`
`US007463997B2
`
`02) United States Patent
`Pasolini et al.
`
`(10) Patent No.:
`(45 ) Date of Patent:
`
`US 7,463,997 B2
`Dec. 9, 2008
`
`(54) PEDOMETER DEVICE AND STEP
`DETECTION METHOD USING AN
`ALGORITHM FOR SELF-ADAPTIVE
`COMPUTATION OF ACCELERATION
`THRESHOLDS
`
`(75)
`
`Inventors: Fabio Pasolini. S. Martino Siccomario
`(IT); Ivo Binda. Voghera (1T)
`
`(73) Assignee: STMicroelectronics S.r.I..Agrate
`Brianza(IT)
`
`( * ) Notice:
`
`Subject to any disclaimer. the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 3 days.
`
`(21) Appl. No.: 11/537,933
`
`(22)
`
`Filed:
`
`Oct. 2. 2006
`
`(65)
`
`Prior Publication Data
`US 2007/0143068Al
`Jun. 21. 2007
`
`(30)
`
`Foreign Application Priority Data
`
`Oct. 3. 2005
`
`(EP)
`
`.................................. 05425683
`
`(51)
`
`Int. Cl.
`(2006.01)
`GolC 22/00
`(52) US. (.‘l.
`...................................................... 702/160
`
`(58) Field ofClassiiication Search ..
`7021'I4I.
`702/15(L154. 158. 160: 600/595: 73/490.
`73/510
`
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`6.052.654 A
`6.135.951 A
`6.826.477 B2.“
`6.898.550 Bl
`200610020l77 Al“
`
`............... 7021160
`42000 (iaudetetal.
`[02000 Richardsonetal.
`......... 6001300
`1152004 Ladetto etal.
`.............. 7011217
`512005 Blackadar etal.
`........... 7021182
`112006 Seo etal.
`.................... 6001300
`
`200710073514 Al "
`200710143069 Al“
`200710198187 Al“
`
`........... 7021160
`312007 Nogimori et a1.
`
`612007 Pasoiinietai.
`.............. 7021160
`812007 Pasolinietal.
`.............. 7011220
`
`FOREIGN PATENT DOCUMENTS
`
`GB
`
`2 359 890
`
`912001
`
`3‘ cited by examiner
`
`Primary Examiner Michael P Nghiem
`(74).‘tttorm:t: Agent, orFirm Lisa K. Jorgenson: Dennis M.
`de (iuzman: Seed IP Law (iroup PI .1 .("
`
`(57)
`
`ABSTRACT
`
`In a pedometer device for detecting and counting steps of a
`user on foot. an accelerometer sensor detects a vertical accel-
`
`eration generated during the step. A processing unit. con—
`nected to the accelerometer sensor. processes an acceleration
`signal relating to the acceleration in order to detect the occur-
`rence of a step. and in particular compares the acceleration
`signal with a first reference threshold. The processing unit
`automatically adapts the first reference threshold as a func—
`tion of the acceleration signal. 1n particular. the processing
`unit modifies the first reference threshold as a function ofan
`
`envelope of the amplitude of the acceleration signal.
`
`, 583.776 A
`
`1251996 Levi et a1.
`
`................... 3641450
`
`30 Claims, 5 Drawing Sheets
`
`//
`
`PROCESSING UNIT
`
`SETTING
`
`FIRST COMPARATOR
`
`DISTANCE-CALCULATION
`
`THRESHow-ADAPTATION
`
`SECOND COMPARATOR
`
`ENVELOPE CALCULATION
`
`MEAN-VALUE CALCULATION
`
`
`
`LENGTH-ESTIMATION AXIS-DETERMINATION
`
`
`
`INTERFACE
`DISPLAY
`
`
`LGE v. Uniloc USA
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`Page 1 of 12
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`LGE Exhibit 1005
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`

