US007106.189B2
`
`(12) United States Patent
`Burneske et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,106,189 B2
`Sep. 12, 2006
`
`(54) TRACKING SYSTEM AND METHODS
`THEREOF
`
`(75) Inventors: Gregory W. Burneske, Mankato, MN
`(US); Fred F. Schleifer, Prior Lake,
`MN (US)
`(73) Assignee: TraceTech Incorporated, Mankato,
`MN (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 133 days.
`(21) Appl. No.: 10/835,187
`(22) Filed:
`Apr. 29, 2004
`
`(*) Notice:
`
`(65)
`
`Prior Publication Data
`US 2005/0242947 A1
`Nov. 3, 2005
`
`(51) Int. Cl.
`(2006.01)
`G08B I/08
`(52) U.S. Cl. ............................. 340/539.13: 340/539.1;
`340/539.11: 340/539.22; 340/573.1; 340/573.4:
`340/825.36; 340/825.49
`(58) Field of Classification Search ........... 340/539.13,
`340/539.1, 539.11, 539.14,539.16,539.22,
`340/539.23,572.1,571.4, 825.49, 825.69,
`340/825.72, 573.1, 573.4, 686.1, 825.36
`See application file for complete search history.
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`4,275,605 A
`4,290,316 A
`
`6/1981 Kennel ....................... T4,534
`9/1981 Noar et al. .................. T4,546
`
`1/1989 Sanderford, Jr. et al. ... 342/450
`4,799,062 A
`3/1994 Keyser ........................ 73/516
`5,291,784. A
`5/1994 Gruber .............
`... 384,536
`5,309,529 A
`7, 1994 Ficalora et al. ...
`... 356/350
`5,327.212 A
`1/1995 Kulmaczewski ...
`... T3/510
`5,383,363 A
`5,473,945 A 12/1995 Grieff et al. .................. 73/510
`5,635,739 A
`6/1997 Grieff et al. ......
`... 257/254
`6,046,531 A
`4/2000 Kikuchi et al. ...
`... 310,367
`6,083,353 A * 7/2000 Alexander, Jr. ...
`... 202,158
`6, 192,756 B1
`2/2001 Kikuchi et al. .......... 73,504.12
`6,198.394 B1* 3/2001 Jacobsen et al. ......... 340,573.1
`6.211,790 B1 * 4/2001 Radomsky et al. ...... 340,5734
`6,227,048 B1
`5/2001 Kikuchi et al. .......... T3,504.12
`6,230,563 B1
`5/2001 Clark et al. .............. T3,504.04
`6,344,794 B1
`2/2002 Ulrich et al. ............... 340,539
`6,439,051 B1
`8, 2002 Kikuchi et al. .......... 73,504.12
`6,933,849 B1* 8/2005 Sawyer .............
`... 340,572.4
`2001/0001928 A1
`5/2001 Kikuchi et al. .......... T3,504.12
`2003/0231098 A1 12/2003 Wan ............................ 338/32
`2004/0021569 A1
`2/2004 Lepkofker et al. ....... 340,568.1
`
`FOREIGN PATENT DOCUMENTS
`
`T 2002
`
`WO
`WO O2/O56274 A1
`* cited by examiner
`Primary Examiner Hung Nguyen
`(74) Attorney, Agent, or Firm—Medlen & Carroll, LLP
`(57)
`ABSTRACT
`
`The present invention relates generally to tracking systems
`and methods for monitoring the location of an asset or group
`of assets. In particular, the present invention provides sys
`tems for monitoring the location of a large group of assets.
`Furthermore, the present invention provides systems and
`methods for identifying an asset within a group of assets.
