U.S. patent application number 11/791208 was filed with the patent office on 2008-02-21 for electric field sensing device.
Invention is credited to Stephen Christopher Kent, Paul Benjamin Mallinson, Brian Keith Russell, Christopher Michael Solomon.
Application Number | 20080042835 11/791208 |
Document ID | / |
Family ID | 36407398 |
Filed Date | 2008-02-21 |
United States Patent
Application |
20080042835 |
Kind Code |
A1 |
Russell; Brian Keith ; et
al. |
February 21, 2008 |
Electric Field Sensing Device
Abstract
A sensing system is disclosed that uses at least one conductive
plate and associated electronic circuitry to provide an output that
is indicative of an object's position in relation to the at least
one conductive plate. The sensing system is provided with a high
impedance drive signal that varies as a result of the location of
an object relative to the at least one conductive plate. The
electronic circuitry receives a high impedance drive signal value
as an input and a processor uses the value to calculate a digital
output indicative of the object's position. The high impedance
drive signal value is monitored over time enabling the objects
position, displacement, pressure, movement, impact and energy to be
determined. This data is output to a display and may also be
transmitted to a person located remotely from the object being
monitored.
Inventors: |
Russell; Brian Keith;
(Auckland, NZ) ; Mallinson; Paul Benjamin;
(Auckland, NZ) ; Kent; Stephen Christopher;
(Auckland, NZ) ; Solomon; Christopher Michael;
(Auckland, NZ) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Family ID: |
36407398 |
Appl. No.: |
11/791208 |
Filed: |
November 22, 2005 |
PCT Filed: |
November 22, 2005 |
PCT NO: |
PCT/NZ05/00309 |
371 Date: |
November 2, 2007 |
Current U.S.
Class: |
340/561 |
Current CPC
Class: |
A61B 5/6892 20130101;
A61B 5/4818 20130101; A61B 5/447 20130101; A61B 5/1038 20130101;
G01B 7/003 20130101 |
Class at
Publication: |
340/561 |
International
Class: |
G01R 29/08 20060101
G01R029/08; G08B 21/18 20060101 G08B021/18 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2004 |
NZ |
536762 |
Claims
1-70. (canceled)
71. An electric field sensing system used to detect movement,
position and pressure of an object comprising: at least one
conductive plate, a reference input signal, a high impedance drive
signal input generated from said reference input signal and
connected to said at least one conductive plate producing an
electric field around said at least one conductive plate, a
processing circuit that synchronously detects and receives as an
input said reference input signal and said high impedance drive
signal and applies at least one algorithm to measure any variations
in said signals, and generates a digital signal output, and wherein
a position of said object in said electric field determines a value
of said high impedance drive signal and said processing circuit
provides said digital signal output indicative of said object's
position or movement in relation to said at least one conductive
plate.
72. The electric field sensing system according to claim 71 wherein
said high impedance drive signal is also a sense signal.
73. The electric field sensing system according to claim 71 wherein
said processing circuit uses said values in said high impedance
drive signal input to calculate at least one of displacement,
position and pressure caused by said object.
74. The electric field sensing system according to claim 71 wherein
said processing circuit uses said values in said high impedance
drive signal input over time to calculate at least one of a
movement, impact or energy caused by said object.
75. The electric field sensing system according to claim 71 wherein
said digital signal output is input to a display system
incorporating an audible alarm.
76. The electric field sensing system according to claim 75 wherein
said digital signal output is input to a display system.
77. The electric field sensing system according to claim 75 wherein
said digital signal output is input to an audible alarm system.
78. The electric field sensing system according to claim 71 wherein
said digital signal output is transmitted from said electric field
sensing system via at least one of a radio, mobile communications
network or the internet to a person located remotely from a user of
said electric field sensing system enabling said remotely located
person to receive on an electronic device said digital data in
real-time.
79. The electric filed sensing system according to claim 78 wherein
said electronic device includes at least one of a radio, mobile
telephone, personal digital assistance, internet connected device
and computer.
80. The electric field sensing system according to claim 71 wherein
said at least one conductive plate is constructed from a solid
material.
81. The electric field sensing system according to claim 80 wherein
said solid material is a copper plate.
82. The electric field sensing system according to claim 80 wherein
said solid material is a carbon impregnated polyethylene pad.
83. The electric field sensing system according to claim 71 wherein
said at least one conductive plate is coated with a conductive ink
such as silver.
84. The electric field sensing system according to claim 71 wherein
said at least one conductive plate is coated with a conductive ink
such as carbon.
85. The electric field sensing system according to claim 71 wherein
said at least one conductive plate is constructed from at least one
of a flexible and stretchable material.
86. The electric field sensing system according to claim 85 wherein
said flexible material is a conductive membrane.
87. The electric field sensing system according to claim 85 wherein
said flexible material is a plurality of conductive fibres.
88. The electric field sensing system according to claim 85 wherein
said flexible material is adhered to or sewn to a garment or other
section of flexible type of material which, in use, does not
inhibit the ability of a user to perform a task.
89. A multilayered electric field sensing system used to detect at
least one of movement, position and pressure of an object
comprising: a plurality of electrically coupled conductive plates
forming a layered construction, a plurality of compressible
insulating members interleaved with said conductive plates, a
reference input signal, a high impedance drive signal input
generated from said reference input signal and connected to at
least one of said conductive plates producing an electric field
between said layered construction, a processing circuit that
synchronously detects and receives as an input said reference input
signal and said high impedance drive signal and applies at least
one algorithm to measure any variations in said signals, and
generates a digital signal output, and wherein a position of said
object in said electric field determines a value of said high
impedance drive signal and said processing circuit provides said
digital signal output indicative of a position of said object or
movement in relation to said plurality of electrically coupled
conductive plates.
