United States Patent [19]
`Gaudet et al.
`
`US0060.18705A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,018,705
`Jan. 25, 2000
`
`[54] MEASURING FOOT CONTACT TIME AND
`FOOT LOFT TIME OF A PERSON IN
`LOCOMOTION
`
`5,323,650 6/1994 Fullen et al. .............................. 73/172
`5,343,445 8/1994 Cherdak ......
`.... 36.8/10
`5,357,696 10/1994 Gray et al.
`... 36/136
`5,361,778 11/1994 Seitz ........................................ 128/779
`5,422,628 6/1995 Rodgers .................................. 340/573
`-
`-
`[75] Inventors: º 5,437,289 8/1995 fºi . 128/779
`Oliver Auleboro all of Mass
`5,452,269 9/1995 Che?dak ----------
`.... 36.8/10
`2
`2
`-
`5,485,402
`1/1996 Smith et al
`. 364/566
`[73] Assignee: Personal Electronic Devices, Inc.,
`sº º: * ai.
`º ;
`Wellesley Hills, Mass.
`5,583,776 12/1996 Levi et al. ...
`. 364/450
`5,623,944 4/1997 Nashner ......
`... 128/779
`5,636,146 6/1997 Flentovet al. ...
`. 364/569
`5,720,200 2/1998 Anderson et al. ..
`... 73/172
`5,724,265 3/1998 Hutchings ............................... 364/565
`Primary Examiner—Marc S. Hoff
`Assistant Examiner—Hien Vo
`Attorney, Agent, or Firm—Wolf, Greenfield & Sacks, P.C.
`[57]
`ABSTRACT
`The time period that a foot is in contact with the ground
`during a stride taken by a user, and the period that the foot
`References Cited
`is not in contact with the ground between strides taken by the
`U.S. PATENT DOCUMENTS
`user are determined by processing and analyzing the output
`------
`signal of an accelerometer. The accelerometer is mounted on
`3,972,038 7/1976 Fletcher et al. ......................... 340/189
`the user such that its acceleration sensing axis senses accel
`3,974,491
`8/1976 Sipe ...
`... 340/272
`eration in a direction substantially parallel to the bottom of
`4,408,183 10/1983 Wills .................
`... 340/323
`º: !|º sº et al.
`--- ?º the user’s foot. The output of the accelerometer is high-pass
`2 * ~ * >
`oal ºr ----
`filtered, amplified, and fed to the input of a micro-controller,
`i. †: º:º º which monitors the signal for positive and negative signal
`4,651446 3/1987 Yukawa et al. ........................... 36/132
`spikes that are indicative, respectively, of the moment that
`4,745,564 5/1988 Tennes et al. ....
`... 364/566
`the foot of the user leaves the ground and the moment that
`4,763,287 8/1988 Gerhaeuser et al.
`... 364/561
`the foot impacts with the ground. By measuring time inter
`4,771,394 9/1988 Cavanagh ................................ 364/561
`vals between these positive and negative spikes, average
`4,774,679 9/1988 Carlin ...................................... 364/550
`“foot contact times” and “foot loft times” of the user may be
`4,814,661
`3/1989 Ratzlaff et al.
`... 310/328
`calculated. To derive the pace of the user, the average foot
`4,830,021 5/1989 Thornton .......
`... 128/707
`contact time is multiplied by a first constant if it is less than
`i. º º ------
`---- sº 400 milli-seconds (ms) and is multiplied by a second con
`Sossois 7/1991 Kato º ai".
`... 364/561
`stant if it is greater than 400 ms. This pace value may, in
`sisoo) 2/1993 Roost ....
`... 73/865.4
`turn, be used to calculate the distance traveled by the user.
