U.S. patent application number 13/618009 was filed with the patent office on 2013-01-10 for apparatus for measuring data for injury analysis with power management.
This patent application is currently assigned to Allen-Vanguard Corporation. Invention is credited to Alain BERDOZ, Jeffrey BYERS, Lock-Sui CHIN, Robert CORSARO, Daniel CROSSMAN, Jean-Philippe DIONNE, Phil FRANK, Peter HERDIC, Brian HOUSTON, Graham HUBLER, Jason KOST, Jeffrey LEVINE, Kenny OPACHKO, Doug WONG.
Application Number | 20130007936 13/618009 |
Document ID | / |
Family ID | 40717233 |
Filed Date | 2013-01-10 |
United States Patent
Application |
20130007936 |
Kind Code |
A1 |
LEVINE; Jeffrey ; et
al. |
January 10, 2013 |
Apparatus for Measuring Data for Injury Analysis with Power
Management
Abstract
An apparatus for recording data indicative of acceleration of a
part of a person's body or other object, including first memory
means for receiving acceleration data from an acceleration sensor,
second memory means operatively coupled to the first memory means
for receiving data from the first memory means, and a data transfer
controller for controlling the transfer of data from the first
memory means to the second memory means based on the acceleration
data.
Inventors: |
LEVINE; Jeffrey; (Nepean,
CA) ; WONG; Doug; (Ottawa, CA) ; CHIN;
Lock-Sui; (Ottawa, CA) ; DIONNE; Jean-Philippe;
(Gatineau, CA) ; CROSSMAN; Daniel; (Kanata,
CA) ; HERDIC; Peter; (Washington, DC) ;
HOUSTON; Brian; (Fairfax, VI) ; CORSARO; Robert;
(Waldorf, MD) ; HUBLER; Graham; (Highland, MD)
; BYERS; Jeffrey; (Fairfax Station, VI) ; OPACHKO;
Kenny; (Shantilly, VI) ; BERDOZ; Alain;
(Annandale, VI) ; FRANK; Phil; (Laurel, MD)
; KOST; Jason; (Burke, VT) |
Assignee: |
Allen-Vanguard Corporation
Ottawa
DC
The Government of the United States of America, as represented
by the Secretary of the Navy
Washington
|
Family ID: |
40717233 |
Appl. No.: |
13/618009 |
Filed: |
September 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12746370 |
Dec 20, 2010 |
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PCT/CA2008/002124 |
Dec 8, 2008 |
|
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13618009 |
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60996855 |
Dec 7, 2007 |
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Current U.S.
Class: |
2/6.6 ; 702/130;
702/141 |
Current CPC
Class: |
A61B 5/7275 20130101;
F41H 1/04 20130101; G01L 5/14 20130101; A42B 3/046 20130101; A61B
2562/0219 20130101; A61B 5/11 20130101; A61B 2560/0209 20130101;
G01P 1/127 20130101; A61B 5/6803 20130101; A61B 5/6814
20130101 |
Class at
Publication: |
2/6.6 ; 702/141;
702/130 |
International
Class: |
G01P 15/18 20060101
G01P015/18; A42B 3/30 20060101 A42B003/30; G01K 13/00 20060101
G01K013/00; F41H 1/04 20060101 F41H001/04; G01P 15/00 20060101
G01P015/00; G06F 15/00 20060101 G06F015/00 |
Claims
1. An apparatus for recording data indicative of acceleration of a
part of a person's body or other object, comprising first memory
means for receiving acceleration data from an acceleration sensor,
second memory means operatively coupled to the first memory means
for receiving data from the first memory means, and a data transfer
controller for controlling the transfer of data from the first
memory means to the second memory means based on the acceleration
data.
2. An apparatus as claimed in claim 1, wherein the first memory
means requires electrical power to hold data therein.
3. An apparatus as claimed in claim 1, wherein the second memory
means is capable of holding data therein in the absence of
electrical power or with less power than required by said first
memory means.
4. An apparatus as claimed in claim 1, wherein said controller is
adapted to enable the transfer of data from said first memory means
to said second memory means in response to and/or only in the event
of said acceleration data meeting a predetermined criteria.
5. An apparatus as claimed in claim 4, wherein said predetermined
criteria is one of (a) a sensed value of acceleration reaches a
predetermined value and (b) a sensed value of acceleration exceeds
a predetermined value.
6. An apparatus as claimed in claim 4, wherein said predetermined
value is at or above a value which is sufficient to cause injury or
is likely to cause injury to the part of the person.
7. An apparatus as claimed in claim 1, wherein the body part is a
person's head.
8. An apparatus as claimed in claim 1, wherein at least one of said
first and second memory means is an internal memory of a
processor.
9. An apparatus as claimed in claim 1, further comprising a third
memory means operatively coupled to said second memory means for
receiving data therefrom.
10. An apparatus as claimed in claim 9, further comprising a memory
controller for controlling the transfer of data from said second
memory to said third memory.
11. An apparatus as claimed in claim 11, wherein said memory
controller is conditioned to transfer acceleration data from said
second memory means to said third memory means only if said second
memory means contains acceleration data from a plurality of
separate events.
12. An apparatus as claimed in claim 10, wherein said memory
controller is adapted to transfer acceleration data relating to a
plurality of different events from said second memory means to said
third memory means in a single or the same write operation.
13. An apparatus as claimed in claim 12, wherein said memory
controller is adapted to transfer acceleration data relating to
three or more events in a single or the same operation.
14. An apparatus as claimed in claim 9, wherein said third memory
means is adapted to hold data in the absence of electrical power or
with less electrical power than required by at least one of said
first and second memory means.
15. An apparatus as claimed in claim 1, further comprising
monitoring means for monitoring the time of an acceleration event
and means for recording the time of the event in a manner in which
the time of the event is associated with acceleration data of the
event.
16. An apparatus as claimed claim 1, further comprising a
temperature sensor for sensing the temperature of one or more
components of the apparatus.