90. The multilayered electric field sensing system according to
claim 89 wherein said high impedance drive signal is a sense
signal.
91. The multilayered electric field sensing system according to
claim 89 wherein said conductive plate layered construction is
formed by at least an upper conductive plate, a lower conducive
plate and a third conductive plate therebetween.
92. The multilayered electric field sensing system according to
claim 91 wherein said upper and lower conductive plates are
electrically connected to ground and said third conductive plate is
connected to said high impedance drive signal.
93. The multilayered electric field sensing system according to
claim 89 wherein said conductive plate layered construction is
formed by a plurality of conductive plates, said plurality of
conductive plates being an odd number and there are n odd numbered
conductive plates and m even numbered conductive plates.
94. The multilayered electric field sensing system according to
claim 93 wherein each of said n odd numbered conductive plates are
electrically connected to ground and each of said m even numbered
conductive plates are connected to said high impedance drive
signal.
95. The multilayered electric field sensing system according to
claim 89 wherein said plurality of compressible insulating members
are constructed from a compressible medium such as high density
foam.
96. The multilayered electric field sensing system according to
claim 95 wherein said plurality of compressible insulating members
are constructed from a compressible medium such as an elastomer
foam material.
97. The multilayered electric field sensing system according to
claim 89 wherein said processing circuit uses said changes in said
high impedance drive signal inputs to calculate at least one of a
displacement, position, pressure impact and energy caused by said
object.
98. The multilayered electric field sensing system according to
claim 89 wherein said digital signal output is input to a display
system incorporating an audible alarm.
99. The multilayered electric field sensing system according to
claim 98 wherein said digital signal output is input to a display
system.
100. The multilayered electric field sensing system according to
claim 98 wherein said digital signal output is input to an audible
alarm system.
101. The multilayered electric field sensing system according to
claim 89 wherein said digital signal output is transmitted from
said electric field sensing system via at least one of a radio,
mobile communications network and the internet to a person located
remotely from a user of said electric field sensing system enabling
said remotely located person to receive on an electronic device
said digital data in real-time.
102. The multilayered electric field sensing system according to
claim 101 wherein said electronic device includes at least one of a
radio, mobile telephone, personal digital assistance, internet
connected device and computer.
103. The multilayered electric field sensing system according to
claim 89 wherein said at least one conductive plate is constructed
from a solid material.
104. The multilayered electric field sensing system according to
claim 103 wherein said solid material is a copper plate.
105. The multilayered electric field sensing system according to
claim 103 wherein said solid material is a carbon impregnated
polyethylene pad.
106. The multilayered electric field sensing system according to
claim 89 wherein said at least one conductive plate is coated with
a conductive ink such as silver.
107. The multilayered electric field sensing system according to
claim 89 wherein said at least one conductive plate is coated with
a conductive ink such as carbon.
108. The multilayered electric field sensing system according to
claim 89 wherein said at least one conductive plate is constructed
from at least one of a flexible and stretchable material.
109. The multilayered electric field sensing system according to
claim 108 wherein said flexible material is a conductive
membrane.
110. The multilayered electric field sensing system according to
claim 108 wherein said flexible material is a plurality of
conductive fibres.
111. The multilayered electric field sensing system according to
claim 108 wherein said flexible material is adhered to or sewn to a
garment or other section of flexible type of material which, in
use, does not inhibit the ability of a user to perform a task.
112. A double layer electric field sensing system used to detect
movement, position and pressure of an object comprising: an
electronic circuit used to generate a multiplexed high impedance
signal and a multiplexed low impedance inverted drive signal, a
first conductive plate energised by said multiplexed high impedance
drive signal, a second conductive plate energised by said
multiplexed low impedance inverted drive signal, a compressible
insulating layer located between said first and second conductive
plates, a processing circuit that obtains as an input said
multiplexed high impedance drive signal, calculates variations in
said multiplexed high impedance drive signal and generates a
digital signal output, and wherein said first conductive plate is
electrically orthogonal to said second conductive plate generating
a matrix of electrically coupled cells whereby a position of said
object determines a number of coupling interactions between said
electrically coupled cells and said processing circuit measures
said positions and provides said digital signal output indicative
of said object position.
113. The double layer electric field sensing system according to
claim 112 wherein said high impedance drive signal is also a sense
signal.
114. The double layer electric field sensing system according to
claim 112 wherein said compressible insulation layer is a
compressible medium such as high density foam.
115. The double layer electric field sensing system according to
claim 112 wherein said compressible insulation layer is a
compressible medium such as an elastomer foam material.
116. The double layer electric field sensing system according to
claim 112 wherein said processing circuit uses said changes in said
multiplexed high impedance drive signal inputs to calculate at
least one of displacement, position, pressure, movement, impact or
energy caused by said conductive body.
117. The double layer electric field sensing system according to
claim 112 wherein said digital signal output is input to a display
system incorporating an audible alarm.
118. The double layer electric field sensing system according to
claim 112 wherein said digital signal output is input to a display
system.
119. The double layer electric field sensing system according to
claim 112 wherein said digital signal output is input to an audible
alarm system.
120. The double layer electric field sensing system according to
claim 112 wherein said digital signal output is transmitted from
said electric field sensing system via at least one of a radio,
mobile communications network and the internet to a person located
remotely from a user of said electric field sensing system enabling
said remotely located person to receive on an electronic device
said digital data in real-time.
121. The double layer electric field sensing system according to
claim 120 wherein said electronic device includes at least one of a
radio, mobile telephone, personal digital assistance, internet
connected device and computer.
122. The double layer electric field sensing system according to
claim 112 wherein said at least one conductive plate is constructed
from a solid material.
