School of Engineering
Automated Storage and Retrieval Systems
By Wong Wei, T2P4
Student No. S10178075
Lee Yong Him
Assistant Director
School of Engineering
September 15, 2018
Automated Storage and Retrieval Systems
Automated Storage and Retrieval Systems (AS/RS) are used throughout different industries to store almost anything, with different types of configurations to store document canisters, hazardous materials, spare parts, and many more. It is capable of accurately and safely storing and retrieving a large number of objects in as small a place as possible. It boasts many advantages over traditional warehouse storage solutions, such as huge reductions in labour requirements and wasted floor space, decreased retrieval times, increased accuracy levels and throughput capabilities, and more CITATION MHInd l 1033 (MHI, n.d.).

This report will describe some AS/RS types and their uses. This paper will then focus on the fixed aisle, unit-load AS/RS and further explain in detail the processes that make up the system by using block diagrams. This paper will conclude with suggestions as to how AS/RS units can be improved and optimized.
The various types of AS/RS
AS/RS are classified into two main categories, unit-load, and mini-load. Unit-load AS/RS is used for warehouses that handle larger loads that are placed on pallets or within containers. They feature aisles of storage racks that can reach heights of above 100 feet. Mini-load AS/RS is similar to unit-load AS/RS, except they are made to handle smaller loads which are stored in cartons, totes and storage trays CITATION Fer18 l 1033 (Glynn, 2018).

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Unit-load AS/RS types
There are two types of unit-load AS/RS, fixed aisle and moveable aisle. Both types use a crane to store and retrieve pallet racks or containers vertically and horizontally on storage racks, the only difference between the two is that the moveable aisle AS/RS crane can move between multiple aisles of pallets instead of a single aisle, which allows one AS/RS crane unit to cover more working space CITATION Fer18 l 1033 (Glynn, 2018).
Mini-load AS/RS types
Mini-load AS/RS come in four different types, mini-load AS/RS crane, mini-load AS/RS shuttle, carousel-based AS/RS, and Vertical Lift Module. Mini-load AS/RS cranes are identical to unit-load AS/RS cranes but are made to handle totes, cartons, canisters or trays instead. Mini-load AS/RS shuttles use a capacitor or battery-powered shuttle that runs between storage racks on tracks to retrieve or store objects. It can work on multiple levels if required. Carousel-based AS/RS stores the storage modules on horizontal or vertical sorters that are retrieved and stored by using a device called an inserter extractor. The entire unit spins into position until the bin containing the carton is aligned with the inserter extractor, which will then complete the storage or retrieval operation. Vertical Lift Modules (VLM) also uses an inserter extractor. The inserter extractor sits in the middle of two columns of trays positioned on either side. The inserter extractor simply locates the tray and completes the storage or retrieval operation CITATION Max18 l 1033 (Ziegler, 2018).

How fixed-aisle unit-load AS/RS works
A typical fixed-aisle, unit-load AS/RS consists of a storage structure, an S/R machine, storage modules, and one or more pickup/deposit stations. The storage structure is made up of the storage rack framework that contains individual storage compartments/space to hold storage modules, and the hardware required to align the S/R machines with the storage compartments of the AS/RS. The S/R machine does most of the work as it is used to retrieve/store storage modules as required. It usually takes the form of a large rigid mast with an elevator system that is mounted on a rail system that runs the length of the aisle. There is a parallel rail at the top of the storage structure to ensure alignment of the mast and carriage with the storage structure. Storage modules are objects that store material/objects. All storage modules are standardised to ensure that they can be handled by the S/R machine and fit into the storage compartments of the rack structure. Pickup/deposit stations act as the location where storage modules are transferred into and out of the AS/RS. It is found at the end of the aisle for convenient access to external handling equipment. A singular station may act as either a deposit station, a pickup station, or both, depending on the layout of the AS/RS. This station must be compatible with both the S/R machine and the external handling equipmentCITATION DavIL l 1033 (O’Sullivan, n.d.).

Figure SEQ Figure * ARABIC 1 A block diagram for the storage process of a fixed-aisle, unit-load AS/RS
When storing a storage module, a worker operates an external handling equipment (in this case, a forklift) to move the storage module (in this case, a pallet) to the pickup/deposit station. The worker then inputs the alphanumerical identification code of the storage compartment into the system. The alphanumerical identification code contains the vertical and horizontal position of the storage compartment. A record of all locations and their codes are stored in an item location file on the AS/RS computer. Computer controls and programmable logic controllers read the alphanumerical identification codes and use them to determine the required location and guide the S/R machine (in this case, a stacker crane) to the right storage module. As the S/R machine moves, a counting procedure positioning method is used to count the number of bays and levels in the direction of travel. Once the S/R machine is in place, it checks the counted number of bays and levels against the item location file to determine if it is in the right location. If it is in the right location, it will then stash the storage module into the container. If it is in the wrong location, the AS/RS will then calculate the number of bays and levels it has to move to get to the right compartment. The process repeats until it has reached the right compartment. The retrieval process is basically the storage process done backwards, where the worker inputs the alphanumerical identification code of the storage module, which the machine uses to find the right storage compartment and bring the storage module to the pickup/deposit station, where external handling equipment is on standby to retrieve the storage module and move it to where it needs to beCITATION DavIL l 1033 (O’Sullivan, n.d.).
Suggested improvements to modern AS/RS
BIBLIOGRAPHY Glynn, F. (2018, May 29). Types of Automated Storage and Retrieval Systems – 6 River Systems. Retrieved September 19, 2018, from 6 River Systems – Warehouse Management & Automation Solutions:
MHI. (n.d., n.d. n.d.). Automated Storage and Retrieval Systems. Retrieved September 19, 2018, from MHI – The Industry That Makes Supply Chains Work:
O’Sullivan, D. (n.d., n.d. n.d.). Microsoft Word – Unit 9 Automated Storage Systems. Retrieved September 21, 2018, from NUI Galway – NUI Galway:
Ziegler, M. (2018, September 18). 6 Types of AS/RS to Increase Efficiency in Your Warehouse | Conveyco. Retrieved September 19, 2018, from Conveyco | Material Handling System Integrator: