Key Takeaways
- Warehouse robots generally fall into two types of automated vehicles, though vehicle capabilities vary by vendor: Automated Guided Vehicles (AGV), which follow a pre-programmed path and stop when encountering obstacles, and Autonomous Mobile Robots (AMR), which determine their own routes in real time and can dynamically move around obstacles.
- Calculating the appropriate range of fleet size requirements, from the ideal number for regular operations to the higher amount needed to meet peak demand, requires modeling five warehouse data points.
- When determining which automated robots are best suited for your facility, it’s crucial to consider navigation needs, payload requirements, and throughput.
- AGVs and AMRs also have different requirements for fleet management software and vehicle monitoring.
- Hybrid systems that blend AMR and AGV solutions can work, but only if the different types of robots are kept to their distinct areas and thoughtfully managed to avoid unnecessary traffic.
Once warehouse decision-makers have determined that automated robotic vehicles will enhance their facility’s material-handling capabilities, the conversation typically follows a certain pattern. Usually, discussion of implementing Autonomous Mobile Robots (AMR) and/or Automated Guided Vehicles (AGV) begins with a demonstration and a projected throughput number. Unfortunately, other factors are often overlooked, such as how many units the facility actually needs, how traffic management flows at peak volume, what the floor needs to have in place before a single AMR or AGV is activated, and how fleet-sizing decisions impact the total cost of ownership. An oversized fleet can drive unnecessary capital expenditures and ongoing operational expenses, while an undersized fleet can limit throughput and increase long-term operating costs.
For operations and technical leads who have already decided to move forward with their automation journey and are entering the evaluation phase to determine whether an implementation will succeed, it’s important to understand concepts like fleet sizing methodology; the data-guided throughput logic for deciding where to deploy AGVs or AMR robots by zone; what real traffic management looks like at scale; and the site readiness components that significantly impact both the timeline and the total project cost. All of these factors are crucial for assessing the business case.
How Many AMR Robots Do You Actually Need?
Warehouse square footage may seem like the most critical data point for estimating an adequate fleet size for deploying warehouse robots, but it’s not the most useful tool in a buyer’s hands. For one, some AGVs and AMRs have multi-level applications with mobile robotic elevators to take advantage of usable vertical space, not just floor space.
In practice, a large facility with short travel distances and moderate throughput volume can maximize operations with fewer units than a smaller facility dominated by high-frequency, multi-zone picking for consumer goods logistics operations. For example, an e-commerce distribution center processing thousands of small, time-sensitive orders may require a larger fleet of AMRs than a warehouse replenishing pallets to prevent queues at picking stations, even if the e-commerce center is much smaller.
In reality, the ideal fleet size comes through modeling six operational variables together. They are:
- The distances mobile robots need to cover between zones
- Peak throughput targets—measured in required transports per hour, rather than average daily volume
- The number of open destination targets available at any given time, which affects robot waiting times and fleet utilization
- Sequencing logic, i.e., whether robots can drop a load and immediately return for the next pick or must carry loads continuously through the full cycle
- Allowable driving speed under load, accounting for operating conditions such as shared work spaces where robots may need to slow when personnel are nearby
- Charging strategy and battery management, including whether robots rely on opportunity charging during normal operations, dedicated charging periods, or a combination of both
Note that speed under load requires extra consideration. Though a robot may be rated for a given top speed, it cannot operate at that top speed when carrying a full payload. The stopping distance for warehouse robots to remain within safety limits increases with weight, meaning speed must decrease. The speed listed on the spec sheet only goes so far, since the practical operating speed of a mobile robot is usually much lower. In real-world operations, robots spend much of their time accelerating, decelerating, navigating intersections, and waiting for traffic jams to clear rather than traveling at their maximum speed. Relying on these hypothetical spec sheet speeds will lead to an underestimation of the number of units a facility actually needs.
Completing this modeling exercise will yield not a single hard number, but a range. You’ll have a minimum effective fleet size based on your facility’s average throughput, plus a larger number that accounts for promotional or seasonal volume spikes.