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`U.S. Patent
`
`Dec. 9, 2008
`
`Sheet 1 of5
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`Us 7,463,997 B2
`
`/I
`
`PROCESSING UNIT
`
`SETTING
`
`FIRST COMPARATOR
`
`DISTANCE-CALCULATION
`
`THRESHOLD-ADAPTATION
`
`SECOND COMPARATOR
`
`INTERFACE
`
`ENVELOPE CALCULATION
`
`MEAN-VALUE CALCULATION
`
`LENGTH-ESTIMATION
`
`AXIS-DETERMINATION
`
`DISPLAY
`
`FIG. I
`
`LGE v. Uniloc USA
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`Page 2 of 12
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`LGE Exhibit 1005
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`

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`U.S. Patent
`
`Dec. 9, 2008
`
`Sheet 2 of 5
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`US 7,463,997 B2
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`LGE v. Uniloc USA
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`Page 3 of 12
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`LGE Exhibit 1005
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`

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`U.S. Patent
`
`Dec. 9, 2008
`
`Sheet 3 of5
`
`Us 7,463,997 B2
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`POSITIVE PHASE
`DETECWON
`
`
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`
`
`
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`
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`
`
`STEP
`INCREMENT
`
`STEP LENGTH
`
`ADAPTAIIQN
`
`DISTANCE
`INCREMENT
`
`"
`
`INCREMENTGFCAL- -
`SPEED COMPUTATION
`
`‘
`c-
`a °°
`
`Fig.3
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`LGE v. Uniloc USA
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`Page 4 of 12
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`LGE Exhibit 1005
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`

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`U.S. Patent
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`Dec. 9, 2008
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`Sheet 4 of5
`
`US 7,463,997 B2
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`DETERMINATION OF ACCELERATION DATUM
`CalAcc AND THRESHOLD ADAPTATION
`
`11 18
`'
`
`ACQUISITION OF
`ACCELERATION SAMPLE Acc
`
`ELIMINATION OF M. COMPONENT
`AND DETERMINATION OF CalAOC
`
`30
`
`31
`
`34
`
`32
`
`
`Env” = ufiEnv‘
`(“1 < 1)
`
`.
`
`‘ ‘ H
`-
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`35
`
`NO-YES
`
`
`37
`
`(a2 < 1)
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`Calec < Env-
`
`nv
`
`a cc
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`5’ = [3" Env’
`(B < 1)
`.
`38
`
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`39
`
`46
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`-"°@--.t = S‘
`
`
`S'= B‘ EHV'
`(B < 1)
`
`No 9 YES m
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`43
`
`
`
`Fig.4
`
`LGE v. Uniloc USA
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`Page 5 of 12
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`LGE Exhibit 1005
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`

`

`U.S. Patent
`
`Dec. 9, 2008
`
`Sheet 5 of5
`
`US 7,463,997 B2
`
`CaIAcc
`
`:
`:
`-
`I
`CE
`'.
`I-
`‘1
`X
`i
`IaII'i‘IsI-IW-I
`I..'.I-i1 II!
`:4, lIIlIiiIIII.IIIIIIIIIIIIIIII I IIIIIIHIIIE IIIIIIII IIIIIIH IIUII. In}.
`S
`"IIIIII"IIIIIIIIIIIIIIIIIIIIII"I IIIIIIIIIIIII IIIIIIIIIIIII IIIIIIIIIIIIIIIII. I” N .
`()1
`S “JIJIIIIIIIIIIIIIIIIII'IIIIIIIIIIIIIIWIIIIIIIIIIIIIII”II“I”IIIIIIIIIJIIHI“HQ-L!'L_
`2
`4 7]
`! I‘IIIIIIIJE‘IEII' Iriflilfill‘uéfl IEIEIII'I' 1W WSW“
`
`/ +
`
`10
`
`Fig.6
`
`PARAMETER
`INITIALIZATION
`
`DETERMINATION OF ACCELERATION DATUM
`CalAcc AND THRESHOLD ADAPTATION
`
`POSITIVE PHASE DETECTION
`CalAcc > S+
`
`
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`
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`HAS A
`POSITIVE PHASE BEEN
`DETECTED?
`
`STEP INCREMENT
`
`STEP LENGTH ADAPTATION
`
`DISTANCE INCREMENT
`
`
`
`INCREMENT OF’GALORIE
`SPEED COMPUTATION
`
`Fig.7
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`LGE v. Uniloc USA
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`Page 6 of 12
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`LGE Exhibit 1005
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`

