RFID Case Study: AGV Automated Guided Vehicle

RFID-Project Clinic: Controlling an automatic guided vehicle system in hospitals

At a glance...

  • Tagging of transport containers
  • Identification at branch points
  • Automated distribution of goods
  • Variable and reliable system
  • Reduced standstill times
  • Optimized logistics process
Used frequency: 13,56 MHz
  • RFID Reader HF60 SAV
  • RFID Transponder Karte

The challenge

Working behind the scenes of every large hospital is a complex supply system delivering medications, linen or meals on a daily basis to the different sectors. The transporting containers follow individual routes through a hospital and even make stops in between. Manual control of such a system is unimaginable, which is why automatic guided vehicles (AGVs) carry the containers throughout a hospital. At certain points, such as elevators or loading stations, containers must be identified before they can continue on their route. RFID has proven to be the ideal technology for this purpose of correct and sure identification. Unlike barcode, an RFID system is resistant to soiling and identifies without sight contact, besides offering much greater memory capacity on the data medium.

Manufacturers of AGVs create an efficient means of transport through a hospital along specified routes. To ensure their AGVs follow the right routes, they need an identification system at strategic branch points to show which vehicle with which container is momentarily waiting here for instructions on how to continue.

To keep the complexity, the control effort and the cost of an AGV system to a viable scale, they require a compact and highly functional device for minimum cost.

The implementation

Configuration of the system
Every container bears an RFID transponder for its unique identification. Vehicles and containers are located in stations at different points of a hospital, from where the personnel send them on their way online. As soon as a vehicle arrives at a branch point, a reader installed there detects the transponder and sends its information to the management system. After comparison of the data, a message comes back indicating the next destination for the vehicle. The AGV starts moving again, and the identification process is repeated at all branch points on the way to its destination. In AGV systems there are different identification variants with different RFID hardware solutions:

  • Transponder attachment to the side of the container – the RFID reader is installed at the same height at the identification points, and responds as soon as the container moves past or halts next to it.
  • Transponder attachment to the bottom of the container – the reader and antenna are installed in the vehicle. Identification occurs when the container is positioned on the vehicle.
  • Transponder attachment to the bottom of the container – this time the reader is installed in a control cabinet and the antenna in the floor of the building. The container is detected when it stops at an identification point.

Requirements of an RFID Reader

RFID technology is sensitive to metal in its close surroundings. The fact that both vehicles and containers are made of metal is consequently a considerable challenge for RFID hardware in the first variant described above, which is the one most commonly used. In this case the reader is matched to its surroundings and shielded by a special rear wall against the metal. All necessary extra components such as power supply, antenna or sensor reading are integrated directly in the reader which minimizes installation costs enormously. A simple conducted test mode provides information regarding the operational readiness of the RFID device.

Summary

The device is designed for minimum cost but nevertheless comes with extensive functionality. It requires little space, and contributes in a large way to reducing the number of components and the costs of a system.