WO2019246049A1 - A real-time location system (rtls) that uses a combination of event sensors and rssi measurements to determine room-and-bay-location of tags - Google Patents

A real-time location system (rtls) that uses a combination of event sensors and rssi measurements to determine room-and-bay-location of tags Download PDF

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Publication number
WO2019246049A1
WO2019246049A1 PCT/US2019/037667 US2019037667W WO2019246049A1 WO 2019246049 A1 WO2019246049 A1 WO 2019246049A1 US 2019037667 W US2019037667 W US 2019037667W WO 2019246049 A1 WO2019246049 A1 WO 2019246049A1
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WIPO (PCT)
Prior art keywords
room
bay
level
tag
location
Prior art date
Application number
PCT/US2019/037667
Other languages
French (fr)
Other versions
WO2019246049A8 (en
Inventor
John A. SWART
Original Assignee
Infinite Leap Holdings, Llc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US16/010,747 external-priority patent/US10251020B1/en
Priority claimed from US16/010,732 external-priority patent/US10231078B1/en
Priority claimed from US16/214,890 external-priority patent/US10390182B2/en
Priority claimed from US16/214,979 external-priority patent/US10412700B2/en
Priority claimed from US16/241,737 external-priority patent/US10354104B2/en
Application filed by Infinite Leap Holdings, Llc filed Critical Infinite Leap Holdings, Llc
Priority to EP19822878.5A priority Critical patent/EP3807853A1/en
Publication of WO2019246049A1 publication Critical patent/WO2019246049A1/en
Publication of WO2019246049A8 publication Critical patent/WO2019246049A8/en

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Classifications

    • G—PHYSICS
    • G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
    • G16H—HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA
    • G16H40/00—ICT specially adapted for the management or administration of healthcare resources or facilities; ICT specially adapted for the management or operation of medical equipment or devices
    • G16H40/20—ICT specially adapted for the management or administration of healthcare resources or facilities; ICT specially adapted for the management or operation of medical equipment or devices for the management or administration of healthcare resources or facilities, e.g. managing hospital staff or surgery rooms
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/0257—Hybrid positioning
    • G01S5/0258—Hybrid positioning by combining or switching between measurements derived from different systems
    • G01S5/02585—Hybrid positioning by combining or switching between measurements derived from different systems at least one of the measurements being a non-radio measurement
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/0009—Transmission of position information to remote stations
    • G01S5/0018—Transmission from mobile station to base station
    • G01S5/0036—Transmission from mobile station to base station of measured values, i.e. measurement on mobile and position calculation on base station
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/0257—Hybrid positioning
    • G01S5/0263—Hybrid positioning by combining or switching between positions derived from two or more separate positioning systems
    • G01S5/0264—Hybrid positioning by combining or switching between positions derived from two or more separate positioning systems at least one of the systems being a non-radio wave positioning system
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/0269—Inferred or constrained positioning, e.g. employing knowledge of the physical or electromagnetic environment, state of motion or other contextual information to infer or constrain a position
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
    • A61B5/1113—Local tracking of patients, e.g. in a hospital or private home
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S2205/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S2205/01—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations specially adapted for specific applications
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S2205/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S2205/01—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations specially adapted for specific applications
    • G01S2205/02—Indoor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S2205/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S2205/01—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations specially adapted for specific applications
    • G01S2205/09—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations specially adapted for specific applications for tracking people
    • G01S2205/10—Elderly or infirm