17. An apparatus as claimed in claim 16, further comprising means
for recording the temperature at the time of a recorded
acceleration event in such a manner that the temperature is
associated with the acceleration data of the event.
18. An apparatus as claimed in claim 1, further comprising sensing
means for sensing acceleration and providing a signal indicative of
the sensed acceleration to the first memory means.
19. An apparatus as claimed in claim 18, wherein said sensing means
comprises a plurality of sensors, each capable of measuring
acceleration in a single direction, and configured to measure
acceleration in a direction which is mutually perpendicular to the
direction of one or more other of said acceleration sensors.
20. An apparatus as claimed in claim 16, wherein said temperature
sensor and said first and second memory means are mounted on a
common substrate.
21. An apparatus as claimed in claim 1, wherein each of said first
and second memory means and said controller are mounted on a common
substrate.
22. An apparatus as claimed in claim 1, wherein said first and
second memory means and said controller are contained in a unit
adapted to be part of a helmet assembly.
23. An apparatus as claimed in claim 22, further comprising
structure for enabling the unit to be mounted to a helmet.
24. An apparatus as claimed in claim 23, wherein said structure
includes fastening means for releasably fastening the unit to the
helmet.
25. An apparatus as claimed in claim 1 adapted to be mounted on a
military or combat helmet.
26. An apparatus as claimed claim 24, wherein said sensing means is
adapted to sense accelerations having values resulting from a blast
or explosive force.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a continuation of co-pending U.S.
patent application Ser. No. 12/746,370, filed Jun. 4, 2010, which
is a national stage application of International Application No.
PCT/CA2008/002124, filed on Dec. 8, 2008, which claims the benefit
of U.S. Provisional Application No. 60/996,855, filed Dec. 7, 2007,
which are each incorporated by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to apparatus and methods for
measuring and recording data from potentially injurious events to
which humans may be exposed.
SUMMARY OF THE INVENTION
[0003] Embodiments of the present invention provide a data recorder
adapted for mounting on a combat helmet to measure and record
parameters indicative of head acceleration resulting from violent
events such as violent impact and blast events. Despite current
designs of head protection, exposure of a large number of soldiers
to detonation of improvised explosive devices (IEDs) has resulted
in a high occurrence of blast-induced traumatic brain injuries
(TBI). TBI has been noted to lead to injuries ranging from
headaches and mild concussions to severe casualties including
severe concussions and memory loss. The data recorder enables data
from violent events to be recorded and used to build a database of
head acceleration data induced by violent events which may be
correlated with injuries suffered. The data recorded from violent
events may be used to correlate injuries, especially brain
injuries, with event characteristics and severity, including
accumulated dosage and long-term and chronic symptoms. The analyzed
data may be used to determine optimal medical treatment based on
instant analysis of event data and/or making longer term medical
decisions. The data may be used to assess effectiveness of
protective equipment, both in helmet technology and other
applications.
[0004] Embodiments of the data recorder provide a small,
light-weight, self-contained digital recording system, capable of
recording acceleration waveforms experienced in violent events.
Embodiments of the data recorder are designed to mount on helmets
and monitor and record exposure to potentially harmful cranial
events. Embodiments of the datalogger enable both the direction and
magnitude of acceleration to be measured. In some embodiments, the
data recorder includes three accelerometers that are each only
sensitive to accelerations in a single direction (axis). The
accelerometers are mounted orthogonally to measure the vector
components of acceleration in three-dimensional space. Embodiments
of the data recorder enable acceleration to be measured by all
three accelerometers simultaneously, with the vector sum of their
signals indicating both the direction of the acceleration and the
magnitude of acceleration.
[0005] Embodiments of the data recorder include a power management
system for reducing the amount of power consumed by the device to
extend the time over which the device can remain operational in the
field. In particular, the power management system provides a means
of switching part(s) of the data recorder between active and
inactive states so that power required by those parts to perform a
particular function is only provided when the particular function
is to be performed.
[0006] Embodiments of the data recorder include a memory management
scheme for managing the recording of data and which is capable of
deciding which data to save and which to discard in order to reduce
the amount of memory space required, and also how to use the
available memory space to store the data efficiently and reduce
power.
[0007] According to one aspect of the present invention, there is
provided an apparatus for measuring acceleration of a person's head
or other object, comprising sensing means for sensing acceleration,
and a controller for controlling recording of data resulting from
the sensed acceleration, wherein the controller is adapted to
determine, based on the sensed acceleration, whether or not to
enable recording of the data.
[0008] In some embodiments, the controller is adapted to enable
recording of the data if the sensed acceleration meets a
predetermined criteria, for example, if the measured acceleration
reaches or exceeds a predetermined value. The predetermined or
threshold value may be a finite value below a value that would or
is likely to cause a predetermined injury to a person.
[0009] Some embodiments may be adapted to base the determination on
any other characteristic of the sensed acceleration, for example, a
time derivative of acceleration such as the slope of an impulse or
Fourier frequency component(s) in the waveforms. This may enable
even earlier detection of significant events.
[0010] In some embodiments, the apparatus comprises data receiving
means for receiving sensed acceleration data from the sensing
means, the receiving means requiring electrical power to enable the
data to be received thereby, and wherein the controller causes
electrical power to the receiving means to be controlled based on
the sensed acceleration.
[0011] In some embodiments, the controller is adapted to determine
whether or not the sensed acceleration meets a predetermined
criteria, and if the criteria is not met, the controller causes the
electrical power to be controlled such that the receiving means is
unable to receive the data. On the other hand, if the criteria is
met, the controller is adapted to cause the electrical power to be
controlled to enable the receiving means to receive the data.
[0012] Advantageously, the predetermined threshold value may be
selected to provide sufficient time for the receiving means to
change from an inactive state to an active state to receive
acceleration data indicative of an injury.
[0013] In some embodiments, the receiving means comprises any one
or more of signal conditioning means for conditioning the signal,
an analog-to-digital converter, a processor and a memory. The
memory may comprise a volatile memory such as a random access
memory.
