DE10037240A1 - Method and arrangement for determining a connection current in a connection of a network - Google Patents

Abstract

In the method and the arrangement for determining a connection current in a selected connection in a network of interconnected nodes and connections through which connections in each case two of the nodes are connected, a current flowing in the network from a predefinable source node to a predefinable destination node, several paths are selected in the network, each of which leads from the source node via at least one of the connections to the destination node and at least one of which contains the selected connection. The stream is divided into sub-streams using a predefinable key, a sub-stream being assigned to each path. All partial streams that flow via the selected connection are combined to form the connection stream.

Description

The invention relates to a determination of a verb current in a connection in a network from below interconnected nodes and connections.

In a network of nodes and connections are more common assign two of the nodes through one of the connections connected. A stream that is in the network of one before specifiable source node to a predefinable target node in one such connection flows is referred to as connection current net.

A determination of a connection current in a network is known from [1].

The method described in [1] concerns the determination of egg traffic flow in a traffic network.

The traffic network known from [1] is made up of traffic nodes, (Intersections or branches) and transport links (Roads) built up. Two traffic nodes are through a traffic connection connected.

A total traffic flow V of egg flows in the traffic network a source node O to a destination node D.

At several predetermined traffic connections (measuring points) In the traffic network there is a local traffic flow measured.

A procedure for the selection and determination of measuring points in a traffic network is known from [2].  

To describe a traffic condition in the traffic network are used in the method known from [1] the local measured in selected traffic connections Traffic flows the traffic flows in the other traffic associations bonds determined.

This determination takes place in the context of an iterative, numeri method, wherein an equilibrium state in the ver traffic network is determined.

In this state of equilibrium, all total terms are in this case also referred to as travel times by everyone Partial traffic flows, which partial traffic flows each different paths from the source node O to the destination node ten D flow and together the total traffic flow V result, same size.

For the determination of the equilibrium state every Ver communication a corresponding instantaneous connection travel time and a corresponding maximum connection capacity activity assigned.

Exceeds a local traffic flow in a traffic ver binding the corresponding maximum connection capacity, so is used for the traffic connection depending on the over delayed connection travel time determined.

The travel time of a partial traffic flow, which on a predetermined path from the source node O to the destination node D flows, results from the addition of all undelayed and delayed connection travel times of those included in the route Transport links.

The flow of traffic is clearly illustrated in the subver traffic flows divided that the travel times of all subver reverse currents are equal.  

The known method has the disadvantage that an Er averaging a connection current in a connection of the Ver traffic network, generally a network, and consequently also the description of a state of the transport network the connection currents flowing in the connections, one high computing power and a long computing time required.

The invention is therefore based on the problem of a method and to provide an arrangement with which a determination ei connection stream in a network is improved.

The problem is caused by the procedure and the arrangement solved according to the respective independent claim.

In the method for determining a connection current in a selected connection in a network other connected nodes and connections through which ver bindings two of the nodes are connected, whereby in the network a stream from a predefinable source node to one Predeterminable destination node flows, there are several ways in which Network selected, each of which is from the source node at least one of the connections leads to the destination node and of which at least one ent the selected connection holds. The current is generated using a predetermined Key divided into sub-streams, each one Partial stream is assigned. All partial flows, which over the selected connection flow becomes the connection current summarized.

The arrangement for determining a connection current in a selected connection in a network of interconnected nodes and connections through which connections are connected in each case two of the nodes, with a current flowing in the network from a predeterminable source node to a predefinable destination node, has one Processor based on the type that

• - Several paths can be selected in the network, each of which from the source node over at least one of the connections leads to the destination node and at least one of which is the contains selected connection,
• - The current using a predetermined key can be divided into partial streams, with each path being a part electricity is assigned,
• - And all sub-streams, which over the selected connection flow, can be combined to form the connection stream are.

The particular advantage of the invention is that their application a considerable saving in computing time and Computing power is achieved.

As a result, the invention is particularly suitable for one State of a large and complex network, which one Has a variety of network nodes and connections write.

In addition, the invention enables in a simple manner a determination of the dynamics of a connection current or a dynamic in a network because for a lot number of times a time-varying ver binding current is determined in a network connection. The same applies to a large number of network servers bonds.

The arrangement is particularly suitable for carrying out the inventive method or one of the following explained further training.

Preferred developments of the invention result from the dependent claims.

The further developments described below relate both on the procedure and on the arrangement.  

The invention and the training described below conditions can be found in both software and hardware for example using a special electrical Circuit.

Furthermore, an implementation of the invention or one in white teren described further training possible by a computer readable storage medium on which a computer program stores which is the invention or training leads.

The invention and each described below can also be used Continuing education realized by a computer program product be, which has a storage medium on which a Computer program is stored, which the invention or Training.

