US007698097B2
`
`a2) United States Patent
`US 7,698,097 B2
`(10) Patent No.:
`
` Pasoliniet al. (45) Date of Patent: Apr.13, 2010
`
`
`(54) METHOD FOR CONTROLLING A
`PEDOMETER BASED ON THE USE OF
`INERTIAL SENSORS AND PEDOMETER
`IMPLEMENTING THE METHOD
`
`5/2005 Blackadar etal. ........... 702/182
`6,898,550 Bl
`1/2007 Tsuji occ eeeeeeeeneeeeee 482/8
`7,169,084 B2*
`7,297,088 B2* 11/2007 TSUji eccccccccccseeccsees 482/3
`2001/0031031 Al* 10/2001 Ogawaetal. wo... 377/24.2
`
`(75)
`
`Inventors: Fabio Pasolini, S. Martino Siccomario
`(IT); Ivo Binda, Voghera (IT)
`
`(73) Assignee: STMicroelectronics S.R.L., Agrate
`Brianza (IT)
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 707 days.
`
`(21) Appl. No.: 11/537,986
`
`(22)
`
`Filed:
`
`Oct. 2, 2006
`
`FOREIGN PATENT DOCUMENTS
`
`GB
`JP
`JP
`
`2 359 890
`63-262784
`04-192095
`
`9/2001
`10/1988
`7/1992
`
`OTHER PUBLICATIONS
`
`Tasaka, Translation of JP 63262784, published Oct. 31, 1988.*
`Tasaka, Translation of H04-192095, published Jul. 10, 1992.*
`
`(65)
`
`(30)
`
`Prior Publication Data
`
`* cited by examiner
`
`US 2007/0143069 Al
`
`Jun. 21, 2007
`
`Foreign Application Priority Data
`
`Primary Examiner—Hal D Wachsman
`(74) Attorney, Agent, or Firm—Lisa K. Jorgenson; Robert
`Jannucci; Seed IP Law Group PLLC
`
`Oct. 3, 2005
`
`(EP)
`
`eeceeeceereteeeeeseeneees 05425684
`
`(57)
`
`ABSTRACT
`
`(51)
`
`Int. Cl.
`(2006.01)
`GOIC 22/00
`(2006.01)
`GOOF 17/40
`(52) U.S.Ccee 702/160; 702/176; 702/178;
`377/24.2
`
`(58) Field of Classification Search ................. 702/160,
`702/176, 178
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`A methodfor controlling a pedometer includesthe steps of:
`generating a signal correlated to movements of a user of the
`pedometer; and detecting steps of the user on the basis of the
`signal. The method moreover envisagesthe steps of checking
`whether sequences of detected steps satisfy pre-determined
`conditions of regularity; updating a total number of valid
`steps ifthe conditions of regularity are satisfied; and prevent-
`ing the updating of the total number of valid steps if the
`conditions of regularity are not satisfied.
`
`6,175,608 BI*
`
`1/2001 Pylesetal. 0... 377/24.2
`
`26 Claims, 3 Drawing Sheets
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`Nuc = min(d, Nyc = 2)
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`An
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`t
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`Tat) Ta(K-2)—Ta{K-1)TA(2) ***
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`Fig.6
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`US 7,698,097 B2
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`1
`METHOD FOR CONTROLLING A
`PEDOMETER BASED ON THE USE OF
`INERTIAL SENSORS AND PEDOMETER
`IMPLEMENTING THE METHOD
`
`BACKGROUND OF THE INVENTION
`
`2
`regularity are satisfied; and preventing updating ofthe total
`numberofvalid steps if the conditions of regularity are not
`satisfied.
`
`BRIEF DESCRIPTION OF THE SEVERAL
`VIEWS OF THE DRAWINGS
`
`1. Field of the Invention
`
`The present invention relates to controlling a pedometer
`based on the use of inertial sensors.