[0014] Embodiments of the apparatus may further comprise a second
memory operatively coupled to the first memory for receiving data
therefrom. The second memory may comprise a non-volatile memory or
another memory requiring no power or less power than the first
memory to hold data.
[0015] In some embodiments, the apparatus further comprises
determining means for determining whether or not to transfer data
from the first memory to the second memory. The determination may
be based on the acceleration data. The determining means may be
adapted to cause the data to be transferred from the first memory
to the second memory, if the acceleration data meets a
predetermined criteria. The predetermined criteria may be, for
example, that a value of acceleration in the acceleration data
(which may or may not be the peak acceleration) is likely to be
sufficient to cause injury or has been previously determined to
cause injury. At least one of the first and second memories may be
an internal memory of a processor.
[0016] In some embodiments, the apparatus further comprises a third
memory operatively coupled to the second memory for receiving data
therefrom. A memory controller may be provided for controlling the
transfer of data from the second memory to the third memory. The
memory controller may be conditioned to transfer acceleration data
from the second and third memory only if the second memory contains
acceleration data from a plurality of separate events.
[0017] In some embodiments, the memory controller is adapted to
transfer acceleration data relating to a plurality of different
events from the second to the third memory in a single or the same
write operation. Advantageously, this transfer scheme assists in
reducing power since write operations can be power intensive. For
example, the memory controller may be adapted to transfer
acceleration data relating to three or more events in a single
operation, for example, 5, 10, 15 or 20 or any other number.
[0018] In some embodiments, the apparatus further comprises
monitoring means for monitoring the time of an acceleration event
and means for recording acceleration data of an event and the time
of the event. Advantageously, this arrangement allows acceleration
data to be time stamped so that it can be correlated with other
information that may be recorded about the event and which may
assist in the compilation and analysis of injury data.
[0019] The acceleration sensor may be adapted to sense acceleration
from an explosive force, and may for example, be capable of
measuring forces of 1,500 gs or more, 5,000 gs or more, 10,000 gs
or more or 15,000 gs or more.
[0020] In some embodiments, the data recording means is capable of
recording acceleration waveforms having frequencies in the range of
at least 500 to 1,000 Hz, or more.
[0021] In some embodiments, the data recording means is capable of
changing from an inactive state to an active state in less than 1
millisecond, for example, less than 500 microseconds or less than
400, 300 or 200 microseconds, or in about 100 microseconds or
less.
[0022] In some embodiments, the apparatus further comprises
monitoring means for monitoring a power source for providing power
to the apparatus.
[0023] In some embodiments, the apparatus further includes a
temperature sensor for sensing the temperature of one or more
components of the apparatus. As components of the data recorder,
for example, the sensors, may be temperature dependent, measuring
the temperature may assist in performing temperature compensation
and increasing the accuracy of the measurements, where needed.
[0024] The data recorder may be adapted to be mounted to a helmet,
for example, to the helmet shell, for example on the outside of the
shell. The data recorder may be adapted for releasably fastening to
the helmet so that it can be readily removed therefrom and
replaced, as necessary.
[0025] According to another aspect of the present invention, there
is provided an apparatus for measuring a parameter resulting from
exposure of a person to a physical event, comprising sensor means
for sensing said parameter, determining means for determining a
relationship between the value of the sensed parameter and a
predetermined value of said parameter, and a controller responsive
to the determining means for controlling a device in response to
the determination made by the determining means.
[0026] According to another aspect of the present invention, there
is provided an apparatus for measuring acceleration of a person's
head resulting from exposure of the head to a force, the apparatus
comprising sensing means for sensing said acceleration, determining
means for determining a relationship between the value of the
sensed acceleration and a predetermined value of acceleration, and
a controller responsive to said determining means for controlling a
device in response to the determination made by the determining
means.
[0027] In some embodiments, the sensing means comprises an
accelerometer for measuring acceleration in three mutually
orthogonal directions.
[0028] In some embodiments, the relationship determined by said
determining means is whether or not the sensed value of
acceleration is equal to or exceeds the predetermined value.
[0029] In some embodiments, the predetermined value is below a
value determined to cause a predetermined degree of injury.
[0030] In some embodiments, the device comprises a power
controller, a memory, a processor, an indicator or another
device.
[0031] In some embodiments, the device comprises a recording means
for recording the value of the sensed parameter.
[0032] In some embodiments, the apparatus includes mounting means
for mounting the apparatus to a protective helmet.
[0033] Advantageously, the apparatus allows head acceleration to be
measured only when it is determined that the sensed acceleration is
sufficient to actually warrant recording the measurement thereby
reducing the electrical power requirements and extending the useful
life of the system when powered by a battery.
[0034] According to another aspect of the present invention, there
is provided an apparatus for recording data indicative of
acceleration of a part of a person's body or other object,
comprising first memory means for receiving acceleration data from
an acceleration sensor, second memory means operatively coupled to
the first memory means for receiving data from the first memory
means, and a data transfer controller for controlling the transfer
of data from the first memory means to the second memory means
based on the acceleration data.
[0035] According to another aspect of the present invention, there
is provided a method of calibrating a data recording unit for
measuring head acceleration, comprising the steps of: (a) providing
a data recording unit mounted to a head protector; (b) mounting the
head protector on a support; (c) subjecting the head protector to a
force or change in pressure; (d) measuring acceleration of the head
protector resulting from the force or change in pressure; (e)
measuring acceleration of the support resulting from the force or
change in pressure; and (f) determining a relationship between the
measured acceleration of the head protector and the support.
[0036] According to another aspect of the present invention, there
is provided a method of determining the value of a parameter
indicative of acceleration of a person's head, comprising the steps
of: acquiring data measured by an acceleration sensor mounted to a
head protector and using a calibration method to determine from the
data the value of said parameter.
