Method and device for determining position of an autonomous apparatus

• US 20040193339A1
• Filed: 05/13/2004
• Published: 09/30/2004
• Est. Priority Date: 03/15/2001
• Status: Active Grant

• Current Assignee: Aktiebolaget Electrolux
• Original Assignee: Aktiebolaget Electrolux
• Inventors: Hulden, Jarl
• Granted Patent: US 7,248,951 B2
• Time in Patent Office: Days
• US Class Current: 701/23
• CPC Class Codes: G05D 1/0225 involving docking at a fixed facility, e.g. base station or loading bay parking aids B62D15/027
• 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 2201/0215 Vacuum cleaner

Abstract

A carrier, such as an autonomous surface treatment device, e.g., a robotic vacuum cleaner, has motive units, such as wheels, for transporting the carrier over a field of operation. The state of the carrier, which can be its position on the field of operation, is determined based, at least in part, on the actual track width of the motive units which will change depending on the carriers driving mode. For example, when the carrier is operating in a driving mode where it is turning, the actual track width of the motive units will be different from the actual track width of those units when the carrier is proceeding straight ahead. A determination is made of the driving mode in which the carrier is operating at the time its state is to be determined, and the actual track width of the motive units that corresponds to that driving mode is employed in determining the state of the carrier.

Claims

1. A method of determining the state of a carrier on a field of operation, the carrier having means comprising two oppositely disposed motive units for transporting it over the field of operation, comprising employing the actual track width of the motive units as a determinant, at least in part, of the state of the carrier, relating one or more potential driving modes for the carrier to the respective actual track widths that result when the carrier operates in those modes, determining the driving mode in which the carrier is operating at the time its state is to be determined, and applying the actual track width that corresponds to that driving mode in determining the state of the carrier.

2. The method of claim 1 wherein the motive units comprise wheels that are arranged to be driven independently of one another.

3. The method of claim 2 wherein a driving mode employed is defined by the overlap of a range of rotational velocities for each wheel.

4. The method of claim 2 wherein a driving mode employed is defined by a range of rotational velocities for only one of the wheels.

5. The method of claim 2 wherein a driving mode employed is defined by a single ratio between the rotational velocities of the two wheels.

6. The method of claim 2 wherein a driving mode employed is defined by a range of ratios between the rotational velocities of the two wheels.

7. The method of claim 2 wherein five driving modes are employed, a first mode being defined by both wheels having equal rotational velocities in a direction tending to move the carrier in a forward direction, second and third modes being defined, respectively, by the rotation of one wheel in one direction or the other and the rotation of the other wheel in the opposite direction at the same rotational velocities, and a fourth and fifth modes being defined, respectively, by the rotation at one rotational velocity of one or the other of the wheels in a direction tending to move the carrier forward either alone or together with the rotation in the same direction at a lower rotational velocity of the other of the wheels.

8. The method of claim 1 wherein the state of the carrier to be determined is the position of the carrier on the field of operation.

9. The method of claim 8 wherein the carrier is an autonomous vacuum cleaner.

10. The method of claim 9 wherein the motive units comprise wheels that are arranged to be driving independently of one another.

11. The method of claim 10 wherein a driving mode employed is defined by the overlap of a range of rotational velocities for each wheel.

12. The method of claim 10 wherein a driving mode employed is defined by a range of rotational velocities for only one of the wheels.

13. The method of claim 10 wherein a driving mode employed is defined by a single ratio between the rotational velocities of the two wheels.

14. The method of claim 10 wherein a driving mode employed is defined by a range of ratios between the rotational velocities of the two wheels.

15. The method of claim 10 wherein five driving modes are employed, a first mode being defined by both wheels having equal rotational velocities in a direction tending to move the carrier in a forward direction, second and third modes being defined, respectively, by the rotation of one wheel in one direction or the other and the rotation of the other wheel in the opposite direction at the same rotational velocities, and a fourth and fifth modes being defined, respectively, by the rotation at one rotational velocity of one or the other of the wheels in a direction tending to move the carrier forward either alone or together with the rotation in the same direction at a lower rotational velocity of the other of the wheels.

