BACKGROUND

[0001] Industrial plant operators need a simple, cost effective and accurate means for maintaining location awareness of personnel and critical assets within their facilities. Typical use cases include safety mustering, man-down detection, mobile worker enhancements (for example location aware augmented reality), geo fencing, plant security and many others. Current location awareness solutions are costly to purchase and install and often require months to fine tune to the characteristics of the local environment. Even after tuning, physical and environmental plant changes over time can degrade the accuracy of the system. Global Positioning Systems (GPS) are not suitable for indoor position monitoring or in outdoor heavy infrastructure.

[0002] A Positioning System (PS) is a network of devices used to wirelessly locate objects or people inside a building or within dense industrial areas. A special design is required since global positioning system (GPS) systems are typically not suitable to establish indoor locations or other crowded locations as they require an unobstructed line of sight to four or more GPS satellites. Microwaves will be attenuated and scattered by roofs, walls and other objects and multiple reflections at surfaces cause multipath propagation serving for uncontrollable errors.

[0003] Ranging may use one or more of a variety of methods, but they may require a complicated synchronization mechanism to maintain a reliable source of time for sensors, or suffer from large multipath conditions in localization situations with dense populations, such as indoor locations and industrial environments which can be crowded, which is caused by the reflection and diffraction of the RF signal from objects.

[0004] Due to the attenuation and reflections caused by construction materials, it is desirable to have an unobstructed line of sight to at least three anchor points at any location that should be covered by the system. As a result, a larger number of anchor stations are required.

SUMMARY

[0005] A location awareness system including a communication network, and a network operating element coupled to the communication network. At least one anchor network gateway is coupled to the communication network, the at least one anchor network gateway configured to generate a wireless anchor network. A plurality of anchors are configured to couple to one of the at least one anchor network gateway via its respective wireless anchor network. A plurality of tags is each configured to communicate with at least one anchor to provide ranging information for determination of a position of the tag within an area covered by the system.

[0006] A method of position location of a plurality of tags in a system includes providing a first network with a network operating element coupled to the first network, and providing at least one anchor network gateway coupled to the first network, the at least one anchor network gateway providing an anchor network. A network of a plurality of fixed position anchors is formed and configured to communicate via ranging with the plurality of tags and via the at least one anchor network to the at least one anchor network gateway. The system is operated using accurate timing within networked wireless communication protocols to provide a global location network schedule for the system.

[0007] A method of ranging a plurality of tags in a system includes using accurate timing of an existing industrial time division multiple access wireless communication protocol to provide a global location network schedule for the system. The method further includes providing a plurality of anchor networks via a plurality of network anchor gateways, and providing a plurality of fixed location anchors coupled to at least one of the plurality of anchor networks, the plurality of anchors providing a plurality of tag to anchor networks. The plurality of tags, plurality of anchors, the anchor networks, and the tag to anchor networks have a shared sense of time.

[0008] A location awareness system includes a plurality of tags, a plurality of anchors, and a plurality of anchor network gateways for communication between tags and anchors, the plurality of network anchor gateways providing a plurality of anchor networks, and the plurality of anchors providing a plurality of anchor to tag networks. A network operating element is coupled to the plurality of anchor network gateways, the network operating element configured to range the plurality of tags. The plurality of tags is ranged using a method of using accurate timing of an existing industrial time division multiple access wireless communication protocol to provide a global location network schedule for the system. The plurality of tags, plurality of anchors, the anchor networks, and the anchor to tag networks have a shared sense of time. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a location awareness system diagram.

[0010] Figure 2 is an example location and wireless anchor network time alignment.

[0011] Figure 3A is a rear isometric view of a personnel location tag design example.

[0012] Figure 3B is a rear elevation of the personnel location tag design of Figure 3A.

[0013] Figure 3C is a front isometric view of the personnel location tag design of Figure 3A.

[0014] Figure 3D is a front elevation view of the personnel location tag design of Figure 3A.

[0015] Figure 4A is a rear isometric view of a location anchor design example.

