US 7,409,291 B2
`(10) Patent No.:
`a2) United States Patent
`Pasoliniet al.
`(45) Date of Patent:
`Aug. 5, 2008
`
`
`US007409291B2
`
`(54) DEVICE FOR AUTOMATIC DETECTION OF
`STATES OF MOTION AND REST, AND
`PORTABLE ELECTRONIC APPARATUS
`INCORPORATINGIT
`
`(75)
`
`.
`.
`.
`Inventors: Fabio Pasolini, S. Martino Siccomario
`(IT); Ernesto Lasalandra, S. Donato
`Milanese(IT)
`(73) Assignee: STMicroelectronics S.r1., Agrate
`Brianza (IT)
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`
`rec. Hsab)by734,de under 3
`(21) Appl. No.: 10/789,240
`
`(22)
`
`Filed:
`
`Feb. 26, 2004
`
`(65)
`
`Prior Publication Data
`
`US 2004/0172167 Al
`
`Sep. 2, 2004
`
`(51)
`
`Int. Cl.
`(2006.01)
`GOIC 21/00
`(52) US. Cl]. occ ccccccecceeeeseeeee 701/220; 700/245; 74/5 R
`(58) Field of Classification Search ................. 700/245,
`700/258, 108, 67; 701/220; 74/5 R, 5.34,
`74/5.46
`See application file for complete search history.
`References Cited
`U.S. PATENT DOCUMENTS
`
`(56)
`
`............ 74/5.34
`4/1989 Hartmann etal.
`4,823,626 A *
`8/1998 Jeenicke et al... 280/735
`5,788,273 A *
`6,320,822 B1* 11/2001 Okeyaetal. woe 368/66
`6,463,347 Bl
`10/2002 Nevruzet al.
`... 700/245
`6,463,357 B1* 10/2002 Anetal.
`.....
`
`6,512,310 BL*
`1/2003. Ohnishi
`...........
`307/121
`5/2004 Ishiyamaetal. seceess.- 360/75
`6,738,214 B2*
`2/2005 Zerbinietal. ............ 200/6 1.08
`6,858,810 B2*
`2002/0033047 Al*
`3/2002 Oguchiet al.
`.....00.0.. 73/514.16
`
`* cited by examiner
`
`Primary Examiner—KhoiH. Tran
`Assistant Examiner—Marie A Weiskopf
`(74) Altorney, Agent, or Firm—Lisa K. Jorgenson; Robert
`Jannucci; Seed IP Law Group PLLC
`
`(57)
`
`ABSTRACT
`
`A devicefor automatic detection of states of motion andrest
`includesat least one inertial sensor, having at least one pref-
`erential detection axis, and a converter, which is coupled to
`the inertial sensor and supplies a first signal correlated to
`forces acting on the first inertial sensor according to the
`preferential detection axis; the device further includes at least
`one processing stage for processing the first signal, which
`supplies a second signal correlated to a dynamic component
`of the first signal, and at least one threshold comparator,
`which supplies a pulse when the second signal exceeds a
`pre-determined threshold.
`
`3,490,719 A *
`
`1/1970 Volpe et al. we 244/169
`
`
`
`28 Claims, 2 Drawing Sheets
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`U.S. Patent
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`Aug. 5, 2008
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`US 7,409,291 B2
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`Sheet 1 of 2
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`U.S. Patent
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`Aug.5, 2008
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`Sheet 2 of 2
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`US 7,409,291 B2
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`US 7,409,291 B2
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`1
`DEVICE FOR AUTOMATIC DETECTION OF
`STATES OF MOTION AND REST, AND
`PORTABLE ELECTRONIC APPARATUS
`INCORPORATINGIT
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to a device for automatic
`detection of states of motion andrest and to a portable elec-
`tronic apparatus incorporating it.
`2. Description of the Related Art
`Asis known,reduction of power consumptionis one of the
`main objectives in any sector of modern microelectronics. In
`somefields, however, power consumption has an even deter-
`mining importance in the evaluation the quality of a product.
`Many widely used electronic devices, in fact, are provided
`with a stand-alone battery supply and are normally discon-
`nected from the mains supply; this is, for example, the case of
`cell phones and cordless phones, of palm-top computers and
`radio frequency pointer devices for computers (mouses and
`trackballs). It is clear that the reduction both of supply volt-
`ages and of currents advantageously involves an increase in
`the autonomyof the device and hence a greater convenience
`of use.
`Furthermore, frequently the cited above devices are effec-
`tively usedjustfor briefperiods, whereas for most ofthe time
`in which they are on they remain inactive. Consider, for
`example, the ratio between the duration of a call from a cell
`phoneandthe average time between two successive calls. Itis
`clear that, for almost the entire period of operation, the cell
`phone remains inactive, but is in any case supplied and thus
`absorbs a certain power. In effect, the autonomyofthe device
`is heavily limited.
`Somedevices, after a pre-determinedinterval ofinactivity,
`can be automatically set in a wait state (stand-by), in whichall
`the functions not immediately necessary are deactivated; for
`example, ina cell phoneit is possible to turn offthe screen and
`all the circuitry that is not involved in identifying an incoming
`call.
`To reactivate the devices from stand-by,it is advantageous
`to exploit a signal linked to an event (such as, for example,
`reception ofa call signal, in the case ofcell phones). However,
`since itis not alwayspossible to associate a signal to an event
`(for example, in the case where it is the user who wants to
`make a call), normally a reactivation key is provided, that the
`user can press for bringing back the device into a normal
`operative state.
`In this case, however, one drawbacklies in that the device
`is not immediately ready foruse: the user mustin fact pick up
`the device, press the reactivation key and wait for the extinc-
`tion of a transient in which the functions previously deacti-
`vated are restored. Although this transient is relatively brief
`(at the most in the region of one second), it is not however
`negligible and in somecases can render the device altogether
`inefficient. For example, in a radio frequency mouse, the
`restore time would be so long that the advantage of having
`low consumption in stand-by would be basically nullified by
`the lowerefficiency of use.
`It would, instead, be desirable to have available a device
`incorporated in an apparatusthatis able to generate automati-
`cally a reactivation signal when the apparatusis to be used.
`
`BRIEF SUMMARYOF THE INVENTION
`
`One embodimentofthe present invention provides a device
`and an apparatus that enables the problem described above to
`be solved.
`One embodimentof the present invention is a device for
`automatic detection of states of motion and rest. The device
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`includesan inertial sensor having a preferential detection axis
`and a converter coupled to the inertial sensor and supplying a
`first signal correlated to forces acting on the first inertial
`sensor according to the preferential detection axis. The device
`also includes a processing stage structured to processthefirst
`signal and supply a secondsignal correlated to a dynamic
`component ofthe first signal; and a threshold comparator
`supplying a pulse when the second signal exceeds a pre-
`determined threshold.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`For a better understanding ofthe invention, an embodiment
`thereof is now described, purely by way of non-limiting
`example and with reference to the attached drawings,
`in
`which:
`FIG.1 illustrates a simplified block diagram of an appara-
`tus incorporating a device made according to the present
`invention;
`FIG.2 illustrates a more detailed circuit block diagram of
`the device according to the present invention; and
`FIG.3 is a schematic plan view ofa detail of the device of
`FIG.2.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`With reference to FIG. 1, designated, as a whole, by the
`reference number1 is a portable electronic apparatus, which,
`in the example illustrated herein,is a palm-top computer; this
`must not, however, be considered in any way limiting, in so
`far as the apparatus 1 could also be of a different type. The
`apparatus 1 comprises at least one battery 2, a control unit 3,
`a memory 4, an input/output (1/O) unit 5 (for example an
`infrared serial port), a screen 6, a counter 8 and an activation
`device 10.
`An output 2a of the battery 2, which supplies a supply
`voltage Vp, 1s connected to respective supply inputs of the
`control unit 3, the memory 4, the I/O unit 5, the screen 6, the
`counter 8 andthe activation device 10.
`Furthermore, the control unit 3, the memory 4, the I/O unit
`5 andthe screen 6 have: respective stand-by inputs connected
`to an output 8a of the counter 8, which supplies stand-by
`pulses STBY;and respective activation inputs, connected to
`an output 10a of the activation device 10, which supplies
`activation pulses WU (“Wake-Up”). Furthermore, the counter
`8 has accounting input connectedto an output 3a@ ofthe control
`unit 3, which supplies a counting signal CT.In the presence of
`a first value of the counting signal CT, the counter 8 is dis-
`abled; when the counting signal CT switches from thefirst
`value to a second value, the counter 8 is reset and then incre-
`mented at each clock cycle. If the counter 8 reaches a pre-
`determined threshold counting value, a stand-by pulse STBY
`is generated.
