Guide to Real-Time Location Systems (RTLS)

What you need to know about use, function, benefits and choosing the right real-time localization system for you.

Our video gives you an initial insight into use cases for RTLS technology

Real-time localization in an industrial environment

The location of industrial assets, such as load carriers or tools, is a key requirement for the automation of logistics and production processes in many companies. As part of the digital transformation towards iIoT (industrial Internet of Things), Production 4.0 and Smart Factory, you need to know exactly where your assets are at all times. Load carriers, industrial trucks and mobile test equipment are tracked in terms of their position, current status and ID to ensure they are used optimally.

The underlying technology, real-time location radio tracking, offers huge opportunities in manufacturing, intralogistics and logistics. Where other RTLS tracking technologies reach their limits, such as with GPS applications in buildings, Ultra-Wideband (UWB) impresses with its cm-accurate, precise location of items. In addition to creating an optimal information basis for digitization and automation, there are two other important advantages: Expensive search times are eliminated - at the same time, process transparency is massively increased. Both contribute to keeping your customer promise and reduce your logistics and production costs.

What is RTLS?

Definition of a real-time location system

If we want to reliably navigate to a point in our private environment, GPS helps us by determining our position via satellites. In production companies and their indoor spaces, other technologies are used: e.g. Bluetooth Low Energy, BLE for short, via beacons, WLAN or ultra-wideband (UWB). The precise, almost cm-accurate positioning predestines UWB as a technology for use in RTLS systems. GPS finds the building. UWB, on the other hand, "finds" a very specific object on a floor of a building with the utmost precision. The potential of UWB in warehouses or production halls is enormous due to the very precise positioning. The wireless technology is also considered smart and stable. In contrast to Bluetooth and WLAN, UWB is robust and interference-free. No interference is to be expected.

The importance of real-time localization systems and industrial RTLS

Imagine being able to precisely determine every single location of all operating resources in the cycle at any time. For your material flow optimization, this means that you can use all pallets, load carriers, pallet cages, floor vehicles, tools, machines and, of course, production materials as efficiently as possible. What's more, you will know the status of each object: Is it available or occupied, empty or full, in which direction is it currently moving and to where, has it been cleaned, what is the battery status or when is a maintenance interval scheduled, etc. This gives you a reliable basis for planning.

This geolocation technology has the greatest potential when used in the material flow area, as in practice the processes here are rarely fully digitized or automated and data is not exchanged with other areas. The operational cost savings will therefore be greatest here.

The large number of RTLS applications in almost all industries makes the real-time localization system a key technology for digitalization.

Sorting: RFID and RTLS

RFID and RTLS are often used in the same context. What is the correct classification of both technologies? RFID (Radio Frequency Identification) is a radio-based technology that identifies objects using radio waves. This does not require visual contact between the transponder (tag) and the reader. In contrast to classic auto-ID technologies, where a person has to scan an object with a reader, RFID technology carries out the reading process automatically, even in bulk and at high speed. The reader transmits electromagnetic waves that are received by the transponder (attached to the object) via its built-in antenna. The tag sends its signal back to the reader. Tags can be written with a variety of data. However, the signal range of RFID systems is designed for 0.1 - 18 m. This results in a perfect application scenario, e.g. to correctly record all goods in the system at once when loading a truck in the outgoing goods area. In this case, it is a matter of pinpointing the location of objects.

However, if individual objects need to be located over a large area, a real-time location system based on UWB technology is more suitable. In practice, a combination of both technologies is often used to suit the various applications. Especially because the unit price for RFID tags is often low.

 

What applications does RTLS offer you?

By using real-time location systems, you receive digital real-time position information about all operating resources for cost-efficient utilization on the store floor or in operations. Mapping in RTLS allows you to create a digital twin of each tool, for example, which provides you with all current information at a glance: ID, position, status, type, maintenance history, planned maintenance and much more. You gain control over your assets and use them productively without wasting costs.

