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`SAMSUNG EXHIBIT 1005
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`U.S. Patent
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`Dec. 9, 2008
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`Sheet 1 of 5
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`US 7,463,997 B2
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`yo!
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`PROCESSING UNIT
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`|
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`SETTING
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`FIRST COMPARATOR
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`DISTANCE—CALCULATION
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`THRESHOLD-ADAPTATION
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`SECOND COMPARATOR
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`
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`ENVELOPE CALCULATION
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`MEAN-VALUE CALCULATION
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`LENGTH-ESTIMATION
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`AXIS—DETERMINATION
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`4
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`DISPLAY
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`INTERFACE
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`FI. 1
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`U.S. Patent
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`Dec. 9, 2008
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`Sheet 2 of 5
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`US 7,463,997 B2
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`U.S. Patent
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`Dec. 9, 2008
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`Sheet 3 of 5
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`US 7,463,997 B2
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` start)
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`PARAMETER
`INITIALIZATION
`
`
`10
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`DETECTION
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`12
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`NEGATIVE PHASE
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`DETEGHON
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`CalAcc > S*
`43 14
` CalAce < S
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`15
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`20
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`HAS A
`YES
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`NEGATIVE PHASE BEEN
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`STEP
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`INCREMENT
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`STEP LENGTH
`ADAPTATION
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`m4
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`;
`;
`CalAccANDTHRESHOLDADAPTATION
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`s
`MIN ATION OF
`4
`RATION
`UJ
`|
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`INCREMENT
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`22
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`23
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`INCREMENTOF CALORIE
`SPEED COMPUTATION
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`
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`
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`Fig.3
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`U.S. Patent
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`Dec.9, 2008
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`Sheet 4 of 5
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`US 7,463,997 B2
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`DETERMINATION OF ACCELERATION DATUM
`CalAcc AND THRESHOLD ADAPTATION
`
`
`11.18
`'
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`ACQUISITION OF
`ACCELERATION SAMPLE Acc
`
`30
`
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`ELIMINATION OF D.C. COMPONENT |
`34
`AND DETERMINATIONOF CalAce
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`34
`
`32
`
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`Env* = o.,“Env*
`(a, < 1)
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`tm
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`Real
`;
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`NOKinetYES
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`37
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`(ay < 1)
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`35
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`nv’
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`@ACC
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`S* = B* Env*
`(B<1)
`|
`38
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`39
`40
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`eeSeshSt=S,
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`S = p* Env
`(B <1)
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`42
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`43
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`(stor)
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`Fig.4
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`U.S. Patent
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`Dec. 9, 2008
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`Sheet 5 of 5
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`US 7,463,997 B2
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`CalAcc
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`MA
`ATHY
`3}
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`nTae—
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`
`
`START
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`10
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`PARAMETER
`INITIALIZATION
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`
`
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`HAS A
`POSITIVE PHASE BEEN
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`DETECTED?
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`YES
`STEP INCREMENT
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`DISTANCE INCREMENT
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`12
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`13
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`20
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`,
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`22
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`__"Speecovpuraron28)
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`Fig./
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`SPEED COMPUTATION
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`US 7,463,997 B2
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`1
`PEDOMETER DEVICE AND STEP
`DETECTION METHOD USING AN
`ALGORITHM FOR SELF-ADAPTIVE
`COMPUTATION OF ACCELERATION
`THRESHOLDS
`
`BACKGROUNDOF THE INVENTION
`
`1. l4eld of the Invention
`
`D
`
`i)D
`
`35
`
`50
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`60
`
`65
`
`Thepresent invention relates to a pedometer device and to
`a step detection method using an algorithmfor self-adaptive
`computation of acceleration thresholds.
`2. Description of the Related Art
`Step-counting devices (referred to in general as pedom-
`eters) are known, which, being carried by a user, enable
`measurementofthe numberof steps made, and calculation of
`the distance traveled, as well as supplying of additional infor-
`mation, such as, for example, the average speed, or the con-
`sumption ofcalories.
