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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a guidance system for individual traffic in a road
system having stationary guide beacons arranged at the roads, the guide
beacons cyclically transmitting guidance information for reaching the
destinations selectable from its location to all passing vehicles, whereby
a specific destination is respectively selectable in the individual
vehicles and the guidance information allocated to the selected
destination can be selected from the totality of the guidance information
transmitted by a guide beacon.
2. Description of the Prior Art
A method for information transmission corresponding to such a guidance
system is already known (German AS No. 19 51 992). In contrast to other
known systems, this method has the advantage that only stationary
transmission devices are required along the travel paths and only
receiving devices are required in the vehicles. This method, however, has
the disadvantage that it requires relatively complicated devices and
procedures for the assignment of the destination selected in the vehicle
to specific guidance information from the totality of the information
transmitted. This is due to the fact that the destinations are selected
according to an absolute coding and that the guidance information
belonging to each destination must likewise be transmitted in this
absolute coding. If, in the destination guidance system, one wishes to
provide a very precise destination indication, then separate information
must be respectively transmitted given this absolute coding for a
corresponding number of destinations.
SUMMARY OF THE INVENTION
Given a guidance system of the type initially mentioned, the object of the
invention is to simplify the information transmission and the selection of
the destination information in the individual vehicle in such manner that,
given the finest possible destination subdivision, the transmission of as
small as possible an amount of information from each guide beacon suffices
in order to comprehensively inform the driver for his specific desired
destination.
This object is achieved according to the invention, in that the guidance
information are transmittable from each guide beacon arranged according to
selection fields, whereby each selection field represents a specific
region of a selection network at whose midpoint the appertaining guide
beacon is located, and whereby the size of the individual selection fields
increases exponentially with increasing distance from the midpoint.
Moreover, the destinations selectable in the vehicle are likewise assigned
to a respective, specific selection field of a selection network stored
according to fixed coordinates and coinciding in size and structure with
the selection network of the guide beacons, whereby the midpoint of the
vehicle selection network is the respective current location of the
vehicle. Upon passing a guide beacon, the selection of the guidance
information can be carried out in accordance with the destination
selection field coinciding at this moment both in the vehicle selection
network and in the guide beacon selection network.
The invention begins from the perception that a differentiated destination
guidance is required for the travel destinations in the close range of a
guide beacon than in travel destinations which are distant. Accordingly,
the selection network, serving as the ordering pattern for the
transmission and selection of the guidance recommendations, is not based
on an absolute coding but, rather, the selection network is always
designed concentrically to the respective guide beacon. The individual
selection fields are arranged around this centrum like the meshes of the
network, whereby their side lengths increase exponentially from ring to
ring toward the outside.
A differentiated destination guidance is possible with the selection
network as the ordering pattern. In the closer proximity of a guide
beacon, which one could designate as the local range, the meshes or,
respectively, selection fields of the selection network are relatively
narrow. In the distant range, the selection fields become greater with
increasing distance, so that, on the one hand, all possible travel
destinations in a larger area, for example in central Europe, can be
arranged in a relatively small number of selection fields and, on the
other hand, a sufficient discrimination of the travel destinations is
possible for the uniform distribution of the traffic flows to the entire
road system. Due to the relatively small number of selection fields, the
amount of information which must be transmitted by the guide beacon is
greatly reduced in contrast to known systems.
Computationally, the selection network is conducted with the vehicle from
guide beacon to guide beacon, so that the individual vehicle is always
situated in the center of the network. This can occur in that, for
example, a microprocessor in the vehicle calculates the relative
destination coordinates with respect to the beacon coordinates at each
guide beacon and, accordingly, assigns the selected travel destination to
a specific selection field. The information which relate to this selection
field are then selected from the totality of the guidance information
transmitted. Therefore, a simple read-only memory storing the boundary
coordinates of the individual selection fields suffices for the vehicle
device. At each guide beacon, the device can then calculate, with a
relatively simple search program, in which selection field its individual
travel destination is to be ordered.
The selection field itself, for example, can be constructed according to
the Cartesian coordinate system, so that the individual section fields
have a rectangular form. In another advantageous embodiment, a selection
network described with polar coordinates can also be employed.
Potentially, such a network does greater justice to the desire of the
traffic participants to arrive at their travel destination on as directly
as possible a path.
The selection of the travel destination in the vehicle can occur in a
manner known per se by inputting the destination coordiates from an
absolute coordinate system. The conversion into the selection network then
occurs, as already described, in accordance with the respective location.