Healthcare: Real-time tracking of mobile medical devices in hospitals

In hospitals and rehabilitation clinics, medical equipment, beds and wheelchairs are usually brought to where they are needed. Fast asset tracking of medical equipment can also be life-saving. However, flexible mobility for the benefit of the patient also has a major disadvantage: hospital staff have no automated and reliable knowledge of where, for example, a mobile ultrasound device is located when needed. Information about the status of a medical device is also important, e.g. its hygienic condition or whether it is currently freely available or in use. In everyday life, nursing staff are unnecessarily delayed by search times. The accelerated identification of the location of medical equipment and hospital inventory can be increased with RTLS and thus contribute to relieving staff and improving patient service. Of course, this also has an impact on the already tight cost situation. This also applies to other companies. For tracking, BLE transmitters, known as beacons, are attached to the objects to be tracked. Once the object has been moved, location data is transmitted by the transmitters' built-in acceleration sensors. The precise location data can be displayed to hospital staff in the hospital floor plan, usually down to the location in a room, on a tablet or smartphone via a corresponding app.

Reasons for RTLS in the healthcare sector:

• Disinfected beds are parked in stockpiles, usually where there is no official place for them
• Medical equipment remains at the last deployment site and must first be found again for the next deployment
• Wheelchairs are forgotten where they were parked

RTLS solutions in industry and intralogistics

In industry and intralogistics, 20% excess stocks of pallets, containers, racks, tools, boxes and other production inventory are usually used in practice. There is only one reason for this: their location cannot be determined in real time. These safety stocks are expensive and unnecessary. If, on the other hand, the position of materials and containers is known at all times via RTLS tracking, material flows can be organized without disruption. Such RTLS-based applications allow you to react flexibly to orders because you know where your resources are at all times.

What is the solution? With dynamic real-time radio positioning, you can optimize your material flows by avoiding search times and supplying all relevant objects to production at the required time. Using material containers as an example, a higher and therefore more efficient throughput can be seen after a very short time. Not forgetting process reliability. By determining the position of all materials down to the last centimeter, you can check which material is in which production zone. This prevents errors and costly downtime.

Responding flexibly to customer requests, right down to small batch sizes, and optimally utilizing production in regular operation requires seamless monitoring of your material flows. RTLS with its real-time radio location enables you to monitor assets and materials required for production at all times.

Reasons for RTLS in the industrial environment:

• Warehouse equipment is not located where it is needed
• No knowledge of the condition of forklift trucks, pallets, load carriers, etc.
• Inventory intransparency via operating resources

RTLS for mobile robotics & autonomous vehicles

Vehicles are particularly suitable for being tracked with an RTLS system. As they are usually constantly mobile and often parked somewhere else, the search effort is enormous. RTLS examples for this type of asset tracking are Rental cars, vehicles in large warehouses, depots or at the airport - fast track & trace of vehicles can only be automated. If a specific vehicle is being sought, "pinpoint" localization is essential. Logistics and production managers also need complete transparency about the duration and location of mobile robots and industrial trucks.

Reasons for using RTLS to locate vehicles:

• Lack of transparency about the location and condition of vehicles
• No process reliability: Material is not on the right production line
• Employees waste valuable search time

RTLS solution for locating tools

Special tools are generally very expensive and available in limited quantities. They cannot be kept in large buffer stocks, as is done in practice with plastic boxes. Whether in the field service vehicle, on the construction site or in the factory, tools must be quickly accessible to the relevant workers. The solution is usually implemented using BLE beacons (Bluetooth Low Energy) and RFID tags. Tools are tagged so that they can be found quickly using modern location technology. Toolboxes or tool trolleys are also given this marking, which can be used to determine their unique ID and position. This enables you to deliver orders faster and more flexibly. There will be no time delays caused by searching for tools.

The tracking technology can also register movements. In addition, you can use the transparency of the tool inventory and its utilization to gain valuable key figures.

Reasons for RTLS for locating tools:

• Special tools have to be found before they can be used. This costs employees time.
• Expensive new purchases of tools and test equipment due to shrinkage
• Tools are not cleaned up after use

RTLS for the safety of employees

When it comes to tracking people, the "alarm lights" may spontaneously go on, but the correct, data protection-compliant location of employees is actually an important part of their occupational safety. On a large company site, rescue measures can be initiated immediately in the event of an accident at work if it is known how many people are currently in the affected zone. It is not a question of knowing who is in the danger zone, but of knowing that there are people in the danger zone who need to be found quickly.