`

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`US 7,463,997 B2
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`
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`1
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`PEDOMETER DEVICE AND STEP
`
`
`
`
`DETECTION METHOD USING AN
`
`
`
`
`ALGORITHM FOR SELF-ADAPTIVE
`
`
`
`COMPUTATION OF ACCELERATION
`
`
`THRESHOLDS
`
`
`
`BACKGROUND OF THE INVENTION
`
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`1. Field of the Invention
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`The present invention relates to a pedometer device and to
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`a step detection method using an algorithm for self-adaptive
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`computation of acceleration thresholds.
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`2. Description of the Related Art
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`Step-counting devices (referred to in general as pedom-
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`eters) are known, which, being carried by a user, enable
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`measurement ofthe number of steps made, and calculation of
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`the distance traveled, as well as supplying of additional infor-
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`mation, such as, for example, the average speed, or the con-
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`sumption of calories.
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`Pedometers are advantageously used in inertial navigation
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`systems (the so-called dead-reckoning systems) applied to
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`human beings. Such systems trace the movements of a user,
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`by identifying and measuring his/her displacements starting
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`from a known starting point, without resorting to the use of a
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`Global Positioning System (GPS), or by acting as aid to a
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`GPS. In said systems, a compass supplies the information
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`linked to the direction of displacement, and the pedometer
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`supplies the information linked to the amount of said dis-
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`placement. Pedometers are also used in a wide range of appli-
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`cations in the clinical sector (for example, in rehabilitation),
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`and in general in the field of fitness (for example, as instru-
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`ments for monitoring a physical activity).
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`In particular, pedometers are known that use integrated
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`accelerometers of a MEMS (micro-electromechanical sys-
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`tem) type for step detection. In particular, such pedometers
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`have particularly compact dimensions, and can be advanta-
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`geously integrated within portable devices, such as mobile
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`phones, Mp3 readers, camcorders, etc.
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`The aforesaid pedometers implement a step detection
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`method based upon the analysis of the pattern of a vertical
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`acceleration, which is generated during the various phases of
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`the step by the contact of the foot to the ground, and which is
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`detected by an accelerometer fixed to the body of the user. In
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`this connection, it is emphasized that “vertical acceleration”
`means herein an acceleration directed along the vertical ofthe
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`user’s body. In particular, the occurrence of a step is deter-
`mined by identifying acceleration peaks that appear in the
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`acceleration signal, and said peaks are detected by comparing
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`the acceleration signal with a given reference threshold, hav-
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`ing a pre-set value.
`However, even though the acceleration signal has a profile
`that is repeatable at each step, its pattern (and, in particular, its
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`amplitude and temporal extension) has a wide variability
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`according to a number of factors that affect the gait, such as
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`the resting surface, the type of shoe worn (rigid sole or flex-
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`ible sole, etc.), and the speed of the gait (slow walking, fast
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`walking, running, etc.). Furthermore, each individual user has
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`given characteristics and peculiarities that affect the gait,
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`differentiating it from that of other users.
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`It follows that a step detection based upon the comparison
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`ofthe value ofthe acceleration signal with a reference thresh-
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`old having a pre-set value for the detection of acceleration
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`peaks, involves the occurrence of errors that may even be
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`considerable in counting ofthe steps, and in the measurement
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`of the distance traveled. In particular, if the threshold is too
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`low, spurious signals, rebounds, or noise in general, may be
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`10