16. The method of claim 2 wherein the procedure of relating potential driving modes to actual track widths that result when the carrier operates in those modes includes the steps of aligning the carrier in an initial known direction, driving the carrier in accordance with a driving mode, determining the angle through which the carrier has turned while being driven in that driving mode, determining the distance each of the wheels has travelled while the carrier turned through that angle, and calculating the actual track width for that driving mode based on the distance and angle determinations.

17. The method of claim 16 wherein said calculating step comprises calculating an approximate angle through which it is estimated the carrier has turned based on the distance determinations for the wheels and an assumed track width, calculating the difference between the approximate angle and the determined angle, and calculating the actual track width as a correction to the assumed track width based on that difference.

18. The method of claim 16 wherein the state of the carrier to be determined is the position of the carrier on the field.

19. The method of claim 18 wherein the carrier is an autonomous vacuum cleaner.

20. The method of claim 19 wherein a driving mode employed is defined by the overlap of a range of rotational velocities for each wheel.

21. The method of claim 19 wherein a driving mode employed is defined by a range of rotational velocities for only one of the wheels.

22. The method of claim 19 wherein a driving mode employed is defined by a single ratio between the rotational velocities of the two wheels.

23. The method of claim 19 wherein a driving mode employed is defined by a range of ratios between the rotational velocities of the two wheels.

24. A carrier having means comprising two oppositely disposed motive units for transporting the carrier over a field of operation, the carrier having the capability of operating in one or more driving modes, means for determining the driving mode of the carrier, and means for calculating the position of the carrier on the field of operation based on the actual track width of the motive units that corresponds to the driving mode that has been determined and the respective distances the motive units have moved.

25. The carrier of claim 24 wherein the carrier comprises an autonomous vacuum cleaner.

26. The carrier of claim 24 wherein the motive units comprise wheels that are arranged to be driven independently of one another.

27. The carrier of claim 26 wherein the carrier comprises an autonomous vacuum cleaner.

28. The carrier of claim 24 and including means for aligning the carrier in a known direction, means for determining the angle through which the carrier turns when operating in a driving mode, and means for calculating an actual track width associated with that driving mode based on the angle through which the carrier turns and the respective distances the motive units move when the carrier moves through that angle.

29. The carrier of claim 28 wherein the carrier comprises an autonomous vacuum cleaner.

30. The carrier of claim 28 wherein the motive means comprises wheels that are arranged to be driven independently of one another.

31. The carrier of claim 30 wherein the carrier comprises an autonomous vacuum cleaner.

32. A position determination system for a carrier having two oppositely disposed motive units and capable of operating in one or more driving modes, comprising means for determining the driving mode of the carrier, and means for calculating the position of the carrier on a field of operation based on the actual track width of the motive units that corresponds to the driving mode that has been determined and the respective distances the motive units have moved.

33. The position determination system of claim 32 wherein the carriers motive units comprise wheels that are arranged to be driven independently of one another, and including means to register the respective rotations of the wheels for the purpose of enabling the velocities of the wheels to be determined.

34. The position determination system of claim 33 wherein the carrier is an autonomous vacuum cleaner.

35. A position calibration system for a carrier having two oppositely disposed motive units and capable of operating in one or more driving modes, comprising means for aligning the carrier in a known direction, means for causing the carrier to proceed in accordance with a selected driving mode, means for determining the angle through which the carrier turns as it proceeds in the selected driving mode, and means for calculating the actual track width for the selected driving mode as a function of the determined angle and the respective distances the motive units have travelled.

36. The system of claim 35 wherein the calculating means includes expectation means for calculating an expected turning angle for the carrier based on an assumed track width, difference means for calculating the difference between the turning angle actually determined and the expected turning angle, and means for determining a correction for the assumed track width based on that difference whereby the assumed track width is calibrated to correspond to the actual track width.

37. The system of claim 36 wherein the motive units comprise wheels that are arranged to be driven independently of one another and the carrier is an autonomous vacuum cleaner.