[0037] According to another aspect of the present invention, there
is provided a method of monitoring acceleration of a part of a body
of military or service personnel comprising mounting a monitor for
monitoring acceleration to the body part to be monitored.
[0038] Embodiments of the method may include any one or more
additional features disclosed herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Examples of embodiments of the present invention will now be
described with reference to the drawings, in which:
[0040] FIG. 1 shows a front perspective view of a data recording
unit according to an embodiment of the present invention, mounted
to the rear of a military helmet;
[0041] FIG. 2 shows a front perspective view of the data recording
unit of FIG. 1 in more detail;
[0042] FIG. 3 shows a rear perspective view of the data recording
unit shown in FIGS. 1 and 2;
[0043] FIG. 4 shows a semi-transparent view of some of the
circuitry of the data recording unit of FIGS. 1 to 3;
[0044] FIG. 5 shows a front perspective view of the data recording
unit encapsulated in a mold;
[0045] FIG. 6 shows a rear perspective view of a molded cover for
the data recording unit;
[0046] FIG. 7 shows a block diagram of components of a data
recording unit according to an embodiment of the present
invention;
[0047] FIG. 8 shows an example of both unfiltered and filtered head
acceleration traces in the x-direction (front-back) of a forward
facing mannequin towards an explosion at a standoff distance of 3
meters, provided by 8.5 pounds of C4;
[0048] FIG. 9 shows an example of both unfiltered and filtered
x-direction helmet acceleration traces as recorded by a data
recording unit from a forward-facing mannequin during the explosion
of FIG. 8;
[0049] FIG. 10 shows an example of filtered head acceleration
traces for x, y (left-right) and z (up-down) directions, and the
resultant acceleration trace for the same forward-facing mannequin
and explosion of FIGS. 8 and 9;
[0050] FIG. 11 shows examples of x, y and z direction, filtered
acceleration traces and a resultant acceleration trace as measured
by a helmet-mounted data recording unit for the same forward-facing
mannequin and blast event of FIGS. 8 to 10;
[0051] FIG. 12 shows resultant, filtered head acceleration traces
for a forward-facing mannequin during 2.5 pounds, 4.0 pounds, 8.5
pounds and 12.5 pounds of C4 charges at a standoff distance of 3
meters;
[0052] FIG. 13 shows an example of resultant filtered acceleration
traces as measured by a helmet mounted data recording unit for the
forward-facing mannequin of FIG. 12 during the 2.0 pounds, 4.0
pounds, 8.5 pounds and 12.5 pounds C4 charges at a standoff
distance of 3 meters;
[0053] FIG. 14 shows an example of resultant, filtered head
acceleration traces for a mannequin oriented in different
directions with respect to 8.5 pound, C4 charges at a standoff
distance of 3 meters; and
[0054] FIG. 15 shows examples of acceleration traces as measured by
a helmet mounted data recording unit for the mannequin of FIG. 14
at different orientations with respect to the explosive charge.
DETAILED DESCRIPTION
[0055] Referring to FIGS. 1 to 7, a data recording unit 1 according
to an embodiment of the present invention comprises a sensor 3 for
sensing acceleration, and circuitry 5 (FIG. 7) for recording
acceleration data. The unit includes a source 6 of electrical
power, which may comprise one or more battery cells, for example,
cells 6a to 6h, which may be standard "coin" cells. A communication
port 7 may be provided for connection to and/or communication with
an external device. Components of the data recording unit may be
mounted on a circuit card assembly 8 which may be subsequently
encapsulated in an epoxy mold 9 to form an integral unit 11. A cap
13 is provided to cover the front and peripheral edge of the unit
and the unit and cap are mounted on a protective helmet 15, as
shown in FIG. 1. In this embodiment, the rear face 17 of the unit
generally conforms to the shape of the part of the helmet against
which it is mounted. The unit may be designed to be mounted on the
rear part of a helmet, although in other embodiments, the unit may
be mounted on any other part of the helmet. A through hole 19 is
provided through the unit and cap for receiving a mounting bolt or
screw to secure the unit to the helmet shell. The through hole may
be positioned to coincide with the position of an existing through
hole in the helmet, for example, for mounting the internal
suspension system, avoiding the need for making any additional
holes in the helmet which might compromise its protective
performance. In this embodiment, the unit includes a clip 21 which
is adapted to clip under the lower peripheral edge of the helmet to
assist in retaining the unit to the helmet, and may be integrally
formed with the cap. In other embodiments, the clip may be
integrally formed with the epoxy layer or mold, or may comprise a
separate piece. In this embodiment, the cap is provided with
internal projections 23, 25 which register with corresponding
apertures 27, 29 formed in the unit 11 to assist in locating the
cap on the unit and preventing relative movement between the
two.
[0056] In other embodiments, alternative or additional fastening
means may be provided to securely fasten the data recording unit to
the helmet.
[0057] The data recording unit comprises an acceleration sensor,
discrimination circuitry for determining whether or not the
measured acceleration is at or exceeds a predetermined value, and
circuitry responsive to the discrimination circuitry for recording
measured values of acceleration.
[0058] A block diagram of an example of a data recording unit is
shown in FIG. 7. Referring to FIG. 7, the data recording unit 101
includes first, second and third accelerometers 103, 105, 107, each
of which measures acceleration in a single direction which is
orthogonal to the acceleration direction measured by the other two
accelerometers. The accelerometers may be arranged so that they
each lie on a respective one of three mutually orthogonal axes in
which all of the axes meet at a common point, to assist in
resolving the actual direction of acceleration from the
acceleration trace produced by each accelerometer. In this
embodiment, the first accelerometer 103 measures acceleration in
the front-back (designated x) direction, the second accelerometer
105 measures acceleration in the left-right (designated y)
direction, and the third accelerometer 107 measures acceleration in
the up-down (designated z) direction. In some embodiments, the
accelerometers use transducers that produce or generate an
electrical signal in response to sensing acceleration, without the
transducers requiring electrical power to do so, in order to help
reduce power requirements. In some embodiments, the accelerometers
use transducers that exploit the Piezo-electric effect to generate
a charge whose value varies with acceleration and may be
proportional to acceleration, for example.
