US008093767B2
`
`a2) United States Patent
`US 8,093,767 B2
`(0) Patent No.:
`Pepinetal.
`Jan. 10, 2012
`(45) Date of Patent:
`
`(54) LINEAR-RESONANT VIBRATION MODULE
`
`(76)
`
`Inventors: Brian Mare Pepin, Oakland, CA (US);
`Robin Elenga, Seattle, WA (US)
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`US.C. 154(b) by 0 days.
`
`(21) Appl. No.: 12/782,697
`
`(22)
`
`Filed:
`
`May18, 2010
`
`(65)
`
`Prior Publication Data
`
`US 2010/0289346 Al
`
`Nov. 18, 2010
`
`Related U.S. Application Data
`
`(60) Provisional application No. 61/179,109,filed on May
`18, 2009.
`
`(51)
`
`Int. Cl.
`(2006.01)
`02K 33/00
`(2006.01)
`H02K 41/02
`(2006.01)
`02K 41/00
`(2006.01)
`HO2K 7/00
`(52) US.CL woo... 310/15; 310/12.15; 310/13; 310/14;
`310/19
`
`(58) Field of Classification Search .............. 310/13-15,
`310/19, 12.15
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`
`5,955,799 A *
`9/1999 Amayaetal. ee 310/36
`6,323,568 BL* 11/2001 Zabar wee 310/17
`6,326,706 BL* 12/2001 Zhang oe 310/12.31
`
`6,809,427 B2* 10/2004 Cheungetal. 0.0.0... 290/1R
`2005/0231045 Al* 10/2005 Obaetal. oo. 310/19
`
`.. 340/407.1
`2005/0275508 Al* 12/2005 Orretal.
`.....
`
`6/2006 Kimetal. wu. 310/15
`2006/0138875 Al*
`2006/0208600 Al*
`9/2006 Sahyoun «0.0... 310/254
`2008/0174187 Al*
`7/2008 Erixonetal. wc... 310/15
`
`JP
`JP
`WO
`
`FOREIGN PATENT DOCUMENTS
`10164809 A
`6/1998
`11018395 A
`1/1999
`9819383 Al
`5/1998
`
`* cited by examiner
`
`Primary Examiner — Quyen Leung
`
`Assistant Examiner — Jose Gonzalez Quinones
`(74) Attorney, Agent, or Firm —Olympic Patent Works
`PLLC.
`
`(57)
`
`ABSTRACT
`
`Various embodiments of the present invention compriselin-
`ear-resonant vibration modules that can be incorporated in a
`wide variety of appliances, devices, and systems to provide
`vibrational forces. The vibrational forces are produced by
`linear oscillation of a weight or member, in turn produced by
`rapidly alternating the polarity of one or more driving elec-
`tromagnets. Feedback control is used to maintain the vibra-
`tional frequency of linear-resonant vibration module at or
`near the resonant frequency for the linear-resonant vibration
`module. Linear-resonant vibration modules can be designed
`to produce vibrational amplitude/frequency combinations
`throughouta large region of amplitude/frequency space.
`
`5 Claims, 15 Drawing Sheets
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`U.S. Patent
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`Jan. 10, 2012
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`Sheet 9 of 15
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`U.S. Patent
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`Jan. 10, 2012
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`Sheet 10 of 15
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`Jan. 10, 2012
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`Sheet 11 of 15
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`Jan. 10, 2012
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`Sheet 12 of 15
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`U.S. Patent
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`Jan. 10, 2012
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`Sheet 13 of 15
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`Jan. 10, 2012
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`Sheet 14 of 15
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`U.S. Patent
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`Jan. 10, 2012
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`Sheet 15 of 15
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`US 8,093,767 B2
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`

`US 8,093,767 B2
`
`1
`LINEAR-RESONANT VIBRATION MODULE
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`This application claims the benefit of Provisional Patent
`Application No. 61/179,109, filed May 18, 2009.