[0016] Figure 4B is a rear elevation of the location anchor design of Figure 4A.

[0017] Figure 4C is a front isometric view of the location anchor design of Figure 4A.

[0018] Figure 4D is a front elevation view of the location anchor design of Figure 4A.

[0019] Figure 5 is a schematic view of a tag architecture.

[0020] Figure 6 is a schematic view of an anchor architecture.

DETAIFED DESCRIPTION OF IFFUSTRATIVE EMBODIMENTS

[0021] The present disclosure provides embodiments of a location awareness system for achieving location awareness of assets and/or personnel within a typical industrial plant is provided. Awareness of the location of critical assets within an industrial plant is an important element in the safe and efficient operation of the plant. Currently available systems are costly, complex, and do not provide the performance required by typical industrial plant operators. This disclosure builds on existing technology to provide a simple to deploy, relatively low cost, accurate location awareness system.

[0022] Many industrial environments use low power industrial communications networks for communication of various components and elements within the industrial environment. Embodiments of the present disclosure build on such existing low power industrial communication and ranging technologies to achieve a location awareness system that performs better than existing solutions at a reduced cost of ownership.

[0023] A general positioning system (PS) (e.g., system 100 described further below) comprises a network of devices used to wirelessly locate objects or people inside a building or within dense industrial areas. A special design is required since global positioning system (GPS) systems are typically not suitable to establish indoor locations or other crowded locations as they require an unobstructed line of sight to four or more GPS satellites. The GPS signal or the RF signal used for GPS will be attenuated and scattered by roofs, walls and other objects and multiple reflections at surfaces cause multipath propagation serving for uncontrollable errors.

[0024] Ranging methods that may be employed in embodiments of the present disclosure include time of flight (ToF), Time Difference of Arrival, Angle of Arrival, signal strength, phase angle measurement, etc. The choice of a ranging method may depend on conditions and desired accuracy and ease of implantation, for example.

[0025] Figure 1 shows a simplified block diagram of a location awareness system 100 according to an embodiment of the present disclosure. System 100 comprises in one embodiment a network 102 to which further components of the system 100 are coupled. Network 102 may be, for example, a high bandwidth wired or wireless network, such as Ethernet, Wi-Fi, or the like. A plurality of wireless anchor network gateways 104 are coupled to the network 102, and each wireless anchor network gateway 104 provides a wireless anchor network 105. A plurality of anchors 106 are coupled to each wireless anchor network gateway 104 through the wireless anchor networks 105. Personnel tags 108 and asset tags 110, which are associated respectively with system personnel and system assets, are in wireless communication with one or more anchors 106 with ranging pulses, such as are described in greater detail below.

[0026] In addition to the wireless anchor network gateways 104 that are coupled to the network 102, additional software and/or hardware used to provide support for the wireless anchor network gateways 104 is also coupled to the network 102. In one embodiment, components coupled to the network 102 comprise a network operating element 111 which includes in one embodiment time-division multiple access (TDM A) location network manager 112, a location calculation engine 114, a location system user interface 116, and a time source 118, each of which is described in greater detail below. The components 112, 114, 116, and 118 are used in one embodiment to provide timing information and operation for the system in conjunction with ranging information for the tags 108, 110 received through anchors 106 and wireless network anchor gateways 104.

[0027] TDMA is a known standard for sharing a frequency channel on a network, by dividing the signal into multiple time slots. Each wireless network anchor gateway 104, for example, may share the frequency being used for communication signals by being assigned a specific time slot for transmissions. Time slots for wireless network anchor gateways 104 are in one embodiment assigned by the TDMA location network manager 112. Any appropriate communication technique may be employed including CDMA techniques or other time and/or frequency slotting or sharing techniques.

[0028] In one embodiment, anchors 106 are distributed around an area, such as a manufacturing facility, in one embodiment in a grid pattern that covers the area to be monitored. In one embodiment, anchors 106 are distributed about a facility in a grid pattern with spacing of about 50 meters. Personnel tags 108 and asset tags 110 range to the grid of anchors in one embodiment using signal strength on an anchor to tag communication network 107. Based on the strength of ranging signals of tags 108 and 110 to the grid of anchors 106, the positions of tags 108 and 110 are ranged by the anchors 106. Anchor to tag communication or network 107 may use a series of ranging pulses and communication on a network such as the mesh networks described herein, or on another network such as an ultrawide band network or the like.

