IL290838B2 - Path planning within a traversed area - Google Patents

Description

PATH PLANNING WITHIN A TRAVERSED AREA TECHNICAL FIELD The presently disclosed subject matter relates to autonomic path planning.

BACKGROUND An unmanned vehicle, also referred to as an uncrewed vehicle or an unmanned ground vehicle (UGV) is a motorized machine that travels and operates autonomously. A UGV can be useful for applications such as moving within areas which are inconvenient, dangerous, or not possible for humans to enter, for bringing supplies or machinery, performing dangerous missions, or the like.

One issue, related to the operation of UGVs, concerns autonomous planning of a path from a starting point, such as a current location of a UGV, to a certain destination, in particular when the area to be traversed comprises unpassable obstacles or problematic areas which should be avoided.

GENERAL DESCRIPTION The disclosure relates to the autonomous planning of a path for a UGV, and to steering of the UGV in accordance with the path. The path is planned in accordance with a given map of the area, and the path accuracy depends, inter alia, on the resolution and accuracy of the map.

In some applications, such as planning a path for a UGV, the map can be generated based on data received from one or more sensors mounted on the UGV, and represent an area surrounding the UGV. The map can thus be updated as the UGV advances, for example, at an update frequency between 1 and 1200 updates per second, and the path can be updated in turn in accordance with at least some of the updated maps. Since the UGV can be in continuous movement during the path planning, the path needs to be planned in real-time or near-real-time to avoid collision with obstacles, avoid delaying the progress of the vehicle, and avoid other problems resulting from advancement of the UGV in accordance with an outdated map.

According to some examples of the presently disclosed subject matter, planning a path comprises determining or receiving a starting point on the map, for example a point representing a current location of the UGV, and adding segments of a predetermined length from the starting point, in a multiplicity of directions at a first angular resolution, such as every 8, every 15, every 30 or the like. If any of the segments collides with an obstacle, the segment is disregarded, and a multiplicity of other segments are added starting at the starting point, at a higher angular resolution, such as every 2, every 5, every 15, respectively, in the vicinity of the angle of the segment to be disregarded. For example, if the colliding segment is at an angle x, in respect to the previous segment, or to a straight line connecting the current location of the UGV with the destination, the other segments can be added at angles x-5, x-3, x-0, x+1, etc. Each such segment forms a path, where each of the paths in which the segment does not hit an obstacle is assigned a weight, and the path having the lowest weight is selected. The process is then repeated by adding segments in a multiplicity of directions, starting at the end point of the segment of the selected path, thus forming a plurality of two-segment paths. These paths are added to the collection of previous paths, which comprises the previously generated paths which were not selected. Once segments have been added to the selected path, a weight is assigned to each path, including the paths created but not selected at an earlier stage. The path having the lowest weight is then selected.

The process continues by adding segments to the end point of the selected path, assigning a weight to each path, and selecting the path with the lowest weight, until a stopping criterion is met, such as a predetermined time has elapsed. The UGV is then steered in accordance with the path having the lowest weight.

Assigning a weight to a path can take into account various factors, such as proximity of the end point of the path to the destination, number of segments, turning angles between segments, proximity of the path to obstacles, passing through allowed but undesired areas, slopes encountered along the path, deviation from recognized roads (which may be an advantage or a disadvantage), passing through waypoints, or the like.

In some examples, a multiplicity of such collections of paths are created, each using different angle densities. For example, each collection may be generated by a different core or processor. Once the collections are generated, one path is selected from each collection. Of all selected paths, the one having the lowest weight is selected and the UGV is steered in accordance therewith.

Thus, an aspect of the disclosed subject matter relates to a method of autonomous path planning for navigating a vehicle, the method comprising using one or more computer processing devices for receiving data indicative of a map of an area, a starting point and a destination; forming a multiplicity of paths, each path comprising a first segment starting at the starting point, each first segment proceeding at one of a multiplicity of directions, the multiplicity of directions fanned out at a first angular resolution; for each segment colliding with an obstacle indicated on the map, determining additional segments starting at the starting point and proceeding at a multiplicity of other directions fanned out at a second angular resolution, the second angular resolution being higher than the first angular resolution; assigning a weight to each of the multiplicity of paths and selecting a selected path from the multiplicity of paths in accordance with the weight, the selected path having an end point; while a stopping criterion has not been met: adding to the multiplicity of paths a further multiplicity of paths, each consisting of the selected path and one of a multiplicity of segments starting at the end point, each of the multiplicity of segments directed at one of the multiplicity of directions fanned out at the first angular resolution, and for each segment that collides with an obstacle indicated on the map. adding an additional multiplicity of paths comprising the selected path and additional segments starting at the end point, the additional segments directed at a multiplicity of other directions fanned out at the second angular resolution, such that each of the additional multiplicity of paths comprises the selected path and one of the additional segments; assigning a weight to each of the further multiplicity of paths and additional multiplicity of paths that does not collide with an obstacle; and upon meeting the stopping criterion, selecting a selected path from the multiplicity of paths, in accordance with the weight; and generating steering instructions for steering the UGV in accordance with the selected path.