`
`
`
`TECHNICAL FIELD
`
`The present invention is related to vibration-generating
`devices and, in particular, to vibration modules that can be
`incorporated into a wide variety of different types of electro-
`mechanical devices and systems to produce vibrations of
`selected amplitudes and frequencies over a wide range ampli-
`tude/frequency space.
`
`BACKGROUND
`
`Vibration-inducing motors and mechanisms have been
`used for many years in a wide variety of different consumer
`appliances, toys, and other devices and systems. Examples
`include vibration signals generated by pagers, vibration-
`driven appliances, such as hair-trimming appliances, electric
`toothbrushes, electric toy football games, and many other
`appliances, devices, and systems. The most commonelectro-
`mechanical system used for generating vibrations is an inten-
`tionally unbalancedelectric motor.
`FIGS. 1A-B illustrate an unbalanced electric motor typi-
`cally used liar generating vibrations in a wide variety of
`different devices. As shown in FIG. 1A, a small, relatively
`low-powerelectric motor 102 rotates a cylindrical shaft 104
`onto which a weight 106 is asymmetrically or mounted. FIG.
`1B shows the weight asymmetrically mounted to the shaft,
`looking downat the weight and shaft in the direction of the
`axis of the shall. As shown in FIG. 1B, the weight 106 is
`mounted off-center on the electric-motor shaft 104. FIGS.
`2A-13 illustrate the vibrational motion produced by the
`unbalancedelectric motor shown in FIGS. 1A-B. As shown in
`FIGS. 2A-B, the asymmetrically-mounted weight creates an
`elliptical oscillation ofthe end ofthe shall, normalto the shaft
`axis, when the shall is rotated at relatively high speed by the
`electric motor. FIG. 2A showsdisplacementofthe weight and
`shall from the stationary shall axis as the shall is rotated,
`looking downonthe weight andshaft along the shall axis, as
`in FIG. 1B. In FIG. 2A, a small mark 202 is provided at the
`periphery ofthe disk-shaped endthe of electric-motorshall to
`illustrate rotation of the shaft. When the shalt rotates at high
`speed, a point 204 on the edge ofthe weighttracesan ellipsoid
`206 and the center of the shaft 208 traces a narrower and
`
`smaller ellipsoid 210. Were the shaft balanced, the center of
`the shaft would remain at a position 212 in the center of the
`diagram during rotation, but the presence of the asymmetri-
`cally-mounted weight attached to the shaft, as well as other
`geometric and weight-distribution characteristics of the elec-
`tric motor, shall, and unbalanced weight together create
`forces that move the end of the shaft along the elliptical path
`210 when the shaft is rotated at relatively high speed. The
`movement can be characterized, as shown in FIG. 2B, by a
`major axis 220 and minor axis 222 of vibration, with the
`direction of the major axis of vibration equalto the direction
`of the majoraxis of the ellipsoids, shown in FIG. 2A,and the
`length of the major axis corresponding to the amplitude of
`vibration in this direction. In many applications, in which a
`linear oscillation is desired, designers seek to force the major-
`axis-amplitude/minor-axis-amplitude ratio to be as large as
`possible, but, because the vibration is produced bya rota-
`
`10
`
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`
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`tional force, it is generally not possible to achieve linear
`oscillation. In manycases, time path traced by the shall center
`may beclose to circular. The frequency of vibration of the
`unbalancedelectric motoris equalto the rotational frequency
`ofthe electric-motorshaft, andis therefore constrained by the
`rate at which the motor canrotate the shaft. At low rotational
`
`
`
`speeds, little vibration is produced.
