Collaborative mobile robots: AS/RS alternative

What is an automated storage and retrieval system? AS/RS meaning and more.

Warehouse Automation Updated January 19th, 2023

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 systems, how they work and their advantages and disadvantages.

In this article, we will explore:

Types of automated storage and retrieval systems and examples
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 automated 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 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.

How to choose the right automated storage and retrieval system

To keep pace with consumer demand, retain their competitive edge and maintain a robust bottom line, businesses need to utilize every square inch of warehouse space effectively, maximize asset utilization and improve labor efficiency. To this end, some businesses choose to deploy AS/RS systems to automate warehousing and streamline product storage and retrieval operations.

However, the complexity of even the most basic AS/RS systems makes choosing the right one a very challenging task. To simplify the selection process, let’s review some of the features and factors to look for.

Reliable software

ASRS systems have four major components:

  • Storage and retrieval (S/R) equipment
  • Input/output system
  • Storage rack
  • Computer management system

The computer management system handles the loading and unloading of SKUs in an AS/RS system via a dedicated software that keeps track of inventory details such as:

  • The specific location of items
  • How long they were in storage
  • Where these items came from

The right AS/RS should come with robust and well-designed software to facilitate seamless scheduling of retrieval and storage operations. All instructions to the AS/RS system are passed through this software, so you must ensure that it’s easy to use, reliable and free of technical glitches.

Height and weight limitations

While AS/RS systems can be customized to handle virtually any type of item, certain types of systems are best for certain products. The system must be able to handle the maximum weight per unit load for your operations (approximately 5500 lb ). Shuttle and mini-load systems are designed to handle small loads (totes, cases, etc.) while unit load AS/RS systems are ideal for heavier weights (large totes, drums, pallets, etc.)

The vertical length should also match the overhead space of your facility. The most common types of storage racks are approximately 40 feet, although some systems can reach up to 100 feet. The higher you build your AS/RS system, the less expensive (per vertical foot) it becomes.


The right AS/RS system should occupy a small footprint (to maximize floor space) and come with multiple speed options that can comfortably handle picking and order fulfillment operations during peak demand periods. For e-commerce operations, it’s best to deploy a system with a high-speed buffer designed for quickly moving high load volumes in and out of storage. Since inventory accuracy is extremely high, companies can lower the amounts of safety stock in storage and reduce work-in-process (WIP) inventory, allowing them to accommodate more SKUs in the same warehouse space and offer customers more product choices and faster fulfillment times.

Customer service

Always purchase an AS/RS system from a vendor that offers fast and reliable customer service. In the event of technical issues, a non-functioning AS/RS system can create a domino effect of stoppages, reduced productivity and unfulfilled orders that can disrupt supply chains and result in an unsatisfied customer base. The ability to get professional help quickly is critical to your reputation and bottom line.

How much do automated storage and retrieval systems (AS/RS) cost?

As with most warehouse automation systems, the cost of an automated storage and retrieval systems can vary widely. The cost is dependent on several factors but can range from $70K for one standalone vertical carousel to more than $5 million for a fully integrated mini-load system that manages tens of thousands of SKUs.

Some of the factors that influence the final cost of an AS/RS system include:

  • The cost of the AS/RS equipment itself
  • Overall size and weight of products to be handled
  • Storage space
  • Operating environment (AS/RS systems for climate controlled and cleanroom environments cost much more)
  • Special handling requirements
  • Required throughput
  • The complexity of the software and machine controls
  • The cost of customizing and reconfiguring the equipment and your facility to maximize benefits
  • Cost of shipping, delivery and installation of the system
  • Integration with existing processes

Aside from the high purchasing costs, the operating and maintenance costs of an AS/RS system is considerable. What’s more, — estimates show that a high-tech automated storage and retrieval system will achieve measurable ROI in approximately 5 years, much longer compared to alternative automation solutions like collaborative mobile robots, which we’ll discuss in more detail below.

A better alternative: collaborative mobile robots

Collaborative mobile robots: a better automated storage system alternative

There’s a better alternative to AS/RS solutions: autonomous mobile robots (AMRs). 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 autonomous mobile robots in weeks compared to the months typically needed to implement AS/RS systems. Autonomous mobile robots guide warehouse associates through tasks, augmenting your human labor, rather than replacing your human workforce.

Autonomous mobile robots are also easily scalable. In some cases, you can rent autonomous 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 autonomous mobile robots, download our white paper, 8 Reasons Why Warehouse Robots Beat Traditional Automation. We can also discuss the solution that’s right for you. Contact us today.