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InfographicsSafety Laser Scanners for AMRs & AGVs: Standards, Zones and Selection
What the safety standards ask for, how protective and warning fields work, how to size them to vehicle speed, and how to choose between discrete and EtherCAT integration.
Why a navigation LiDAR isn't a safety device
Navigation LiDAR and safety laser scanners can look alike and produce similar scan data, but only one is built and certified to stop a vehicle when a person is in the way. A safety scanner uses a redundant, self-monitoring design with dedicated safety outputs, and it is tested to a recognized standard. A navigation sensor such as the UST-10LX is a measurement device: excellent for mapping and localization, but not certified for personnel protection.
That is why most production AMRs carry both, or use a safety scanner whose measurement output also feeds navigation, with the two functions evaluated separately. For a side-by-side look, see Safety Laser Scanner vs. LiDAR Sensor.
The safety standards in plain terms
Three families of standards come up on almost every AMR or AGV project. Each answers a different question.
ISO 3691-4
Sets safety requirements for driverless industrial trucks and their systems, including AGVs and AMRs. It covers personnel detection, speed limits, operating zones and braking, and assigns a required performance level to each safety function. In the US, ANSI/ITSDF B56.5 covers the same ground.
Who proves it: the vehicle manufacturer or system integrator, for the complete machine.
ISO 13849-1
Rates how reliably a safety function works, on a scale from Performance Level a (lowest) to e (highest). “Category” describes the architecture behind it.
PL d, Category 3 means a redundant design in which a single fault does not cause loss of the safety function, with diagnostics that detect most faults.
IEC 61496-1 / -3
Covers electro-sensitive protective equipment. Part 3 applies to laser scanners that detect people by reflected light. Type 3 sets requirements for detection capability, self-testing and fault response.
Hokuyo UAM scanners are certified to ISO 13849-1 PL d, Cat. 3 and IEC 61496-1/-3 Type 3.
Protective fields vs. warning fields
A safety laser scanner watches user-defined zones around the vehicle and reacts differently depending on which one is entered.
Protective field
- If breached, the scanner's safety outputs switch off and the vehicle stops
- Sized so the vehicle can stop before reaching a person
- Up to 5 m on Hokuyo UAM scanners
Warning field
- Entered first, so the vehicle can slow down or sound an alert
- Avoids unnecessary hard stops that cost throughput
- Up to 20 m on the UAM-05LP and up to 30 m on the UAM-05LPA
Sizing zones to robot speed
The protective field has to be long enough for the vehicle to come to a full stop before it reaches someone who has just stepped into the field. The length in the direction of travel comes from three things: how fast the vehicle moves, how long the system takes to react, and how far the vehicle travels while braking.
A worked example (illustrative numbers)
An AMR travels at 1.2 m/s. Assume a total response time of 0.2 s, a measured braking distance of 0.5 m and a 0.15 m tolerance supplement:
(1.2 × 0.2) + 0.5 + 0.15 = 0.89 m minimum protective field ahead of the vehicle.
At 2.0 m/s the same vehicle travels further during the response time and needs more distance to brake, so the field grows quickly. These figures are examples only; use your vehicle's measured stopping performance, the scanner's specified response time and the method required by your applicable standard.
Speed-dependent field switching
One field sized for top speed would stop the vehicle constantly in tight aisles. Instead, the scanner switches between field sets as speed and direction change: short fields when creeping or docking, long fields at full speed, and offset fields in turns.
| Vehicle state | Typical field set | Why |
|---|---|---|
| Docking or creeping | Short protective field, close to the vehicle | Lets the vehicle approach stations and racks without false stops |
| Normal travel | Medium protective field plus warning field | Warning field slows the vehicle before the protective field is reached |
| Top speed in open aisles | Longest protective field and warning field | Covers the greater response and braking distance at speed |
| Turning | Field extended to the side of the turn | Covers the area the vehicle's corners will sweep into |
| Reversing | Rear field from a second scanner | A 270° scanner can't see directly behind its mounting point |
Field sets are selected by the vehicle controller or, on encoder-equipped models, by measured wheel speed. The UAM-05LP stores 32 area patterns, the UAM-05LPA stores 128 with four encoder inputs, and the UAM-05LECA-T301 supports up to 176 switchable patterns.