123. The double layer electric field sensing system according to
claim 122 wherein said solid material is a copper plate.
124. The double layer electric field sensing system according to
claim 122 wherein said solid material is a carbon impregnated
polyethylene pad.
125. The double layer electric field sensing system according to
claim 112 wherein said at least one conductive plate is coated with
a conductive ink such as silver.
126. The double layer electric field sensing system according to
claim 112 wherein said at least one conductive plate is coated with
a conductive ink such as carbon.
127. The double layer electric field sensing system according to
claim 112 wherein said at least one conductive plate is constructed
from at least one of a flexible or stretchable material.
128. The double layer electric field sensing system according to
claim 127 wherein said flexible material is a conductive
membrane.
129. The double layer electric field sensing system according to
claim 127 wherein said flexible material is a plurality of
conductive fibres.
130. The double layer electric field sensing system according to
claim 127 wherein said flexible material is adhered to or sewn to a
garment or other section of flexible type of material which, in
use, does not inhibit the ability of a user to perform a task.
131. The method of monitoring the performance of a user
incorporating any one of the conductive plate arrangements and
associated sensing system circuit according to claims 71, 89 or 112
comprising the steps of: placing said conductive plate arrangement
and said associated sensing system in close proximity to said user,
measuring changes in electrical characteristics between said
conductive plates using said associated sensing system when said
user moves in relation to said conductive plates, applying a
plurality of algorithms to said measured changes to calculate at
least one of movement parameters of displacement, force, shear
force and pressure, converting said movement parameters into a
digital signal output, and outputting said movement parameters to
said user.
132. The method of monitoring performance according to claim 131
wherein said step of measuring said changes in electrical
characteristics includes measuring fluctuations in a high impedance
drive signal applied to said conductive plate arrangement as a
result of said user's movement in relation to said conductive plate
arrangement.
133. The method of monitoring performance according to claim 131
wherein said step of outputting said movement parameters includes
inputting said digital signal output from said sensing system to a
display system incorporating an audible alarm.
134. The method of monitoring performance according to claim 133
wherein said step of outputting said movement parameters includes
inputting said digital signal output from said sensing system to a
display system.
135. The method of monitoring performance according to claim 133
wherein said step of outputting said movement parameters includes
inputting said digital signal output from said sensing system to an
audible alarm.
136. The method of monitoring performance according to claim 133
wherein said step of outputting said movement parameters includes
transmitting said digital signal output from said sensing system to
a remote electronic device.
Description
FIELD OF INVENTION
[0001] This invention relates to a contactless monitor and
particularly to a conductive surface coupling an electric field
between conductive bodies that provides a system capable of
detecting movement, position and pressure of a body.
SUMMARY OF THE PRIOR ART
[0002] A number of systems are known in the art for providing a
contactless monitor or alarm condition responsive to the activity
of humans or animals. More commonly known forms of monitor or alarm
are for use in a hospital environment or home which responds to
respiration and apnea and more particularly its application to
preventing apnea in small infants and premature babies. Respiration
monitors of this type are used in hospitals providing a visible
and/or aural indication of when a patient develops abnormal
breathing patterns or has stopped breathing.
[0003] In U.S. Pat. No. 4,033,332 to Cavitron Corporation, a
contactless activity and respiration monitor is disclosed which
includes a resilient, capacitive pad (a mattress) or a pad used as
a mattress, having a capacitor therein which is responsive to the
activity or respiration of a patient lying on the pad. Coupled to
the capacitor pad is electronic sensing circuitry and an alarm unit
that provides an indication and/or alarm when abnormal respiratory
rates change or when apnea occurs. This monitor is capable of
responding to and distinguishing between small movements of the
patient being monitored due to breathing, including apnea, and
larger movements of the patient that would naturally cause the
breathing rate of a patient to increase and result in false alarms
being indicated. This monitor uses three layers of conductive wire
mesh electrodes having foam between each layer. The sandwiched
construction is then placed either within or under an infant's
mattress, for example. When an infant is lying on the pad the
relative motion between electrodes caused by breathing effectively
changes the capacitance between the electrodes. The change in
capacitance is sensed by the electronic circuitry and if the
detected level falls outside a predetermined threshold level a
visual and/or aural alarm is used to alert medical staff. The
system uses rudimentary integrator and filtering circuits to detect
long term changes of capacitance caused by increased breathing rate
or apnea. One of the disadvantages of this type of system is that
it cannot measure static parameters such as distance, force or
pressure, it is susceptible to electrostatic pick up at mains line
frequency, can only measure event changes and not constant values
such as would occur when a person sits still. A further
disadvantage is that the electronic circuitry responds to
electrostatic charges generated by movement of the pad cable,
unless non-micro phonic cabling was used and as such the circuit
requires a drive conductor and a receive conductor.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a
contactless monitoring system which goes some way to overcoming the
abovementioned disadvantages in the prior art or which will at
least provide the industry with a useful choice.
[0005] Accordingly, in a first aspect the invention consists in an
electric field sensing system used to detect movement, position and
pressure of an object comprising:
[0006] at least one conductive plate,
[0007] a reference input signal,
[0008] a high impedance drive signal input generated from said
reference input signal and connected to said at least one
conductive plate producing an electric field around said at least
one conductive plate,
[0009] a processing circuit that receives as an input said
reference input signal and said high impedance drive signal, and
generates a digital signal output, and
[0010] wherein a position of said object in said electric field
determines a value of said high impedance drive signal and said
processing circuit provides said digital signal output indicative
of said object's position in relation to said at least one
conductive plate.
[0011] Preferably, said high impedance drive signal is also a sense
signal.
[0012] Preferably, said processing circuit uses said values in said
high impedance drive signal input to calculate at least one of
displacement, position and pressure caused by said object.