[0029] Once anchors 106 have the ranging data to the plurality of tags 108 and 110, the range data is conveyed within the system 100 to their respective gateways 104 via the plurality of wireless anchor networks 105. In one embodiment, the gateways 104 are also arranged in a grid pattern that covers the area to be monitored. In one embodiment, gateways 104 are distributed about a facility in a grid pattern with spacing of about 200 meters. The gateways 104 receive ranging information from the anchors 106, and convey that ranging information within system 100 to components coupled to the network 102.

[0030] Personnel tags 108 and asset tags 110 range to the grid of anchors in one embodiment using signal strength. Based on the strength of ranging signals of tags 108 and 110 to the grid of anchors 106, the positions of tags 108 and 110 are ranged by the anchors 106. Ranging data from the tags 108, 110 is passed to location calculation engine 114 for determining positioning of the tags 108, 110 relative to each anchor 106. Location may then be determined based on a known location of the anchors 106.

[0031] Location Awareness System Overview:

[0032] As shown and described above, the system 100 uses a matrix of low power anchors 106 that are mounted to fixed points within a facility. These anchors 106 are in one embodiment battery powered wireless devices which can be deployed for a fraction of the cost of other types of anchors that must be wired to power and communication lines. The costs of running wires in a hazardous plant environment can easily dwarf the cost of the anchors themselves.

[0033] The anchors 106 of the various embodiments within system 100 may employ any of a number of industrial or commercial wireless communication technologies including but not limited to IEC 62591 (WirelessHART) and IEC 62734 (ISAlOO.l la). The WirelessHART protocol was designed specifically to address the challenging environment that exists in most industrial plants including heavy infrastructure, electrical noise, congested RF bands, and the presence of flammable and explosive materials. The location awareness system 100 builds on self organizing multi-hop mesh protocols such as WirelessHART by taking advantage of the accurate timing of these TDMA-based protocols to produce an orthogonal schedule for conducting single or multi-spectral ranging to a large number of mobile personnel tags 108 and asset tags 110. Time division multiple access uses ultra-low power, time deterministic ranging to a large number of tags 108, 110 in a congested RF environment. The schedule makes it possible for both tags 108, 110 and anchors 106 to synchronize their operations (communicating and ranging) for high efficiency.

[0034] To allow the system 100 to cover a user's entire facility, more than one wireless anchor network 105 is likely to be deployed from more than one wireless anchor network gateway 104. When multiple wireless anchor networks 105 are employed at a facility, the location awareness system 100 maintains a shared sense of time between components. In one embodiment, the system-global sense of time along with a schedule generated by the TDMA location network manager 112 and transmitted to the anchors 106 and tags 108, 110 makes it possible for the system 100 to operate very efficiently with many tags 108, 110 without self- interference.

[0035] Location Network Timing Detail:

[0036] The TDMA location network manager 112 communicates its timing information to each anchor 106 and tag 108, 1 10. For example, using an available precision time source 118 (e.g. using a Precision Time Protocol- PTP source connected to the network 102), the TDMA location network manager 112 timestamps the beginning of its first schedule slot. Each subsequent slot is a precise duration (e.g. 10 ms) and is numbered sequentially. This timestamp is propagated to each anchor 106 and tag 108, 110 through the wireless anchor networks 105 and the anchor to tag communication network 107. The anchors 106 and tags 108, 1 10 use this information to time align their local anchor to tag transmit, receive, and ranging slots as programmed by the TDMA location network manager 1 12.

[0037] The anchors 106 maintain their sense of time using the wireless anchor networks 105 which also provide timing information for a particular schedule slot on demand. This continuously updated time is shared between the anchors 106 and tags 108, 110 to maintain alignment over time and temperature for all constituents of the location awareness system 100.

