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System, Method, and Computer-Program Product
For Measuring Pressure Points
Copyright Notice
[0001] Portions of the disclosure of this patent document may contain material
that is subject to copyright protection. The copyright owner has no objection
to the facsimile reproduction by anyone of the patent document or the patent
disclosure, as it appears in the United States Patent and Trademark Office
file
or records, but otherwise reserves all copyright rights whatsoever.
Cross-Reference to Related Applications
[0002] This application claims the benefit of the following related
applications:
application Serial No. 12/155,558, filed on June 5, 2008, which, in turn,
claims
the benefit of application Serial No. 60/924,931, filed on June 5, 2007, and
application Serial No. 60/996,608, filed on November 27, 2Q07, each of which
is incorporated herein by reference in its entirety.
Background of the Invention
Field of the Invention
[0003] The present invention in its disclosed embodiments is related generally
to pressure sensing systems, methods, and computer-program products, and
more particularly to such systems, methods, and computer-program products
for sensing pressure along the bottom of a user's foot during sports training
and monitoring applications, electronic games, and diagnostic systems as will
become more apparent hereinafter. However, it should be readily appreciated
to those of ordinary skill in the art that the following embodiments may also
be
applicable to the other pressure sensing applications.
Statement of the Prior Art
[0004] Athletes utilize various metrics to measure their performance and chart
their workouts. The metrics are recorded and analyzed both during and after
workouts. For example, interval type workouts typically involve multiple sets
of intense activity, semi-intense activity, and rest. The intense activity may
be
characterized by a range of metrics which correlate to the desired intensity
for
a particular athlete. Likewise, the rest or semi-intense activity periods may
be
characterized by a range or metrics which correlate to the desired restful
state
for a particular athlete.
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[0005] Accordingly, it would be desirable to provide systems, methods, and
computer-program products for sensing pressure along the bottom of a user's
foot, to record and analyze such metrics during sports training and monitoring
applications, electronic games, and diagnostic systems.
[0006] The human foot combines mechanical complexity and structural
strength. The ankle serves as foundation, shock absorber, and propulsion
engine. The foot can sustain enormous pressure (i.e., in the range of about
several tons over the course of a one-mile run) and provides flexibility and
resiliency.
[0007] The foot and ankle contain 26 bones (i. e., nearly one-quarter of the
bones in the human body are in the feet); 33 joints; more than 100 muscles,
tendons (i.e., fibrous tissues that connect muscles to bones), and ligaments
(i.e., fibrous tissues that connect bones to other bones); and a network of
blood vessels, nerves, skin, and soft tissue.
[0008] These components work together to provide the body with support,
balance, and mobility. A structural flaw or malfunction in anyone part can
result in the development of problems elsewhere in the body. Abnormalities
in other parts of the body can lead to problems in the feet. Embodiments of
the present invention help sense the pressure exerted at a plurality of points
of the user's feet to help alleviate such problems.
[0009] Structurally, the foot has three main parts: the forefoot, the midfoot,
and the hindfoot. The forefoot as shown in FIGS. 2A and 2B is composed of
the five toes (called phalanges) and their connecting long bones
(metatarsals). Each toe (phalanx) is made up of several small bones. The
big toe (also known as the hallux) has two phalanx bones-distal and proximal.
It has one joint, called the interphalangeal joint. The big toe articulates
with
the head of the first metatarsal and is called the first metatarsophalangeal
joint (MTPJ for short). Underneath the first metatarsal head are two tiny,
round bones called sesamoids. The other four toes each have three bones
and two joints. The phalanges are connected to the metatarsals by five
metatarsal phalangeal joints at the ball of the foot. The forefoot bears half
the
body's weight and balances pressure on the ball of the foot.
[0010] The midfoot has five irregularly shaped tarsal bones, forms the foot's
arch, and serves as a shock absorber. The bones of the midfoot are
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connected to the forefoot and the hindfoot by muscles and the plantar fascia
(arch ligament).
[0011] The hindfoot is composed of three joints and links the midfoot to the
ankle (talus). The top of the talus is connected to the two long bones of the
lower leg (tibia and fibula), forming a hinge that allows the foot to move up
and down. The heel bone (calcaneus) is the largest bone in the foot. It joins
the talus to form the subtalar joint. The bottom of the heel bone is cushioned
by a layer of fat.
[0012] A network of muscles, tendons, and ligaments supports the bones and
joints in the foot. There are 20 muscles in the foot that give the foot its
shape
by holding the bones in position and expand and contract to impart
movement. The main muscles of the foot are: the anterior tibial, which
enables the foot to move upward; the posterior tibial, which supports the
arch;
the peroneal tibial, which controls movement on the outside of the ankle; the
extensors, which help the ankle raise the toes to initiate the act of stepping
forward; and the flexors, which help stabilize the toes against the ground.
Smaller muscles enable the toes to lift and curl.
[0013] There are elastic tissues (tendons) in the foot that connect the
muscles
to the bones and joints. The largest and strongest tendon of the foot is the
Achilles tendon, which extends from the calf muscle to the heel. Its strength
and joint function facilitate running, jumping, walking up stairs, and raising
the
body onto the toes. Ligaments hold the tendons in place and stabilize the
joints. The longest of these, the plantar fascia, forms the arch on the sole
of
the foot from the heel to the toes. By stretching and contracting, it allows
the
arch to curve or flatten, providing balance and giving the foot strength to
initiate the act of walking. Medial ligaments on the inside and lateral
ligaments on outside of the foot provide stability and enable the foot to move
up and down. Skin, blood vessels, and nerves give the foot its shape and
durability, provide cell regeneration and essential muscular nourishment, and
control its varied movements.
[0014] Pressure sensing methods, systems, and computer-program products
in particular may be used to sense pressure at a plurality of points of a
user's
foot, including its bones, joints, muscles, tendons, and ligaments.
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Summary of the Invention
[0015] These and other objects, advantages, and novel features according to
embodiments of the present invention are accomplished by a sensing system
generally comprising a transducer having a plurality of points of interest,
first
means for collecting and transmitting data sensed at the plurality of points
of
interest, first means for coupling that data across a network by way of second
means coupling same to a collector node and then to a computer for analysis.
[0016] A "computer" may refer to one or more apparatus and/or one or more
systems that are capable of accepting a structured input, processing the
structured input according to prescribed rules, and producing results of the
processing as output. Examples of a computer may include: a computer; a
stationary and/or portable computer; a computer having a single processor,
multiple processors, or multi-core processors, which may operate in parallel
and/or not in parallel; a general purpose computer; a supercomputer; a
mainframe; a super mini-computer; a mini-computer; a workstation; a micro-
computer; a server; a client; an interactive television; a web appliance; a
telecommunications device with internet access; a hybrid combination of a
computer and an interactive television; a portable computer; a tablet personal
computer (PC); a personal digital assistant (PDA); a portable telephone;
application-specific hardware to emulate a computer and/or software, such as,
for example, a digital signal processor (DSP), a field-programmable gate array
(FPGA), an application specific integrated circuit (ASIC), an application
specific instruction-set processor (ASIP), a chip, chips, a system on a chip,
or
a chip set; a data acquisition device; an optical computer; a quantum
computer; a biological computer; and generally, an apparatus that may accept
data, process data according Yo one or more stored software programs,
generate results, and typically include input, output, storage, arithmetic,
logic,
and control units.
[0017] "Software" may refer to prescribed rules to operate a computer.
Examples of software may include: code segments in one or more computer-
readable languages; graphical and or/textual instructions; applets; pre-
compiled code; interpreted code; compiled code; and computer programs.
[0018] A "computer-readable medium" may refer to any storage device used
for storing data accessible by a computer. Examples of a computer-readable
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medium may include: a magnetic hard disk; a floppy disk; an optical disk,
such as a CD-ROM and a DVD; a magnetic tape; a flash memory; a memory
chip; and/or other.types of media that can store machine-readable instructions
thereon.