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`15
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`55
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`counted as steps; on the other hand, if the threshold is too
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`high, some steps may not be detected.
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`2
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`BRIEF SUMMARY OF THE INVENTION
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`invention provides a
`One embodiment of the present
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`pedometer device and a method for detecting and counting
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`steps which will enable the aforesaid disadvantages and prob-
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`lems to be overcome.
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`One embodiment ofthe invention is a pedometer device for
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`detecting and counting the steps ofa user. The device includes
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`an accelerometer sensor configured to detect an acceleration
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`generated during a step; and a processing unit connected to
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`the accelerometer sensor, and configured to process an accel-
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`eration signal relating to the acceleration to detect the occur-
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`rence of a step. The processing unit includes a first compara-
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`tor configured to compare the acceleration signal with a first
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`reference threshold, and a threshold-adaptation circuit con-
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`figured to modify the first reference threshold as a function of
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`the acceleration signal.
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`One embodiment of the invention is a step detection
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`method for detecting steps in the gait of a user. The method
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`includes producing an acceleration signal relating to an accel-
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`eration generated during a step; and processing the accelera-
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`tion signal to detect the occurrence ofthe step. The processing
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`step includes comparing the acceleration signal with a first
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`reference threshold, and modifying the first reference thresh-
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`old as a function of the acceleration signal.
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`BRIEF DESCRIPTION OF THE SEVERAL
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`VIEWS OF THE DRAWINGS
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`For a better understanding of the present invention, pre-
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`ferred embodiments thereof are now described, purely by
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`way of non-limiting example and with reference to the
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`attached drawings, wherein:
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`FIG. 1 shows a block diagram of a pedometer device;
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`FIG. 2 shows a graph corresponding to the pattern of an
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`acceleration signal during a step;
`FIG. 3 shows a flowchart corresponding to operations of
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`detection and counting of steps, executed by a processing unit
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`of the pedometer device of FIG. 1;
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`FIG. 4 shows a flowchart corresponding to operations of
`self-adaptive modification of acceleration thresholds,
`executed by the processing unit of the pedometer device of
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`FIG. 1;
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`FIGS. 5-6 are graphs corresponding to the pattern of an
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`acceleration signal during a step and of reference thresholds
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`associated to the algorithm of FIG. 3;
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`FIG. 7 shows a possible variant of the flowchart of FIG. 3;
`and
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`FIG. 8 is a partially exploded schematic view of a portable
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`in particular a mobile phone,
`incorporating the
`device,
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`pedometer device of FIG. 1.
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`DETAILED DESCRIPTION OF THE INVENTION
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`FIG. 1 is a schematic illustration of a pedometer device 1,
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`comprising an accelerometer 2, of a linear type and having a
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`vertical detection axis z, and a processing unit 3, connected to
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`the accelerometer 2. Advantageously, the accelerometer 2
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`and the processing unit 3 are mounted on the same printed
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`circuit, housed inside a casing of the pedometer device 1 (not
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`illustrated). The pedometer device 1 is carried by a user, for
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`example on his belt or on his shoulder, so as to be fixed to the
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`LGE V. Uniloc USA
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`Page 7 of 12
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`LGE Exhibit 1005
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`LGE v. Uniloc USA
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`Page 7 of 12
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`LGE Exhibit 1005
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`