`During normal operation of the apparatus 1 (active state),
`the control unit 3 maintains the counting signal CTatthe first
`value, disabling the counter 8. When,instead, the control unit
`3 recognizes a condition in which the apparatus 1 is turned on,
`but is not used (for example, when the control unit 3 must
`execute only wait cycles), the counting signal is set at the
`second value, and the counter 8 is thus activated. After a
`pre-determinedperiodof inactivity, the counter 8 reaches the
`threshold counting value and supplies at output a stand-by
`pulse STBY;in this way, the control unit 3, the screen 6, the
`J/O unit 5 and the memory 4 areset in a stand-bystate,i.e., in
`an inoperative mode in which power consumption is mini-
`mized.
`The activation device 10, the structure of which will be
`described in detail hereinafter, detects the accelerations to
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`US 7,409,291 B2
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`tively. Moreover, the activation device 10 comprises: a mul-
`which the apparatus 1 is subjected, preferably alonga first
`tiplexer 24; a capacitance-voltage (C-V) converter 25; a
`axis X, a second axis Y and a third axis Z orthogonalto one
`demultiplexer 26; a first detection line 28; a second detection
`another and fixed to the apparatus 1. More precisely, the
`line 29 and a third detectionline 30, associated respectively to
`activation device 10 detects both the static accelerations (due
`the first inertial sensor 20, to the secondinertial sensor 21 and
`to constant forces, like the force of gravity) and dynamic
`to the third inertial sensor 22; an output logic gate 31; anda
`accelerations (due to non-constant forces) to which the appa-
`phase generator 32.
`ratus 1 is subjected.
`First stator terminals 20a, 21a, 22a and secondstatorter-
`Whenthe apparatus1 is not used, it usually remains sub-
`minals 205, 216, 225 respectively ofthe first, second and third
`stantially immobile or in any case subjected to forces of
`inertial sensors 20, 21, 22 are selectively connectable in
`negligible intensity, for example because it is resting on a
`sequenceto detection inputs 25a, 255 ofthe C-V converter 25
`shelf. As has been mentioned previously, after a pre-deter-
`via the multiplexer 24. For this purpose, a control input 24a of
`mined timeinterval, the apparatus 1 goes into a stand-bystate.
`
`In these conditions, the activation device 10 detects dynamic the multiplexer 24 is connectedtoafirst output of the phase
`
`accelerations which are practically zero and maintains its generator 32, which suppliesafirst selection signal SEL1.
`output 10a@ constant at a resting logic value; the apparatus 1
`The C-V converter 25 is based upon a differential charge-
`thus remainsin stand-by.
`amplifier circuit, of a type in itself known, and has a timing
`Whenthe dynamic accelerations directed along at least one
`input 25c, connected to a second output ofthe phase generator
`of the three axes X, Y, Z exceed a pre-determined threshold,
`32, which supplies timing signals CK, and an output 25d,
`the activation device 10 generates an activation pulse WU
`which supplies, in sequence, sampled valuesofa first accel-
`thus bringing its output 10a to an activation logic value. In the
`eration signal A,, a second acceleration signal A,-and a third
`acceleration signal A,, correlated to the accelerations along
`presence of an activation pulse WU, any possible standby
`pulses STBYare ignored, and the controlunit 3, the screen 6,
`the first, second andthird axes X, Y, Z, respectively.
`the I/O unit 5 and the memory4 areset in the active state. The
`The demultiplexer 26 connects the output of the C-V con-
`activation pulse WU terminates whenall the dynamic accel-
`verter 25 selectively and in sequence to respective inputs of
`the first, second and third detection lines 28, 29, 30, which
`erations alongthefirst axis X, the second axis Y andthe third
`axis Z return below the pre-determined threshold.
`thus receive respectively the first, second andthird accelera-
`The activation device 10 is based upon capacitive-unbal-
`tion signals Ay, A,, Az. For this purpose, the demultiplexer 26
`ancelinearinertial sensors, made using MEMS(Micro-Elec-
`has a control input 26@ connected to a second output of the
`tro-Mechanical Systems) technology. For greater clarity,
`phase generator 32, which supplies a secondselection signal
`SEL2.