In a further training, a network is used in which lead several ways over the selected connection.

For the description of a dynamics of the connection current the current is described by a time-dependent variable.

In one development, the current is generated using a predeterminable key divided into the partial streams. In the Allocation using the key becomes common or probabilities of the paths and thus the corresponding ones appropriate partial flows are taken into account.

It is for describing a dynamic in the network expedient that the key by a time-dependent size is described. It is also useful for connection streams to be determined for several selected connections.

For a realistic description of the dynamics in the network, it is also useful the connection current  to measure in the selected connection. Under use of the measured connection current, which using the Connection current determined method according to the invention and an optimization method, for example a Gra descent procedure, can be a realistic stream and more realistic partial flows can be determined.

A traffic network is preferably described by the network ben. In such a network, a node is a Intersection and be connected by a road wrote. The current in this case describes a ver traffic flow.

In one embodiment, at least one partial stream or one Connection current measured.

An embodiment is used for monitoring or control connection current or regulation.

An embodiment of the invention is shown in figures provides and is explained in more detail below:

Show it

Fig. 1 compounds a traffic network with traffic nodes and traffic;

Figure 2 shows a measuring point in the transport network to which a connection is measured.;

Fig. 3 process steps which are carried out in a determination of a connection current in the transport network.

embodiment traffic network

Fig. 1 shows a transport network 100, which 120 (roads) is constructed of transport nodes 110 (crossings or branches) and traffic connections. Two traffic nodes 110 are connected to one another by a traffic connection 120 .

A traffic flow V flows from a source node O 111 to a destination node D 112 in the traffic network 100 .

Furthermore, a plurality of routes w _j 130 are selected in the traffic network 100 , each of which leads from the source node O 111 to the destination node D 112 ( FIG. 3, step 310 ).

This relationship can be represented in the form of a route matrix W for the connection OD (source node-destination node):

in which:
i: index for a connection in the network,
j: index for a path leading from the source node 0 to the destination node D,
w _ij : 1, if path j leads via connection i,
0 if path j does not lead via connection i.

The traffic flow V is divided into partial traffic flows v _j , with each path w _{j being assigned} a partial flow v _j ( FIG. 3, step 320 ).

This relationship can be represented in the form of a traffic flow vector V = (v ₁ ,..., V _j ) ^T for the connection OD (source node-destination node):

The traffic flow V is divided into the partial traffic flows v _j according to a predefinable key ϕ _j as follows:

V _j = V. ϕ _j (3)

With:

When the traffic flow V is divided using the key strö _j , frequencies and / or probabilities of the partial traffic flows are taken into account.

All partial traffic flows v _j , which flow over the traffic connection i, are combined to form a connection stream k _i ( FIG. 3, step 330 ).

All relevant connection currents k _i , ie all connection flows k _i of traffic connections over which at least one path w _i of OD leads each, are summarized in a connection current vector K = (k ₁ ,..., K _i ) ^T :

This results in:

K = W. V, (5)

the traffic route matrix W to the relevant traffic ver ties is adjusted by the fact that lines of traffic gematrix, which each have only the values zero, ge be deleted.

The traffic flow V of the connection OD can be described by a so-called daily course line:

With:
l: index for a number of superimposed Gaussian curves,
n _G : number of superimposed Gaussian curves, here: n _G = 6,
g (ξ _l , t): Gaussian curve, used in the time interval [t - Δt, t], where there is a predefinable time interval at Δt,
ξ _l : average of the respective Gaussian curve,
a _l : amplitude of the respective Gaussian curve, [vehicles / h]
σ: standard deviation [min], here: 75 min,
exp (...): exponential function.

As a freely selectable parameter, the daily curve of the traffic current V each has n _G mean values ξ _l and amplitudes a _l .

To determine the freely selectable parameters ξ _l and a _l , the connection current k _{i is} measured at several predetermined traffic connections (measuring points m, here 5 measuring points m) in the traffic network.

A determination of measuring points in a traffic network is over [2] known.  

Fig. 2 shows a measuring point 200 in the transport network 100 to which the connection is measured.

For this purpose, a conductor loop 210 is worked into a roadway 211 , which measures a number i _{Fz of} the vehicles 212 which cross the measuring point 200 within a predetermined period of time Δt, and the respective speed v _{iFz of} the vehicle 212 which crosses the measuring point 200 ,

The measured values (i _Fz , v _iFz ) are transmitted to an evaluation unit 220 coupled to the conductor loop 210 . The evaluation unit 220 determines the connection current as a function of the transmitted variables.

The measurements take place in a predefinable time Chen distance Δt, here Δt = 30 min. so for every ver communication with associated measuring point a time series for the respective connection current is determined.

