Autonomous machine

• US 20050046373A1
• Filed: 10/31/2002
• Published: 03/03/2005
• Est. Priority Date: 11/03/2001
• Status: Active Grant

• Current Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Original Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Inventors: Aldred, Micheal David
• Granted Patent: US 7,053,580 B2
• Time in Patent Office: Days
• US Class Current: 318/580
• CPC Class Codes: A47L 2201/04 Automatic control of the travelling movement; Automatic obstacle detection
• CPC Class Codes: A47L 2201/06 Control of the cleaning action for autonomous devices; Automatic detection of the surface condition before, during or after cleaning
• CPC Class Codes: A47L 9/009 Carrying-vehicles; Arrangements of trollies or wheels; Means for avoiding mechanical obstacles
• CPC Class Codes: G05D 1/0242 using non-visible light signals, e.g. IR or UV signals
• CPC Class Codes: G05D 1/0255 using acoustic signals, e.g. ultra-sonic singals sonar systems designed for anti-collision purposes G01S15/93
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30

Abstract

An autonomous machine comprises driving means for moving the machine along a surface of an area, and a navigation system. The navigation system causes the machine to follow a boundary of the area, storing path information on the path travelled by the machine as the machine follows the boundary and compares when the machine has returned to a previously visited position in the area. The navigation system compares the latest section of the path travelled by the machine with information representing a section of the path previously stored in the memory and decides when the new path information and previously stored path information are substantially the same.

Claims

1. An autonomous machine comprising:

driving means for moving the machine along a surface of an area, and

a navigation system, including a memory means, for navigating the machine around the area,

the navigation system comprising;

boundary following means for causing the machine to follow a boundary of the area, storing path information on the path travelled by the machine as the machine follows the boundary;

comparison means for determining when the machine has returned to a previously visited position in the area, the comparison means being arranged to compare the latest section of the path travelled by the machine with information representing a section of the path previously stored in the memory, and for deciding when the new path information and previously stored path information are substantially the same.

2. An autonomous machine according to claim 1 wherein the path information is stored at regular intervals.

3. An autonomous machine according to claim 2 wherein the path information is stored at intervals which are spaced by an equal distance from one another.

4. An autonomous machine according to any one of the preceding claims wherein the path information is representative of the change in direction of the machine as the machine follows the boundary of the area.

5. An autonomous machine according to claim 4 wherein the path information is the relative change in direction of the machine compared to a previous point at which path information was stored.

6. An autonomous machine according to any one of the preceding claims wherein the navigation system is arranged to derive, from the stored path information, a second set of path information which is a less detailed representation of the travelled path.

7. An autonomous machine according to claim 6 wherein the comparison means is arranged to use the second set of path information in deciding whether the new path information and previously stored path information are substantially the same.

8. An autonomous machine according to any one of the preceding claims wherein the navigation system also comprises means for sensing another parameter and for storing this other parameter in the memory along with the path information as the machine follows the boundary of the area.

9. An autonomous machine according to claim 8 wherein the comparison means also uses, on at least some occasions, the other parameter to determine when the machine has returned to a previously visited position in the area.

10. An autonomous machine according to claim 8 or 9 wherein the other parameter is the absolute direction of the machine.

11. An autonomous machine according to any one of claims 8 to 10 wherein the other parameter is one or more of:

received light level and distance information.

12. An autonomous machine according to any one of the preceding claims wherein, if the comparison means fails to find a match between the new path information and previously stored path information, the comparison means is arranged to increase the length of the path section used by the comparison means.

13. An autonomous machine according to any one of the preceding claims wherein the navigation system is arranged to travel around the boundary of the area and the condition of new path information being substantially the same as previously stored information is used to indicate that the machine has completed a traverse of the boundary of the area.

14. An autonomous machine according to any one of the preceding claims wherein the navigation system is arranged to construct a map of the area and to add the path information to the map.

15. An autonomous machine according to claim 14 wherein, on determining that the machine has returned to a previously visited position on the boundary, the navigation system corrects the map.

16. An autonomous machine according to claim 14 or 15 wherein the navigation system is arranged to cause the machine to follow the boundary of the area after a period of operating away from the boundary, the comparison means being used to compare new path information from the path around the boundary with previously stored path information to decide when the two sets of path information are substantially the same and, upon detecting a match, to retrieve the position on the map corresponding to the matched path information.

17. An autonomous machine according to claim 16 wherein the navigation system is also arranged to update, on the map, the path travelled by the machine during the period of operating away from the boundary based on the error between the navigation system'"'"'s guess of the current position and the position which is retrieved from the map.

18. An autonomous machine according to any one of claims 14-17 wherein the navigation system uses the recognition of a previously visited location to update the position of the machine on the map.

19. An autonomous machine according to any one of claims 14-18 wherein the navigation system is arranged so that, once the map has been constructed, the system:

selects a starting point on the boundary from which to work in the area;

extracts the section of path information on the boundary preceding the selected starting point; and

causes the machine to travel along the boundary towards the starting point and to use the comparison means to compare new path information, as the machine follows the boundary, with the extracted section of path information so as to find the starting point.

20. An autonomous machine according to any one of the preceding claims comprising means for deriving odometry data and wherein the path information is derived from the odometry data.

21. An autonomous machine according to 20 wherein the comparison means comprises:

means for maintaining an indication of the reliability of the new path information as the machine travels around the area, the reliability decreasing with the distance travelled by the machine since the last reset;

and wherein the comparison means is arranged to use the indication in comparing new path information with stored path information.

22. A method of controlling an autonomous machine comprising:

causing the machine to follow a boundary of the area, storing path information on the path travelled by the machine as the machine follows the boundary;

determining when the machine has returned to a previously visited position in the area by comparing the latest section of the path travelled by the machine with information representing a section of the path previously stored in the memory, and deciding when the new path information and previously stored path information are substantially the same.

23. Software for controlling an autonomous machine to perform the method according to claim 22.

24. An autonomous machine, a method of controlling an autonomous machine or software method for controlling an autonomous machine substantially as described herein with reference to the accompanying drawings.