[0013] Preferably, said processing circuit uses said values in said
high impedance drive signal input over time to calculate at least
one of movement, impact or energy caused by said object.
[0014] Preferably, said digital signal output is input to a display
system incorporating an audible alarm.
[0015] Alternatively, said digital signal output is input to a
display system.
[0016] Alternatively, said digital signal output is input to an
audible alarm system.
[0017] Preferably, said digital signal output is transmitted from
said electric field sensing system via at least one of a radio,
mobile communications network and the internet to a person located
remotely from a user of said electric field sensing system enabling
said remotely located person to receive on an electronic device
said digital data in real-time.
[0018] Preferably, said electronic device includes at least one of
a radio, mobile telephone, personal digital assistance, internet
connection device and computer.
[0019] Preferably, said at least one conductive plate is
constructed from a solid material.
[0020] Alternatively, said at least one conductive plate is
constructed from at least one of a flexible and stretchable
material.
[0021] Preferably, said solid material is a copper plate.
[0022] Alternatively, said solid material is a carbon impregnated
polyethylene pad.
[0023] Preferably, said at least one conductive plate is coated
with a conductive ink such as silver.
[0024] Alternatively, said at least one conductive plate is coated
with a conductive ink such as carbon.
[0025] Preferably, said flexible material is a conductive
membrane.
[0026] Alternatively, said flexible material is a plurality of
conductive fibres.
[0027] Preferably, said flexible material is adhered to or sewn to
a garment or other section of flexible type of material which, in
use, does not inhibit the ability of a user to perform a task.
[0028] In a second aspect the invention consists in a multilayered
electric field sensing system used to detect at least one of
movement, position and pressure of an object comprising:
[0029] a plurality of electrically coupled conductive plates
forming a layered construction,
[0030] a plurality of compressible insulating members interleaved
with said conductive plates,
[0031] a reference input signal,
[0032] a high impedance drive signal input generated from said
reference input signal and connected to at least one of said
conductive plates producing an electric field between said layered
construction,
[0033] a processing circuit that receives as an input said
reference input signal and said high impedance drive signal, and
generates a digital signal output, and
[0034] wherein a position of said object in said electric field
determines a value of said high impedance drive signal and said
processing circuit provides said digital signal output indicative
of a position of said object in relation to said plurality of
electrically coupled conductive plates.
[0035] Preferably, said high impedance drive signal is also a sense
signal.
[0036] Preferably, said conductive plate layered construction is
formed by at least an upper conductive plate, a lower conducive
plate and a third conductive plate therebetween.
[0037] Alternatively, said conductive plate layered construction is
formed by a plurality of conductive plates, said plurality of
conductive plates being an odd number and there are n odd numbered
conductive plates and m even numbered conductive plates.
[0038] Preferably, said upper and lower conductive plates are
electrically connected to ground and said third conductive plate is
connected to said high impedance drive signal.
[0039] Preferably, each of said n odd numbered conductive plates
are electrically connected to ground and each of said m even
numbered conductive plates are connected to said high impedance
drive signal.
[0040] Preferably, said insulation layers are a compressible medium
such as high density foam.
[0041] Alternatively, said insulation layers are a compressible
medium such as an elastomer foam material.
[0042] Preferably, said processing circuit uses said changes in
said high impedance drive signal inputs to calculate at least one
of displacement, position, pressure, impact and energy caused by
said object.
[0043] Preferably, said digital signal output is input to a display
system incorporating an audible alarm.
[0044] Alternatively, said digital signal output is input to a
display system.
[0045] Alternatively, said digital signal output is input to an
audible alarm system.
[0046] Preferably, said digital signal output is transmitted from
said electric field sensing system via at least one of a radio,
mobile communications network and internet to a person located
remotely from a user of said electric field sensing system enabling
said remotely located person to receive on an electronic device
said digital data in real-time.
[0047] Preferably, said electronic device includes at least one of
a radio, mobile telephone, personal digital assistance, internet
connected device and computer.
[0048] Preferably, said at least one conductive plate is
constructed from a solid material.
[0049] Alternatively, said at least one conductive plate is
constructed from at least one of a flexible and stretchable
material.
[0050] Preferably, said solid material is a copper plate.
[0051] Alternatively, said solid material is a carbon impregnated
polyethylene pad.
[0052] Preferably, said at least one conductive plate is coated
with a conductive ink such as silver.
[0053] Alternatively, said at least one conductive plate is coated
with a conductive ink such as carbon.
[0054] Preferably, said flexible material is a conductive
membrane.
[0055] Alternatively, said flexible material is a plurality of
conductive fibres.
[0056] Preferably, said flexible material is adhered to or sewn to
a garment or other section of flexible type of material which, in
use, does not inhibit the ability of a user to perform a task.
[0057] In a third aspect the invention consists in a double layer
electric field sensing system used to detect movement, position and
pressure of an object comprising:
[0058] an electronic circuit used to generate a multiplexed high
impedance signal and a multiplexed low impedance inverted drive
signal,
[0059] a first conductive plate energised by said multiplexed high
impedance drive signal,
[0060] a second conductive plate energised by said multiplexed low
impedance inverted drive signal,
[0061] a compressible insulating layer located between said first
and second conductive plates,
[0062] a processing circuit that obtains as an input said
multiplexed high impedance drive signal, calculates variations in
said multiplexed high impedance drive signal and generates a
digital signal output, and
[0063] wherein said first conductive plate is electrically
orthogonal to said second conductive plate generating a matrix of
electrically coupled cells whereby a position of said object
determines a number of coupling interactions between said
electrically coupled cells and said processing circuit measures
said positions and provides said digital signal output indicative
of said object position.