Definitions

  • the present invention relates generally to a real-time location system (RTLS) having active tags, bridges, and room-level, bed-level, or-bay-level event sensors, that pass sufficient sensor data to a location engine in a central server, to locate tags at room-level, bed-level, and bay-level inside a building such as a hospital.
  • RTLS real-time location system
  • RTLS systems estimate locations for moving tags or moving personnel badges within a floor plan of interior rooms, in buildings such as hospitals.
  • Many RTLS systems based on radio-frequency signals such as Wi-Fi or Bluetooth Low Energy (BLE) are designed to have moving tags that transmit a radio signal, within a field of receiving devices called bridges, gateways, sensors, or Access Points.
  • a network of bridges will measure and use received signal strength of transmissions from a tag, as a proxy for estimating the distance between the tag and each bridge, and then use multi-lateration algorithms to estimate the locations of tags.
  • Those approaches with tags that transmit are standard in the industry and provide location estimates that are acceptable for may use cases in industrial and manufacturing environments.
  • Hospitals typically have several, large, patient-care rooms where may patients can be treated simultaneously, such as an ED receiving room, a prepare- for-surgery room, a recovery-from-surgery room, or an infusion room. These large rooms are designed with a set of small bays, where each bay is defined as a treatment area for one patient.
  • Each bay usually has enough floor space to hold one bed, and/or one chair, for a patient to lie in or sit in.
  • the bays may be separated by a curtain.
  • the curtain may be suspended from a track in the ceiling of the bay, which allows a curtain to be drawn or retracted to provide a private space for the patient’s care.
  • the bays may alternatively be divided by a structural half- wall or other privacy structure.
  • Hospitals also have patient rooms for inpatients which are shared by two or more patients in two or more beds.
  • the beds in these shared multi-patient rooms are typically separated by a curtain.
  • RTLS systems in hospitals in common use may be able to determine or estimate the location of tagged assets, patients and staff members with 1 -meter accuracy, but RTLS systems in common use fail to determine reliably which room or bay the tag resides in.
  • the common RTLS system struggles to determine which side of a wall the tag resides on, because the common RTLS system uses only radio signals for location information, and the radio signals travel through the wall.
  • the common RTLS system struggles to determine which side of a curtain a tag resides on.
  • a better location system is required that can reliably determine which side of a wall or curtain a tag resides on, so the hospital can determine which room or bay a patient is seated in, and which caregivers are in the room or bay with the patient, and determine which assets are in the room or bay with the patient.
  • RTLS systems in common use fail to determine which bed a tag resides on or near, in a multi patient room.
  • Tagged assets may be placed on shelves along that shared wall, just 20 centimeters apart from each other, separated by a wall.
  • An RTLS-system lookup for clean equipment needs to report all assets in the clean-equipment room, and none of the equipment in the soiled-equipment room.
  • An RTLS system that uses radio-signals may be able to estimate a location for a tagged asset within 1 -meter accuracy, but still struggle to answer the question of precisely which side of the wall the tagged asset is on because the tags are only 20 centimeters apart.
  • Some RTLS systems have used infrared light or ultrasound signals to determine the precise room-level location of each tagged asset, but these systems require significant design, engineering, tuning, and cost.
  • RTLS system To further illustrate the accuracy problem, imagine a hospital patient-care area that is a large room, hosting many patients, divided into bays. Patients may sit in beds or lie or chairs just 1 meter apart from each other, separated by a curtain.
  • an RTLS system must be accurate enough to determine which bed, chair or bay a patient is located in, and also determine which pieces of medical equipment are in the same bay with that patient, and also determine which staff members are in the same bay with that patient.
  • An RTLS system that uses radio-signals may be able to estimate a location for a patient, asset or staff member within 1 -meter accuracy, but still struggle to answer the question of precisely which side of the curtain the tagged asset, patient or staff member is on because the patients are only 1 meter apart.
  • RTLS systems have used infrared light or ultrasound signals to build“virtual walls” where the curtains separate the bays, but these systems require significant design, engineering, tuning, and cost.
  • a room-level event sensor is defined as an electronic sensing device that can determine whether movement occurs in the room where it is placed.
  • a room-level event sensor is a passive-infrared motion sensor.
  • two room-level motion sensors are placed in two rooms on opposite sides of a shared wall. For this illustration, we can assume that one room holds clean equipment and the other room holds soiled equipment. Tagged assets that move in one of the rooms are seen moving by the motion sensor in one room only.
  • the location engine receives a combination of radio-signal-strength information, motion-sensing information in the two rooms, and an accelerometer reading from an accelerometer in a tag, to use in its determination of which room holds the tagged asset.
  • the location engine may properly determine that a tagged asset is in the soiled room based on not only a signal-strength reading that provides an approximate location, but also by matching the motion report from an accelerometer in the tag to a motion report from a motion sensor placed in the soiled room. Therefore, the current invention provides a greatly improved room-level location determination for the tag.
  • a bay-level event sensor is defined as an electronic sensing device that can determine whether an event occurs in one bay, or its adjacent bay.
  • a bay-level event sensor may be a fixed
  • thermographic camera and the bay-level event it senses is motion in the bay, of an object that appears to be the size and shape of a human person.
  • the fixed camera can sense motion in one bay, without sensing motion in any nearby bay.
  • a bay-level event sensor may be a pressure sensor on a bed or chair.
  • the bay-level event it senses is the action of a person sitting down or rising from a bed or chair.
  • the bay-level pressure sensor can determine whether a person is sitting in a chair or bed in a precise bay, without sensing a person sitting in any adjacent bay.
  • each room-level motion sensor or bay-level event sensor detects, occurring in a specific room or bay but not an adjacent room or bay, is generally defined as a“motion event”.
  • a bay-level thermo-graphic camera may detect a human body moving in a specific bay, or a rolling equipment cart moving in a specific bay.
  • a bay-level pressure sensor may detect a person seated in a bed or chair in a specific bay, or a motion event of a person sitting down into a chair or bed, or a motion event of a person standing up from a seated position in a chair or bed.
  • a room-level passive infrared sensor may detect a motion event of a person moving in a specific room.
  • the room-level event sensor or bay- level event sensor is able to transmit a periodic radio signal known as a beacon.
  • the beacon radio signal will contain a unique identifier.
  • the beacon radio signal may be used as a location reference signal for locating the tags.
  • the beacon radio signal may contain information about the room-level motion events or bay-level motion events that are sensed in the precise room or precise bay.
  • the beacon radio signal may contain information about a recent history of motion events in the precise room or bay.
  • the bay-level accuracy may be referred to as“chair-level accuracy”.
  • An embodiment of the invention is directed to a real-time location system (RTLS) having tags, bay-level event sensors, bridges, and a location server for providing people and asset-tag locating, the includes one or more tags which transmit a report of its motion status as sensed by its accelerometer.
  • a bay-level event sensor transmits a report of motion events that occur in a bay to a location engine and one or more bridges receive reports from a tag and measure at least one characteristic of the received transmissions, including received signal strength, and forwarding those reports to a central server, and which also receives transmissions of reports from at least one bay-level event sensors, which report motion events that occur in a bay.
  • a location engine utilizes both received-signal- strength information and bay-level motion-sensing information for determining bay-level location of the at least one tag.
  • a real-time location system includes tags, room-level event sensors, bridges, and a location server for providing people and asset-tag locating that include one or more tags which transmits a report of its motion status as sensed by an accelerometer.
  • a room-level event sensor transmits a report of its sensation of motion events that occur in a bay.
  • One or more bridges receive reports from the tag and measure one or more characteristics of the received transmissions, including received signal strength, and forwarding those reports to a central server.
  • a location engine utilizes both received-signal- strength information and room-level motion-sensing information for determining room-level location of the at least one tag.
  • a real-time location system includes tags, room-level or bay-level event sensors, bridges, and a location server for providing people and asset-tag locating, and uses a room-level or bay-level event sensor, which wirelessly transmits a report of its sensation of motion events that occur in a room or bay.
  • One or more tags than listen for radio transmissions from the at least one room-level or bay-level event sensor and measure multiple characteristics of those received transmissions, including received signal strength and the report of motion events in the room-level or bay-level event sensor’s room or bay.
  • Accelerometer-sensed-motion status of the tag is compared to motion events received by the room-level or bay-level event sensors’ transmissions, and location-update messages are transmitted to a bridge for receiving reports from the tag and forwards those location-update messages to a central server.
  • a location engine utilizes both received-signal-strength information and room-level or bay-level motion-sensing information for determining room-level or bay-level location of the at least one tag.
  • a real-time location system includes tags, room-level or bay-level event sensors, bridges, and a location server for providing people and asset-tag locating and uses one or more room-level or bay- level event sensor for transmitting Bluetooth low energy (BLE) transmissions, equipped with sensor that detects motion events, and transmitting recent history of motion events sensed in the room-level or bay-level-event-sensor’s room or bay.
  • BLE Bluetooth low energy
  • a bridge receives location-update messages from at least one tag and measuring multiple characteristics of the received location-update messages, including received signal strength.
  • One or more tags than listen for BLE advertisements from the room-level or bay-level event sensors and measuring multiple characteristics of the received advertisements, including received signal strength and a series of advertisements of motion events in the room-level or bay-level- event-sensor’s room or bay.
  • An accelerometer-sensed-motion status of the tag is compared to the motion events in the room-level or bay-level event sensors’ transmissions, and location-update messages are transmitted to the bridge.
  • a location engine utilizing location-determining methods including, a first location method for calculating a first location estimate for the at least one tag, based on radio characteristics of BLE room-level or bay-level event sensor signals emitted by at least one room-level or bay-level event sensor in fixed locations and received by the tag, and transmitted to the central location server.
  • a second location method is used for calculating a second location estimate for the at least one tag, based on comparing motion events in the room-level or bay-level-event- sensors’ rooms or bays, and the coincident accelerometer-determined motion status of the at least one tag that is likely in the room or bay.
  • a third location method is used for combining the first location estimate and second location estimate to determine a location result for the tag.
  • a method for estimating bay-location for at least one asset tag used in a real-time location system comprising the steps of: calculating a first location estimate using a first location method for the at least one tag, based on radio signal-strength characteristics; calculating a second location estimate using a second location method for the at least one tag, based on matching motion events in the room- level or bay-level event-sensors’ rooms or bays, and the coincident history of changes in accelerometer-determined motion status of the at least one tag that is likely in the room or bay; and combining the first and second location estimates using a third location method for determining a location result for the at least one tag.
  • RTLS real-time location system
