45th AGV-Talk: How important is a reliable WLAN?

To prevent mobile robots from stopping unplanned or blocking each other, there are master controllers – with monitoring and control in real time. As in any relationship, communication is the most important thing: a fleet manager can only be as good as the communication with its fleet.

The open protocol VDA 5050 via WLAN has established itself as the interface between the control system and vehicles. The flow of traffic is usually controlled by allocating route sections. During a driving job, the vehicle reports the waypoints it has passed. The control system releases the next route section and previous sections are available to other vehicles. The smaller the route sections, the closer the possible distances between vehicles and the greater the achievable traffic density.

Problems arise when the deviation between the actual vehicle position and the last known position in the guidance control system becomes too great. This uncertainty is mainly due to delays in data exchange between the vehicle and the control system. If the master control system does not know where a vehicle is located, it cannot release anything. If a vehicle does not receive clearance for the next section of the route in time, it has to stop. This results in unplanned downtimes and a loss of throughput.

WLAN can cause considerable delays, especially with many mobile devices and when switching between access points. The control system is therefore designed in such a way that it can tolerate short-term interruptions. Route segments are dimensioned more generously and speeds are reduced. However, this is at the expense of traffic density and means restrictions in route and process planning.

• What are the problems with WLAN in practice?
• What should you pay attention to?
• What added value results from reliable data exchange with guaranteed latency?
• Are real-time capable wireless networks only worthwhile for high vehicle densities and large fleets, or do smaller systems also benefit from them?

We want to discuss these topics with Nick Schwarzenberg.
As always, I’m looking forward to it!

Best regards
Günter Ullrich
Forum-FTS