AGV & AMR Systems

AGVs and AMRs are the fastest-growing segment of warehouse automation — the most deployable, scalable, and risk-managed entry point. Unlike AS/RS or sortation systems, an AMR fleet can be deployed in phases, scaled seasonally, and redeployed across facilities. For DC applications, AMRs dominate because they adapt to the realities of a live warehouse.

---

AGV vs. AMR: The Critical Distinction

These terms are used interchangeably in vendor marketing. They are meaningfully different.

Characteristic	AGV	AMR
Navigation	Fixed path (wire, magnetic tape, QR code grid)	Free navigation (SLAM)
Obstacle response	Stop and wait	Navigate around
Path changes	Requires physical infrastructure change	Software update only
Installation	High (floor infrastructure)	Low (map + software)
Cost	$50,000-150,000/unit	$30,000-100,000/unit
Best for	Fixed, repetitive, high-precision transport	Dynamic warehouse environments

AGVs are appropriate for fixed, controlled environments — automated production lines, fixed dock-to-conveyor routes, manufacturing logistics. AMRs dominate in distribution because they adapt to obstacles, layout changes, and seasonal reconfigurations.

---

AMR Use Cases

Use Case 1: Tugger AMR (Cart Towing)

AMR tows a cart train of totes, orders, or cartons.

Application: Replenishment from reserve to pick zones; order totes from pick to pack; zone-to-zone transfer in large facilities. Performance: 2-6 carts per train; each cart holds 4-12 totes; 0.5-1 mile/hr in a live warehouse. ROI driver: Eliminates pedestrian transport — one AMR-tug replaces 1-2 FTE.

Use Case 2: Shelf-Lifting AMR (Goods-to-Person)

AMR drives under mobile shelving, lifts the unit, and delivers to a stationary picking station.

Key vendors: Amazon Robotics (formerly Kiva), Geek+, Hai Robotics, 6 River Systems. Performance: 300-600+ picks/hour at stationary station vs. 80-150 picks/hour walk-and-pick. 2-3× improvement typical. Requirements: Dedicated AMR grid storage area; no mixed use of shelving; Floor FF50+; 4-5 ft aisle widths.

Use Case 3: Pick Assist / Follow-Me AMR

AMR follows an operator, carrying the pick cart. Operator walks and picks; robot carries the load.

Key vendors: 6 River Systems (Chuck), Locus Robotics (LocusBot), Fetch Robotics (Zebra). Performance: 15-30% productivity improvement vs. manual cart. More modest than G2P — operator still travels. Best fit: Operations transitioning from manual; large facilities where cart movement is significant; mixed human/robot environments where full G2P isn’t justified.

Use Case 4: Autonomous Forklift (AMR-Forklift)

Fully autonomous pallet handling — picking from floor, rack, or dock and transporting to defined destination.

Key vendors: Seegrid, Vecna Robotics, Balyo (Linde), Toyota (Autopilot), Jungheinrich. Performance: 20-35 pallet moves/hour (vs. human 50-65/hr) — but available 24/7. Economics work: 24/7 operations with expensive overnight labor; hazardous environments (cold storage, narrow aisles); highly predictable, repetitive pallet flows. Don’t work: Dynamic high-congestion environments; poor pallet quality; operations requiring human judgment for exceptions.

---

Fleet Sizing: The Queueing Model

For detailed fleet sizing math — Little’s Law, cycle time decomposition, charging strategy, and the 70% utilization limit — see AMR Fleet Sizing.

The critical rule not in most vendor proposals: AMR throughput does not scale linearly past 70% utilization. The M/G/1 queueing model shows queue wait at 70% utilization = 2.33× mean service time; at 85% = 5.67×. Path congestion compounds on top. Effective throughput peaks at 65–75% utilization and declines past that.

Design at ≤70% utilization at peak hour. If sizing math produces 85%, you have an undersized fleet — add robots.

The 15% maintenance float is not optional: spec’d fleet = operational minimum ÷ 0.85. Without it, the first two robots entering scheduled maintenance push below throughput commitment.

---

Fleet Sizing Methodology

Step 1: Define the Task

Parameter	Input
Transport route	Origin → Destination; distance (feet)
Frequency	Trips per hour at peak
Load per trip	Totes, pallets, or cart trains
Cycle components	Load, travel, unload, return

Step 2: Calculate Cycle Time

Cycle Time = Load Time + Travel Time (loaded) + Unload Time + Return Time

Travel Time = Distance (feet) ÷ Speed (feet/min)

Speed assumptions:

• AMR in live warehouse: 150-250 FPM loaded (2.0-3.0 MPH)
• Apply 85-90% reduction for traffic, intersections, acceleration
• Effective speed: 130-220 FPM

Example — replenishment run (reserve to pick zone, 300 ft):

Cycle Element	Time
Load cart at reserve	2.0 min
Travel to pick zone (300 ft ÷ 165 FPM)	1.8 min
Unload at pick zone	1.5 min
Return to reserve	1.5 min
Total cycle time	6.8 min

Step 3: Required Fleet Size

Robots = (Required Trips/Hour × Cycle Time in Hours) ÷ Target Utilization (80%)

Example:
25 trips/hr × 0.113 hr ÷ 0.80 = 2.83 → round up to 3 robots

Add 1 robot for maintenance/charging buffer in a 3-robot fleet. Final fleet: 4 robots.

Step 4: Battery and Charging

• Battery life: 8-16 hours depending on load/travel intensity
• Charging stations: 1 per 2-3 robots (opportunity charging model)
• Infrastructure cost: $3,000-8,000 per charging station
• Power draw: 1-3 kW per AMR during charging

---

Path Design and Traffic Management

Map development (SLAM process):

1. Drive robot through facility to build initial map
2. Remove dynamic objects (forklifts, temporary storage)
3. Validate permanent infrastructure as fixed obstacles
4. Program no-go zones (dock areas during active loading, pedestrian zones)

Aisle width minimums:

AMR Type	Minimum Aisle Width
Shelf-lifting (small)	4.5-5.5 ft
Cart-towing tugger	6-8 ft
Pallet AMR-forklift	8-10 ft
Mixed human/AMR	+2-3 ft beyond single-use minimum

Traffic management: Fleet Management Software (FMS) handles collision avoidance and right-of-way. One-way robot aisles eliminate congestion where possible. Humans always have right-of-way; AMRs stop when humans enter their path.

---

Payback Benchmarks

Scenario	Typical Payback
AMR picking assist, 3 shifts	8-12 months
AMR picking assist, 1 shift	20-30 months
Shelf-lifting G2P (3 shifts)	12-18 months
Tugger AMR (labor redeployment)	10-18 months

Shift utilization is the most sensitive variable. The same fleet achieves payback in 8-12 months at 3 shifts and 20-30 months at 1 shift.

Documented: AMR deployments with 250%+ ROI in multi-year live deployments; 42% 5-year OPEX reduction with labor redeployment.

---

Integration and Cultural Failure Mode

The most common AMR failure is cultural, not technical. Workers who distrust the system override it, block paths, or move pods the robots are managing — destroying throughput and ROI.

Best practices:

• Pre-launch briefings explaining what robots do and don’t do, and how to interact safely
• Floor markings distinguishing robot paths from human paths
• Clear escalation protocol when a robot is stuck — workers need a way to report, not stand next to a stopped robot
• Feedback loop for operators to flag operational issues