Method and system for transporting inventory items
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.
1. A system for inventory management, comprising:
a two-dimensional grid of fiducial marks within a workspace;
a plurality of inventory holders, each of the plurality of inventory holders associated with a fiducial mark in the two-dimensional grid of fiducial marks;
a plurality of mobile drive units, each mobile drive unit operable to:
move beneath an inventory holder at a first fiducial mark in the two-dimensional grid of fiducial marks, wherein the first fiducial mark identifies a first location of the inventory holder and facilitates navigation within the workspace from the first location to a second location in the two-dimensional grid by providing location information that is used by a management module to generate a path from the first fiducial mark to the second location;
lift the inventory holder at the first location;
move while the inventory holder is lifted from the first location to the second location in the two-dimensional grid by following the path generated by the management module;
lower the inventory holder at the second location; and
move away from the second location.
2. The system of claim 1 , wherein after lilting the inventory holder at the first location, a supporting member of the inventory holder is not in direct contact with a surface upon which each mobile drive unit operates.
3. The system of claim 1 , wherein moving while the inventory holder is lifted from the first location to the second location in the two-dimensional grid comprises moving the mobile drive unit along straight lines defined by intersections identified by the fiducial marks.
4. The system of claim 1 , wherein the inventory holder is positioned over an associated fiducial mark, and each mobile drive unit is further operable to move beneath the inventory holder by detecting the associated fiducial mark.
5. The system of claim 1 , wherein each mobile drive unit comprises a sensor and is further operable to:
calculate a difference between a portion of the inventory holder and the sensor; and
adjust the mobile drive unit beneath the inventory holder based on the calculated difference.
6. The system of claim 1 , each mobile drive unit further operable to:
raise a docking head of the mobile drive unit towards a surface of the inventory holder; and
engage the docking head with the surface of the inventory holder.
7. The system of claim 6 , wherein the docking head comprises a high-friction portion and engaging the docking head with the surface of the inventory holder comprises abutting the high-friction portion against the surface of the inventory holder.
8. The system of claim 1 , each mobile drive unit further operable to rotate the inventory holder about a center portion of the inventory holder while the center portion of the inventory holder is substantially vertically aligned with a center portion of the mobile drive unit.
9. The system of claim 1 , wherein each of the plurality of inventory holders comprise a frame and a plurality of legs, wherein the legs are arranged to form a plurality of device openings that allow the mobile drive unit to move under the inventory holder.
10. The system of claim 1 , wherein the inventory holder comprises four legs, and the device openings allow the mobile drive unit to move under the inventory holder from four different directions on the two-dimensional grid.