`FIG.2 illustrates a first inertial sensor 20, having a preferen-
`Eachofthe detection lines 28, 29, 30 comprises a subtrac-
`tial detection axis parallel to the first axis X.
`In detail, the first inertial sensor 20 comprises a stator 12 tor node 34,afilter 35, of a low-pass type, and a threshold
`
`and a moving element 13, connected to one another by means
`comparator 36. In greater detail, the input of each detection
`of springs 14 in such a waythat the moving element 13 may
`line 28, 29, 30 is directly connected to a non-inverting input
`34a of the adder node 34 and is moreover connected to an
`translate parallel to the first axis X, whereas it is basically
`fixed with respect to the second axis Y and thethird axis Z (in
`FIG.2, the third axis Z is orthogonalto the planeofthe sheet).
`Thestator 12 and the moving element13 are provided with
`a plurality of first and second stator electrodes 15', 15" and,
`respectively, with a plurality of mobile electrodes 16, which
`extend basically parallel to the plane Y-Z. Each mobile elec-
`trode 16 is comprised between two respective stator elec-
`trodes 15', 15", which it partially faces; consequently, each
`mobile electrode 16 forms with the two adjacentfixed elec-
`trodes 15', 15" a first capacitor and, respectively, a second
`capacitor with plane and parallel faces. Furthermore,all the
`first stator electrodes 15' are connectedto a first stator termi-
`nal 20a and all the secondstator electrodes 15" are connected
`to a secondstator terminal 206, while the mobile electrodes
`16 are connected to ground. From the electrical standpoint,
`hence,the first inertial sensor 11 can be idealized by means of
`a first equivalent capacitor 18 and a second equivalent capaci-
`tor 19 (illustrated herein with a dashed line), having first
`terminals connectedto thefirst stator terminal 20a and to the
`
`inverting input 345 of the adder node 34 itself through the
`respective filter 35.
`In practice, the filters 35 extract the d.c. components ofthe
`acceleration signals Ay, Ay, Az and supplies at output a first
`static-acceleration signal A,., a second static-acceleration
`signal Ay. and a third static-acceleration signal A,., respec-
`tively. The subtractor nodes 34 subtractthe static-acceleration
`signals A,<, Ays, Azs from the corresponding acceleration
`signals Ay, Ay, Az. A first dynamic-acceleration signal A,,,,
`a second dynamic-acceleration signal A,, and a third
`dynamic-acceleration signal A,,,, which are correlated exclu-
`sively to the accelerations due to variable forces, are thus
`provided onthe outputsof the subtractor nodes 35 ofthefirst,
`second andthird detection lines 28, 29, 30, respectively.
`The threshold comparators 36 have inputs connected to the
`outputs of the respective subtractor nodes 34 and outputs
`connected to the logic gate 31, which in the embodiment
`described is an OR gate. Furthermore, the output of the logic
`gate 31 formsthe output 10a of the activation device 10 and
`suppliesthe activation pulses WU.In particular, an activation
`second stator terminal 20d, respectively, and second termi-
`pulse WU is generated when at least one of the dynamic-
`nals connected to ground. Furthermore, thefirst and second
`acceleration signals Ay», Ayp, Azp is higher than a pre-
`equivalent capacitors 18, 19 have a variable capacitance cor-
`determined threshold accelerationA,;, storedin the threshold
`related to the relative position of the moving element 13 with
`comparators 36; the activation pulses WU terminate when all
`respect to the rotor 12; in particular, the capacitances of the
`the dynamic-acceleration signals Ay,, Ayp, Azp return below
`equivalent capacitors 18, 19 at rest are equal and are unbal-
`the threshold acceleration A,,,. The threshold acceleration
`ancedin the presence of an acceleration oriented according to
`A,,, 18 moreover programmable and is preferably so selected
`the preferential detection axis (in this case,thefirst axis X).
`With reference to FIG. 3, the activation device 10 com-
`as to be exceeded in the presenceofthe stresses that the user
`prises, in addition to the first inertial sensor 20, a second
`impresses on the apparatus 1 during normaluse.