`Pedometers are advantageously usedin inertial navigation
`systems (the so-called dead-reckoning systems) applied to
`human beings. Such systems trace the movementsof a user,
`byidentifying and measuring his/her displacementsstarting
`from a knownstarting point, without resorting to the use ofa
`Global Positioning System (GPS), or by acting as aid to a
`GPS. In said systems, a compass supplies the information
`linked to the direction of displacement, and the pedometer
`supplies the information linked to the amount of said dis-
`placement. Pedometersare also used in a wide range of appli-
`cationsin the clinical sector (for example, in rehabilitation),
`and in general in the field of fitness (for example, as instru-
`ments for monitoring a physicalactivity).
`In particular, pedometers are knownthat use integrated
`For a better understanding of the present invention, pre-
`accelerometers of a MEMS(micro-electromechanical sys-
`ferred embodiments thereof are nowdescribed, purely by
`tem) type for step detection. In particular, such pedometers
`way of non-limiting example and with reference to the
`have particularly compact dimensions, and can be advanta-
`attached drawings, wherein:
`gcously integrated within portable devices, such as mobile
`FIG. 1 showsa block diagram of a pedometer device;
`phones, Mp3 readers, camcorders, etc.
`FIG. 2 shows a graph corresponding to the pattern of an
`&D
`The aforesaid pedometers implement a step detection
`acceleration signal duringastep;
`method based upon the analysis of the pattern of a vertical
`l'IG. 3 shows a flowchart corresponding to operations of
`acceleration, which is gencrated during the various phases of
`detection and counting ofsteps, executed by a processing unit
`the step bythe contact ofthe foot to the ground, and whichis
`of the pedometer device of FIG.1;
`detected by an accelerometerfixed to the body of the user.In
`FIG. 4 showsa flowchart corresponding to operations of
`this connection,it is emphasized that “vertical acceleration”
`modification of acceleration thresholds,
`> self-adaptive
`meansherein an acceleration directed alongthe vertical ofthe
`executed by the processing unit of the pedometer device of
`user’s body. In particular, the occurrence of a step is deter-
`FIG.1;
`mined byidentifying acceleration peaks that appear in the
`FIGS. 5-6 are graphs corresponding to the pattern of an
`acceleration signal, and said peaks are detected by comparing
`acceleration signal during, a step and of reference thresholds
`the acceleration signal with a given reference threshold, hav-
`associated to the algorithm of FIG.3;
`ing a pre-set value.
`FIG.7 showsa possible variant ofthe flowchart of FIG. 3;
`However, even thoughthe acceleration signal hasa profile
`and
`that is repeatable at each step,its pattern (and,in particular,its
`amplitude and temporal extension) has a wide variability
`according to a numberoffactors that affect the gait, such as 5:
`the resting surface, the type of shoe worn (rigid sole or flex-
`ible sole, etc.), and the speed of the gait (slow walking,fast
`walking, running,etc.), Furthermore, each individual user has
`given characteristics and peculiarities that affect the gait,
`differentiating it from that of otherusers.
`It follows that a step detection based upon the comparison
`ofthe value ofthe acceleration signal with a reference thresh-
`old having, a pre-set value for the detection of acceleration
`peaks, involves the occurrence of errors that may even be
`considerable in counting ofthe steps, and in the measurement
`of the distance traveled. In particular, if the threshold is too
`low, spurious signals, rebounds, or noise in general, may be
`
`2
`counted as steps; on the other hand, if the threshold is too
`high, some steps maynotbe detected.
`
`
`
`BRIEF SUMMARYOF THE INVENTION
`
`One embodiment of the present invention provides a
`pedometer device and a method for detecting and counting
`steps which will enable the aforesaid disadvantages and prob-
`lems to be overcome.