`

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`US 7,463,997 B2
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`3
`body of the user and be able to sense vertical accelerations
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`that occur during the step, caused by the impact of the feet on
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`the ground.
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`The pedometer device 1 further comprises a display screen
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`4, connected at an output of the processing unit 3, and an
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`interface 5, connected at an input ofthe processing unit 3. The
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`display screen 4 displays information at output from the
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`pedometer device 1, such as the number of steps, the distance
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`traveled, etc. The interface 5, for example, including push-
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`buttons, an alphanumeric keypad, communication ports, etc.,
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`allows the user to communicate with the processing unit 3 (for
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`example, by entering data).
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`The accelerometer 2 is advantageously an integrated sen-
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`sor of semiconductor material, made using the MEMS tech-
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`nology, of a known type and thus not described in detail
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`herein. In use, the accelerometer 2 detects the component
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`ated during the step, and produces a corresponding accelera-
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`tion signal A.
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`As shown in FIG. 2, the pattern ofthe acceleration signal A
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`(with the dc. component filtered out) in time t has a given
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`acceleration profile which repeats at each step (indicated by
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`the dashed rectangle). In detail, the acceleration profile com-
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`prises in succession: a positive phase, in which a positive-
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`acceleration peak occurs (i.e., directed upwards), due to con-
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`tact and consequent impact of the foot with the ground; and a
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`negative phase in which a negative-acceleration peak occurs
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`(i.e., directed downwards) due to rebound, having an absolute
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`value smaller than that of the positive-acceleration peak.
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`The processing unit 3, comprising a microprocessor circuit
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`(for example, a microcontroller or DSP), acquires at pre-set
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`intervals samples of the acceleration signal A generated by
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`the accelerometer 2, and executes appropriate processing
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`operations for counting the number of steps and measuring
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`the distance traveled. As will be described in detail hereinaf-
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`ter, the processing unit 3 compares the value of the accelera-
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`tion signal A (with the dc. component filtered out) with a
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`positive reference threshold S+ and with a negative reference
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`threshold S", for identifying, respectively, the positive phase
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`(positive acceleration peak) and the negative phase (negative
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`acceleration peak) of the step.
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`According to one embodiment ofthe present invention, the
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`values ofthe positive and negative reference thresholds S“, S"
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`are not fixed and equal to a given pre-set value, but are
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`calculated in a self-adaptive way (i.e., in a way that adapts
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`without any external intervention from a user) by the process-
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`ing unit 3, based on the values assumed by the detected
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`acceleration. In particular, as will be clarified hereinafter, the
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`values ofthe positive and negative reference thresholds 8", S—
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`are modified at each acquisition of a new sample of the
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`acceleration signal A, as a function of the value of a positive
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`and negative amplitude envelope ofthe acceleration signal, in
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`such a manner that the reference thresholds vary with time
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`approximately following said envelopes. The pedometer
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`device 1 thus adapts to variations in the detection conditions
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`signal, in terms of amplitude and duration), due, for example,
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`to a different type of terrain, or to an increase in the speed of
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`the gait.
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`The algorithm implemented by the processing unit 3 for
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`performing, among other things, the operations of step count-
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`ing and of traveled distance measurement is now described,
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`with reference to FIG. 3. Said algorithm envisages the analy-
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`sis of the acceleration signal A in order to look for a positive
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`phase ofthe step followed by a negative phase within a pre- set
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`time interval from the occurrence of the positive phase. In the
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`case where said sequence occurs (which indicates the occur-
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`4
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`rence of a step), counting ofthe steps and measurement ofthe
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`total distance traveled are updated; otherwise, the algorithm