[0064] Preferably, said high impedance drive signal is also a sense
signal.
[0065] Preferably, said insulation layers are a compressible medium
such as high density foam.
[0066] Alternatively, said insulation layers are a compressible
medium such as an elastomer foam material.
[0067] Preferably, said processing circuit uses said changes in
said multiplexed high impedance drive signal inputs to calculate at
least one of displacement, position, pressure, movement, impact or
energy caused by said conductive body.
[0068] Preferably, said digital signal output is input to a display
system incorporating an audible alarm.
[0069] Alternatively, said digital signal output is input to a
display system.
[0070] Alternatively, said digital signal output is input to an
audible alarm system.
[0071] Preferably, said digital signal output is transmitted from
said electric field sensing system via at least one of a radio,
mobile communications network and the internet to a person located
remotely from a user of said electric field sensing system enabling
said remotely located person to receive on an electronic device
said digital data in real-time.
[0072] Preferably, said electronic device includes at least one of
a radio, mobile telephone, personal digital assistance, internet
connected device and computer.
[0073] Preferably, said at least one conductive plate is
constructed from a solid material.
[0074] Alternatively, said at least one conductive plate is
constructed from at least one of a flexible and stretchable
material.
[0075] Preferably, said solid material is a copper plate.
[0076] Alternatively, said solid material is a carbon impregnated
polyethylene pad.
[0077] Preferably, said at least one conductive plate is coated
with a conductive ink such as silver.
[0078] Alternatively, said at least one conductive plate is coated
with a conductive ink such as carbon.
[0079] Preferably, said flexible material is a conductive
membrane.
[0080] Alternatively, said flexible material is a plurality of
conductive fibres.
[0081] Preferably, said flexible material is adhered to or sewn to
a garment or other section of flexible type of material which, in
use, does not inhibit the ability of a user to perform a task.
[0082] In a fourth aspect the present invention consists in a
method of monitoring the performance of a user incorporating any
one of the conductive plate arrangements and associated sensing
system circuit according to claims 1, 19 and 42 comprising the
steps of:
[0083] placing said conductive plate arrangement and said
associated sensing system in close proximity to said user,
[0084] measuring changes in electrical characteristics between said
conductive plates using said associated sensing system when said
user moves in relation to said conductive plates,
[0085] applying a plurality of algorithms to said measured changes
to calculate at least one of movement parameters of displacement,
force, shear force and pressure,
converting said movement parameters into a digital signal output,
and
[0086] outputting said movement parameters to said user.
[0087] Preferably, said step of measuring said changes in
electrical characteristics includes measuring fluctuations in a
high impedance drive signal applied to said conductive plate
arrangement as a result of said user's movement in relation to said
conductive plate arrangement.
[0088] Preferably, said step of outputting said movement parameters
includes inputting said digital signal output from said sensing
system to a display system incorporating an audible alarm.
[0089] Alternatively, said step of outputting said movement
parameters includes inputting said digital signal output from said
sensing system to a display system.
[0090] Alternatively, said step of outputting said movement
parameters includes inputting said digital signal output from said
sensing system to an audible alarm.
[0091] Preferably, said step of outputting said movement parameters
includes transmitting said digital signal output from said sensing
system to a remote electronic device.
[0092] To those skilled in the art to which the invention relates,
many changes in construction and widely differing embodiments and
applications of the invention will suggest themselves without
departing from the scope of the invention as defined in the
appended claims. The disclosures and the descriptions herein are
purely illustrative and are not intended to be in any sense
limiting.
[0093] This invention consists in the foregoing and also envisages
constructions of which the following gives examples.
BRIEF OF DRAWINGS
[0094] Preferred forms of the present invention will now be
described with reference to the accompanying drawings in which;
[0095] FIG. 1 is a block diagram of the electric field sensing
system of the first preferred embodiment of the present
invention,
[0096] FIGS. 2a and 2b are waveform diagrams illustrating high
impedance drive signal variations measured by the electric field
sensing system of FIG. 1,
[0097] FIG. 3 is a block diagram of a second preferred embodiment
of the present invention using a multilayered electric field
sensing system,
[0098] FIG. 4 is a side view of a layered electrically coupled
conductive plate used with the electric field sensing system of the
second embodiment of the present invention,
[0099] FIG. 5 is a block diagram showing a number of conductive
plates as applied to the multilayered electric field sensing system
of FIG. 3,
[0100] FIG. 6 is a flexible conductive pad applied to the electric
filed sensing system of FIG. 1,
[0101] FIG. 7 is a block diagram of a third preferred embodiment of
the present invention utilising a double layer electric field
sensing system,
[0102] FIG. 8 is a side view of an N.times.M flexible sensing pad
for insertion into a shoe using the electric field sensing system
of FIG. 1,
[0103] FIG. 9 is a block diagram of a digital system capable of
providing an aural and visual output to a user that can be applied
to any of the preferred embodiments of the present invention,
[0104] FIGS. 10a and 10b are side views of a layered electrically
coupled conductive plate used with the second and third preferred
embodiments of the present invention showing the change in distance
between the conductors as a result of a force being applied to the
conductors,
[0105] FIGS. 11a and 11b are side views of a layered electrically
coupled conductive plate used with the second and third preferred
embodiments of the present invention showing the effects of a shear
force being applied to the conductors,
[0106] FIGS. 12a and 12a are side views of a layered electrically
coupled conductive plate used with the second and third preferred
embodiments of the present invention showing the effects on the
conductive plates when a pressure is applied to the conductors,
[0107] FIG. 13 is a block diagram of a circuit attached to any one
of the preferred embodiments of the present invention enabling the
data output from the sensing system to be transmitted to a person
located remotely from a user.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0108] Whilst there are a number of different monitors available
for detecting a human, animal or any other forms of non-insulating
object movement and/or for detecting changes in respiratory rate or
detecting apnea, the present invention is directed to an electric
field sensing system 1 which can be utilised in a broad range of
applications, such as; infant respiratory monitoring systems,
pressure detection systems as a means of preventing bed sores; in
wheel chairs to detect the movement of the occupant and provide a
means of determining the risk of the occupant developing sores as a
result of being in a sedentary position for a prolonged period of
time; placing the sensor in a shoe to detect pressure while running
in order to determine false leg follow-through based on early foot
strike detection or alternatively the system could be used as a
proximity sensor to control the sense of touch for robotic limbs.