For destinations that are frequently targeted, for example for a place of
residence, a place of work or the like, destination registers can be
provided in the vehicle device. Such stored travel destinations can then
be selected by pressing one or two keys.
The transmission of the guidance recommendations from the guide beacons to
the individual vehicle occurs with guide beacon messages which are
constantly cyclically transmitted. These messages contain the guidance
recommendations arranged in data blocks in accordance with the selection
network. In the data transmission procedure, it must also be guaranteed
that the vehicle device properly interprets the message of the guidance
recommendations when the appertaining vehicle enters the transmission
range of a guide beacon at any point in time. Since the selection fields
are arranged in rings around the midpoint, it is advantageous to transmit
the guidance information for a respective ring in a closed block and to
initiate each of these blocks by a synchronization character and to
terminate each with a safeguarding byte. Depending on the number of rings
of the selection network, therefore, the guide beacon message then
contains a corresponding number of information blocks. Losses of time due
to timing errors are relatively slight in this type of coding, for a
vehicle, for example, can receive a random block as the first, whereby the
block preceding in the cycle is then received as the last.
In accordance with the differing incidence of guidance information, the
individual message blocks can also have differing lengths.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the invention, its organization,
construction and operation will be best understood from the following
detailed description, taken in conjunction with the accompanying drawings,
on which:
FIG. 1 is a pictorial and schematic representation of the transmission of
guidance information from a stationary guide beacon to a vehicle;
FIG. 2 is a block diagram of the selection device for the guidance
information in a vehicle;
FIG. 3 is a plan view of a selection network for a combination of travel
destinations based on Cartesian coordinates;
FIG. 4 illustrates a guidance recommendation as a chain of guidance
vectors;
FIG. 5 illustrates a possible display in the vehicle for the recommended
travel direction;
FIG. 6 is a plan view of a selection network for a combination of travel
destinations based on polar coordinates;
FIG. 7 illustrates the format of a guide beacon message; and
FIGS. 8-11 illustrate examples of coding for the guidance recommendations.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the example of FIG. 1, the possible arrangement of the stationary
devices, on the one hand, and of the vehicle borne devices, on the other
hand, is illustrated. A vehicle FZ, which is moving along a road STR,
receives its guidance information from a stationary transmitter SE in the
guide beacon device BK. In the example illustrated, the guide beacon
device BK is a traffic signal housing in which the transmitter SE is
arranged in addition to the standard signal lights LF. Thus, existing
devices and poles can be co-employed for the transmission of the guidance
recommendations. For example, the memories and measuring devices belonging
to the guide beacon can also be housed in the housing of a traffic signal
control device STG which is connected (not shown) to the traffic light
structure.
Advantageously, the guide beacon device contains a microwave or infrared
transmitter which transmits the guidance information to the vehicle FZ,
namely to each passing vehicle FZ. To this end, the vehicle FZ contains a
microwave or infrared receiver FE which receives the guidance information
from the guide beacon transmitter SE and supplies the same to an
evaluation device AW in the vehicle. The evaluation device AW at the same
time receives information concerning the length and the direction of the
path respectively traversed. To this end, a path pulse generator WG for
hodometry and a magnetic field probe MS for measuring the respective
travel direction are attached to the vehicle. A microprocessor provided in
the evaluation device is programmed to form incremental path vectors from
the measured values of the path pulse generator WG and of the magnetic
field probe MS and sums these continuously. On the basis of the vehicle
position determined in this manner, the location-dependent guidance
information can be selected from a larger block and can be displayed at
the proper time. To this end, an input device EG and an output device AG
are connected to the evaluation device AW. For example, the selected
travel destination is input via the input device EG, for example a
keyboard. In the evaluation device AW, the information pertaining to the
selected travel destination are selected from the sum of the transmitted
guidance information and are displayed at the output device AG. To this
end, all guidance information are transmitted with an additional location
indication, so that, taking the respectively traversed path vector into
consideration, they are always displayed precisely when their testimony
applies and is to be observed.
The manner of operation of the evaluation device in the vehicle will now be
explained below on the basis of the block diagram of FIG. 2. The system
has a central station (not illustrated in further detail) which receives
traffic information from the entire region which can be covered and works
out guidance information from this traffic information for the individual
desired destination entering into considertion. For each starting
location, i.e., for each location of a guide beacon, there is a specific
group of desired destination and correspondingly appertaining guidance
information. This group of guidance information is transmitted to the
appertaining guidance beacons BK (FIG. 1). In addition, further
information can be stored in each beacon device, for example path
information independent of traffic conditions, speed regulations and
traffic signs and the like.
