Guide to Real-Time Location Systems (RTLS)

Real-time localization in the industrial environment

In many companies, the location of industrial assets such as load carriers or tools is a central requirement for the automation of logistical and production processes. In the context of digital transformations towards iIoT (industrial Internet of Things), Production 4.0 and Smart Factory, you should know exactly where your assets are at any time. Load carriers, industrial trucks, mobile test equipment are tracked in their position, with their current status and with their ID to ensure their optimal use.

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 in GPS applications in buildings, Ultra Wide Band (UWB) impresses with cm-accurate, precise location of the 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 manufacturing costs.

 

What is RTLS?

Definition of a Real-Time Location System

If we want to navigate reliably to a point in a private environment, GPS helps us by determining our position via satellites. In production companies and their interiors, other technologies are used: e.g. Bluetooth Low Energy, or BLE for short, via so-called beacons, or WLAN or ultra-wideband (UWB). The precise, almost cm-accurate location predestines UWB as a technology for use in RTLS systems. GPS finds the building. UWB, on the other hand, "finds" a very specific object highly precisely on one floor of a building. The potential of UWB in warehouses or production halls is enormous due to the very precise positioning. In addition, the wireless technology is considered smart and stable. Unlike Bluetooth and WLAN, UWB runs robustly and without interference. No interference is to be expected.

The importance of real-time localization systems and Industrial RTLS.

Imagine being able to precisely determine the location of every single piece of equipment 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. And on top of that, you get knowledge about the status of each object: Is it available or occupied, empty or filled, in which direction is it currently moving and to where, is it 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, because in practice the processes here are rarely fully digitized or not automated and data is not exchanged with other areas. The operational cost savings will therefore be highest here.

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

Sorting: RFID and RTLS

RFID and RTLS are often used in the same context. How should both technologies be correctly classified? RFID (Radio Frequency Identification) is a radio-based technology that identifies objects using radio waves. This requires no visual contact between the transponder (tag) and the reader. Compared to classic auto-ID technologies, where a human must scan an object with a reader, with RFID technology the reading process is automatic, even in a crowd and at high speed. The reader sends 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 meters. This results in their perfect application scenario, e.g. to correctly record all goods in the system at once when loading a truck in the outgoing goods department. Here, we are dealing with a point-by-point location of objects.

What are the possible applications of RTLS?

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. By mapping in RTLS, you can e.g. create a digital twin of each tool, which tells you all current information at a glance: ID, position, condition, type, maintenance history, planned maintenance, and much more. You get control over your assets and use them productively without wasting costs.

Healthcare: Real-time tracking of mobile medical devices in the hospital.

In hospitals and rehabilitation clinics, medical equipment, beds, wheelchairs are usually moved to where they are needed at the time. The fast asset tracking of a medical device can also be life-critical. Flexible mobility for the benefit of the patient, but also offers a major disadvantage: hospital staff have no automated and secure knowledge of where, for example, a mobile ultrasound device is located when needed. Statements about the status of a medical device are also important, e.g. its hygienic condition or whether it is currently freely available or currently in use. In daily routine, the nursing staff is unnecessarily delayed in their work flow by search times. The accelerated identification of whereabouts of medical equipment and hospital inventory can be increased with RTLS and thus contribute to the relief of the staff and a better service for the patient. Of course, this also has an impact on the already tight cost situation. The same is true for other businesses. For tracking, BLE transmitters known as beacons are attached to the objects to be tracked. Location data is transmitted after the object has been moved by built-in acceleration sensors of the transmitters. The precise

However, if it is necessary to locate individual objects 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 found in order to meet the various purposes. This is especially true because the unit price for RFID tags is often low.

location information can be displayed to the clinic staff in the clinic floor plan, usually down to the location place in a room, on a tablet or smartphone via a corresponding app.

Reasons for RTLS in Healthcare:

• Disinfected beds are parked in stockpiles, usually where there is officially no place for them to go
• Medical equipment remains at the last location and must first be retrieved for the next operation
• Wheelchairs are forgotten where they were left [H3] RTLS solutions in industry and intralogistics

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

What is the solution? With dynamic real-time radio location, you can optimize your material flows by avoiding search times and supplying all relevant objects to production at the required time. Especially the example of material containers shows a higher and therefore more efficient throughput after a very short time. Not to forget process reliability. With centimeter-precise positioning of all materials, you can control which material is in which production zone. This prevents errors and costly downtimes.