The contactless monitoring system allows static parameters such as
force and pressure to be measured. As illustrated by the above
examples the number and types of application to which the present
invention can be directed is very broad.
[0109] Referring to FIG. 1, a first preferred embodiment of the
electric field sensing system of the present invention is shown
that uses a single conductive plate 3 that provides improvements
over systems currently available in a number of industries and the
medical or sports industries in particular. A conductive plate 3
coupled with a microprocessor based circuit is described which
provides a means of measuring position and movement variations
applied to the conductive plate 3 such that erroneous or false
alarm detections are substantially reduced. A system of this type
will provide a means of enhancing personnel safety through the
provision of visual and/or audible alarms to which medical staff,
for example, will react to knowing that there is a minimal risk of
the alarm being false.
[0110] It will be appreciated that the electric field sensing
system 1 as described in the first preferred embodiment of the
present invention can be used in a broad range of applications
including the medical and sports industries generally but will now
be described below with reference to use in the neonatal care
environment to monitor the respiratory rate of neonates and in
particular for the early detection of apnea (cessation of
breathing). It will be appreciated that the present invention can
be applied to various applications within the hospital environment,
including but not limited to a contact less electric field pad.
Electric Field Sensing Circuit
[0111] The conductive plate 3 is constructed from a conductive
material such as copper or carbon impregnated polyethylene and may
also be coated with conductive inks such as silver or carbon.
Alternatively, the plate 3 may be constructed from a flexible
material using one or a number of sandwiched membranes. The circuit
which provides the signal input to drive the electric field sensing
system 1 is illustrated at FIG. 1. In the first preferred
embodiment, an alternating current (AC) source 4 generates a sine
wave signal (reference signal) 5 of a pre-selected frequency. To
generate a high impedance signal 7 to drive the electric field
sensing system 1, the reference signal 5 is input through a high
impedance resistor 6 before being applied to conductive plate 3.
The reference signal 5 is also used as an input clocking signal to
an analogue-to-digital converter (ADC) 10. Hence, as the reference
signal 5 and ADC clock signal are in phase, synchronisation of
signal peaks and troughs can be measured using the ADC 10.
[0112] An electric field 26 is generated around the conductive
plate 3 being driven with the high impedance drive signal 7. When a
conductive body or object 2 moves over or near the conductive plate
3, the electric field 26 between the conductive body 2 and the
conductive plate 3 is altered. The movement alters the electric
field coupling of the high impedance drive signal 7. Moving a
conductive body or object 2 closer to the conductive plate 3
increases the coupling between the high impedance drive signal 7
and the object 2 thereby attenuating the high impedance drive
signal 7. Hence, the greater the common area between the conductive
plate 3 and object 2, the higher the attenuation of the high
impedance drive signal 7 and the subsequent changes in electric
field coupling are measured as a voltage by the processing
circuitry as shown in FIG. 1. An example of changes in voltage as a
result of changes in electric field coupling due to the movement of
the object 2 in relation to the conductive plate 3 is shown in FIG.
2. Measuring the change in high impedance drive signal strength
provides a means of measuring the distance between the conductive
plate 3 and the object 2 or common area between the conductors 2, 3
to be measured. Hence, the high impedance drive signal 7 is also
used as the sense signal.
[0113] With reference to FIG. 2a and 2b, the waveform illustrates
the changes in the high impedance drive signal due to an object or
conductive body 2 moving towards the conductive plate 3. FIG. 2a
shows a sine wave of voltage V.sub.c, having a peak-to-peak
amplitude V.sub.p-p that corresponds to the high impedance drive
signal 7 applied to the conductive plate 3 with no movement
detected by the electric field sensing system 1. When the electric
field sensing system 1 has an external force applied or conductive
body 2 changes position, the high impedance drive signal 7
amplitude V.sub.p-p is reduced as a result of the electrical
coupling between the conductive plate 3 in relation to the
conductive body 2. The change in amplitude V.sub.p-p is shown in
FIG. 2b. The reduction in high impedance drive signal 7 amplitude
V.sub.p-p is measured by the processing circuitry which applies a
number of algorithms to convert the signal variations into a
meaningful data output to a display system and/or audible alarm
system (not shown). Whilst a symmetrical sine wave alternating
current is applied to the system as shown in FIG. 1, the processing
circuitry is capable of performing the necessary calculations and
provide a meaningful output when other symmetrical or unsymmetrical
waveforms are applied.
[0114] To increase the sensitivity of the electric field sensing
system 1, the reference signal 5 may be input to a difference
amplifier (not shown) along with the high impedance drive signal 7.
The difference between the reference signal 5 and high impedance
drive signal 7 can be measured when the separation distance between
conductors 2, 3 is varied thereby causing the high impedance drive
signal voltage to vary as a result of the change in electric field
coupling. These voltage variations are buffered 9 and input to the
ADC 10 thereby converting the resultant analogue voltage into a
digital data output which is input to the microprocessor 11 for
further processing. The microprocessor 11 implements a number of
algorithms in order to measure sensed voltage signal variations
representative of movement and force or pressure variations which
correspond to changes in breathing patterns, for example.