  • a tag for use in a real-time locating system (RTLS) and includes a wireless transceiver; a microprocessor for operating the transceiver; a battery for powering the transceiver and microprocessor; an energy harvesting device connected to an energy storage device; and a capacitor connected to the energy storage device.
  • the energy harvesting device charges the energy storage device so the capacitor can power the microprocessor and transceiver for performing limited tasks upon battery depletion.
  • a location system for estimating the room-location of a portable device in a building, and includes a one room-level or bay-level event sensor, which transmits a report of motion events that occur in a room or bay.
  • a portable device is used for listening for radio transmissions from the at least one room-level or bay-level event sensor and measuring multiple characteristics of the received transmissions, including received signal strength indication (RSSI) and a motion status of the sensor’s room-location or bay-location. Patterns of accelerometer-sensed-motion status of the portable device are compared to patterns of the motion status in the sensor’s radio transmissions, for determining room-location of the at least one portable device.
  • RSSI received signal strength indication
  • FIG. 1 is a block diagram illustrating components in an RTLS, including one or more tags, one or more bridges, one or more room-or-bay-level-event sensors, and a location engine.
  • FIG. 2 is a block diagram illustrating components used in one embodiment of the tag
  • FIG. 3 is a block diagram illustrating components used in the bridge
  • FIG. 4 is a block diagram illustrating components used in the room-level event sensor, or the bay-level event sensor.
  • FIG. 5 is a flow chart diagram illustrating the steps using the tags, bridges, room-level and bay-level event sensors and location engine to estimate tag location.
  • FIG. 6 is a block diagram illustrating components used in an alternate embodiment of the tag
  • FIG. 7 is a flow chart diagram illustrating processes used by the alternate embodiment of the tag in accordance with some embodiments of the invention.
  • Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. Detailed Description
  • embodiments of the invention described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of RTLS having tags, bridges, room-level event sensors and bay-level event sensors.
  • the non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method to perform tag functions, bridge functions, and bay-level event sensor functions.
  • the current invention proposes a room-level-accurate and bay-level- accurate RTLS.
  • Radio signals sent from the tag to the bridges provide data that the location engine may use to form a first location estimate, which likely is not precise enough for room-level or bay-level-accurate location.
  • the room-level and bay-level event sensors which may include but are not limited to motion sensors, pressure sensors, passive-infrared motion sensors,
  • thermographic cameras infrared cameras, visible-light cameras, and/or other room-level and bay-level event sensors, provide data to the location engine which empowers the location engine to estimate the tag at room-level or bay-level.
  • FIG. 1 is a block diagram illustrating components used in the RTLS in accordance with various embodiments of the invention.
  • the system 100 includes one or more fixed room-level or bay-level event sensors 101 that sense motion events, which report their sensed motion event by radio or wired transmission, including transmission to a bridge 104. Any radio transmissions from room-level or bay-level event sensors 101 that are received at the bridge 104 will be forwarded to a location engine 105.
  • One or more mobile tags 103 transmit wireless messages to one or more bridges 104. This tag transmission will contain a report of the motion status of a tag as measured by an accelerometer on the tag.
  • the motion status of a tag may be“the tag is not moving”, or“the tag is moving slowly” or“the tag is moving with a motion that resembles a person sitting down into a chair”.
  • the received signal strength and content of this tag transmission is retransmitted by the bridges, perhaps via a wireless transmission, to the location engine 105.
  • the location engine may employ trilateration or multi-lateration algorithms on the signal strength reports it receives from multiple bridges to form one estimate of the location of the tag.
  • all of the sensor information including signal strengths of tag transmissions received at the bridges, plus room- level and bay-level sensor information about motion events, plus motion-status information reported by the tag, is factored into the location algorithm at the location engine.
  • the output of the location engine is a location estimate, which is an estimate of the room-level or bay-level-location of the tag.
  • the system in FIG.1 includes a novel feature not taught in the prior art namely; a system of tags, bridges, room-level and bay-level event sensors and a location engine, which enables the location engine to combine two location estimates: one location estimate based on received signal strength, and a second location estimate based on motion status of tags and motion events sensed by room-level and bay-level event sensors; to produce a combined location estimate, used to store a updated, estimated room-level or bay-level location of the tag.
  • FIG. 2 is a block diagram illustrating system components used in the tag.
  • the tag 200 includes a transceiver 201 which transmits and receives radio frequency (RF) signals.
  • the transceiver 201 complies with the specifications of one of the set of standards Bluetooth Low Energy (BLE), or Wi-Fi, and/or IEEE 802.15.4, or similar low-power radio standards.
  • the transceiver 201 is connected to a microprocessor 203 for controlling the operation of the transceiver.
  • the transceiver is also connected to an antenna 205 for providing communication to other devices.
  • the tag further includes an accelerometer 207 connected to the microprocessor 203 for detecting motion of the tag and a battery 209 for powering electronic components in the device.
  • FIG. 3 is a block diagram illustrating components used in the bridge as seen in FIG. 1.
  • the bridge 300 includes one or more transceivers 301 that connect to a microprocessor 303 for controlling operation of the transceiver(s)
  • a Wi-Fi processor 305 also connects to the processor 303 for transmitting and receiving Wi-Fi signals.
  • An AC power supply 307 is connected to the transceiver 301, microprocessor 303 and the Wi-Fi processor 305 for powering these devices. The AC power supply 307 powers the bridge components.
  • An antenna 309 is connected to both the BLE transceiver 301 and the Wi-Fi processor 305 for transmitting and receiving tag and Wi-Fi RF signals to these devices at the appropriate frequency.
  • FIG. 4 is a block diagram illustrating components used in a room-level or bay-level event sensor that senses motion events.
  • Various embodiments of this room-level or bay-level event sensor that senses motion events are pressure sensors, passive infrared sensors, visible-light cameras, and thermographic cameras. Passive infrared sensors will detect human motion in the hospital room or bay, and the cameras may detect human and asset movement as well.
  • the room-level or bay-level sensor 400 includes a transceiver 401 for transmitting wired or radio transmissions to report the sensed data.
  • the transceiver 401 connects to a microprocessor 403 for controlling the transceiver(s).
  • a battery or alternate power supply 405 connects to the transceiver(s) 401 and the
  • the room-level or bay-level event sensor 400 that uses radio includes one or more antennas 407 for providing gain.
  • the room-level or bay-level event sensor 400 includes an event sensor 409, which detects motion events in the bay where the room-level or bay-level motion sensor is located, which may be one of a camera, infrared sensor or pressure sensor.
  • the event sensor 409 that detects motion events is connected to both the microprocessor 403 and battery 405, for detecting motion of anything in the bay.
  • the room-level or bay-level event sensor 400 typically is placed in the ceiling or high on the wall of a hospital room or hospital bay, so that it can sense motion anywhere within the room or bay.
  • the room-level or bay-level event sensor 400 can determine if there are objects moving about the room or bay, to help a location engine, to correlate motion events in rooms and bays, to motion status of tags, and match moving tags to rooms and bays that are sensed to have coincident motion.
  • the room-level or bay-level motion events can then be transmitted and/or stored in a database for determining room-level or bay-level location of one or more tags.
  • FIG. 5 is a block diagram illustrating the steps used in the location process.
  • the methods 500 as shown in FIG. 5 include starting the process 501 where a tag senses motion 503 with its accelerometer.
  • the tag transmits a radio signal 505 including its accelerometer reading.
  • One or more bridges 507 will receive the signal and forward the corresponding received-signal-strength reading and content of the transmission including the tag’s accelerometer reading to a location engine.
  • the location engine will then calculate a first location estimate based on radio signal strength indication (RSSI) data 509.
  • RSSI radio signal strength indication
  • the location engine will calculate a second location estimate based on a comparison of motion status of the tag, and the motion-event data from room-level or bay-level event sensors 511.
  • the location engine will use a third location method that combines the first location estimate and the second location estimate to estimate a room-level or bay-level location for the tag. For example, the location engine knows from the first location estimate that the tag is near bays 1, 2, or 3 but is uncertain which one specific bay the tag is in. The location engine knows from a second location estimate that considers the tag’s accelerometer reading, that the motion resembles a person in the act of sitting down, and knows from bay-level event sensors the chairs in bays 1 and 4 sensed someone taking a seat at that coincident moment, and knows from bay-level event sensors that the chairs in bays 2 and 3 did not sense anyone taking a seat, the location engine know that it is likely that the tag is in bay 1 or 4.
  • the third location method may consider the first and second location estimates to report a bay-level location reading of“Bay 1”, which was identified as likely by both the first and second location methods.
  • the method illustrated in FIG. 5 for the location engine may either centralize the functions described, or distribute these functions among the tag’s processor and a central location-server processor.
  • an attribute of the current invention is the use of tag-accelerometer motion-status and room-level-and-bay- level motion events that are sensed by room-level or bay-level event sensors, to refine the location estimate to room-level or bay-level.
  • Radio frequency signals can suffer fades, absorption and reflection, all of which decrease its signal strength.
  • the location engine that relies solely on radio frequency signal strength(s) to determine location will make location-estimate errors and erroneously place an asset or person in the wrong room or bay.
  • determining which room or bay an asset is in, and thereby determining which patient an asset is associated to is of the utmost importance. Therefore, an RTLS system may strive to estimate and report which specific room or bay an asset is located in.
  • radio signals sent by a tag or tags to the multiple bridges will suffer from a variety of polarity fades i.e. mismatches between the polarity of the transmitting antenna on the tag and the receive antenna on the bridge.
  • polarity fades work to dispel the general assumption that the RSSI of the advertisement from the tag to the bridge is directly correlated to the distance between the tag and the bridge. Therefore, this adds error to the location estimate, mis-estimating which room a clean or soiled asset is placed.
  • some of the tags will be blocked (by metal objects or other assets) from a clear line of sight to the one or more bridges, further breaking the correlation of signal strength to distance.
  • tags will have their radio energy absorbed by human bodies or bags of water, further breaking the relationship of signal strength to distance.
  • the tag may be placed in a location where it happens to suffer from a persistent multipath fade relative to a specific bridge, so that bridge will mis estimate its distance to the tag.
  • all of these radio fading effects are time- varying, as people and metal objects move through the hospital’s rooms, so using radio signal strength alone to estimate the location of an asset tag will make a stationary asset appear to move from time to time.
  • the present invention uses room-level or bay-level event sensors to help determine which room or bay a tag is located.
  • Room-level and Bay-level event sensors have a relative advantage in that they perceive the motion or pressure changes inside a room, or bay, or chair or bed within a bay, but they are oblivious to any motion in any adjacent room or bay (because those movements are in a different room, or a different bay’s bed or chair or outside the receive angle of a motion sensor or thermographic camera lens, or because the motion event occurs in a specific bay’s bed or chair).
  • the room-level event sensor in room 1 sees objects moving, sitting or standing in room 1.
  • the room-level event sensor in room 2 senses objects moving, sitting or standing in room 2. Neither room-level event sensor can sense any motion on the other room.
