The Shuttle (Stacker Crane or Rack Master): The SRM moves in X & Y directions, while the shuttle moves in Z direction. Pick-up & delivery in storage cells & P/D stands are accomplished via a specially-designed shuttle mounted on the SRM. When the SRM is positioned accurately both in horizontal & vertical directions with the cell or P/D stand, the shuttle starts a move in the direction perpendicular to the movement plane of the SRM.
Planning & Control System containers arrive on a random basis. As soon as a P/D station becomes empty, a container is delivered to it, after which the SRM moves the load to an empty location in the rack. Pick-up & delivery on both P/D stations & storage cells are automated & controlled by computer. Request for retrieval of items also follows a random nature.
When this incoming & outgoing randomness are combined with material storage policies, an additional stochastic factor, the location of items in the rack, is introduced. The location assignment & planning, tracking & control of the total system are accomplished through a distributed system. These systems are often customized to suit & fit into the customer´s daily operation.