`65
`inertial sensor 21 andathird inertial sensor 22,identical to the
`In practice, the C-V converter 25 reads the capacitive
`first inertial sensor 20 and having preferential detection axes
`unbalancing values AC, ACy, AC; ofthe inertial sensors 20,
`parallel to the second axis Y and to the third axis Z, respec-
`21, 22, to which it is sequentially connected and converts the
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`sumption: consequently, the energy accumulated in the bat-
`teries is almost entirely available for active use of the appa-
`ratus 1,
`the effective autonomy whereof is significantly
`increased.
`Finally, it is clear that modifications and variations can be
`made to the device described herein, without thereby depart-
`ing from the scopeofthe present invention. In particular, the
`activation device 10 could comprise twoinertial sensors (for
`example, in the case ofa radio frequency mouse, which in use
`is displacedjust in one plane)or evenjustoneinertial sensor;
`inertial sensors of a different type could also be used, for
`example rotational inertial sensors or else inertial sensors
`with more than one degree of freedom (i.e., having at least
`two preferential non-parallel detection axes). Furthermore,
`there can be provided a C-V converter for each inertial sensor
`used; in this case, use of the multiplexer and demultiplexeris
`not required.
`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/orlisted in the Application Data Sheet,
`are incorporated herein by reference,in their entirety.
`From the foregoing it will be appreciated that, although
`specific embodiments of the invention have been described
`herein for purposesof illustration, various modifications may
`be made without deviating from the spirit and scope of the
`invention. Accordingly, the invention is not limited except as
`by the appended claims.
`The invention claimed is:
`1. A device for automatic detection ofstates of motion and
`
`5
`capacitive unbalancing values ACy, AC,, AC; into a voltage
`signal V_,, which is then sampled. Thefirst, second and third
`acceleration signals Ay, Ay, Az hence comprise respective
`sequences of sampled values of the voltage signal V_, gener-
`ated when the C-V converter 25 is connected respectively to
`the first, the second and the third inertial sensor 20, 21, 22;
`moreover, the first, second and third acceleration signal A,,
`Ay, Az indicate the sum ofall the accelerationsthat act respec-
`tively alongthefirst, second and third axes X, Y, Z.
`Thestatic-acceleration signals Ay, Ay<, Az, supplied by
`the filters 35, which basically correspondto the d.c. compo-
`nents of the acceleration signals A,, A,, Az, are correlated to
`the accelerations due to constant forces, such as for example
`the force of gravity. Note that, since the apparatus 1 can be
`variously oriented both during use and whenit is not in use,
`not necessarily are the components of the force of gravity
`along the axes X, Y, Z always constant and they may be
`non-zero even whenthe apparatus 1 is not moved. However,
`as long as the apparatus 1 remainsatrest, the force of gravity
`supplies constant contributionsto the acceleration signals Ay,
`Ay, Az. The static-acceleration signals Ay, Ay, Az, take into
`accountalso all the causes that can determine,in the inertial
`sensors 20, 21, 22, a permanent displacement of the moving
`element 13 from the position of rest with respect to the stator
`12 (FIG. 2). Amongst these causes, for example, there are
`fabrication offsets and deviations that can be caused by the
`fatiguing of the materials, especially in the springs 14. Sub-
`traction of the static-acceleration signals Ay, Ays, Az; from
`the acceleration signals Ay, Ay, Az advantageously enables
`compensation of said offsets.
`rest, comprising:
`The dynamic-acceleration signals Ay», Ayp, Azgp are
`
`exclusively correlated to the accelerations due to variable a first inertial sensor havingafirst preferential detection
`axis;
`forces and,in practice, are different from zero only when the
`apparatus 1 is moved, 1.e., when it is picked up to be used.
`a converter coupledto saidfirst inertial sensor and supply-
`35
`
`Consequently, at the precise moment whenthe user picks up ingafirst signal correlated to forces acting on saidfirst
`the apparatus 1, at least one of the dynamic-acceleration
`inertial sensor accordingto saidfirst preferential detec-
`tion axis;
`signals Ay», Ayp, Azp exceeds the threshold acceleration
`A,,, of the respective threshold comparator 36, and an activa-
`a first processing stage structured to processsaidfirst sig-
`tion pulse WU is supplied, which bringsthe control unit 3, the
`nal and supply a secondsignal correlated to a dynamic
`memory 4, the I/O unit 5 and the screen 6 back into the active
`componentofsaid first signal whereinsaidfirst process-
`state. Note that, in this case, also the force of gravity can
`ing stage comprises a filter, supplying a third signal
`advantageously provide a contribution to the dynamic-accel-
`correlated to a static componentof said first signal, and
`eration signals Ay, Ayn, Azp,as far as the apparatus 1 can be
`a subtractor element, for subtracting said third signal
`rotated by the user so as to changethe orientation of the axes
`from saidfirst signal; and
`X, Y, Z with respectto the vertical direction(i.e., with respect
`a first threshold comparator supplying a pulse when said
`to the direction of the force of gravity). Consequently, the
`second signal exceeds a threshold.