  • the bay-level event sensor in bay 1 sees objects moving, sitting or standing in bay 1.
  • the bay-level event sensor in bay 2 senses objects moving, sitting or standing in bay 2.
  • Neither bay-level event sensor can sense any motion on the opposite side of the curtain in the adjacent bay.
  • each room-level or bay-level event sensor in each bay sends a periodic transmission of motion status, determined from motion events.
  • a bay-level event sensor such as a camera, sensing no motion in its bay, includes that no-motion status indication in its transmission.
  • a bay-level event sensor senses motion in its bay, it transmits an indication or quantification of the motion it senses.
  • a bay-level event sensor such as a pressure sensor senses a person being seated or leaving a chair or a bed, and that motion-status event is transmitted to the location engine.
  • a room-level event sensor such as a passive infrared sensor, sensing no motion in its room, includes that no-motion status indication in its transmission.
  • That room-level event sensor senses motion in its room, it transmits an indication or quantification of the motion it senses.
  • each room or bay will have a unique“motion fingerprint” for its last few minutes of observed time.
  • A“motion fingerprint” is a record of a room’s or bay’s motion- or pressure-change events over a recent few seconds’ time.
  • the location engine can store these“motion fingerprints” for each room or bay, for use in the location estimate.
  • a location engine calculates an approximate location for a transmitting tag in the hospital room that has multiple rooms and bays
  • the location engine consults additional information to get a room-level or bay-level location fix: It will compare the patterns of the motion status of the tag as reported in the tag’s transmission, to the“motion fingerprints” of one or more rooms or bays. The location engine will match a tag to a room or bay location based on a match between the tag’s reported motion status and the room or bay’s motion fingerprint.
  • the tag is on an asset.
  • the asset may be on a cart.
  • the cart moves into one room in a hospital.
  • a room-level passive-infrared motion sensor senses the motion in bay 1.
  • the asset tag transmits a radio transmission to surrounding bridges, which feed the location engine, which uses the radio signal strengths to determine that the asset is in one of two rooms, but the location engine is not yet certain which specific room the asset has arrived in.
  • the tag’s accelerometer sends a transmission stating that the tag has stopped moving, and the movement stopped at time T.
  • Room-level motion sensors in neighboring rooms sense and report that prior to time T there was motion in room 1, but there was no motion in room 2 at time T.
  • the room-level motion sensor then senses and reports that the motion stopped in room 1 just after time T.
  • the location engine can now use the room-level event sensor information to conclude that the asset could not be in room 2 because of the lack of coincident motion in room 2, but the asset should be in room 1 because of a match between the motion status of the tag’s accelerometer and the motion event in room 1.
  • the tag is on an asset.
  • the asset may be on a cart.
  • the cart moves into one bay in a multi-bay hospital room.
  • a bay-level camera senses the motion in bay 1.
  • the asset tag transmits a radio transmission to surrounding bridges, which feed the location engine, which uses the radio signal strengths to determine that the asset is in the large room, but the location engine is not yet certain which bay the asset has arrived in.
  • the tag s accelerometer sends a transmission stating that the tag has stopped moving, and the movement stopped at time T.
  • One or more bay-level cameras in the room sense and report that prior to time T there was motion in bay 1, but there was no motion in bay 2 at time T.
  • the bay-level camera then senses and reports that the motion stopped in bay 1 just after time T.
  • the location engine can now use the bay-level event sensor information to conclude that the asset could not be in bay 2 because of the lack of coincident motion in bay 2, but the asset should be in bay 1 because of a match between the motion status of the tag’s accelerometer and the motion event in bay 1.
  • the bay-level event sensor may report (in each transmission) the current motion status in the bay as measured at the bay-level event sensor, plus the motion status at predetermined time periods (e.g. six seconds ago and 12 seconds ago).
  • one bay-level event sensor can report in a series of transmissions that there was no motion-event in a room 12 seconds ago, no motion-event six seconds ago, but there is motion currently happening in the room that is consistent with a human at walking speed.
  • One adjacent bay-level event sensor may report no motion at all.
  • a staff tag or patient tag reports that it is moving because of its accelerometer.
  • the location engine can determine that the tag is unlikely to be in the bay with the bay-level event sensor that has seen no motion at all. The location engine is therefore more accurate than a system based on signal strength alone.
  • the RTLS in the current invention uses three algorithmic methods and/or processes to estimate the room-level or bay-level location of a tag. These processes include:
  • the RTLS uses information from its location estimates from the two processes above to finalize its room-level or bay-level location estimate for the tag.
  • the radio-signal-strength estimate is determined in the location engine, using reports of received signal strength at the bridges.
  • the radio-signal-strength estimate is determined in the tag, which listens for the radio transmissions from multiple room-level and bay-level event sensors, and estimates its own location, based on the relative signal strengths of the sensors in several rooms or bays.
  • the tag functions are performed within a portable device such as a smart phone, tablet, or portable computer.
  • That portable device listens for radio transmissions from multiple room-level and bay-level event sensors, and estimates its own location, based on the relative signal strengths of the sensors in several rooms or bays, the motion status of the sensors, and the motion status of its own accelerometer. That room- level or bay-level location may be reported to the location engine by a radio transmission from the smart device to the bridge, which relays the smart-device location to the location engine.
  • each sensor may include in its transmission another piece of data, viz. its room type.
  • the sensor s transmission of its room-type helps the portable device to determine whether it is entering a room where room-level location is important (such as a patient room), vis-a-vis entering a hallway.
  • typical“room types” in a hospital setting may include but are not limited to patient room, hallway, equipment storage room, and elevator lobby.
  • the portable device may optionally consider the room-type in its decision as to whether to report a room-level location.
  • Each sensor may include in its transmission another piece of data: the floor on which it has been installed.
  • a portable device knows that a movement from a patient room on one floor directly to a patient room on an adjacent floor is not likely (and a radio algorithm that reports such a change may be mistaken because of a spurious radio signal from another floor). Therefore, the portable device will be told to reject an apparent floor-hop from a patient room to another floor, because that move is unlikely. But a transition from a hallway on one floor to a patient room on the same floor is very possible, so the portable device should accept that reported location change when it is confirmed by the signal strength and motion-event algorithm.
  • the portable device in the current invention uses sensor-reported motion information, sensor-reported floor information, and radio signal strength, to estimate the location of a portable device. The location estimate will be more accurate over the portable device using radio signal strength alone.
  • each bed and chair is permanently installed in a specific bay, and is administratively assigned to a bay.
  • the bay-level location of the patient is derived from the bay-level location of the chair.
  • each bed and chair is movable and may be located in a different bay from hour to hour or day to day.
  • the beds and chairs will then be tagged with an active tag.
  • the bay-level location of each bed or bay is established through the method shown in Figure 5 as each tagged bed or chair is moved into a bay. Subsequently, when a patient sits or lies in chair or bed, the location of the patient is derived from the bay-level location of the chair or bed.
  • FIG. 6 is a block diagram illustrating system components used in the tag as seen in FIG. 1, in some alternate embodiments of the invention.
  • the tag 600 includes a low energy BLE transceiver 601 that works to transmit and receive Bluetooth RF signals.
  • the BLE transceiver 601 is connected to a microprocessor 603 for controlling the operation of the transceiver.
  • the BLE transceiver is also connected to an antenna 605 for providing communication to other devices.
  • the tag further includes an accelerometer 607 connected to microprocessor 603 for detecting motion of the tag.
  • the tag 600 further includes a unique power management system where a battery 611 is connected to the microprocessor 603 and accelerometer 607 where the battery 611 works to power these devices in one operating mode.
  • an energy harvesting circuit such as a photocell using light energy, or other energy harvester 613, can be used to power the device for specific tasks. More specifically, the photocell or other energy harvester 613 connects to an energy storage device 615 to charge the storage device 615 for use in tasks requiring short bursts of energy to power the tag 600. The energy storage 615 then charges a capacitor 617, connected to the BLE transceiver 601 and microprocessor 603, for energizing these devices for such limited periods of time e.g. when the tag is misplaced and has a dead battery.
  • the tag 600 includes a novel feature not taught in the prior art namely: the tag 600 is rarely spent nor will it ever be fully discharged since it will not die due to battery depletion.
  • the photocell or other energy harvester 613 and energy storage 615 are used to provide energy for operating the tag for limited periods.
  • the photocell charges the energy storage device 615 for operating the tag 600 for limited tasks including running an initialization process, executing software in the tag, transmitting a message that can be used for tag location
  • FIG. 7. is a flow chart outlining the process 700 by which the tag 600 optimally uses both power sources.
  • the process starts 701 with the tag using the battery power 703.
  • the tag will use the battery power to operate in Operating Model, transmitting frequently enough to achieve low-latency and highly accurate locations 705. Energy harvesting may occur when the tag is in
  • the present invention describes a new wireless technology available for RTLS systems in healthcare that makes the RTLS more reliable and a long- lived survivability for use in hospitals.
  • Hospitals may survive a period of battery depletion which causes tags to become un-locatable and un-serviceable.
  • tags can transmit a location signal at some periodic interval, e.g. at least once per day. This allows the system manager to locate the dead-battery tag(s), service it, and return it to normal operating mode, without having to search an entire hospital for a non-reporting, dead-battery tag.
  • RTLS systems with active tags in common use usually employ a process to monitor the battery status of the tag, and attempt to alert or warn system managers when a tag is reaching a low-battery status and needs to be serviced.
  • these processes are often unsuccessful in notifying the system’s manager in time, or the system’s manager is unable to replace the battery or tag before the battery fails.
  • Once a battery fails on a tag or badge, and the asset or person moves to a new location, their location changes are invisible to the RTLS system. It becomes very difficult to find a dead-battery tag for several reasons: the tag can be carried anywhere within a large building like a hospital, and a dead tag looks exactly like a live tag, so a visual inspection is no help.
  • Some non-RTLS sensory systems are beginning to be introduced into the market which use energy harvesting to power the sensors. These devices lack a battery. Their advantage is that they do not have a battery that dies and renders the sensor useless.
  • energy-harvesting technology alone is not practical for powering RTLS tags for their entire useful life. In practice, either the energy harvesting circuitry makes the tag so large as to be impractical for tagging small assets, or the energy harvesting circuitry does not harvest enough energy to power a tag that can be located accurately at low latency.
  • the active tags feature both a battery, and energy-harvesting circuitry, and operate in two power modes at various times, switching between the two modes.
  • the tag uses a first operating mode which uses the battery to transmit frequent locating signals, for low-latency and high-accuracy locating.
  • the second operating mode uses the energy-harvested power to transmit less-frequent locating signals, so that the tag can continue to be located when the battery is dead or at an inoperative level.
  • “Adequate power” for the first operating mode is defined as battery power sufficient to energize the tag’s microprocessor and radio transceiver to successfully format, generate and send a radio transmission that the RTLS can use to locate the tag.

