Note: Descriptions are shown in the official language in which they were submitted.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-1-
AUDIO DEVICES HAVING ELECTROACTIVE POLYMER ACTUATORS
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit, under 35 USC 119(e), of
United States provisional patent application numbers: 61/497,556, filed
June 16, 2011, entitled "ELECTRO-MECHANICAL SYSTEM FOR
SIMULATING LOW FREQUENCY AUDIO SENSATIONS"; and
61/564,437, filed November 29, 2011, entitled "ACOUSTIC NOISE
REDUCTION TECHNIQUES FOR TACTILE HEADPHONE
ACTUATORS"; the entire disclosure of each of which is hereby
incorporated by reference.
FIELD OF THE INVENTION
In various embodiments, the present disclosure relates generally to
electro-mechanical systems for simulating low frequency audio sensations.
More particularly, the present disclosure relates to audio devices equipped
with electroactive polymer actuators or transducers. In particular, the
present disclosures relates to headphones equipped with electroactive
polymer actuators and mechanical and electrical acoustic noise reduction
modules.
BACKGROUND OF THE INVENTION
Conventional acoustic headphones include a pair of ear cups
intercoupled by a headband. The ear cups include loudspeakers mounted
within a housing portion of the ear cups and held in place close to a user's
ears. The headphones include electrical wires to connect the
loudspeakers to an audio signal source such as an audio amplifier, radio,
CD player, portable media player, computer, tablet, mobile device, or
gaming console. Some versions of conventional headphones also include
electronic circuits for signal conditioning and processing the acoustic
signal received from the audio signal source. Versions of audio
headphones that do not include a headband and are specifically designed
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
to be placed directly in the user's ear are also known as earphones or
colloquially as earbuds.
Conventional audio signals include acoustical frequency
components in the range of about 20 Hz to about 20 kHz. Most acoustic
reproduction systems (home audio, headphones, earbuds, telephones,
speakers) cannot cover the entire audio frequency range effectively and
typically perform poorly at low frequencies (below about 200 Hz).
Accordingly, large acoustical radiators are employed to accurately
reproduce low frequency audio signals. Typically, these devices are
physically large and consume a significant amount of power. One
example of an acoustical radiator is a subwoofer cabinet used in home
theater systems. It is difficult to implement low frequency audio content
into relatively small acoustic reproduction devices such as headphones.
Some methods of doing so require essentially sealing the air volume
around the listener's ear and using directly coupled air pressure waves.
This method is effective but also poses uncomfortable pressures even at
modest sound levels. At higher sound levels it can even become
dangerous and cause short or long term hearing loss.
Bone conduction is the conduction of sound to the inner ear through
the bones of the skull (http://en.wikipedia.org/wiki/Bone_conduction).
Bone conduction is why a person's voice sounds different to him/her when
it is recorded and played back. Because the skull conducts lower
frequencies better than air, people perceive their own voices to be lower
and deeper than others do. Bone conduction also explains why a
recording of one's own voice sounds higher than one is accustomed to.
Bone conduction is said to have been discovered by the composer Ludwig
van Beethoven, who was almost deaf. Beethoven supposedly found a
way to hear music through his jawbone by biting a rod attached to his
piano.
Some hearing aids employ bone conduction, achieving an effect
equivalent to hearing directly by means of the ears. A headset is
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-3-
ergonomically positioned on the temple and cheek and an
electromechanical transducer, which converts electric signals into
mechanical vibrations, sends sound to the internal ear through the cranial
bones. Likewise, a microphone can be used to record spoken sounds via
bone conduction. The first description of a bone conduction hearing aid
was provided in U.S. Pat. No. 1,521,287.
Bone conduction devices may be categorized into three types:
hands-free headsets or headphones; hearing aids and assistive listening
devices; and specialized communication devices (e.g. underwater & high-
noise environments). Bone conduction devices have several advantages
over traditional headphones: such devices are "ears-free:, thus providing
extended use comfort and safety; have high sound clarity in very noisy
environments; may be used with hearing protection; and may provide the
perception of stereo sound.
Among the devices' disadvantages: some implementations require
more power than headphones; and some devices may provide less clear
recording & playback than traditional headphones and microphone
because of reduced frequency bandwidth.
An example of a bone conduction speaker is a rubber over-molded
piezo-electric flexing disc about 40mm across and 6mm thick which is
used by scuba divers. A connecting cable is molded into the disc,
resulting in a tough, water-proof assembly. In use, the speaker is strapped
against one of the dome-shaped bone protrusions behind the ear. As
would be expected, the sound produced seems to come from inside the
user's head, but can be surprisingly clear and crisp.