Another example: In secure areas, you can also coordinate access restrictions for certain people. This type of monitoring ensures that no unauthorized persons gain access or that an alarm would be triggered if they did.

Reasons for RTLS for occupational safety:

• In the event of a plant accident, you do not know how many people are currently in the affected zone
• You need to quickly find a specific technician for a malfunction in the system
• You risk production downtime - simply because employees are not found quickly enough

How does RTLS work?

Various positioning technologies: Ultra-wideband UWB, WLAN and BLE

Short-range radio communication via the so-called ultra-wideband is suitable for indoor areas. This radio technology in the 3 - 10 GHz transmission range works by means of pulse radio, i.e. different pulses are used over a wide frequency band (500 MHz). With UWB, the pulses are in the nanosecond range. This has the advantage that the arrival time of a pulse can be measured precisely using the Time of Flight method (or Time-Difference of Arrival (TDoA)), up to +/-25 cm! This is an outstanding advantage of UWB compared to WLAN or BLE, which can only determine the exact position within a radius of 1-5 meters.

While Bluetooth Low Energy (BLE) or WLAN determine the position of an object by measuring signal strength, UWB uses other positioning methods. With UWB technology, the position is determined via the signal propagation time between a tagged object and several receivers (nodes). At least 3 such nodes are required for precise localization. The more closely meshed the network of nodes in a hall, for example, the more precisely objects can be localized.

Why UWB and not GPS, WLAN or BLE?

This question is quickly answered. Firstly, GPS is not precise enough to find an object at cm level. Secondly, it is only suitable for outdoor use in order to establish a connection to the satellite required for tracking. Other tracking technologies such as WLAN or BLE (Bluetooth Low Energy) can be used indoors, but cannot keep up with UWB (Ultra Wideband) in terms of connection stability and precision. BLE systems localize objects with an accuracy of up to 1 m at best. This makes the system prone to errors, as the employee could also mistakenly identify the object next to them. With UWB, on the other hand, you get highly accurate and reliable results. When deciding on the right positioning system, don't forget that UWB signals have a range of up to 150 m, just like WLAN, while BLE signals don't reach half as far.

The different localization methods

Time-Difference of Arrival (TDoA)

The Time-Difference of Arrival (TDoA) method is suitable for determining the position of a large number of large objects. The transponder transmits the signal, which is received by various nodes. The times required by the radio pulses between the transponder and two nodes are considered. In other words, not the absolute times, but only the difference between the two transit times. The determined time differences result in a curve on which the object being searched for is located in space. If several such curves resulting from the difference are superimposed, the exact position of the tagged object is obtained at the point of intersection.

Time of Flight (ToF)

The time-of-flight method is used to localize tools, driverless transport systems or workers. It is used in Two-way Ranging (TWR) mode so that it is suitable for very precise, reliable real-time localization. In contrast to TDoA, where only the time differences are taken into account, Time of Flight records the individual transit times between the transponder and the node. To increase accuracy, localization is carried out in both directions. Once from the transponder to the node and then again from the node to the transponder. This double localization limits measurement errors and inaccuracies, but requires an increased processing time. This allows the distance between the object and the nodes to be measured very precisely and its exact position to be determined. The position found is then transmitted.

Angle-of-Arrival (AoA)

The Angle of Arrival method is used if the RTL system is to be used outdoors. As there may be radio relay links operating in the same frequency range, this could cause interference with the fixed nodes. Therefore, outdoors only the transponder transmits its signal, which is received by two antennas in the RTLS node. The angle to the transponder can be determined from the phase differences between the two received signals. The advantage of transponders that are capable of all three localization methods (TDoA, ToF and AoA) is that they can be used indoors and outdoors without any gaps.

When does an RTLS system make sense for you?