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Abstract

A real-time location system (RTLS) includes tags, bridges, room-level and bay-level event sensors and a location engine. To determine which room or bay a tag is in, room-level and bay-level event sensors sense motion events in the room or bay, transmit the motion event reports to a location engine, and/or tags. Tags contain an accelerometer, to sense motion of the tags. A series of location-engine steps estimates the room-level or bay-level-location of the tags based on a combination of received signal-strength analysis, and a comparison of tag-motion status to the perceived motion events in a room or bay. The analysis of tag- motion status and motion-in-room and motion-in-bay events produces a better estimate of room-level or bay-level location of the tag than a received-signal- strength estimate can produce alone.

Description

A REAL-TIME LOCATION SYSTEM (RTLS) THAT USES A COMBINATION OF EVENT SENSORS AND RSSI MEASUREMENTS TO DETERMINE ROOM-AND-B A Y -LOCATION OF TAGS
Field of the Invention
[0001] The present invention relates generally to a real-time location system (RTLS) having active tags, bridges, and room-level, bed-level, or-bay-level event sensors, that pass sufficient sensor data to a location engine in a central server, to locate tags at room-level, bed-level, and bay-level inside a building such as a hospital.
Background of the Invention
[0002] RTLS systems estimate locations for moving tags or moving personnel badges within a floor plan of interior rooms, in buildings such as hospitals. Many RTLS systems based on radio-frequency signals such as Wi-Fi or Bluetooth Low Energy (BLE), are designed to have moving tags that transmit a radio signal, within a field of receiving devices called bridges, gateways, sensors, or Access Points. A network of bridges will measure and use received signal strength of transmissions from a tag, as a proxy for estimating the distance between the tag and each bridge, and then use multi-lateration algorithms to estimate the locations of tags. Those approaches with tags that transmit are standard in the industry and provide location estimates that are acceptable for may use cases in industrial and manufacturing environments. They may even be accurate enough to locate tagged assets and tagged people with accuracy within 1 -meter or less. But the approaches common in the industry fail to provide an efficient location system for determining the precise location of a tag at room-level, bay-level or bed-level, especially in large, open patient-care areas in hospitals, or in a hospital room with two patient beds. [0003] Hospitals typically have several, large, patient-care rooms where may patients can be treated simultaneously, such as an ED receiving room, a prepare- for-surgery room, a recovery-from-surgery room, or an infusion room. These large rooms are designed with a set of small bays, where each bay is defined as a treatment area for one patient. Each bay usually has enough floor space to hold one bed, and/or one chair, for a patient to lie in or sit in. The bays may be separated by a curtain. The curtain may be suspended from a track in the ceiling of the bay, which allows a curtain to be drawn or retracted to provide a private space for the patient’s care. The bays may alternatively be divided by a structural half- wall or other privacy structure.
[0004] Hospitals also have patient rooms for inpatients which are shared by two or more patients in two or more beds. The beds in these shared multi-patient rooms are typically separated by a curtain.
[0005] RTLS systems in hospitals in common use may be able to determine or estimate the location of tagged assets, patients and staff members with 1 -meter accuracy, but RTLS systems in common use fail to determine reliably which room or bay the tag resides in. As one example, the common RTLS system struggles to determine which side of a wall the tag resides on, because the common RTLS system uses only radio signals for location information, and the radio signals travel through the wall. As a second example, the common RTLS system struggles to determine which side of a curtain a tag resides on. A better location system is required that can reliably determine which side of a wall or curtain a tag resides on, so the hospital can determine which room or bay a patient is seated in, and which caregivers are in the room or bay with the patient, and determine which assets are in the room or bay with the patient. Similarly, RTLS systems in common use fail to determine which bed a tag resides on or near, in a multi patient room.
[0006] To illustrate the accuracy problem, imagine a hospital that puts clean equipment into one room, and soiled equipment in an adjacent room, where the two rooms are separated only by a wall. Tagged assets may be placed on shelves along that shared wall, just 20 centimeters apart from each other, separated by a wall. An RTLS-system lookup for clean equipment needs to report all assets in the clean-equipment room, and none of the equipment in the soiled-equipment room. An RTLS system that uses radio-signals may be able to estimate a location for a tagged asset within 1 -meter accuracy, but still struggle to answer the question of precisely which side of the wall the tagged asset is on because the tags are only 20 centimeters apart. Some RTLS systems have used infrared light or ultrasound signals to determine the precise room-level location of each tagged asset, but these systems require significant design, engineering, tuning, and cost.
[0007] To further illustrate the accuracy problem, imagine a hospital patient-care area that is a large room, hosting many patients, divided into bays. Patients may sit in beds or lie or chairs just 1 meter apart from each other, separated by a curtain. For some hospital use cases, an RTLS system must be accurate enough to determine which bed, chair or bay a patient is located in, and also determine which pieces of medical equipment are in the same bay with that patient, and also determine which staff members are in the same bay with that patient. An RTLS system that uses radio-signals may be able to estimate a location for a patient, asset or staff member within 1 -meter accuracy, but still struggle to answer the question of precisely which side of the curtain the tagged asset, patient or staff member is on because the patients are only 1 meter apart. RTLS systems have used infrared light or ultrasound signals to build“virtual walls” where the curtains separate the bays, but these systems require significant design, engineering, tuning, and cost.
[0008] The current invention proposes a novel use of a room-level and bay-level event sensor(s). A room-level event sensor is defined as an electronic sensing device that can determine whether movement occurs in the room where it is placed. One example of a room-level event sensor is a passive-infrared motion sensor. In one embodiment of the invention, two room-level motion sensors are placed in two rooms on opposite sides of a shared wall. For this illustration, we can assume that one room holds clean equipment and the other room holds soiled equipment. Tagged assets that move in one of the rooms are seen moving by the motion sensor in one room only. The location engine receives a combination of radio-signal-strength information, motion-sensing information in the two rooms, and an accelerometer reading from an accelerometer in a tag, to use in its determination of which room holds the tagged asset. The location engine may properly determine that a tagged asset is in the soiled room based on not only a signal-strength reading that provides an approximate location, but also by matching the motion report from an accelerometer in the tag to a motion report from a motion sensor placed in the soiled room. Therefore, the current invention provides a greatly improved room-level location determination for the tag.
[0009] A bay-level event sensor is defined as an electronic sensing device that can determine whether an event occurs in one bay, or its adjacent bay. In one embodiment of the invention, a bay-level event sensor may be a fixed
thermographic camera, and the bay-level event it senses is motion in the bay, of an object that appears to be the size and shape of a human person. The fixed camera can sense motion in one bay, without sensing motion in any nearby bay.
In a similar embodiment of the invention, the camera will sense multiple bays, and through analysis of one or more camera images, determine which bay an event is occurring in. In another embodiment, a bay-level event sensor may be a pressure sensor on a bed or chair. The bay-level event it senses is the action of a person sitting down or rising from a bed or chair. The bay-level pressure sensor can determine whether a person is sitting in a chair or bed in a precise bay, without sensing a person sitting in any adjacent bay.
[0010] The event that each room-level motion sensor or bay-level event sensor detects, occurring in a specific room or bay but not an adjacent room or bay, is generally defined as a“motion event”. A bay-level thermo-graphic camera may detect a human body moving in a specific bay, or a rolling equipment cart moving in a specific bay. A bay-level pressure sensor may detect a person seated in a bed or chair in a specific bay, or a motion event of a person sitting down into a chair or bed, or a motion event of a person standing up from a seated position in a chair or bed. A room-level passive infrared sensor may detect a motion event of a person moving in a specific room.
[0011] In one embodiment of the invention, the room-level event sensor or bay- level event sensor is able to transmit a periodic radio signal known as a beacon. The beacon radio signal will contain a unique identifier. The beacon radio signal may be used as a location reference signal for locating the tags. The beacon radio signal may contain information about the room-level motion events or bay-level motion events that are sensed in the precise room or precise bay. The beacon radio signal may contain information about a recent history of motion events in the precise room or bay.
[0012] Estimating the location of a tag with a precision of determining which room a tag resides in is often named“room-level accuracy”.
[0013] Estimating the location of a tag with a precision of determining which bay a tag resides in is often named“bay-level accuracy”. If there is one bed in that one bay, then the bay-level accuracy may be referred to as“bed-level accuracy”.
If there is one chair in that one bay, then the bay-level accuracy may be referred to as“chair-level accuracy”.
Summary of the Invention
[0014] An embodiment of the invention is directed to a real-time location system (RTLS) having tags, bay-level event sensors, bridges, and a location server for providing people and asset-tag locating, the includes one or more tags which transmit a report of its motion status as sensed by its accelerometer. A bay-level event sensor, transmits a report of motion events that occur in a bay to a location engine and one or more bridges receive reports from a tag and measure at least one characteristic of the received transmissions, including received signal strength, and forwarding those reports to a central server, and which also receives transmissions of reports from at least one bay-level event sensors, which report motion events that occur in a bay. A location engine utilizes both received-signal- strength information and bay-level motion-sensing information for determining bay-level location of the at least one tag.
[0015] In another embodiment, a real-time location system (RTLS) includes tags, room-level event sensors, bridges, and a location server for providing people and asset-tag locating that include one or more tags which transmits a report of its motion status as sensed by an accelerometer. A room-level event sensor transmits a report of its sensation of motion events that occur in a bay. One or more bridges receive reports from the tag and measure one or more characteristics of the received transmissions, including received signal strength, and forwarding those reports to a central server. A location engine utilizes both received-signal- strength information and room-level motion-sensing information for determining room-level location of the at least one tag.
[0016] In still another embodiment, a real-time location system (RTLS) includes tags, room-level or bay-level event sensors, bridges, and a location server for providing people and asset-tag locating, and uses a room-level or bay-level event sensor, which wirelessly transmits a report of its sensation of motion events that occur in a room or bay. One or more tags than listen for radio transmissions from the at least one room-level or bay-level event sensor and measure multiple characteristics of those received transmissions, including received signal strength and the report of motion events in the room-level or bay-level event sensor’s room or bay. Accelerometer-sensed-motion status of the tag is compared to motion events received by the room-level or bay-level event sensors’ transmissions, and location-update messages are transmitted to a bridge for receiving reports from the tag and forwards those location-update messages to a central server. A location engine utilizes both received-signal-strength information and room-level or bay-level motion-sensing information for determining room-level or bay-level location of the at least one tag.
[0017] In yet another embodiment, a real-time location system (RTLS) includes tags, room-level or bay-level event sensors, bridges, and a location server for providing people and asset-tag locating and uses one or more room-level or bay- level event sensor for transmitting Bluetooth low energy (BLE) transmissions, equipped with sensor that detects motion events, and transmitting recent history of motion events sensed in the room-level or bay-level-event-sensor’s room or bay.
A bridge receives location-update messages from at least one tag and measuring multiple characteristics of the received location-update messages, including received signal strength. One or more tags than listen for BLE advertisements from the room-level or bay-level event sensors and measuring multiple characteristics of the received advertisements, including received signal strength and a series of advertisements of motion events in the room-level or bay-level- event-sensor’s room or bay. An accelerometer-sensed-motion status of the tag is compared to the motion events in the room-level or bay-level event sensors’ transmissions, and location-update messages are transmitted to the bridge. Then a location engine utilizing location-determining methods including, a first location method for calculating a first location estimate for the at least one tag, based on radio characteristics of BLE room-level or bay-level event sensor signals emitted by at least one room-level or bay-level event sensor in fixed locations and received by the tag, and transmitted to the central location server. A second location method is used for calculating a second location estimate for the at least one tag, based on comparing motion events in the room-level or bay-level-event- sensors’ rooms or bays, and the coincident accelerometer-determined motion status of the at least one tag that is likely in the room or bay. Finally, a third location method is used for combining the first location estimate and second location estimate to determine a location result for the tag. [0018] In another embedment of the invention, a method is provided for estimating bay-location for at least one asset tag used in a real-time location system (RTLS), comprising the steps of: calculating a first location estimate using a first location method for the at least one tag, based on radio signal-strength characteristics; calculating a second location estimate using a second location method for the at least one tag, based on matching motion events in the room- level or bay-level event-sensors’ rooms or bays, and the coincident history of changes in accelerometer-determined motion status of the at least one tag that is likely in the room or bay; and combining the first and second location estimates using a third location method for determining a location result for the at least one tag.