[0019] A "computer system" may refer to a system having one or more
computers, where each computer may include a computer-readable medium
embodying software to operate the computer or one or more of its
components. Examples of a computer system may include: a distributed
computer system for processing information via computer systems linked by a
network; two or more computer systems connected together via a network for
transmitting and/or receiving information between the computer systems; a
computer system including two or more processors within a single computer;
and one or more apparatuses and/or one or more systems that may accept
data, may process data in accordance with one or more stored software
programs, may generate results, and typically may include input, output,
storage, arithmetic, logic, and control units.
[0020] A "network" may refer to a number of computers and associated
devices that may be connected by communication facilities. A network may
involve permanent connections such as cables or temporary connections
such as those made through telephone or other communication links. A
network may further include hard-wired connections (e.g., coaxial cable,
twisted pair, optical fiber, waveguides, etc.) and/or wireless connections
(e.g.,
radio frequency waveforms, free-space optical waveforms, acoustic
waveforms, etc.). Examples of a network may include: an internet, such as
the Internet; an intranet; a local area network (LAN); a wide area network
(WAN); and a combination of networks, such as an internet and an intranet.
Exemplary networks may operate with any of a number of protocols, such as
Internet protocol (IP), asynchronous transfer mode (ATM), and/or
synchronous optical network (SONET), user datagram protocol (UDP), IEEE
802.x, etc.
[0021] Embodiments of the present invention may include apparatuses for
performing the operations disclosed herein. An apparatus may be specially
constructed for the desired purposes, or it may comprise a general-purpose
device selectively activated or reconfigured by a program stored in the
device.
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[0022] Embodiments of the invention may also be implemented in one or a
combination of hardware, firmware, and software. They may be implemented
as instructions stored on a machine-readable medium, which may be read
and executed by a computing platform to perform the operations described
herein.
[0023] In the following description and claims, the terms "computer program
medium" and "computer readable medium" may be used to generally refer to
media such as, but not limited to, removable storage drives, a hard disk
installed in hard disk drive, and the like. These computer program products
may provide software to a computer system. Embodiments of the invention
may be directed to such computer program products.
[0024] References to "one embodiment," "an embodiment," "example
embodiment," "various embodiments," etc., may indicate that the
embodiment(s) of the invention so described may include a particular feature,
structure, or characteristic, but not every embodiment necessarily includes
the
particular feature, structure, or characteristic. Further, repeated use of the
phrase "in one embodiment," or "in an exemplary embodiment," do not
necessarily refer to the same embodiment, although they may.
[0025] In the following description and claims, the terms "coupled" and
"connected," along with their derivatives, may be used. It should be
understood that these terms are not intended as synonyms for each other.
Rather, in particular embodiments, "connected" may be used to indicate that
two or more elements are in direct physical or electrical contact with each
other. "Coupled" may mean that two or more elements are in direct physical
or electrical contact. However, "coupled" may also mean that two or more
elements are not in direct contact with each other, but yet still cooperate or
interact with each other.
[0026] An algorithm is here, and generally, considered to be a self-consistent
sequence of acts or operations leading to a desired result. These include
physical manipulations of physical quantities. Usually, though not
necessarily,
these quantities take the form of electrical or magnetic signals capable of
being stored, transferred, combined, compared, and otherwise manipulated.
It has proven convenient at times, principally for reasons of common usage, to
refer to these signals as bits, values, elements, symbols, characters, terms,
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numbers or the like. It should be understood, however, that all of these and
similar terms are to be associated with the appropriate physical quantities
and
are merely convenient labels applied to these quantities.
[0027] Unless specifically stated otherwise, and as may be apparent from the
following description and claims, it should be appreciated that throughout the
specification descriptions utilizing terms such as "processing," "computing,"
"calculating," "determining," or the like, refer to the action and/or
processes of
a computer or computing system, or similar electronic computing device, that
manipulate and/or transform data represented as physical, such as electronic,
quantities within the computing system's registers and/or memories into other
data similarly represented as physical quantities within the computing
system's memories, registers or other such information storage, transmission
or display devices.
[0028] In a similar manner, the term "processor" may refer to any device or
portion of a device that processes electronic data from registers and/or
memory to transform that electronic data into other electronic data that may
be stored in registers and/or memory. A "computing platform" may comprise
one or more processors.
Brief Description of the Drawings
[0029] The foregoing and other features of the present invention will become
more apparent from the following description of exemplary embodiments, as
illustrated in the accompanying drawings wherein like reference numbers
generally indicate identical, functionally similar, and/or structurally
similar
elements. Usually, the left most digit in the corresponding reference number
will indicate the drawing in which an element first appears.
[0030] FIG. 1 illustrates a sensing system according to a first embodiment of
the present invention;
[0031] FIGS. 2A and 2B illustrate parts of the human foot, some of which may
be sensed by the sensing system shown in FIG.1;
[0032] FIG. 3 illustrates a portion of the sensing system shown in FIG. 1,
with
an exploded view of a transducer according thereto;
[0033] FIG. 4 illustrates in schematic format electrode grid selector mapping
means which may be used with the transducer shown in FIG. 3;
[0034] FIG. 5 illustrates in schematic format a controller which incorporates
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the electrode grid selector mapping means shown in FIG. 4;
[0035] FIG. 6 illustrates a graph showing the dependency of the resistance of
the transducer as a function of pressure sensed by same;
[0036] FIG. 7 illustrates a flowchart of the transmission of data sensed by
the
sensing system of FIGS. 1 and 3-6;
[0037] FIG. 8 illustrates a first electrode grid layer of a transducer
according to
another embodiment of the present invention;
[0038] FIG. 9 illustrates a second electrode grid layer which may be used with
the first electrode grid layer of a transducer according to another embodiment
of the present invention;
[0039] FIGS. 10A-10F illustrate in schematic format portions of an RF module
which may be used with the first and second electrode grid layers shown in
FIGS. 8 and 9; and
[0040] FIGS. 11 and 12 illustrate a first and a second algorithm which may be
used with transducers according to FIGS. 8, 9 and 10A-10F.
Detailed Description of the Embodiments
[0041] Exemplary embodiments are discussed in detail below. While specific
exemplary embodiments are discussed, it should be understood that this is
done for illustration purposes only. In describing and illustrating the
exemplary embodiments, specific terminology is employed for the sake of
clarity. However, the embodiments are not intended to be limited to the
specific terminology so selected. Persons of ordinary skill in the relevant
art
will recognize that other components and configurations may be used without
departing from the true spirit and scope of the embodiments. It is to be
understood that each specific element includes all technical equivalents that
operate in a similar manner to accomplish a similar purpose. Therefore, the
examples and embodiments described herein are non-limiting examples.
[0042] Referring now to the drawings, wherein like reference numerals and
characters represent like or corresponding parts and steps throughout each of
the many views, there is shown in FIG. 1 a sensing system 100 according to a
first embodiment of the present invention. System 100 generally comprises a
transducer 102 having a plurality of points of interest 104a, 104b, 104c,
104d,
104e, an insole node 106 for collecting and transmitting data sensed at the
plurality of points of interest 104a through 104e, first means 108 for
coupling
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that data across a network 110, by way of second means 112 for coupling
same to a collector node 114, and then to a computer 116.
[0043] FIG. 3 illustrates a portion of the sensing system 100 shown in FIG. 1,
with an exploded view of a transducer 300 according thereto. The insole of
sensing system 100 comprises a foot force transducer 300 which may include
a continuous capacitance pressure sensor system. Conventional foot force
transducers have discrete arrays of capacitors formed by overlapping two sets
of conducting strips laid in orthogonal directions on opposite sides of a
center
layer in a three-layer configuration.
