Method and system for transporting inventory items

An apparatus comprising:

• a drive module operable to propel the apparatus towards a destination;
• a docking actuator operable to facilitate docking with an inventory holder;
• a control module operable to:
• cause the apparatus to move to a starting location associated with an inventory holder;
• cause the apparatus to dock with the inventory holder;
• cause the apparatus to move towards a destination location;
• while moving towards the destination location, determine a location of the inventory holder;
• calculate a difference between the determined location of the inventory holder and an anticipated location of the inventory holder;
• determine whether the difference is greater than a predetermined tolerance;
• and
• in response to determining that the difference is greater than the predetermined tolerance:
• cause the apparatus to undock from the inventory holder;
• determine a correction value based on the difference, wherein the correction value indicates at least one of a direction and a distance;
• cause the apparatus to move based on the correction value;
• cause the apparatus to dock with the inventory holder;
• and
• cause the apparatus to move towards the destination location.

A system for storing inventory items, comprising:

• an inventory holder operable to store inventory items;
• and
• a mobile drive unit operable to:
• move to a starting location associated with an inventory holder;
• dock with the inventory holder;
• move towards a destination location;
• while moving towards the destination location, determine a location of the inventory holder;
• calculate a difference between the determined location of the inventory holder and an anticipated location of the inventory holder;
• determine whether the difference is greater than a predetermined tolerance;
• and
• in response to determining that the difference is greater than the predetermined tolerance:
• undock from the inventory holder;
• determine a correction value based on the difference, wherein the correction value indicates at least one of a direction and a distance;
• move based on the correction value;
• dock with the inventory holder;
• and
• move towards the destination location.