includes a plurality of sets of parallel flow control packet sequences, each of the parallel flow control packet sequences includes eight parallel flow control packets, and each of the parallel flow control packets includes one main flow and three tributaries.
Step 3, randomly selecting a group of parallel flow control packet sequences from the parallel flow control packet sequence list, and controlling the traffic flow of the crossroad according to the set passing time rule; specifically, the passing time rule is specifically as follows: keeping the main stream of traffic flow to pass all the time in the control time of the parallel flow control packet, and simultaneously adjusting the traffic flow passing time of the tributary based on an isochronous sequential switching rule in the control time of the parallel flow control packet;
specifically, in this embodiment, a group of parallel flow control packet sequences is arbitrarily selected from the parallel flow control packet sequence table, as shown in the figure, the selected parallel flow control packet sequences are 0:4,5,7,4:0,1,3,1:2,4,5,2:1,6,7,7:0,2,3,3:4,6,7,6:2,3,5, and 5:0,1,6 in sequence, a number before a part number in each parallel flow control packet represents a number of a main stream, and three numbers after the part number represent numbers of three tributaries, respectively. The method comprises the following steps of controlling the traffic flow of the crossroad through parallel flow control packets, wherein in the control time of the parallel flow control packets, in the embodiment, the control time of each parallel flow control packet is assumed to be 3T, the traffic flow of a main flow is kept to pass all the time, namely the traffic flow running time of the main flow is 3T (a signal lamp for controlling the traffic flow of the main flow is a green light), and meanwhile, in the control time of the parallel flow control packets, the traffic flow passing time of branch flows is adjusted on the basis of an isochronous sequential switching rule, namely the sequential passing time of three branch flows is T; fig. 7 is a timing chart of traffic control performed by the parallel flow control packet sequence in the present embodiment, which is used to control traffic lights of the corresponding traffic;
and 4, judging whether the current control packet sequence is finished or not, if so, returning to the step 1.
Example 2
Fig. 6 shows a traffic flow control method for an intersection according to the present invention, which comprises the following steps,
step 1, numbering eight traffic flows in a crossroad in sequence, selecting any one traffic flow as a main flow for traffic control, calculating the numbers of three branch flows which can run in parallel with the main flow according to the numbers of the main flow and through a formula (1), a formula (2) and a formula (3), wherein the main flow and the three branch flows form a parallel flow control packet, and a symbol P for the parallel flow control packet is usedm=[m:b1,b2,b3]Represents:
wherein, b1、b2And b3Respectively the number of three branches, m is the number of the main stream, m, b1、b2And b3The value range of (1) is 0-7;
specifically, FIG. 1 illustrates an eight lane traffic flow diagram of an existing intersection (note: the intersection is the simplest traffic flow model that includes all the necessary traffic flows, and other actual intersections can be described by the model. for example, FIG. 4 includes a right turn traffic flow. The crossroad shown in FIG. 1 is denoted as crossroad
Is provided with
For traffic flow at intersections, i.e. complete set
In this embodiment, eight traffic flows in the intersection are numbered sequentially from 0 to 7 in the clockwise direction, and each traffic flow is sequentially marked as f0、f1、f2、f3、f4、f5、f6And f7And selecting the traffic flow with the number of 0 as a main flow, and calculating the sum through a formula (1), a formula (2) and a formula (3)The serial numbers of three branches which can be run in parallel of the main stream with the serial number 0 are respectively the serial numbers 1,3 and 4, and four traffic flows with the serial numbers 0,1,3 and 4 are taken as a parallel flow control packet P0=[0:1,3,4]Controlling; the parallel operation means that two traffic flows do not intersect at the intersection, and for any one traffic flow in the intersection, three traffic flows (branch flows) and the traffic flow (main flow) can be calculated to operate in parallel, for example, f0Three parallel branches are respectively f1、f3And f4Is denoted by P0=[0:1,3,4]And f1Three parallel branches are respectively f0、f5And f6Is denoted by P1=[1:0,5,6]And f2Three parallel branches are respectively f3、f5And f6Is denoted by P2=[2:3,5,6]And f3Three parallel branches are respectively f7、f0And f2Is denoted by P3=[3:7,0,2]And f4Three parallel branches are respectively f5、f7And f0Is denoted by P4=[4:5,7,0]And f5Three parallel branches are respectively f1、f2And f4Is denoted by P5=[5:1,2,4]And f6Three parallel branches are respectively f7、f1And f2Is denoted by P6=[6:7,1,2]And f7Three parallel branches are respectively f3、f4And f6Is denoted by P7=[7:3,4,6]。
Step 2, acquiring a parallel flow control packet switching sequence table through a formula (4) according to the serial number of the main stream and the serial number of the tributary;
wherein:
to
Representing any group of parallel flow control packets in the parallel flow control packet switching sequence table; x is the number of
i、x
jA number indicating a main stream in the parallel flow control packet sequence;
representing traffic flow x
iA parallel set of (a);
representing a complete set of cross-road traffic flows, i.e.