[0038] Location calculation engine 114 works in conjunction with TDMA location network manager to determine position locations for the tags 108, 110, wdth the ranging information received along network 102 from the wireless anchor network gateways 104 via anchors 106 from tags 108, 110. Location system user interface 116 allows a user to see and use ranging and position information for operations and the like within a facility.

[0039] Time is passed from a central time source 118 over the network 102 to the wireless anchor network gateways 104. Gateways 104 pass the time on to the anchors 106 over wireless anchor networks 105. Anchors 106 pass the time on to the tags 108, 110 on network 107. Once all components of system 100 have a common sense of time, operation of the system is made with time synchronized communications and ranging.

[0040] For example, synchronization could be accomplished by sending time pulses at a very high rate, such as once every microsecond. However, such a high rate of sending time pulses is power intensive, and with many anchors 106 operating on at least partial battery power, is inefficient and wasteful. Instead, time pulses are sent in one embodiment less frequently (for example, once per minute to maintain acceptable timing guardbands), and use a microprocessor clock to perform between-pulse timing. In one embodiment, in order to achieve target battery life, a lms time synchronization may be used across different anchor networks. Microprocessors may be employed in anchors, 106, wireless anchor network gateways, and the like, and can provide timing signals for some amount of time. However, over time, microprocessor clocks can drift, and a synchronized clock is used to refresh the timing of microprocessor clocks on a regular basis. In one embodiment, this is done with propagation of a timing signal from precision time source 118 over network 102 to wireless anchor network gateways 104, over networks 105 to anchors 106, and over network 107 to tags 108, 110.

[0041] Figure 2 shows the use of a system 100 global precision time source (e.g., 118) to align the location network schedules of independent anchor networks 105 within system 100. An anchor 106 local sense of time may be corrected to a location network schedule provided by TDMA location network manager 112 and precision time source 118, using an anchor network specific offset value (TANO, TANI, etc.).

[0042] Ranging Spectrum:

[0043] In one embodiment of the system 100, anchors 106 and tags 108, 110 communicate and range using a different part of the radio frequency (RF) spectrum than the wireless anchor networks 105 and therefore, the tag location communication or network 107 does not use any knowledge of the wireless anchor network 105 schedule. For example, the wireless anchor networks 105 may use 2.4 GHz industrial scientific and medical (ISM) portion of the RF spectrum. In this configuration, communication and ranging between anchors 106 and tags 108, 110 is done in another portion of the RF spectrum such as the unlicensed 900 MHz (U.S.) or 860 MHz (EU) bands. In another embodiment, the anchors 106 and tags 108, 110 range and communicate using wide-band, ultra-wide band or ultrasonic spectrum communications. The use of a completely different spectrum to range and communicate between the anchors 106 and tags 108, 110 makes it possible for the wireless anchor network schedule and the location network schedule to be completely independent and overlapping, while still achieving high efficiency operation that is free from interference.

[0044] In another embodiment, the system 100 has anchors 106 and tags 108, 110, as well as wireless anchor networks 105, sharing the same spectrum (in one embodiment, the 2.4 GHz band). Such an embodiment simplifies global deployments. The 2.4 GHz band is globally harmonized, while sub-GHz bands are not. In the case of an overlapping spectrum, more efficient sharing may be accomplished, for example, by employing blacklisting features of WirelessHART.

[0045] As shown in FIG. 2, precision time source 118 keeps a precision time that is used for synchronization of system 100. Propagation of a precision time signal from the precision time source 118 is provided on a location network schedule 202 having slots 204 of a certain predetermined time duration. Wireless anchor networks 105 , 105 ₂ , ..., l05 _n have anchor network specific offset values TANO, TANI, · · · , TAN _H ) that allow all wireless anchor networks to operate on the same time schedule. For example, wireless anchor network 105] operates in slots 206, wireless anchor network 105 ₂ operates in slots 208, and wireless anchor network 105 _n operates in slots 210, with the timing for each of the wireless anchor networks 105 synchronized as discussed. The shared known timing is passed from wireless anchor networks 105 to anchors 106 and then to tags 108, 110 as synchronization occurs.