`5,269,081 12/1993 Gray .......................................... 36/136
`5,285,586 2/1994 Goldston et al. ......................... 36/137
`
`[21] Appl. No.: 08/942,802
`[22] Filed:
`Oct. 2, 1997
`[51] Int. Cl." ............................ G01C 22/00; G04E 1000
`[52] U.S. Cl. .......................... 702/176; 702/141; 702/160;
`702/142; 368/10; 235/105
`[58] Field of Search ..................................... 702/160, 176,
`702/144, 141, 142, 149; 368/10; 235/105
`
`[56]
`
`
`
`38 Claims, 13 Drawing Sheets
`
`FITBIT, INC. v. LOGANTREE LP
`Ex. 1016 / Page 1 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 1 of 13
`
`6,018,705
`
`FIG. 1
`32
`|USER INIEFFACE
`
`
`
`70
`/
`
`25A
`
`28
`
`NETWORK PROCESSING CIRCUITRY
`
`25B
`AUDIO 0R WIBRATIONAL
`INDICATOR
`
`20A
`
`22
`
`24
`
`FOOT CONTACT TIMEIFOOT LOFT TIME
`GENERATOR
`
`HEART RAIE
`MONITOR
`
`RESPIRATORY
`MONITOR
`
`*\|FOOT CONIAC IIEF0 tº IIf
`GENERATOR
`
`Ex. 1016 / Page 2 of 27
`
`

`
`U.S. Patent
`U.S. Patent
`
`Jan. 25, 2000
`Jan. 25,2000
`
`Sheet 2 of 13
`Sheet 2 of 13
`
`6,018,705
`6,018,705
`
`
`
`Ex. 1016/ Page 3 of 27
`
`Ex. 1016 / Page 3 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 3 of 13
`
`6,018,705
`
`FIG. 3
`58
`USER INIERFACE
`
`72
`/
`
`54
`
`
`
`
`
`FOOT CONTACT TIMEIFOOT LOFT TIME
`GENERATOR
`
`AUDIO 0R WIBRATIONAL
`INDICATOR
`
`FIG. 4
`
`20 /
`
`ACCELEROMETER
`
`
`
`HIGHPASS
`FILTER
`
`AMPLIFIER
`CIRCUIT
`
`40
`
`LOW POWER
`MICROCONTROLLER
`
`
`
`
`
`
`
`
`
`Ex. 1016 / Page 4 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 4 of 13
`
`6,018,705
`
`|I9-8
`
`HETTOHIN00080IH
`
`
`
`SHE WII (NW 01W IM
`
`
`
`
`
`
`
`
`
`
`
`28
`
`Ex. 1016 / Page 5 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 5 of 13
`
`6,018,705
`
`FIG. 5
`
`1.82 L_2.08 || 2.34
`1.55 |
`º, 11",") 13.1% ”* 1.53 ° 1.95
`2.21
`TIME (SECONDS)
`
`• * * * * * * * * * * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * * * * * * * * * * * * * * * * * * * * - - - - - - - - - - - - - - -
`
`
`
`-
`
`0.13
`
`-
`
`0.33
`
`-
`
`..]
`
`2.34
`1.55 | 1.82 |_2.08
`1.30 |
`0.55 * "I'm
`.43
`1.63 T 1.95
`2.2
`1
`2.
`1
`IIHE ISECONDS)
`
`Ex. 1016 / Page 6 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 6 of 13
`
`6,018,705
`
`
`
`- - - - - - - - - - - - - -
`
`0
`0.0 ().2 0.3 0.5 0.5 0.8 0.3 1.1 1.2 1.4 1.5 1.] 1.8 2.0 2.1 2.3 2.4
`IIME (SECONDS)
`
`200---........................................................... ; * * * * * * - - - - - - - - - - ? 8 + + º- + - - - - - - - - - - - a s : * * * * * - - - - - - - - * * *
`
`|W
`
`{{M-sº
`
`150–4..…..:/------------------------ - - - - - - - - - - - ----------- | - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
`
`º
`
`WALUE
`
`100–.......................................}}....................::• * * * - - - - - - - - - - - --> * * * * * * - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
`
`50–............................................................. : * * * * - - - - - - - - - - -> * * * * * * * - - - - - - - - - - * * * * * * - - - - - - - - - - - - -
`
`IN
`:
`i
`--~~
`0
`0.0 0.2 0.3 0.5 0.6 0.8 0.8 1.1 1.2 1.4 1.5 1.] 1.9 2.0 2.2 2.3 2.5
`TIME (SECONDS)
`
`Ex. 1016 / Page 7 of 27
`
`

`
`U.S. Patent
`
`Jan. 25,2000
`
`Sheet 7 of 13
`
`6,018,705
`
` .
`
`.
`173017.5317‘B817.71177217.9017'9B18.0E1B‘“1B.22m‘3o13.38m 751115118 521117018
`IIHE 1SECOMJS1
`
`.7
`
`1 .91
`813.86 B
`
`
`
`7.
`150175111
`
`7.55
`
`17.73
`
`17.81
`
`17.89
`
`17.95
`
`1.
`.7
`1B.01[H21fl.201821H.35lfl
`
`.4
`
`.
`318.5118 581115518
`
`.71
`
`.
