Storage and retrieval machines (SRMs) – also known as automated storage devices – are material handling systems for the manual or automated servicing of racking systems.
They are typically:
rail-guided on the floor
supported by rails at the top of the rack or warehouse ceiling
divided into single- or double-mast machines
Some SRMs can navigate curves, making them independent of specific aisles. However, movement into staging areas or production zones is generally not possible or practical.