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`returns to the initial condition of looking for a new positive
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`phase ofthe step. In particular, the positive acceleration peaks
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`that occur within the pre-set time interval are ignored by the
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`algorithm (in so far as they can be ascribed to phenomena of
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`noise, such as impact, anomalous rebounds, etc.).
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`In detail, the algorithm starts with initialization, block 10,
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`ofthe values ofthe positive and negative reference thresholds
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`S+ and S", respectively, at a positive minimum value S1 and at
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`a negative minimum value 82, the latter being smaller, in
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`absolute value, than the positive minimum value 81. As will
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`be clarified, said minimum values represent limit values
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`below which the reference thresholds are not allowed to drop.
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`In addition, the values of a positive envelope Env+ and of a
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`negative envelope Env' of the acceleration signal A (which
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`will subsequently be used for modification of the reference
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`thresholds) are initialized, respectively, at the positive mini-
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`mum value S1 and at the negative minimum value 82.
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`Next, block 11, the processing unit 3 determines a first
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`acceleration datum CalAcc, and consequently modifies the
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`values of the reference thresholds (as will be described in
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`detail hereinafter with reference to FIGS. 4 and 5).
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`The algorithm then proceeds, block 12, with the search for
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`the positive phase of the step, by comparing the value of the
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`acceleration datum CalAcc with the positive reference thresh-
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`old S+, to detect a positive acceleration peak of the accelera-
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`tion signal A.
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`Until a positive phase of the step is found, block 13, the
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`algorithm proceeds with acquisition of a new acceleration
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`datum CalAcc in block 11 (and corresponding modification
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`of the reference thresholds), and with the comparison of said
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`new acceleration datum with the positive reference threshold
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`8*.
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`The positive phase is detected when the acceleration datum
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`exceeds the positive reference threshold S+ and then drops
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`below the positive reference threshold, the instant of detec-
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`tion of the positive phase corresponding to the instant in
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`which the acceleration datum drops again below the positive
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`reference threshold 8". At this instant, the processing unit 3
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`stores the value assumed by the positive reference threshold
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`8", which is a maximum value Strum.
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`After the positive phase detection, the algorithm proceeds
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`with the search for the negative phase of the step, block 14,
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`i.e., of a negative acceleration peak, by comparing the value
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`ofthe acceleration datum CalAcc with the negative reference
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`threshold 8'. Inparticular, the search for the negative phase of
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`the step is executed within a certain time interval Mask, the
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`value of which must be lower than a maximum interval Max-
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`_Mask from detection ofthe positive phase (corresponding to
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`a certain number of samples, the value ofwhich is determined
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`also as a function of the sampling rate of the acceleration
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`data).
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`Until a negative acceleration peak is detected, block 15,
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`and as long as the time interval Mask is shorter than the
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`maximum interval Max_Mask, block 16, the algorithm pro-
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`ceeds with the search for the negative phase of the step. In
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`detail, the time interval Mask is incremented, block 17, a new
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`acceleration datum CalAcc is acquired (and the values of the
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`reference thresholds are modified accordingly), block 18
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`(which is equivalent to block 11), and the algorithm returns to
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`block 14. If no negative phase of the step has been identified
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`after expiry of the maximum interval Max_Mask, block 16,
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`the algorithm returns to block 11 in order to look for a new
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`potential positive phase of the step.
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`On the contrary, if the negative phase is identified within
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`the maximum interval Max_Mask (i.e.,
`the acceleration
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`LGE V. Uniloc USA
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`Page 8 of 12
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`LGE Exhibit 1005
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`LGE v. Uniloc USA
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`Page 8 of 12
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`LGE Exhibit 1005
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`