`111.8218 B915 .37
`
`TIME (SECONDS)
`
`Ex. 1016/ Page 8 of 27
`
`Ex. 1016 / Page 8 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 8 of 13
`
`6,018,705
`
`FIG. 9
`
`-
`
`-
`
`-
`
`-
`
`..]
`
`*"... tº 1, #3, "'; sº, sº º;" 25.9
`IIME (SECONDS)
`
`.8 | 25.9
`
`25.0
`
`
`
`•
`
`25.
`
`.3
`
`-
`
`*
`
`-
`
`25.5 ..] .. 25.] . .
`. 25.8
`25.9
`ãº, **** #3"; 25.6
`25.7
`25.9
`25.0
`IIME (SECONS)
`
`•
`
`Ex. 1016 / Page 9 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 9 of 13
`
`6,018,705
`
`FIG. 10
`\ I
`
`100 - || DETECT NEGATIVE
`SPIKE EVENT AND
`INCREASE STEPCOUNT
`
`
`
`
`
`102
`
`104
`
`PERFORM Ia FIFO
`SMOOTHING
`
`
`
`
`
`INCREMENT TaSUM
`AND TaSTEPS
`
`
`
`
`
`105
`
`SLEEP FOR MINIMUM
`IC
`
`
`
`
`
`108
`
`DETECI POSITIVE
`SPIKE EVENT
`
`
`
`
`
`110
`
`PERFORM IC FIFO
`SM00THING
`
`
`
`
`
`112
`
`
`
`114
`
`INCREMENT ICSUM
`AND TCSIEPS
`
`SLEEP fº MINIMUM
`C
`
`Ex. 1016 / Page 10 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 10 of 13
`
`6,018,705
`
`FIG. 11
`
`tº
`
`115
`
`
`
`
`
`
`
`
`
`
`
`
`
`118
`
`
`
`120
`
`
`
`122
`
`
`
`
`
`124
`
`125
`
`Y SECOND
`INTERRUPT2
`
`CALCULATE
`TCAVERAGE AND
`RESET ICSUM AND
`ICSTEPS
`
`CALCULATE
`TakWERAGE AND
`RESET TaSUM AND
`TaSTEPS
`
`CALCULAIE
`STEP FREQUENCY
`AND STEPCOUNI
`
`
`
`CALCULATE PACE
`AND DISTANCE
`
`RETURN
`
`Ex. 1016 / Page 11 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 11 of 13
`
`6,018,705
`
`FIG. 12
`
`101
`\ 100,
`READ X-AXIS
`ACCELEROMETER
`
`100B
`
`100C
`
`100D
`
`100E
`
`YES
`
`STOP Ta TIMER
`
`START IC TIMER
`
`STEPCOUNT + +
`
`* ?on?: "...WIES
`(FIFO)
`
`TaSUM=
`TaSUM4IA
`
`TaSTEPS4 +
`
`104A
`
`104B
`
`SLEEP FOR TIME | 106
`EQUAL TO THE
`MINIMUM ALLOWED
`CONTACT IIME
`
`READ X-AXIS
`ACCELEROMETER
`
`108A
`
`-
`
`102B
`
`LASI Ta VALUE
`WITHIN Yº OF
`EACH OTHER2
`
`108B
`
`
`
`
`
`POSITIVE G
`SPIKE EVENI 2
`
`YES
`
`108C
`
`10BE
`
`
`
`YES
`
`
`
`
`
`FIRST AND
`LASI IC VALUE
`WITHIN X% OF
`EACH OTHER2
`
`
`
`FIRST AND
`MIDDLE IC VALUE
`WITHIN X% OF
`EACH OTHER2
`
`SEI MIDDLE IC
`WALUE TO MIDPOINT
`OF FIRST AND
`LAST IC VALUES
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`102C
`
`STOP TC TIMER
`
`START Ta TIMER
`
`
`
`FIRST AND
`MIDDLE Ta VALUE
`WITHIN Yº OF
`EACH OTHER2
`
`SEI MIDDLE Ta
`WALUE TO MIDPOINT
`OF FIRST AND
`LAST Ta VALUES
`
`USE LEASI RECENT Ta
`FOR FUTURE
`CALCULATIONS
`
`102E
`
`108D
`
`USE LEASI RECENI IC
`FOR FUTURE
`CALCULATIONS
`
`112A
`
`1128
`
`
`
`114
`
`
`
`TCSUM
`ICSUMATC
`
`ICSIEPS4 t
`
`SLEEP FOR TIME
`EQUAL TO THE
`MINIMUM ALLOWED
`CONTACT TIME
`
`Ex. 1016 / Page 12 of 27
`
`

`
`U.S. Patent
`
`Jan. 25, 2000
`
`Sheet 12 of 13
`
`6,018,705
`
`FIG. 13
`
`115
`
`115
`
`122A
`
`Y SECOND RIC
`INTERRUPT)
`
`YES
`
`118A
`
`YES
`
`TCAVERAGE
`=7ER07
`
`NO
`
`
`
`
`
`118B
`
`STEPS=
`
`<> STEPCOUNT 82
`
`124A
`
`
`
`ICAVERAGE=
`ICSUM/ICSTEPS
`
`1180
`
`TCAVERAGEx
`400mS2
`
`SET ICSUM=0
`SET ICSTEPS=0
`
`1180
`
`SLOPE=24.0
`
`
`
`| SLOPE-28.5
`
`PACE=
`TCAVERAGE:SLOPE
`
`
`
`DISTANCE =
`(TIMEs (5280/
`(PACE:50)))
`
`125
`
`RETURN
`
`isitºsº
`
`12
`0A
`
`120B
`
`TaSUM-7ER07
`
`* WUTraviºr.