Bone conduction audio devices are not limited to headsets or
headphones but can also be used on other parts of the body wherever the
device can be coupled to the skeletal system.
The present disclosure provides improved audio devices such as
headphones with electro-mechanical systems such as electroactive
polymer actuators for simulating low frequency audio sensations, The
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-4-
improved audio devices comprise mechanical and electrical acoustic noise
reduction modules.
Another application that may be addressed by the present invention
lies in sensory enhanced audio devices where information other than
audio signals is conveyed to the user. An early example of a sensory
enhanced headphone to convey coded signals is described in U. S. Pat.
No. 1,531,543.
SUMMARY OF THE INVENTION
In one embodiment, the present disclosure applies to a sensory
enhanced audio device. The audio device includes an electroactive
polymer actuator array comprising at least one elastomeric dielectric
element disposed between first and second electrodes. A tray may be
configured to receive the electroactive polymer actuator array and a mass
coupled to the electroactive polymer actuator array. A circuit is electrically
coupled to the electroactive polymer actuator array. The circuit is to
generate a drive signal preferably in the frequency range of about 2 Hz to
about 200 Hz to cause the electroactive polymer actuator array to move or
vibrate according to the drive signal. The electroactive polymer actuators
shake (vibrate) the ear cups in the case of headphones, the vibrations
tracking the incoming low frequency audio, thereby giving the sensation of
low frequency audio without creating high pressure acoustical waves,
which are potentially dangerous to the eardrum. The electroactive
polymer actuators disclosed herein enhance the "listening" experience of
conventional audio devices, such as headphones. With an appropriate
drive signal, the actuator array can also be used to convey information
unrelated to the audio signal. These and other advantages and benefits of
the present invention will be apparent from the Detailed Description of the
Invention herein below.
BRIEF DESCRIPTION OF THE FIGURES
The present invention will now be described for purposes of
illustration and not limitation in conjunction with the figures, wherein:
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-5-
FIG. 1 is a perspective view of a sensory enhanced headphone
according to one embodiment of the present invention;
FIG. 2 is a perspective view of the left ear cup shown in FIG. 1
according to one embodiment;
FIG. 3 is a front view of the left ear cup shown in FIG. 1 according
to one embodiment;
FIG. 4 is a perspective view of the right ear cup shown in FIG. 1
according to one embodiment;
FIG. 5 is a back view of the right ear cup shown in FIG. 1 according
to one embodiment;
FIG. 6 is a sectional view of the right ear cup taken along section
line 6-6 as shown in FIG. 4 according to one embodiment;
FIG. 7 is a sectional view of the right ear cup taken along section
line 6-6 as shown in FIG. 4 according to one embodiment;
FIG. 8 is a front view of the ear cup shown in FIGS. 6 and 7
according to one embodiment;
FIG, 9 is a cutaway view of an electroactive polymer system
according to one embodiment;
FIG. 10 is a schematic diagram of one embodiment of an
electroactive polymer system to illustrate the principle of operation;
FIGS. 11A, 11B, 1C illustrate three possible configurations,
one/three/six bar electroactive polymer actuator arrays, according to
various embodiments;
FIG. 12 is an exploded view of one embodiment of an electroactive
polymer actuator system for an acoustic headphone system according to
one embodiment;
FIG. 13 illustrates an electroactive polymer actuator and speaker
element according to one embodiment;
FIG. 14 illustrates the electroactive polymer actuator shown in FIG.
13 without the mass shown FIG. 13 to show the underlying electroactive
polymer actuator array, according to one embodiment;
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-6-
FIG. 15 illustrates the electroactive polymer actuator shown in FIG.
14 with the tray removed, according to one embodiment;
FIG. 16 illustrates the electroactive polymer actuator shown in FIG.