`movement due to the intervention of the user is more readily
`2. The device according to claim 1 wherein said first iner-
`detected.
`tial sensor is a micro-electro-mechanical sensor with capaci-
`Some advantages of the invention are evident from the
`tive unbalancing.
`foregoing description.In thefirst place, the activation device
`3. The device according to claim 1, further comprising a
`10 enables the apparatus 1 to be brought back automatically
`second inertial sensor having a second preferential detection
`into the active state from the stand-bystate, since it is based
`axis, the first and second inertial sensors being of a micro-
`just upon the forces that are transmitted by the user when he
`electro-mechanical type with capacitive unbalancing,thefirst
`picks up the apparatus 1 to use it. In practice, the activation
`preferential detection axis and the secondpreferential detec-
`device 10 is able to distinguish a condition of use from a
`tion axis being orthogonalto one another.
`condition of rest by simply detecting a state of motion from a
`4. The device according to claim 3 saidfirst inertial sensor
`state of substantial rest. Consequently, the apparatus 1 is
`and said secondinertial sensor are selectively connectable in
`reactivated as soon as it is picked up by the user and the
`sequence to said converter.
`transients of exit from the stand-by state are exhausted when
`5. The device according to claim 4, comprising a third
`the user is terminating the movementof picking up the appa-
`inertial sensor of a micro-electro-mechanical
`type with
`ratus 1. The troublesomedelays, that can reduce or eliminate
`capacitive unbalancing, having a third preferential detection
`the advantages deriving from the use of portable apparatus
`axis, orthogonalto saidfirst preferential detection axis and to
`with stand-alone supply,are thus prevented. Furthermore,the
`said second preferential detection axis.
`use of inertial sensors of the MEMS type, which are
`6. The device according to claim 5, further comprising a
`extremely sensitive, have small overall dimensions and can be
`switch device positioned to selectively connectsaid first iner-
`tial sensor, said second inertial sensor and said third inertial
`made at relatively low costs,
`is advantageous. Above all,
`however, the MEMSsensorshave a virtually negligible con-
`sensor in sequenceto said converter.
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`7. The device according to claim 1, further comprising a
`second inertial sensor having a secondpreferential detection
`axis that is transverseto thefirst preferential detection axis.
`8. The device according to claim 7, further comprising:
`a multiplexer connected betweenthe inertial sensors and
`the converter to selectively electrically connect each of
`the inertial sensors to the converter, the converter sup-
`plying a third signal correlated to forces acting on said
`second inertial sensor according to said second prefer-
`ential detection axis;
`a second processing stage structured to process said third
`signal and supply a fourth signal correlated to a dynamic
`componentofsaid third signal;
`asecondthreshold comparator supplying a pulse whensaid
`fourth signal exceeds the threshold; and
`a demultiplexer connected between the converter and the
`first and second processing stages to selectively supply
`the first and third signals to the first and second process-
`ing stages, respectively.
`9. The device according to claim 8, further comprising:
`a phase generator connected to the multiplexer, converter,
`and demultiplexer and structured to provide timing sig-
`nals that coordinate operations of the multiplexer, con-
`verter, and demultiplexer.
`10. A portable electronic apparatus, comprising:
`a supply source;
`a plurality of user devices alternatively connected to said
`supply source in a first operative state, and disconnected
`from said supply source in a second operativestate;
`deactivation means connected to said user devices for set-
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`16. The apparatus according to claim 10, wherein said
`activation meansfurther include a secondinertial sensor hav-
`
`ing a second preferential detection axis that is transverse to
`the first preferential detection axis.