`
`One embodimentofthe inventionis a pedometer device for
`detecting and counting the steps ofa user. The device includes
`an accelerometer sensor configured to detect an acceleration
`generated during a step; and a processing unit connected to
`the accelerometer sensor, and configured to process an aceel-
`eration signal relating to the acceleration to detect the occur-
`rence of a step. The processing unit includes a first compara-
`tor configured to compare the acceleration signal witha first
`reference threshold, and a threshold-adaptation circuit con-
`figured to modify thefirst reference threshold as a function of
`the accelerationsignal.
`One embodiment of the invention is a step detection
`method for detecting steps in the gait of a user. The method
`includes producing an accelerationsignalrelating to an accel-
`eration generated during a step; and processing the accelera-
`tion signalto detect the occurrence ofthe step. The processing
`step includes comparing the acceleration signal with a first
`reference threshold, and modifyingthefirst reference thresh-
`old as a function of the acceleration signal.
`
`BRIEF DESCRIPTION OF THE SEVERAL
`
`
`VIEWS OF THE DRAWINGS
`
`FIG. 8 is a partially exploded schematic view of a portable
`device,
`in particular a mobile phone,
`incorporating the
`pedometer device of FIG. 1.
`
`
`
`DETAIL ED DESCRIPTION OF THE INVENTION
`
`
`
`FIG. 1 is a schematic illustration of a pedometer device1,
`comprising an accelerometer2, of a linear type and having a
`vertical detection axis z, and a processing unit 3, connected to
`the accelerometer 2. Advantageously, the accelerometer 2
`and the processing unit 3 are mounted on the sameprinted
`circuit, housed inside a casing ofthe pedometer device 1 (not
`illustrated). The pedometer device 1 is carried bya user, for
`example on his belt or on his shoulder, so as to be fixed to the
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`US 7,463,997 B2
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`D
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`4
`3
`renceof a step), counting ofthe steps and measurement ofthe
`body of the user and be able to sense vertical accelerations
`total distance traveled are updated; otherwise, the algorithm
`that occur during the step, caused bythe impactof the feet on
`returns to the imitial condition of looking for a new positive
`the ground.
`phaseofthestep. In particular, the positive acceleration peaks
`The pedometer device 1 further comprises a display screen
`that occur within the pre-set time interval are ignored by the
`4, connected at an output ofthe processing unit 3, and an
`algorithm (in so far as they canbe ascribed to phenomena of
`interface 5, connected at an inputofthe processing unit 3. The
`noise, such as impact, anomalous rebounds, etc.).
`display screen 4 displays information at output from the
`Jo detail, the algorithmstarts withinitialization, block 10,
`pedometer device 1, such as the numberofsteps, the distance
`ofthe valuesofthe positive and negative reference thresholds
`traveled, etc. The interface 5, for example, including push-
`buttons, an alphanumeric keypad, communication ports,etc.,
`Stand 5‘, respectively, at a positive minimum value S, and at
`a negative minimum value S., the latter being smaller, in
`allows the user to communicate withthe processing unit 3 (for
`absolute value, than the positive minimum value S,. As will
`example, by entering data).
`be clarified, said minimum values represent
`limit values
`The accelerometer 2 is advantageouslyan integrated sen-
`belowwhichthe reference thresholdsare not allowed to drop.
`sor of semiconductor material, made using the MEMStech-
`nology, of a known type and thus not described in detail
`Tn addition, the values ofa positive envelope Tinv™ and ofa
`negative envelope Env” of the acceleration signal A (which
`herein. In use, the accelerometer 2 detects the component
`will subsequently be used for modification of the reference
`along the detection axis z of the vertical acceleration gener-
`thresholds) are initialized, respectively, at the positive mini-
`ated during the step, and produces a corresponding accelera-
`mum value S, and at the negative minimum value S,.
`tion signal A.