`
`42 Claims, 7 Drawing Sheets
`
`(260)
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`(270)
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`Power
`Supply
`
`Non-volatile
`Memory
`
`(280}
`Sensor Signal
`Conditioning
`and Sampling
`
`(230)
`
`(260)
`
`Processor
`
`Wieless
`Communications
`Apparatus
`
`(240)
`
`
`
`Processor
`Memory
`
`(200)
`
`20C)
`
`(200)
`
`(210)
`
`(210)
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`(220)
`
`(220)
`
`(220)
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`X Axis
`Accelerometer
`
`Y Axis
`AcceleIonieter
`
`Zit Axis
`Accelerometer
`
`8. Roll
`Gyro
`
`9 Roll
`Gyro
`
`GyTo
`
`Hx Magnetic
`Field Sensor
`(optional)
`
`Hy Magnetic
`Field Sensor
`optional
`
`H. Magnetic
`Field Sensor
`(optional
`
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`U.S. Patent
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`Sep. 12, 2006
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`Sheet 1 of 7
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`US 7,106,189 B2
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`
`
`
`
`Homing Station
`110
`
`Communication
`Network
`120
`
`Tracking Device
`100
`
`Manual Alignment
`Fixture
`130
`
`Figure 1
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`U.S. Patent
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`Sep. 12, 2006
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`Sheet 2 of 7
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`US 7,106,189 B2
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`(200)
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`(200)
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`(200)
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`(210)
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`(210)
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`(210)
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`(220)
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`(220)
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`(220)
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`X Axis
`Accelerometer
`
`YB Axis
`Accelerometer
`
`Ze Axis
`Accelerometer
`
`6x Roll
`Gyro
`
`0y Roll
`Gyro
`
`0. Roll
`Gyro
`
`Hx Magnetic
`Field Sensor
`(optional)
`
`Hy Magnetic
`Field Sensor
`(optional
`
`H. Magnetic
`Field Sensor
`(optional
`
`(260)
`
`(270)
`
`Power
`Supply
`
`Non-volatile
`Memory
`
`(280)
`
`(230)
`
`(260)
`
`Sensor Signal
`Conditioning
`and Sampling
`
`Processor
`
`Wireless
`Communications
`Apparatus
`
`(240)
`
`
`
`Processor
`Memory
`
`Figure 2
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`U.S. Patent
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`Sep. 12, 2006
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`Sheet 3 of 7
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`US 7,106,189 B2
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`Figure 3
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`U.S. Patent
`U.S. Patent
`
`Sep. 12, 2006
`Sep. 12, 2006
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`Sheet 4 of 7
`Sheet 4 0f 7
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`US 7,106,189 B2
`US 7,106,189 B2
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`|PR2020-01192
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`U.S. Patent
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`Sep. 12, 2006
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`Sheet 5 of 7
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`US 7,106.189 B2
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`(110)
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`
`
`(300)
`
`Localizing
`Transmitter
`
`Tracking
`Device
`EO)
`
`
`
`(330)
`
`(320)
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`
`
`Communication
`Network Memory
`
`Communication
`Network
`Server
`
`(340) - Z
`
`Access
`Point
`
`Access
`Point
`
`Access
`Point
`
`(100)
`
`
`
`Tracking
`Device
`
`Tracking
`Device
`
`Tracking
`Device
`
`Tracking
`Device
`
`Figure 5
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`U.S. Patent
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`Sep. 12, 2006
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`Sheet 6 of 7
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`US 7,106,189 B2
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`True Z
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`
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`Tracking
`Device
`100
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`
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`WectO
`
`Figure 6
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`True X-Y Plane
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`ZA axis tilt error angle
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`XA-YA Plane
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`U.S. Patent
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`Sep. 12, 2006
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`Sheet 7 Of 7
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`US 7,106,189 B2
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`
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`True X direction
`parallel with
`Earth' magnetic
`field - North
`-O-
`
`Figure 7
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`US 7,106,189 B2
`
`1.
`TRACKING SYSTEMAND METHODS
`THEREOF
`
`FIELD OF THE INVENTION
`
`The present invention relates generally to tracking sys
`tems and methods for monitoring the location of an asset or
`group of assets. In particular, the present invention provides
`systems for monitoring the location of each member of a
`large group of assets. Furthermore, the present invention
`provides systems and methods for uniquely identifying a
`single asset within a group of assets.
`
`BACKGROUND OF THE INVENTION
`
`A variety of methods and systems exist for tracking and
`locating assets and personnel in a facility Such as a hospital
`or a factory. Present tracking methods currently available
`fall into several broad categories of operation: 1) control
`point; 2) time of arrival; and 3) GPS.