14 with the mass and the cartridge portion of the electroactive polymer
actuator array removed to show just the tray and a bottom rigid frame
element, according to one embodiment;
FIG. 17 illustrates a top view of an electroactive polymer actuator
according to one embodiment;
FIG. 18 illustrates a sectional view of the electroactive polymer
actuator shown in FIG. 17 taken along section line 18-18, according to
one embodiment;
FIG. 19 is a perspective view of an electroactive polymer actuator,
according to one embodiment;
FIG. 20 is a back view of the electroactive polymer actuator shown
in FIG. 19, according to one embodiment;
FIG. 21 is a sectional view of the electroactive polymer actuator
shown in FIG. 19 taken along section line 21-21, according to one
embodiment;
FIG. 22 is a perspective view of the electroactive polymer actuator
shown in FIG. 19 with the top plate removed to show the underlying mass
located within a suspension tray of the flexure suspension system,
according to one embodiment;
FIG. 23 is a perspective view of the electroactive polymer actuator
shown in FIG. 22 with the mass removed to show the underlying adhesive
layer located above the electroactive polymer actuator array 724,
according to one embodiment;
FIG. 24 is a perspective view of the electroactive polymer actuator
shown in FIG. 23 with the flexure tray removed to better show the base
plate and the underlying 3-bar electroactive polymer actuator array,
according to one embodiment;
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-7-
FIG. 25 is a perspective view of the electroactive polymer actuator
shown in FIG. 24 with the electroactive polymer actuator array removed to
show the underlying base plate and the adhesive layer, according to one
embodiment;
FIG. 26 is a perspective view of the electroactive polymer actuator
shown in FIG. 25 with the adhesive layer and flex circuit removed to show
the underlying base plate and apertures, according to one embodiment;
FIG. 27 is a sectional view of the electroactive polymer actuator
shown in FIG. 19 taken along section line 27-27, according to one
embodiment;
FIG. 28 illustrates one embodiment of an electroactive polymer
actuator;
FIG. 29 is a perspective view of the electroactive polymer actuator
shown in FIG. 28 with the mass removed to show the underlying adhesive
FIG. 30 illustrates a base portion of the tray with the electroactive
polymer actuator array removed, according to one embodiment;
FIG. 31 is perspective view of the electroactive polymer actuator
array portion of the electroactive polymer actuator 800, according to one
embodiment;
FIG. 32 is a graphical representation of test data illustrating the
frequency responses of an electroactive polymer actuator without a flexure
suspension system and suspended mass, where Frequency (Hz) is shown
along the horizontal axis and STROKE (mm) displacement is shown along
the vertical axis;
FIG. 33 is a graphical representation of test data illustrating the
frequency responses of an electroactive polymer actuator with a flexure
suspension system and suspended mass, where Frequency (Hz) is shown
along the horizontal axis and STROKE (mm) displacement is shown along
the vertical axis;
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-8-
FIG. 34 is a perspective sectional view of one embodiment of an
ear cup;
FIG. 35 is a perspective sectional view of the ear cup shown in FIG.
34;
FIG. 36 is a front sectional view of the ear cup shown in FIG. 34;
FIG. 37 illustrates one embodiment of the ear cup shown in FIGS.
34-36 with the circumaural cushion and the housing removed to expose
the underlying standalone tray mounted to a sound cavity behind a
speaker;
FIG. 38 illustrates the ear cup shown in FIG. 37 without the
standalone module housing to expose the electroactive polymer actuator
array, according to one embodiment;
FIG. 39 illustrates the ear cup shown in FIG. 38 without the
electroactive polymer actuator array to shown the underlying mass,
according to one embodiment;
FIG. 40 illustrates the ear cup shown in FIG. 39 without the
underlying mass, according to one embodiment;
FIG. 41 is a bottom view of a sound cavity showing a speaker
mounted therein, according to one embodiment;
FIG. 42 illustrates one embodiment of electroactive polymer based
headphone comprising an electroactive polymer actuator contained in a
first housing portion of an ear cup;
FIG. 43 is a block diagram of an electronic circuit for generating low
frequency audio signals for driving the electroactive polymer actuators and
for reducing unwanted audio noise, according to one embodiment;
FIG. 44 is a graphical representation of harmonic distortion
measurements without the use of the Inverse Polynomial Circuit (e.g.,
"inverse square root circuit") shown in FIG. 43, according to one
embodiment;
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-9-
FIG. 45 is a graphical representation of harmonic distortion
measurements with the Inverse Polynomial Circuit ("square root circuit")
shown in FIG. 43, according to one embodiment;
FIG. 46 illustrates one embodiment of the Inverse Polynomial
Circuit (e.g., "inverse square root circuit") shown in FIG. 43, according to
one embodiment;
FIG. 47 is a partial cutaway view of the electroactive polymer
module shown in FIG. 12 comprising a flexure suspension system,
according to one embodiment;
FIG. 48 is a schematic illustration of one embodiment of the
electroactive polymer module shown in FIGS. 12 comprising the flexure
suspension system shown in FIGS. 12 and 47 comprising a flexure tray,
according to one embodiment;
FIG. 49 illustrates an X and Y axes vibration motion diagram for
modeling the motion of the flexure suspension system shown in FIGS. 12
and 47-48 in the X and Y-directions, according to one embodiment;
FIG. 50 illustrates an X and Z axes vibration motion diagram for
modeling the motion of the flexure suspension system shown in FIGS. 12
and 47-48 in the X and Z-directions, according to one embodiment;
FIG. 51 is a schematic diagram illustrating flexure tray travel stop
features of the flexure suspension system shown in FIGS. 12 and 47-48,
according to one embodiment;
FIG. 52 is a schematic diagram of a flexure linkage beam model,
according to one embodiment;
FIG. 53 illustrates one embodiment of a flexure tray without a mass,
according to one embodiment; and
FIG. 54 illustrates a segment of one embodiment of a flexure tray.