[0059] A respective band pass filter 109, 111, 113 may be provided
for filtering the signal from each accelerometer 103, 105, 107. A
respective amplifier (not shown) may be provided to amplify each
accelerometer signal, either before or after the band pass filter,
or both. In some embodiments, the amplifiers may be very low power
op-amps to help minimize the amount of power required by the sensor
circuitry. Electrical power for the sensor circuitry is provided by
a suitable power source 115, which may comprise one or more
individual battery cells.
[0060] The data recording unit includes a data processing unit 117
for receiving acceleration signals from the accelerometers 103,
105, 107, and a control or discriminating circuit 119 for
controlling the state of the data processing unit 117 to manage the
power drawn by the unit. In particular, the control circuit 119 is
arranged to control the data processing unit 117 between a first,
inactive state in which the data processing unit is in "sleep" mode
and draws no or little power and is unable to record acceleration
data, and a second state in which the data processing unit is in
"an awake" mode or active state and able to record acceleration
data. In this embodiment, the control circuit 119 comprises a
respective comparator 121, 123, 125 coupled to receive acceleration
signals from a respective accelerometer and for comparing the
magnitude of the acceleration signals with a predetermined value.
In this particular embodiment, one input of each comparator is
coupled to receive a respective accelerometer signal from a
respective band pass filter and another input of each comparator is
coupled to receive the threshold value provided by a suitable
source 127. The output of each comparator is coupled to a suitable
logic device or circuit, for example, an OR gate 129 which is
arranged to output a trigger signal 131 to the data processor unit
117 to cause the data processing unit to change from an asleep
state to an awake state if the acceleration measured by any one of
the accelerometers reaches or exceeds the predetermined threshold
value. A main clock 132 provides clocking signals to the data
processing unit, and, in this embodiment, is an external clock,
although in other embodiments, the clock may be internal of the
CPU. The trigger signal 131 is provided to the main clock 132 to
control operation thereof, as described in more detail below.
[0061] Some embodiments may be adapted to base the determination as
to whether or not to enable the data recording unit to receive and
record acceleration data on any other characteristic of the sensed
acceleration. These may include any one or more of a time
derivative of acceleration, such as the slope of an impulse, or
Fourier frequency component(s) in the waveforms. A derivative
circuit may be provided to monitor the slopes of impulses, or
appropriate circuitry may be provided to perform a Fourier analysis
on the waveform, and to determine whether the resulting values meet
a predetermined criteria. This may allow even earlier detection of
significant events.
[0062] The data processing unit 117 includes first, second and
third analog-to-digital converters 133, 135, 137 for receiving
acceleration signals from a respective accelerometer 103, 105, 107,
a first memory unit 139 for recording digital acceleration data
from each A to D converter 133, 135, 137, and a second memory unit
141 for receiving data from the first memory unit 139. The first
memory unit may comprise a volatile memory, e.g. a random access
memory (RAM) and the second memory unit may comprise a non-volatile
memory, for example, a FLASH memory. The data processing unit 117
may also include a temperature sensor 143 and possibly a fourth
analog to digital converter 145 for receiving an analog signal
indicative of temperature from the temperature sensor and passing a
corresponding digital signal to the first memory unit 139 to be
recorded therein. The data processing unit also includes one or
more interface(s) 147, 149, 151 for communicating and exchanging
signals with one or more external device(s), and an I/O controller
155 for controlling the transfer of data between internal memory of
the data processing unit 117 and external device(s).
[0063] The data recording unit includes an external memory 157 and
a real time clock 159 coupled to a respective interface 147, 149 of
the data processing unit 117 and which are capable of communicating
with its internal memory 139 via the I/O controller 155. The real
time clock provides an indication of real time (e.g. including any
one or more of year, month, day and time, (e.g. hour, and
optionally minute and optionally second) and enables event data to
be time-stamped. Time-stamping enables the event to be correlated
with other information or record(s) of an event. One of the
interfaces of the data processing unit 151 includes a general
interface port adapted for releasable connection to a peripheral
device, such as a host computer. In the present embodiment, the
interface 155 is an RS-232 interface, although in other
embodiments, the interface 151 may comprise any other suitable
interface, for example, a USB.
[0064] The data recording unit also includes a power source 161 for
providing electrical power to the data processing unit. Regulator
and power management modules 163, 164 are provided for regulating
power to the data processing unit and the acceleration sensor
circuitry, respectively. In this particular embodiment, the
regulator and power management modules 163, 164 are coupled to an
interface 165 (e.g. a digital I/O interface) of the data processing
unit. In some embodiments, the regulator and power management
modules 163, 164 may each comprise a switch, which switchably
couples/decouples the power sources to/from the data processing
unit 117 and sensor circuitry in response to a control signal from
the interface 165. Each power management module may be controlled
independently of the other, or may be controlled together, for
example using the same control signal. The switch may enable the
respective power sources to be completely disconnected from their
associated circuitry (load), so that substantially no power is
drawn when the unit is in storage, for example.
Power Management
[0065] Embodiments of the data recording unit are designed to
operate continuously for extended periods of time using stored
electrical energy from a battery, for example, without any
requirement for recharging, and the associated infrastructure, or
replacing the battery. Some embodiments are designed to operate
continuously for the duration of a typical "tour of duty" for
military personnel which may last for up to six months, or more. In
normal operation, i.e. in the absence of exposure to a violent
event, components which are required to record data are maintained
in an "off" or inactive state where little or no power is drawn by
those components. In this state, only the acceleration sensors,
their associated circuitry (i.e. op-amps and band pass filters) and
the control circuit 119 are active. In some embodiment, the
comparators 121, 123, 125 of the control circuit are selected to
draw little power.