`TaSUM/TaSTEPS
`
`120D
`
`
`
`SET TaSUM=0
`SET TaSTEPS=0
`
`Ex. 1016 / Page 13 of 27
`
`

`
`U.S. Patent
`U.S. Patent
`
`
`
`Jan. 25,2000
`Jan. 25, 2000
`
`Sheet 13 0f 13
`Sheet 13 of 13
`
`6,018,705
`6,018,705
`
`2.2%9
`8:
`8:
`2..._.
`.25.:
`E;S:9:
`2;98:
`
`2:
`8:
`2.:
`
`$2
`
`2.2
`
`:22:.
`
`SI.
`22
`
`
`
`.32053:w._:5528
`
`Wm.
`82
`
`2:2:._
`._$2..
`H.=2Q2.._
`
`22
`8.
`
`2.552;.5:
`
`Ex. 1016/Page 14 Of27
`
`3..30
`
`98
`
`Ex. 1016 / Page 14 of 27
`
`

`
`1
`MEASURING FOOT CONTACT TIME AND
`FOOT LOFT TIME OF A PERSON IN
`LOCOMOTION
`
`6,018,705
`
`10
`
`15
`
`20
`
`30
`
`2
`It is therefore a general object of the present invention to
`provide a new approach to pedometry that is affordable,
`reliable, easy to use and accurate.
`SUMMARY OF THE INVENTION
`According to the invention, a method and an apparatus are
`disclosed in which an output of an accelerometer is used to
`determine: (1) instances at which a foot of a user in
`locomotion leaves a surface, and (2) instances at which the
`foot of the user impacts the surface. By measuring the time
`difference between each instance at which the foot impacts
`the surface and the following instance at which the foot
`leaves the surface, several periods of time that the foot was
`in contact with the surface during strides taken by the user,
`i.e., several foot contact times, may be measured accurately
`and reliably. By calculating an average of these several
`measured foot contact times, an average foot contact time
`may be determined, from which information such as the
`pace of the user, rate of travel, distance traveled, etc., may
`be calculated. Additionally, by measuring time differences
`between the instances at which the foot of the user leaves the
`surface and the following instances at which the foot
`impacts the surface, the average period of time that the foot
`was not in contact with the surface, i.e., the average foot loft
`time, between strides taken by the user also may be calcu
`lated.
`According to one aspect of the present invention, a
`method for analyzing the motion of a foot relative to a
`surface includes using an output of an accelerometer to
`determine a moment that the foot leaves the surface.
`According to another aspect of the invention, the output
`signal of the accelerometer, which is indicative of the
`acceleration of the foot, is fed to a signal processing circuit
`configured to analyze the signal to determine a moment that
`the foot leaves the surface.
`According to another aspect, the output of the acceler
`ometer also is used to determine a moment that the foot
`comes into contact with the surface.
`According to yet another aspect, a foot contact time may
`be determined based upon a difference between the moment
`that the foot comes into contact with the surface and the
`moment that the foot leaves the surface, or a foot loft time
`may be determined based upon a time difference between the
`moment that the foot leaves the surface and the moment that
`the foot comes into contact with the surface.