[0044] Unlike such conventional transducers, the design of sensing system
100 allows for flexible placement of conductive elements when creating the
typical three-layer configuration. The continuous capacitance pressure
sensor elements of the insoles are made using a pressure sensitive variable
conductive polymer 302 between conductive traces 304, 306 on sheets 308,
310 of flexible circuit made of a flexible polymer film laminated to a thin
sheet
of copper that is etched to produce the conductor patterns. This polyimide
film is high heat resistance, has dimensional stability, good dielectric
strength,
with high flexibility, which allows it to survive hostile environments.
[0045] The continuous resistive/capacitive sensor layer may be an extruded
electrostatic discharge (ESD) type ultra high-density conductive XPU foam.
This is used to protect against very-high voltage ESD and provide a
compressible form factor for physical device protection against movement
shock. The material provides linear resistive and capacitive characteristics
through a range of compression forces (0 - 30 psi) as shown in FIG. 6.
[0046] The XPU foam used in layer 302 is a semiconductor that changes its
characteristic impedance as a function of applied pressure or compression.
As FIG. 6 shows, the impedance characteristics of the material are non-linear
at low applied pressures (e.g., less than 10 psi) or compression, and become
linear as the applied pressure or compression increases. Thicknesses of the
XPU material is also a determining factor of characteristic XPU material
impedance. The impedance function is characterized by:
Z(p) XPU = [R(p) + jwC(p)] (1 - exp(-p/Rc)) for 0 <= p <=Pc
Z(p) XPU = R(p) + jwC(p) for Pc < p <Pmax
Z(p) XPU R(p) for Po < p < 30 psi Po = Pc * n * 0.125
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where n = number of XPU layers (i.e., thickness = 0.125 inches) and P is the
operating linear starting pressure. The characteristic impedance of the XPU
material may be profiled algorithmically with embedded software running on a
processor of sensing system 100.
[0047] It may be appreciated that variable pressure analysis point techniques
may be used to dynamically map a plurality of points/regions of interest for
the
foot pressure measurement. For instance, and referring again to FIG. 1, a
portion of the heel area 104a and the toe areas 104c, 104d may be measured
for approximately 10 milliseconds, while an arch area 104e may be measured
for 25 milliseconds. This would allow for pattern measurements, for instance,
in the case of persons with diabetes, where the nerve damage as a result of
the disease does not allow the person to become aware of the fact that
certain areas of the feet are swelling. By using targeted pattern
measurement, alerts to changes in plantar foot pressure variations may be
provided.
[0048] It is contemplated that other materials such as piezoceramic materials
which may provide capacitive, piezoelectric, and/or resistive effects may also
be used.
[0049] The transducer 300 of sensing system 100 incorporates these modular
lightweight, high resolution, continuous pressure sensing shoe insoles, which
may be reconfigurable for varying arrangements, to wirelessly transmit
through an RF module 312, detailed pressure data to a computer 116, where
the data may be collated and collectively displayed. Sensing system 100 may
be integrated with other systems (e.g., vision based sensing systems) to
provide robust multi-modal sensing capabilities. Sensing system 100, thus,
not only provides a series of applications for data analysis/visualization,
data
recording and playback, but also may be grouped together to form clusters of
sensing systems that send real-time data to computers.
[0050] Sensing system 100 detects the changes in the electrical properties of
continuous capacitance pressure sensors, caused by the mechanical
deformation of its material. It may have typical recording durations of about
one second at a sampling rate of 50 Hz for a transducer 300 comprising 200
elements, which results in about 10,000 pressure data points per transducer
per second. With this volume of information, visual presentation and data
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reduction techniques may be used. The graphical representation of pressure
distribution may be through wire frame diagrams 314. These pressure maps
are obtained for each sampling interval or at specific instants during the
foot-
ground contact. A peak pressure graphical representation 316 may also be
used to illustrate individual foot contact behavior with the ground. This
image
may be created by presenting the highest pressures under the foot, as they
have occurred at any time during the ground contact.
[0051] Sensing system 100 is able to measure plantar pressure during bipedal
standing, which results in about 2.6 times higher heel against forefoot
pressures. The highest forefoot pressures are located under the second and
third metatarsal heads. There is almost no load sharing contribution of the
toes during this standing period. The peak plantar pressures indicate no
substantial relationship to body weight. Sensing system 100 measures foot
pressures during bipedal standing, walking, and running and shows the
highest pressures under the forefoot are found under the third metatarsal
head. For bipedal standing as well as walking, peak pressures beneath the
third metatarsal head are substantially higher than under the other metatarsal
heads. When running, during the impact phase of the ground reaction force,
the momentum from the decelerating limb rapidly changes as the foot collides
with the ground, resulting in a transient force transmitted up the skeleton.
These forces reach magnitudes of up to three times body weight. The
repetitive transmission of these forces contributes to degradation and overuse
injuries. The ability of sensing system 100 to measure plantar pressure
distributed over the sole of a foot during running allows for an early
determination of potential degradation and overuse injury by profiling the
foot's biomechanical characteristics as a result of the impact phase of the
ground reaction force.
[0052] FIG. 4 illustrates in schematic format electrode grid selector mapping
means 400 which may be used with the transducer shown in FIG. 3. The grid
selector mapping means 400 may comprise a combination of logic, firmware,
and hardware in a suitable microcontroller. Transducer 300 comprises three
layers of conductive foam 302 between the electrode grids (not shown in FIG.
4) on sheets 308, 310. Such three-layer configuration is electrically coupled
between +Vcc and ground by way of a bias resistor 402. Vfout from sheet 308
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is input to a 10-bit analog-to-digital converter (ADC) 406, which outputs ten
bits of digital output.
[0053] FIG. 5 illustrates in schematic format a microcontroller 500 which
incorporates the electrode grid selector mapping means shown in FIG. 4.
[0054] On start up, sensing system 100 first determines if it will be a
collector
node 114 or an insole node 106. It does this by determining first if any wired
interfaces exist. This would be the case if sensing system 100 was to be a
collector node 114, since a USB interface will exist to allow for attachment
to
computer 116.
[0055] As a collection node 114, sensing system 100 would initialize the MCU,
COP, GPIO, SPI, IRQ, and set the desired RF transceiver clock frequency by
calling routines MCUInit, GPIOInit, SPilnit, IRQlnit, IRQACK, SPIDrvRead,
and IRQPinEnable. MCUInit is the master initialization routine which turns off
the MCU watchdog, and sets the timer module in order to use BUSCLK as a
reference with a pre-scaling of 32. The state variable gu8RTxMode would be
set to SYSTEM_RESET_MODE, and routines GPIOInit, SPIInit, and IRQlnit
would be called. Next, the state variable gu8RTxMode would be set to
RF_TRANSCEIVER_RESETMODE and the IRQFLAG would be checked to
see if IRQ is asserted. The RF transceiver interrupts would first be cleared,
using SPIDrvRead. Then, RF transceiver would be checked for ATTN IRQ
interrupts. As a final step for MCUInit, calls would be made to
PLMEPhyReset (in order to reset the physical MAC layer), IRQACK (in order
to ACK the pending IRQ interrupt), and IRQPinEnable (to pin Enable, IE, IRQ
CLR, on signal's negative edge).