It makes sense for you to introduce an RTLS system if you want to eliminate the following inadequate conditions in intralogistics and production:

• Process flows are disrupted because employees have to keep searching for pallets, containers, tools, test equipment, etc.
• This results in production delays
• The internal material flow comes to a standstill
• An increase in production throughput is not possible due to the lack of transparency regarding work equipment
• You keep at least a 20% safety stock of load carriers in order to be able to act flexibly at all
• You lack data to gain more transparency in the production process via an IoT platform
• Mobile robots and autonomous vehicles cannot find materials quickly enough because their location is unknown
• You have no real-time data to quickly change over production orders

With the transparency and control provided by permanent asset tracking via a real-time localization system, you receive precise information about the whereabouts of your assets. You can also track their movements, making deployment planning easier. If you know what is moving where and when, you can use the visualization to see where bottlenecks will occur and can therefore eliminate them proactively. You increase throughput and efficiency. Employees can concentrate on their actual work and are not held up by time-consuming searches. Recording and tracking your operating resources is an important step towards digitalized production. Start with optimized material flow management using an RTLS system.

RTLS provides data for further processing in the Smart Factory

If you have intelligently optimized your processes in production, intralogistics and logistics with an RTLS system, you are ideally positioned for a future self-organizing store floor. In the Industry 4.0 model, the smart factory provides for intelligent networking of operating resources. They "communicate" with each other in order to process production orders automatically. They trigger processes, such as the just-in-time replenishment of material on the assembly line. They ensure that exactly the right items are brought to the right production station by precisely identifying all individual parts and compare the units used with the total stock. Since such real-time tracking is connected to an ERP system, it can also trigger orders in purchasing. The smart factory uses a wide range of data that it receives directly from the store floor via sensors and simultaneously reports production orders back to all connected IoT points. The containers required for the order, including raw materials or semi-finished products, are allocated and precisely prepared for processing. This smart automated management is only possible if the location of the operating resources is known. This is the first step towards Internet-of-Things-controlled production. The opportunity for complete transparency on the store floor lies in the data obtained. If it is used to analyze processes, movement profiles, for example, can help to quickly identify where the material flow is coming to a standstill. Suboptimal processes become immediately visible and can be remedied.

What advantages does real-time localization with RTLS offer you?

The previous chapters have already discussed why it is essential that you know the location of your assets in logistics and production. Here we summarize the most important advantages for you:

• 100% Real-time transparency of your materials, goods and operating resources
• Reducing search times and therefore costs
• High process quality (JIT supply of the correct materials at the correct production location)
• Tracking of ground vehicles (e.g. forklift trucks) increases tour efficiency & capacity utilization
• Secure, automated access control when approaching via a vehicle (without gate code, card, etc.)
• Centimeter-precise recording of position, movement and status data of all objects
• High-precision, interference-free positioning in real time

Indoor or outdoor localization - What do you need to consider? RFID or UWB?

Moving on to the question of when it is worth investing in an RTLS system, the first question is whether you mainly have a need for tracking in the indoor area or more in the outdoor area. It is not always necessary or economical to track items 24/7. Sometimes it may be sufficient to register assets at checkpoints, for example. If this variant is sufficient for you, then the use of RFID is a good option. However, if you need to be able to track goods, containers or industrial trucks continuously, then an RTLS system based on UWB is recommended. This allows you to prove traceability during audits by precisely documenting the data.

In many companies, outdoor tracking does not stop at the company's own depot, but can continue across several locations. If pallets make their way from plant A to B and need to be localized at their new destination in a warehouse, an indoor tracking system is required. Ideally in combination with the preceding outdoor tracking. RTLS systems that seamlessly combine indoor and outdoor transponders with UWB tracking are a practical solution here. If the unit load is to be tracked within a supply chain or even a global supply chain, its identification using RFID tags is an economically viable solution.

How do you recognize a good RTLS real-time localization?

How much does an RTLS system cost?

Even if BLE systems are the cheaper investment compared to UWB or WLAN systems, you must of course consider the cost-benefit ratio, such as increased productivity, automated material flow, error reduction, etc. First analyze your desired area of application for real-time localization management. If selective checkpoints are sufficient for your asset tracking, you may be able to rely on an RFID solution. If you want to implement comprehensive indoor tracking of your assets, then it makes sense to consider an RTLS solution. The price depends on the number of objects you need to tag and the size of your factory or warehouse, which will need to be equipped with a correspondingly high number of nodes.

Some providers of RTLS systems support the decision-making process with a simulation in a real test environment. This shows how much hardware would be needed to install an RTLS solution in order to achieve certain defined results. So you know what you can expect for your money before you buy. Kathrein and its partners will also provide you with a realistic offer based on your requirements.