[0019] In still yet another embodiment of the invention, a tag is provided for use in a real-time locating system (RTLS) and includes a wireless transceiver; a microprocessor for operating the transceiver; a battery for powering the transceiver and microprocessor; an energy harvesting device connected to an energy storage device; and a capacitor connected to the energy storage device. The energy harvesting device charges the energy storage device so the capacitor can power the microprocessor and transceiver for performing limited tasks upon battery depletion.
[0020] Finally, in another embodiment of the invention, a location system is provided for estimating the room-location of a portable device in a building, and includes a one room-level or bay-level event sensor, which transmits a report of motion events that occur in a room or bay. A portable device is used for listening for radio transmissions from the at least one room-level or bay-level event sensor and measuring multiple characteristics of the received transmissions, including received signal strength indication (RSSI) and a motion status of the sensor’s room-location or bay-location. Patterns of accelerometer-sensed-motion status of the portable device are compared to patterns of the motion status in the sensor’s radio transmissions, for determining room-location of the at least one portable device.
Brief Description of the Figures
[0021] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
[0022] FIG. 1 is a block diagram illustrating components in an RTLS, including one or more tags, one or more bridges, one or more room-or-bay-level-event sensors, and a location engine.
[0023] FIG. 2 is a block diagram illustrating components used in one embodiment of the tag;
[0024] FIG. 3 is a block diagram illustrating components used in the bridge;
[0025] FIG. 4 is a block diagram illustrating components used in the room-level event sensor, or the bay-level event sensor; and
[0026] FIG. 5 is a flow chart diagram illustrating the steps using the tags, bridges, room-level and bay-level event sensors and location engine to estimate tag location.
[0027] FIG. 6 is a block diagram illustrating components used in an alternate embodiment of the tag
[0028] FIG. 7 is a flow chart diagram illustrating processes used by the alternate embodiment of the tag in accordance with some embodiments of the invention [0029] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. Detailed Description
[0030] Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to an RTLS having active tags, room-level and bay-level event sensors, and bridges that pass location updates to a location engine in a central server. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
[0031] In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by“comprises ...a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.
[0032] It will be appreciated that embodiments of the invention described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of RTLS having tags, bridges, room-level event sensors and bay-level event sensors. The non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method to perform tag functions, bridge functions, and bay-level event sensor functions. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. Thus, methods and means for these functions have been described herein. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.
[0033] The current invention proposes a room-level-accurate and bay-level- accurate RTLS. Radio signals sent from the tag to the bridges provide data that the location engine may use to form a first location estimate, which likely is not precise enough for room-level or bay-level-accurate location. But the addition of the room-level and bay-level event sensors, which may include but are not limited to motion sensors, pressure sensors, passive-infrared motion sensors,
thermographic cameras, infrared cameras, visible-light cameras, and/or other room-level and bay-level event sensors, provide data to the location engine which empowers the location engine to estimate the tag at room-level or bay-level.
[0034] FIG. 1 is a block diagram illustrating components used in the RTLS in accordance with various embodiments of the invention. The system 100 includes one or more fixed room-level or bay-level event sensors 101 that sense motion events, which report their sensed motion event by radio or wired transmission, including transmission to a bridge 104. Any radio transmissions from room-level or bay-level event sensors 101 that are received at the bridge 104 will be forwarded to a location engine 105. One or more mobile tags 103 transmit wireless messages to one or more bridges 104. This tag transmission will contain a report of the motion status of a tag as measured by an accelerometer on the tag. As examples, the motion status of a tag may be“the tag is not moving”, or“the tag is moving slowly” or“the tag is moving with a motion that resembles a person sitting down into a chair”. The received signal strength and content of this tag transmission is retransmitted by the bridges, perhaps via a wireless transmission, to the location engine 105. As is already typical in the industry, the location engine may employ trilateration or multi-lateration algorithms on the signal strength reports it receives from multiple bridges to form one estimate of the location of the tag. With the current invention, all of the sensor information, including signal strengths of tag transmissions received at the bridges, plus room- level and bay-level sensor information about motion events, plus motion-status information reported by the tag, is factored into the location algorithm at the location engine. The output of the location engine is a location estimate, which is an estimate of the room-level or bay-level-location of the tag.
[0035] Thus, the system in FIG.1 includes a novel feature not taught in the prior art namely; a system of tags, bridges, room-level and bay-level event sensors and a location engine, which enables the location engine to combine two location estimates: one location estimate based on received signal strength, and a second location estimate based on motion status of tags and motion events sensed by room-level and bay-level event sensors; to produce a combined location estimate, used to store a updated, estimated room-level or bay-level location of the tag.
[0036] FIG. 2 is a block diagram illustrating system components used in the tag. The tag 200 includes a transceiver 201 which transmits and receives radio frequency (RF) signals. The transceiver 201 complies with the specifications of one of the set of standards Bluetooth Low Energy (BLE), or Wi-Fi, and/or IEEE 802.15.4, or similar low-power radio standards. The transceiver 201 is connected to a microprocessor 203 for controlling the operation of the transceiver. The transceiver is also connected to an antenna 205 for providing communication to other devices. The tag further includes an accelerometer 207 connected to the microprocessor 203 for detecting motion of the tag and a battery 209 for powering electronic components in the device.
[0037] FIG. 3 is a block diagram illustrating components used in the bridge as seen in FIG. 1. The bridge 300 includes one or more transceivers 301 that connect to a microprocessor 303 for controlling operation of the transceiver(s)
301. A Wi-Fi processor 305 also connects to the processor 303 for transmitting and receiving Wi-Fi signals. An AC power supply 307 is connected to the transceiver 301, microprocessor 303 and the Wi-Fi processor 305 for powering these devices. The AC power supply 307 powers the bridge components. An antenna 309 is connected to both the BLE transceiver 301 and the Wi-Fi processor 305 for transmitting and receiving tag and Wi-Fi RF signals to these devices at the appropriate frequency.
[0038] FIG. 4 is a block diagram illustrating components used in a room-level or bay-level event sensor that senses motion events. Various embodiments of this room-level or bay-level event sensor that senses motion events are pressure sensors, passive infrared sensors, visible-light cameras, and thermographic cameras. Passive infrared sensors will detect human motion in the hospital room or bay, and the cameras may detect human and asset movement as well. The room-level or bay-level sensor 400 includes a transceiver 401 for transmitting wired or radio transmissions to report the sensed data. The transceiver 401 connects to a microprocessor 403 for controlling the transceiver(s). A battery or alternate power supply 405 connects to the transceiver(s) 401 and the
microprocessor 403 for powering these devices. The room-level or bay-level event sensor 400 that uses radio includes one or more antennas 407 for providing gain.
[0039] The room-level or bay-level event sensor 400 includes an event sensor 409, which detects motion events in the bay where the room-level or bay-level motion sensor is located, which may be one of a camera, infrared sensor or pressure sensor. The event sensor 409 that detects motion events is connected to both the microprocessor 403 and battery 405, for detecting motion of anything in the bay. The room-level or bay-level event sensor 400 typically is placed in the ceiling or high on the wall of a hospital room or hospital bay, so that it can sense motion anywhere within the room or bay. Thus, the room-level or bay-level event sensor 400 can determine if there are objects moving about the room or bay, to help a location engine, to correlate motion events in rooms and bays, to motion status of tags, and match moving tags to rooms and bays that are sensed to have coincident motion. The room-level or bay-level motion events can then be transmitted and/or stored in a database for determining room-level or bay-level location of one or more tags.
[0040] FIG. 5 is a block diagram illustrating the steps used in the location process. The methods 500 as shown in FIG. 5 include starting the process 501 where a tag senses motion 503 with its accelerometer. The tag transmits a radio signal 505 including its accelerometer reading. One or more bridges 507 will receive the signal and forward the corresponding received-signal-strength reading and content of the transmission including the tag’s accelerometer reading to a location engine. The location engine will then calculate a first location estimate based on radio signal strength indication (RSSI) data 509. Next, the location engine will calculate a second location estimate based on a comparison of motion status of the tag, and the motion-event data from room-level or bay-level event sensors 511. Then, the location engine will use a third location method that combines the first location estimate and the second location estimate to estimate a room-level or bay-level location for the tag. For example, the location engine knows from the first location estimate that the tag is near bays 1, 2, or 3 but is uncertain which one specific bay the tag is in. The location engine knows from a second location estimate that considers the tag’s accelerometer reading, that the motion resembles a person in the act of sitting down, and knows from bay-level event sensors the chairs in bays 1 and 4 sensed someone taking a seat at that coincident moment, and knows from bay-level event sensors that the chairs in bays 2 and 3 did not sense anyone taking a seat, the location engine know that it is likely that the tag is in bay 1 or 4. The third location method may consider the first and second location estimates to report a bay-level location reading of“Bay 1”, which was identified as likely by both the first and second location methods. The method illustrated in FIG. 5 for the location engine may either centralize the functions described, or distribute these functions among the tag’s processor and a central location-server processor.
[0041] Those skilled in the art will recognize that an attribute of the current invention is the use of tag-accelerometer motion-status and room-level-and-bay- level motion events that are sensed by room-level or bay-level event sensors, to refine the location estimate to room-level or bay-level. Radio frequency signals can suffer fades, absorption and reflection, all of which decrease its signal strength. As a result, the location engine that relies solely on radio frequency signal strength(s) to determine location will make location-estimate errors and erroneously place an asset or person in the wrong room or bay. For some RTLS applications and use cases, determining which room or bay an asset is in, and thereby determining which patient an asset is associated to, is of the utmost importance. Therefore, an RTLS system may strive to estimate and report which specific room or bay an asset is located in.
[0042] Typically, in a RTLS, radio signals sent by a tag or tags to the multiple bridges will suffer from a variety of polarity fades i.e. mismatches between the polarity of the transmitting antenna on the tag and the receive antenna on the bridge. These polarity fades work to dispel the general assumption that the RSSI of the advertisement from the tag to the bridge is directly correlated to the distance between the tag and the bridge. Therefore, this adds error to the location estimate, mis-estimating which room a clean or soiled asset is placed. In addition, some of the tags will be blocked (by metal objects or other assets) from a clear line of sight to the one or more bridges, further breaking the correlation of signal strength to distance. Some of the tags will have their radio energy absorbed by human bodies or bags of water, further breaking the relationship of signal strength to distance. The tag may be placed in a location where it happens to suffer from a persistent multipath fade relative to a specific bridge, so that bridge will mis estimate its distance to the tag. Finally, all of these radio fading effects are time- varying, as people and metal objects move through the hospital’s rooms, so using radio signal strength alone to estimate the location of an asset tag will make a stationary asset appear to move from time to time.
[0043] All of these radio-fading effects make it very difficult to estimate which room or bay each of the assets are placed in, producing erred room-or-bay- location estimates. Bay 1 may be only 1 meter from the adjacent Bay 2. If the RTLS location algorithm has 1 -meter accuracy 90% of the time, then the algorithm will fail to estimate the correct bay-level location of all assets and people 10% of the time. Hence, those skilled in the art will reach the conclusion that radio signal strength alone is insufficient for determining which bay an asset is placed in greater than 90% of the time, even if it is 1 -meter accurate or half meter accurate. Signal strength measurements are degraded by too many radio fading effects.
[0044] Hence, the present invention uses room-level or bay-level event sensors to help determine which room or bay a tag is located. Room-level and Bay-level event sensors have a relative advantage in that they perceive the motion or pressure changes inside a room, or bay, or chair or bed within a bay, but they are oblivious to any motion in any adjacent room or bay (because those movements are in a different room, or a different bay’s bed or chair or outside the receive angle of a motion sensor or thermographic camera lens, or because the motion event occurs in a specific bay’s bed or chair). In using the system and methods of present invention, the room-level event sensor in room 1 sees objects moving, sitting or standing in room 1. The room-level event sensor in room 2 senses objects moving, sitting or standing in room 2. Neither room-level event sensor can sense any motion on the other room. In using the system and methods of present invention, the bay-level event sensor in bay 1 sees objects moving, sitting or standing in bay 1. The bay-level event sensor in bay 2 senses objects moving, sitting or standing in bay 2. Neither bay-level event sensor can sense any motion on the opposite side of the curtain in the adjacent bay.
[0045] With the present invention, each room-level or bay-level event sensor in each bay sends a periodic transmission of motion status, determined from motion events. In one embodiment of the present invention, a bay-level event sensor such as a camera, sensing no motion in its bay, includes that no-motion status indication in its transmission. When that bay-level event sensor senses motion in its bay, it transmits an indication or quantification of the motion it senses. In an alternate embodiment of the present invention, a bay-level event sensor such as a pressure sensor senses a person being seated or leaving a chair or a bed, and that motion-status event is transmitted to the location engine. In yet another embodiment of the present invention, a room-level event sensor such as a passive infrared sensor, sensing no motion in its room, includes that no-motion status indication in its transmission. When that room-level event sensor senses motion in its room, it transmits an indication or quantification of the motion it senses.