[0056] Once the collector node process has been initialized, sensing system
100 is ready to receive RF packets from insole nodes 106. This would be
started by creating a RF packet receive queue that is driven by a call back
function on RF transceiver packet receive interrupts. When an RF packet is
received from an insole node 106, a check would first be made to determine if
that packet is from a new insole node 106 or an existing one. If from an
existing insole node 106, RF packet sequence numbers would be checked to
determine continuous synchronization before further analyzing the packet. If
from a new insole node 106, an insole node context state block would be
created and initialized. Above this RF packet session level process for node-
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to-node communication, is the analysis of the RF packet data payload. This
payload would contain the compressed plantar foot pressure profile based on
the current variable pressure analysis map. The first part of the compressed
data would contain a map mask array, which may be structured as follows:
Ox10 I001010011001011011* * * * 1001111011001010101 245 1 234 I
219 225 1 * * * * 1 233 1
start I row 1 1 row 2 1 I row 15 row
m D1 I D2 I D3 I D4 I ID n 1
[0057] where a bit in the FootMaskArray(row 1, row 2, ..., row m) would be set
to one for data that is 255 in value. Each row representation byte would use 6
bits (i.e., the upper two bits would be zero and reserved for future use) to
refer
to each analog-to-digital (A/D) channel, of which there are six in the current
utility. Next, the FootRowMask[k] array would be scanned for non-active
values (i.e., no compression). The location in the FootRowMask[k] array
where to set the no compression value bit would then be determined. This
may be done by first finding out which byte of 16 (which represent rows) in
the
FootRowMask[k] array is the row that has a no compression value in it. The
base value that brings in the row byte of interest would then be removed, and
the remainder may be used as a bit mask and XORed with existing contents,
which could be other no compression values already identified.
[0058] Once the RF packet from an insole node 106 would be decompressed,
the collector node 114 would use the SCITransmitArray routine to send such
decompressed RF packet data (gsRxPacket. pu8Data and
gsRxPacket. u8DataLength) to the connected computer 116 via the USB
interface (not shown). The insole pressure data would then be formatted as
follow:
(Packet headerlOxl0lvalue of A/D CHOlvalue of A/D CHllvalue of A/D
CH21value of A/D CH31
Ivalue of A/D CH61value of A/D CH71value of
A/D CHOlvalue of A/D CH11
(value of A/D CH21value of A/D CH31value of
A/D CH6I* * * * *
[0059] The IEEE 802.15.4 standard (which will be referred to hereinafter as
"802.15.4"), which is the basis for the ZigBee, WirelessHART, and MiWi
specifications, specifies a maximum packet size of 127 bytes and the Time
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Synchronized Mesh Protocol (TSMP) reserves 47 Bytes for operation, leaving
80 Bytes for payload. The 2.4 GHz Industrial, Scientific, and Medical (ISM)
band Radio Frequency (RF) transceiver which may be used herein is
compliant with 802.15.4. It contains a complete 802.15.4 physical layer (PHY)
modem designed for the 802.15.4 wireless standard, which supports peer-to-
peer, star, and mesh networking. It is combined with an MPU to create the
wireless RF data link and network according to various embodiments of the
present invention. The transceiver (e.g., RF module 312) supports both 250
kbps O-QPSK data in 5.0 MHz channels and full spread-spectrum encode
and decode.
[0060] All control, reading of status, writing of data, and reading of data is
done through the sensing system node device's RF transceiver interface port.
The sensing system node device's MPU accesses the sensing system node
device's RF transceiver through interface "transactions" in which multiple
bursts of byte-long data are transmitted on the interface bus. Each
transaction is three or more bursts long depending on the transaction type.
Transactions are always read accesses or write accesses to register
addresses. The associated data for any single register access is always 16
bits in length.
[0061] Receive mode is the state where the sensing system node device's RF
transceiver is waiting for an incoming data frame. The packet receive mode
allows the sensing system node device's RF transceiver to receive the whole
packet without intervention from the sensing system node device's MPU. The
entire packet payload may be stored in RX Packet RAM and the
microcontroller fetches the data after determining the length and validity of
the
RX packet.
[0062] The sensing system node device's RF transceiver waits for a preamble
followed by a Start of Frame Delimiter. From there, the Frame Length
Indicator is used to determine the length of the frame and calculate the Cycle
Redundancy Check (CRC) sequence. After a frame is received, the sensing
system node device's application determines the validity of the packet. Due to
noise, it is possible for an invalid packet to be reported with either of the
following conditions: a valid CRC and a frame length (0, 1, or 2) and/or an
invalid CRC/invalid frame length.
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[0063] The sensing system node device's application software determines if
the packet CRC is valid and that the packet frame length is valid with a value
of 3 or greater. In response to the interrupt request from the sensing system
node device's RF transceiver, the sensing system node device's MPU
determines the validity of the frame by reading and checking valid frame
length and CRC data. The receive packet RAM port register is accessed
when the sensing system node device's RF transceiver is read for data
transfer.
[0064] The sensing system node device's RF transceiver transmits entire
packets without intervention from the Invention node device's MPU. The
entire packet payload is pre-loaded in TX Packet RAM, the sensing system
node device's RF transceiver transmits the frame, and then the transmit
complete status is set for the sensing system node device's MPU. When the
packet is successfully transmitted, a transmit interrupt routine that runs on
the
sensing system node device's MPU reports the completion of packet
transmission. In response to the interrupt request from the sensing system
node device's RF transceiver, the sensing system node device's MPU reads
the status to clear the interrupt and check successful transmission.
[0065] Control of the sensing system node device's RF transceiver and data
transfers are accomplished by means of a Serial Peripheral Interface (SPI).
Although the normal SPI protocol is based on 8-bit transfers, the sensing
system node device's RF transceiver imposes a higher level transaction
protocol that is based on multiple 8-bit transfers per transaction. A singular
SPI read or write transaction comprises an 8-bit header transfer followed by
two 8-bit data transfers. The header denotes access type and register
address. The following bytes are read or write data. The SPI also supports
recursive "data burst" transactions, in which additional data transfers can
occur. The recursive mode is primarily intended for packet RAM access and
fast configuration of the sensing system node device's RF transceiver.
[0066] When the sensing system determines that it is to operate in an insole
mode, it will reset its state flag, FootStepPacketRecvd, and will call its
MLMERXEnableRequest routine while enabling a LOW_POWER WHILE state.
The insole node 106 will then wait 250 milliseconds for a response from the
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collector node 114 to determine whether a default full insole electrode scan
will be done or a mapped electrode scan will be initiated. In the case of a
mapped electrode scan, the collector node send the appropriate electrode
scan mapping configuration data. Electrode scanning is performed by the
FootScan routine, where the FootDataBufferlndex is initialized and rows are
activated, by enabling MCU direction mode for output [PTCDD_PTCDDN =
Output] and bringing the associated port line low[PTCD_PTCD6 = 0]. As
each row is activated based on the electrode scanning map, the columns
which are attached to the MCU analog signal ports will sample and read the
current voltage on the column lines and convert them into digital form which
is
the plantar foot pressure across that selected row. All rows may be
sequentially scanned and the entire process repeated until a reset condition
or inactivity power-down mode.
[0067) The plantar foot pressure data is compressed by clearing the bit map
mask array, which may be structured as follows.
1 0x10 1001010011001011011 * * * 1001111011001010101 245 1 234 1 219
225 1 * * * 1 233 1
I start 1 row 11 row 2 1 * * * 1 row 15 1 row 16 1 * * * row N
1Data1IData2IData31 * * * 1DataN1
[0068] This is where a bit in the FootMaskArray [k] is set to one for data
that is
no compression in value. Each row representation byte uses 6 bits (i.e., the
upper two bits would be zero and reserved for future use) to refer to each A/D
channel, of which there are six. To set the compression bit, a call is made to
the routine FootsetMask with parameters Foot xowMaskIndex and MaskValue
set accordingly. Then, based on Maskvalue, an XOR operation is performed
on FootxowMask [R] with a selected mask value { 0x01; 0x02; 0x04; 0x08;
0x10; 0x20; }.
