Apr 03, 2022"Traceability" has become a buzzword in the manufacturing industry, as plant managers and executives work tirelessly to improve the speed and accuracy of their operations. To that end, real-time location systems (RTLS) have become invaluable. RTLS solutions use radio frequency identification (RFID)-based technology to provide factory workers with the exact location and station at which a specific item can be found within their factories.
In most systems, wireless tags are attached to objects, with fixed reference points receiving wireless signals from these tags to identify the objects' locations. However, real-time location systems can differ significantly in how they operate. They utilize a variety of active RFID technologies, each offering its own set of positives and negatives, providing a range of price points and varying accuracy.
Depending on the specific needs of a manufacturing operation, one RTLS technology may meet operational needs better than others. Let's look at three common active RFID technologies—sub-gigahertz (sub-GHz), ultra-wideband (UWB) and Bluetooth Low Energy (BLE)—as well as their unique traits and common manufacturing applications.
Sub-Gigahertz
The term "sub-gigahertz" can identify any wireless technology that utilizes a frequency band less than 1 gigahertz (GHz). This common type of tech can be found in a variety of applications, such as handheld wireless home utility meter-readers. Using a relatively small amount of power, sub-GHz signals travel distances greater than the ranges reached by higher RTLS frequency signals. In some cases, sub-GHz technology can transmit information over a distance of several kilometers.
For RTLS applications, the key drawback of sub-GHz technology (as compared to higher-frequency RTLS) is decreased accuracy, which is primarily due to longer wavelengths used by sub-GHz. As a result, sub-GHz may not reach a level of accuracy that many manufacturing operations require. For example, while sub-GHz could identify a vehicle's general location in a parking lot to within several car-lengths, it would not be able to identify a bin's specific location inside a factory.
These traits make sub-GHz an ideal technology for applications that need to track assets outside of factory walls. If an automotive manufacturer requires tracking of vehicles in a parking lot, or if a contractor wants to find the general location of equipment spread across a large construction site, sub-GHz technology would be a great fit to integrate within their real-time location systems.
Ultra-wideband
UWB, by far the most accurate active RFID-based technology for real-time location systems, can identify an object's location within 10 centimeters (3.9 inches) of accuracy. The technology uses time difference of arrival (TDoA), a technique that measures the difference in the time-of-flight of a tracked object's transmissions, to triangulate on that object's location. Additionally, by using multiple receive antennas, fixed receivers may determine the angle-of-arrival (AoA), further improving the location accuracy of the tracked object. By using TDoA, and optionally AoA, multiple fixed receivers work together to determine an object's precise location.
The biggest drawbacks for UWB RTLS over sub-GHZ and BLE are the higher price point and the increased power required for transmissions. At the component level, a UWB device must be added to the bill of materials for each device being tracked. Typically, the tracked devices each contain a BLE radio for communications. UWB's superior accuracy makes it an ideal fit for manufacturing operations where specific parts on pallets need to be located. While BLE can deliver much of the same accuracy across the floor, UWB is the way to go for locating relatively small individual items.
Bluetooth Low Energy
Of the three RTLS technologies discussed, BLE hits a sweet spot between price (lowest) and accuracy (acceptable for most applications). The commercial availability of BLE technology, with widespread applications ranging from cell phones to car radios, has dramatically lowered the cost of implementing RTLS with BLE, increasing the potential for adopting BLE technology for use in real-time location systems. Furthermore, BLE can generate sub-meter accuracy, making it an attractive option for most manufacturing operations needing to locate assets within a factory.
BLE technology is globally supported and standards-based. Hence, devices that incorporate BLE chips can support RTLS—but unless the chips are specifically programmed for RTLS, they will not be usable in real-time location systems. This combination of low cost and acceptable accuracy makes BLE a strong fit for operations located entirely within factory walls. Plant managers can know the location of an asset or a pallet at any given time, within roughly 1 meter (3.3 feet).
Each of these technologies comes with its own unique benefits and drawbacks. The important takeaway is to work with your solution provider to determine which type of active RFID best suits your factory operations, enabling you to improve operational efficiency for your business.
Richard Lourette leads the product engineering team at Panasonic's Industrial Internet of Things (IoT) Division. His background in engineering spans several decades, ranging from consumer electronics products such as digital cameras and smart rings to developing payload test equipment (including RF) for GPS III navigational satellites recently launched by the U.S. Space Force. Additionally, his background includes a long history of geolocation projects. Richard holds more than 20 U.S. patents and many foreign patents.