DETAILED DESCRIPTION OF THE INVENTION
Before explaining the embodiments of the inventive sensory
enhanced audio devices and audio noise reduction modules in detail, it
should be noted that the disclosed embodiments are not limited in
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-10-
application or use to the details of construction and arrangement of parts
illustrated in the accompanying drawings and description. The disclosed
embodiments may be implemented or incorporated in other embodiments,
variations and modifications, and may be practiced or carried out in
various ways. Further, unless otherwise indicated, the terms and
expressions employed herein have been chosen for the purpose of
describing the embodiments for illustrative purposes and for the
convenience of the reader and are not intended for the purposes of limiting
any of the embodiments to the particular ones disclosed. Further, it should
be understood that any one or more of the disclosed embodiments,
expressions of embodiments, and examples can be combined with any
one or more of the other disclosed embodiments, expressions of
embodiments, and examples, without limitation. Thus, the combination of
an element disclosed in one embodiment and an element disclosed in
another embodiment is considered to be within the scope of the present
disclosure and appended claims.
The present invention provides a sensory enhanced audio device
comprising an actuator system with having a mechanical Q factor less
than about 10 and a circuit electrically coupled to the actuator system,
wherein the circuit is to generate a drive signal to cause the actuator
system to move according to the drive signal.
The present invention further provides a sensory enhanced
headphone comprising at least one ear cup, an electro active polymer
actuator array located within the at least one ear cup, the electroactive
polymer actuator comprising at least one elastomeric dielectric element
disposed between first and second electrodes and a circuit electrically
coupled to the electroactive polymer actuator array, wherein the circuit is
to generate a drive signal to cause the electroactive polymer actuator
array to vibrate according to the drive signal.
The drive signal used to move the actuator system in the sensory
enhanced audio device is derived from an audio signal. The actuator
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-11-
system useful in the present invention comprises an electroactive polymer
actuator array comprising at least one elastomeric dielectric element
disposed between first and second electrodes.
In one embodiment, the drive signal is designed to move the
actuator system in a way to convey information other than according to the
audio signal. Thus, control of the intensity of the effect due to the motion
of the actuator system can be separate from the control of the intensity of
the audio signal. The user is able to increase, for example, the bass
response of a headphone without being subjected to an increased sonic
response which could potentially be uncomfortable or harmful to the user's
hearing.
In one embodiment, the present disclosure provides high quality low
frequency vibration content to augment limited audio based sensations.
This includes sensory enhanced audio devices such as sensory enhanced
headphones comprising electroactive polymer actuators, for example, as
described in more detail hereinbelow. While not wishing to be bound by
any particular theory, the present inventors speculate the inventive audio
devices rely on a mixture of bone conduction and sound wave effects due
to the inclusion of electroactive polymer actuators,
The present disclosure provides various embodiments of sensory
enhanced headphones containing electroactive polymer actuators. The
electroactive polymer actuators contain electroactive polymer modules
based on dielectric elastomer elements. Such modules possess the
bandwidth and the energy density suitable for implementing electroactive
polymer actuators for use in acoustic headphones and for implementing
mechanical acoustic noise reduction techniques. Such modules are made
from a thin sheet with a dielectric elastomer film sandwiched between two
electrode layers. When a sufficiently high voltage is applied to the
electrodes, the two attracting electrodes compress the dielectric elastomer
film. These modules are slim, low-powered, and can be coupled to an
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-12-
inertial mass to amplify the motion produced by a drive signal derived from
an audio signal source of a host device.
In addition to providing various embodiments of electroactive
polymer actuators for sensory enhanced audio device implementation, in
various aspects, the present disclosure also provides mechanical and
electronic techniques for reducing acoustic noise from a variety of sources.
