| Written by Christian Aadal
What is RTLS?
Real-time locating systems (RTLS) identify automatically the location of objects in real-time, usually within a building or other contained area like a terminal or parking lot. Typically, wireless RTLS transponders are placed in or attached to objects to make them visible by determining their location. Readers are necessary to receive or detect signals from these tags. Most known examples for RTLS are tracking automobiles through an assembly line (learn more about it in our whitepaper 1x1 Smart Factory RTLS), locating pallets of merchandise in a warehouse, or finding medical equipment in a hospital.
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Locating systems include GPS, GSM (mobile phone network), active and passive RFID, infrared, ultrasound, WIFI, Bluetooth, optical locating, ultra-wideband among others. The location concept will determine which technology is best suited for a specific business solution. In most cases, the more RTLS reference points that are installed, the better the location accuracy - within the limits of the selected technology. In general, the location of a transponder can be detected either by passing objects or by triangulation. The first possibility uses gates or choke points to monitor the flow of tags and with the help of directional antennas, the direction of the movement is received. In this case, you know if an object is still in the room or not, when it entered or left and where it went. The second possibility is to pinpoint the position of a transponder by triangulation (or other methods of calculating the position), using several readers that receive the transponder signal. The accuracy of the computed location depends on the technology, and the surroundings of transponder and readers: walls, furniture, or various materials (like metal) can distort the estimated range.
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Where to use RTLS?
RTLS is a well-used concept throughout many different industries. Here is a list of different operational areas for real-time location systems:
- identify the correct carrier to feed material into a processing machine
- locate mobile equipment in a hospital to have it available
- identify persons and grant access to a gated area
- create automated jobs for lifting machines based on the identification of the objects
- combine identity of several items in a single location (e.g. pallets)
- monitor muster zones and the whereabouts of personnel in case of an emergency
- track the position of the parked vehicle after they leave the production line
- allow potential harmful operations in mines after all workforce has moved to a safe area
- follow a product along the production line (in a conveyor or non-conveyor belt system)
Such scenarios will determine the technology and the set-up of the RTLS. Also with RTLS, there are limitations. Some technologies may not be suited in certain environments, for instance in hospitals where sensitive equipment is operating and lives are depending on them. This said, every single case must be tested for a better understanding, especially the range of signal and its strength. Placing readers in utility rooms or above doors between hospital wings to monitor assets is not a problem.
RTLS may consist of various technologies used at the same time, e.g. RFID, UWD and NFC combined in one system to perform different tasks. It is important therefore to make a proper choice to avoid wrong design decisions already at the early stages. To solve this problem a special methodology for RTLS design space exploration was developed. It consists of such steps as modelling, requirements specification, and verification into a single efficient process.
Continue reading the complete overview: Real time location systems in manufacturing and indoor logistics