`i)D
`As shownin FIG. 2,the pattern ofthe acceleration signal A Next, block 11, the processing unit 3 determinesafirst
`
`(with the d.c. component filtered out) in time t has a given
`acceleration datum CalAcc, and consequently modifies the
`acceleration profile which repeats at cach step (indicated by
`values of the reference thresholds (as will be described in
`the dashed rectangle). In detail, the acceleration profile com-
`detail hereinafter with reference to FIGS. 4 and 5).
`prises in succession: a positive phase, in which a positive-
`Thealgorithm then proceeds, block 12, with the search for
`acceleration peak occurs(i.e., directed upwards), due to con-
`the positive phase ofthe step, by comparing the value ofthe
`tact and consequent impactofthe foot with the ground; and a
`acceleration datum CalAccwith the positive reference thresh-
`negative phase in whicha negative-acceleration peak occurs
`old S*, to detect a positive acccleration peak of the aceclera-
`(.e., directed downwards) due to rebound, having, an absolute
`tion signal A.
`value smaller thanthat of the positive-acceleration peak.
`Until a positive phase of the step is found, block 13, the
`The processing unit 3, comprising a microprocessorcircuit
`algorithm proceeds with acquisition of a new acceleration
`(for example, a microcontroller or DSP), acquires at pre-set
`datum CalAcc in block 11 (and corresponding modification
`intervals samples of the acceleration signal A generated by
`of the reference thresholds), and with the comparison of said
`the accelerometer 2, and executes appropriate processing
`new acceleration datum withthe positive reference threshold
`Ss.
`operations for counting the numberof steps and measuring
`the distance traveled. As will be described in detail hereinaf-
`‘The positive phase is detected whenthe acceleration datum
`ter, the processing unit 3 compares the value ofthe accelera-
`exceeds the positive reference threshold S* and then drops
`tion signal A (with the d.c. componentfiltered out) with a
`belowthe positive reference threshold, the instant of detec-
`tion of the positive phase corresponding to the instant in
`positive reference threshold S* and with a negative reference
`threshold S~, for identifying, respectively, the positive phase
`whichthe acceleration datum drops again below the positive
`(positive acceleration peak) and the negative phase (negative
`reference threshold S*. At this instant, the processing unit 3
`acceleration peak) of the step.
`stores the value assumed bythe positive reference threshold
`According to one embodimentofthe present invention, the
`S*, which is a maximum value S*,,_...
`After the positive phase detection, the algorithm proceeds
`values ofthe positive and negative reference thresholds $*, S~
`are not fixed and equal to a given pre-set value, but are
`with the search for the negative phase ofthe step, block 14,
`calculated in a self-adaptive way(i.e., in a way that adapts
`5 1.e., of a negative acceleration peak, by comparing the value
`without any external intervention froma user) by the process-
`ofthe acceleration datum CalAcc with the negative reference
`ing unit 3, based on the valucs assumed bythe detected
`threshold S~. In particular, the search for the negative phase of
`acceleration. In particular, as will be clarified hereinafter, the
`the step is executed within a certain time interval Mask, the
`value of which must be lower than a maximum interval Max-
`values ofthe positive and negative reference thresholds S*, S~
`are modified at each acquisition of a new sample ofthe
`_Maskfromdetection ofthe positive phase (corresponding to
`acceleration signal A, as a function ofthe value ofa positive
`acertain numberof samples, the value ofwhich is determined
`and negative amplitude envelope ofthe acceleration signal, in
`also as a function of the sampling rate of the acceleration
`such a mannerthat the reference thresholds vary with time
`data).
`approximately following said envelopes. The pedometer
`Until a negative acceleration peak is detected, block 15,
`device 1 thus adapts to variations in the detection conditions 55
`and. as long as the time interval Mask is shorter than the
`(and, in particular, to different profiles of the acceleration
`maximum interval Max_Mask,block 16, the algorithm pro-
`signal, in terms of amplitude and duration), due, for example,
`ceeds with the search for the negative phase of the step. In
`detail, the time interval Maskis incremented, block 17, a new
`to a different type of terrain, or lo an increase in the speed of
`the gait.