`In control point schemes asset tracking tags are affixed to
`assets to be tracked. One Such control point approach is
`presented in U.S. Pat. No. 6,344,794. Other control point
`methods are based on RFID technology similar to the system
`marketed by AXCESS Inc. The tracking tags can be either
`passive (e.g., deriving power from an external source) or
`active (e.g., deriving power from an internal Source). The
`tracking tags emit a signal either upon request, periodically
`or sporadically. The signal can be a light signal, infra-red or
`RF signal and is modulated with an identification number
`unique to the asset to which the tracking tag is affixed.
`Control point schemes require that a multitude of control
`points be established. Control points are usually established
`at doorways or in the geometric center of rooms of interest.
`At each control point a receiver, reader or access point is
`placed. The control points are typically tied together by a
`communications network which may include a central pro
`cessor and database. When the tracking tag is in close
`proximity to a control point, the control point receives an
`identification number signal from the tracking tag.
`There are several limitations to control point systems as
`they relate to asset tracking. The ability of the control point
`system to resolve the precise location of a tracking tag is
`limited. The control point system can only report that a given
`tracking tag is either within range or not within range of a
`given control point. In addition, there are large gaps in
`coverage between control points due to the propagation
`characteristics of IR and RF signal energy.
`Time of arrival tracking systems determine the location of
`an asset by measuring the time it takes for radio signals to
`travel from multiple fixed radio antennas to the asset track
`ing tag. Conversely, a time of arrival system can be estab
`lished by measuring the time it takes the signal to travel from
`the asset tracking tag to multiple fixed antennas. In some
`systems the multiple fixed antennas of time of arrival
`systems are installed specifically for the purpose of making
`time of arrival measurements. In still other systems time of
`arrival calculations are performed on signals emanating
`from antenna infrastructures that are already in place for
`other purposes such as wireless computer network access
`points or FM radio broadcast stations. One such time of
`arrival approach is presented in U.S. Pat. No. 4,799,062.
`There are several limitations to time of arrival systems as
`they relate to asset tracking. The ability of time of arrival
`systems to resolve location requires an accurate time refer
`ence be available throughout the system. Each transmitter
`and receiver must be synchronized, either by direct or
`
`2
`indirect means, to a known reference in order for time of
`arrival to be measured. Another set of limitations arises from
`the reflective nature of radio wave propagation. Multipath
`reflections can substantially increase the time of arrival for
`radio signals which will degrade the accuracy of any Such
`system. Multipath reflections are especially problematic in
`an indoor environment. Another problem with time of
`arrival systems is that their accuracy is a function of the
`spatial diversity and number of time-of-arrival paths that can
`be determined. This limits the useful coverage area of a
`system to those areas where a transmitting tracking tag is
`within range of a minimum of three reference receivers. It
`would be desirable for an asset tracking tag to reliably report
`its position in the case where only one receiver was in
`communication range.
`A well-known embodiment of a time of arrival system is
`the GPS satellite system. There are several limitations to the
`GPS system as it relates to asset tracking. The primary
`limitation is that GPS signals do not penetrate buildings and
`therefore assets in places such as hospitals and factories can
`not be located with GPS.
`U.S. patent application Ser. No. 10/432.339 provides an
`asset tracking system utilizing inertial sensors. Accelerom
`eters and gyroscopes are used to establish an inertial refer
`ence from which linear acceleration and roll rates are
`measured when the asset tracking tag is moved. A limitation
`with this tracking system is it provides no means of miti
`gating sensor errors inherent to all inertial sensor techniques
`Such as noise, drift, error in calibration factors, and mechani
`cal alignment errors.
`What is needed is a tracking system that may be used
`indoors and outdoors. Additionally, what is needed is a
`tracking system that permits precise detection of an asset
`location.
`
`SUMMARY OF THE INVENTION
`
`The present invention relates generally to tracking sys
`tems and methods for monitoring the location of an asset or
`members of a group of assets. In particular, the present
`invention provides systems for monitoring the location of
`each member within a large group of assets. Furthermore,
`the present invention provides systems and methods for
`uniquely identifying an asset within a group of assets.
`In certain embodiments, the present invention provides an
`asset tracking system. In preferred embodiments, the asset
`tracking system includes at least one tracking device,
`wherein each tracking device is associated with an asset,
`wherein each tracking device measures linear acceleration
`and roll rate, wherein each tracking device determines asset
`position, and wherein each tracking device detects and
`reduces measurement error. In other preferred embodiments,
`the asset tracking system includes a communication network
`configured to receive said asset position from each tracking
`device. In some preferred embodiments, the communication
`network participates in the detection and reduction of mea
`Surement error.
