System and Method for Coordinating Movement of Mobile Drive Units

• US 20130204480A1
• Filed: 03/14/2013
• Published: 08/08/2013
• Est. Priority Date: 06/19/2006
• Status: Active Grant

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Inventors: D'Andrea, Raffaello, Wurman, Peter R., Barbehenn, Michael T., Hoffman, Andrew E., Mountz, Michael C.
• Granted Patent: US 9,740,212 B2
• Time in Patent Office: Days
• US Class Current: 701/25
• CPC Class Codes: G05B 19/41895 using automatic guided vehicles [AGV] control of position or course of AGV's G05D1/00
• CPC Class Codes: G05B 2219/31003 Supervise route, reserve route and allocate route to vehicle, avoid collision
• CPC Class Codes: G05B 2219/45056 Handling cases, boxes
• CPC Class Codes: G05D 1/0212 with means for defining a desired trajectory involving a plurality of land vehicles G05D1/0287
• CPC Class Codes: G05D 1/0291 Fleet control monitoring fleets in traffic control systems for road vehicles G08G1/127, G08G1/127
• CPC Class Codes: G05D 1/0297 by controlling means in a control room
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]
• CPC Class Codes: Y02P 90/60 Electric or hybrid propulsion means for production processes

Abstract

A method for moving one or more mobile drive units within a workspace includes receiving, from a first mobile drive unit, a reservation request requesting use of a first path segment to move in a first direction. The method further includes determining that a second mobile drive unit is currently located on the first path segment and determining whether the second mobile drive unit is moving in the first direction. Additionally, the method includes transmitting a reservation response indicating that the reservation request is denied, in response to determining that the second mobile drive unit is not moving in the first direction. The method also includes transmitting a reservation response indicating that the reservation request is granted, in response to determining that the second mobile drive unit is moving in the first direction.

Claims

1-17. -17. (canceled)

18. A method, comprising:

receiving, by a management module and from a first mobile drive unit, a reservation request requesting use of a first path segment to move in a first direction;

determining, by the management module, that a second mobile drive unit is currently located on the first path segment;

determining, by the management module, whether the second mobile drive unit is moving in the first direction; and

in response to determining that the second mobile drive unit has reserved the first path segment and is moving in the first direction, transmitting, by the management module, a reservation response indicating that the reservation request is granted, wherein the granted reservation request allows movement of the first mobile drive unit and the second mobile drive unit on the first path segment at a substantially same time on different portions of the first path segment and the first path segment comprises a portion of a path requested by the reservation request.

19. The method of claim 18, further comprising:

in response to determining that the second mobile drive unit is not moving in the first direction, transmitting, by the management module, a reservation response indicating that the reservation request is denied.

20. The method of claim 18, further comprising:

receiving, by the first mobile drive unit, the reservation response;

in response to receiving the reservation response, determining, by the first mobile drive unit, whether the reservation request was granted; and

in response to determining that the reservation request was granted, moving, by the first mobile drive unit, across the first path segment in the first direction.

21. The method of claim 20, further comprising:

in response to determining that the reservation request was denied, waiting, by the first mobile drive unit, a predetermined amount of time; and

after waiting the predetermined amount of time, transmitting, by the first mobile drive unit, a second reservation request requesting use of the first path segment to move in the first direction.

22. The method of claim 18, wherein the reservation request comprises a current reservation request, and wherein determining whether the second mobile drive unit is moving in the first direction comprises:

prior to receiving the current reservation request from the first mobile drive unit, receiving a previous reservation request from the second mobile drive unit requesting use of the first path segment to travel in a reserved direction;

storing the previous reservation request; and

determining whether the second mobile drive unit is moving in the first direction based on the stored previous reservation request.

23. The method of claim 18, wherein transmitting a reservation response indicating that the reservation request is granted comprises:

determining whether the first path segment extends farther than a second path segment currently reserved by the second mobile drive unit;

in response to determining that the first path segment extends farther than the second path segment, transmitting a reservation response indicating that the reservation request is denied; and

in response to determining that the first path segment does not extend farther than the second path segment, transmitting a reservation response indicating that the reservation request is granted.

24. The method of claim 18, wherein transmitting a reservation response indicating that the reservation request is granted comprises:

determining whether the first path segment extends farther from the first mobile drive unit than a second path segment currently reserved by the second mobile drive unit;

in response to determining that the first path segment does not extend farther from the first mobile drive unit than the second path segment, transmitting a reservation response indicating that the reservation request is granted; and

in response to determining that the first path segment extends farther from the first mobile drive unit than the second path segment, transmitting a reservation response indicating that a reservation has been granted on a portion of the first path segment, wherein the portion is less than an entirety of the first path segment.