In addition to the above features, the method according to this aspect of the presently disclosed subject matter can optionally comprise one or more of features (i) to (xiii) listed below, in any technically possible combination or permutation: i. Wherein the weight assigned to each path of the multiplicity of paths is determined in accordance with at least one non-angular factor. ii. Wherein the at least one non-angular factor is selected from the group consisting of: proximity of the path to an obstacle; slopes along the path; intersection of the path with areas not recommended for passing; and deviation from recognized roads. iii. Wherein the selected path is selected as a path from a multiplicity of paths having a lowest absolute weight. iv. Wherein the selected path is selected as a path from the multiplicity of paths having a lowest weight per segment. v. The method further comprising creating a second multiplicity of paths, using another first angular resolution different from the first angular resolution, or another second angular resolution different from the second angular resolution, and selecting a second selected path from the second multiplicity of paths; and generating steering instructions for steering the UGV with a path selected from the selected path and the second selected path. vi. Wherein the first angular resolution and the second angular resolution are lower than the other first angular resolution and the other second angular resolution, respectively, wherein the selected path is selected from the multiplicity of paths in accordance with a lowest absolute weight, and wherein the second selected path is selected from the second multiplicity of paths in accordance with a lowest weight per segment. vii. Wherein the multiplicity of paths and the second multiplicity of paths are generated by different cores. viii. Wherein the weight assigned to each path of the multiplicity of paths is determined in accordance with smoothness of the path and proximity of an end point of the path to a destination. ix. Wherein the map is generated upon scanning data received from a scanning device mounted on the vehicle. x. Wherein the stopping criterion is an elapsed time period. xi. The method further comprising receiving at least one waypoint, wherein the weight assigned to each path of the multiplicity of paths is determined also in accordance with a distance of the path from each of the at least one waypoint. xii. The method further comprising steering the UGV in accordance with the steering instructions. xiii. Wherein any previously selected paths are excluded from selection of the selected path from the multiplicity of paths.

According to another aspect of the presently disclosed subject matter there is provided a method of navigating an autonomous vehicle using path planning, the method comprising using at least one computer processing device for receiving data indicative of a map of an area, a starting point, and a destination; forming a multiplicity of paths, each path comprising a first segment starting at the starting point, each first segment proceeding at one of a multiplicity of directions having a first angular resolution; for each segment colliding with an obstacle indicated on the map, ignoring the segment and determining additional segments starting at the starting point and proceeding in a multiplicity of other directions having a second angular resolution, the second angular resolution being higher than the first angular resolution; assigning a weight to each of the multiplicity of paths; and selecting a selected path from the multiplicity of paths in accordance with the weight, the selected path having an end point; while a stopping criterion has not been met: adding to the multiplicity of paths a further multiplicity of paths, each consisting of the selected path and one of a multiplicity of segments starting at the end point, each of the multiplicity of segments directed at one of the multiplicity of directions having the first angular resolution, and for each segment that collides with an obstacle indicated on the map, adding an additional multiplicity of paths comprising the selected path and additional segments starting at the end point, the additional segments directed at a multiplicity of other directions having the second angular resolution, such that each of the additional multiplicity of paths comprises the selected path and one of the additional segments; assigning a weight to each of the further multiplicity of paths and additional multiplicity of paths that does not collide with an obstacle; and, upon meeting the stopping criterion, selecting a selected path from the multiplicity of paths in accordance with the weight; and steering the UGV in accordance with the selected path.

The method disclosed in accordance with the aspects of the presently disclosed subject matter detailed above can optionally comprise one or more of features (i) to (xiii) listed above, mutatis mutandis, in any technically possible combination or permutation.

