GB2507152A

GB2507152A - Modelling an ambient field of an object

Info

Publication number: GB2507152A
Application number: GB1314268.2A
Authority: GB
Inventors: Holger Mielenz; Christian Heigele
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2012-08-10
Filing date: 2013-08-08
Publication date: 2014-04-23
Anticipated expiration: 2033-08-08
Also published as: GB201314268D0; GB2507152B; DE102012214307A1; FR2994486B1; FR2994486A1

Abstract

Modelling an ambient field of an object, in particular of a vehicle, comprises providing at least one cell 1 having a unique identification, neighbourhood relationships whichfor each direction 11, 12 in which further linking cells may be located includes an identification of an existing adjacent cell or information indicating no adjacent cell is present, and items of occupancy information that are formed by a spatial discretisation of the cell. The current position of the object and an obstacle is determined in the environment of the object and the occupancy value or occupancy probability of the discrete obstacle position is changed. An intermediate position between the object and the obstacle is changed to indicate a vacant position. The occupancy values can indicate, occupied, vacant and unknown and the cells may represent a two dimensional or three dimensional environment occupancy map. Information about the environment may be obtained by sensors on the vehicle.

Description

Description Title

process and apparatus for modelling an ambient field State of the art The present invention relates to a process and an apparatus for modelling an ambient field, the extent of which is unknown, which has been detected by arbitrary sensorics.

In particular, the present invention relates to the automobile ambient field, since it is often advantageous here to create ambient-field maps of the environment, whereby items of information about the environment are obtained by means of sensors that are used in the vehicle.

The processes currently available for representing an ambient field can, in principle, be divided up into two categories. On the onehand, a mapping with the aid of tree structures, and, on the other hand, a mapping with the aid of discrete.cells arranged in a grid which is frequently uniform.

In the case of the tree structures, each node of the tree maps a defined two-dimensional or three-dimensional space and may possess bccupancy information about this space.

Additionally, each node offers the possibility of sub-nodes if the territory that this node describes can be, or is to be, described in more detailed manner. The same applies to each sub-node. Accordingly, starting from a central principal node, the complete space that this node describes can be mapped arbitrarily fineLy. If measured data pertaining to regions outside the principal node are available, either these data can be discarded or alternatively a new principal node is created that covers a more far-reaching space than the principal node previously available, and the previous principal node, and optionally further principal nodes, is/are subordinated to the new principal node.

In the case of the grid-based processes, most commonly a two-dimensional or three-dimensional space, limited to a defined extent, is described by a usually uniform rasterisation. Each of these cells contains a measure of occupancy (frequently a probability of occupancy) and optionally further information (such as, for example, altitude or traversability) Such cells may also contain a list of items of altitude information stacked on top of one another, in order to reproduce compressed 3D information in a2Dmap.

Known, moreover, from the state of the art is printed publication DE 10 2008 036 009 Al, which describes a process for protecting a vehicle against a collision. For this purpose, sensors have been fitted to the vehicle, which register the ambient field of the vehicle and enter the data acquired in this way into, an ambient-field map, the ambient-field map having been realised as a grid-based map. The grid points therein have been arranged equidistantly and can assume the values "vacant", "occupied" or "unknown", so that a discretised model of the environment arises. . Similarly, from DE 10 2010 013 093 Al a process is known which enters obstacles in the environment of a vehicle into a cell-based map. Overall, however, the cell-based and grid-based processes predominantly have the drawback that here always a two-dimensional or three-dimensional space limited to defined tolerances is available by way of ambient-field map, into which the data acquired with respect to existing obstacles are entered.

Moreover, the space has most commonly been uniformly discretised and can consequently store occupancy values or occupancy probabilities at the discrete points. Therefore the processes described above are very inaccurate precisely in the marginal regions of the discretised space, since measured values that relate to regions outside the discretised space are discarded. Moreover, no flexibility is guaranteed, since the discretised space cannot be extended, so that in the event of the necessity to have to map a larger region the entire discretised space always has to be discarded, and a new, larger discretised space has to be created.