25. A method comprising:

transmitting, by a first mobile drive unit, a request to a management module for use of a path segment;

receiving, by the first mobile drive unit, a reservation response and a command to move in a first direction;

initiating, by the first mobile drive unit, movement in the first direction along the path segment;

detecting an object located on the path segment in the first direction from the first mobile drive unit;

determining, by the first mobile drive unit, whether the object comprises a second mobile drive unit moving in the first direction; and

in response to determining that the object comprises a second mobile drive unit moving in the first direction, continuing, by the first mobile drive unit, movement in the first direction.

26. The method of claim 25, further comprising:

in response to determining that the object does not comprise a second mobile drive unit moving in the first direction, terminating, by the first mobile drive unit, movement in the first direction.

27. The method of claim 25, further comprising:

transmitting, by the first mobile drive unit, a drive identification signal, wherein the drive identification signal indicates a first speed and the first speed comprises a current speed of the first mobile drive unit;

calculating, by the second mobile drive unit, a second speed based on the first speed; and

moving, by the second mobile drive unit, in the first direction at the second speed.

28. The method of claim 25, wherein determining that the object comprises a second mobile drive unit moving in the first direction comprises:

determining whether the first mobile drive unit detects a drive identification signal transmitted by a second mobile drive unit, the drive identification signal indicating that the second mobile drive unit is a mobile drive unit moving in the first direction.

29. The method of claim 28, wherein the drive identification signal further indicates a state of the second mobile drive unit;

and further comprising;

calculating, by the first mobile drive unit, a second speed based on the state of the second mobile drive unit; and

continuing, by the first mobile drive unit, movement in the first direction at the second speed.

30. The method of claim 28, wherein the drive identification signal indicates a state of the second mobile drive unit by indicating at least a current speed of the second mobile drive unit and a deceleration rate associated with the second mobile drive unit;

and further comprising;

calculating, by the first mobile drive unit, a second speed based on the indicated state by calculating a second speed based on the current speed of the second mobile drive unit and the deceleration rate associated with the second mobile drive unit.

31. The method of claim 30, wherein calculating, by the first mobile drive unit, a second speed based on the state of the second mobile drive unit comprises:

calculating a second speed based on the state of the second mobile drive unit and a deceleration rate associated with the first mobile drive unit.

32. The method of claim 31, further comprising:

determining, by the second mobile drive unit, the deceleration rate associated with the second mobile drive unit based on a docking state of the second mobile drive unit.

33. The method of claim 32, further comprising:

determining, by the second mobile drive unit, the deceleration rate associated with the second mobile drive unit based on one or more properties of an inventory holder docked with the second mobile drive unit.

34. A non-transitory computer-readable medium comprising logic, the logic, when executed by a processor, operable to:

transmit a request to a management module for use of a path segment;

receive a reservation response and a command to move in a first direction;

initiate movement in the first direction along the path segment;

detect an object located on the path segment in the first direction from a first mobile drive unit;

determine whether the object comprises a second mobile drive unit moving in the first direction; and

in response to determining that the object comprises a second mobile drive unit moving in the first direction, continue movement in the first direction.

35. The computer-readable medium of claim 34, wherein the logic is further operable to:

in response to determining that the object does not comprise a second mobile drive unit moving in the first direction, terminate movement in the first direction.

36. The computer-readable medium of claim 34, wherein determining that the object comprises a second mobile drive unit moving in the first direction comprises:

determining whether the first mobile drive unit detects a drive identification signal transmitted by a second mobile drive unit, the drive identification signal indicating that the second mobile drive unit is a mobile drive unit moving in the first direction.

37. The computer-readable medium of claim 36, wherein the drive identification signal further indicates a state of the second mobile drive unit and wherein the logic is further operable to:

calculate a second speed based on the state of the second mobile drive unit; and

signal to continue movement in the first direction at the second speed.

38. The computer-readable medium of claim 36,

wherein the drive identification signal indicates the state of the second mobile drive unit by indicating at least a current speed of the second mobile drive unit and a maximum deceleration rate associated with the second mobile drive unit;

and

wherein the logic is further operable to calculate a second speed based on the indicated state by calculating a second speed based on the current speed of the second mobile drive unit and the maximum deceleration rate associated with the second mobile drive unit.

39. The computer-readable medium of claim 36, wherein the first mobile drive unit is configured to be deployed in a grid-based workspace that includes a plurality of cells, and wherein the path segment comprises one or more cells of the grid-based workspace.

40. The computer-readable medium of claim 34, wherein the logic is further operable to transmit a drive identification signal, wherein the drive identification signal indicates a first speed and the first speed comprises a current speed of the first mobile drive unit.