Collaborative mobile robots: AS/RS alternative

What is an automated storage and retrieval system?

Will Allen Last Updated: January 18th, 2020

Automated storage and retrieval systems (AS/RS) are computer- and robot-aided systems that can retrieve items or store them in specific locations. The system is usually comprised of predefined locations where machines can follow established routes to get items.

As long as everything is stored in its proper location, these systems help to speed up manufacturing and shipping tasks. Typically, automated storage and retrieval systems are used when high volume loads must be moved rapidly and accurately. Let’s explore the main types of AS/RS, how they work and their advantages and disadvantages.

In this article, we will explore:


Types of automated storage and retrieval systems Example of an automated storage and retrieval system: a red and blue unit-load system on a track.

The two primary types of AS/RS include unit-load and mini-load systems. Unit-load AS/RS is used for large loads such as handling full pallets or cases of items. Unit-load AS/RS handle the big jobs that may require moving objects or pallets that weigh a few thousand pounds. A typical unit-load AS/RS uses moveable-aisle cranes or fixed-aisle cranes:

  • Fixed-aisle cranes usually stay fixed to one area or row of pallets, in this scenario. They travel along the designated area or path to retrieve items.
  • Moveable-aisle cranes are similar, but they’re designed to retrieve or store items in multiple areas instead of along one path or aisle.

Mini-load AS/RS, such as case-handling or tote-stacking systems, are smaller cranes or robots that handle lightweight loads such as trays or cartons. Mini-load AS/RS typically use cranes or shuttles:

  • Mini-load AS/RS cranes move along narrow aisles to retrieve or store products. It’s essentially a much smaller version of a fixed-aisle crane.
  • Mini-load AS/RS shuttles run along a track and deliver items or move them between racking systems. Imagine a small flatbed truck that runs out and grabs a box, tote or tray for you. They can work at multiple levels if designed for the job, but most of them run along a single path.

Other types of AS/RS include carousel-based systems and vertical lift modules. Carousel-based AS/RS retrieve and store products with the help of an inserter extractor. The carousel spins until the shelf or bin is in the proper position for the inserter extractor to either place or remove the item. This system can usually move vertically or horizontally in a fixed area. Most carousel-based automated storage and retrieval systems handle smaller jobs than the heavy lifters like unit-load systems.

Vertical lift modules (VLM) work in a similar fashion to carousel-based systems. In this case, the inserter extractor is located in the center of an enclosed structure and is surrounded by columns of trays on both sides. It locates the correct tray and delivers it to an operator who then completes the order and returns the tray.

How automated storage and retrieval systems work

Each type of AS/RS operates in slightly different ways, all with the goal of speeding up warehouse processes. Each type of system outlined above automates the process of storing products in appropriate bins, shelves or other storage locations or retrieving items or loads from storage areas. They reduce the time and manpower needed to retrieve and store items.

Advantages of automated storage and retrieval systems

Automated storage and retrieval systems offer a few advantages, including:

  • Reduced labor costs
  • Improved accuracy, efficiency and productivity
  • Reduced safety risks for employees (reducing the need to lift and move heavy or bulky items)

AS/RS can work in environments that aren’t ideal for human workers, such as freezer storage areas. They can function at heights that are difficult for human workers to navigate, as well, allowing warehouse operators to maximize floor space by making better use of vertical space.

Disadvantages of automated storage and retrieval systems

Despite their advantages, there are several downsides to AS/RS solutions. The equipment is often large and bulky, requiring a significant upfront investment and substantial changes to the warehouse infrastructure and layout.

Regular equipment maintenance is required to keep AS/RS systems functioning at peak performance. When breakdowns do occur, productivity suffers substantially, sometimes grinding operations to a halt. Finally, warehouses that handle varying products at different times, such as seasonal items, may experience decreased productivity during these transitions while retraining the AS/RS to fetch or move new products.

A better alternative: collaborative mobile robots

Collaborative mobile robots: a better AS/RS alternative

There’s a better alternative to AS/RS solutions: collaborative mobile robots. They work alongside your human workforce to increase productivity and accuracy without requiring infrastructure changes. They’re intuitive to learn, so warehouses can get up and running with collaborative mobile robots in weeks compared to the months typically needed to implement AS/RS systems. Collaborative mobile robots guide warehouse associates through tasks, augmenting your human labor, rather than replacing your human workforce.

Collaborative mobile robots are also easily scalable. In some cases, you can rent collaborative robots as needed to supplement your workforce during peak times. Once demand returns to normal, you can simply return the robots you rented until the next rush.

To learn more about the benefits of collaborative mobile robots, download our white paper, 7 Reasons Why Warehouse Robots Beat Traditional Automation.