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

Reasons for RTLS in the industrial environment:

• Warehouse equipment is not located where it is needed
• no knowledge of condition of forklifts, pallets, load carriers, etc.
• Inventory non-transparency via operating resources

RTLS for mobile robotics & autonomous vehicles

Vehicles are particularly suitable for being tracked with an RTLS system. Since they are usually constantly mobile and also frequently always 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 searched for, "pinpoint" localization is indispensable. Logistics and production managers also need complete transparency about the duration and location of mobile robots and industrial trucks.

Reasons for RTLS to locate vehicles:

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

RTLS solution for tool location

Special tools are usually very expensive and available in limited quantities. They cannot be kept in high buffer stocks, as is done in practice with plastic boxes. Whether in the field service vehicle, on the construction site or in the plant, tools must be in quick access for the appropriate workers:in. The solution is usually implemented using BLE beacons (Bluetooth Low Energy) and RFID tags. Tools are tagged so that they can be found quickly via modern location technology. Tool cases or tool carts are also given this tag, 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 delay due to searching for tools.

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

Reasons for RTLS to locate 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, one's "alarm lights" may spontaneously go on, but in fact the correct, data protection-compliant tracking of employees is an important part of their occupational safety. On a large company site, rescue measures can be initiated immediately in the event of occupational accidents if it is known how many people are currently in the affected zone. It is not a matter of knowing who, but rather that people are in the danger zone who need to be found quickly.

Another example: In security areas, you can also coordinate access restrictions for certain people. By means of such monitoring, you ensure that no unauthorized persons gain entry, or that an alarm would be triggered in this case.

Reasons for RTLS on occupational health and 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 plant incident
• You risk production downtime - just because employees are not found quickly enough

 

How does RTLS work?

Various tracking technologies: Ultra Wideband UWB, WLAN and BLE

Short-range radio communication via the so-called ultra-wideband is suitable for indoor applications. This radio technology in the transmission range 3 - 10 GHz works by means of impulse radio, i.e. different impulses 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 accurately using the Time of Flight method (or Time-Difference of Arrival (TDoA)), down +/-25 cm! Compared to WLAN or BLE, which are only able to determine the exact position within a radius of 1-5 meters, this is an outstanding advantage of UWB.

Whereas with Bluetooth Low Energy (BLE) or WLAN the position of an object is determined by measuring signal strengths, UWB offers other positioning methods. With UWB technology, the position is determined via the signal propagation time between a tagged object and several receivers (nodes). For exact localization, at least 3 such nodes are needed. The closer the network of nodes in a hall, for example, the more precisely objects can be located.

Why UWB and not GPS, WLAN or BLE?

This question is quickly answered. Firstly, GPS is not precise enough to find a sought object at cm level. Second, it is only suitable for outdoor use to connect to the satellite - which is necessary for tracking. Other tracking technologies such as WLAN or BLE (Bluetooth Low Energy) can be used indoors, but cannot compete with UWB (Ultra Wideband) in terms of connection stability as well as precision. BLE systems locate objects with an accuracy of up to 1 m at best. This makes the system error-prone, because the employee could accidentally identify the object next to him by mistake. With UWB, on the other hand, you get highly accurate and reliable results. When deciding on the right tracking system, don't forget that UWB signals, just like WLAN, have a range of up to 150 m, while BLE signals don't reach half that far.

The different localization methods [H3] Time-Difference of Arrival (TDoA)

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

Time of Flight (ToF)

To locate tools, automated guided vehicles or workers, the Time of Flight method is used. To make it suitable for very precise, reliable real-time localization, it is used in Two way Ranging (TWR) mode. In contrast to TDoA, where only the time differences are taken into account, Time of Flight involves the acquisition of the individual travel times between the transponder and the node. To increase accuracy, localization is performed 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 increased processing time. Thus, the distance of the object to the nodes can be measured very precisely and its exact position can be determined. The position found is then transmitted.