Disclosure of the invention

The process according to the invention uses a linking of individual cells, whereby the scope of the linked cells can be extended or restricted in arbitrary mantier. Therefore the process is very flexible and canpreferably also be employed where computing resources are available only to a limited degree.

In accordance with the invention, at least one cell is provided which includes the fOllowing features. Firstly, an identification is present with which the cell can be addressed. The identification in this connection is unique among all existing cells. Moreover, the cell contains neighbourhood relationships, whereby for each direction in which a further cell may be located the aforementioned identification of the adjacent cell has been stored. In case no adjacent cell were to be present in one direction, this has likewise been stored. Overall, it can therefore be established whether further cells are located at the adjacent positions of a cell or whether the boundary of the modelled ambient field has been reached here. Finally, itenis of occupancy information are available in each cell, which have been realised by a spatial discretisation of the cell. The discretisation of all existing cells may preferably be identical, whereby, in similarly preferable manner, cells may also be discretised variably. Moreover, the discretisation may vary preferably within the cell or may alternatively also preferably be uniform over the cell.

At each discrete point of a cell an occupancy value or an occupancy probability is stored. In this way, obstacles in the environment can be modelled.

With the provision cf at least one cell, it is possible to

create an ambient-field map of an object. For this

purpose, firstly a discrete object position within the at least one cell has to be determined. This corresponds to a position that represents the current location of the object

in the ambient-field map. In the course of a first

initialisation of the ambient-field map, corresponding to a first-time provision of at least one cell, the discrete object position is preferably freely defined. After this, the environment of the object is examined for obstacles, and in the event of an obstacle being present the position thereof is determined. Subsequently the position ofthe obstacle is-transformed into a discrete obstacle position, so that within the cells which have been provided a discrete position is determined that corresponds to the real position of the obstacle. For the purpose of modelling the obstacle, the occupancy value at the discrete obstacle position is changed in such a manner that, as a result, the existence of an obstacle is indicated.

Lastly, in accordance with the invention it is established whether discrete intermediate positions are located between the discrete obstacle position and the discrete object position. Since a detection of an obstacle normally presupposes that the region between object and obstacle is vacant, in the case of the existence of at least one discrete intermediate position the occupancy information at the at least one discrete intermediate position is set to a value that indicates that this point is vacant. The occupancy information has preferably been designed relative to the previous occupancy information at the same discrete intermediate position, so that by means of the new value for the occupancy information it is indicated that the point is freer than previously assumed.

It is, moreover, preferably possible that a cell is able to store further data besides the items of information that have been described. This may be, for example, a value for the clearance height at a defined point, or. a value for the traversabilityof the undersurface. Accordingly, each cell can be adapted to the currently prevailing environment, by characteristic data pertaining to the environment being incorporated into the modelling.

The invention relates, moreover, to an apparatus for modelling an ambient fieldof an object. In accordance with the invention, the apparatus includes a storage device which has preferably been set up to store one or more of the aforementioned cells. Moreover, the apparatus includes an environment sensor for detecting obstacles in the environment of the object. This sensor may be, for example, a camera system, an ultrasonic sensor, a radar sensor or a lidar sensor. With the envi±onment sensor it is preferably possible to determine both the presence of an obstacle and the spacing of an obstaclefrorn the object.

Finally, the apparatus includes a control unit which has been connected both to the storage device and to the environment sensor. In accordance with the invention, the control device has been set up in such a manner that said device implements the aforementioned process according to the invention.

The process according to the invention and the apparatus according to the invention exhibit several advantages in -comparison with the state of the art.

By virtue of the iterative linking and creation of the cells, the process is very compact. Only that space, about which items of environmental information are actually available, is described. A large discretised space, as in the state of the art, is not necessary.

Since the local environment is described contiguously in the storage device, the control unit with the storage device is able to calculate highly efficiently. The tolerances of the ambient field have no influence on this. -Solely the jumps from one cell to a further cell may necessitate jumps within the storage device. -7-.

If a situation analysis exists, interesting regions of the environment can be determined, and the associated cells can be created with a finer discretisation. For example, especially for narrow alleyways or parking spaces a fine discretisation is advisable, whereas for main roads a coarser discretisation is sufficient.