`While effective in producing vibrations, there are many
`problems associated with the unbalanced-electric-motor
`vibration-generating units, such as that shown in FIG. 1A,
`commonly usedin the various devices, systems, and applica-
`tions discussed above. First, unbalancing the shaft of an elec-
`tric motor not only produces useful vibrations that can be
`harnessed for various applications, but also produces destruc-
`tive, unbalanced forces within the motor that contribute to
`rapid deterioration of motor parts. Enormouscare and effort
`is undertaken to precisely balance rotating parts of motors,
`vehicles, and other types ofmachinery, and the consequences
`of unbalancedrotating parts are well knownto anyone famil-
`iar with automobiles, machine tools, and other such devices
`and systems. The usefullifetimes of many devices and appli-
`ances, particularly hand-held devices and appliances, that
`employ unbalancedelectric motors for generating vibrations
`may range from a few tens of hours to a few thousands of
`hoursof use, after which the vibrational amplitude produced
`by the devices declines precipitously asthe electric motor and
`other parts deteriorate.
`A second problem with unbalancedelectric motors is that
`they are relatively inefficientat producing vibrational motion.
`A far greater amount of poweris consumed by an unbalanced
`electrical motor to produce a given vibrational force than the
`theoretical minimum power required to produce the given
`vibrational three. As a result, many hand-held devices that
`employ unbalancedelectric motors the generating vibrations
`quickly consumebatteries during use.
`A third problem with unbalanced electric motors, dis-
`cussed above,is that they generally produce elliptical vibra-
`tional modes. Although such modes maybe usefulin particu-
`lar applications, many applications can better use a linear
`oscillation, with greater directional concentration of vibra-
`tional forces. Linear oscillation cannot generally be produced
`by unbalancedelectric motors.
`A fourth, and perhaps most fundamental, problem associ-
`ated with using unbalancedelectric motors to generate vibra-
`tions is that only a very limited portion ofthe total vibrational-
`force/frequency space is accessible to unbalanced electric
`motors. FIG. 3 showsa graph ofvibrational three with respect
`to frequency for various types of unbalancedelectric motors.
`The graph is shown as a continuous hypothetical curve,
`although, of course, actual data would be discrete. As shown
`in FIG. 3, for relatively low-power electric motors used in
`hand-held appliances, only a fairly narrow range of frequen-
`cies centered about 80 Hz (302 in FIG.3) generate a signifi-
`cant vibrational force. Moreover, the vibrational force is rela-
`tively modest. The bulk of energy consumed by an
`unbalancedelectric motor is used to spin the shaft and unbal-
`anced weight and to overcomefrictional and inertial threes
`within the motor. Only a relatively small portion of the con-
`sumed energy is translated into desired vibrational forces.
`Because of the above-discussed disadvantages with the
`commonly employed unbalanced-electric-motor vibration-
`generation units, designers, manufacturers, and, ultimately,
`users of a wide variety of different vibration-based devices,
`appliances, and systems continue to seek moreefficient and
`
`17
`
`17
`
`

`

`US 8,093,767 B2
`
`3
`capable vibration-generating units for incorporation into
`many consumerappliances, devices, and systems.
`
`SUMMARY
`
`Various embodiments of the present invention comprise
`linear-resonantvibration modules that can be incorporated in
`a widevariety of appliances, devices, and systems to provide
`vibrational forces. The vibrational forces are produced by
`linear oscillation of a weight or member, in turn produced by
`rapidly alternating the polarity of one or more driving elec-
`tromagnets. Feedback control is used to maintain the vibra-
`tional frequency of linear-resonant vibration module at or
`near the resonant frequency for the linear-resonantvibration
`module. Linear-resonant vibration modules can be designed
`to produce vibrational amplitude/frequency combinations
`throughouta large region of amplitude/frequency space.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIGS. 1A-B illustrate an unbalanced electric motor typi-
`cally used for generating vibrations in a wide variety of dif-
`ferent devices.
`FIGS. 2A-B illustrate the vibrational motion produced by
`the unbalanced electric motor shown in FIGS. 1A-B.
`FIG. 3 showsa graph of vibrational force with respect to
`frequency for various types of unbalancedelectric motors.