`In some embodiments, the communication network dis
`plays the asset position. In certain embodiments, the asset is
`a non-living entity. In other embodiments, the asset is a
`living entity.
`In some embodiments, each tracking device measures
`acceleration with at least one accelerometer. If the tracking
`device is associated with an asset that is allowed to rotate,
`each tracking device measures roll rate with at least one
`gyroscope.
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`In certain embodiments, the accelerometers measure lin
`ear acceleration. In certain embodiments, the gyroscopes
`measure roll rate.
`In other preferred embodiments, each tracking device
`further comprises magnetic sensors, wherein the magnetic
`sensors identify the tracking device's heading error.
`In other preferred embodiments, each tracking device
`further comprises a processor, wherein the processor
`receives accelerometer and gyroscope signals, uses those
`signals to calculate the tracking device's movement through
`space, detects errors in the accelerometer and gyroscope
`signals, and compensates for said measurement errors.
`In other preferred embodiments, each tracking device
`processor performs minimal processing on the accelerom
`eter and roll-rate signals, and the tracking device sends the
`accelerometer and roll-rate values to the communication
`network whereby computing elements in the network use the
`acceleration and roll-rate values to compute the tracking
`device's location.
`In still further embodiments, the asset tracking system
`further includes a homing station, wherein the homing
`station provides a reference position for each tracking
`device. In some preferred embodiments, the asset position is
`in reference to the reference position.
`In certain embodiments, the present invention provides a
`method of tracking an asset. In Such embodiments, the
`method provides an asset tracking system. In further
`embodiments, the method entails acquiring the asset posi
`tion for each asset.
`In certain embodiments, the present invention provides an
`asset tracking system, comprising at least one tracking
`device associated with an asset, wherein the at least one
`tracking device measures acceleration and roll rate, identi
`fies and mitigates measurement error, and determines asset
`position; and a communication network configured to
`receive the asset position from the at least one tracking
`device. In further embodiments, the communication network
`displays the asset position. In other embodiments, the asset
`is a non-living entity. In other embodiments, the asset is a
`living entity.
`In further embodiments, the at least one tracking device
`measures acceleration with at least one accelerometer. In
`further embodiments, the accelerometer measures linear
`acceleration. In further embodiments, the at least one track
`ing device measures roll rate with at least one gyroscope. In
`further embodiments the gyroscope measures roll rate. In yet
`other embodiments, the measurement error is selected from
`the group consisting of accelerometer measurement error,
`gyroscope measurement error, accelerometer linearity error,
`gyroscope linearity error, accelerometer noise, gyroscope
`noise, accelerometer drift, gyroscope drift, accelerometer
`misalignment, and gyroscope misalignment.
`In other embodiments, the at least one tracking device
`further comprises a processor. In yet other embodiments, the
`processor performs calculations to determine the location of
`the at least one tracking device. In other embodiments, the
`processor identifies accelerometer measurement error. In
`further embodiments, the processor identifies gyroscope
`measurement error.
`In other embodiments, the tracking device further com
`60
`prises at least one magnetic sensor. In further embodiments,
`the at least one magnetic sensor measures the difference
`between the tracking device computational frame of refer
`ence and Earth’s magnetic field. In yet other embodiments,
`the asset tracking system further comprises a homing sta
`tion, wherein the homing station provides a homing station
`reference position for the at least one tracking device. In
`
`45
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`4
`other embodiments, the asset position is in reference to the
`homing station reference position.
`In certain embodiments, the present invention provides an
`asset tracking system, comprising at least one tracking
`device associated with an asset, wherein the at least one
`tracking device comprises at least one accelerometer, at least
`one gyroscope, and a processor, wherein the at least one
`accelerometer measures linear acceleration, wherein the at
`least one gyroscope measures roll rate, wherein the proces
`sor identifies and mitigates accelerometer measurement
`error and gyroscope measurement error, wherein the pro
`cessor determines asset position; and a communication
`network configured to receive the asset position from the at
`least one tracking device, wherein the communication net
`work displays the asset position.