[0069) Several variables such as Foot SendNumByt e s and FootDataBuf ferIndex
are used to prepare 802.15.4 RF packets gsTxPacket. gau8TxnataBuf fer [I for
sending using the compressed data in FootDataBuffer [ i. The RF packets
are sent using the RFSendRequest (&gsTxPacket) routine. This routine checks
to see if gu8RTxMode is set at IDLE-MODE and uses gsTxPacket as a pointer
to call the RAMDrvWriteTx routine, which then calls SPIDrvRead to read the RF
transceiver's TX packet length register contents. Using this contents, mask
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length setting may be updated with 2 added 2 for CRC and 2 for code bytes.
A call is made to SPIDrvwrite to update the TX packet length field. Next, a
call to SPIC1earRecievestatReg is made to clear the status register followed
by a call to sPlclearRecieveDataReg to clear the receive data register to make
the SPI interface ready for reading or writing.
[0070] With the SPI interface ready, a call is made to SPISendChar sending a
OxFF character which represents the 1st code byte. Next,
SPIWaitTransferpone is called to verify the send is done.
[0071] Now, SPISendChar is called again to send a Ox7E byte, which is the
second code byte and then the sPlwaitTransferpone is called again to verify
the send is done. With these code bytes sent, the rest of the packet is sent
using a for loop where psTxPkt->u8 Data Length+ 1 are the number of iterations
to a series of sequential to SPISendChar, SPIWaitTransferpone,
SPIC1earRecieveDataReg. Once this is done, the RF transceiver is loaded
with the packet to send. The ANTENNA SWITCH is set to transmit, the
LNA_ON mode enabled and finally a RTXENAssert call made to actually send
the packet.
[0072] In this manner, by using continuous two-dimensional pressure sensing
grids with variable mapping capability, a three-dimensional, real-time plantar
pressure may be obtained and wirelessly transmitted to a remote location for
analysis and display. Further details regarding the programming of sensing
system 100 in the manner described above may be found in Wireless Sensing
Triple Axis Reference Design Designer Reference Manual, Document
Number ZSTARRM, Rev. 3, 01/2007, and Simple Media Access Controller
(SMAC) User's Guide, Document Number SMACRM, Rev. 1.2, 04/2005, each
of which is a publication of Freescale Semiconductor, Inc. and is incorporated
herein by reference.
[0073] Referring now to FIG. 8, there is shown a first electrode grid layer
800
of a transducer according to another embodiment of the present invention.
Layer 800 is comparable to layer 308 shown in FIG. 3. In this case, however,
a plurality of lateral grid members 802 are electrically coupled to RF module
312, as are a plurality of longitudinal grid members 804.
[0074] FIG. 9 illustrates a second electrode grid layer 900 which may be used
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with the first electrode grid layer 800. Layer 900 is comparable to layer 310
shown in FIG. 3. In this case, however, the plurality of longitudinal members
902 are coupled to RF module 312, and cooperate with the first electrode grid
layer 800 and conductive foam layer 302 (not shown in FIGS. 8 or 9) to sense
pressure at a plurality of points of interest along the user's feet.
[0075] FIGS. 1OA-1 OF illustrate in schematic format portions of an RF module
312 which may be used with the first and second electrode grid layers shown
in FIGS. 8 and 9. In FIG. 10A, a portion of the schematic relating to a
flexible
PCB connection 1000 is shown. Rows and columns of the electronic grids in
the mapped array may be coupled to the RF module 312. FIG. 10B illustrates
a portion of the schematic relating to a battery 1002. A suitable battery may
comprise a Model No. BK-877, with a CR2450 Coin Cell Retainer SMD made
of phosphor bronze, nickel finished contacts, and a Mylar battery insulator.
[0076] Referring now to FIG. 1 OC, there is shown a portion of the schematic
relating to a triple-axis accelerometer 1004 according to embodiments of the
present invention. One exemplary accelerometer 1004 may be the model
MMA7260QT 1.5g - 6g Three Axis Low-g Micromachined Accelerometer
manufactured by Freescale Semiconductor, Inc. of Tempe, Arizona USA.
This low cost capacitive micromachined accelerometer features signal
conditioning, a 1-pole low pass filter, temperature compensation and g-Select
which allows for the selection among 4 sensitivities. Zero-g offset full scale
span and filter cut-off are factory set and require no external devices. It
includes a Sleep Mode that makes it ideal for handheld battery powered
electronics.
[0077] Accelerometer 1004 is a surface-micromachined integrated-circuit
accelerometer. The device consists of two surface micromachined capacitive
sensing cells (g-cell) and a signal conditioning ASIC contained in a single
integrated circuit package. The sensing elements are sealed hermetically at
the wafer level using a bulk micromachined cap wafer.
[0078] The g-cell is a mechanical structure formed from semiconductor
materials (polysilicon) using semiconductor processes (masking and etching).
It can be modeled as a set of beams attached to a movable central mass that
move between fixed beams. The movable beams can be deflected from their
rest position by subjecting the system to an acceleration.
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[0079] As the beams attached to the central mass move, the distance from
them to the fixed beams on one side will increase by the same amount that
the distance to the fixed beams on the other side decreases. The change in
distance is a measure of acceleration.
[0080] The g-cell beams form two back-to-back capacitors. As the center
beam moves with acceleration, the distance between the beams changes and
each capacitor's value will change, (C = A/D). Where A is the area of the
beam, E is the dielectric constant, and D is the distance between the beams.
[0081] The ASIC uses switched capacitor techniques to measure the g-cell
capacitors and extract the acceleration data from the difference between the
two capacitors. The ASIC also signal conditions and filters (switched
capacitor) the signal, providing a high level output voltage that is
ratiometric
and proportional to acceleration.
[0082] The g-Select feature allows for the selection among 4 sensitivities
present in the device. Depending on the logic input placed on pins 1 and 2,
the device internal gain will be changed allowing it to function with a 1.5g,
2g,
4g, or 6g sensitivity (Table 1 below). This feature is ideal when a product
has
applications requiring different sensitivities for optimum performance. The
sensitivity can be changed at anytime during the operation of the product.
The g-Selectl and g-Select2 pins can be left unconnected for applications
requiring only a 1.5g sensitivity as the device has an internal pull-down to
keep it at that sensitivity (800mV/g).
Table 1. g-Select Pin Descriptions
g-Select2 g-Selectl g-Range Sensitivity
0 0 1.5g 800 mV/g
0 1 2g 600 mV/g
1 0 4g 300 mV/g
1 1 6g 200 mV/g
[0083] Accelerometer 1004 may provide a Sleep Mode that is ideal for battery
operated products. When Sleep Mode is active, the device outputs are turned
off, providing significant reduction of operating current. A low input signal
on
pin 12 (Sleep Mode) will place the device in this mode and reduce the current
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to 3 pA typ. For lower power consumption, it is recommended to set g-
Select1 and g-Select2 to 1.5g mode. By placing a high input signal on pin 12,
the device will resume to normal mode of operation.
[0084] Accelerometer 1004 also contains onboard single-pole switched
capacitor filters. Because the filter is realized using switched capacitor
techniques, there is no requirement for external passive components (i.e.,
resistors and capacitors) to set the cut-off frequency.
[0085] Ratiometricity simply means the output offset voltage and sensitivity
will scale linearly with applied supply voltage. That is, as supply voltage is
increased, the sensitivity and offset increase linearly; as supply voltage
decreases, offset and sensitivity decrease linearly. This is a key feature
when
interfacing to a microcontroller or an A/D converter because it provides
system level cancellation of supply induced errors in the analog to digital
conversion process. Offset ratiometric error can be typically >20% at VDD =
2.2 V. Sensitivity ratiometric error can be typically >3% at VDD = 2.2 V.
Table 2. Pin Descriptions
Pin No. Pin Name Description
1 g-Selectl Logic input pin to select g level.
2 g-Select2 Logic input pin to select g level.
3 VDD Power Supply Input
4 VSS Power Supply Ground
5-7 N/C No internal connection. Leave unconnected.