According to another aspect of the presently disclosed subject matter there is provided an unmanned ground vehicle (UGV), comprising a scanning device for scanning an area surrounding the UGV, to thereby provide scanning output data providing information on distances between objects in the area and the UGV in a multiplicity of directions; a map obtaining module for receiving a map of the area, the map generated upon scanning output data received from the scanning device; a destination receiving module for receiving a destination to which the UGV has to steer; a vehicle control sub-system configured to receive vehicle control instructions and control the UGV in accordance with the instructions; and a processor configured to receive data indicative of a map of an area to be navigated, a starting point and a destination; forming by a processor a multiplicity of paths, each consisting of a first segment starting at the starting point, each first segment proceeding at one of a multiplicity of directions having a first angular resolution; for each segment having a common point with an obstacle indicated on the map, ignoring the segment and determining additional segments starting at the starting point and proceeding in a multiplicity of other directions having a second angular resolution, the second angular resolution being higher than the first angular resolution; assigning a weight to each of the multiplicity of paths; and selecting a selected path from the multiplicity of paths in accordance with the weight, the selected path having an end point; while a stopping criterion has not been met: adding to the multiplicity of paths a further multiplicity of paths, each consisting of the selected path and one of a multiplicity of segments starting at the end point, each of the multiplicity of segments directed at one of the multiplicity of directions having the first angular resolution, and for each segment that collides with an obstacle indicated on the map, adding an additional multiplicity of paths comprising the selected path and additional segments starting at the end point, the additional segments directed at a multiplicity of other directions having the second angular resolution, such that each of the additional multiplicity of paths comprises the selected path and one of the additional segments; assigning a weight to each of the further multiplicity of paths and additional multiplicity of paths, that does not collide with an obstacle; and, upon meeting the stopping criterion, selecting a selected path from the multiplicity of paths in accordance with the weight; and generating steering instructions for steering the UGV in accordance with the selected path.

The UGV disclosed in accordance with the aspects of the presently disclosed subject matter detailed above can optionally comprise one or more of features (i) to (xiii) listed above, mutatis mutandis, in any technically possible combination or permutation.

According to another aspect of the presently disclosed subject matter there is provided a system mountable on a UGV, comprising a processor configured to receive data indicative of a map of an area to be navigated, a starting point and a destination; forming by a processor a multiplicity of paths, each consisting of a first segment starting at the starting point, each first segment proceeding at one of a multiplicity of directions having a first angular resolution; for each segment having a common point with an obstacle indicated on the map, ignoring the segment and determining by the processor additional segments starting at the starting point and proceeding in a multiplicity of other directions having a second angular resolution, the second angular resolution being higher than the first angular resolution; assigning, by the processor, a weight to each of the multiplicity of paths; and selecting, by the processor, a selected path from the multiplicity of paths in accordance with the weight, the selected path having an end point; while a stopping criterion has not been met: adding to the multiplicity of paths a further multiplicity of paths, each consisting of the selected path and one of a multiplicity of segments starting at the end point, each of the multiplicity of segments directed at one of the multiplicity of directions having the first angular resolution, and for each segment that collides with an obstacle indicated on the map, adding an additional multiplicity of paths comprising the selected path and additional segments starting at the end point, the additional segments directed at a multiplicity of other directions having the second angular resolution, such that each of the additional multiplicity of paths comprises the selected path and one of the additional segments; assigning, by the processor, a weight to each of the further multiplicity of paths and additional multiplicity of paths, that does not collide with an obstacle; and upon meeting the stopping criterion, selecting by the processor a selected path from the multiplicity of paths in accordance with the weight; and generating steering instructions for steering the UGV in accordance with the selected path.

The system disclosed in accordance with the aspects of the presently disclosed subject matter detailed above can optionally comprise one or more of features (i) to (xiii) listed above, mutatis mutandis, in any technically possible combination or permutation.

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it can be carried out in practice, embodiments will be described, by way of non-limiting examples, with reference to the accompanying drawings, in which: Fig. 1 illustrates a schematic block diagram of a UGV with automatic path planning, in accordance with certain examples of the presently disclosed subject matter; Fig. 2 illustrates a schematic illustration of an environment in which a UGV has to navigate; Fig. 3 illustrates a generalized flow-chart of a method for path planning, in accordance with certain examples of the presently disclosed subject matter; Fig. 4 A provides a first graphical demonstration of a path planning example, in accordance with certain examples of the presently disclosed subject matter; and Figs. 4B-4F provide a second graphical demonstration of a path planning example, in accordance with certain examples of the presently disclosed subject matter.