`17. The apparatus according to claim 16, wherein said
`activation means further include:
`a multiplexer connected between the inertial sensors and
`the converter to selectively electrically connect each of
`the inertial sensors to the converter, the converter sup-
`plying a third signal correlated to forces acting on said
`second inertial sensor according to said secondprefer-
`ential detection axis;
`a second processing stage structured to process said third
`signal and supply a fourth signal correlated to a dynamic
`componentof said third signal;
`a second threshold comparator supplying a pulse when said
`fourth signal exceeds the threshold; and
`a demultiplexer connected between the converter and the
`first and second processing stages to selectively supply
`the first and third signals to the first and second process-
`ing stages, respectively.
`18. The apparatus according to claim 10, wherein said
`activation means further include:
`
`a phase generator connected to the multiplexer, converter,
`and demultiplexer and structured to provide timing sig-
`nals that coordinate operations of the multiplexer, con-
`verter, and demultiplexer.
`19. A method for automatic detection of motion of a por-
`table electronic device, comprising:
`sensing motion of the device along a first preferential
`detection axis;
`supplying a first signal correlated to forces acting on the
`device according to the preferential detection axis;
`processing the first signal and supplying a second signal
`correlated to a dynamic componentofthe first signal
`wherein the processing comprisesfiltering the first sig-
`nal to create a third signal correlated to a static compo-
`nent of the first signal, and subtracting the third signal
`from thefirst signal to create the second signal; and
`supplying an activation pulse when the second signal
`exceedsa first threshold.
`
`supplying the activation pulse when the fourth signal
`exceeds a secondthreshold.
`
`ting said user devicesin said second operative state; and
`activation means for setting the user devices in thefirst
`operative state, said activation means including:
`a first inertial sensor having a preferential detection axis,
`a converter coupledto saidfirst inertial sensor and supply-
`ing a first signal correlated to forces acting on saidfirst
`inertial sensor according to said preferential detection
`axis;
`a first processing stage structured to processsaid first sig-
`nal and supply a second signal correlated to a dynamic
`componentofsaid first signal, and
`a first threshold comparator supplying an activation pulse
`20. The method of claim 19, further comprising
`whensaid second signal exceeds a threshold.
`sensing motion of the device along a secondpreferential
`11. An apparatus according to claim 10 wherein, in the
`detection axis that is orthogonalto the first preferential
`presence of the activation pulse, said user devices are in said
`detection axis;
`first operative state.
`supplying a third signal correlated to forces acting on the
`12. The apparatus according to claim 10 wherein saidfirst
`device according to the second preferential detection
`processing stage comprisesafilter, supplying a third signal
`axis;
`correlated to a static componentofsaid first signal, and a
`processing the third signal and supplying a fourth signal
`subtractor element,for subtracting said third signal from said
`correlated to a dynamic componentof the third signal;
`first signal.
`and
`13. The apparatus according to claim 10 wherein saidfirst
`inertial sensor is a micro-electro-mechanical sensor with
`capacitive unbalancing.
`14. The apparatus according to claim 10, wherein said
`activation meansfurther include a secondinertial sensor hav-
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`21. The method of claim 19, further comprising:
`receiving the activation pulse at an operation circuit of the
`device, the operation circuit being in a stand-by condi-
`ing a second preferential detection axis, the first and second
`tion prior to receiving the activation pulse; and
`inertial sensors being of a micro-electro-mechanical type
`activating the operation circuit into an active condition in
`with capacitive unbalancing, the first preferential detection
`responseto receiving the activation pulse.
`axis and the secondpreferential detection axis being orthogo-
`nal to one another.
`22. A device, comprising:
`a first inertial sensor havingafirst preferential detection
`15. The apparatus according to claim 14, wherein said
`activation means further include a third inertial sensor of a
`axis;
`a converter coupledto thefirst inertial sensor and supply-
`ing a first signal correlated to forces acting on the first
`inertial sensor according to the first preferential detec-
`tion axis;
`
`micro-electro-mechanical type with capacitive unbalancing,
`having a third preferential detection axis, orthogonalto said
`first preferential detection axis andto said secondpreferential
`detection axis.
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`US 7,409,291 B2
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`sensing motion of the device along a secondpreferential
`detection axis that is orthogonalto the first preferential
`detection axis;
`supplying a third signal correlated to forces acting on the
`device according to the second preferential detection
`axis;
`processing the third signal and supplying a fourth signal
`correlated to a dynamic componentof the third signal;
`and
`
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`a first processing stage structuredto process thefirst signal
`and supply a secondsignal correlated to a dynamic com-
`ponentofthefirst signal;
`a first thres