8-11 N/C Unused for factory trim. Leave unconnected.
12 Sleep Mode Logic input pin to enable product or Sleep Mode.
13 ZOUT Z direction output voltage.
14 YOUT Y direction output voltage.
15 XOUT X direction output voltage.
16 N/C No internal connection. Leave unconnected.
[0086] The VDD line should have the ability to reach 2.2 V in < 0.1 ms as
measured on the device at the VDD pin. Rise times greater than this most
likely will prevent start up operation. Physical coupling distance of the
accelerometer to the microcontroller should be minimal. The flag underneath
the package is internally connected to ground. It is not recommended for the
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flag to be soldered down. A ground plane should be placed beneath the
accelerometer 1004 to reduce noise. The ground plane should be attached to
all of the open ended terminals. An RC filter with a 1.0 kQ resistor 1006 and
a
0.1 pF capacitor 1008 may be used on the outputs of the accelerometer 1004
in order to minimize clock noise (from the switched capacitor filter circuit).
PCB layout of power and ground should not couple power supply noise.
Accelerometer and microcontroller should not be a high current path. AID
sampling rate and any external power supply switching frequency should be
selected such that they do not interfere with the internal accelerometer
sampling frequency (11 kHz for the sampling frequency). This will prevent
aliasing errors. PCB layout should not run traces or vias under the QFN part.
This could lead to ground shorting to the accelerometer flag.
[0087] Further details regarding accelerometer 1004 may be found in
Freescale Document Number: MMA7260QT, Rev 5, 03/2008, which is
incorporated herein by reference.
[0088] Referring now to FIGS. 1OD-1 OF, there are shown portions of the
schematic relating to a microcontroller 1010 and transceiver 1012, including a
balun 1014 and crystal oscillator 1016, which may be used according to
embodiments of the present invention. One exemplary platform incorporating
both functions may be the model MC13213 ZigBeeT""- Compliant Platform -
2.4 GHz Low Power Transceiver for the IEEE 802.15.4 Standard plus
Microcontroller manufactured by Freescale Semiconductor, Inc. of Tempe,
Arizona USA.
[0089] The MC1321x family is Freescale's second-generation ZigBee platform
which incorporates a low power 2.4 GHz radio frequency transceiver and an
8-bit microcontroller into a single 9x9x1 mm 71-pin LGA package. The
MCI 321x solution can be used for wireless applications from simple
proprietary point-to-point connectivity to a complete ZigBee mesh network.
The combination of the radio and a microcontroller in a small footprint
package allows for a cost-effective solution.
[0090] The MC1321x contains an RF transceiver which is an 802.15.4
compliant radio that operates in the 2.4 GHz ISM frequency band. The
transceiver includes a low noise amplifier, 1 mW nominal output power, PA
with internal voltage controlled oscillator (VCO), integrated transmit/receive
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and decoding. The MC1321x also contains a microcontroller based on the
HCSO8 Family of Microcontroller Units (MCU), specifically the HCSO8 Version
A, and can provide up to 60KB of flash memory and 4KB of RAM. The
onboard MCU allows the communications stack and also the application to
reside on the same system-in-package (SIP). The MC13213 contains 60K of
flash and 4KB of RAM and is also intended for use with the Freescale fully
compliant 802.15.4 MAC and the fully ZigBee compliant Freescale BeeStack.
Table 3. Pin Function Description
Pin # Pin Name Type Description Functionality
1 PTA3/KBI1 P3 Digital Input/Output MCU Port A Bit
3/Keyboard Input
Bit 3
2 PTA4/KBI1 P4 Digital Input/Output MCU Port A Bit
4/Keyboard Input
Bit 4
3 PTA5/KBI1 P5 Digital Input/Output MCU Port A Bit
5/Keyboard Input
Bit 5
4 PTA6/KBI1 P6 Digital Input/Output MCU Port A Bit
6/Keyboard Input
Bit 6
PTA7/KBI1 P7 Digital Input/Output MCU Port A Bit
7/Keyboard Input
BR 7
6 VDDAD Power Input MCU power Decouple to ground.
supply to ATD
7 PTGO/BKGND/MS Digital Input/Output MCU Port G Bit PTGO is output only.
0/Background / Pin is I/O when used
Mode Select as BDM function.
8 PTG1/XTAL Digital MCU Port G Bit Full I/O when not used
Input/Output/Output 1/Crystal as dock source.
oscillator output
9 PTG2/EXTAL Digital MCU Port G Bit Full I/O when not used
Input/Output/Input 2/Crystal as dock source.
oscillator input
CLKO Digital Output Modem Clock Programmable
Output frequencies of 16
MHz, 8 MHz, 4 MHz, 2
MHz, 1 MHz, 62.5
kHz, 32.786+ kHz
(default), and 16.393+
kHz.
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Table 3. Pin Function Description (cont)
Pin # Pin Name Type Description Functionality
11 RESET Digital Input/Output MCU reset.
Active low
12 PTCO/TXD2 Digital Input/Output MCU Port C Bit
0/SCI2 TX data
out
13 PTC1/RXD2 Digital Input/Output MCU Port C Bit
1/SCI2 RX data
in
14 PTC2/SDA1 Digital Input/Output MCU Port C Bit
1/IIC bus data
15 PTC3/SCL1 Digital Input/Output MCU Port C Bit
1/IIC bus clock
16 PTC4 Digital Input/Output MCU Port C Bit 4
17 PTC5 Digital Input/Output MCU Port C Bit 5
18 PTC6 Digital Input/Output MCU Port C Bit 6
19 PTC7 Digital Input/Output MCU Port C Bit 7
20 PTEO/TXD1 Digital Input/Output MCU Port E Bit 0
/ SCI1 TX data
out
21 PTE1/RXD1 Digital Input/Output MCU Port E Bit
1/ SCI1 RX data
in
22 VDDD Power Output Modem regulated Decouple to ground.
output supply
voltage
23 VDDINT Power Input Modem digital 2.0 to 3.4 V. Decouple
interface supply to ground. Connect to
Battery.
24 GPIO51 Digital Input/Output General Purpose See Footnote 1
Input/Output 5.
25 GPIO61 Digital Input/Output Modem General See Footnote 1
Purpose
Input/Output 6
26 GPIO71 Digital Input/Output Modem General See Footnote 1
Purpose
Input/Output 7
27 XTAL1 Input Modem crystal Connect to 16 MHz
reference crystal and load
oscillator input capacitor.
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Table 3. Pin Function Description (cont.)
Pin # Pin Name Type Description Functionality
28 XTAL2 Input/Output Modem crystal Connect to 16 MHz
reference crystal and load
oscillator output capacitor. Do not load
this pin by using it as a
16 MHz source.
Measure 16 MHz
output at CLKO,
programmed for 16
MHz.
29 VDDLO2 Power Input Modem L02 Connect to VDDA
VDD supply externally.
30 VDDLO1 Power Input Modem LO1 Connect to VDDA
VDD supply externally.
31 VDDVCO Power Output Modem VCO Decouple to ground.
regulated supply
bypass
32 VBATT Power Input Modem voltage Decouple to ground.
regulators' input Connect to Battery.
33 VDDA Power Output Modem analog Decouple to ground.
regulated supply Connect to directly
output VDDLOI and
VDDLO2 externally
and to PAO_P and
PAO_M through a bias
network.
34 CT Bias RF Control Modem bias When used with
Output voltage/control internal T/R switch,
signal for RF provides ground
external reference for RX and
components VDDA reference for
TX. Can also be used
as a control signal with
external LNA, antenna
switch, and/or PA (high
level is VDDA).
35 RFIN_M RF Input (Output) Modem RF When used with
input/output internal T/R switch, this
negative is a bi-directional RF
port for the internal
LNA and PA
36 RFIN_P RF Input (Output) Modem RF When used with
input/output internal T/R switch, this
positive is a bi-directional RF
port for the internal
LNA and PA
37 NC Not used May be grounded or
left open
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Table 3. Pin Function Description (cont.)