`According to yet another aspect of the invention, the
`measured foot contact time is used to determine the rate at
`which a user is moving relative to the surface. Further, by
`measuring the time interval that the user is in locomotion,
`the distance that the user has traveled may be determined by
`multiplying the rate at which the user is moving by the time
`interval during which the rate measurement was determined.
`According to another aspect, a method for determining a
`rate that a user is moving on foot relative to a surface
`includes the steps of: (a) determining a foot contact time of
`a user in locomotion; (b) if the foot contact time is less than
`a first amount of time, then deriving the rate at which the
`user is moving according to a first equation in which the foot
`contact time is a factor; and (c) if the foot contact time is
`greater than a second amount of time, which is greater than
`the first amount of time, then deriving the rate at which the
`user is moving according to a second equation in which the
`foot contact time is a factor.
`According to another aspect of the invention, a device for
`analyzing the motion of a foot relative to a surface includes
`an accelerometer and a signal processing circuit. The accel
`
`25
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention relates to the monitoring of the
`orthopedic motion of a person and, more particularly, to the
`measuring of foot contact time, foot loft time, speed and/or
`pace of a person in locomotion.
`2. Discussion of the Related Art
`It is known that useful information may be derived from
`the measurement of the “foot contact time” of a person in
`locomotion, wherein “foot contact time” refers to the period
`of time that a foot of a person is in contact with the ground
`during a stride taken by the person. Once the foot contact
`time of a person is known, other information, such as rate of
`travel, distance traveled and ambulatory expended energy
`may be calculated based upon this measured foot contact
`time.
`In the past, foot contact time has been measured by
`placing pressure-sensitive sensors or switches, such as resis
`tive sensors, in both the heel and toe portions of the sole of
`a shoe, and measuring a time difference between a first
`signal output by the heel sensor (which indicates that the
`foot has made physical contact with the ground) and a
`second signal output by the toe sensor (which indicates that
`the foot has left the ground). These sensors, however, are
`subjected to a high-impact environment inside of the shoe,
`and therefore fail frequently. In addition, inaccurate foot
`contact time measurements may result when a user is taking
`strides during which either the heel sensor or the toe sensor
`is not activated, for example, when a user is running on his
`or her toes.
`35
`Another device well-known in the art is a pedometer. A
`pedometer typically is mounted on the waist of a user and is
`configured to count the footsteps of the user by measuring
`the number of times the user’s body moves up an down
`during footsteps taken by the user. A well-known prior art
`pedometer design uses a weight mounted on a spring to
`count the number of times that the user’s body moves up and
`down as the user is walking. By properly calibrating the
`pedometer according to a previously measured stride length
`of the user, the distance traveled by the user may be
`measured by this device. These “weight-on-a-spring”
`pedometers, however, generally cannot measure the distance
`traveled by a runner because the weight experiences exces
`sive bouncing during running and footsteps are often
`“double-counted” because of this bouncing, causing the
`pedometer to produce inaccurate results. These devices,
`therefore, may not be used across different training regimes
`(e.g., walking, jogging, and running).
`Another prior art pedometer device uses an accelerometer
`to measure the number of times that a foot impacts the
`ground when a user is in locomotion. That is, an acceler
`ometer is mounted on a shoe so as to produce a signal having
`pronounced downward going peaks that are indicative of
`moments that the foot impacts the ground. These devices
`therefore produce results similar to the prior art weight-on
`a-spring pedometer devices in that they merely count the
`number of footsteps of a user, and must be calibrated
`according to the stride length of the user in order to calculate
`the distance traveled by the user. Thus, these accelerometer
`based devices are subject to similar limitations as are the
`weight-on-a-spring devices, and are not able to measure the
`foot contact time of a user in locomotion.
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`Ex. 1016 / Page 15 of 27
`
`

`
`6,018,705
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`erometer is supported in relation to the foot and is configured
`and arranged to provide an output signal indicative of the
`acceleration of the foot. The signal processing circuit is
`coupled to the accelerometer to receive the output signal
`from it, and is configured to analyze the output signal to
`determine at
`least one moment
`that
`the foot
`leaves the
`surface.
`
`According to another aspect of the invention, the process-
`ing circuit also is configured to analyze the output signal to
`determine at least one moment that the foot makes contact
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`with the surface. Additionally, according to yet another
`aspect, the processing circuit is configured to: (1) analyze
`the output signal to determine at least one time period that
`the foot was in contact with the surface during at least one
`stride taken by the foot; and/or (2) analyze the output signal
`to determine at least one time period that the foot was not in
`contact with the surface between strides taken by the foot.