`
`For a better understanding ofthe invention, an embodiment
`thereof is now described, purely by way of non-limiting
`example and with referenceto the attached plate of drawings,
`wherein:
`
`FIG. 1 showsa simplified andpartially sectioned perspec-
`tive view of a portable electronic device incorporating a
`pedometer according to the present invention;
`FIG.2 is a simplified block diagram of the pedometer of
`FIG.1;
`FIG. 3 shows a flowchart corresponding to a control
`method according to the present invention executed by the
`pedometer of FIGS. 1 and 2;
`FIG. 4 is a more detailed flowchart correspondingto a first
`step of the methodof FIG.3;
`FIG.5 is a graphthat represents first quantities used in the
`method according to the present invention;
`FIG.6 is a graph that represents second quantities used in
`the method according to the present invention;
`FIG. 7 is a more detailed flowchart corresponding to a
`second step of the method of FIG. 3; and
`FIG. 8 is amoredetailed flowchart correspondingto a third
`step of the methodof FIG.3.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`With reference to FIGS. 1 and 2, a pedometer 1 is inte-
`grated within a portable electronic device, such as a cell
`phone 2. The pedometer 1 comprises an inertial sensor 3, a
`control unit 5, equipped with a nonvolatile-memory module
`(not illustrated herein), a display 6, and a communication
`interface 8, all housed on a card 9, which is, in turn, fixed
`within a casing 10 of the cell phone 2. In the embodiment
`described herein, the control unit 5 performs control func-
`tions of the pedometer 1 and, moreover, presides over bi-
`directional communication and over handling of the func-
`tions envisagedfor the cell phone 2. Likewise, the display 6,
`which is obviously arranged so as to be visible from the
`outside of the casing 10, can be used for displaying both
`information regarding the pedometer 1 and, more in general,
`information regarding the operation of the cell phone 2.
`Theinertial sensor 3 is a linear accelerometer of a MEMS
`
`20
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`40
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`45
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`55
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`2. Description of the Related Art
`As is known, a pedometeris a device that can be carried by
`a user and has the function of counting the numberof steps
`during various walking or running activities for estimating
`accordingly the distance traveled. The indications supplied
`are useful for quantifying the motor activity performed by a
`personin the course ofa given period, for instance, for clinical
`purposes, for assessing the athletic performance, or even just
`for simple personalinterest.
`Thereliability of a pedometer obviously depends on the
`precision in estimating the step length of the user at the
`various rates of locomotion, but also on the selectivity in
`recognizing and ignoring events not correlated to the gait,
`which, however, cause perturbations resembling those pro-
`duced by a step. For example, many pedometers are based on
`the use of inertial sensors, which detect accelerations along a
`substantially vertical axis, and recognize that a step has been
`being made by a user whenthe timeplot of the acceleration
`signal shows given morphological characteristics. Basically,
`a step is recognized when the pedometer detects a positive
`acceleration peak (i.e., a peak directed upwards) having an
`amplitude greater than a first threshold, followed, at a dis-
`tance of some tenths of second, by a negative acceleration
`peak (directed downwards) having an amplitude greater than
`a second threshold. However, there are many random events
`that can interfere with correct recognition of the step. Impact
`or other external vibrations and given movements of the user
`can, in fact, give rise to so-called “false positives”, i.e., to
`events that are recognized as steps even though in actual fact
`they are not, because the morphological characteristics pro-
`duced are compatible. Events of this type are very frequent
`also in periods of rest, when the user, albeit not walking, in
`any case performs movements that can be detected by the
`pedometer. In the majority of cases, also “isolated” steps or
`very brief sequences of steps are far from significant and
`should preferably be ignored becausetheyare, in effect,irrel-
`(micro-electromechanical systems) type and is mounted on
`evant in regard to assessment of the motor activity for which
`the card9so as to have a detection axis Z substantially parallel
`the pedometeris being used.
`to a longitudinal axis L ofthe casing 10 ofthe cell phone 2. In
`Ofcourse,in all thesesituations, the count ofthe steps may
`practice, the detection axis Z and the longitudinal axis L are
`substantially horizontal, when the cell phone2 is resting on a
`prove to be completely erroneous.
`surface, and substantially vertical or slightly inclined with
`respectto the vertical when the cell phone 2 is handled. The
`inertial sensor 3 supplies at output an acceleration signal A,,
`which is correlated to the accelerations undergone by the
`inertial sensor 3 itself along the detection axis Z.
`The control unit 5 receives and processes the acceleration
`signal A, as explainedin detail hereinafter for identifying and
`counting a total number of valid steps N,-, made by a user
`wearing or carrying the pedometer1, for example, on his belt
`or on his shoulder. In addition, the control unit 5 is preferably
`configured for generating an estimate of the distance traveled
`by the user and other data, such as, for example, estimates of
`the average speed during movementand energy consumption.
