US Patent 9002506 Item retrieval using a robotic drive unit

Disclosed are various embodiments that may facilitate items being retrieved from a storage location. A robotic drive unit transports a carrier storage unit to be proximate to a target storage unit that comprises a container in which an item is located. The robotic drive unit aligns a receptacle in the carrier storage unit with the container in the target storage unit. The container is transferred from the target storage unit to the carrier storage unit. The robotic drive unit transports the carrier storage unit with the container to a destination.