`In certain embodiments, the present invention provides a
`method of tracking an asset, comprising providing an asset
`tracking system comprising at least one tracking device
`associated with an asset, wherein the at least one tracking
`device measures acceleration, identifies and mitigates mea
`Surement error, and determines asset position; and a com
`munication network configured to receive the asset position
`from the at least one tracking device; and acquiring the asset
`position for each asset.
`In other embodiments, the communication network dis
`plays the asset position. In some embodiments, the asset is
`a non-living entity. In other embodiments, the asset is a
`living entity.
`In some embodiments, the at least one accelerometer
`tracking device measures linear acceleration. In other
`embodiments, the at least one gyroscope measures roll rate.
`In other embodiments, the measurement error is inaccurate
`acceleration measurement. In further embodiments, the at
`least one tracking device further comprises at least one
`magnetic sensor, wherein the at least one magnetic sensor
`identifies alignment errors with the at least one accelerom
`eter and the at least one gyroscope.
`In further embodiments, the at least one tracking device
`further comprises a processor, wherein the processor iden
`tifies and mitigates the measurement error. In further
`embodiments, the method further comprising a homing
`station, wherein the homing station provides a homing
`station reference position for the at least one tracking device.
`In further embodiments, the asset position is in reference to
`the homing station reference position.
`In certain embodiments, the present invention provides a
`method of tracking an asset, comprising providing a tracking
`device associated with an asset and an initial reference
`position, wherein the tracking device is configured to mea
`Sure linear acceleration and roll rate, wherein the tracking
`device is configured to mitigate measurement error associ
`ated with the linear acceleration and roll rate measurements,
`wherein the tracking device is configured to determine the
`position of the asset; acquiring the linear acceleration and
`roll rate measurements; mitigating the measurement errors
`associated with the linear acceleration and roll rate mea
`Surements, and determining the position of the asset in
`relation to the initial reference position.
`In further embodiments, the tracking device obtains the
`initial reference position from a homing station. In further
`embodiments, the tracking device further comprises at least
`one accelerometer and at least one gyroscope. In other
`embodiments, the tracking device measures the linear accel
`eration with at least one accelerometer. In further embodi
`ments, the tracking device measures the roll rate with at least
`one gyroscope. In other embodiments, the tracking device
`further comprises at least one magnetic sensor, wherein the
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`at least one magnetic sensor identifies alignment errors of
`the accelerometer and the gyroscope. In other embodiments,
`the asset is a non-living entity. In other embodiments, the
`asset is a living entity. In further embodiments, the mitigat
`ing the measurement errors involves adjusting the linear
`acceleration and roll rate measurements for accelerometer
`and gyroscope alignment error. In further embodiments, the
`mitigating the measurement errors involves filtering and
`digitally sampling the linear acceleration and roll rate mea
`surements with initial calibration factors. In other embodi
`ments, the mitigating the measurement errors involves reset
`ting the initial reference position prior to taking the linear
`acceleration and roll rate measurement. In yet other embodi
`ments, the determining the asset position involves process
`ing the linear and roll rate measurements. In further embodi
`ments, the processing involves integration calculations.
`In certain embodiments, the present invention provides a
`method of tracking an asset, comprising providing an asset
`tracking system comprising at least one tracking device
`associated with an asset, wherein the at least one tracking
`device measures acceleration; and a communication net
`work configured to receive measurements from the at least
`one tracking device, identify and mitigate measurement
`error, and determine asset position for the at least one
`tracking device; and acquiring the asset position for each
`asset. In preferred embodiments, the communication net
`work displays the asset position. In further embodiments, the
`asset is a living or non-living entity.
`In further embodiments, the at least one accelerometer
`tracking device measures linear acceleration. In further
`embodiments, the at least one gyroscope measures roll rate.
`In preferred embodiments, the measurement error is inac
`curate acceleration measurement. In further embodiments,
`the at least one tracking device further comprises at least one
`magnetic sensor, wherein the at least one magnetic sensor
`identifies alignment errors with the at least one accelerom
`eter and the at least one gyroscope.
`In further embodiments, the at least one tracking device
`further comprises a processor, wherein the processor iden
`tifies and mitigates the measurement error. In even further
`embodiments, the method further comprises a homing sta
`tion, wherein the homing station provides a homing station
`reference position for the at least one tracking device. In
`further embodiments, the asset position is in reference to the
`homing station reference position. In yet further embodi
`ments, the communication network comprises a remote
`processor. In even further embodiments, the remote proces
`Sor determines the asset position for the at least one tracking
`device.