`According to another aspect, a device for determining the
`rate at which a user in locomotion is moving includes
`processing circuitry adapted to receive information regard-
`ing a foot contact time. The processing circuitry is config-
`ured such that if the foot contact time is less than a first
`
`amount of time, then the processing circuitry derives the rate
`at which the user is moving according to a first equation in
`which the foot contact time is a factor, and if the foot contact
`time is greater than a second amount of time, which is
`greater than or equal to the first amount of time, then the
`processing circuitry derives the rate at which the user is
`moving according to a second equation in which the foot
`contact time is a factor.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram of a network in which the
`present invention may be used;
`FIG. 2 is an illustration showing how the invention may
`be mounted with respect to a user;
`FIG. 3 is a block diagram of a system in which the
`invention may be used;
`FIG. 4 is a block diagram of one embodiment of a circuit
`according to the present invention;
`FIG. 5 is a schematic diagram of the circuit shown in FIG.
`
`4;
`
`FIG. 6 is a pair of graphs showing signals at two nodes of
`the circuit shown in FIG. 5 during a period in which a user
`is walking;
`FIG. 7 is a pair of graphs that compare the amplified/
`filtered output of the accelerometer according to the inven-
`tion with data obtained using prior art resistive sensors
`during a period that a user is walking;
`FIG. 8 is a pair of graphs showing signals at two nodes of
`the circuit shown in FIG. 5 during a period in which a user
`is running;
`FIG. 9 is a pair of graphs that compare the amplified/
`filtered output of the accelerometer according to the inven-
`tion with data obtained using prior art resistive sensors
`during a period that a user is running;
`FIG. 10 is a high-level flow diagram of a continuous-loop
`portion of a method for measuring foot contact time accord-
`ing to the invention;
`FIG. 11 is a high-level flow diagram of an interrupt
`portion of the method for measuring foot contact
`time
`according to the invention;
`FIG. 12 is a more detailed flow diagram of the
`continuous-loop portion of the method shown in FIG. 10;
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`FIG. 13 is a more detailed flow diagram of the interrupt
`portion of the method shown in FIG. 11; and
`FIG. 14 is a graph illustrating how the pace of a user in
`locomotion may be determined based upon the average
`measured foot contact time of a foot of the user.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`FIG. 1 shows a block diagram of a network 70 in which
`the present invention may be used. As shown, network 70
`includes network processing circuitry 30, a memory unit 28,
`a user interface 32, a display 26A, and an audio or vibra-
`tional indicator 26B. Network processing circuitry 30 also is
`coupled to receive inputs from one or more monitoring
`devices, such as foot contact time/foot loft time generators
`20A and 20B, heart rate monitor 22, and respiratory monitor
`24. The devices shown in FIG. 1 may be linked together, for
`example, via direct wiring or capacitive coupling, by using
`radio-frequency (RF) or infa-red (IR) transmitters/receivers,
`or by any other information transmission medium known to
`those skilled in the art.
`
`Network processing circuitry 30 may include a personal
`computer, or any other device capable of processing infor-
`mation from the various inputs of network 70. Memory unit
`28 is coupled to network processing circuitry 30 and is used
`to store programming and data for network processing
`circuitry 30 and/or to log data processed by circuitry 30.
`User interface 32 also is coupled to network processing
`circuitry 30 and permits a user, e.g., a walker, jogger or
`runner, to select a particular feature implemented by opera-
`tion of a software routine,
`to input particular operating
`parameters, or to select particular outputs for display 26A
`and/or audio or vibrational indicator 26B. Heart rate monitor
`22 and respiratory monitor 24 operate according to known
`methods and supply inputs to network processing circuitry
`30.
`
`Each one of foot contact time/foot loft time generators
`20A and 20B operates according to the present invention and
`supplies a separate input to network processing circuitry 30.
`By receiving information from the outputs of foot contact
`time/foot
`loft
`time generators 20A and 20B, heart rate
`monitor 22, and respiratory monitor 24, as well as inputs
`from any other type of electronic health monitoring device,
`network processing circuitry 30 is able to process all such
`information and provide a user with a fitness metric, to help
`the user attain a peak fitness level in the most efficient
`manner possible, or other health related information, useful
`for physical therapy, recovery, etc.