The dependent claims show preferred further developments of the invention.

In an advantageous manner the process according to the invention is executed by the following steps being followed. Firstly, from all existing cells an initial cell is selected which in at least one direction exhibits no neighbourhood relationship. Preferably, by way of initial cell that cell can, for example, be chosen within which the discrete object position is located. After this, a further cell is generated, this procedure involving the following steps. By way of first step, an identification of the further cell is defined, whereby the identification, above all in the light of the cells already generated or provided, is unique.and relates exclusively to the further cell. Subsequently the neighbourhood conditions can be stored. This includes, on the one hand, a storing of the identification of the further cell by way of neighbourhood relationship in the initial cell, and a storing of the identification of the initial cell by way of neighh.ourhood relationship in the further cell. Tn this way, the initial * cell and the further cell have been locally linked to one *another, so that a referencing is possible not globally but rather merely starting from an adjacent cell. Lastly, * items of occupancy information that are formed by a spatial discretisation of the further cell are provided in the * -8-S further cell. At each discrete point in this connection a discrete occupancy value or an occupancy probability has been provided.

By virtue of the neighbourhood relationships, based merely on the adjacentcells, the mapping cf multi-level situations is also possible without difficulty. For example, ramps in multi-storey car parks do not have o be detected specially as such but result automatically in a new generated cell with appropriate neighbourhood conditions.

With the generating of a further cefl, it is possible to extend the ambient-field map of the object. For this purpose, once again a discrete object position is determined within dhe of the cells which have been provided or generated. Subsequently the environment of the object is examined further for obstacles, and in the event of an obstacle being present the position thereof is determined.

Then the position of the obstacle is transformed into a discrete obstacle position, so that within the cells which have been provided or generated a discrete position is determined that dorresponds to the real position of the obstacle. For the purpose of modelling the obstacle, the occupancy value at the discrete obstacle position is changed in such a manner that, as a result, the existence of an obstacle is indicated. Lastly, in accordance with the invention it is established whether discrete intermediate positions are located between the discrete obstacle position and the discrete object position. In the event of the existence of at least one discrete intermediate position, the occupancy information at the at least one discrete intermediate position is set to a value that indicates that this point is vacant.

Overall, this preferred embodiment makes! it possible to extend the modelling region of the ambient-field map very easily. This is a great advantage in comparison with the state.of the art, since here an extension of the modelling regidn is not possible, or is possible only with great effort.

In this connection it is particularly advantageous to apply the described preferred embodiment of the process according to the invention merely when a discrete obstacle position in the existing cells -that is to say, in the cells which have been provided and/or generated -cannot be determined.

Only in this case is it advantageous to generate a further cell, in order to enlarge the entire modelling region. It can then preferably be examined once again whether a discrete obstacle position in the enlared modelling region can be determined.

Another advantageous embodiment of the process according to the invention comprises the executing of the following steps. Precisely one cell is provided, which is designated as the master cell. Consequently a discrete object position within the master cell is also defined. Lastly a spatial discretisation is defined, with which the items of environmental information are to be stored. With these steps, the generating of an ambient-field map with a single cell, the master cell, is initialised. Should further cells be required, these are inserted on demand. The memory needed is therefore restricted to a minimum.

Moreover, there is preferably provision that the occupancy value can assume the values "occupied", "vacant" and "unknown". The occupancy probability can preferably be specified with a value between 0 and 1, where 0 preferably corresponds to "vacant", 0.5 preferably corresponds to "unknown", and 1 preferably corresponds *to "occupied".

This enables a comprehensive describing of the environthent of the object within the cells.

In particularly preferred manner there is provision that for each cell a number of items of occupancy information are determined, whereby only items of occupancy information that do not contain the value "unknown" are taken into account. Should this number fall below a first value, the corresponding cell is deleted. By virtue of the deleting of cells with only little information content, storage space. can be conserved, since it can be assumed that a cell with little information content does not play an important role in the modelling of the ambient field. The first 2Q value is preferably dependent on the discretisation of the cell, so that in the case of fine discretisaticn the first value is higher than in the case of coarse discretisation.

