VDA 5050 in practice: KLT palletizing and AMR handover
VDA 5050 regulates the vehicle side of handing over a pallet of small load carriers (KLT): pick, drop, fine positioning, waiting for release. It does not regulate the handshake, the signal exchange between station and vehicle. Peripheral interfaces are expressly excluded. Since March 2026, VDA 5050 has been available in version 3.0.0.
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How VDA 5050 regulates communication with mobile robots
VDA 5050 defines how fleet control and mobile robots exchange orders, instant actions and state messages via MQTT and JSON. MQTT (Message Queuing Telemetry Transport), at least version 3.1.1, is the messaging protocol, JSON (JavaScript Object Notation) the data format.
VDA 5050 is published by the German Association of the Automotive Industry (VDA) and co-developed by the Mechanical Engineering Industry Association (VDMA). The Institute for Material Handling and Logistics (IFL) at Karlsruhe Institute of Technology (KIT) maintains the GitHub repository.
Version 3.0 uses the terms "mobile robot" and "fleet control" instead of AGV (Automated Guided Vehicle, a driverless transport vehicle) and master control. Also new is support for freely navigating mobile robots: they share planned paths with fleet control, and a zone concept governs their behaviour in defined areas.
Communication runs via defined topics (MQTT message channels):
| Topic | Content | Mandatory/optional |
|---|---|---|
| order | orders from fleet control to the robot | mandatory |
| instantActions | immediate actions from fleet control | mandatory |
| state | state message from the robot to fleet control | mandatory |
| connection | reports when the robot's connection drops | mandatory |
| factsheet | robot key data for setup in fleet control | mandatory |
| visualization | high-frequency position and planned path for visualisation systems | optional |
| zoneSet | zones from fleet control to the robot (new in 3.0) | optional |
| responses | responses of fleet control to robot requests (new in 3.0) | optional |
What VDA 5050 does and does not regulate at the transfer point
At the transfer point, VDA 5050 regulates vehicle actions. Interfaces to peripheral equipment such as the palletizing cell, conveyor or PLC (programmable logic controller) lie outside. Section 2 of the specification ("Scope") expressly excludes this. It reads: "Interfaces unrelated to the communication between a fleet control system and mobile robots are excluded, such as interfaces to peripheral equipment, infrastructure components, or external IT systems."
Safety requirements are excluded as well.
Section 5.3 names peripheral systems such as doors, gates and lifts as fleet control tasks, without defining a protocol.
At the station, the standard regulates these vehicle-level actions:
- pick and drop: the robot picks up or sets down a load. Parameter stationType describes the station (for example floor position, rack position, passive or active conveyor), loadType the load type.
- finePositioning: fine positioning of the robot at a target.
- waitForTrigger: the robot waits until fleet control releases it via the "trigger" action, typically after another system reports process completion. Alternatively, a local signal on the robot releases it, such as a button press or manual loading. Fleet control monitors the waiting time.
The handshake at the transfer point: documented signal paths
Manufacturer sources document three direct signal paths between an autonomous mobile robot (AMR) and the station and one indirect via fleet control; the table is a selection of them.
| Signal path | Connects | Manufacturer example | What is documented |
|---|---|---|---|
| Infrared | top module on the AMR and stationary conveyor | Interroll LCP (a conveyor top module that sits on the AMR) | requires line of sight between top module and stationary conveyor, no offloading without it, conveyor load up to 50 kg |
| Wireless, method not stated | top module on the AMR and external conveyor | ROEQ GuardCom, NORD Modules Pallet Mover 1000 with Dock Target | wireless handshake or wireless communication with external conveyors |
| Optical I/O coupling | AMR and fixed conveyor | Omron LD Conveyor Top | an optical communications accessory for the top module, used for direct I/O status change between AMR and fixed conveyor |
| Indirect via fleet control: OPC UA (Open Platform Communications Unified Architecture) or Modbus | fleet manager or transport system control and periphery, no direct AMR-station exchange | BlueBotics ANT server (fleet manager), SAFELOG | conveyors, lifts and doors via Modbus or OPC UA (BlueBotics), PLC coupling via OPC UA or Modbus (SAFELOG) |
KLT to VDA 4500: dimensions, max. fill weight and stacking rules
VDA Recommendation 4500 defines basic dimensions, max. fill weights and stacking rules for KLT. It is freely accessible and currently in version 3.2 (August 2026). The KLT system is modular, matched to the pallets 1200 x 800 mm (Euro pallet) and 1200 x 1000 mm (ISO pallet).
