# US 9,436,184 B2 · Method and system for transporting inventory items > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,436,184 B2 - Document ID: US9436184B2 - Status: Granted - Kind: B2 - Application number: 14/252,570 - Filed: 2014-04-14 - Published: 2014-08-14 - Granted: 2016-09-06 - Earliest claimed: 2006-06-09 - Assignees: Amazon Technologies, Inc. - Applicants: Amazon Technologies, Inc. - Inventors: Raffaello D'Andrea; Peter K. Mansfield; Michael Cordell Mountz; Dennis Polic; Patrick R. Dingle - Web page: https://patentgrep.com/patent/US9436184B2 ## CPC - B65G 1/0492: {with cars adapted to travel in storage aisles} - B65G 1/1378: {the orders being assembled on fixed commissioning areas remote from the storage areas} - B66F 9/063: {Automatically guided} - G05D 1/00: Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots (drive control systems specially adapted for autonomous road vehicles B60W60/00) - G05D 1/0022: {characterised by the communication link (data switching networks in general H04L12/00)} - G05D 1/0234: {using optical markers or beacons (optical beacons per se G01S1/70)} - G06Q 10/087: Inventory or stock management, e.g. order filling, procurement or balancing against orders - G06Q 10/08741: {by picking of items from inventory for fulfillment} - G06Q 10/08744: {by distributed inventory management} - G06Q 10/0877: {by inventory control or reporting using inventory tracking or counting} - B65G: TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS (packaging B65B; handling thin or filamentary materials, e.g. paper sheets or thread, B65H; cranes B66C; portable mobile or lifting or hauling appliances, e.g. hoists, B66D; devices for lifting or lowering goods for loading or unloading purposes, e.g. fork-lift trucks, B66F9/00; emptying bottles, jars, casks, barrels or similar containers, not otherwise provided for, B67C9/00; delivering or transferring liquids B67D; filling or discharging vessels for liquefied, solidified or compressed gases F17C; pipe-line systems for fluids F17D) - B66F: HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD ({invalid lifting devices A61G7/10; } mounting artificial islands on piles or like supports E02B17/00; scaffolding combined with lifting devices E04G1/22; lifting devices for sliding forms E04G11/24; lifting of buildings E04G23/06; shores or struts E04G25/00; lifts or other hoisting devices on ladders E06C7/12; props for mining E21D15/00) - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - G06Q: INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR ## Abstract A system for transporting inventory items includes an inventory holder capable of storing inventory items and a mobile drive unit. The mobile drive unit is capable of moving to a first point with the inventory holder at least one of coupled to and supported by the mobile drive unit. The mobile drive unit is additionally capable of determining a location of the inventory holder and calculating a difference between the location of the inventory holder and the first point. The mobile drive unit is then capable of determining whether the difference is greater than a predetermined tolerance. In response to determining that the difference is greater than the predetermined tolerance, the mobile drive unit is also capable of moving to a second point based on the location of the inventory holder, docking with the inventory holder, and moving the mobile drive unit and the inventory holder to the first point. ## Claims ### Claim 1 A system for navigation, comprising: a plurality of fiducial marks arranged in a two-dimensional grid in a workspace; a mobile drive unit, comprising: a position sensor operable to sense information associated with a first fiducial mark in the two-dimensional grid; a processing unit operable to process the information to produce information that identifies a location associated with the first fiducial mark within the two-dimensional grid; and a wireless transmission module operable to wirelessly transmit the information identifying the location associated with the first fiducial mark to a remote control module, wherein the remote control module utilizes the information identifying the location associated with the first fiducial mark to facilitate navigation within the workspace. ### Claim 2 (depends on 1) The system of claim 1, wherein the remote control module is further operable to: wirelessly receive the identifying information; determine that the mobile drive unit is located at the first fiducial mark based at least in part upon the information identifying the first fiducial mark; and calculate a path to a second fiducial mark in the two-dimensional grid based at least in part upon the information identifying the first fiducial mark. ### Claim 3 (depends on 2) The system of claim 2, wherein the first and second fiducial marks comprise unique identifiers that are affixed to a floor of the workspace. ### Claim 4 (depends on 1) The system