In advantageous manner the process according to the invention is implemented by the cells being regarded as rectangular. In particular, it is advantageous if the cells are regarded as square. In this case, an environment to be modelled can be mapped very easily by means of the cells. In addition, merely four neighbourhood conditions have to be dealt with.

Moreover, there is preferably provision that the cells all exhibit the same size. This simplifies the process -11 -according to the invention, since all the cells can be treated identically. Alternatively, there is preferably provision that the cells exhibit differing sizes. Hence districts having different regions of varying size, for example, can be imaged more easily.

In addition, the cells may preferably represent a two-dimensipnal space or even a three-dimensional space.

Depending on the type of object; the environment of which is being modelled, the one or other type is advantageous.

For a land-based vehicle, a use of two-dimensional cells, for example, is sufficient.

In an advantageous embodiment of the process according to the invention the following steps are additionally executed. Firstly, an absolute position of each cell within a fixed coordinate system is determined. This is done with the aid of the neighbourhood relationships, so that the relative data of the neighbourhood relationships are converted into absolute data within the fixed coordinate system. Subsequently it is determined which cells have been placed at an identical point within the coordinate system. Such a situation may occur if a position within a first cell is approached by two different adjacent cells. Since the adjacent cells possess no information whatsoever as to whether the respective other cell has already generated the first cell, at any rate a new first cell is generated. Consequently two first cells are present which, however, exhibit the same content.

Therefore for the case where two-cells exhibit the same absolute position the items of occupancy information are * compared. Should the items of occupancy information *of the cells intersect, or should the items of occupancy -12 -information be identical, it is to be assumed that both cells are modelling the same territory. For this reason, * in a concluding step the cells with identical or partly identical items of occupancy information are merged to form a single cell.

* In a preferred embodiment *of the apparatus according to the invention the storage device has been set up to return, upon a request for a new cell by the control unit, the identification of a first cell from a first number of cells without occupancy information and neighbourhood -relationships. Hence it is possible to accelerate the process of generating a cell, since here no physical storage space has to be requested, but rather use is made of a cell from a stock of empty cells. Therefore there is preferably provision that the storage device always stores a second number of cells without occupancy information and neighbourhood relationships. The second number of cells in this case is preferably at least just as large as the first number of cells. Consequently a stock of cells is always available, in which connection the time-consuming process of requesting storage space has been decoupled from the process of generating the cell.

Brief description of the dra*ing

Exemplary embodiments of the invention will be described in detail in the following with reference to the accompanying drawing. In the drawing: Figure 1 is a schematic view of a cell such as is used in the process according to the invention according to a preferred embodiment, -13 -Figure 2 is a schematic view of two cells with which the

ambient field of a vehicle is modelled with the

process according to the invention according to the preferred embodiment, Figure 3 is a schematic view of a real environment which is modelled with the process according to the invention according to the preferred embodiment, Figu±e 4 is a schematic, planar view of several cells which were generated with the process according to the invention according to the preferred embodiment, Figure 5 is a schematic, spatial view of several cells which were generated with the process according to the invention according to the preferred embodiment, and Figure 6 is a schematic overview of the apparatus according to a preferred embodiment of the invention. -Embodiments of the invention Figure 1 shows a first cell 1 which is used for modelling an environment of an object. The first cell 1 exhibits a total of four neighbourhood relationships which divide up into a first direction 11, a second direction 12, a third direction 13 and a fourth direction 14. Consequently it is possible, starting from the first cell 1, to generate four -14 -further cells. The first cell 1 has been discretised and can receive items of occupancy information at discrete points 10. These items of occupancy information have firstly been pre-allocated with the value "unknown".

In Figures 2 and 3 it has been illustrated how the cells are used in order to model the environment of a vehicle 4.