[0115] The microprocessor 11 uses a crystal clock (not shown) to
clock the circuit internal digital signals and is also used as a
source to drive the conductive plate or sensor plate 3. This
provides an advantage over other systems as the microprocessor 11
inherently knows the frequency of the drive 5 and sense signals 7.
Hence, using software programmes, the microprocessor 11 can phase
lock with the sense signal 7. This allows the ADC 10 to be
triggered in phase and in a frequency dependent way thereby
allowing synchronous detection of changing events without the use
of external devices.
[0116] Therefore, the sensing system 1 of the first preferred
embodiment of the present invention is inherently frequency locked
and the ADC 10 synchronously detects the time varying signal,
allowing the time varying signal to be referenced to a zero
frequency reference. Hence, timing variations due to changes in the
timing source over time and changes in environmental conditions are
naturally tracked and cancelled.
Multilayered Electric Field Sensing System
[0117] With reference to FIGS. 3 and 4, a second preferred
embodiment of the present invention is shown which uses at least
three conductive plates 15, 16, 17, having an insulating layer 18
placed between each conducting plate 15, 16, 17, forming a
sandwich. The sandwiched conducting plate system coupled with a
microprocessor based circuit as described in this embodiment
provides a means of measuring position, movement and pressure
variations applied to the sandwiched conductive plates such that
erroneous or false alarm detections are substantially reduced. The
use of a multilayered electric field sensing system 14 provides a
means of calculating pressure variations as well as movement and
position variations.
[0118] As illustrated in FIG. 5, the multilayered sandwiched
conductor plate sensing system 30 need not be limited to three
conductive plates. FIG. 5 shows a number of conductors n1, m1, n2,
m2 . . . m.sub.z, n.sub.z, having a compressible medium 18 between
each conductor of the type provided in FIGS. 3 and 4. The
conductors n1 to n.sub.z may be either solid conductors or
alternatively, each of the "plates" can be flexible conductive
surface such as a membrane adhered to or sewn into material. As can
be see in FIG. 5, each alternative conductive surface (n1, n2 . . .
n.sub.z) has been grounded while the interleaved conductive
surfaces (m1, m2 . . . m.sub.z) are driven by the high impedance
drive signal 7 enabling a sensed signal to be detected as
previously detailed in the first preferred embodiments of the
present invention.
Conductive Plates
[0119] FIG. 4 shows the multilayered construction of the sensing
system 14 having at least three conductive plates 15, 16, 17 with
insulated layers 18 between each plate forming a sandwich type
construction. The insulated layers 18 are formed of a compressible
material such as high impact foam or other elastomer foam. Each of
the conductive plates 15, 16, 17 are of the same construction as
those as described with reference to the first preferred embodiment
as shown in FIG. 1. The upper and lower conductive plates 15, 16
are electrically connected to ground in order to provide a shield
to isolate the sensor plate (middle conductive plate) 17 from
electromagnetic interference whilst acting as coupling plates, such
that movement of these plates 15, 16 causes the high impedance
drive signal 7 supplied to the sensor plate 17 to vary.
[0120] FIG. 6 shows an alternative type of conductor 40 whereby the
conductor 40 is made from a stretchable medium such as a membrane
sewn or adhered to material. The conductor 40 has metallic fingers
41, conductive ink or conductive fibres which are electrically
connected to the drive and sensing circuitry of any of the
preferred embodiments of the present invention. Hence, when the
flexible conductive material 40 is stretched, the coupling changes
between the metallic fingers 41 thereby causing the distance
between adjacent metallic fingers 41 to vary and hence the high
impedance drive signal 7 supplied to alternate fingers 41 to
vary.
Multilayered Electric Sensing Circuit
[0121] A circuit that provides the signal input to drive the
multilayered electric field sensing system 14 is illustrated at
FIG. 3. This sensing circuit can also be applied to the
multilayered electric field sensing system 30 as illustrated in
FIG. 5. The sensor plate 17 is connected to an alternating current
(AC) source 50 which generates a sine wave signal (reference
signal) 51 from which a high impedance signal 53 to drive the
sensing system 14 is generated when the reference signal 51 is
input through a high impedance resistor 52 before being input to
sensor plate 17. The reference signal 51 is also used as an input
clocking signal to the analogue-to-digital converter (ADC) 55.
Hence, as the reference signal 51 and ADC clock signal are in
phase, synchronisation of signal peaks and troughs can be measured
using the ADC 55.
[0122] As the sense plate 17 is sandwiched between an electrically
grounded upper and lower conductive plate 15, 16, and separated by
a compressive medium 18, changes in the position of the conductive
plates 15, 16 either horizontally or vertically, alters the
electric field coupling of the high impedance drive signal 53.
Moving one or both of the conductors 15, 16 closer to the sense
plate 17 increases the coupling between the high impedance drive
signal 53 and the conductor 17 thereby attenuating the high
impedance drive signal 53. Alternatively, moving the conductors 15,
16, 17 horizontally in relation to each other changes the common
area between the conductors 15, 16, 17. This also results in a
change in electric field coupling thereby changing the high
impedance drive signal 53. Hence, the greater the common area
between conductors 15, 16, 17, the higher the attenuation of the
high impedance drive signal 53. The subsequent changes in electric
field coupling are measured as a voltage by the processing
circuitry 56. Measuring the change in high impedance drive signal
strength provides a means of measuring the distance between two
conductors or common area between conductors to be measured.
[0123] The sensitivity of the multilayered electric field sensing
system 14 can be increased in the manner already described with
reference to FIG. 3 using a difference amplifier (not shown) along
with the high impedance drive signal 53.