Each technique is focused on different operational conditions that produce
undesired acoustics and will be described separately hereinbelow.
Various embodiments of the mechanical techniques for reducing
acoustic noise are disclosed. In one embodiment, the mechanical noise
reduction techniques employ electroactive polymer based flexure
suspension systems to minimize and eliminate unwanted modes of
vibration by substantially limiting displacements to a single direction
(desired direction, such as the direction of movement, for example). Test
results support that stable vibrations substantially along a desired direction
of movement can be achieved. The reduction in acoustic noise is highest
when the desired direction is orthogonal to the acoustic radiator axis.
Embodiments of electronic techniques for reducing acoustic noise
are also disclosed. In one embodiment, the electronic acoustic noise
technique employs a non-linear inverse transform to remove unwanted
acoustic artifacts. The basic functioning of electroactive polymer elements
relies on electrostatic pressure produced by an electric field. In its
simplest form, this pressure is proportional to the square of the electric
field. Thus, to compensate for unwanted distortions of the actuator
response, a non-linear inverse transform such as a square root circuit may
be employed. This is true for isotropic, homogeneous, linear dielectric
properties of electroactive polymers as disclosed in more detail
hereinbelow. Other materials that are non-linear, non-isotropic, or non-
homogeneous may require additional electronic and/or mechanical
corrections, for example. Block diagrams depicting examples of electronic
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-13-
topologies for implementing non-linear noise reduction techniques are
shown and described hereinbelow.
Prior to describing the various noise reduction techniques, the
disclosure turns to FIG. 1, which is a perspective view of a sensory
enhanced headphone 100 according to one embodiment. In the
embodiment shown in FIG. 1, the headphone 100 comprises a right ear
cup 102 and a left ear cup 104 intercoupled by a headband 106. The
headband 106 may be any suitable conventional headband. The right and
left ear cups 102, 104 each comprise a corresponding exemplary right and
left circumaural cushion 108, 110. It will be appreciated that the
circumaural cushions 108, 110 may have any shape although traditionally
such cushions are circular or ellipsoid to encompass the ears. Because
the circumaural cushions 108, 110 completely surround the ear, these
headphones 100 can be designed to fully seal against the head to
attenuate any intrusive external noise, for example. The materials of the
cushions 108, 110, may be chosen to modulate the degree of coupling
between the headphone and the user. Each of the right and left ear cups
102, 104 may preferably comprise circumaural cushions 108, 110,
perforated speaker grills 112 (right only shown), and housings 114 (left
only shown). The housing 114 contains a speaker, an electroactive
polymer actuator, a circuit board comprising circuits to drive the actuator,
and in some embodiments and mechanical and/or electronic acoustic
noise reduction components. Embodiments of these elements are
described hereinbelow.
FIG. 2 is a perspective view of the left ear cup 104 and FIG. 3 is a
front view of the left ear cup 104. As shown in FIGS. 2 and 3, the left ear
cup 104 comprises a circumaural cushion 110 and a perforated speaker
grill 116.
FIG. 4 is a perspective view of the right ear cup 102 and FIG. 5 is a
back view of the right ear cup 102. As shown in FIGS. 4 and 5, the right
ear cup 102 comprises a housing 118.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-14-
FIGS. 6 and 7 are sectional views of the right ear cup 102 taken
along section line 6-6 as shown in FIG. 4. FIG. 8 is a front view of the
ear cup 102 shown in FIGS. 6 and 7. Since the left ear cup 104 is
substantially similar to the right ear cup 102, for conciseness and clarity of
disclosure the remainder of this description provides focuses on the
structure and function of the right ear cup 102 although such attributes
may pertain equally to the left ear cup 104.