`FIGS. 4A-Gillustrate one particular LRVM,and operation
`of the particular LRVM,that represents one embodiment of
`the present invention.
`FIGS. 5A-Billustrate an H-bridge switch that can be used,
`in various embodiments of the present invention, to change
`the direction of current applied to the coil that drives linear
`oscillation within a
`linear-resonance vibration module
`
`(“LRVM”).
`FIG.6 provides a block diagram of the LRVM,illustrated
`in FIGS. 4A-G,
`that represents one embodiment of the
`present invention.
`FIGS. 7A-C provide control-flow diagramsthat illustrate
`the control program, executed by the CPU, that controls
`operation of an LRVM that represents one embodimentofthe
`present invention.
`FIG. 8 represents the range of frequencies and vibrational
`forces that can achieved by different implementations of
`LRVMand LRVMcontrol programsthat represent embodi-
`ments of the present invention.
`FIG. 9 showsa plot of the amplitude/frequency space and
`regions in that space that can be operationally achieved by
`unbalanced electrical motors and by LRVMsthat represent
`embodiments of the present invention.
`FIGS. 10-17 show a variety of different alternative imple-
`mentations of LRVMsthat represent different embodiments
`of the present invention.
`FIG. 18 illustrates an enhancementof the embodiment of
`
`the present invention shown in FIG.16.
`
`DETAILED DESCRIPTION
`
`Embodiments of the present invention include various
`types of linear-resonant vibration modules (“LRVMs’’) that
`can be used within a wide variety of different types of appli-
`ances, devices, and systems, to generate vibrational forces.
`The LRVMsthat represent embodimentsofthe present inven-
`tion are linear in the sense that the vibrational forces are
`
`produced bya linear oscillation of a weight or component
`within the LRVM,rather than as a by-product of an unbal-
`anced rotation, as in the case of currently employed unbal-
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`anced electric motors. The linear nature of the LRVM vibra-
`tion-inducing motion allows the problems associated with
`unbalanced-electric-motor vibrators, discussed above, to be
`effectively addressed. An oscillating linear motion does not
`produce destructive forces that quickly degrade and wear out
`an unbalanced electric motor. A linearly oscillating mecha-
`nism is characterized by parameters that can be straightfor-
`wardly varied in order to produce vibrations of a desired
`amplitude and frequency over a very broad region of ampli-
`tude/frequency space. Combininga linearly oscillating vibra-
`tion-inducing mechanism with feedback control, so that the
`frequencyof vibration falls close to the resonant frequency of
`the LRVM,results in optimal power consumption with
`respect to the amplitude and frequencyofvibration produced
`by the LRVM.Clearly, linear oscillation within a LRVM
`translates into highly direction vibrational forces produced by
`an appliance or device that incorporates the LRVM.
`FIGS. 4A-Gillustrate one particular LRVM,and operation
`of the particular LRVM,that represents one embodiment of
`the present invention. FIGS. 4A-Gall use the sameillustra-
`tion conventions, next discussed with reference to FIG. 4A.
`The LRVMincludes a cylindrical housing 402 within which
`a solid, cylindrical mass 404, or weight, can movelinearly
`along the inner, hollow, cylindrically shaped chamber 406
`within the cylindrical housing or tube 402. The weightis a
`magnet, in the described embodimentof the present inven-
`tion, with polarity indicated by the “+” sign 410 on the right-
`hand end and the “-” sign 412 on the left-hand end of the
`weight 404. The cylindrical chamber 406 is capped by two
`magnetic disks 414 and 416 with polarities indicated by the
`“+ sion 418 and the “—” sign 419. The disk-like magnets 414
`and 418 are magnetically oriented opposite from the mag-
`netic orientation of the weight 404, so that when the weight
`movesto either the extremeleft or extreme right sides of the
`cylindrical chamber, the weight is repelled by one of the
`disk-like magnets at the left or right ends of the cylindrical
`chamber. In other words, the disk-like magnets act muchlike
`springs, to facilitate deceleration and reversal of direction of
`motion ofthe weight and to minimize or prevent mechanical-
`impact forces ofthe weight and the end caps that close offthe
`cylindrical chamber. Finally, a coil of conductive wire 420
`girdles the cylindrical housing, or tube 402 at approximately
`the mid-point of the cylindrical housing.