[0066] The earliest stages of a blast event are critical in
determining potential injury as this is when the maximum
acceleration(s) occur. Typically, a subject is exposed to maximum
acceleration values in the first few milliseconds of a blast event,
for example, the first one or two milliseconds. The largest
acceleration impulses are usually the first to arrive, and these
initial impulses may only last one or two milliseconds. An example
of the acceleration of the head of an anthropomorphic mannequin
measured during a blast event is shown in FIG. 8. In this example,
the mannequin's head is facing forwards towards the blast which is
generated by a charge containing 8.5 pounds of C4 at a distance
from the mannequin of 3 meters. The graph shows two x-direction
(front-back) acceleration traces, one being an unfiltered trace and
the other being filtered by a band pass filter which cuts off
frequencies above about 1,650 Hertz. As can be seen, the peak
acceleration occurs at about 0.5 milliseconds or 500 microseconds
after the point at which the acceleration first begins to change.
This peak acceleration only lasts for about 1 millisecond. FIG. 9
shows an example of filtered and unfiltered x-direction
acceleration traces from the same blast event as that of FIG. 8, as
measured by a data recording unit mounted to a helmet fitted on and
secured to the mannequin's head. Again, the peak acceleration
occurs within the first 500 microseconds and has a duration of
about 1 millisecond. As described below, embodiments of the data
recording unit are capable of switching from an inactive to an
active state in response to acceleration measured by the sensors in
a sufficiently short time to enable at least part of the earliest
acceleration impulse, which may be the strongest, to be
recorded.
[0067] When an event of interest occurs, such as an impact event or
a blast event, as determined by the acceleration measured by one or
more accelerometers reaching or exceeding the threshold value, a
trigger signal 131 is output from the control circuit 119 and
causes the data processing unit 117 to turn on and start recording.
The threshold value may be set at about 50 gs, for example, or any
other suitable value. In some embodiments, the data processing unit
is triggered to start by an acceleration from any one or more of
the acceleration sensors which exceeds a pre-set threshold. In some
embodiments, the acceleration trigger threshold is set slightly
below levels where injury is expected to occur. Advantageously,
this provides sufficient time for the data processing unit to start
up and capture the relevant acceleration waveforms. The data
processing unit may employ a rapid start up system to jump from a
deep sleep mode to full execution mode in a relatively short time,
for example, about 100 microseconds.
[0068] Although in some embodiments, activation of the data
processing unit may be controlled by switchably connecting the data
processing unit to the power source, other embodiments of the data
recording unit use one or more other techniques for rapid startup,
an example of which controls startup through the main CPU clock. In
one embodiment, the frequency of the main clock 132 can be varied
between one or more operating frequencies, for example, 5.5 MHz (or
any other suitable frequency) and a frequency of 0 Hz, for example.
This may be implemented by switching the clock between ON and OFF
states, for example in response to the trigger signal 131 from the
control circuit 119. In one embodiment, the clock may comprise a
solid state oscillator rather than a crystal oscillator to enable
the clock to start quickly, for example in one or two clock cycles,
which for a clock frequency of 5.5 MHz would take about 0.2 to 0.4
microseconds. When the main clock is in the OFF state, the CPU
effectively sees that the clock has stopped, ceases to execute the
current instruction and holds its current state. Although power to
the data processing unit is available, power is conserved when the
data processing unit is in the "inactive" state, and execution of
instructions is suspended.
[0069] On receiving a trigger or control signal from the control
circuit 119, the clock turns ON and provides a clocking signal to
the data processing unit which, in response, becomes active and
begins to execute instructions. Advantageously, controlling the
data processing unit between active and inactive states using the
main clock rather than switchably ON/OFF coupling the data
processing unit to the power source reduces the amount of power
required to activate the data processing unit.
[0070] In some embodiments, power for activating or driving the
main CPU clock is provided both by the control signal 131 and the
data processing unit. In a specific embodiment, the trigger signal
lasts for a sufficient time to power the clock on until power for
the clock can be supplied by the data processing unit. Any suitable
means may be provided to maintain the control or trigger signal 131
at an appropriate level to provide power to the clock for a
sufficient period of time until the data processing unit has
started and can provide power to the clock. The means may for
example be provided by an appropriate filter. In some embodiments,
once the data processing unit receives an appropriate clocking
signal from the main clock, the data processing unit executes a
relatively short "house-keeping" program, which may include an
instruction to provide power to the main clock. Once active, the
data processing unit is able to receive and convert analog
accelerometer signals to digital signals and record the digital
signals.
[0071] In some embodiments, the data recording unit is adapted to
record data for a predetermined length of time, for example, any
time from about 1 to 15 milliseconds or any other suitable time,
e.g. a length of time that is sufficient to record the maximum
acceleration only or the latter plus a predetermined additional
time. The data processing unit may also be adapted to maintain
itself in the active state for a predetermined period of time and
then cause itself to change to an inactive state to conserve power.
This may be implemented, for example, by configuring the data
processing unit to turn off power to the clock a predetermined
period of time after the CPU becomes active. Once in the inactive
state, the data processing unit remains in that state until another
acceleration event causes the data processing unit to change to the
active state.
[0072] In the present embodiment, the analog waveform from each
sensor is converted by a respective A to D converter to a digital
signal and stored in the first, volatile memory unit 139. The A to
D converters may be adapted to operate at any desired sampling
rate, for example, 10 kHz or any other suitable frequency. The band
pass filters may be configured to ensure that the signals to the A
to D converters do not fluctuate faster than half the A to D
sampling frequency to reduce frequency and amplitude errors in the
digitized waveforms. Each of the first, second and third A to D
converters may be adapted to convert simultaneously so that the
direction of each instantaneous acceleration can be determined
efficiently. When an event occurs in which the acceleration is
sufficient to activate the data recorder, acceleration data is
received by the first memory unit and recorded therein with the
time of the event, as provided by the real time clock 159, and the
temperature from the temperature sensor 143. After capturing an
event in the first memory unit 139, the data processing unit may be
adapted to make a decision either to store or not to store the data
in non-volatile memory, based, for example, on the measured
acceleration. Such a determination may be made based on whether a
peak acceleration exceeds an injury threshold or not. The data
recording unit may be provided with one or a plurality of such
threshold(s). The threshold(s) may be set by an external computer,
via a suitable interface, for example, interface 151. In one
embodiment, a threshold may be set at 100 gs, for example, or any
other suitable value.