EtherCAT vs. discrete outputs
How the scanner talks to the vehicle's safety controller shapes wiring, diagnostics and how many field sets you can practically manage.
| Consideration | Discrete safety outputs UAM-05LP · UAM-05LPA |
EtherCAT with FSoE UAM-05LECA-T301 |
|---|---|---|
| Connection | Dedicated safety output and input wiring to a safety PLC, relay or controller | Safety and control data on one EtherCAT network using Fail Safe over EtherCAT (FSoE) |
| Field switching | Wired inputs from the controller; encoder inputs on the UAM-05LPA | Over the network; encoder speed data can be shared with the EtherCAT master |
| Pattern capacity | 32 (UAM-05LP) or 128 (UAM-05LPA) | Up to 176 switchable patterns, up to five protection zones |
| Measurement data | Distance and intensity over Ethernet | Raw measurement data through the EtherCAT master |
| Diagnostics | Status via outputs and configuration software | Network-level diagnostics for standard and safety functions |
| Best fit | Simpler vehicles, retrofits and controllers without EtherCAT | Vehicles and cells already built on an EtherCAT safety network |
Hokuyo UAM safety laser scanners for AMRs and AGVs
UAM-05LP
- 5 m protective / 20 m warning, 270°
- 32 safety-area patterns
- Distance and intensity output for obstacle detection and localization
- One of the smallest safety scanners available, for compact vehicles
UAM-05LPA
- 5 m protective / 30 m warning, 270°
- 128 area patterns and four encoder inputs
- Expanded I/O for speed-dependent field switching
- Improved resistance to dust, light interference and electrical noise
UAM-05LECA-T301
- EtherCAT with Fail Safe over EtherCAT (FSoE)
- Up to 176 switchable patterns and five protection zones
- Encoder speed data shared over the network
- Centralized configuration and diagnostics
For a full model-by-model comparison and selection steps, see Which Safety Laser Scanner Should I Use for an AGV, AMR, or Automated Manufacturing System? or browse all safety laser scanners.
What to have ready before you request a scanner
- Vehicle type, size and maximum travel speed
- Measured stopping distance at each speed
- Controller or safety PLC, and whether it uses EtherCAT
- Required performance level from your risk assessment
- Travel modes: forward, reverse, turning, docking
- Mounting positions and any load overhang
- Operating environment: dust, light, temperature
- Whether scanner data must also feed navigation
Frequently asked questions
Can a navigation LiDAR be used as a safety device on an AMR?
No. Navigation LiDAR such as the Hokuyo UST series is a measurement sensor and is not certified for personnel protection. Stopping an AMR or AGV to protect a person requires a safety-rated device, such as a UAM-series safety laser scanner, integrated into a validated safety control system.
What safety standards do Hokuyo UAM safety laser scanners meet?
Hokuyo UAM safety laser scanners are certified to ISO 13849-1 (PL d, Category 3) and IEC 61496-1/-3 (Type 3). Compliance of the complete vehicle with standards such as ISO 3691-4 depends on the full system design, risk assessment and validation.
What is the difference between a protective field and a warning field?
A protective field is the safety-rated zone: if it is breached, the scanner's safety outputs switch off and the vehicle stops. A warning field sits outside it and is typically used to slow the vehicle or signal an alert before anyone reaches the protective field. Hokuyo UAM scanners provide protective fields up to 5 m and warning fields up to 20 m (UAM-05LP) or 30 m (UAM-05LPA).
How do you size a safety field for an AMR?
The protective field must be long enough for the vehicle to stop before reaching a person. It is calculated from travel speed multiplied by the total response time of the scanner and vehicle control, plus the vehicle's braking distance, plus supplements for measurement tolerance and other factors defined in the applicable standard. Faster vehicles need longer fields, which is why speed-dependent field switching is common.
When should I choose the EtherCAT UAM-05LECA-T301 instead of a discrete-output scanner?
Choose the UAM-05LECA-T301 when the vehicle or system already uses an EtherCAT network and you want safety and control data on one network. It supports Fail Safe over EtherCAT (FSoE), up to five protection zones, up to 176 switchable area patterns and sharing encoder speed data over the network. Discrete-output models such as the UAM-05LP and UAM-05LPA suit simpler wiring to a safety PLC or relay.
Can I evaluate a Hokuyo safety laser scanner before buying?
Yes. Hokuyo-USA offers 90-day evaluation units so engineering teams can configure fields and test a safety laser scanner on their own vehicle before committing to a production order. Contact Hokuyo USA to request one.
Technical basis: Hokuyo-USA UAM-05LP, UAM-05LPA and UAM-05LECA-T301 product pages and the Hokuyo safety laser scanner category page, accessed October 29, 2026. Standards summaries are simplified for orientation and are not a substitute for the standards themselves or a qualified risk assessment. Verify current specifications for the exact model before purchasing or integrating.