[0046] System 100 Component Details:

[0047] Tags (personnel 108 or asset 110):

[0048] Tags 108, 110 are in one embodiment low power electronic devices that are attached to personnel (tags 108) and critical assets (tags 110) within the plant or facility. Rear isometric, rear elevation, front isometric, and front elevation views of a design of a representative personnel tag 108 are shown, respectively, in FIGS. 3A, 3B, 3C, and 3D. A block diagram of one architecture embodiment of tag 108, 110 is shown in FIG. 5. FIG. 5 shows tag 108, 110 comprising an accelerometer 502, a ranging element or system 504, and an anchor to tag communication element 506. Operation of tags 108, 110 is known and will not be described further herein.

[0049] Power for tags 108, 110 is provided in one embodiment by a primary or secondary cell battery. When a secondary cell battery is used, it may be recharged in various ways including but not limited to plug-in and inductively coupled proximity charging. In order to extend battery life, in one embodimen the tags 108, 110 include accelerometer 502 or other component to allow the tag to enter a low power sleep state when it has been stationary for a specified time period. When in the low power stationary state, the tag 108, 110 can report its position at a significantly reduced rate.

[0050] Each tag includes a ranging module 504 compatible with one or more of the ranging modules in the deployed anchors 106. Ranging capabilities may include one or more of the following:

a. narrow band RF signal strength

h. narrow band RF time of flight (one-way and two-way)

c. narrow band RF beaconing d. wide band RF signal strength

e. wide band RF time of flight (one-way, two-way, and three-way)

f. wide band RF beaconing

g. GPS

h. ultrasonic time of flight (one-way and two-way)

i. hybrid narrow' band RF and ultrasonic where the narrow' band RF

pulse is used for time synchronization between the tag and the

anchor

j. combinations of the above techniques

[0051] Tags 108, 110 may further include components to support dead reckoning location awareness such as but not limited to gyroscopes, magnetometers, and accelerometers (502). Tags 108, 110 may also contain proximity detection hardware such as an RFID tag or an inductive coupling to a fixed exciter positioned at a gate or doorway of the facility or section of the facility. Data from these components may or may not be filtered in the tag 108, 110 prior to transmission over the anchor to tag communication network 107. Ranging and dead reckoning data is transmitted to one or more wireless anchor network gateways 104 and then to the location calculation engine 114 over network 102 for processing along with other ranging information to establish a high- confidence location for the tags 108, 110.

[0052] In one embodiment, tags are provisioned out of band (using non-operational means) to securely join the location awareness system 100. A tag is provided with a unique ID that is then associated with a particular asset or personnel. When entering operation, the tag 108, 110 reports its presence to the TDMA location network manager (TLNM) 112 using a secure location join key.

[0053] As tags 108, 1 10 may be deployed in hazardous locations, tags arc designed in one embodiment as self-contained battery powered intrinsically safe devices. The tags 108, 110 may also adhere to electrical equipment shock and fire hazard requirements as well as electromagnetic compatibility (EMC) and spectrum usage requirements.

[0054] In additional embodiments, tags may incorporate other features such as status indicators (e.g. LED) indicating the health of a tag 108, 110 as well as the state of its internal battery. The tags may also incorporate measurement functions to detect environmental parameters such as temperature, humidity, and gas concentration. Personnel tags 108 may also incorporate biometric measurements such as heart rate, respiration rate, skin temperature, body position and the like. Tags may also incorporate a panic button that a user can activate to request assistance. All of the parameters mentioned above are communicated back to a host system using the anchor to tag networks 107 and wireless anchor networks 105. The host system can then take action such as notifying plant emergency response and safety personnel.

[0055] Rear isometric, rear elevation, front isometric, and front elevation views of a design of a representative anchor 106 are shown, respectively, in FIGS. 4A, 4B, 4C, and 4D. A block diagram of one architecture embodiment of anchor 106 is shown in FIG. 6. FIG. 6 shows anchor 106 comprising a wireless anchor network radio 602, a ranging element or system 604, and an anchor to tag communication element 606.