`
`As used herein, the terms “user reference frame,” “user
`coordinate system,” or similar terms, refer to a user-defined
`three-dimensional coordinate system for measuring or dis
`playing the tracking device's position. Coordinates in the
`users frame of reference are expressed, for example, as X,
`y, and Z.
`As used herein, the term “heading and attitude” and
`“attitude” refers to a full description of the tracking device's
`orientation (not position) in three-dimensional space. This is
`equivalent to the net effect of roll, pitch, and yaw maneuvers
`over time.
`As used herein, the term “homing field” refers to the
`localizing transmitter region.
`As used herein, the term “localizing transmitter refers to
`a device for sending a wireless signal that is received and
`used by a tracking device.
`As used herein, the term "derived position coordinates'
`refers the tracking device's position coordinates as deter
`mined by the tracking device's sensors and internal proces
`Sor, or as determined by a communication network server
`using sensor information provided by the tracking device via
`the communication network.
`As used herein, the term "derived heading refers the
`tracking device's heading as determined by the tracking
`device's sensors and internal processor, or as determined by
`a communication network server using sensor information
`provided by the tracking device via the communication
`network.
`
`DESCRIPTION OF THE FIGURES
`
`FIG. 1 presents a schematic of the asset tracking system.
`FIG. 2 presents a tracking device embodiment.
`FIG. 3 presents a schematic example of a tracking
`device's body-axes coordinate system.
`FIG. 4 presents a depiction of the tracking device's body
`axes and the user's frame of reference.
`FIG. 5 presents a schematic depiction of a homing station
`and communication network embodiments.
`FIG. 6 depicts the presence of gravity and the constant 1g
`downward force in relation to the tracking device's compu
`tation frame of reference.
`FIG. 7 depicts the presence of a magnetic field in relation
`to the tracking device's computational frame of reference.
`
`DETAILED DESCRIPTION
`
`The present invention provides tracking systems and
`methods for monitoring the location of an asset or group of
`assets. In particular, the present invention provides systems
`for monitoring the location of each member of a large group
`of assets. Furthermore, the present invention provides sys
`tems and methods for uniquely identifying a particular asset
`within a group of assets. The illustrated and preferred
`embodiments discuss these systems and methods. These
`systems and methods are well Suited for use with any type
`of asset tracking within any type of setting. FIGS. 1-7 show
`various preferred embodiments of the tracking device sys
`tems and methods of the present invention. The present
`invention is not limited to these particular embodiments.
`FIG. 1 presents a schematic of the present invention, and
`includes a tracking device 100, a homing station 110, a
`communication network 120, and a manual alignment fix
`ture 130. Generally, a tracking device 100 receives initial
`position coordinate information from a homing station 110
`or a manual alignment fixture 130. As the tracking device
`100 changes location within its computational frame, posi
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`DEFINITIONS
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`To facilitate understanding of the invention, a number of
`terms are defined below.
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`As used herein, the term “asset' refers to any living or
`nonliving entity.
`As used herein, the term “tracking-device body axes”
`refers to a three-dimensional coordinate system defined by
`or fixed to the tracking device's enclosure.
`As used herein, the terms “tracking-device computational
`frame,” “computational frame of reference.” “tracking
`device computational frame of reference,” or similar terms,
`refer to a three-dimensional coordinate system for integrat
`ing the tracking device's location and attitude through time.
`Coordinates in the computational frame of reference are
`expressed, for example, as X, y, and Z.
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`IPR2020-01192
`Apple EX1014 Page 11
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`US 7,106,189 B2
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`tional information is sent to the communication network
`120. The communication network 120 is configured to
`present the location of a tracking device 100. For conve
`nience, the description of the invention is presented in the
`following sections: I) Tracking Systems; and II) Uses of
`Tracking Systems.
`I. Tracking Systems
`The present invention provides tracking systems for the
`tracking of assets. As shown in FIG. 1, the tracking systems
`of the present invention include at least one tracking device
`100, at least one homing station 110, communication net
`work 120. In some embodiments, a manual alignment fixture
`130 is further provided. Additionally, the tracking systems
`provide reliable and accurate asset information through
`detection and compensation of tracking device measurement
`eO.