Matrix System Circuit
[0124] A third preferred embodiment of the present invention is
shown in FIG. 7. A multiplexed electric field sensing system 19 is
provided using two conductive plates 20, 21 separated by a
compressive medium 18 of the type described with reference to FIGS.
3 and 5. A matrix of cells is generated using orthogonal drive
signals in conjunction with multiplexed or switched electric
fields. The lower conductor (rows) 21 is driven with a multiplexed
high impedance drive signal 23 and the upper conductor (columns)
20, an electrically orthogonal conductive plate, is electrically
grounded or driven with a multiplexed low impedance inverted drive
signal 22. Hence, where the upper and lower conductors 20, 21
electrically overlap, changes in distance between the two
conductors 20, 21 causes a change in the amplitude and phase of the
high impedance drive signal 24 between the conductive plates 20,
21. This change in high impedance drive signal 24 is converted from
an analogue signal to digital data via the ADC 10 and provided as
an input to the microprocessor 11. By selectively driving different
orthogonal conductors in the matrix, each cell in the matrix may be
measured and position and movement within the matrix can be
determined. Furthermore, multiplexing several drive signals in time
with multiple orthogonal receiving signals enables an X-Y
resolution of force on the conductive plates 20 and 21 to be
determined.
[0125] Pressure and force measurements can be used to determine a
person's 2 gait. The measured data can be used as a feedback
mechanism for control loops. These loops can control various
pressure plates within a person's shoe, the follow-through of an
artificial leg or control the dispensing of medicine. FIG. 8 shows
an n.times.m matrix sensing pad whereby an sensing pad is inserted
into a user's shoe which is made up using a number of conductive
plates or flexible membranes adhered to the shoe inner. This plate
system operates in the same maimer as the matrix sensing system as
described above and is capable of sensing events in three
dimensions.
Data Display
[0126] The calculated data can be output via an RS232 port (not
shown) or other know connection ports, to a display system 70
providing a map illustrating the pressure difference, for example,
being applied to the electric field sensing system 1, 14, 19, 30 as
shown in FIG. 9. Alternatively, the display system 70 may provide a
user, such as medical personnel, with a numerical readout of
pressure, force or movement variations as a result of changes in
the electric field sensing system 1, 14, 19, 30. An audible alarm
71 can also be generated providing an aural warning that a patient
has been sedentary for an extended duration, or that breathing has
ceased for example.
Calculations
[0127] As mentioned previously, the microprocessor 11 applies a
number of software algorithms to determine pressure, force,
displacement and types of forces applied to and sensed by the
conductive plates for each of the embodiments of the present
invention. FIGS. 10a to 12b illustrate the types of forces on
conductor plates 16 and 17 and compressible material 18 that can be
detected and measured. FIG. 10a shows a force being applied to the
upper conductive plate 17. Hence, by way of example, with the
multilayered electric field sensing system 14 as shown in FIG. 3,
as the drive signal frequency and amplitude remain constant, then
knowing the force constant and density of the compressible medium
18, the derived force can be determined by multiplying the
displacement of the conductive plates 15, 16, 17 by the
compressible medium force constant. FIGS. 11a and 11b show the
effects of a shear force being applied to the electric field
sensing system 14. The electrical coupling between the plates 16
and 17 can be proportional to the shear forces as well as the
orthogonal forces applied to the plates 16, 17 enabling shear force
to be determined. Also, knowing the area of the sensor plate 17,
the pressure can also be calculated by dividing the calculated
force by the sensor plate area as illustrated in FIGS. 12a and 12b.
Other events that may be measured are listed below: [0128] a.
Energy which is calculated based on force applied over time. [0129]
b. Impact can be calculated based on a determination of the energy
applied over time and the speed of changes of force applied to the
system. [0130] c. Breathing, diaphragm expansion and heart rate can
be calculated based on the expected frequency content of each of
these events and the displacement caused by the sensor system.
[0131] d. Activity based events such as seating position, walking
or running gait, kicking a ball or swing a golf club for example,
can be determined by adding several of the sensed events over
time.
[0132] It would also be possible to determine for example, a mode
of transport or type of physical activity by combining the electric
field sensing system 14 with tilt and vibration sensors (not
shown). Whilst other more complex calculations are undertaken by
the microprocessor 11, details of these algorithms go beyond the
scope of the object of the present invention and are therefore not
disclosed.
Communications
[0133] The sensing and processing circuit of each of the preferred
embodiments of the present invention can be modified to incorporate
the output of sensed data to a communications device as shown in
FIG. 13. The incorporation of a communications device will provide
a means of remotely sensing a physical state or method of activity
in a sports event, for example. Hence, data can be output to a
coach, medical practitioner or other person monitoring the sensed
data via a radio, mobile telephone network 61 or alternatively via
the internet. The data is sent over the radio or mobile phone link
62 to the remote person's radio, mobile phone, personal digital
assistant (PDA), internet connected device, computer or other
electronic device (not shown) capable of receiving radio, internet
and/or mobile phone type signals. Hence, real-time feedback can be
obtained by an athlete's coach, a doctor or other person monitoring
the sensing system 60. Hence, medical compliance and the
characteristics of potential medical problems can be logged and
transmitted enabling medical personnel, for example, to monitor a
person and enable prognosis and/or diagnosis to be undertaken as
soon as a problem arises.
[0134] Furthermore, a user's position along with sensed data 60 may
also be monitored remotely by adding GPS circuitry 63 at the output
of the sensing circuit 60. This type of data would be of great
benefit to personnel involved in a search and rescue type of
situation particularly if the sensing system user 64 is in
difficulty and is known to be a diabetic for example, and as such,
the risk of the user going into a coma is greatly reduced.
* * * * *