[0056] Anchors 106 are in one embodiment battery or line powered devices that have fixed and known positions. Anchors 106 securely communicate with tags 108, 1 10 within range and use single or multi- spectral means to determine the distance from the anchor 106 to each tracked tag 108, 110. In one embodiment, anchors 106 are members of an industry standard mesh network used to relay tag ranging and health information to a location calculation engine 114.

[0057] To be cost effective, an anchor 106 may be a self-contained battery powered wireless device with battery life in the range of 5 to 10 years. The development and use of such anchors 106 helps overcome a major cost drawback of existing systems. Many existing systems rely on expensive to purchase and install wired equipment such as industrial grade Wi-Fi access points. Anchors 106 could also be line powered when reliable d.c. power is available. For example, anchors 106 may be integrated into industrial lighting systems.

[0058] In one embodiment, anchors 106 communicate with the tags 108, 110 over a network or networks 107 using a variety of ways including narrow and wide band RF. The anchors 106 may form a network with each other using existing wireless sensor field protocols such as WirelessHART, ISA100, or BLE Mesh. In one embodiment, this communication uses a frequency band different from that used to communicate and range between the tags 108, 110 and anchors 106. This avoids any coexistence issues between these two parts of the system 100.

[0059] Anchors 106 employ ranging techniques matching those of the tags 108, 1 10 in the system. Additionally, anchors 106 may periodically range to each other to continuously assess important characteristics affecting range measurement in the local area. For example, anchors may use RF signal strength measurement between themselves to continuously assess changes in the RF environment including propagation, reflection and absorption coefficients. Since the fixed position of each anchor is known to the location calculation engine 114, the anchor to anchor ranging information may be used to continuously improve the range measurement between tags and anchors. Anchors 106 may also incorporate GPS functions to help determine their position without requiring an installer to input this fixed position information.

[0060] Each anchor 106 is in one embodiment securely joined to a wireless anchor network 105 using the provisions of the wireless sensor networking protocol that it employs (e.g. WirelessHART or ISA100). During operation, the TLNM 112 establishes a schedule for the anchor 106 to range and communicate with selected tags 108, 110 in the vicinity of the anchor 106. The anchor's participation within the anchor mesh network is independently managed by an anchor network manager which typically runs in an anchor network manager gateway or as a remote application.

[0061] As the anchors 106 may be deployed in hazardous locations, they are designed as self-contained battery powered intrinsically safe devices. The anchors 106 may also adhere to electrical equipment shock and fire hazard requirements as well as EMC and spectrum usage requirements.

[0062] Embodiments of the present disclosure provide an industrial location awareness system that can accurately track the position of personnel and critical assets. A method of using industrial TDMA wireless communication protocols (e.g., WirelessHART, ISA, lOO.lla, BLE, etc.) to form a network of fixed position anchors is also provided. The method provides performance and cost advantages over existing systems such as Wi-Fi based systems, Bluetooth beaconing systems, GPS systems, and dead reckoning systems.

[0063] In another embodiment, a method of using accurate timing within industrial TDMA wireless communication protocols provides a global location network schedule, such that a system (e.g., system 100) has more power and bandwidth efficiency and allows the system to track the position of thousands of tags in a single facility without any possibility of self interference. [0064] In another embodiment, a method of using a frequency spectrum different from that of the anchor communication network to communicate and range between anchors and tags is provided. In such a configuration, the anchor network and location network schedules operate independently by reducing the complexity of the system while increasing bandwidth for both communication and ranging.

[0065] In another embodiment, a method of using accurate timing of existing industrial TDMA wireless communication protocols to provide a global location network schedule propagating a shared sense of time to a plurality of wireless anchor networks and a plurality of anchor to tag networks, wherein components of the system including wireless anchor network gateways, anchors, and tags have a shared sense of time and the schedule generated by a location network manager.

[0066] Although the present disclosure has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the disclosure.