`FIGS. 4B-G illustrate operation of the LRVM shown in
`FIG. 4A. Whenan electric current is applied to the coil 420 in
`a first direction 422, a corresponding magnetic force 424 is
`generated in a direction parallel to the axis of the cylindrical
`chamber, which accelerates the weight 404in the direction of
`the magnetic force 424. Whenthe weightreaches a pointat or
`close to the corresponding disk-like magnet 414, as shown in
`FIG. 4C, a magnetic force dueto the repulsion ofthe disk-like
`magnet 414 and the weight 404, 426,
`is generated in the
`opposite direction, decelerating the weight and reversingits
`direction. As the weight reverses direction, as shown in FIG.
`4D, current is applied in an opposite direction 430 to the coil
`420, producing a magnetic force 432 in an opposite direction
`from the direction of the magnetic. force shown in FIG. 4B,
`which accelerates the weight 404 in a direction opposite to the
`direction in which the weight is accelerated in FIG. 4B. As
`shownin FIG. 4F,the weight then movesrightward until, as
`shownin FIG.4F, the weightis decelerated, stopped, and then
`accelerated in the opposite direction by repulsionofthe disk-
`like magnet 416. An electrical current is then applied to the
`coil 420 in the same direction 434 as in FIG. 4B, again
`accelerating the solid cylindrical mass in the samedirection
`as in FIG. 4B. Thus, by acombination ofa magneticfield with
`rapidly reversing polarity, generated by alternating the direc-
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`US 8,093,767 B2
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`5
`tion of current applied to the coil, and by the repulsive forces
`between the weight magnet andthe disk-like magnets at each
`end of the hollow, cylindrical chamber, the weight linearly
`oscillates back and forth within the cylindrical housing 402,
`imparting a direction force at the ends of the cylindrical
`chamber with each reversal in direction.
`Clearly, the amplitude of the vibration and vibrational
`forces producedare related to the length of the hollow cham-
`ber in which the weight oscillates, the current applied to the
`coil, the mass of the weight, the acceleration of the weight
`producedby the coil, and the massofthe entire LRVM.All of
`these parameters are essentially design parameters for the
`LRVM,and thus the LRVM can be designed to produce a
`wide variety of different amplitudes.
`The frequency of the oscillation of the solid, cylindrical
`massis determined by the frequency at which the direction of
`the current applied to the coil is changed. FIGS. 5A-Billus-
`trate an H-bridge switch that can be used, in various embodi-
`ments of the present invention, to change the direction of
`current appliedto the coil that drives linear oscillation within
`an LRVM.FIGS. 5A-B both use the sameillustration con-
`
`to FIG. 5A. The
`ventions, described next with respect
`H-bridge switch receives, as input, a directional signal d 502
`and direct-current (“DC”) power 504. The direction-control
`signal d 502 controls four switches 506-509, shownas tran-
`sistors in FIG. 5A. When the input control signal d 502 is
`high, or “1,” as shown in FIG. 5A, switches 508 and 509 are
`closed and switches 506 and 507 are open, and therefore
`current flows, as indicated by curved arrows, such as curved
`arrow 510, from the power-source input 504 to ground 512 in
`a leftward direction through the coil 514. When the input-
`control signal d is low, or “0,” as shown in FIG. 5B, the
`direction of the current through the coil is reversed. The
`H-bridge switch, shown in FIGS. 5A-B, is but one example of
`various different types of electrical and electromechanical
`switches that can be used to rapidly alternate the direction of
`current within the coil of an LRVM.