R-KLT is rigid, with a composite base, RL-KLT has a smooth base, F-KLT is foldable.
| Type (selection) | Nominal size L x W x H in mm | Max. fill weight | Top load |
|---|---|---|---|
| RL-KLT 6280 | 600 x 400 x 280 | 20 kg | 600 kg |
| RL-KLT 6147 | 600 x 400 x 147 | 20 kg | 600 kg |
| RL-KLT 4147 | 400 x 300 x 147 | 20 kg | 600 kg |
| RL-KLT 3147 | 300 x 200 x 147 | 20 kg | 400 kg |
| F-KLT 6410 | 600 x 400 x 280 | 20 kg | 250 kg |
The stacking pattern depends on base and pallet. RL-KLT stack in columns only on both pallets. R-KLT in 600 x 400 and 400 x 300 can interlock on the ISO pallet, crosswise and self-securing; on the Euro pallet they too stack in columns.
The standard unit load has a stack height of 810 mm without pallet and securing plate. Because containers nest 15 mm into each other (nesting depth), the stack height fits 6 layers of 147.5 mm containers, 4 of 213.75 mm or 3 of 280 mm.
Which safety rules apply at the transfer point
ISO 3691-4, 2023 edition (German version DIN EN ISO 3691-4:2023-12), defines safety requirements for driverless industrial trucks and their systems, AMRs included. An operating hazard zone (an area where persons may be exposed to hazards) can by definition lie in load transfer areas.
Per the German Social Accident Insurance (DGUV), section 4.8.2.3 of ISO 3691-4 permits muting only in certain situations such as load transfer. Muting here means silencing the vehicle's personnel detection. The standard allows muting only with travel speed reduced to 0.3 m/s or less, and these situations also require additional protective measures.
The 2020 VDI guide on the safety of AGV systems (Association of German Engineers) demands load transfer stations where neither vehicle nor load endangers persons. Crushing and shearing points must be avoided by structural or technical measures.
Safety technology manufacturer Pilz treats interlinked machines and mobile platforms as one overall machine. Pilz considers a risk assessment for the entire mobile system necessary. IHK Nürnberg states the essential requirements of the EU Machinery Regulation apply from 20 January 2027. The EU Machinery Regulation post explains what this means for robot cells.
The information on safety does not replace legal advice.
Practical example: how DEUTZ palletizes KLT alongside existing AMRs
DEUTZ palletizes KLT containers at its Cologne logistics centre with a MalocherBot Palletizer S equipped with a Doosan P3020 cobot and a custom-developed gripper. The DEUTZ case study describes the project. Unchained Robotics delivered the turnkey cell, commissioned in 2025. It runs the LUNA Automation Operating System.
The cell closes a previously manual gap in empty-container handling. The existing AMRs at DEUTZ take over pallet transport within the logistics centre. Per the case page, the light curtains ensure simple, safe operator access at all times.
The case page text speaks of AMRs, while the customer quote refers to interfaces "including those to the conveyor technology and our AGVs". The case page does not state protocol or signal path of the handover. Christoph Heid, Head of Technology, Systems and Maintenance, Logistics Center: "It was particularly important for us that all electrical and mechanical interfaces […] were cleanly implemented."
What to define before going out to tender
Six points should be settled before going out to tender:
- Handshake signal path between station and AMR
- Transfer height and positioning tolerance of the station
- Pallet type
- KLT type and stacking pattern
- Safety concept of the transfer point
- Responsibility for fleet control and periphery communication
The post on planning mistakes in palletizing projects describes common mistakes, and the one on the right system integrator covers partner selection.
Frequently asked questions
Does an AMR have to support VDA 5050?
No. The specification describes its use as "optional and non-binding". KUKA promotes the KMP 600P mobile platform as "VDA 5050 compatible".
Where can I download the VDA 5050 specification?
The specification is free of charge from the VDA and in the GitHub repository; since version 2.1.0, VDA 5050 has been published in English only. If the GitHub version and the VDA PDF differ, the PDF applies.
Is a new version of ISO 3691-4 coming?
A draft ISO/DIS 3691-4:2026 exists; the vote ended in September 2026. Per its foreword, the draft adds Annex H on muting via combined vehicle signals and Annex ZA on EU Machinery Regulation 2023/1230. No publication date is fixed.
What do AMRs cost at Unchained Robotics?
The AMR category lists 12 models from 6 manufacturers; prices of individual models range from 12,000 to 109,950 euros excluding VAT, as of October 2026.