`acceleration datum CalAcc is acquired (and the values of the
`The algorithm implemented. by the processing unit 3 for
`reference thresholds are modified accordingly), block 18
`performing, amongotherthings, the operations of step count-
`(which is equivalent to block 11), and the algorithm returns to
`ing and oftraveled distance measurement is now described,
`block 14. If no negative phase of the step has been identified
`with reference to FIG.3. Said algorithmenvisages the analy-
`after expiry of the maximuminterval Max_Mask, block 16,
`sis of the acceleration signal A in order to look for a positive
`the algorithm returns to block 11 in order to look for a new
`phase ofthe step followed by a negative phase withina pre-set
`potential positive phase ofthestep.
`umeinterval from the occurrenceofthe positive phase. In the
`Onthe contrary, if the negative phaseis identified within
`case where said sequence occurs (which indicates the occur-
`the maximum interval Max_Mask (1.e.,
`the acceleration
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`US 7,463,997 B2
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`5
`datum drops below the negative reference threshold S~), the
`processing unit 3 determines the occurrenceof a step, and,
`block 20, increments the count of the detected steps. Further-
`more, the estimate of the distance traveled is updated by
`adding to the previous value an estimate ofthe length ofthe
`current step LPS.
`In detail, according to one embodiment of the present
`invention, block 21, the processing unit 3 calculates theesti-
`mate ofthe length ofthe current step LPSas a function ofthe
`maximum value S,,,, reached by the positive reference
`threshold S* during the positive phase of the step, which is
`indicatory ofthe value ofthe positive acceleration peak.‘he
`actual length ofthe step varies with respect to a standard value
`determined onthebasis of the physical characteristics of the
`user, according to the speed ofthe step, or, equivalently, to the
`amplitude of the generated acceleration. Consequently, the
`estimate ofthe length ofthe currentstep IPS 1s calculated via
`he formula:
`
`LPS=LPS\S*max)
`
`where LP is a standard length ofthe step, corresponding to 0.4
`o 0.5 times the heightof the user, and f(S*,,,,,) is a corrective
`‘unction, for example a linear one, based upon the maximum
`value S*,,,..,-. |he corrective function f(S",,,,,,.) can be tabulated
`on the basis ofexperimental tests, which enable association to
`a given maximum valuc S*,,,,,. of an appropriate correction to
`be made to the standard lengthofthe step LP. Inparticular, the
`unction f(S*,,,,,.) is conveniently stored in the processing unit
`3.
`
`
`
`The algorithm then proceeds, block 22, by increasing the
`distance traveled on the basis of the estimate of the length of
`he current step LPS, previously calculated. Furthermore,
`block 23, further variables supplied at output from the
`pedometer device 1 can be updated, such as the number of
`calories (also in this case, the previous count is updated by
`adding an average consumptionofcalories per step), and the
`average and inslantaneous speed of travel, which are calcu-
`ated in a known waynot described in detail herein.
`Neat, the algorithm returns to block 11 in order to detect a
`newacceleration profile indicating occurrence ofa step.
`There will now be described in detail, with reference to
`FIG. 4, the algorithm implemented bythe processing unit 3
`or determination of a new acceleration datum CalAcc and
`consequent updating ofthe valuesofthe positive and negative
`reference thresholds St and S~, in such a mannerthat the
`aforesaid values will follow approximatelythe positive and
`negative envelope of the acceleration signal.
`In brief, said algorithm envisages calculation, for each new
`w2
`acceleration datum CalAcc, ofthe valuesofthe positive enve-
`lope Env* and negative envelope Env’, and modification of —
`the value ofthe positive and negative reference thresholds St
`and S” as a function of the positive envelope Env* and nega-
`live envelope Env’, respectively.