Angle-of-Arrival (AoA)

The Angle of Arrival method is used when the RTL system is to be used outdoors. Since there may be directional radio links operating in the same frequency range, there could be interference with the permanently installed nodes. Therefore, only the transponder that is received by two antennas in the RTLS node transmits its signal outdoors. The angle to the transponder can be determined from the phase differences of the two received signals. The advantage of transponders that can handle 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 looking for pallets, containers, tools, test equipment, etc.
• This results in production delays
• The internal flow of materials comes to a standstill
• An increase in production throughput is not possible due to the lack of transparency about 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 manufacturing process via an IoT platform
• Mobile robots and autonomous vehicles cannot find materials quickly enough because their location is unknown
• You do not have real-time data to quickly change over production orders

With the visibility and control provided by permanent asset tracking via a real-time location system, you get precise information about the whereabouts of your assets. You can also track their movements, which makes it easier to plan operations. When you know what's moving where and when, visualization lets you see where bottlenecks will occur and consequently proactively eliminate them. You increase throughput and efficiency. Employees focus on their actual work and are not held up by time-consuming searches. Recording and tracking your operating resources is an important step towards digitized manufacturing.

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 self-organizing store floor in the future. 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. In doing so, they ensure that exactly the right items are brought to the right production location via the precise identification of all individual parts and compare the units consumed with the total stock. Since such real-time tracking is connected to an ERP system, it can also be used to trigger purchase orders. The smart factory uses a variety of data that it receives directly from the store floor via sensors, while reporting production orders back to all connected IoT points. The containers needed for the order, including raw materials or semi-finished products, are allocated and precisely staged 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 manufacturing. The opportunity for complete transparency on the store floor lies in the data obtained. If they are used to analyze processes, movement profiles, for example, can help to quickly identify where the material flow is coming to a standstill. Suboptimal processes thus become immediately visible and can be eliminated.

What are the benefits of real-time localization with RTLS?

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

• 100% real-time transparency of your materials, goods, resources
  Search times and thus reducing costs
• High process quality (JIT replenishment of the correct materials at the correct production location)
• Indoor or outdoor localization - What do you need to consider? RFID or UWB?

Transitioning to the question of when it is worthwhile for you to invest in an RTLS system, first brings us to the question of whether you have a need for tracking mainly indoors or more outdoors. Tracking items 24/7 is not always necessary or economical. Sometimes it might be enough to register assets passing checkpoints. If this option is sufficient for you, then RFID is a good choice. However, if you need to be able to track goods, containers or forklift trucks continuously, then an RTLS system based on UWB is recommended. In this way, you can also prove traceability during audits through precise documentation of the data.

• Tracking of floor vehicles (e.g. forklift trucks) increase tour efficiency & capacity utilization
• Secured, automated access controls when approaching via a vehicle (without gate code, card, or similar).
• Centimeter-precise acquisition of position and motion and status data of all objects
• High-precision, interference-resistant positioning in real time

In many companies, outdoor tracking does not stop at the company's own yard, but can continue over several locations. If pallets are on their way from plant A to B and are to be located at their new destination in a warehouse, a tracking system is needed for the indoor area. Ideally, this should be combined with outdoor tracking in advance. RTLS systems that seamlessly combine indoor and outdoor transponders with UWB tracking are a viable 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, and more. First, analyze your desired application area for real-time localization management. If point check-points are sufficient for your asset tracking, then you can possibly rely on an RFID solution. If you want to implement area-wide 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 needs to be equipped with a correspondingly high number of nodes.

Some suppliers of RTLS systems support the decision-making process with a simulation in a real test environment. There, it is shown how much hardware it would take to install an RTLS solution in order to realize certain defined results. This way, you know what you can expect for your money even before you buy. Kathrein and its partners will also provide you with an offer that is realistic for your requirements.

Conclusion

The advantages of an RTLS system are obvious. Why you should invest in this technology must be examined on the basis of your individual area of application and by means of relevant key figures. Only in this way will you contain a good basis for decision-making based on valid information. Seeing for yourself in a real test environment what effects an RTLS tracking system brings makes sense in any case. You get a feeling for the costs and, above all, for the savings potential of future costs. In addition, you bring your manufacturing to a digitalized automation level that prepares for IoT and Smart Factory.