`
`BRIEF SUMMARY OF THE INVENTION
`
`One embodiment of the present invention is a method for
`controlling a pedometer and a pedometer which overcomethe
`described above limitations.
`
`60
`
`One embodimentis a method for controlling a pedometer.
`The method includes: generating a signal correlated to move-
`ments of a user of the pedometer; detecting steps of the user
`based on the signal; checking whether sequences of the
`detected steps satisfy pre-determined conditions of regular-
`ity; updating a total numberofvalid steps if the conditions of
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`3
`The total numberof valid steps N,---and the other data possi-
`bly producedare sent to the display 6.
`The communication interface 8 in this case is based on the
`
`US 7,698,097 B2
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`4
`after the test on the state flag F,,of block 120 of FIG.3, the
`surveying procedure is executed, block 140). Otherwise (out-
`put NO from block 205), the duration of the timeinterval T.
`is comparedwith a second time threshold T.,, shorter than the
`transceiver system (known andnot shown)of the cell phone 2
`first time threshold T,, and equal, for example, to 3 s (block
`and, preferably, also comprises a port (also known and not
`215). If the second time threshold T,, has been exceeded
`shown) for communication with a computer. The communi-
`(output YES from block 215), the number of valid control
`cation interface § can thus be used both for downloading the
`steps N,. and the numberof invalid steps N,,,-are set to zero
`data produced by the pedometer 1 (amongst whichat least the
`total numberof valid steps N,,,) and for uploading operating
`(block 220); then a step-recognition test is carried out (block
`225). Otherwise (output NO from block 215), the control unit
`parameters for the pedometer 1 into the control unit 5.
`5 directly executes the step-recognition test.
`The control unit 5 is configured for executing a control
`In the step-recognition test of block 225, the control unit 5
`procedure,as illustrated with reference to FIGS. 3-8.
`Upon switching-on of the pedometer 1, an initialization
`verifies whether the time plot of the acceleration signal A,
`
`step is executed (block 100, FIG. 3), in whichafirst counter (i.e., the sequence of the samples acquired) has pre-deter-
`of the total number of valid steps N,;; a second counter,
`mined characteristics. In particular (FIG. 5), a step is recog-
`hereinafter referred to as numberofvalid control steps N;.;
`nized if the acceleration signal A, shows a positive peak,
`and a third counter, hereinafter referred to as number of
`higher than a positive acceleration threshold A;,, followed by
`invalid steps N,v;, are set to zero.
`a negative peak, smaller than a negative acceleration thresh-
`The control unit 5 then executes a first counting procedure
`old An, and if the negative peak falls within a time window
`(block 110), based upon the sampling of the acceleration
`TW ofpre-determined amplitude and, moreover, located at a
`signal A, at a pre-determined frequency, for example 25 Hz.
`pre-determined distance after the positive peak.
`In this step, the user is considered at rest and the control unit
`If the control unit 5 does not recognize an event corre-
`5 is considered as waiting to recognize, on the basis of the
`sponding to a step (output NO from block 225), a new sample
`acceleration signal A,, sequences of events corresponding to
`of the acceleration signal A, is read (block 200). If, instead,
`a sequenceofsteps thatare close to one another, whichsatisfy
`the step-recognition test is passed (output YES from block
`pre-determined conditions of regularity described in detail
`225), the control unit 5 executes a first validation test, corre-
`hereinafter. When a sequence of steps corresponding to a
`spondingto the regularity of the individual step (block 230).
`With referencealso to FIG.6, the validation occurs when the
`regular gait of the user is recognized, the first counting pro-
`cedure is interrupted. Alternatively, the first counting proce-
`duration AT, of a current step K is substantially homoge-
`dure terminates when a time interval T, that has elapsed from
`neous with respect to the duration AT,, of an immediately
`the last step recognized is longer than a first time threshold
`preceding step K-1 (the duration of a generic step is deter-
`Tx, for example 10 s. On exit from the first calculation
`mined by the time that has elapsed between an instant of
`procedure,the control unit 5 sets a state flag F.,-to a first value
`recognition of the step of which the duration is evaluated and
`C, if a sequenceof steps thatsatisfies the conditions of regu-
`an instant of recognition of the step that immediately pre-
`larity has been recognized, and to a second value PD,if the
`cedesit). More precisely, the last step recognizedis validated
`first time threshold T,, has been exceeded.