Businesses should also consider accounting for anticipated business growth in fleet sizing. While overinvesting in unnecessary robots increases costs, designing a system with expansion in mind can prevent future disruption. Simulation allow organizations to evaluate how projected increases in throughput, order volume, or product mix will affect fleet requirements over time.
AGV vs. AMR Robots: The Decision Comes Down to Throughput by Zone
The next question is which type of warehouse robot will be most productive in each zone: AGVs or AMRs. Required throughput, process stability, layout complexity, future flexibility, and navigation needs are all factors here. For example, while an AGV follows a fixed, programmed path from point A to point B and stops completely if something blocks the prescribed route, an AMR is self-determining. It designs its own route between A and B, navigating around obstacles in the moment rather than waiting for them to clear.
When evaluating your options, consider the load type the AMR or AGV will be moving and what your load requirements are before evaluating performance requirements. At roughly two feet by one-and-a-half feet in size, smaller warehouse robots can handle totes and cartons. Standard pallet transport vehicles measure about four feet by three-and-a-half feet, while the largest available configurations can carry significant payloads, with maximum capacities varying by vendor and application. Identifying your facility’s load requirements is an early step that determines every subsequent specification decision.
Next to consider are performance requirements. Depending on their application, AMRs are generally well-suited for picking and supply areas where 15 to 20 transports per hour are needed, as each robot makes its own individual routing decisions. This flexibility is desirable when transport volume is within a manageable range. Self-determined movement is not ideal when throughput requirements rise in inbound and outbound zones and can even become a liability. With each vehicle choosing its own path, traffic is inevitable and can increase the risk of congestion and handling incidents, just when the operation needs to run at peak performance.
At high-throughput volumes, the restrictions imposed on AMR deployments to keep pace start to resemble those that inherently limit the movement freedom of AGVs. When AMR robots are relegated to fixed corridors, restricted zones, and prioritized routing sequences, the gap between the two technologies narrows considerably. In dense, high-volume environments, adding more AMRs does not always produce a proportional increase in throughput. Larger fleets can introduce congestion, longer wait times, and more complex traffic management, reducing overall efficiency. By comparison, AGVs operating along predefined pathways can deliver more predictable outcomes, which is why many automotive and manufacturing facilities continue to favor them for repetitive, high-throughput transport applications.
Traffic Management at Scale
A hybrid architecture for AMRs prioritizing “guided autonomy” is a possible solution for facilities with varying needs, but it requires clear zone definitions and separate fleet-management logic for each area. In this design, AMRs would follow a defined, pre-programmed path through high-throughput zones and then shift to autonomous navigation in lower-density areas. If plotted correctly, this compromise can benefit operations that require AGV-level performance in some places and AMR-level flexibility in others.
Blended fleets are also a smart logistics choice for ecommerce operations. In these environments, inbound velocity and outbound sortation typically operate at different throughput levels than picking and replenishment zones. However, when combining AGV and AMR technologies, mixing vehicle types within the same zone is more complicated than deploying them in different areas. Some facilities successfully operate mixed fleets with advanced traffic management systems, though this comes at a higher cost. In many cases, the traffic management overhead required to keep both warehouse robot types moving safely and efficiently would undermine any gains in throughput.
Another factor to consider is that each type of warehouse robot has different implications for IT and site readiness. Some AGVs have minimal onboard processing capabilities, as routing decisions are made in the fleet management software and uniformly applied across the fleet, though the routes can be updated in the software to be more dynamic. AMRs, on the other hand, must carry more onboard intelligence in order to make routing decisions independently. That difference is reflected in the system architecture, the software licensing structure, and the way IT teams monitor and troubleshoot the fleet in practice.
Additionally, a warehouse might have an existing fleet that they’re upgrading and expanding by adding different mobile robots. Depending on the robot models and their communication platform, the preexisting vehicles may be able to be incorporated into the new fleet management software for seamless integration. This makes scaling up easier and less costly overall.
Take Your Warehouse Robots Operations to the Next Level
Are you ready to begin a data-informed, goal-oriented determination of which warehouse robots will take your operations to the next level? TGW Logistics experts can advise on IT needs, payload requirements, and even change management for your staff as you deploy your automated vehicles. Get in touch for more information today.