`FIG. 2 illustrates how a device according to the invention
`may be mounted on a user. Each of devices 20A—20C shown
`in FIG. 2 has a particular axis in which it senses acceleration,
`i.e., an acceleration sensing axis. According to one embodi-
`ment of the invention, each of the devices should be
`mounted such that the acceleration sensing axis of the device
`is oriented substantially parallel to a bottom surface of the
`foot of the user. For example, device 20A is mounted on the
`ankle of the user, device 20B is mounted on or within the
`shoe of the user, and device 20C is mounted on the waist of
`the user, with the acceleration sensing axises of the devices
`being oriented as indicated by arrows 80A, 80B and 80C,
`respectively. In each case, this positioning of the accelera-
`tion sensing axis has been found to produce an output signal
`that is most strongly indicative of both: (1) the moment at
`which the foot of the user leaves the surface, and (2) the
`moment at which the foot of the user comes into contact with
`
`the surface. It is hypothesized that this is true because a large
`
`Ex. 1016/Page 16 of27
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`Ex. 1016 / Page 16 of 27
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`

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`5
`portion of the change in acceleration sensed by the device is
`caused by the friction between the shoe of the user and the
`surface, rather than being caused primarily by the impact of
`the shoe with the surface, as is the case with prior art
`accelerometer-based pedometers.
`FIG. 3 shows a system 72 according to the present
`invention. As shown, the system 72 includes a foot contact
`time/foot loft time generator 20 (which could correspond to
`either of foot contact time/foot loft time generators 20A and
`20B in FIG. 1), a memory unit 54, a user interface 58, a
`display 56A, and an audio or vibrational indicator 56B.
`According to one embodiment, foot contact time/foot loft
`time generator 20 includes a micro-controller having virtu
`ally all circuitry, e.g., memory, timers and analog-to-digital
`(A/D) converters, on board, so that memory unit 54 need
`only be used to perform functions such as permanently
`storing data produced by foot contact time/foot loft time
`generator 20.
`User interface 58 may be activated conventionally by
`means of buttons, switches or other physically actuated
`devices, or may be voice activated using a commercially
`available voice activation device. As discussed in more
`detail below, user interface 58 may be used, for example: (1)
`to adjust any of several parameters used in a software routine
`according to the invention, (2) to select any of several
`possible outputs for the user, e.g., outputs could be displayed
`on display 56A or could provide a user with an audio or
`vibrational indication via audio or vibrational indicator 56B,
`or (3) to select features which are implemented through
`software routines called automatically responsive to user
`inputs.
`FIG. 4 shows an exemplary embodiment of the foot
`contact time/foot loft time generator 20 shown in FIG. 3. As
`shown, foot contact time/foot loft time generator 20 includes
`an accelerometer 34, an amplifier circuit 38 (which has a
`high-pass filter 36 included within it), and a micro-controllcr
`40. An output of accelerometer 34 is connected to an input
`of amplifier circuit 38, and an output of amplifier circuit 38
`is connected to an input of micro-controller 40.
`FIG. 5 shows the foot contact time/foot loft time generator
`20 shown in FIG. 4 in more detail. As shown in FIG. 5,
`output 50 of accelerometer 32 is provided to an input
`capacitor C1 included in amplifier circuit 38. Amplifier
`circuit 38 further includes operational amplifier 62 and
`resistors R1-R4. According to one embodiment, accelerom
`eter 32 may comprise part number ADXL250, manufactured
`by Analog Devices, Inc., and operational amplifier 62 may
`comprise part number MAX418 produced by MAXIM, Inc.
`As shown in FIG. 5, resistor R1 is connected between
`input capacitor C1 and the inverting input of operational
`amplifier 62, and resistor R2 is connected in feedback
`between the inverting input terminal and output 52 of
`operational amplifier 62. Thus, the combination of input
`capacitor C1 and resistor R1 form a high-pass filter, and the
`position of resistors R1 and R2 place the amplifier circuit in
`an inverting configuration with a gain-factor dependent on
`the relative values of resistors R1 and R2. In the embodi
`ment shown, resistor R2 has a value of one mega-ohm and
`resistor R2 has a value of 150 kili-ohms, so that the gain
`factor of the amplifier is approximately (-6.6). In addition,
`according to the embodiment shown, capacitor C1 has a
`value of 0.15 microfarads, so that high-pass filter section 36
`of amplifier circuit 38 cuts off input signal frequencies that
`are less than approximately 7.07 hertz.