In this connection, Figure 2 represents the modelled state by means of a first cell 1 and a second cell 2, whereas Figure 3 sketches the real environment from a bird's-eye view. With a view to better clarification, the regions that are modelled by the first cell 1 and the second cell 2 have also been sketched in Figure 3. Within the first cell la discrete object position 40 is determined which coincides with the real position of the vehicle 4. As shown in Figure 3, the vehicle 4 is driving alongside an obstacle 3. Ambient-field sensors 5 built into the vehicle register the obstacle 3, so that the latter can be represented in the first cell 1 at the discrete obstacle positions 32. For this purpose, a notional laser beam, for example, is shone between discrete object position 40 and each discrete pbstacle position 32, and the items of occupancy information along the laser beam are set to "vacant". At the end of the beam that is to say, at the discrete obstacle positions 32 -the occupancy information is changed to "occupied". However, as soon as the vehicle 4 approaches the boundaries of the region that can be modelled with the first cell 1 the problem arises that a discrete obstacle position 31 is situated outside the cel.1 1 and consequently cannot be represented. For this reason, *a second cell 2 is generated in the second direction 12 of the first cell 1, so that a neighbourhood relationship exists between the first cell 1 and the second cell 2.

-

With successful eneration of the second cell 2, consequently discrete obstacle position 31 can also be modelled.

The generating of new cells is always executed on the basis ofa cell that is already present. Accordingly, in Figure 4 an example has been represented of how, sta:ting-from the first cell 1, a total of three further cells are generated: the second cell 2, a third cell 6 and a fourth cell 7. In this connection the neighbourhood relationship of the first cell 1 in the second direction 12 is identical to the neighbourhood relationship of the second cell 2 in the fourth direction 24. Consequently a transition from the first cell 1 to the second cell 2 is present here. The same applies to the neighbourhood relationships of the second cell 2 relative to the third cell 6 in the third direction 23 of the second cell 2 and in the first direction 61 of the third cell 6, and also to the neighbourhood relationships of the third cell 6 relative to the fourth cell 7 in the fourth direction 64 of the third cell 6 and in the second direction 72 of the fourth cell 7.

However, there is no neighbourhood relationship between the first cell 1 and the fourth cell 7. Should the vehicle 4, starting from a location in the fourth cell 7, move in the direction of the first cell -that is to say, in the first direction 71 of the fourth cell 7 -a new cell would be created which would be situated absolutely at the same position as the first cell 1. The same also applies to the third direction 13 of the first cell 1.

The advantage of the local neighbourhood relationship.s within the cells has been elucidated in Figure 5. In this case, the vehicle 4 is driving up a helical tower, as may -16 -be the case, for example, in multi-storey car parks.

Starting from the first cell 1, firstly several cells are generated in the seccnd direction 12 of the first cell 1 until finally a fifth cell 8 is obtained. Starting from the fifth cell 8, a further cell 9 is generated which is situated absolutely at the same position as the first cell 1, but at a higher level. This is automatically taken into account with the process according to the invention, since the further cell 9 is generated on the basis *of the fifth cell 8 in the third direction 83 of the fifth cell 8.

Consequently the neighbourhood relationship of the fifth cell 8 in the third direction 83 points not towards the first cell 1 but rather to the further cell 9. Similarly, the neighbourhood relationship of the first cell 1 in the first direction 11 also does not point to the fifth cell 8 located at the same absolute position..

In principle, however, the case could also occur that the first cell 1 and the further cell 9 describe the same space, for example because the object 4 has moved in a circular-arc trajectory on one level. Therefore in an additional step it is examined whether cells are present that have to be merged. This is done by the absolute position of each of the generated cells being ascertained.

Consequently it can be established that the first cell 1 and the further cell 9 exhibit the same absolute position.

Subsequent to this, it is examined whether the cells located at the same absolute position describe the same content. For this purpose the items of occupancy 30. information are compared, and in the event of a limiting value of a measure cf the similarity of the items of occupancy informaticn being exceeded the items of occupancy information and the neighbourhood relationships of the two -17 -cells are merged in one of the cells, the cell no longer required being deleted.

In Figure 6 the apparatus according to the invention for modelling an environment has been represented. Said apparatus includes a storage device 200 which has been set up to store a plurality of cells. Connected to the storage device 200 is a control device 100 which is likewise connected to the environment sensor 5.

