Wedge based lifting device and system

• US 10,144,587 B2
• Filed: 09/26/2016
• Issued: 12/04/2018
• Est. Priority Date: 09/26/2016
• Status: Active Grant

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Inventors: Stubbs, Andrew, Shydo, Jr., Robert Michael
• Primary Examiner(s): Logan, Kyle O
• Application Number:
  US15/276,566
• Publication Number:
  US 20180086561A1
• Time in Patent Office: 799 Days
• Field of Search: 700214
• CPC Class Codes: B65G 1/137 with arrangements or automatic control means for selecting which articles are to be removed
• CPC Class Codes: B66F 9/07522 Variable length or width chassis
• CPC Class Codes: G05D 1/021 specially adapted to land vehicles

Abstract

Features are disclosed for a mobile drive unit and systems including mobile drive units that eliminate the need for dedicated lifting motors. The mobile drive unit arrangements described leverage existing motors used to drive the rolling elements (e.g., wheels) of the mobile drive unit to perform the lifting. For example, a mobile drive unit may include four locomotion motors. Because each motor can be individually controlled, the distance between front and rear (or left and right) rolling elements can be used to actuate mechanisms for lifting payloads without requiring a dedicated lifting motor.

Claims

1. A mobile drive unit comprising:

a first wheel;

a second wheel;

a drive system coupled to provide a first force to drive the first wheel and to provide a second force to drive the second wheel;

a chassis having the first wheel mounted at a first end and the second wheel mounted at a second end, the second end opposite the first end, wherein the chassis is configured to extend when (i) the first force drives the first wheel in a first direction and (ii) the second force drives the second wheel in a second direction opposite the first direction, and wherein the chassis is configured to contract when (i) the second force drives second first wheel in the first direction and (ii) the first force drives the first wheel in the second direction;

a first wedge block having a first surface sloping downward from the first end toward the second end;

a second wedge block having a second surface sloping downward from the second end toward the first end, wherein the first wedge and the second wedge are mounted on the chassis, and wherein the first wedge block joins with the second wedge block when the chassis is contracted; and

a wedge supported by the first wedge block and the second wedge block, wherein a change in a length of the chassis causes a change in distance between the first wedge block and the second wedge block which causes a change in height for a top surface of the wedge.

2. The mobile drive unit of claim 1, further comprising:

an optical sensor configured to measure a distance from the chassis to the ground at one of the first end or the second end, wherein the first motor drives the first wheel and the second motor drives the second wheel to move the mobile drive unit, wherein the drive applied to each wheel is adjusted during locomotion to maintain a speed for the mobile drive unit and a distance from the top surface of the wedge to the ground.

3. The mobile drive unit of claim 1, wherein the first surface sloping downward comprises a first roller and the second surface sloping downward comprises a second roller, and wherein the first roller and the second roller reduce friction between:

(i) the first surface and the wedge; and

(ii) the second surface and the wedge.

4. The mobile drive unit of claim 1, wherein a portion of the wedge supported by the first sloped surface comprises a roller, and wherein the roller reduces friction between the first sloped surface and the wedge.

5. A mobile drive unit comprising:

a first rolling element and a second rolling element, wherein the first rolling element is driven by a first drive force and the second rolling element is driven by a second drive force;

a chassis having an adjustable length, wherein the first rolling element and the second rolling element are coupled with the chassis, wherein a length of the chassis determined by the first drive force and the second drive force, wherein the length is between a maximum length and a minimum length;

a first wedge block having a first surface sloping downward from a first end of the chassis toward a second end of the chassis; and

a second wedge block having a second surface sloping downward from the second end toward the first end, wherein the first wedge block and the second wedge block are mounted on the chassis, and wherein the first wedge block joins with the second wedge block when the chassis is at the minimum length, and wherein a change in the length of the chassis causes a change in distance between the first wedge block and the second wedge block.

6. The mobile drive unit of claim 5, further comprising:

a wedge supported by the first wedge block and the second wedge block, wherein the change in distance between the first wedge block and the second wedge block causes a change in height for a top surface of the wedge.

7. The mobile drive unit of claim 6, wherein the first surface comprises a first surface rolling element and the second surface comprises a second surface rolling element, and wherein the first surface rolling element and the second surface rolling element reduce friction between:

(i) the first surface and the wedge; and

(ii) the second surface and the wedge.

8. The mobile drive unit of claim 6, wherein a portion of the wedge supported by the first surface comprises a surface rolling element, and wherein the surface rolling element reduces friction between the first surface and the wedge.

9. The mobile drive unit of claim 6, further comprising:

a sensor configured to measure a distance from the chassis to the ground at one of the first end or the second end; and

a locomotion controller configured to;

determine the distance from the chassis to the ground is below a threshold distance; and

adjust at least one of the first drive force for the first rolling element or the second drive force for the second rolling element during locomotion of the mobile drive unit to maintain a speed for the mobile drive unit and a distance from the top surface of the wedge to the ground.

10. The mobile drive unit of claim 5, further comprising:

a locomotion controller configured to;

drive at least one of a first rolling element with a first drive force and a second rolling element with a second drive force to position the mobile drive unit beneath an inventory holder configured to hold at least one inventory item; and

determine at least one of the first drive force and the second drive force using a weight of the inventory holder, wherein the first drive force and the second drive force elevate a wedge supported by the first wedge block and the second wedge block.

11. The mobile drive unit of claim 10, wherein the mobile drive unit further comprises the wedge.

12. The mobile drive unit of claim 10, wherein the locomotion controller is configured to drive the at least one of the first rolling element and the second rolling element by:

transmitting a current location for the mobile drive unit and an identifier for the inventory holder to a route planning service;

receiving route information identifying a path from the current location to the inventory holder;

driving the at least one of the first rolling element and the second rolling element based at least in part on the route;

detecting an alignment identifier beneath the inventory holder, the alignment identifier identifying a center point of the inventory holder; and

driving the at least one of the first rolling element and the second rolling element to align the wedge with the first wedge block and the second wedge block using the identified center point.