`if the instant of recognition of the current step T,(K) falls
`Atthe endofthefirst counting procedure, the control unit
`within a validation interval TV, defined with respect to the
`5 checks whetherthe state flag F,, has been set at the first
`instant of recognition of the immediately preceding step
`value C (block 120), i.e., whether a sequenceof steps has been
`T,(K-1), in the following way:
`recognized. If so (output YES from block 120), a second
`TV=[Tp(K-1)+ATg)-TA, Tp(K-1)+ATye+7B]
`counting procedure is executed (block 130). The useris con-
`sidered to be moving, andafirst counter, hereinafter referred
`where TA and TB are complementary portions ofthe valida-
`tion interval TV.
`In the embodiment of the invention
`to as total numberofvalid steps N,-,, is incremented when-
`ever an event correspondingto a step is recognized. Further-
`more, the control unit 5 checksthe regularity ofthe sequences
`of steps, as explained hereinafter, and, when an interruption in
`the locomotion is detected, the second counting procedure is
`terminated, and execution of the first counting procedure
`resumes (block 110).
`If, instead, the state flag F,, has the second value PD,the
`pedometer1 is set in a low-consumption wait state (“power
`down”state), and the control unit 5 executes a surveying
`procedure (block 140). The surveying procedure terminates
`when a variation of the d.c. component of the acceleration
`signal A, is detected, i.e., when the cell phone 2 that includes
`the pedometer 1 is moved. The control unit 5 then returns to
`execution ofthefirst calculation procedure (block 110).
`Thefirst counting procedureis illustrated in greater detail
`in FIG. 4.
`
`10
`
`40
`
`45
`
`described herein, the complementary portions TA, TB are
`defined as follows, for the generic current step K:
`TA=ATg_/2
`
`TB=ATx;
`
`Consequently,the validation interval is asymmetrical with
`respect to the instant T,(K-1)+AT,._, and has an amplitude
`equal to 3AT, ,/2. The validation interval TV could, how-
`ever, be symmetrical and have a different amplitude. In prac-
`tice, it is verified that the last step recognized is compatible
`with the frequencyof the last steps made previously.
`If the verification yields a negative result (output NO from
`block 230), the numberof invalid steps N,,,;- is incremented
`by one (block 235) before being compared with a first pro-
`grammable threshold number N,,,, for example 3 (block 240).
`If the number of invalid steps N,,; has reached the first
`threshold number N,, (output YES from block 240), both the
`numberof invalid steps N,,,;, and the numberofvalid control
`steps N,,. are set to zero (block 245), and the first counting
`procedure is resumed, with reading of a new sample of the
`acceleration signal A, (block 200). If, instead, the numberof
`invalid steps N,,;-is smaller than the first threshold number
`N-,, (output NO from block 240), the numberofvalid control
`
`Initially, the control unit 5 reads a sample of the accelera-
`tion signal A, (block 200) and then evaluates whetherthe time
`interval T,. that has elapsed from the last step recognized is
`higherthan thefirst time threshold T,,, 1-e., whether the step
`recognition fails for a period longer thanthefirst time thresh-
`old T,, (block 205). If so (output YES from block 205), the
`state flag Fis set at the second value PD (block 210) and the
`first counting procedure is terminated (in this eventuality,
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`5
`steps N,< is decremented (block 250). In the embodiment
`described herein, the decrementis equalto two. Ifthe result of
`the decrement operation is negative, the number of valid
`control steps N,- is set to zero (in practice, the updated value
`of the number of valid control steps N,. is equal to the
`smaller between zero and the previous value ofthe numberof
`valid control steps N,,., decreased by two). Then, the control
`unit 5 reads a new sample ofthe acceleration signal A; (block
`200).