The guidance information are cyclically transmitted in the form of guidance
messages by the transmitter SE of the respective beacon device and are
received by the individual vehicles via their vehicle receiver FE. The
individual guidance messages first respectively contain an indication
concerning the precise location of the beacon device, i.e., the beacon
coordinates x.sub.B and y.sub.B. These beacon coordinates serve to
coordinate the destination coordinates x.sub.Z, y.sub.Z input in the
evaluation device AW of the vehicle with the guidance information.
Moreover, the dead-reckoning device including the path pulse generator WG
and the magnetic field probe MS can be corrected with the beacon
coordinates; in the present example, it is advantageous to have the
dead-reckoning respectively begin anew from the zero point upon passing
each guide beacon.
As mentioned above, the coordinates x.sub.Z, y.sub.Z of the selected travel
destination are input via the input device EG. To this end,
advantageously, an absolute coding according to grid squares is
undertaken. Thereby, grid squares of 100 m.times.100 m ought to be
expedient in order to render possible an effective destination guidance,
even in cities. In designing a traffic guidance system for a large area
such as the central European area, thus, one must proceed to this end from
a uniform coordinate network with an extent of approximately 3000
km.times.3000 km and smaller destination fields of 100 m.times.100 m. The
selected destination can be selected from a map with such grid squares and
be input in the form of two five-place numbers for the x and y
coordinates. For destinations which are frequently targeted, such as place
of residence, place of work and the like, destination registers can be
provided in the input device. In this case, the destination input is
reduced to pressing one or two keys.
The input destination coordinates x.sub.Z, y.sub.Z are stored in the input
device EG in a standard manner and are compared with the respective beacon
coordinates x.sub.B, y.sub.B when passing a guide beacon. The respective
relative destination coordinates x, y are formed therefrom in a subtractor
SUB by means of difference formations:
x=x.sub.Z -X.sub.B
y=y.sub.Z -y.sub.B.
The guidance information are transmitted from each beacon device according
to a relative coordinate system, whereby the guide beacon forms the
midpoint of this coordinate system. According to the same relative
coordinates, the guidance information appertaining to the selected
destination can now be selected in the vehicle.
The full precision of the destination coding is only required in the
selection of relevant guidance recommendations when the destination has
been nearly reached. At greater distances from the destination, the
evaluation device AW need only roughly calculate the direction in order to
be able to select relevant guidance recommendations. For selection,
therefore, a selection network consisting of individual selection fields
is employed, the mesh size of the selection network increasing
exponentially with the distance from the center. The pattern of such a
selection network is illustrated in FIG. 3. The appertaining guide beacon
and the vehicle just passing, as well as receiving the guide
recommendations, are respectively situated in the center of the selection
network. The selection network according to FIG. 3 is constructed
according to Cartesian coordinates. Quadratic or, respectively,
rectangular selection fields are arranged concentrically in rings, whereby
the mesh widths double from ring to ring. The side lengths (x.sub.i+1
-x.sub.i ; y.sub.i+1 -y.sub.i) of these selection fields thus increase
exponentially from ring to ring. In this example, each ring consists of
twelve selection fields which are continuously numbered. Thus, the
selection fields of the first ring R1 have the addresses 1-12, those of
the second ring R2 have the addresses 13-24, etc. If one gives the
selection fields 2, 5, 8 and 11 of the first ring (around the shaded zero
zone) an edge length of 100 m, then the selection network with 14 rings
covers a surface of 3277 km.times.3277 km. Thus, the selection fields 1-12
of the first ring have a side length of 0.1 km, the selection fields 13-24
of the second ring have the side length 0.2 km, and the selection fields
25-36 of the third ring have a side length of 0.4 km, etc.
The numbers of the selection fields serve as addresses for the respective
guidance information, namely both in the transmission from the guide
beacon to the vehicle and in the selection of the guidance information in
the vehicle. The pattern of the selection network is stored in the vehicle
in the form of the coordinates x.sub.1, x.sub.2, x.sub.3 . . . y.sub.1,
y.sub.2, y.sub.3 . . . for the individual rings in a read-only memory FSP.