Claims (49)

1.CLAIMS: 1. A method of autonomous path planning for navigating a vehicle, the method comprising: receiving data indicative of a map of an area to be traversed; processing the map to determine a selected path leading to a desired destination, comprising: defining a current point on the map; while a stopping criterion has not been met, generating a collection of paths: determining a plurality of segments fanning out from the current point in a first angular resolution, each of the plurality of segments proceeding at one of a multiplicity of directions; if a segment intersects an obstacle on the map, determining further segments fanning out from the current point in a second angular resolution that is higher than the first angular resolution; determining a plurality of paths, each path comprising a previously selected path, if such exists, and one of the plurality of segments; adding the plurality of paths to the collection of paths; selecting a selected path from the collection of paths; defining an end point of the selected path as the current point; once the stopping criterion is met generating steering instructions for steering the vehicle, in accordance with the selected path.

2. The method of claim 1 further comprising: assigning a respective weight to each path in the collection of paths; and performing the selecting of a selected path according to the assigned weights.

3. The method of claim 2, wherein the selected path from the collection of paths is a path having a lowest weight.

4. The method of claim 2, wherein the selected path from the collection of paths is a path having a lowest weight per segment.

5. The method of any one of the preceding claims wherein the current point is defined as the current position of the vehicle on the map.

6. The method of any one of the preceding claims further comprising: generating a second collection of paths and selecting a second selected path therefrom, wherein the second collection of paths is generated using another first angular resolution different from the first angular resolution, and/or another second angular resolution different from the second angular resolution; generating steering instructions for steering the vehicle according to a path selected from the selected path and the second selected path.

7. The method of claim 6, wherein the first angular resolution and the second angular resolution are lower than the another first angular resolution and the another second angular resolution, respectively.

8. The method of any one of claims 6 and 7, wherein the collection of paths and the second collection of paths are each generated by different cores.

9. The method of any one of claims 1 to 5 further comprising: using at least one computer processing device that comprises at least a first core and a second core, and: using the first core for determining the selected path; using the second core for determining a second selected path, selected from a second collections of paths that is generated using another first angular resolution different from the first angular resolution, and/or another second angular resolution different from the second angular resolution; generating steering instructions for steering the vehicle according to a path selected from the selected path and the second selected path.

10. The method of any one of the preceding claims further comprising: generating the map based on scanning data received from a scanning device mounted on the vehicle.

11. The method of any one of the preceding claims, wherein the stopping criterion is an elapsed time period.

12. The method of any one of the preceding claims further comprising: receiving one or more waypoints, wherein the weight assigned to each path of the collection of paths is determined in accordance with a distance of the path from at least one of the one or more waypoints.

13. The method of any one of the preceding claims further comprising, steering the vehicle in accordance with the steering instructions.

14. The method of any one of the preceding claims, wherein a segment that interests with an obstacle on the map is ignored and not selected.

15. The method of any one of the preceding claims, wherein the weight assigned to each path of the collection of paths is determined in accordance with at least one non-angular factor.

16. The method of claim 15 wherein the at least one non-angular factor is selected from a group comprising: proximity of the path to an obstacle; slopes along the path; intersection of the path with areas not recommended for passing; and deviation from recognized roads.

17. The method of any one of claims 1 to 14, wherein the weight assigned to each path of the collection of paths is determined in accordance with smoothness of the path and proximity of an end point of the path to a destination.

18. The method of any one of claims 1 to 5 further comprising: using at least one computer processing device that comprises a first core and one or more additional cores, and: using the first core for determining the selected path; using each one of the one or more additional cores for determining a respective selected path, thereby giving rise to one or more additional selected paths; wherein each respective path is selected from a respective collection of paths that is generated using a unique respective first angular resolution, and/or a unique respective second angular resolution; generating steering instructions for steering the vehicle according to a path selected from the selected path and the one or more additional selected paths.