[0046] Since motion-status event changes in one room or bay are likely to be non coincident with motion-status event changes in an adjacent room or bay, each room or bay will have a unique“motion fingerprint” for its last few minutes of observed time. A“motion fingerprint” is a record of a room’s or bay’s motion- or pressure-change events over a recent few seconds’ time. The location engine can store these“motion fingerprints” for each room or bay, for use in the location estimate. When a location engine calculates an approximate location for a transmitting tag in the hospital room that has multiple rooms and bays, the location engine consults additional information to get a room-level or bay-level location fix: It will compare the patterns of the motion status of the tag as reported in the tag’s transmission, to the“motion fingerprints” of one or more rooms or bays. The location engine will match a tag to a room or bay location based on a match between the tag’s reported motion status and the room or bay’s motion fingerprint.
[0047] In one embodiment of the present innovation, the tag is on an asset. The asset may be on a cart. The cart moves into one room in a hospital. A room-level passive-infrared motion sensor senses the motion in bay 1. The asset tag transmits a radio transmission to surrounding bridges, which feed the location engine, which uses the radio signal strengths to determine that the asset is in one of two rooms, but the location engine is not yet certain which specific room the asset has arrived in. The tag’s accelerometer sends a transmission stating that the tag has stopped moving, and the movement stopped at time T. Room-level motion sensors in neighboring rooms sense and report that prior to time T there was motion in room 1, but there was no motion in room 2 at time T. The room-level motion sensor then senses and reports that the motion stopped in room 1 just after time T. The location engine can now use the room-level event sensor information to conclude that the asset could not be in room 2 because of the lack of coincident motion in room 2, but the asset should be in room 1 because of a match between the motion status of the tag’s accelerometer and the motion event in room 1.
[0048] In another embodiment of the present innovation, the tag is on an asset. The asset may be on a cart. The cart moves into one bay in a multi-bay hospital room. A bay-level camera senses the motion in bay 1. The asset tag transmits a radio transmission to surrounding bridges, which feed the location engine, which uses the radio signal strengths to determine that the asset is in the large room, but the location engine is not yet certain which bay the asset has arrived in. The tag’s accelerometer sends a transmission stating that the tag has stopped moving, and the movement stopped at time T. One or more bay-level cameras in the room sense and report that prior to time T there was motion in bay 1, but there was no motion in bay 2 at time T. The bay-level camera then senses and reports that the motion stopped in bay 1 just after time T. The location engine can now use the bay-level event sensor information to conclude that the asset could not be in bay 2 because of the lack of coincident motion in bay 2, but the asset should be in bay 1 because of a match between the motion status of the tag’s accelerometer and the motion event in bay 1.
[0049] As another illustration of the unique benefit of the current invention, consider the challenge of locating a tag-wearing staff member, or patient. Radio signals are absorbed by the human body. The location engine that uses only radio signal-strength will struggle to determine where a staff member or patient is actually located, and may report an adjacent (incorrect) bay as the location of the staff tag. In one embodiment of the current invention, the bay-level event sensor may report (in each transmission) the current motion status in the bay as measured at the bay-level event sensor, plus the motion status at predetermined time periods (e.g. six seconds ago and 12 seconds ago). As an example, one bay-level event sensor can report in a series of transmissions that there was no motion-event in a room 12 seconds ago, no motion-event six seconds ago, but there is motion currently happening in the room that is consistent with a human at walking speed. One adjacent bay-level event sensor may report no motion at all. A staff tag or patient tag reports that it is moving because of its accelerometer. The location engine can determine that the tag is unlikely to be in the bay with the bay-level event sensor that has seen no motion at all. The location engine is therefore more accurate than a system based on signal strength alone.
[0050] Hence, the RTLS in the current invention uses three algorithmic methods and/or processes to estimate the room-level or bay-level location of a tag. These processes include:
1) Use of radio-signal strength and trilateration to estimate a location of a tag, which may not be a room-level or bay-level-accurate estimate.
2) Matching of motion events reported by room-level or bay-level event sensors and motion status reported by tags, to estimate the room-level or bay-level location of a tag. 3) Finally, the RTLS uses information from its location estimates from the two processes above to finalize its room-level or bay-level location estimate for the tag.
[0051] In one embodiment of the invention, the radio-signal-strength estimate is determined in the location engine, using reports of received signal strength at the bridges. In an alternate embodiment of the invention, the radio-signal-strength estimate is determined in the tag, which listens for the radio transmissions from multiple room-level and bay-level event sensors, and estimates its own location, based on the relative signal strengths of the sensors in several rooms or bays.
[0052] In yet another embodiment of the invention, the tag functions are performed within a portable device such as a smart phone, tablet, or portable computer. That portable device listens for radio transmissions from multiple room-level and bay-level event sensors, and estimates its own location, based on the relative signal strengths of the sensors in several rooms or bays, the motion status of the sensors, and the motion status of its own accelerometer. That room- level or bay-level location may be reported to the location engine by a radio transmission from the smart device to the bridge, which relays the smart-device location to the location engine.
[0053] In one embodiment of the invention, each sensor may include in its transmission another piece of data, viz. its room type. The sensor’s transmission of its room-type helps the portable device to determine whether it is entering a room where room-level location is important (such as a patient room), vis-a-vis entering a hallway. For example, typical“room types” in a hospital setting may include but are not limited to patient room, hallway, equipment storage room, and elevator lobby. The portable device may optionally consider the room-type in its decision as to whether to report a room-level location.
[0054] Each sensor may include in its transmission another piece of data: the floor on which it has been installed. A portable device knows that a movement from a patient room on one floor directly to a patient room on an adjacent floor is not likely (and a radio algorithm that reports such a change may be mistaken because of a spurious radio signal from another floor). Therefore, the portable device will be told to reject an apparent floor-hop from a patient room to another floor, because that move is unlikely. But a transition from a hallway on one floor to a patient room on the same floor is very possible, so the portable device should accept that reported location change when it is confirmed by the signal strength and motion-event algorithm. Hence, the portable device in the current invention uses sensor-reported motion information, sensor-reported floor information, and radio signal strength, to estimate the location of a portable device. The location estimate will be more accurate over the portable device using radio signal strength alone.
[0055] In another embodiment of the invention, each bed and chair is permanently installed in a specific bay, and is administratively assigned to a bay. When a patient sits in a chair, and the location of the chair is administratively assigned to a bay, the bay-level location of the patient is derived from the bay-level location of the chair. In an alternate embodiment of the invention, each bed and chair is movable and may be located in a different bay from hour to hour or day to day. The beds and chairs will then be tagged with an active tag. The bay-level location of each bed or bay is established through the method shown in Figure 5 as each tagged bed or chair is moved into a bay. Subsequently, when a patient sits or lies in chair or bed, the location of the patient is derived from the bay-level location of the chair or bed.
[0056] FIG. 6 is a block diagram illustrating system components used in the tag as seen in FIG. 1, in some alternate embodiments of the invention. The tag 600 includes a low energy BLE transceiver 601 that works to transmit and receive Bluetooth RF signals. The BLE transceiver 601 is connected to a microprocessor 603 for controlling the operation of the transceiver. The BLE transceiver is also connected to an antenna 605 for providing communication to other devices. The tag further includes an accelerometer 607 connected to microprocessor 603 for detecting motion of the tag. The tag 600 further includes a unique power management system where a battery 611 is connected to the microprocessor 603 and accelerometer 607 where the battery 611 works to power these devices in one operating mode. In the event the battery is below some predetermined threshold and/or is dead or spent, an energy harvesting circuit, such as a photocell using light energy, or other energy harvester 613, can be used to power the device for specific tasks. More specifically, the photocell or other energy harvester 613 connects to an energy storage device 615 to charge the storage device 615 for use in tasks requiring short bursts of energy to power the tag 600. The energy storage 615 then charges a capacitor 617, connected to the BLE transceiver 601 and microprocessor 603, for energizing these devices for such limited periods of time e.g. when the tag is misplaced and has a dead battery.
[0057] Thus, the tag 600 includes a novel feature not taught in the prior art namely: the tag 600 is rarely spent nor will it ever be fully discharged since it will not die due to battery depletion. The photocell or other energy harvester 613 and energy storage 615 are used to provide energy for operating the tag for limited periods. Using this technique, when the battery is depleted, the photocell charges the energy storage device 615 for operating the tag 600 for limited tasks including running an initialization process, executing software in the tag, transmitting a message that can be used for tag location
[0058] Those skilled in the art will recognize that energy harvesting in itself is not unique, but has been employed in other wireless sensors. Although battery- powered tags are common in the RTLS industry, the use of two energy sources with load-sharing or switching is novel. Current devices often require more energy than can be harvested in a hospital environment, and a balancing of the two sources i.e. battery power and energy harvesting is difficult and impractical. But the current invention is unique in its ability to employ battery and energy harvesting in two operating modes that can be optimally combined and dynamically chosen with a simple switchover. These processes are employed for the explicit purpose of using the battery when it has sufficient energy to achieve low-latency, highly-accurate locating, but also use the energy harvesting when necessary to achieve high-latency, sufficiently-accurate locating for dead-battery tags.
[0059] FIG. 7. is a flow chart outlining the process 700 by which the tag 600 optimally uses both power sources. The process starts 701 with the tag using the battery power 703. The tag will use the battery power to operate in Operating Model, transmitting frequently enough to achieve low-latency and highly accurate locations 705. Energy harvesting may occur when the tag is in
Operating Mode 1 but the harvested energy is never used. However, when the battery nears or reaches exhaustion as determined by the tag’s internal status monitoring 707 while in a first Operating Mode 1 , the tag will perform a simple switchover 709 to a second Operating Mode 2, at which time the tag uses harvested energy to send infrequent transmissions 711, including an indication that the tag is operating in a dead-battery status, achieving high-latency but survivable locating by the RTLS system.
[0060] Thus, the present invention describes a new wireless technology available for RTLS systems in healthcare that makes the RTLS more reliable and a long- lived survivability for use in hospitals. Hospitals may survive a period of battery depletion which causes tags to become un-locatable and un-serviceable. Instead, tags can transmit a location signal at some periodic interval, e.g. at least once per day. This allows the system manager to locate the dead-battery tag(s), service it, and return it to normal operating mode, without having to search an entire hospital for a non-reporting, dead-battery tag.
[0061] RTLS systems with active tags in common use usually employ a process to monitor the battery status of the tag, and attempt to alert or warn system managers when a tag is reaching a low-battery status and needs to be serviced. Unfortunately, these processes are often unsuccessful in notifying the system’s manager in time, or the system’s manager is unable to replace the battery or tag before the battery fails. Once a battery fails on a tag or badge, and the asset or person moves to a new location, their location changes are invisible to the RTLS system. It becomes very difficult to find a dead-battery tag for several reasons: the tag can be carried anywhere within a large building like a hospital, and a dead tag looks exactly like a live tag, so a visual inspection is no help. Large-scale failures of 5% or 10% of tag batteries often cause a system’s location reports to become unreliable, since a significant fraction of the tagged assets or people are not reporting to the system, and users lose faith in the ability of the system to track the tagged items and badged personnel. The value, efficiencies and safety features of the system are inhibited when large numbers of tag and badge batteries are dead.
[0062] Some non-RTLS sensory systems are beginning to be introduced into the market which use energy harvesting to power the sensors. These devices lack a battery. Their advantage is that they do not have a battery that dies and renders the sensor useless. However, even with state-of-the art energy harvesting, the use of energy-harvesting technology alone is not practical for powering RTLS tags for their entire useful life. In practice, either the energy harvesting circuitry makes the tag so large as to be impractical for tagging small assets, or the energy harvesting circuitry does not harvest enough energy to power a tag that can be located accurately at low latency.
[0063] In one embodiment of the current invention, the active tags feature both a battery, and energy-harvesting circuitry, and operate in two power modes at various times, switching between the two modes. When a tag’s battery provides adequate power, the tag uses a first operating mode which uses the battery to transmit frequent locating signals, for low-latency and high-accuracy locating.
But when a tag’s battery fails, the tag switches to a second operating mode. The second operating mode uses the energy-harvested power to transmit less-frequent locating signals, so that the tag can continue to be located when the battery is dead or at an inoperative level. “Adequate power” for the first operating mode is defined as battery power sufficient to energize the tag’s microprocessor and radio transceiver to successfully format, generate and send a radio transmission that the RTLS can use to locate the tag.
[0064] In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below.
Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.