`A. Tracking Device
`FIG. 2 presents a schematic depiction of an embodiment
`of a tracking device 100 of the present invention. Each
`tracking device 100 within the system associates with an
`asset (e.g., is affixed to the asset with screws, adhesive foam
`tape, etc.). The present invention is not limited to a particular
`kind of asset. In preferred embodiments, the asset includes
`living and non-living entities. The present invention is not
`limited to an asset of a particular size.
`In preferred embodiments, a tracking device 100 of the
`present invention measures motion through measurement of
`linear acceleration and roll rates versus time. In further
`preferred embodiments, a tracking device 100 uses mea
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`Sured linear acceleration and roll rates to calculate position
`within the computational frame of reference. In even further
`embodiments, as a tracking device 100 changes location, the
`position coordinates are updated by, for example, adding
`calculated translation values from the integration and trans
`formation of measured roll and acceleration.
`Still referring to FIG. 2, the tracking device 100 com
`prises three accelerometers 200 positioned to measure linear
`acceleration. In preferred embodiments, the accelerometers
`200 are positioned within the tracking device 100 to measure
`acceleration components along three Substantially orthogo
`nal axes (e.g., X, Y, and Z) within the tracking device body
`axes (see FIG. 3). The present invention is not limited to a
`particular type of accelerometer 200. In preferred embodi
`ments, the accelerometer 200 is a linear accelerometer. The
`present invention is not limited to a particular type of linear
`accelerometer. Indeed, a variety of linear accelerometers
`find use in the present invention, including, but not limited
`to, the ADXL150 and ADXL250 (Analog Devices), and the
`MMA1250D and VTI-SCA320-CC5V1G (Motorola). In
`other embodiments, the present invention utilizes linear
`accelerometers described in U.S. Pat. Nos. 5,291,784; 5,383,
`363; 5,408,879; 5,473,945; 5,635,739; 6,046,531; 6,192,
`756; each herein incorporated by reference in their entirety.
`In preferred embodiments, the ADXL210EB (Analog
`Devices) linear accelerometer is used.
`It is recognized that a single accelerometer device may
`provide measurements along more than one axis. It is also
`recognized that more than three accelerometers may be
`employed to redundantly measure acceleration for the ben
`efit of reducing measurement error (e.g., noise) or improving
`accuracy. For the purposes of describing the nature of this
`invention, a single accelerometer is assigned to each
`orthogonal body axis with the task of measuring acceleration
`along that particular axis.
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`Still referring to FIG. 2, the tracking device 100 com
`prises three gyroscopes 210 positioned to measure roll rate
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`about three axes. In preferred embodiments, the gyroscopes
`210 are positioned in a tracking device 100 to measure the
`rotation or roll rate around three Substantially orthogonal
`axes (e.g., X, Y, and Z) within the tracking device's body
`axes coordinate system (see FIG. 3). The gyroscopes 210
`have fixed positions within the tracking device 100 enclo
`Sure, and the gyroscope measurements are in the tracking
`device's body-axes coordinate system. The present inven
`tion is not limited to a particular type of gyroscope 210. In
`Some embodiments, the present invention utilizes gyro
`scopes 210 described in U.S. Pat. Nos.: 4,275,605; 4,290,
`316; 5,309,529; 5,327,212: 6,227,048, 6,230,563, 6,439,
`051; and U.S. Patent Application No. US20010001928A1:
`each herein incorporated by reference in their entirety. In
`preferred embodiments, the ADXRS300 (Analog Devices)
`is used. The tracking device 100 is not limited to a particular
`positioning of the gyroscopes 210.
`It is recognized that a single gyroscope device may
`provide measurement outputs for more than one axis of
`rotation. Furthermore, it is recognized that more than three
`gyroscopes may be employed to provide redundant roll-rate
`measurements in order to reduce measurement noise or to
`improve the accuracy of the system. It is also recognized that
`a gyroscope may provide various types of measurement
`information (e.g., absolute angular change, roll rate).
`Still referring to FIG. 2, the tracking device 100 com
`prises at least one magnetic field sensor 220. The present
`invention is not limited to a particular type of magnetic field
`sensor 220. In preferred embodiments, the magnetic field
`sensor 220 is an arrangement of 3 single-axis magnetic field
`sensors. In some embodiments, the present invention pro
`