The connection currents measured at the measuring points m at a time t are combined to form a measured connection current vector Q = (q ₁ (t),..., Q _m (t)) ^T :

The freely selectable parameters ξ _l and a _l can be determined by minimizing an error function F. The following applies:

F = Q (t) - K '= Q (t) - W'. V → min (9)

in which:
K ': reduced connection current vector adapted to the measuring points m,
W ': reduced path matrix adapted to the measuring points m.

The error function F is minimized using a gradient descent method. It should be noted that any other optimization method for the Mini Fault function F can be used.

After the freely selectable parameters have been determined, a connection stream can be determined for any time t and for any traffic connection in the traffic network in accordance with context ( 5 ).

With traffic monitoring or traffic network planning connection currents according to the above relationships determined for a time interval of one day.

Using the determined time courses are given otherwise, d. H. if the connection current in one is too large Transport connection, changes to the transport network made men, for example designing a new transport network structure by adding or adding new traffic nodes creating / releasing new / existing traffic connections, and / or if necessary, control of a connection current Use of a traffic management system.

Below are alternatives to the embodiment described.

In an alternative to the exemplary embodiment, a time-dependent, predeterminable key ϕ _j (t) is used. The time dependency can be realized either by specifiable keys ϕ _j (t) at discrete times t or by continuous time-dependent keys ϕ _j (t). The relationships shown above apply accordingly.

To adjust the freely selectable parameters ξ _l and a _l by minimizing the error function F, the number of measuring points must be increased if necessary.

In a further alternative to the exemplary embodiment, the error function F is minimized by an alternating method. In a first step, the freely selectable parameters ξ _l and a _{l are} ascertained or adjusted, the time-dependent predeterminable key ϕ _j (t) being kept constant. In a second step, alternating with the first step, the time-dependent predeterminable key ϕ _j (t) is adapted, the freely selectable parameters ξ _l and a _{l being} kept constant.

In a third alternative to the exemplary embodiment, a time-dependent, predeterminable key ϕ _ji (t) is determined for each relevant connection i.

With such a key ϕ _ji (t), changing probabilities or frequencies of the partial traffic flows can be taken into account. The relationships shown above apply accordingly.

To adjust the freely selectable parameters ξ _l and a _l by minimizing the error function F, the number of measuring points must be increased if necessary.

The error function F is minimized by the alternating method described above. In the first step, the freely selectable parameters ξ _l and a _{l are} ascertained or adjusted, the time-dependent predeterminable key ϕ _ji (t) being kept constant. In the second step, alternating with the first step, the time-dependent predeterminable key ϕ _ji (t) is adapted, the freely selectable parameters ξ _l and a _{l being} kept constant.

The following documents are cited in this description:
[1] M. Bell et al., "A Stochastic User Equilibrium Path Flow Estimator", Transportation Research C, Vol. 5, No. 3/4, pp. 197-210, 1997
[2] H. Yang et al., "Optimal Traffic Counting Locations For Origin-Destination Matrix Estimation", Transportation Research B, Vol. 32, No. 2, pp. 109-126, 1998

Claims (12)

1. Method for determining a connection current in a selected connection in a network of interconnected nodes and connections through which connections two of the nodes are connected, wherein a current flows in the network from a predefinable source node to a predefinable destination node,
in which several paths are selected in the network, each of which leads from the source node via at least one of the connections to the destination node and at least one of which contains the selected connection,
in which the stream is divided into sub-streams using a predefinable key, a sub-stream being assigned to each path,
in which all partial streams that flow via the selected connection are combined to form the connection stream. 2. The method according to claim 1, where several routes lead over the selected connection. 3. The method according to claim 1 or 2, in which the current is described by a time-dependent variable becomes. 4. The method according to any one of claims 1 to 3, in which the predefinable key is a probability path taken into account. 5. The method according to any one of claims 1 to 4, where the key is a time-dependent variable is written. 6. The method according to any one of claims 1 to 5, in which a traffic network is described by the network.   7. The method according to claim 6, where a street intersection is described by a node and a road is described by a connection. 8. The method according to any one of claims 1 to 7, where the current describes a traffic flow. 9. The method according to any one of claims 1 to 8, in which at least one connection current is measured. 10. The method according to claim 9, at using the measured connection current, the connection stream and an optimization process of Current and the partial flows are determined. 11. The method according to any one of claims 1 to 10, used to monitor or control or regulate the Connection current. 12. An arrangement for determining a connection current in a selected connection in a network of interconnected nodes and connections through which connections two of the nodes are connected, wherein a current flows in the network from a predeterminable source node to a predefinable target node, which Arrangement has a processor which is set up such that
several paths can be selected in the network, each of which leads from the source node via at least one of the connections to the destination node and at least one of which contains the selected connection,
the stream can be divided into partial streams using a predefinable key, a partial stream being assigned to each path,
and all partial streams that flow via the selected connection can be combined to form the connection stream.