`Ifthefirst validation test ofblock 230 is passed, the number
`of valid control steps N;-.is incremented by one (block 255),
`and then the control unit 5 executesa first test on regularity of
`the sequenceof steps recognized (block 260). Thefirst regu-
`larity test is based upon a first condition of regularity and
`envisages comparing the numberof valid control steps Nyc
`with a second programmable threshold number N,. greater
`thanthefirst threshold number N,, (for example, 8). In prac-
`tice, the first condition of regularity is satisfied when there is
`a significant prevalence of steps spaced in a substantially
`uniform way, at the most interrupted sporadically by a num-
`berof irregular steps smaller than the first threshold number
`N,,. If the numberofvalid control steps N;-. is smaller than
`the second threshold number N,;, (output NO from block
`260), the first condition of regularity is not satisfied, and the
`first regularity test indicates that there has not yet been iden-
`tified a sequence of steps corresponding to a sufficiently
`regular gait, and hence the control unit 5 acquires once again
`anew sampleof the acceleration signal A, (block 200), with-
`out the total numberofvalid steps N,-, being incremented.
`Otherwise (output YES from block 260), a sequence of steps
`is recognized thatsatisfies the first condition ofregularity, and
`the first regularity test is passed. The numberofinvalid steps
`N,,yand the numberofvalid control steps N,,. are set to zero,
`whereas the total numberof valid steps N,- is updated and
`incremented by a value equalto the second threshold number
`N,, (block 265). Furthermore, thestate flag F.,is set at the
`countvalue, andthefirst counting procedureis terminated. In
`this case, after the test on the state flag ofblock 120 of FIG.3,
`the second counting procedure is executed (block 130).
`In practice,the first counting procedure enables the pedom-
`eter 1 to remain waiting for a sequence of events correspond-
`ing to a sequenceofsteps thatsatisfies the first condition of
`regularity. The regularity of the gait is considered sufficient
`when the numberofvalid control steps N,. reaches the sec-
`ond threshold number N,,. The events consideredirregular or
`a waiting time that is too long between two successive steps
`cause the decrement (block 250) or the zeroing (blocks 220
`and 245) of the numberofvalid control steps N,,,, so that the
`first counting procedure resumesfrom the start. As long as the
`pedometer1 is in the waiting condition, the total numberof
`valid steps N,-; is not incremented because the useris still
`considered as at rest. However, whenthe first regularity test
`(block 260) is passed, the total numberof valid steps N,-- is
`immediately updated so as to take into accountthe valid steps
`(equal to N,.) that make up the sequence considered as being
`regular. Isolated events and sequence of steps that are in any
`case too short are thus advantageously ignored, whereas
`counting of the steps promptly resumes also in the case of
`isolated irregularities (for example, due to a non-homoge-
`neous acceleration or to a loss of balance at the start of
`locomotion).
`The possibility of programming the value of the first
`threshold number N,,, and of the second threshold number
`N,, enables modification of the sensitivity of the pedometer
`in recognizing an initial sequence of steps. For example, the
`user can program lowervaluesof the first threshold number
`N,, and of the second threshold number N,, (for example 2
`
`5
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`10
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`15
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`20
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`25
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`30
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`35
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`60
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`6
`and 4, respectively) when he remains for a long time in a
`closed environment, for example an office or a room, whereit
`would not in any case be possible to maintain a regular gait for
`a long time. In this way, shorter sequences of steps are vali-
`dated and counted. Instead, during a more constant and
`intense activity, such as running,the gait remains constant for
`a long time, and hencethefirst threshold number N,,, and the
`second threshold number N,. can be programmed with
`higher values (for example, 4 and 12, respectively). Step
`sequencesthat are shorter and notvery significantin relation
`to the activity performed can be ignored.
`FIG.7 illustrates in detail the second counting procedure
`(executed in block 130 of FIG.3).
`The control unit 5 initially reads a sample ofthe accelera-
`tion signal A, (block 300), and then evaluates whether the
`time interval T. that has elapsed from thelast step recognized
`is higher than the first second time threshold T.,, (block 305).
`Ifso (outputYES from block 205), the numberofinvalid steps
`N,yy and the numberof valid control steps N,,.. are zeroized
`(block 310), and the second counting procedureis terminated.
`Otherwise (output NO from block 305), a step-recognition
`test is carried out (block 315), identical to the step-recogni-
`tion test of block 225 of FIG.3. Also in this case, then, step
`recognition is based upon the detection of a positive peak of
`the acceleration signal A, followed by a negative peak that
`falls in the time window TW (see FIG. 5).