19. A method of navigating an autonomous vehicle using real-time path planning, the method comprising: receiving data indicative of a map of an area to be traversed; processing the map to determine a selected path leading to a desired destination, comprising: defining a current point on the map; while a stopping criterion has not been met, generating a collection of paths: determining a plurality of segments fanning out from the current point in a first angular resolution, each of the plurality of segments proceeding at one of a multiplicity of directions; if a segment intersects an obstacle on the map, determining further segments fanning out from the current point in a second angular resolution that is higher than the first angular resolution; determining a plurality of paths, each path comprising a previously selected path, if such exists, and one of the plurality of segments; adding the plurality of paths to the collection of paths; selecting a selected path from the collection of paths; defining an end point of the selected path as the current point; once the stopping criterion is met navigating the vehicle the area, in accordance with the selected path.

20. The method of claim 19 further comprising: generating the map based on scanning data received from a scanning device mounted on the vehicle.

21. The method of any one of claims 19 and 20 further comprising: using at least one computer processing device that comprises at least a first core and a second core, and: using the first core for determining the selected path; using the second core for determining a second selected path, selected from a second collections of paths, using another first angular resolution different from the first angular resolution, and/or another second angular resolution different from the second angular resolution; generating steering instructions for steering the vehicle according to a path selected from the selected path and the second selected path.

22. A system mountable on a vehicle comprising at least one computer processing device configured to: obtain a map of an area to be traversed; process the map to determine a selected path leading to a desired destination, comprising: define a current point on the map; while a stopping criterion has not been met, generate a collection of paths: determine a plurality of segments fanning out from the current point in a first angular resolution, each of the plurality of segments proceeding at one of a multiplicity of directions; if a segment intersects an obstacle on the map, determine further segments fanning out from the current point in a second angular resolution that is higher than the first angular resolution; determine a plurality of paths, each path comprising a previously selected path, if such exists, and one of the plurality of segments; add the plurality of paths to the collection of paths; select a selected path from the collection of paths; define an end point of the selected path as the current point; once the stopping criterion is met generate steering instructions for steering the vehicle, in accordance with the selected path.

23. The system of claim 22, wherein the at least processing device is configured to: assign a respective weight to each path in the collection of paths; and select of a selected path according to the assigned weights.

24. The system of claim 23, wherein selected path from the collection of paths is a path having a lowest weight.

25. The system of claim 23, wherein the selected path from the collection of paths is a path having a lowest weight per segment.

26. The system of any one of claims 22 to 25, wherein the current point is defined as the current position of the vehicle on the map.

27. The system of any one of claims 22, wherein the at least one processing device is configured to: generate a second collection of paths and select a second selected path therefrom, wherein the second collection of paths is generated using another first angular resolution different from the first angular resolution, and/or another second angular resolution different from the second angular resolution; generate steering instructions for steering the vehicle according to a path selected from the selected path and the second selected path.

28. The system of claim 27, wherein the first angular resolution and the second angular resolution are lower than the another first angular resolution and the another second angular resolution, respectively.

29. The system of any one of claims 26 and 27, wherein the collection of paths and the second collection of paths are each generated by different cores.

30. The system of any one of claims 22 to 26, wherein the at least one processing device comprises at least a first core and a second core, wherein the first core is configured to determine the selected path and the second core is configured to generate a second collection of paths and select a second selected path therefrom, wherein the second collection of paths is generated using another first angular resolution different from the first angular resolution, and/or another second angular resolution different from the second angular resolution; the at least one processing device is configured to generate steering instructions for steering the vehicle according to a path selected from the selected path and the second selected path.

31. The system of any one of claim 22 to 30, wherein the at least one processing device is configured to generate the map based on scanning data received from a scanning device mounted on the vehicle.

32. The system of any one of claims 22 to 31, wherein the stopping criterion is an elapsed time period.

33. The system of any one of claims 22 to 32, wherein the at least one processing is configured to receive one or more waypoints, wherein the weight assigned to each path of the collection of paths is determined in accordance with a distance of the path from at least one of the one or more waypoints.

34. The system of any one of claims 22 to 33, wherein a segment that interests with an obstacle on the map is ignored and not selected.

35. The system of any one of claims 22 to 33, wherein the weight assigned to each path of the collection of paths is determined in accordance with at least one non- angular factor.

36. The system of claims 35, wherein the at least one non-angular factor is selected from a group comprising: proximity of the path to an obstacle; slopes along the path; intersection of the path with areas not recommended for passing; and deviation from recognized roads.

