Tradition Group offers a solution in partnership with Fraunhofer ALI and based on Ubisense technologies to locate, track, record and analyze the movement of any mobile object inside any building or enclosed space to an accuracy of up to 15 cm in 3D in real time using ultra-wideband. Visualization of objects in 3D and control of the Ubisense sensor network is integrated into the Lockey™ web service.

To determine the object’s location the path from transmitter (special Ubisense active tags are used) to receiver (Ubisense sensors) is measured, here only the direct path signal determines object’s true location, reflections are errors.

With conventional RF, reflections in in-building environments distort the direct path signal, making accurate pulse timing difficult. With UWB the direct path signal can be distinguished from the reflections, making pulse timing easier. Sensors are grouped into cells which are typically rectangular in shape with additional sensors being added to a cell depending on the geometry of the area to be covered. In each cell a master sensor coordinates the activities of the other sensors and communicates with all the tag whose location is detected within a cell. By designing overlapping cells, it is possible to cover very large areas in a similar way to the cellular layout of a mobile telephone network.

Tag locations are sent via standard Ethernet cable or wireless LAN to the Location Engine software which aggregates the data and passes the information via an API to an external program or to the Ubisense Location Platform for visualisation and spatial processing. As tags move between cells, the responsibility for locating them passes seamlessly and automatically from one master sensor to the next. When setting up the system, one 3D co-ordinate reference grid is specified for the whole multi-cell configuration. The visualisation module displays the tags in real-time as they move around the reference grid, irrespective of which cell currently contains them.

The system can work in different modes depending on the location accuracy required.

 Presence Only Mode

The following mode requires minimal infrastructure costs for situations where precise location is not needed and is used when you simply need to determine whether an object or a person is «there» without knowing exact coordinates (e.g. on a particular floor or somewhere on the premises) or when you need to identify something in a very close proximity (e.g. a person walks past a sensor).  

In the presence mode, sensors and tags communicate only using 2.4 GHz control channel. Tag’s presence is determined based upon being heard by one or more sensor that can be adjusted to extend or limit range as appropriate.

Infrastructure requirements:

• 1-2 Ubisense sensors;
• 2-3 tags per object (in 2D);
• USB-stick – covered area is 10 – 50 m, depending on environmental conditions, i.e. disturbances
• USB-stick and +8 dBi-antenna – up to 120 m;
• USB-stick and vectored +20 dBi antenna – up to 500 m, where area covered depends on beaming characteristics of the vectored antenna.

High-precision location mode

To ensure a high quality object localization (accuracy up to 15-30 cm) and to construct a 3D model of the zone, it is required that sensors are installed every 20-25 m (worst case, due to probable reflections and shadowing in the aisles). For example, an area of 500-625 sq.m will require 4 sensors. Every object tracked will also require up to 3 tags. 

Technology: main characteristics

• Extremely durable equipment. Tags are available in rugged industrial casings, designed to be robust against mechanical damage and protect against dust and dampness. Requirements for extended temperature ranges can be accommodated. There are two kinds of tag available for various applications: the slim and the compact tag.
• Application flexibility. A considerable range of options exist to design a system to meet the needs of the application and the physical environment. Typical parameters are the geometry of the area and the materials present, the required accuracy in different areas, which objects will have tags attached to them and what speed of movement is usual, what actions and interactions are expected between the objects and the fixed or untagged assets, desired battery life, available power and Ethernet cabling, presence of other RF systems and many more.
• Economical. The tags will only transmit UWB signals when a sensor requests them to do so and the rate of UWB transmission (i.e. the update rate of the tag) is driven by the sensors. Tags transmit pulses with very low power (less than 1 mW) which minimizes the interference risk with other RF systems and ensures a long battery life. For example, at a continuous update every five seconds, the battery will last more than five years.

• Interactivity. The slim tag, designed to be carried by a person or fixed to an object, has two buttons whose meaning may be configured in the application, for example, to lock or unlock a nearby remote controlled door. There are also two LEDs and a buzzer which can be activated by the application to provide feedback, perhaps to identify a specific tag to a worker when many are close together or provide an audible warning if a worker is entering a dangerous area.