[0073] If the decision by the data processing unit is to retain the
data stored in the volatile memory 139, data is then transferred
from the volatile memory to the non-volatile memory unit 141, where
the data may be stored indefinitely without requiring electrical
power. Once the data has been transferred from the first to the
second memory unit, the data processing unit shuts itself down,
entering a "sleep" state, and waits for the next event. If the data
processing unit decides not to keep the event data, the data
processing unit shuts itself down without transferring the event
data to non-volatile memory, resulting in the loss of the data
recorded in the volatile memory 139.
[0074] As described above, the data recording unit may be adapted
to enable electrical power to one or more of the acceleration
sensors and/or the data processing unit to be turned on or off to
extend battery life. This feature may be used to prolong
battery-shelf-life so that the unit can be activated only when it
is brought into service rather than during periods of storage or
non-use. For this purpose, the data recording unit may include a
switch which may be manually accessible on the device or a switch
(e.g. power management module 163, 164) accessible via a
communications port or interface, for example interface 151. In
this latter case, an external control signal may cause the
switching module 163, 164 to change state from OFF to ON and the
switching module may be adapted to maintain itself in the ON-state
thereafter without further application of the control signal.
Electrical power to the unit may be switched off in a similar
manner.
[0075] Electrical power may be provided to the data recording unit
other than via the batteries to enable the data processing unit to
be turned on and data downloaded from the internal non-volatile
memory 141 and/or the external memory 157. Advantageously, this
feature allows data to be retrieved in the event that the batteries
no longer have sufficient energy to activate the unit for this
purpose.
Memory Management
[0076] As described above, in the present embodiment, memory
associated with the data recording unit includes a first memory
unit 139 for receiving and recording data from the A to D
converters, a second memory unit 141 for receiving and storing data
from the first memory unit, and an external memory unit 157. In
some embodiments, the first memory unit comprises a random access
memory to capture and store high speed samples from the A to D
converters and to keep the data until a decision has been made as
to whether to save it. To reduce power consumption, data which is
to be saved is transferred to the second, non-volatile memory unit.
The second memory unit 141 may have the capacity to store
simultaneously event data from a number of separate events. In some
embodiments, data stored in the second memory unit may be
transferred to the external memory unit 157. In some embodiments,
data from a number of separate events may be transferred from the
second memory unit 141 to the external memory unit 157 in a single
or the same write operation to reduce the power which would
otherwise be required if data from each event is transferred in
separate, discrete write operations. In some embodiments, the data
processing unit is adapted to control the transfer of data from the
second memory unit to the external memory unit once a predetermined
number of events have been recorded in the second memory unit. In
one embodiment, the data processing unit may be arranged to
transfer data only when more than three, for example, ten events
have been accumulated and to transfer those (ten) events in a
single write operation. In other embodiments, the number of
accumulated events prior to transfer may be any other number and
the number of events transferred in a single write operation may
also be any other number, and not necessarily the same number as
the number of accumulated events. Preferably event data for more
than one event is transferred in a single write operation.
[0077] In some embodiments, the non-volatile memory comprises a
solid-state memory to withstand the high forces experienced by the
data recording unit. The amount of memory may be limited to
conserve electrical power, reduce size and save weight. The
non-volatile memory of the data processing unit may comprise a
flash memory, for example, an electrically erasable programmable
read-only memory (EEPROM), and may be used to store firmware and
accumulate data from a plurality of events before the data is
archived to the external memory. The external memory may also
comprise a solid state flash memory.
[0078] In some embodiments, other data may be stored in one or more
of the available memories. This may include data which is specific
to the data recording unit to enable the data recording unit to
operate and/or recorded data to be processed. The data may include
offset value(s) for the acceleration sensor(s). For example, a
sensor may provide a non-zero output in the absence of any
acceleration. Offset values may be used by the control circuit 119
to modify/correct the threshold value that controls activation of
the data processing unit, and/or to modify/correct threshold values
used to determine whether to keep the recorded data or not. The
values may include multiplication factor(s) resulting from any
signal amplifiers, or other conditioning. The data may be available
to be output to an external device via a suitable interface for
subsequent use, which may include correcting/adjusting recorded
data for analysis and/or other processing. Storing such values in
or with the unit is particularly convenient, as it obviates the
need for the values to be stored elsewhere, for example in a
central database, their associated input thereto, which may be
prone to error, and their maintenance therein.
Sensors
[0079] In addition to acceleration sensors, the data recording unit
may include a temperature sensor. The temperature sensor may be
included in the data processing unit or may be separate therefrom.
Since the accelerometer sensors may exhibit some temperature
dependence, providing a temperature sensor enables temperature
compensation to be performed on the data to improve accuracy of the
measurement, if required.
[0080] Embodiments of the data recorder may include a communication
port for enabling data to be downloaded to an external device. The
port may be one which requires a physical wireline connection. In
some embodiments, the data recorder may include a wireless
interface for communicating with an external device to enable, for
example, data to be downloaded using a wireless connection. In some
embodiments, the protocol used for transferring data may enable
secure data transfer over short ranges with efficient, low power
operation. The protocol may be based on the IEEE 802.15.4 Standard
for the physical and media access control layer, an example of
which is known as ZIGBEE. The protocol may also allow data to be
downloaded from a number of separate data recording units.
[0081] Embodiments of the data recording unit may include an
optional indicator, which may comprise a visual indicator such as a
red or green light or both to indicate if power to the unit is
turned on, thereby confirming that the unit is ready to record
events.