37. The system of any one of claims 22 to 36, wherein the at least one computer processing device comprises a first core and one or more additional cores, wherein the first core is configured to determine the selected path and each one of the one or more additional cores is configured to determine a respective selected path, thereby giving rise to one or more additional selected paths; wherein each respective path is selected from a respective collection of paths that is generated using a unique respective first angular resolution, and/or a unique respective second angular resolution; the at least one processing device is configured to generate steering instructions for steering the vehicle according to a path selected from the selected path and the one or more additional selected paths.

38. The system of any one of claims 22 to 37, wherein the vehicle is an unmanned manned vehicle.

39. An unmanned vehicle, comprising: a scanning device for scanning an area surrounding the vehicle, to thereby provide scanning output data, wherein a map of the area is generated based on the scanning output data; a vehicle control sub-system configured to receive vehicle control instructions and control the vehicle in accordance with the instructions; and at least one computer processing device configured to: process the map to determine a selected path leading to a desired destination, comprising: define a current point on the map; while a stopping criterion has not been met, generate a collection of paths: determine a plurality of segments fanning out from the current point in a first angular resolution, each of the plurality of segments proceeding at one of a multiplicity of directions; if a segment intersects an obstacle on the map, determine further segments fanning out from the current point in a second angular resolution that is higher than the first angular resolution; determine a plurality of paths, each path comprising a previously selected path, if such exists, and one of the plurality of segments; add the plurality of paths to the collection of paths; select a selected path from the collection of paths; define an end point of the selected path as the current point; once the stopping criterion is met generate steering instructions for steering the vehicle, in accordance with the selected path.

40. The vehicle of claim 39, wherein the at least processing device is configured to: assign a respective weight to each path in the collection of paths; and select of a selected path according to the assigned weights.

41. The vehicle of any one of claims 39 and 40, wherein the at least one processing device is configured to: generate a second collection of paths and selecting a second selected path therefrom, wherein the second collection of paths is generated using another first angular resolution different from the first angular resolution, and/or another second angular resolution different from the second angular resolution; generate steering instructions for steering the vehicle according to a path selected from the selected path and the second selected path.

42. The vehicle of claim 41, wherein the first angular resolution and the second angular resolution are lower than the another first angular resolution and the another second angular resolution, respectively.

43. The vehicle of any one of claims 39 to 42, wherein the at least one processing device comprises at least a first core and a second core, wherein the first core is configured to determine the selected path and the second core is configured to determine a second selected path; wherein the second selected path is selected from a second collection of paths generated using another first angular resolution different from the first angular resolution, and/or another second angular resolution different from the second angular resolution; the at least one processing device is configured to generate steering instructions for steering the vehicle according to a path selected from the selected path and the second selected path.

44. The vehicle of any one of claims 39 to 43, wherein the stopping criterion is an elapsed time period.

45. The system of any one of claims 22 to 33, wherein a segment that interests with an obstacle on the map is ignored and not selected.

46. The vehicle of any one of claims 39 to 42, wherein the at least one processing device comprises at least a first core and a second core, wherein the first core is configured to determine the selected path and the second core is configured to generate a second collection of paths and select a second selected path therefrom, wherein the second collection of paths is generated using another first angular resolution different from the first angular resolution, and/or another second angular resolution different from the second angular resolution; the at least one processing device is configured to generate steering instructions for steering the vehicle according to a path selected from the selected path and the second selected path.

47. The system of any one of claims 39 to 46 vehicle is an unmanned ground vehicle.

48. A non-transitory computer readable storage medium tangibly embodying a program of instructions that, when executed by a computer, causing the computer to perform a method comprising: receiving data indicative of a map of an area to be traversed by a vehicle; processing the map to determine a selected path leading to a desired destination, comprising: defining a current point on the map; while a stopping criterion has not been met, generating a collection of paths: determining a plurality of segments fanning out from the current point in a first angular resolution, each of the plurality of segments proceeding at one of a multiplicity of directions; if a segment intersects an obstacle on the map, determining further segments fanning out from the current point in a second angular resolution that is higher than the first angular resolution; determining a plurality of paths, each path comprising a previously selected path, if such exists, and one of the plurality of segments; adding the plurality of paths to the collection of paths; selecting a selected path from the collection of paths; defining an end point of the selected path as the current point; once the stopping criterion is met generating steering instructions for steering the vehicle, in accordance with the selected path.

49. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of any one of claims 1 to 18. 20