Claims

We claim:
1. A real-time location system (RTLS) having tags, bay-level event sensors, bridges, and a location server for providing people and asset-tag locating, comprising:
at least one tag which transmits a report of its motion status as sensed by its accelerometer;
at least one bay-level event sensor, which transmits a report of motion events that occur in a bay to a location engine;
at least one bridge for receiving reports from at least one tag and measuring at least one characteristic of the received transmissions, including received signal strength, and forwarding those reports to a central server, and which also receives transmissions of reports from at least one bay-level event sensors, which report motion events that occur in a bay; and
a location engine utilizing a both received-signal-strength information and bay-level motion-sensing information for determining bay-level location of the at least one tag.
2. The RTLS as in claim 1, wherein the at least one tag further comprising: a transceiver;
a microprocessor for driving the transceiver;
a battery for powering the transceiver;
and an accelerometer for detecting motion, used by the microprocessor to determine and report changes in the motion-status of the tag.
3. The tag as in claim 2, wherein the tag’s transceiver complies with the specifications of at least one of the set of standards defining Bluetooth Low Energy (BLE), Wi-Fi, or IEEE 802.15.4
4. The RTLS as in claim 1, the at least one bay-level event sensor comprising: a transceiver;
a microprocessor for operating the transceiver;
a sensor for detecting motion events in the bay-level-event-sensor’s bay; and
a power supply for powering the transceiver and the microprocessor;
5. The bay-level event sensor as in claim 4, wherein the sensor is one of the set of a pressure sensor, a passive infrared sensor, a visible-light camera, or a thermo graphic camera.
6. A real-time location system (RTLS) having tags, room-level event sensors, bridges, and a location server for providing people and asset-tag locating, comprising:
at least one tag which transmits a report of its motion status as sensed by its accelerometer;
at least one room-level event sensor, which transmits a report of its sensation of motion events that occur in a room;
at least one bridge for receiving reports from at least one tag and measuring at least one characteristics of the received transmissions, including received signal strength, and forwarding those reports to a central server; and a location engine utilizing a both received-signal-strength information and room-level motion-sensing information for determining room-level location of the at least one tag.
7. The RTLS as in claim 6, the at least one tag further comprising:
a transceiver;
a microprocessor for driving the transceiver;
a battery for powering the transceiver; and
an accelerometer for detecting motion, used by the microprocessor to determine and report changes in the motion-status of the tag.
8. The tag as in claim 7, wherein the tag’s transceiver complies with the specifications of at least one of the set of standards defining Bluetooth Low Energy (BLE), Wi-Fi, or IEEE 802.15.4
9. The RTLS as in claim 6, the at least one room-level event sensor comprising: a transceiver;
a microprocessor for operating the transceiver;
a sensor for detecting motion events in the room-level event sensor’s room; and
a power supply for powering the transceiver and the microprocessor;
10. The room-level event sensor as in claim 9, wherein the sensor is one of the set of a pressure sensor, a passive infrared sensor, a visible-light camera, or a thermo graphic camera.
11. The room-level event sensor as in claim 9, wherein the sensor transmits its detection of motion events through one of a wireless network or a wired network to the location engine.
12. A real-time location system (RTLS) having tags, room-level or bay-level event sensors, bridges, and a location server for providing people and asset-tag locating, comprising:
at least one room-level or bay-level event sensor, which wirelessly transmits a report of its sensation of motion events that occur in a room or bay; at least one tag for listening for radio transmissions from the at least one room-level or bay-level event sensor and measuring multiple characteristics of those received transmissions, including received signal strength and the report of motion events in the room-level or bay-level event sensor’s room or bay, where accelerometer-sensed-motion status of the tag is compared to motion events received the room-level or bay-level event sensors’ transmissions, and location- update messages are transmitted to the at least one bridge; and
at least one bridge for receiving reports from at least one tag and forwarding those location-update messages to a central server;
a location engine utilizing both received-signal-strength information and room-level or bay-level motion-sensing information for determining room-level or bay-level location of the at least one tag.
13. The RTLS as in claim 12, the at least one tag further comprising:
a transceiver;
a microprocessor for driving the transceiver;
a battery for powering the transceiver; and
an accelerometer for detecting motion, used by the microprocessor to determine and report changes in the motion-status of the tag.
14. The tag as in claim 13, wherein the tag’s transceiver complies with the specifications of at least one of the set of standards defining Bluetooth Low Energy (BLE), Wi-Fi, or IEEE 802.15.4
15. The RTLS as in claim 12, the at least one room-level or bay-level event sensor comprising:
a transceiver;
a microprocessor for operating the transceiver;
a sensor for detecting motion events in the bay-level event sensor’s bay; and
a power supply for powering the transceiver and the microprocessor;
16. The room-level or bay-level event sensor as in claim 15, wherein the sensor is one of the set of a pressure sensor, a passive infrared sensor, a visible-light camera, or a thermo-graphic camera.
17. The room-level or bay-level event sensor as in claim 15, wherein the sensor transmits its detection of motion events through one of a wireless network or a wired network to the location engine.
18. A real-time location system (RTLS) having tags, room-level or bay-level event sensors, bridges, and a location server for providing people and asset-tag locating, comprising:
at least one room-level or bay-level event sensor for transmitting
Bluetooth low energy (BLE) transmissions, equipped with sensor that detects motion events, and transmitting recent history of motion events sensed in the room-level or bay-level-event-sensor’s room or bay; at least one bridge for receiving location-update messages from at least one tag and measuring multiple characteristics of the received location-update messages, including received signal strength;
at least one tag for listening for BLE advertisements from the room-level or bay-level event sensors and measuring multiple characteristics of the received advertisements, including received signal strength and a series of advertisements of motion events in the room-level or bay-level-event-sensor’s room or bay, where accelerometer-sensed-motion status of the tag is compared to the motion events in the room-level or bay-level event sensors’ transmissions, and location- update messages are transmitted to the at least one bridge;
a location engine utilizing location-determining methods comprising: a first location method for calculating a first location estimate for the at least one tag, based on radio characteristics of BLE room-level or bay-level event sensor signals emitted by at least one room-level or bay-level event sensor in fixed locations and received by the at least one tag, and transmitted to the central location server;
a second location method for calculating a second location estimate for the at least one tag, based on comparing motion events in the room-level or bay- level-event-sensors’ rooms or bays, and the coincident accelerometer-determined motion status of the at least one tag that is likely in the room or bay; and
a third location method for combining the first location estimate and second location estimate to determine a location result for the at least one tag.
19. A method of estimating bay-location for at least one asset tag used in a real time location system (RTLS), comprising the steps of:
calculating a first location estimate using a first location method for the at least one tag, based on radio signal-strength characteristics; calculating a second location estimate using a second location method for the at least one tag, based on matching motion events in the room-level or bay- level event-sensors’ rooms or bays, and the coincident history of changes in accelerometer-determined motion status of the at least one tag that is likely in the room or bay; and
combining the first and second location estimates using a third location method for determining a location result for the at least one tag.
20. A tag for use in a real-time locating system (RTLS) comprising:
a wireless transceiver;
a microprocessor for operating the transceiver;
a battery for powering the transceiver and microprocessor;
an energy harvesting device connected to an energy storage device;
a capacitor connected to the energy storage device; and
wherein the energy harvesting device charges the energy storage device so the capacitor can power the microprocessor and transceiver for performing limited tasks upon battery depletion.
21. The tag for use in an RTLS system as in claim 20, wherein the tag can transmit with a dead battery.
22. The tag for use in an RTLS system as in claim 20, wherein the tag operates in a first mode of operation when the tag provides adequate battery power and a second mode of operation when the tag provides less than adequate battery power.
23. The tag for use in an RTLS as in claim 22, wherein the first mode of operation is a frequent transmission, and the second mode of operation is a less frequent transmission.
24. A location system for estimating the room-location of a portable device in a building, comprising:
at least one room-level or bay-level event sensor, which transmits a report of motion events that occur in a room or bay;
at least one portable device for listening for radio transmissions from the at least one room-level or bay-level event sensor and measuring multiple characteristics of the received transmissions, including received signal strength indication (RSSI) and a motion status of the sensor’s room-location or bay- location; and
where patterns of accelerometer-sensed-motion status of the portable device are compared to patterns of the motion status in the sensor’s radio transmissions, for determining room-location of the at least one portable device.
25. The location system as in claim 24, wherein the at least one room-level or bay-level event sensor comprising:
a radio transceiver;
a microprocessor for operating the transceiver;
an event sensor for detecting motion in the sensor’s room;
a battery for powering the transceiver and the microprocessor; and at least one antenna for broadcasting the radio transmission from the transceiver to portable devices in proximity to the sensor.
26. The location system as in claim 24, wherein the at least one portable device estimates its own location based upon at least one of current signal strength readings, past signal strength readings, changes in motion status received in the sensor transmission, and accelerometer/motion status of the portable device.
27. The location system as in claim 24, wherein the at least one portable device estimates its own location based upon at least one of current signal strength readings, past signal strength readings, changes in motion status received in the sensors’ transmissions, accelerometer/motion status of the portable device, and sensor transmissions that include the room-type where the sensor is installed.
28. The location system as in claim 24, wherein the at least one portable device estimates its own location based upon at least one of current signal strength readings, past signal strength readings, changes in motion status received in the sensors’ transmissions, accelerometer/motion status of the portable device, and sensor transmissions that include the identified floor where the sensor is installed.
29. The location system as in claim 24, where the portable device is at least one of a mobile telephone, tablet or laptop computer.
30. A real-time location system (RTLS) having tags, room-level event sensors, bridges, and a location server for providing people and asset-tag locating, comprising:
at least one tag which transmits a report of its motion status as sensed by its accelerometer;
at least one room-level event sensor, which transmits a report of its sensation of motion events that occur in a room including a report of the tag transmissions it receives; at least one bridge for receiving reports from at least one tag and measuring at least one characteristics of the received transmissions, including received signal strength, and forwarding those reports to a central server; and a location engine utilizing a both received-signal-strength information and room-level motion-sensing information for determining room-level location of the at least one tag.
31. The RTLS as in claim 30, the at least one tag further comprising:
a transceiver;
a microprocessor for driving the transceiver;
a battery for powering the transceiver; and
an accelerometer for detecting motion, used by the microprocessor to determine and report changes in the motion-status of the tag.
32. The tag as in claim 31 , wherein the tag’s transceiver complies with the specifications of at least one of the set of standards defining Bluetooth Low Energy (BLE), Wi-Fi, or IEEE 802.15.4
33. The RTLS as in claim 30, the at least one room-level event sensor comprising:
at least one transceiver;
a microprocessor for operating the transceivers;
a sensor for detecting motion events in the room-level event sensors; and a power supply for powering the transceivers and the microprocessor;
34. The room-level event sensor as in claim 33, wherein the sensor is one of a pressure sensor, a passive infrared sensor, a visible-light camera, or a thermo graphic camera.
35. The room-level event sensor as in claim 33, wherein the sensor transmits its detection of motion events and tag transmissions through one of a wireless network or a wired network to the location engine.
PCT/US2019/037667 2018-06-18 2019-06-18 A real-time location system (rtls) that uses a combination of event sensors and rssi measurements to determine room-and-bay-location of tags WO2019246049A1 (en)

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Applications Claiming Priority (13)

Application Number Priority Date Filing Date Title
US16/010,732 2018-06-18
US16/010,747 US10251020B1 (en) 2016-05-31 2018-06-18 Bluetooth low energy (BLE) real-time location system (RTLS) having tags, beacons and bridges, that use a combination of motion detection and RSSI measurements to determine room-location of the tags
US16/010,747 2018-06-18
US16/010,732 US10231078B1 (en) 2016-05-31 2018-06-18 Bluetooth low energy (BLE) real-time location system (RTLS) having simple transmitting tags, beacons and bridges, that use a combination of motion detection and RSSI measurements to determine room-location of the tags
US16/214,890 US10390182B2 (en) 2016-05-31 2018-12-10 Real-time location system (RTLS) having tags, beacons and bridges, that uses a combination of motion detection and RSSI measurements to determine room-location of the tags
US16/214,979 2018-12-10
US16/214,979 US10412700B2 (en) 2016-05-31 2018-12-10 Portable-device-locating system that uses room-level motion sensors and RSSI measurements to determine precise room-location
US16/214,890 2018-12-10
US16/241,758 US10412541B2 (en) 2016-05-31 2019-01-07 Real-time location system (RTLS) that uses a combination of bed-and-bay-level event sensors and RSSI measurements to determine bay-location of tags
US16/241,758 2019-01-07
US16/241,737 2019-01-07
US14241737 2019-01-07
US16/241,737 US10354104B2 (en) 2016-05-31 2019-01-07 Real-time location system (RTLS) tag with battery and energy harvesting, which transmits a location signal when the battery is inoperative

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