`FIG.6 provides a block diagram of the LRVM,illustrated
`in FIGS. 4A-G,
`that represents one embodiment of the
`present invention. The LRVM,in addition to the cylindrical
`housing, coil, and internal components shown in FIG, 4A,
`includes a powersupply, a user interface, generally compris-
`ing electromechanical buttons or switches,
`the H-bridge
`switch, discussed above with reference to FIGS. 5A-B, a
`central processing unit (“CPU”), generally a small, low-pow-
`ered microprocessor, and one or more electromechanical sen-
`sors. All of these components are packaged together as an
`LRVMwithin a vibration-based appliance, device, or system.
`As shown in FIG. 6, the LRVM 600 is controlled by a
`control program executed by the CPU microprocessor 602.
`The microprocessor may contain sufficient on-board memory
`to store the control program and other values needed during
`execution of the control program, or, alternatively, may be
`coupled to a low-powered memory chip 604orflash memory
`for storing the control program. The CPU receives inputs
`front the user controls 606 that together comprise a user
`interface. These controls may include any of various dials,
`pushbuttons, switches, or other electromechanical-control
`devices. As one example,the user controls may include a dial
`to select a strength of vibration, which corresponds to the
`current applied to the coil, a switch to select one of various
`different operational modes, and a power button. The user
`controls generate signals input to the CPU 608-610. A power
`supply 612 provides power, as needed,to user controls 614, to
`the CPU 616 and optional, associated memory,
`to the
`H-bridge switch 618, and, when needed, to one or more
`sensors 632. The voltage and current supplied by the power
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`supply to the various components mayvary, depending on the
`operational characteristics and requirements of the compo-
`nents. The H-bridge switch 620 receives a control-signal
`input d 622 from the CPU. The power supply 612 receives a
`control input 624 from the CPUto control the current sup-
`plied to the H-bridge switch 618 for transfer to the coil 626.
`The CPU receives input 630 from one or more electrome-
`chanical sensors 632 that generate a signal corresponding to
`the strength of vibration currently being produced by the
`linearly oscillating mass 634. Sensors may include one or
`more ofaccelerometers, piezoelectric devices, pressure-sens-
`ing devices, or other types of sensors that can generate signals
`corresponding to the strength of desired vibrational forces.
`FIGS. 7A-C provide control-flow diagramsthatillustrate
`the control program, executed by the CPU, that controls
`operation of an LRVM that represents one embodimentofthe
`present invention. FIG. 7A provides a control-Bow diagram
`for the high-level control program. The program begins
`execution, in step 702, upon a power-on event invoked by a
`user through a powerbutton or other user control. In step 702,
`variouslocal variables are set to default values, including the
`variables: (1) mode, which indicates the current operational
`mode of the device; (2) strength, a numerical value corre-
`sponding to the current user-selected strength of operation,
`correspondingto the electrical current applied to the coil; (3)
`Ivl0, a previously sensed vibrational strength; (4) Ivl1, a cur-
`rently sensed vibrational strength; (5) freq, the current fre-
`quency at which the direction of current is alternated in the
`coil; (6) d, the control output to the H-bridge switch; and (7)
`inc, a Boolean value that indicates that the frequencyis cur-
`rently being increased. Next, in step 704, the control program
`waits for a next event. The remaining steps represent a con-
`tinuously executing loop, or event handler, in which each
`event that occurs is appropriately handled by the control
`program.In certain implementations of the control program,
`events may be initiated by interrupt-like mechanisms and
`stacked for execution while, in more primitive implementa-
`tions, certain events that overlap in time may be ignored or
`dropped. In the implementation illustrated in FIGS. 7A-C,
`two timers are used, one for controlling the change in direc-
`tion ofthe current appliedto the coil, ata currently established
`frequency, and the other for controlling a monitoring interval
`at which the control program monitors the vibrational force
`currently produced. Rather than using a formal timer mecha-
`nism, certain implementations may simply employ counted
`loops or other simple programming techniques for periadi-
`cally carrying out tasks. When an event occurs, the control
`program begins a series of tasks, the first of which is repre-
`sented by the conditional step 706, to determine what event
`has occurred and appropriately handle that event. When the
`frequency timer has expired, as determined in step 706, the
`value of the output signald is flipped, in step 708, and output
`to the H-bridge switch, with the frequencytimer beingreset to
`trigger a next frequency-related event. The frequency-timer
`interval is determinedbythe current value ofthe variable freq.