Therefore, it suffices to respectively store 14 values for x and y in the
memory FSP given 14 rings, thus to allocate the selected travel
destination to a specific selection field and, thus, to a specific
guidance information in a relativey simple manner. To this end, the
calculated relative destination coordinates x and y are supplied to a
comparator VGA (FIG. 2) and are compared there with the selection network
coordinates x.sub.1 . . . x.sub.14, y.sub.1 . . . y.sub.14 from the
read-only memory FSP. One gains a selection field address f.sub.i from
this comparison which is supplied to a further comparator VGL. The
information respectively appertaining to the specific selection field
f.sub.i is selected from the total guidance information received in the
vehicle receiver FE in this comparator and is stored in the guidance
information memory LSP. The guidance information memory LSP, therefore,
contains all information which the vehicle driver requires in order to
reach the destination or, under certain conditions, the next guide beacon.
The output of the respectively location-related guidance information
occurs in accordance with the respective position which is taken from a
position memory PSP.
The position memory PSP is respectively set to zero when passing a beacon
and is kept constantly current proceeding from there with the assistance
of the dead-reckoning device. As mentioned above, the traversed travel
path is measured with a path pulse generator WG and the direction of
travel is measured with a magnetic field probe MS; subsequently, the
respective path vector is determined in a vector determining device VB.
This path vector is added in an adder ADD to the respective earlier
vehicle position from the position memory PSP; the new vehicle position
resulting therefrom is again input into the position memory.
The guidance information are advantageously provided as a chain of guidance
vectors as is illustrated in FIG. 4. The recommended path, for example,
begins at a guide beacon BK or attaches to the last intermediate
destination of a guidance recommendation. FIG. 4 now, shows what
information, for example, is transmitted for the illustrated path segment
and displayed in the vehicle. If the vehicle begins to follow the guidance
vector LV1, which is identified in an auto-navigation device AN, then, in
the example illustrated, the traffic sign "Arterial Highway" is also
displayed. In FIG. 4, the display duration is also indicated as a
plurality of guidance vectors in addition to the appertaining character.
The traffic sign "Arterial Highway", thus, is displayed for the duration
of one guidance vector. While the vehicle is still following the guidance
vector LV1, the guidance vector LV2 is calculated from the stored
coordinates of its beginning and of its end and is already displayed.
Thus, the driver has time to enter the proper lane. At the beginning of
the guidance vector LV2, the traffic sign "Pay Attention To Right Of Way"
then appears and is displayed for the duration of 5 guidance vectors, i.e.
up to the end of guidance vector LV6. Moreover, a travel direction arrow
for the guidance vector LV3 is displayed in the display field. The
distance up to the intersection at the end of guidance vector LV2 can also
be continuously calculated and displayed. Further traffic signs can be
transmitted and displayed in the same manner.
A display possibility for the guidance vector is illustrated in FIG. 5.
Thereby, it is a matter of a compass instrument RI with an angular
division WE, whereby a directional arrow RP describes the respectively
recommended direction of travel. In addition, a display field AF for an
alphanumerical distance display is provided in the center. Here, one can
read from which point the recommended and displayed change of direction
applies. In the example of FIG. 5, therefore, it can be read from the
display device that a half-turn toward the right is to be made after 310
meters.
The preceding description of the selection of relevant guidance
recommendations was based on a selection network which, according to FIG.
3, is constructed according to a Cartesian coordinate system. In terms of
traffic engineering, however, a selection network described with polar
coordinates could also be advantageous. Such a selection network with
polar coordinates is illustrated in FIG. 6. As in the selection network
according to FIG. 3, the individual selection fields are also numbered
consecutively here. The individual rings are now circular; thereby, the
radii r.sub.i increase exponentially from the inside toward the outside of
the network. With r.sub.i =0.1+2.sup.i km and with i=0 . . . 15, such a
selection network covers a circular area with a diameter of 3277 km.
Otherwise, the calculation of the destination field and the allocation to
the guidance information occurs in accordance with the method described
above.