`the processing unit 3
`In detail,
`in an initial block 30,
`acquires from the accelerometer 2 a new acceleration sample
`Acc ofthe acceleration A. Then, block 31, the d.c. component
`ofsaid acceleration value (due substantially to the accelera-
`ton of gravity) is eliminated so as to determinethe accelera-
`tion datum CalAcc, with zero meanvalue, which will be used
`subsequentlyin the algorithm.In detail, the mean value Acem
`of the acceleration sample Acc is calculated withthe expres-
`sion:
`
`6
`mean value and of the acceleration datum, which werecal-
`culated at the previous acquisition. The newacceleration
`datum CalAcc is calculated by applyingthe relation:
`CalAcc=Acc-Accm
`
`
`
`
`
`Then,the algorithm proceeds with the determination ofthe
`new values ofthe positive and negative envelopes Env*, Env.
`In detail, block 32, if the value of the acceleration datum
`
`CalAccis higher than the value of the positive envelope Env~
`(as calculated at the previous acquisilion), the new value of
`the positive envelope Env* is set equal to the value of the
`acceleration datum CalAcc, block 33. Otherwise, block 34,
`the value ofthe positive envelope Env* is set equal to a proper
`fraction of the previous value; 1.e., the previous value is mul-
`tiplied by a first constant a,<1, for example, a,=0.9458. In
`this way, the value of the envelope coincides substantially
`with the value of the acceleration datum,if the acceleration
`datum is greater than the previous value of the envelope, and
`otherwise decreases(in particular, almost exponentially) with
`respect to the previous value.
`Likewise, block 35, if the value of the acceleration datum
`CalAccis smaller than the negative envelope Env” (as calcu-
`lated at the previous acquisition), the new value ofthe nega-
`tive envelope Linv” is set equal to the value ofthe acceleration
`datum CalAce, block 36. Otherwise, block 37, the value ofthe
`negative envelope Env”is set equalto a properfraction ofthe
`previous value of the envelope;
`i.e.,
`it is multiplied by a
`second constant «,<1, for example, 0,=0.9438. Note, in par-
`ticular, that the different value of the first and second con-
`slants a, ais due to the different value of the positive and
`negative accelerations, said negative accelerations being of
`smaller intensity, since the negative phase of the step is a
`reboundofthe positive phase.
`The algorithm then proceeds with updating ofthe values of
`the reference thresholds as a function of the envelope values
`previously calculated. In detail, block 38, the valuc of the
`positive reference threshold S* is set equal to a certain proper
`
`fraction of the positive envelope Env*; in particular,it is set
`equalto the value ofthe positive envelope Env* multiplied by
`a third constant B<1, for example, §=0.65. However, if the
`value thus calculated is less than the positive minimum value
`S,, block 39, the value of the positive reference threshold S*
`is set at said positive minimum value S,, block 40.
`Likewise, black 41, the value of the negative reference
`threshold S” is set equal to a certain proper fraction of the
`negative envelope; in particular, also this value is multiplied
`bythe third constant B. However, once again, ifthe value thus
`calculated is less than the negative minimum value S,, block
`42,the value ofthe negative reference threshold S~ is set at the
`negative minimumvalue S,, block 43.
`Thevalues ofthe new reference thresholds thus calculated
`are then used for detection of the positive and negative phases
`of the step, as described previously.
`FIGS.5 and 6 show the curvesofthe positive and negative
`reference thresholds S*, S”, and ofthe positive and negative
`envelopes Env*, Env’, calculated using the algorithm
`described previously, and the pattern of the acceleration sig-
`nal CalAcc(constituted by the sequence ofthe acceleration
`data CalAcc). It is evident that the reference thresholds sub-
`stantially follow the envelopes of the acceleration signal
`(which, in turn, follow the peaks of the acceleration signal).
