An operation monitoring device monitors operations of machining devices in a machining line. Information on a workpiece stocker that constitutes the machining line is acquired, and a current workpiece stock number for the workpiece stocker is updated based on the acquired information. The necessity of change of machining speeds of the machining devices constituting the machining line is determined based on the current stock number for the workpiece stocker. Based on the result of the determination, change of the machining speeds is commanded to the machining devices located before and behind the workpiece stocker in the machining line.

An inventory system can include radio frequency identification (RFID) tags and RFID tuners that can be brought into interacting proximity with one another to provide input or other information about the location or other condition of movable elements within the inventory system. A wearable accessory that is wearable by a human operator can include RFID tuners thereon for interacting with RFID tags on other elements of the inventory system in order to communicate details about the elements and facilitate functions of the inventory system.

An inventory system can include radio frequency identification (RFID) tags and RFID tuners that can be brought into interacting proximity with one another to provide input or other information about the location or other condition of movable elements within the inventory system. For example, a closed or at least partially open state of a drawer can be determined based on signals from an RFID tag when the RFID tag and a corresponding RFID tuner are mounted on opposing faces of the drawer and a compartment that receives the drawer.

An inventory system includes inventory holders, container holders, containers carried by the container holders, mobile drive units, stations, and a management module. The management module instructs the mobile drive units to move the inventory holders and container holders to stations. Container holders are loaded with containers of inbound inventory items at a first station. Inbound inventory items are transferred from containers to inventory holders at a second station. Outbound inventory items are transferred from inventory holders to containers at a third station. Containers of outbound inventory items are removed from container holders at a fourth station.