The control device 100 can therefore provide and generate cells which are subsequently stored into the storage device 200. By means of the environment sensor 5 the control device 100 scans the environment to be modelled for obstacles, and in this way determines the existence of obstacles 3 as well as the discrete obstacle positions 31, 32 within the cells which have been generated or provided.

Moreover, the control device100 is able to realise the modelling of an ambient field also with limited storage space. In this case a number of cells that may be used maximally is defined. As soon as this number has been attained, in the case of a further cell which is required the cell that was first set up is deleted, and consequently storage space is freed for a further cell. The model therefore encompasses merely the most recent part of the environment, but in exchange it manages with limited storage space.

In addition, the storage device 200 may be bipartite, one part having been designed as archive with long access-time, and a further part having been designed as operational memory with short access-time. Consequently the deleting

-LB -

o cells described in the preceding section may also * represent a relocating cut of the operational memory into the archive, so that a cell from the archive is restored in the case of a return of the object 4 into an environment that corresponds to a part of the model already archived.

Claims

-19 -Claims 1. Process for modelling an ambient field of an object (4), in particular of a vehicle, comprising the following steps: -providing at least one cell (1, 2, 6, 7, 8, 9) having -a unique identification, -neighbourhood relationships which for each direction (11, 12, 13, 14) in which further cells (1, 2, 6, 7, 8, 9) may be located include an identification of an existing.adjacent cell or an item of information to the effect that no adjacent cell is present in this direction, and -items of occupancy information that are formed by a spatial discretisation of the cell (1), whereby at each discrete point (10) a discrete occupancy value or an occupancy probability has been specified, -determining a discrete object position (40) in the at least one cell (1, 2, 6, 7, 8, 9) which represents the current position of the object (4), -detecting an obstacle (3) in the environment of the object (4) and determining the position of the obstacle (3), -determining at least one discrete obstacle position (31, 32) in one of the cells (1, 2, 6, 7, 8, 9) which have been provided that corresponds to the position of the obstacle (3), -changing the occupancy value or the occupancy probability of the at least one discrete obstacle position (31, 32) in such a manner that the presence of the obstacle (3) is indicated, and -changing at least one discrete intermediate position in at least one of the cells (1, 2, 6, 7, 8, 9) which have -20 -been provided between disorete obstacle position (31, 32) and discrete object position (40) in such a manner that these positions indicate a vacant environment in case at least one such discrete intermediate position is present.
2. Process according to Claim 1, comprising the -following steps: -defining an initial cell from the existing cells (1, 2, 6, 7, 8, 9) that exhibits no adjacent cell (1, 2, 6, 7, 8, 9) at least in one vacant direction (11, 12, 13, 14) -generating a further cell (1, 2, 6, 7, 8, 9) having the same features as the at least one cell (1, 2, 6, 7, 8, 9) which has beefi provided, comprising the following steps: -defining an identification of the further cell (1, 2, 6, 7, 8, 9), -storing the identification of the further cell (1, 2, 6, 7, 8, 9) in the initial cell by way of neighbourhood relationship in the vacant direction (11, 12, 13, 14), -defining a further direction in which the initial cell is situated, viewed from the further cell (1, 2, 6, 7, 8, 9), -storing the identification of the initial cell in the further cell (1, 2, 6, 7, 8, 9) by way of neighbourhood relationship in the further direction, and -providing items of occupancy information of the further cell (1, 2, 6, 7, 8, 9) that are formed by a spatial discretisation of the further cell (1, 2, 6, 7, 8, 9), whereby at each discrete point (10) a discrete occupancy value or an occupancy probability has been specified, -determining a discrete object position (40) within one of the cells (1, 2, 6, 7, 8, 9) which have.been generated or within one of the cells (1, 2, 6, 7, 8, 9) which have been provided that represents the current position of the object (4), -detecting an obstacle (3) in the environment of the object (4) and determining the position of the obstacle (3), -determining at least one