`Resistor R3 is connected between VCC supply node 44
`and the non-inverting input 60 of operational amplifier 62,
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`6,018,705
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`6
`and resistor R4 is heonnected between non-inverting input
`60 and ground node 42. VCC supply node 44 is maintained
`at approximately 5 volts (e.g., regulated from a six-volt
`battery) in relation to ground node 42, and resistors R3 and
`R4 are of equal values (e.g., 50 kili-ohms each) so that the
`voltage at non-inverting input node 60 is maintained
`approximately midway between the voltage at VCC supply
`node 44 and ground (i.e., approximately 2.5 volts).
`Output 52 of amplifier circuit 38 is connected to a first
`A/D input 46 of low-power micro-controller 40, and node 60
`of amplifier circuit 38 is connected to a second A/D input 48
`of micro-controller 40. According to one cmbodiment,
`micro-controller 40 may comprise part number PIC:16C73
`manufactured by Microchip, Inc. This micro-controller
`includes on-board memory, A/D converters, and timers. A/D
`input 48 of micro-controller 40 serves as a zero-reference
`that is maintained at approximately 2.5 volts (as described
`above), and input 46 of micro-controller 40 serves as a
`variable input that fluctuates between 0 and 5 volts. Micro
`controller 40 samples the voltages at inputs 46 and 48 at a
`rate of approximately 500 samples-per-second, converts
`these samples into 8-bit unsigned digital values, and calcu
`lates the difference between the voltages at the two inputs,
`which difference is used during operation of software rou
`times described in more detail below.
`FIG. 6 shows two curves along the same time axis. These
`curves represent the 8-bit unsigned digital values of the
`voltages at nodes 50 and 52 of the circuit shown in FIG. 5
`during a period when a user is walking. That is, curve 50W
`in FIG. 6 represents (digitally) the voltage at output 50 of
`accelerometer 32 before it is filtered and amplified, and
`curves 46W and 48W, respectively, represent (digitally) the
`voltages at inputs 46 and 48 of micro-controller 40 during
`the period when the user is walking. While each of curves
`46W, 48W and 50W shares a common time axis, the
`voltage-magnitude axis of curves 46W and 48W is distinct
`from the voltage-magnitude axis of curve 50W. Therefore,
`the placement of curve 50W above curves 46W and 48W is
`not intended to signify that curve 50W attains a higher
`amplitude than do curves 46W and 48W.
`As shown in FIG. 6, because amplifier circuit 38 is
`configured to have a negative gainfactor, high peak 51W of
`curve 50W corresponds with low peak 47W of curve 46W.
`High peak 49W of curve 46W, however, does not appear to
`correspond to a low peak of curve 50W. That is, high peak
`49W is ascertainable only after the output of accelerometer
`34 has been high-pass filtered and amplified by amplifier
`circuit 38. It is high peak 49W in curve 46W that indicates
`the moment that the foot of the user has left the surface when
`the user is in locomotion.
`Similarly, low peak 47W in curve 46W indicates the
`moment that the foot of the user has impacted with the
`surface when the user is in locomotion. By measuring the
`time difference between peak 47W and peak 49W of curve
`46W, the foot contact time of the user when the user is in
`locomotion may be ascertained. As used herein, “foot con
`tact time” refers to the period of time between when a foot
`of a user impacts a surface and when the foot next leaves the
`surface.
`In a similar manner, the foot loft time of a user in
`locomotion may be determined. That is, by measuring the
`time difference between high peak 49W and low peak 53W
`in curve 46W, the foot loft time of the user is ascertainable.
`As used herein, “foot loft time” refers to the period of time
`between when a foot of a user leaves a surface and when the
`foot next comes into contact with the surface.
`
`Ex. 1016 / Page 17 of 27
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`

`
`7
`FIG. 7 shows the correspondence, when a user is walking,
`between (1) two curves 55H and 55T produced by resistive
`sensors mounted in the heel and toe, respectively, of a shoe
`and (2) the amplified and filtered output of the accelerometer
`according to the invention. That is, curve 55H represents the
`output of a resistive sensor mounted in the heel of a shoe,
`curve 55T represents the output of a resistive sensor
`mounted in the toe of the shoe, and curve 46W represents the
`voltage at node 52 of circuit 20 (shown in FIG. 5). All of
`these measurements were taken while a user was walking.
`While each of curves 55H, 55T and 46W shares a common
`time axis, the voltage-magnitude axis of curves 55H and 55T
`is distinct from the voltage-magnitude axis of curve 46W.
`Therefore, the placement of curves 55H and 55T above
`curve 46W is not intended to signify tha