`If the control unit 5 does not recognize an event corre-
`sponding to a step (output NO from block 315), a new sample
`of the acceleration signal A, is read (block 300). If, instead,
`the step-recognition test is passed (output YES from block
`315), a second validation test is made, corresponding to the
`regularity of the individual step (block 320). The second
`validation test is altogether similar to the first validation test
`carried out in block 230 of FIG. 3. Also in this case, then, the
`last step recognizedis validated ifthe instant ofrecognition of
`the current step T.(K) falls within the validation interval TV
`defined above. In practice, it is verified that the last step
`recognized is compatible with the frequencyof the last steps
`made previously.
`Ifthe check yields a positive result (outputYES from block
`320), the control unit 5 updatesthe total numberofvalid steps
`N,,,and the numberof valid control steps N,,,, incrementing
`them by one (block 325). The numberofvalid control steps
`N,¢ is then compared with a third programmable threshold
`number N,, (block 330), which, in the embodimentdescribed
`herein, is equal to the second threshold number N,,. If the
`numberof valid control steps N,,.. is smaller than the second
`threshold number N,, (output NO from block 330), the con-
`trol unit 5 once again directly acquires a new sample of the
`acceleration signal A, (block 300), whereas otherwise (out-
`put YES from block 330), the numberof invalid steps Nv
`and the number of valid control steps N,< are set to zero
`(block 335) prior to acquisition of a new sample A,.
`If, instead, the secondvalidation test of block 320 is nega-
`tive, the numberof invalid steps N,,,, is incremented by one
`(block 340) before being compared with a fourth program-
`mable threshold number N,, (block 345), which,
`in the
`present embodiment, is equal to thefirst threshold number
`N,,. If the numberofinvalid steps N,,;-is smaller than the
`fourth threshold number N,,, (output NO from block 345), the
`number of valid control steps N,. is decremented (block
`350), here by two. Also in this case, if the result of the
`decrement operation is negative, the numberof valid control
`steps N;is set to zero (the updated value of the numberof
`valid control steps N,. is equal to the smaller between zero
`and the previous value of the numberof valid control steps
`N,¢, decreased by two). Then, the control unit 5 reads a new
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`7
`sample of the acceleration signal A, (block 300). If the num-
`ber of invalid steps N,,;- has reached the fourth threshold
`number N,, (output YES from block 345), the number of
`invalid steps Nand the numberofvalid control steps Ny.
`are set to zero (block 355), and the second counting procedure
`is terminated.
`
`In practice, the second counting procedure is based on a
`second condition of regularity, which is satisfied as long as
`sporadic irregular steps occur within sequences of steps
`spaced in a substantially homogeneous way. Moreprecisely,
`the second condition of regularity is satisfied as long as the
`number ofinvalid steps N,,,;-is smaller than the fourth thresh-
`old number N,,. Consequently, the second counting proce-
`dure continues to update and increment the total number of
`valid steps N,-.as long as the gaitof the user is kept regular.
`Possible isolated irregularities are ignored and do notinter-
`rupt or suspend updating of the count, which is, instead,
`interrupted when prolonged pauses occuror in the presence
`of significant discontinuities in locomotion. However, if the
`gait becomesregular again, even with a different rhythm,also
`the count promptly resumes, becausethe first counting pro-
`cedure is once again executed. This prevents a significant
`numberof steps from being neglected.
`The surveying procedure executed in block 140 of FIG. 3
`will now be describedin greater detail, with reference to FIG.
`8.
`
`Whenthe surveying procedure is started, a current mean
`value A,,, of the acceleration signal A, is stored in the non-
`volatile-memory module (notillustrated) ofthe control unit 5
`(block 400). The current mean value A,,, represents an esti-
`mate of the DC component of the acceleration signal A,,
`which, when the cell phone 2 containing the pedometer 1 is
`stationary, is determined substantially by the contribution of
`the acceleration of gravity along the detection axis Z. In
`practice, then, the current mean value A,,, provides an esti-
`mate ofthe position of the cell phone 2 and of the pedometer
`1.
`
`After storage ofthe current mean value A,,,, the pedometer
`1 is set in a low-consumption operating condition (power-
`down condition), in which at least the inertial sensor 3 is
`inactive (block 410).
`Awaiting cycle is then carried out (block 420), for example
`of the duration of 10 s, after which all the functions of the
`pedometer1 are re-activated (“power on”, block 430).