of claim 1, wherein the transmitting of the information identifying the location associated with the first fiducial mark indicates to the remote control module that the mobile drive unit is proximate to the first fiducial mark. ### Claim 5 (depends on 1) The system of claim 1, wherein the mobile drive unit further comprises a docking mechanism operable to: raise a docking head of the mobile drive unit towards a surface of an inventory holder; and engage a docking head with the surface of the inventory holder. ### Claim 6 (depends on 1) The system of claim 1, wherein the position sensor comprises a camera operable to optically detect the first fiducial mark in response to sensing that a fiducial mark is in a view of the camera. ### Claim 7 (depends on 1) The system of claim 1, wherein the remote control module is further operable to: determine locations of one or more other mobile drive units in the workspace based on receiving information associated with fiducial marks from the other mobile drive units; and calculate a path from one fiducial mark to another fiducial mark that avoids collisions with the one or more other mobile drive units based at least in part upon the information. ### Claim 8 A mobile drive unit operable to: detect a first fiducial mark within a two-dimensional grid of fiducial marks in a workspace, wherein the second fiducial mark identifies a fixed location of the mobile drive unit within the two-dimensional grid of fiducial marks in the workspace; determine the location of the mobile drive unit within the two-dimensional grid of fiducial marks in the workspace based on the identified particular location; and navigate from the first fiducial mark to a second fiducial mark by providing the location of the mobile drive unit to a remote control module. ### Claim 9 (depends on 8) The mobile drive unit of claim 8, wherein the mobile drive unit is further operable to: transmit information associated with the first fiducial mark to the remote control module; and receive, from the remote control module, a path from the first fiducial mark to the second fiducial mark in the two-dimensional grid of fiducial marks. ### Claim 10 (depends on 9) The mobile drive unit of claim 9, wherein the path is calculated to avoid collisions with objects in the workspace. ### Claim 11 (depends on 8) The mobile drive unit of claim 8, wherein detect the first fiducial mark comprises sensing the first fiducial mark using a position sensor. ### Claim 12 (depends on 8) The mobile drive unit of claim 8, wherein: the second fiducial mark in the two-dimensional grid of fiducial marks is associated with an inventory holder; and the mobile drive unit is further operable to: determine that the inventory holder is located at the second fiducial mark; and dock with the inventory holder at the second fiducial mark. ### Claim 13 (depends on 8) The mobile drive unit of claim 8, wherein the particular location comprises a position of the mobile drive unit in relation to one or more fixed objects in the workspace. ### Claim 14 A method for transporting inventory items, comprising: sensing, by a mobile drive unit, information associated with a first fiducial mark within a two-dimensional grid of fiducial marks; processing, by the mobile drive unit, the information to produce an identifier associated with a location of the first fiducial mark within the two-dimensional grid of fiducial marks; transmitting, by the mobile drive unit, the information identifying the identifier associated with the location of the first fiducial mark to a remote control module; and receiving, by the mobile drive unit, navigation information from the remote control module instructing the mobile drive unit to move to a second fiducial mark, the navigation information calculated by the remote control module based at least in part upon the information identifying the identifier associated with the location of the first fiducial mark. ### Claim 15 (depends on 14) The method of claim 14, wherein the information identifying the identifier associated with the location of the first fiducial mark is used by the remote control module to calculate a location of the mobile drive unit based on a known fixed position of the first fiducial mark in a workspace. ### Claim 16 (depends on 14) The method of claim 14, further comprising moving the mobile drive unit to the second fiducial mark based at least upon the navigation information. ### Claim 17 (depends on 14) The method of claim 14, wherein the first and second fiducial marks are affixed to a floor of a workspace. ### Claim 18 (depends on 14) The method of claim 14, further comprising: docking the mobile drive unit with an inventory holder at the second fiducial mark; and moving the mobile drive unit away from the second fiducial mark. ### Claim 19 (depends on 18) The method of claim 18, further comprising undocking the mobile drive unit from the inventory holder at a third fiducial mark.