Pin # Pin Name Type Description Functionality
38 PAO_P RF Output Modem power Open drain. Connect
amplifier RF to VDDA through a
output positive bias network when
used with external
balun. Not used when
internal T/R switch is
used.
39 PAO_M RF Output Modem power Open drain. Connect
amplifier RF to VDDA through a
output negative bias network when
used with external
balun. Not used when
internal T/R switch is
used.
40 SM Input Test Mode pin Must be grounded for
normal operation
41 GPIO41 Digital Input/Output General Purpose See Footnote 1
Input/Output 4.
42 GPIO31 Digital Input/Output Modem General See Footnote 1
Purpose
Input/Output 3
43 GPIO2 Test Point MCU Port E Bit Internally connected
6/Modem pins. When
General Purpose gpio_att_en, Register
Input/output 2 9, Bit 7 = 1, GPIO2
functions as a "CRC
Valid" indicator.
44 GPIO1 Test Point MCU Port E Bit Internally connected
7/Modem pins. When
General Purpose gpio_alt_en, Register
Input/Output 1 9, Bit 7 = 1, GPIO1
functions as an "Out of
Idle" indicator.
45 VDD Power Input MCU main power Decouple to ground.
supply
46 ATTN2 Digital Input Active Low See Footnote 2
Attention.
Transitions IC
from either
Hibernate or
Doze Modes to
Idle.
47 PTD2/TPM1CH2 Digital Input/Output MCU Port D Bit
2/TPM1 Channel
2
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Table 3. Pin Function Description (cont.)
Pin # Pin Name Type Description Functionality
48 PTD4/TPM2CH1 Digital Input/Output MCU Port D Bit
4/TPM2 Channel
1
49 PTD5/TPM2CH2 Digital Input/Output MCU Port D Bit
5/TPM2 Channel
2
50 PTD6/TPM2CH3 Digital Input/Output MCU Port D Bit
6/TPM2 Channel
3
51 PTD7/TPM2CH4 Digital Input/Output MCU Port D Bit
7/TPM2 Channel
4
52 PTBO/AD1 PO Input/Output MCU Port B Bit
0/ATD
analogChannel 0
53 PT¾1/AD1 P1 Input/Output MCU Port B Bit
1/ATD analog
Channel 1
54 PTB2/AD1 P2 Input/Output MCU Port B Bit
2/ATD analog
Channel 2
55 PTB3/AD1 P3 Input/Output MCU Port B Bit
3/ATD analog
Channel 3
56 PTB4/AD1 P4 Input/Output MCU Port B Bit
4/ATD analog
Channel 4
57 PTB5/AD1 P5 Input/Output MCU Port B Bit
5/ATD analog
Channel 5
58 PTB6/AD1 P6 Input/Output MCU Port B Bit
6/ATD analog
Channel 6
59 PTB7/AD1 P7 Input/Output MCU Port B Bit
7/ATD analog
Channel 7
60 VREFH Input MCU high
reference voltage
for ATD
61 VREFL Input MCU low
reference voltage
for ATD
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Table 3. Pin Function Description (cont.)
Pin # Pin Name Type Description Functionality
62 PTAO/KBI1 PO Digital Input/Output MCU Port A Bit
0/Keyboard Input
Bit 0
63 PTA1/KBI1 P1 Digital Input/Output MCU Port A Bit
1/Keyboard Input
Bit 1
64 PTA2/KBI1 P2 Digital Input/Output MCU Port A Bit
2/Keyboard Input
Bit 2
65 TEST Test Point For factory test Do not connect
66 TEST Test Point For factory test Do not connect
67 TEST Test Point For factory test Do not connect
68 TEST Test Point For factory test Do not connect
69 TEST Test Point For factory test Do not connect
70 TEST Test Point For factory test Do not connect
71 TEST Test Point For factory test Do not connect
FLAG VSS Power input External package Connect to ground.
flag. Common
VSS
' The transceiver GPIO pins default to inputs at reset. There are no
programmable pull ups on
these pins. Unused GPIO pins should be tied to ground if left as inputs, or if
left unconnected, they
should be programmed as outputs set to the low state.
2 During low power modes, input must remain driven by MCU.
[0091] FIGS. 11 and 12 illustrate a first and a second algorithm which may be
used with transducers according to FIGS. 8, 9 and 1OA-10F. Sensing system
100 may use an exponential moving average filter in conjunction with a sliding
window boxcar style integrator to per-process digitize real-time acceleration
data for all three dimensions Ax, Ay, Az. The accumulated acceleration data
may be analyzed to identify unique motion artifacts such as strides and steps
and their respective directions. Reference frames may be created to provide
variable time sequences of motion artifacts. The XPU conductive foam allows
for gating reference frames such as the start of step (i.e., a standing
position -
rising foot to start stride) and the end of step (i.e., a falling foot - to
standing
position). A general algorithm which may be incorporated and implemented
as embedded software running on processors supporting the sensing system
100 is as follows:
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[0092] A(x, y, z)SigAccum = i * IIA(x, y, z)[i]I * Aw(x, y, z)[i]
A(x, y, z)SigScale ;_,
[0093] Alternative embodiments of that algorithm are shown in FIG. 11. In
either case, the results of those algorithms are summed and integrated in the
manner shown in FIG. 12. The resultant approximates the following:
[AxNegAccum*WxN+AxPosAccum*WXP
AyNegAccum*WyN+AyPosAccum*WyP
M(-Ax,-Ay,-Az, t) _ +
AzNegAccum*WzN+AzPosAccum*WzP]
*
[1 +eXp(-t)].
[0094] Sensing system 100 is, thus, sensitive enough to measure the plantar
pressures differences between adult male and female foot pressures under
the longitudinal arch. Under the mid-foot, females have reduced peak foot
pressures during standing. Also, for females, there is a correlation between
body weight and foot pressures under the longitudinal arch of a female's feet
in walking. This allows for sensing system 100 to analyze the ligamentous
structure which results to some degree in collapse of the longitudinal arch
during weight bearing phase of walking.
[0095] Sensing system 100 is able to perform similar foot function analysis
during running. Specifically, sensing system 100 may analyze mid-foot
loading as well as the amount of rear-foot rotation which is more apparent in
female runners as compared to male runners. In the case for children,
contrary to adults, body weight is identified to be of major influence on the
magnitude of the pressures under the feet of children and between boys and
girls no differences in the foot pressure or relative load patterns are
present.
Sensing system 100 may be used in such cases periodically to analyze
potential walking/running/gait related issues in children as they develop.
This
may provide data that may help in development of proper in-soles and other
support structures to aid in the renormalizing walking/running/gait related
issues.
[0096] Sensing system 100 may also help determine the cause of pain and
lower extremity complaints for overweight and obese persons. The system's
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ability to analyze plantar pressure analysis may provide additional insight
into
pain and lower extremity complaints. Plantar pressure differences between
obese and non-obese adults during standing and walking indicates that the
overweight persons have an increase in the forefoot width to foot length
ratio.
This is due to the broadening of the forefoot under increased weight loading
conditions. Even though there is the increased load bearing contact area with
the foot against the ground, overweight persons have substantially higher foot
pressures under the heel, mid-foot, and forefoot during standing, walking and
running.
[0097] Sensing system 100 measures larger foot pressures under the mid-foot
during standing periods for the obese women as compared to the obese men.
There is a major influence of body weight on the flattening of the arch is the
consequence of the inherent reduced strength of the ligaments in natively in
women's feet. This may contribute to lower extremity pain and discomfort in
these obese persons and their choice of footwear and predisposition to
participation in activities of daily living such as walking and running. For
walking, the forefoot pressures as well as the forefoot contact area are
substantially increased for obese women. Sensing system 100 may analyze
and monitor this increased forefoot plantar pressures, which in most cases
result in foot discomfort and hinders these obese women in participating
normally in physical activity.