`The control unit 5 acquires from the inertial sensor 3 a
`numberof samplesofthe acceleration signal A, sufficientfor
`estimating an updated mean value A,,/ (block 440), whichis
`then compared with the current mean value A,,, previously
`stored (block 450).
`If the updated mean value A,,/ departs from the current
`mean value A,,, (output NO from block 450), the surveying
`procedure is interrupted, and the first counting procedure
`indicated in block 110 of FIG. 3 is executed. If, instead, the
`updated mean value A,,/ is substantially unvaried with
`respect to the current mean value A,,, (output YES from
`block 450), the surveying procedure proceeds and the pedom-
`eter 1 is set again in the low-consumption operating condition
`(block 410).
`Clearly, the use of the surveying procedure enables a dras-
`tic reduction in the power consumption when the pedometer
`1 is not used and, hence increases the autonomythereof.If, as
`in the embodimentdescribed, the pedometer1 is integrated in
`a portable device with which it shares the use ofresources, for
`example the control unit 5, the surveying procedure entails
`further advantages. In fact, the de-activation of the functions
`linked to the pedometer1 frees the shared resourcesfor use by
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`8
`the active functions, which can thus access the resources
`themselves in a moreefficient way.
`Finally, it is evident that modifications and variations can
`be made to the device described herein, without thereby
`departing from the scopeofthe present invention, as defined
`in the annexed claims.
`In particular, the control procedure described can be used
`to advantage in a stand-alone pedometer or in any case one
`integrated in a further portable device, but with stand-alone
`and non-shared resources.
`
`Furthermore, the conditions of regularity used to enable or
`prevent counting ofthe steps recognized can be different from
`the ones described. For example, a sequence of steps can be
`considered regular when possible steps recognized and not
`validated are separated byat least one pre-determined number
`of consecutive validated steps. Again, a sequence of a pre-
`determined number of validated or non-validated steps (se-
`quenceoffixed length) can be considered regular when the
`validated steps are at least a given percentageofthe steps of
`the sequence.
`Finally, the inertial sensor can be of the type with two or
`three axes of detection. In this case, step recognition can
`advantageously be performed by selecting the acceleration
`signal corresponding to the detection axis nearest to the ver-
`tical. The nearer the detection axis usedis to the vertical, in
`fact, the greater the amplitude of the signal useful for step
`recognition. The detection axis is selected on the basis of the
`value of the DC component of the respective acceleration
`signal, which is correlatedto the contribution ofthe accelera-
`tion of gravity. The detection axis nearest to the vertical is the
`axis along which the contributionofthe acceleration of grav-
`ity is greater. The pedometer can then be used independently
`of how it is oriented.
`The invention claimed is:
`1. A methodfor controlling a pedometer, the method com-
`prising:
`generating a signal correlated to movements ofa user ofthe
`pedometer;
`detecting steps of the user based on said signal;
`checking whether sequencesof the detected steps indicate
`whether the sequencesof the detected steps correspond
`to a regular gait of the user;
`updating a total numberof valid steps if said sequences
`correspondto the regular gait of the user;
`preventing updating of said total numberof valid steps if
`said sequences do not correspondto the regular gait of
`the user; and
`partially deactivating the pedometerif said detecting steps
`of the user based onsaid signal fails for a period longer
`than a time threshold.
`
`2. The method according to claim 1, wherein said checking
`comprises:
`in a first operating condition, checking whether a first
`condition of regularity is satisfied; and
`in a second operating condition, checking whethera sec-
`ond condition of regularity is satisfied.
`3. The method according to claim 2, wherein, during said
`checking whethersaidfirst condition ofregularity is satisfied,
`the updating of said total numberofvalid steps is prevented.
`4. The method according to claim 2, wherein, during said
`checking whether said second condition of regularity is sat-
`isfied, the updating of said total number of valid steps is
`allowed.
`
`5. A methodfor controlling a pedometer, the method com-
`prising:
`generating a signal correlated to movements ofa user ofthe
`pedometer;
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`US 7,698,097 B2
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`9
`detecting steps of the user based on said signal;
`checking whether sequences of the detected steps indicate
`whether the sequencesof the detected steps correspond
`to a regular gait of the user;
`updating a total numberofvalid steps if said sequences
`correspondto the regular gait of the user; and
`preventing updating of sai