f
0To f
7Representing the traffic flow at a crossroad;
specifically, in
step 2, the numbers of the main stream and the tributary in the first parallel flow control packet are obtained according to
step 1, and a parallel flow control packet sequence table can be obtained through calculation according to formula (4). The basic idea of this formula can be derived from four conditions: by
It can be seen that L is formed by taking all traffic flows at the intersection as main flows in turn. By
It can be known that, in the L chain, the main stream in the following control packet must be a certain sub-stream in the previous control packet. By
It can be seen that any two control packets in L are different. By "one cycle unit size of
Length of "known
Namely the total traffic flow at the intersection.
In this embodiment, a traffic flow numbered 0 is used as a main flow, and a parallel flow control packet sequence table obtained by a formula (4) is shown in fig. 7, where the parallel flow control packet sequence table includes a plurality of sets of parallel flow control packet sequences, each of the parallel flow control packet sequences includes eight parallel flow control packets, and each of the parallel flow control packets includes one main flow and three tributaries.
Fig. 7 only provides a parallel flow control packet sequence table using the traffic flow with the number 0 as the main flow, and corresponding parallel flow control packet sequence tables can be correspondingly calculated using other numbers as the main flows, which are not given in the present invention.
Step 3, randomly selecting a group of control packet sequences from the parallel flow control packet sequence list, and controlling the traffic flow of the crossroad according to a set passing time rule; specifically, the passing time rule is specifically as follows: the method comprises the following steps of keeping a main stream of traffic flow always passing in the control time of a parallel flow control packet, and adjusting the traffic flow passing time of a branch based on a real-time traffic data switching rule in the control time of the parallel flow control packet, wherein the adjusting of the traffic flow passing time of the branch based on the real-time traffic data switching rule comprises the following steps:
parallel set
I.e. f is the main stream, f
a,f
bAnd f
cAre sub-streams.
Obtaining the flow f 'of the current vehicle flow of the three branches'a,f′bAnd f'c;fa、fbAnd fc;f'1,f'3,f'4;
Obtaining the current waiting length L 'of the three branches'a,L′bAnd L'c;
Flow f 'according to the current traffic flow'a,f′b,f′cAnd the current waiting length L'a,L′b,L′cAnd calculating the traffic flow passing time of each branch by the formula (5):
wherein: suppose fb>fa>fc,T0=3T,T0Control time, T, for a parallel flow control packeta、TbAnd TcRespectively the traffic flow passing time of each branch flow.
Specifically, in the embodiment, the current traffic flow rate and the waiting length may be obtained in the manner shown in fig. 12, that is, a flow meter and a waiting detector are arranged at the intersection, the current traffic flow rate is collected by the flow meter, and the waiting length is collected by the waiting detector; a group of parallel flow control packet sequences is arbitrarily selected from the parallel flow control packet sequence table, as shown in the figure, the selected parallel flow control packet sequences are 0:4,5,7,4:0,1,3,1:2,4,5,2:1,6,7,7:0,2,3,3:4,6,7,6:2,3,5 and 5:0,1,6 in sequence, the number in front of the part number in each parallel flow control packet represents the serial number of the main stream, and the three numbers behind the part number represent the serial numbers of the three sub-streams respectively. And controlling the traffic flow of the crossroad through the parallel flow control packets, wherein the specific control process is that in the control time of the parallel flow control packets, in the embodiment, the control time of each parallel flow control packet is assumed to be 3T, the traffic flow of the main flow is kept to pass all the time, that is, the traffic flow running time of the main flow is 3T (a signal lamp for controlling the traffic flow of the main flow is a green light), and meanwhile, in the control time of the parallel flow control packets, the control time T of three sub-flows is controlleda、TbAnd TcCalculated by formula (5);
and 4, judging whether the current control packet sequence is finished or not, if so, returning to the step 1.