[0098] Sensing system 100 may also help runners manage overuse injuries.
This affects more than half of active runners each year and causes them to
stop running. The causes of such injuries include variation/distribution of
body dimensions to optimize training, rear-foot movement, kinetic, and
strength variables. Biomechanical parameters such as real-time foot
pressures may be identified and analyzed by sensing system 100 to help
identify key properties of athletic footwear in providing overuse injury
protection and performance enhancement. Such parameters may be mid-
sole material properties, which may provide information about footwear
production tolerances.
[0099] Sensing system 100 may also measure and record rear-foot rotation,
foot pressure patterns, and shock absorption properties running shoes/athletic
footwear to analyze shoe characteristics which may help reduce the risk of
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overuse injuries. Thus, sensing system 100 may be used to evaluate shoe fit
and comfort during running on various terrain types. The system's long term
monitoring and archive capability allows for analyzing deterioration of shoe
properties over time and use.
[00100] Sensing system 100 may also record in real-time in-shoe pressure
during running and training and provides information of the interaction
between footwear and foot mechanics of the person wearing them. Over
rotation during running and training is responsible for many overuse injuries.
Typically, restriction of excessive rear-foot motion and improved shock
absorption may reduce the risk of running and training injuries. The
determination and measurement of subtalar joint rotation are critical the
evaluation of running and training shoes. Capturing real-time subtalar joint
rotation measurement data is one of the main features of the sensing system.
[00101] Sensing system 100 may also determine wear and tear with the
assessment monitoring and recording features. It has the ability to detect,
capture and analyze foot pressure data wirelessly and in real-time variations
in rear-foot motion combined with the differences in mid-sole properties to
determine shoe cushioning differences to categorize overall stiffness of the
shoe. These stiffness characteristic tend to alter the wears landing patterns
to
elicit lower impact forces. This allows for constructing biomechanical
assessments that are beneficial for the wearer using such shoes to minimize
injuries resulting from repeated impact loading. The wear of the insole will
be
displayed outside the shoe as green, yellow, red graphic display indications
to
illustrate the degree of shoe wear.
[00102] Sensing system 100 may also perform weight and power assessment
by foot zones (e.g., heel, mid-foot, and forefoot). Sensing system 100 has
capability to detect, capture and analyze foot pressure data wirelessly and in
real-time relating to vertical ground reaction force patterns and materials
characterization of running shoes with advanced cushioning column systems
during walking, running, and/or training.
[00103] Sensing system 100 may also detect changes in foot sole pressure
patterns during activity so that a subject's footfall changes/patterns may be
determined during a specific event and correlated against multiple events
(e.g., practice versus game activity). To be able to detect slight variations
of
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pressure over time - like the loss of fluid within a running race. The ability
to
transmit this information wirelessly to a collection site or monitor.
[00104] Sensing system 100 may also detect changes in power patterns during
a specific sporting event and calculate power/energy requirements against
expected output. Energy vector analysis versus current and expected output.
[00105] Sensing system 100 may also provide the monitoring and analysis
required for dance and kinesiology applications, interactive dance movements
(e.g., learn to dance as a game application where a subject is signaled in one
way when they are taking the right steps and another when they are wrong.
[00106] Sensing system 100 may also provide the monitoring and analysis
required for industrial applications to determine warehouse personnel
effectiveness, such as allowable personnel movements measured against
assembly efficiency, the determination of specific individuals locations
(since
GPS is not very effective and expensive to deploy indoors, especially in a
warehouse setting), to guard against entry into certain areas where they are
prohibited such as hazard and/or security areas, and in applications where
there are employee health care incentives for weight loss and health
maintenance.
[00107] Sensing system 100 may also may augment gaming interfaces to
supplement videogames such as PlayStation PS3 and XBox 360 gaming
console. This would add an extra dimension to how one interacts with
videogames running on these game consoles. Foot pressure activity detected
during jumping, walking or running are combined with foot orientation and
location data to provide enhance interactivity to the regular popular
videogames, allowing for intuitive game play such as kicking or blocking in a
fighting game.
[00108] A backend server processing option of sensing system 100 may also
be able to collect large groups of insole monitors that would represent a
field
of players involved in sporting games (e.g., football, soccer, basketball and
the like). This may be implemented as a website for remote analysis
supporting peer review type applications. Sensing system 100 may also be
able to capture the data over a large field of reference (e.g., sports field,
field
of battle, long distance run) by a specific signature for an individual sole,
by
person (i.e., two soles) or by collection of individuals. Sensing system 100
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would, thus, enable download of all of this information upon arrival, within a
transmission zone, to a web interface that creates a post event re-simulation
to be stored, compared and rated by peer web garners.
[00109] The backend server processing option is also able to collect large
groups of the insole monitors that would represent a field of players involved
in sporting games (e.g., football, soccer, basketball, and the like). This may
allow for the creation of game strategy analysis program by using correlation
analysis using real-time and archived in-sole data. With additional data
input,
such as real-time video, it would be readily apparent to those of ordinary
skill
in the art that enhanced dynamic game strategy adjustment programs would
be possible.
[00110] Sensing system 100 may also be able to detect slight variations of
foot
pressure over time caused by conditions such as the loss of fluid within a
running race, the change in pressure in a medical or rehabilitation
environment, the change in pressure during an operating process (e.g.,
driving a car) where pressure may indicate that the operator is fit to
continue.
With the monitoring and archive capabilities of sensing system 100, programs
may be constructed to manage long-term foot pressure variation analysis as
previously mentioned.
[00111] Sensing system 100 may also be implemented in a floor mat type
arrangement for a car as the key mechanism for vehicle speed operation. It
may also be used in applications to assist in small motor control where the
operator is incapable, either due to injury or birth defect, of applying
pressure
to hand or foot operating systems. In both cases mentioned, wireless support
for sensing system 100 allows for six-degrees of motion.
[00112] Yet another embodiment of sensing system 100 is one in which energy
is "harvested". That is, piezoelectric fiber composites can convert mechanical
energy and into electrical energy. Alternative embodiments of sensing system
100 may be used to leverage the composite nature of such piezoelectric fiber
composites, because they are lighter and more flexible than bulk piezoelectric
ceramics. Such piezoelectric fiber composites are capable of producing 50 V
at a "stepping" frequency of 3 Hz. This could charge a battery at a 5 milliamp
rate. Piezoelectric fiber composites may be shaped within insoles of various
embodiments of the present invention, running from heel to toe. Piezoelectric
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fiber composites may also run in parallel, to accumulate the desired electric
power. As a result, sensing system 100 may leverage potted and laminated
implementations in conjunction with polyethylene sheets for insole design.
[00113] Such sensing systems 100, including piezoelectric fiber composites
would be very durable and have a fatigue life time which is greater than 200
million cycles, with no degradation in the piezoelectric characteristics. The
piezoelectric fiber composites used herein are 250 microns in diameter with
variable lengths. A charging circuit could be added to provide voltage
limiting
and conditioning capabilities for a battery charging application. The
particular
battery technology which would be useful for sensing system 100 would be a
function of its application. For example, gaming, sports and health monitoring
applications might require a rechargeable Lithium-Polymer (Li-Poly) battery.
In such cases, a 1 mm insole layer of piezoelectric fiber composites would be
appropriate for battery recharging implementations.
[00114] While various embodiments of the present invention have been
described above, it should be understood that they have been presented by
way of example only, and not limitation. Thus, the breadth and scope of the
present invention should not be limited by any of the above-described
exemplary embodiments, but should instead be defined only in accordance
with the following claims and their equivalents.