`

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`US 7,463,997 B2
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`5
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`datum drops below the negative reference threshold S"), the
`processing unit 3 determines the occurrence of 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 of the length of the
`current step LPS.
`In detail, according to one embodiment of the present
`invention, block 21, the processing unit 3 calculates the esti-
`mate of the length of the current step LPS as a function of the
`maximum value S+max reached by the positive reference
`threshold S+ during the positive phase of the step, which is
`indicatory of the value of the positive acceleration peak. The
`actual length ofthe step varies with respect to a standard value
`determined on the basis 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 current step LPS is calculated via
`the formula:
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`10
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`15
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`LPS:LP1(S*W)
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`where LP is a standard length ofthe step, corresponding to 0.4
`to 0.5 times the height of the user, and f(S+max) is a corrective
`function, for example a linear one, based upon the maximum
`value SUM. The corrective function f(S+maX) canbe tabulated
`on the basis ofexperimental tests, which enable association to
`a given maximum value S+max of an appropriate correction to
`be made to the standard length ofthe step LP. Inparticular, the
`function f(S+max) is conveniently stored in the processing unit
`3.
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`The algorithm then proceeds, block 22, by increasing the
`distance traveled on the basis of the estimate of the length of
`the 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 consumption of calories per step), and the
`average and instantaneous speed of travel, which are calcu-
`lated in a known way not described in detail herein.
`Next, the algorithm returns to block 11 in order to detect a
`new acceleration profile indicating occurrence of a step.
`There will now be described in detail, with reference to
`FIG. 4, the algorithm implemented by the processing unit 3
`for determination of a new acceleration datum CalAcc and
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`consequent updating ofthe values ofthe positive and negative
`reference thresholds S+ and S", in such a manner that the
`aforesaid values will follow approximately the positive and
`negative envelope of the acceleration signal.
`In brief, said algorithm envisages calculation, for each new
`acceleration datum CalAcc, ofthe values ofthe positive enve-
`lope Env+ and negative envelope Env', and modification of
`the value of the positive and negative reference thresholds S+
`and S" as a function of the positive envelope Env+ and nega-
`tive envelope Env', respectively.
`In detail,
`in an initial block 30, the processing unit 3
`acquires from the accelerometer 2 a new acceleration sample
`Acc ofthe accelerationA. Then, block 31, the dc. component
`of said acceleration value (due substantially to the accelera-
`tion of gravity) is eliminated so as to determine the accelera-
`tion datum CalAcc, with zero mean value, which will be used
`subsequently in the algorithm. In detail, the mean value Accm
`of the acceleration sample Acc is calculated with the expres-
`s10n:
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`Accm :y-Accm+(l —y)- CalAcc
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`where y is a constant between 0 and l, for example equal to
`0.95, andAccm and CalAcc are the values, respectively, ofthe
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`6
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`mean value and of the acceleration datum, which were cal-
`culated at the previous acquisition. The new acceleration
`datum CalAcc is calculated by applying the relation:
`CaZACC:ACC—Accm
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`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
`CalAcc is higher than the value of the positive envelope Env+
`(as calculated at the previous acquisition), 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; i.e., the previous value is mul-
`tiplied by a first constant a1<l, for example, (x1:0.9458. 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
`CalAcc is smaller than the negative envelope Env' (as calcu-
`lated at the previous acquisition), the new value of the nega-
`tive envelope Env' is set equal to the value of the acceleration
`datum CalAcc, block 36. Otherwise, block 37, the value ofthe
`negative envelope Env' is set equal to a proper fraction ofthe
`previous value of the envelope; i.e., it is multiplied by a
`second constant a2<l, for example, (x2:0.9438. Note, in par-
`ticular, that the different value of the first and second con-
`stants (x1, azis 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
`rebound of the 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 value of the
`positive reference threshold S+ is set equal to a certain proper
`fraction of the positive envelope Env+; in particular, it is set
`equal to the value of the positive envelope Env+ multiplied by
`a third constant [3<l, for example, [3:065 However, if the
`value thus calculated is less than the positive minimum value
`81, block 39, the value of the positive reference threshold S+
`is set at said positive minimum value 81, block 40.
`Likewise, block 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
`by the third constant [3. However, once again, ifthe value thus
`calculated is less than the negative minimum value 82, block
`42, the value ofthe negative reference threshold 8' is set at the
`negative minimum value 82, block 43.
`The values of the new reference thresholds thus calculated
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`are then used for detection of the positive and negative phases
`of the step, as described previously.
`FIGS. 5 and 6 show the curves of the positive and negative
`reference thresholds S“, S", and of the 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 of the 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 1 (see, in
`particular, FIG. 6), and remains constant as long as the accel-
`eration datum CalAcc remains less than the positive accel-
`eration threshold 8". Starting from the instant at which the
`acceleration datum CalAcc exceeds the positive acceleration
`
`LGE V. Uniloc USA
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`Page 9 of 12
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`LGE Exhibit 1005
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`LGE v. Uniloc USA
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`Page 9 of 12
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`LGE Exhibit 1005
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`

`

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`US 7,463,997 B2
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`7
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`threshold 8+, and as long as the acceleration datum CalAcc
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`increases, the positive acceleration threshold S+ follows, in a
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`“damped” way, the increase ofthe acceleration datum CalAcc
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`in particular, FIG. 5). Next, the acceleration datum
`(see,
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`CalAcc starts to decrease, and, along with it, the positive
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`acceleration threshold S“, which, as long as the acceleration
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`datum CalAcc decreases, assumes a decreasing pattern (with-
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`out, however, dropping below the positive minimum value
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`Sl). In particular, at the end of the positive phase of the step,
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`the maximum value S+max is stored. The positive reference
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`threshold S+ returns to the positive minimum value Sl when
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`the user comes to a halt. A similar pattern (in absolute value)
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`is showed by the negative acceleration threshold S", with the
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`difference that the decrease (in ab solute value) ofthe negative
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`acceleration threshold S" is different, in particular faster. Said
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`difference is due to the different conformation ofthe negative
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`acceler