The method has the following beneficial effects:
the advantage of the packet traffic flow passing scheme is that the scattered passing time in the passing period is gathered, and under the condition of equal passing opportunities, the passing expenditure caused by introducing signal conversion is reduced to achieve the purpose of improving the passing amount. The analysis is as follows.
Document [6] indicates a combination of 12 types of safe traffic in total for 8 traffic flows shown in fig. 1. In fact, any traffic scenario ultimately embodies optimization and control of these 12 combinations. For example, in real life, the most common signal sequences are organized in a clockwise or counterclockwise order. Fig. 8 shows the timing of the counterclockwise sequential organization of signals, which is denoted as control mode 1. For another example, document [6] designs two algorithms, and can use data collected by the wireless sensor network to plan the switching sequence of 12 combination modes, which is denoted as control mode 2.
The traffic flow control method disclosed by the invention is compared with the control modes 1 and 2 as follows.
Comparing the timing sequences of fig. 8, 9 and 10, the parameters of table 1 can be obtained. From table 1, it is clear that, in the same 48T time and under the same traffic opportunities (6 traffic opportunities per traffic flow, i.e. 6 green lights), the traffic flow control method disclosed by the present invention has a maximum continuous traffic time of 5T and an occupancy of 40/48, while the other solutions have a maximum of 3T and a maximum of only 24/48. Therefore, it is concluded that: the continuous traffic flow control method disclosed by the invention can perform best under the condition of meeting at the same traffic machine in the same time.
Table 124 passage unit plan parameter comparisons
|
Conventional control method 1
|
Conventional control system 2
|
The invention discloses a scheme
|
Period of time
| 12T |
|
12T |
|
24T
|
Traffic opportunity |
|
6 times of
|
6 times of
|
6 times of
|
Shortest continuous transit time length
|
1T
|
1T
|
5T
|
Shortest continuous traffic ratio
|
36/48
|
8/48
|
8/48
|
Maximum length of continuous transit time
| 2T |
|
3T
|
5T
|
Maximum continuous traffic ratio
|
12/48
|
24/48
|
40/48
|
Maximum number of signal switches
|
6 times of
|
6 times of
|
2 times (one time)
|
Minimum number of signal switches
|
4 times (twice)
|
2 times (one time)
|
2 times (one time) |
Note: t in table 1 represents one transit time unit.
The comparison of crossing throughput for the three control modes is shown in fig. 11. As can be seen from FIG. 11, when the vehicle speed is below 40km/s, the vehicles passing through the intersection are substantially equal, so the performances of the three schemes are basically consistent; when the vehicle speed is more than 40km/s (namely, under the condition that the road speed limit is relatively high), the advantages of the control mode disclosed by the invention begin to appear, the performance of the control mode 2 is the second, and the performance of the control mode 1 is the worst. Data calculations show that the throughput of the control scheme disclosed by the present invention is improved by about 14.29% compared to control scheme 1.
Reference to the literature
[1]Nellore,K.;Hancke,G.P.A Survey on Urban Traffic Management System Using Wireless Sensor Networks[J].Sensors 2016,16(157).
[2] An intelligent traffic light control system based on WSN is designed according to the following steps of J measurement and control technology, 2009,28(12):56-59.
[3]Jinyang Li,Yuanrui Zhang,Yixiang Chen.A Self-Adaptive Traffic Light Control SystemBased on Speed of Vehicles[C]//2016IEEE International Conference on Software Quality,Reliability and Security Companion(QRS-C),Vienna,Austria IEEE,2016.
[4] Improved webster signal timing model study with bus priority considered at je [ D ]. university of south east 2015.
[5] The signal intersection Webster method delays calculating and correcting a model [ J ] of Zhao Yu 26104, Von Yu celery, Yang loyalty, proceedings of the engineering academy of Heilongjiang (Nature science edition), 2010,24(02).
[6]B.Zhou,J.Cao,X.Zeng,and H.Wu,“Adaptive traffic light control in wireless sensor network-based intelligent transportation system,”in IEEE 72nd Vehicular Technology Conference,Ottawa,2010.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.