[0082] FIG. 10 shows an example of filtered acceleration traces for
the x, y and z directions measured by accelerometers mounted in the
head of a mannequin together with the resultant acceleration trace
derived from the x, y and z direction acceleration traces. The
measurements were made during the same blast event of FIGS. 8 and
9, i.e. with the mannequin's face facing forward towards an 8.5
pound C4 charge at a distance of 3.0 meters. As can be seen, the
peak of the resultant acceleration experienced by the mannequin's
head occurs within the first 1 or 2 milliseconds of the blast.
[0083] FIG. 11 shows filtered acceleration traces in the x, y and z
directions as measured by an embodiment of a data recording unit
mounted to a helmet and worn by and secured to the mannequin's head
for the same blast event as FIGS. 8 to 10, together with the
resultant acceleration trace derived from each of the measured x, y
and z acceleration traces. Again, the peak acceleration or
accelerations of the helmet occur within the first one or two
milliseconds of the blast. The magnitude of the peak acceleration
of the helmet is higher than the peak acceleration of the
mannequin's head. This is at least partly due to the mechanical
decoupling between the head and helmet provided by the resilient or
flexible helmet suspension or cushioning system, which allows
relative movement between the head and helmet, and the difference
in mass between the head and helmet. In practice, for head
acceleration monitoring, acceleration may be measured by helmet
mounted accelerometers only. In order to derive head acceleration
from a helmet mounted data recording unit, calibration tests may be
performed in order to determine a relationship describing or
defining the correlation between helmet and head accelerations.
Such a determination may be made by performing a number of
measurements with the head/helmet combination subjected to
different blast strengths, which may be varied, for example, by
either changing the strength of the blast or the distance between
the explosive and the mannequin.
[0084] FIGS. 12 and 13 show resultant acceleration traces for head
and helmet accelerations, respectively, measured for four blast
events using different quantities of explosive at the same standoff
distance of 3 meters. In determining the correlation between head
and helmet accelerations, the peak (or other value of) acceleration
may be obtained from each acceleration trace and the ratio between
peak head and peak helmet accelerations may be determined. A
mathematical expression may then be fitted to the data, thereby
establishing a relationship between head and helmet accelerations.
This relationship may then be used when analyzing data from the
data recording unit to determine head acceleration. This data may
be used to determine a level of injury that may have been caused by
the blast event. For example, previous studies carried out by the
applicant, in which anthropomorphic mannequins have been subjected
to the blast of high explosives in free field (no obstacles)
conditions, have indicated that the blast-induced head acceleration
injury threshold corresponds to a peak resultant head acceleration
of the order of 450 gs.
[0085] The inventors have found that both head and helmet
acceleration depend on the orientation of the head/helmet
combination relative to the source of the blast. In addition, the
inventors have found that the ratio between head acceleration and
helmet acceleration may also depend on the orientation of the
head/helmet combination relative to the source of the explosion.
FIG. 14 shows examples of resultant head acceleration traces
measured for four different mannequin orientations: (1) the front
of the mannequin faces the explosive source; (2) the back and side
of the mannequin are directed towards the explosive source, with a
line extending between front and back of the mannequin at
45.degree. to the source; (3) the side of the mannequin is directed
towards the explosive source; and (4) the back of the mannequin is
directed towards the explosive source. As can be seen from the
traces, the peak acceleration varies depending on the orientation,
with the highest peak acceleration values resulting from the side
and 45.degree. orientations and the lowest peak acceleration values
resulting from the back orientation.
[0086] FIG. 15 shows resultant acceleration traces measured by a
helmet mounted data recording unit for the same orientations and
blast events of FIG. 14. As can be seen, the highest acceleration
value results from a side orientation, the second highest
acceleration results from the back orientation, the third highest
results from front orientation and the lowest acceleration peak
results from the 45.degree. orientation. This shows that the ratio
between head and helmet acceleration varies depending on the
orientation of the head relative to the explosive source. The
relationship between head and helmet acceleration may be determined
for any number of different orientations and subsequently used to
determine head acceleration from data recorded by the helmet
mounted data recording unit. For example, the acceleration traces
measured by the accelerometers of the data recording unit provide
the direction of the blast relative to the head/helmet combination
from which the orientation of the helmet relative to the explosive
source can be determined. The orientation value can then be used to
look up a value of the ratio or other relationship between head and
helmet acceleration and the ratio or other relationship then used
to determine head acceleration from the value of acceleration
measured by the data recording unit. The determined head
acceleration value may then be used to determine whether or not an
injury has occurred and possibly the level of injury.
[0087] In other embodiments and aspects of the invention, any
feature disclosed herein may be omitted altogether or substituted
by another feature which may or may not be an equivalent or variant
thereof. For example, in some embodiments, the z-direction
accelerometer may be omitted. This may be appropriate if the
azimuthal direction of acceleration (i.e. the direction in the
horizontal plane) only is of interest.
[0088] Embodiments of the data recorder may be mounted on any
object. For example, it may be mounted on a vehicle or a stationary
object, or on any article of apparel to be worn by a person.
[0089] Embodiments of the data recorder may be capable of measuring
accelerations having values of at least 1,500 gs, for example,
5,000, 10,000 or 15,000 gs or more.
[0090] Other aspects and embodiments of the invention comprise any
feature disclosed herein in combination with any one or more other
feature disclosed herein or a generic or specific equivalent or
variant thereof.
[0091] Any embodiment may comprise sensor means for measuring
rotational motion, for example, rotational acceleration. The sensor
means may comprise a plurality of spaced apart sensors (e.g.
accelerometers) located at different positions either within a data
recording unit, or one or more sensors may be separate from the
unit and mounted on the object to be monitored, for example, on a
head protector.
[0092] The data recording unit may record data from the rotational
sensor(s). Recording and storing the data may be performed using
the same or similar methodology to that disclosed herein in
relation to the axial acceleration data.
[0093] Numerous modifications to the embodiments described above
will be apparent to those skilled in the art.
* * * * *