discrete obstacle position (31, 32) within one of the cells (1, 2, 6, 7, 8, 9) which have been gene-rated or within one of the cells (1, 2, 6, 7, 8, 9) which have been provided that corresponds to the position of the obstacle (3), -changing the occupancy value or the occupancy probability of the at least one discrete obstacle position (31, 32) in such a manner that the presence of the obstacle (3) is indicated, and -changing at least one discrete intermediate position in at least one of the cells (1, 2, 6, 7, 8, 9) which have been provided and/or of the cells (1, 2, 6, 7, 8, 9) which have been generated between discrete obstacle position (31, 32) and discrete object position (40) in such a manner that these positions indicate a vacant environment in case at least one such intermediate position is present.
3. Process according to Claim 2, wherein the steps according to Claim 2 are implemented only when a discrete obstacle position (31, 32) in-one of the cells (1, 2, 6, -7, 8, 9) which have been provided or in one of the cells (1, 2, 6, 7, 8, 9) which have been generated cannot be determined.
4: Process according to one o the preceding claims, comprising the following steps: -providing precisely one cell (1, 2, 6, 7, 8, 9) which is designated as the master cell, -defining a discrete object position (40) within the master cell that corresponds to a current position of the object (4), and -defining a spatial discretisation, within which the items of occupancy information are to be represented.
5. Process according to one of the preceding claims, wherein the occupancy value encompasses the values "occupied", "vacant" and "unknown", and/or the occupancy probability is specified as a value between 0 and 1, where 0 corresponds to the value "vacant", 0.5 corresponds to the value "unknown", and 1 corresponds to the value "occupied".
6. Process according to Claim 5, comprising the following steps: -determining a number of items of occupancy information for each cell (1, 2, 6, 7, 8, 9) that do not contain the value "unknown", -deleting a cell (1,. 2, 6, 7, 8, 9) in which the number of items of occupancy information falls below a first value.
7. Process according to one of the preceding claims, wherein each cell (1, 2, 6, 7, 8, 9) exhibits a rectangular shape, in particular a square shape.-23 -
8. Process according to one of the preceding claims, wherein all the cells (1, 2, 6, 7, 8, 9) exhibit the same size or the cells (1, 2, 6, 7, 8, 9) exhibit differing sizes
9. Process according to one of the preceding claims, wherein each cell (1, 2, 6, 7, 8, 9) represents the environment two-dimensionally or three-dimensionally.
10. Process according to one of the preceding claims, comprising the following steps: -determining an absolute position of each cell (1, 2, 6, 7, 8, 9) within a fixed coordinate system on the basis of the neighbourhood relationships, -determining a group of cells (1, 2, 6, 7, 8, 9) that are situated at the same absolute position, -comparison of the items *of occupancy information of, in each instance, two cells (1, 2, 6, 7, 8, 9) from the group of cells, -merging the two cells (1, 2, 6, 7, 8, 9) from the group of cells to form one cell in case the items of occupancy information of the two cells are at least partly identical.
11. A process, for modelling an ambient field of an object, substantially as herein described with reference to the attached drawings.
12. Apparatus for modelling an ambient field of anobject (4), *in particular of a vehicle, comprising -a storage device (200), -at least one environment sensor (5) for detecting obstacles (3) in the environment of the object (4) , and -24 - -a control unit (100) which has been connected to the storage device (200) and to the environment sensor (5) wherein -the control unit (100) executes a process according to one cf Claims 1 to 11, and -the cells (1, 2, 6, 7, 8, 9) are stored within the storage device. -
13. Apparatus according to Claim 13, wherein -the storage device (200) has been set up to return, upon request for a new cell (1, 2, 6, 7, 8, 9) by the control unit (100), the identification of a cell (1, 2, 6, 7, 8, 9) from a first number of cells (1, 2, 6, 7, 8, 9) without occupancy information and neighbourhood relationships, -the storage device (200) has been set up to store always a second number of cells (1, 2, 6, 7, 8, 9) without occupancy information and neighbourhood relationships, and -the second number of cells (1, 2, 6, 7, 8, 9) is at least just as large as the first number of cells (1, 2, 6, 7, 8, 9).
14. An apparatus, for modelling an ambient field of an object, substantially as herein described with reference to the accompanying drawings.