`In detail, the value ofthe positive acceleration threshold S*
`is initially equal to the positive minimum value S, (see, in
`particular, FIG. 6), and remains constant as long asthe accel-
`eration datum CalAcc remains less than the positive accel-
`eration threshold S*. Starting from the instant at which the
`acceleration datum CalAcc exceeds the positive acceleration
`
`0
`
`5
`
`20
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`weD
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`35
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`Accm=7 Acem+(1-y): CalAce
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`65
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`wherey is a constant between 0 and 1, for example equal to
`0.95, andAcem and CalAccare the values, respectively,ofthe
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`7
`threshold S-, and as long as the acceleration datum CalAcc
`increases, the positive acceleration threshold S* follows, in a
`“damped”way, the increase ofthe acceleration datum CalAcc
`(see,
`in particular, FIG. 5). Next, the acceleration datum
`CalAcc starts to decrease, and, along with it, the positive
`acceleration threshold S*, which, as long as the acceleration
`datum CalAcc decreases, assumesa decreasing pattern (with-
`out, however, dropping below the positive minimum value
`S,). In particular, at the end of the positive phase ofthe step,
`the maximum value S*,,,. is stored. he positive reference
`threshold S* returns to the positive minimum value S, when
`the user comesto a halt. A similar pattern (in absolute valuc)
`is showedbythe negative acceleration threshold S”, with the
`difference that the decrease (in absolute value) ofthe negative
`acceleration threshold S~is different, in particularfaster. Said
`difference is due to the different conformation ofthe negative
`acceleration peak, which has a smaller amplitude anda longer
`duration as comparedto the positive acceleration peak,so that
`an excessively long decrease time could lead to the peak not
`being detected. The ditterence, in absolute value, ofthe posi-
`ive minimum valueS, and ofthe negative minimum value S,
`is duc to the samereason.
`According to one embodiment ofthe present invention, the
`positive minimum value S, and the negative minimum value
`S, can be modified from outside, for example through the
`interface 5 in order to modify the sensitivity of the pedometer
`device 1. In particular, if said minimumvaluesare decreased,
`he sensitivity ofthe device increases, in so far as acceleration
`peaks of smaller amplitude (for example, dueto a particularly
`slow gait or to a surface that is not very rigid) can be detected.
`At the same time, however, the number offalse positives
`detected increases, in so far as noise (external vibrations,
`bumps, fast movements made by the user) is more likely to
`cause erroneous detections assimilated to the phases of the
`step.
`The advantages of the pedometer device and ofthe corre-
`sponding step detection methodare clear from the foregoing
`description.
`In anycase, it is emphasized that the pedometer device 1 is
`able to adapt to changes in the acceleration profile, for
`example due to an increase in the walking speed, and so
`external interventions for resetting the acceleration thresh-
`olds necessaryfor step detection are not needed.
`The fact that the acceleration thresholds follow the enve-
`lopes ofthe acceleration signal (analogously to an electronic
`peak detector) enables said changes to be followed rapidly,
`without any risk for any loss of steps and counting crrors
`occurring, and at the same time enables a good insensitivity to
`noise to be achieved. In particular, when the accelerations
`w2
`increase (in absolute value), for example because the walking 5
`speed has increased, the reference thresholds increase rap-
`idly, so as to adapt rapidly to the new conditions. When,
`instead, the accelerations decrease, for example because the
`user is slowing down,the reference thresholds also decrease,
`but slowly, and always remaining above a minimumvalue. In 45
`this way, the deviceis able to follow closely a newincrease in
`the acceleration values.
`Finally, it is clear that modifications and variations can be
`made to what is described and illustrated herein without
`thereby departing fromthe scope of the present invention, as
`defined in the appended claims.