`Otherwise, when the event is a monitor timer expiration
`event, as determined in step 710, then a routine “monitor”is
`called in step 712. Otherwise, when the event corresponds to
`a change in the user input through the user interface, as
`determinedin step 714, the routine “control”is called in step
`716. Otherwise, when the event is a power-down event, as
`determined in step 718, resulting from deactivation of a
`powerbutton bythe user, then the control program appropri-
`ately powers down the device, in step 720, and the control
`program terminates in step 722. Any other of various types of
`events that may occur are handledby a default event handler
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`US 8,093,767 B2
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`7
`724. These events may include various error conditions that
`arise during operation of the device.
`FIG. 7B provides a control-flow diagram for the routine
`“monitor,” called in step 712 of FIG. 7A. In step 730, the
`routine “monitor” converts the sensor input to an integer
`representing the current vibrational force produced by the
`LRVMandstores the integer value in the variable Ivl1. Next,
`in step 732, the routine “monitor” determines whetheror not
`the LRVM is currently operating in the default mode.In the
`default mode, the LRVM uses continuous feedback control to
`optimize the vibrational force produced by the LRVM by
`continuously seeking to operate the LRVMat a frequency as
`close as possible to the resonant frequency for the LRVM.
`Other, more complex operational modes maybe handled by
`various more complex routines, represented by step 734 in
`FIG. 7B. More complex vibrational modes may systemati-
`cally and/or periodically alter the frequency or producevari-
`ous complex, multi-componentvibrational modes useful in
`certain applications, appliances, devices, and systems. These
`more complex modesare application dependent, and are not
`further described in the control-flow diagrams. In the case
`that the operational mode is the default mode, in which the
`control program seeks to optimize the vibrational force gen-
`erated by the device, in step 736, the routine “monitor”deter-
`mines whetherthelocal variable inc is set to TRUE. Ifso, then
`the control program is currently increasing the frequency at
`which the device operates in order to obtain the resonance
`frequency. When lv11 is greater than Ivl0, as determined in
`step 738,
`then the vibrational
`force has been recently
`increased by increasing the frequency, and so the routine
`“monitor” increases the frequency again, in step 740, and
`correspondingly resets the frequency timer. Otherwise, when
`Ivl1 is less than Ivl0, as determined in step 742, then the
`control program has increased the frequency past the reso-
`nance frequency, and therefore, in step 744, the control pro-
`gram decreasesthe frequency,sets the variable inc to FALSE,
`and correspondingly resets the frequency timer. In similar
`fashion, when the variable inc is initially FALSE, as deter-
`mined in step 736, and when lvl1 is greater than lvl0, as
`determined in step 746, the routine “monitor” decreases the
`value stored in the variable freq, in step 748 andresets the
`frequency timer. Otherwise, when lvl] is less than Iv10, as
`determinedin step 750, then the routine “monitor”increases
`the value stored in the variable freq, sets the variable the to
`TRUE,andresets the frequency timerin step 752. Finally, the
`value in Ivl1 is transferred to Ivl0 and the monitor timeris
`reset, in step 754.
`FIG. 7C provides a control-flow diagram for the routine
`“control,” called in step 716 in FIG. 7A. This routine is
`invoked when a changein the user controls has occurred. In
`step 760, the variables mode andstrength are set to the cur-
`rently selected mode andvibrationalstrength, represented by
`the current states of control features in the user interface.
`Next, in step 762, the routine “control” com