The guide beacons transmit their guidance recommendations ordered according
to selection fields, namely cyclically beginning with the selection fields
of the first ring, then those of the second ring, etc. Given this data
transmission procedure, it must be guaranteed that the evaluation device
AW correctly interprets the message of the guidance recommendations when
the appertaining vehicle enters the transmission range of a guide beacon
at any random point in time. For this reason, the guidance beacon messages
are subdivided into a plurality of data blocks. Advantageously, these data
blocks respectively correspond to one ring of the selection field. FIG. 7
schematically illustrates the format of such a guide beacon message which
is cyclically transmitted. Each data block is initiated by a
synchronization character and is terminated by a safeguarding byte. The
block B0 contains the guide beacon identifier, the blocks B1-B4 contain
the guidance recommendations for the selection fields of the corresponding
rings R1-R14. Losses of time due to timing errors are relatively slight in
this manner of coding for a vehicle can receive, for example, the data
block B4 as the first data block and receive the data block B3 as the
last, whereas another vehicle which arrives in the transmission range of
the guide beacon somewhat later receives the data block B10 as the first
and the data block B9 as the last.
A possible coding for the individual data blocks of the guidance beacon
message is illustrated in FIGS. 8-11. FIG. 8 shows the coding of block B0,
i.e. the guide beacon identifier. To this end, for example, 8 byte can be
employed. The data block B0, like every other data block, begins with a
synchronization character SYN with eight bits. Next, there follows the
section OFB in which the appertaining ring can be characterized as local
or distant range. In the data block B0, only a "0" is here. Following
thereupon is a code section BAK for the beacon coordinates. In the
example, 20 bits are respectively provided here for the x coordinates and
for the y coordinates. The termination of the block B0 is then formed by a
cyclical data block safeguard ZYB.
FIG. 10 illustrates a coding for a ring R in the local range, i.e. for one
of the inner rings of the selection network. The ring number, for example
1 or 2, is coded after the synchronization character SYN. The number of
the rings for the local range, however, is variable from guide beacon to
guide beacon. In rural areas, the local range will generally be greater
than in inner-city areas with a dense road system and smaller intervals
between the guide beacons. Therefore, following the ring number, it is
respectively marked as to how the following information are to be
interpreted. The next byte in the coding area AUF indicates the starting
point or, respectively, the starting field for the chain of guidance
vectors. That can either be the ring 0000, i.e. the location of the guide
beacon, or the last intermediate destination of a guidance recommendation
which has led to a selection field SEL of a ring R lying further toward
the inside.
There subsequently follows a variable number of guidance vectors LV1, LV2 .
. . , of which each can be coded with three byte. Such a guidance vector
coding is illustrated in FIG. 9. Given 8 bit each for the x and y
coordinates, one can describe intermediate destinations in an area of 2560
m.times.2560 m in 10 m units. In city areas, a local region should not
exceed these dimensions, but would in suburbs or in rural areas.
Therefore, in the area OFB of the guidance recommendation according to
FIG. 10, the last two bits can be employed for indicating a scale
(indicated with M there). In this manner, one can multiply, for example,
the 10 meter units with the factors 1, 2, 5 or 10 and thus obtains a
maximum local area of 25.6 km.times.25.6 km.
The end of the guidance vector chain LV1, LV2 . . . leading to the
selection field 1 (SEL 1) of a ring is marked by a clearing signal SZ
(FIG. 10). This clearing signal, for example, reads 1111; the address of
the next selection field (SEL 2) follows thereon as a starting character
AZ. There subsequently again follows the marking of a starting field and
the following guidance vectors, etc. The cyclical data block safeguarding
ZYB as in FIG. 8 follows behind the clearing signal SZ for the twelfth
selection field of a ring.
The guidance recommendations of the rings in the distant range are
significantly shorter. An example of this is illustrated in FIG. 11. Only
one byte is provided for each selection field SEL.sub.i, SEL.sub.i+1, etc.
Thereby, i respectively indicates the first selection field of the
appertaining ring, etc. A specific selection field in the local range
which is to be approached in order to arrive at the distant destination is
respectively coded in this one byte for each selection field. Therefore, a
respective ring R and a selection field SEL are programmed as an
intermediate destination. The path to these intermediate destinations is
to be respectively derived from the corresponding message blocks for the
indicated rings R.
The amount of information which will have to be transmitted with a guide
beacon message will differ from guide beacon to guide beacon. It depends
on the size of the local regions and, thus, on the plurality of guide
vectors required. If a guidance recommendation contains many changes of
direction or if many traffic signs are pointed out, then many guide
vectors are to be transmitted. If, on the other hand, the path to be taken
can be simply described, then one only requires a few guide vectors. By
means of the structure of the selection network with meshes becoming
greater toward the outside, however, it is assured overall that the total
required informational amount can be transmitted from the individual
beacon to the passing vehicles in the time available.
It will be apparent that many modifications and variations may be effected
without departing from the scope of the novel concepts and teachings of
the present invention.
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