`In particular, as shown in FIG. 7, in which the samerefer-
`ence numbers are used for designating, blocks similar to the
`ones previously described, according to an alternative
`embodimentof the present invention, the step detection algo-
`rithm can be simplified, and can be based exclusively upon
`the identification of the positive phaseof the step (1.e., of the
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`positive acceleration peak). In this case, the algorithm uses a
`single reference threshold, in particularthe positive reference
`threshold S*, which is modified as a functionof the value of
`the positive envelope Env*, in a way altogether similar to
`what has been described previously. Said simplified algo-
`rithm, although computationally less burdensomeforthepro-
`cessing unit 3, has, however, the disadvantage of being more
`sensitive to noise. In fact, the lack of check onthe presence of
`the negative phase, after the positive phase, renders false
`detection and counting errors morelikely.
`The accelerometer 2 could be equipped with a numberof
`axes ofmeasurement, for example three mutually orthogonal
`axes of measurement,and be built, for example, as described
`in “3-axis Digital Output Accelerometer For Future Automo-
`tive Applications”, B. Vigna et al. AMAA 2004. In this case,
`according to one embodiment of the present invention, the
`algorithm implemented by the processing unit 3 envisages
`identifying the mainvertical axis to be used for step detection
`as the axis of detection that has the highest mean acceleration
`value Accm(on account of pravity). For example, the main
`vertical axis can be identified at each acquisition of a new
`acceleration sample, block 30 of I'IG. 4, so as to take into
`accountvariations in the orientation of the pedometer device
`1, and consequently of the accelerometer2 arrangedinsideit.
`Instead of being integrated in the pedometer device 1, the
`accelerometer 2 could be arranged outsidethe casing thereof,
`and connected, in a wired or wireless way, to the detection
`unit 3. In this case, the accelerometer 2 could advantageously
`be housed in a garment or accessory worn bythe user, for
`example a shoe, a belt, a watch, etc.
`As shown in FIG. 8, the pedometer device 1, due to its
`reduced dimensions, may advantageously be housed inside a
`portable device, in particular a mobile phone 50 (or else an
`Mp3reader, a camera, a PDA, a game console, etc.). In this
`> case, the accelerometer 2, and the processing unit 3 are
`mounted ona printed circuit board 52 fixed within a casing 53
`ofthe mobile phone 50. Advantageously, in this embodiment,
`the processing unit 3, in addition to implementing the algo-
`rithms previously described, controls the operation of the
`mobile phone 50. Likewise, the display screen 4, which is
`obviously arrangedso as to be visible from outside the casing
`53, shows both information corresponding to the pedometer
`device 1 and, more in general, information linked to operation
`ofthe mobile phone 50. The interface 5 in this case preferably
`comprises a communication port (of a known type, and not
`shown), which can be interfaced with a personal computer.
`Theinterface 5 can therefore be used both for downloading
`the data produced by the pedometer device 1 (among whichat
`least the number of steps counted) and for uploading into the
`processing unit 3 operating parameters of the pedometer
`device 1, such as the positive and negative minimum values
`S,, 85.
`Finally, even though the entire description refersto a digital
`implementation ofthe pedometer device 1, it is evident that a
`similar version of an analog type (comprising, among other
`things, threshold comparators, a peak detector, amplifiers,
`etc.) can be contemplated by making the appropriate obvious
`substitutions.
`All of the above U.S. patents, U.S. patent application pub-
`lications, U.S. patent applications, foreign patents, foreign
`patent applications and non-patent publicationsreferred to in
`this specification and/or listed in the Application Data Sheet,
`are incorporated herein byreference, in their entirety.
`The invention claimed is:
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`1. A pedometer device for detecting and counting steps of
`a user, the device comprising:
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`US 7,463,997 B2
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`9
`an accelerometer sensor configured to detect an accelera-
`tion generated during a step; and
`aprocessing unit coupled to said accelerometer sensor, and
`configured to process an acceleration signal relating to
`said acceleration to detect an occurrenceof the step, said
`processing unit including:
`first comparator means for comparing said acceleration
`signal with a first reference threshold, said processing
`unil being configured to detect the occurrence of the
`step based on a result of said comparin