With reference now in particular to FIGS. 6-8, in one embodiment
the right ear cup 102 comprises a housing 118, which defines an opening
124 suitable for mounting a speaker 120 and an electroactive polymer
actuator 122 therein. In the embodiment illustrated in FIGS. 6-8, the
actuator 122 comprises several sub-components and thus may be
occasionally referred to herein as a electroactive polymer module. In
particular embodiments where the actuator 122 includes three-bars, for
example, the actuator 122 may be referred to as a 3-bar electroactive
polymer module, without limitation. In particular embodiments where the
actuator 122 comprises a flexure suspension system, for example, the
actuator 122 may be referred to as an inertial electroactive polymer
module, without limitation. With reference now back to FIGS. 6-8, the
speaker 120 can be mounted directly behind the perforated speaker grill
112, as shown. In other embodiments however, the location of the
speaker 120 may vary and may be mounted in any suitable location within
the opening 124 of the housing 118. In one embodiment, for example, the
electroactive polymer actuator 122 can be mounted to an inner wall 132
portion of the housing 118. In one embodiment, the actuator 122 may
comprise a tray 126, an electroactive polymer actuator array 128, and a
mass 130. In one embodiment, the tray 126 may be replaced with a
flexure suspension system as discussed in more hereinbelow for
minimizing, reducing, or substantially eliminating acoustic noise arising
unwanted modes of vibration by substantially limiting displacements to a
single desired direction of movement, for example. Electroactive polymer
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-15-
actuator arrays such as the actuator 128 also may be referred to herein as
an "n-bar cartridge," where "n" stands for the number of actuator bars in
the array. Thus, a 3-bar standalone cartridge refers to an electroactive
polymer actuator array comprising three actuator bars that is mounted in a
tray without flexure elements. Conversely, a 3-bar inertial cartridge refers
to an electroactive polymer actuator array comprising three bars that is
mounted in flexure suspension system. It will be appreciated that any of
the disclosed headphone embodiments comprising a standalone actuator
tray such as the tray 126 may be replaced with flexure suspension trays,
without limitation.
With reference now to FIGS. 1-6, in one embodiment, the sensory
enhanced headphones 100 comprising electroactive polymer actuators
122 according to the present disclosure are capable of producing
mechanical vibrations in the audio frequency band (e.g., about 20 Hz to
about 20 kHz) to provide high quality audio sensations without creating
high sound pressures in the ear. In one embodiment, each of the ear cups
102, 104 comprise the electroactive polymer actuator 122. Each of the
actuators 122 comprises a small mass 130 (preferably from 1 to 50 g,
more preferably 25 g) attached to the electroactive polymer actuator array
128 forming a simple mass/spring/damper resonant system. Low
frequency portions of the incoming audio are passed to an audio amplifier
that is connected to the actuators 122. The electroactive polymer
actuators 122 shake (vibrate) the ear cups 102, 104, the vibrations
tracking the incoming low frequency audio, thereby giving the sensation of
low frequency audio without creating high pressure acoustical waves,
which are potentially dangerous to the eardrum. The electroactive
polymer actuators 122 disclosed herein enhance the "listening" experience
of conventional audio headphones. The generation of low frequency (20
Hz - 200 Hz) vibrations extends the perceived frequency range of the
audio headphones 100 below their normal, optimal range.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-16-
The vibrations generated by the electroactive polymer actuators
122, however, are non-linear in nature. In addition, electroactive polymer
based actuators 122 may also produce acoustic vibrations that may, or
may not, be desirable. In the case of undesirable acoustic vibrations, the
present disclosure also provides mechanical and electrical techniques to
reduce the undesirable acoustic effects to acceptable levels. At times, the
vibrations may be out-of-plane with the speaker 120. Vibrational
augmentation may be added to the sensory enhanced headphones 100, if
desired, by employing voice coils for driving suspended masses. These
implementations, however, may result in high Q systems having low
damping such that they vibrate longer in the same axis as the acoustic
radiator, thereby introducing undesirable acoustic artifacts. In various
embodiments, however, the electroactive polymer actuators 122 disclosed
herein may be oriented in such a manner that the plane of vibration is
perpendicular to the acoustic radiator axis, thereby significantly reducing
unwanted acoustic artifacts.
The mechanical Q factor characterizes the mechanical damping of
a system. It is the ratio of the reactive energy over the mechanical energy
loss. As noted hereinabove, high Q systems vibrate longer creating more
acoustic artifacts and less well defined effects. Low Q values indicate
systems with high mechanical losses so vibrations are easily damped and
the motion of the actuator system is well defined.
For optimal performance, the Q of the actuator system should be
preferably below 10, more preferably below 5, and most preferably
between 1.5 and 3.
As those skilled in the art are aware, Qms is a unit less
measurement, characterizing the mechanical damping of the driver, that is,
the losses in the suspension (surround and spider.) It varies roughly
between 0.5 and 10, with a typical value around 3. High Qms indicates
lower mechanical losses, and low Qms indicates higher losses. The main
effect of Qms is on the impedance of the driver, with high Qms drivers
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-17-
displaying a higher impedance peak. One predictor for low Qms is a
metallic voice coil former. These act as eddv-current brakes and increase
damping, reducing Qms and must be designed with an electrical break in
the cylinder. Some speaker manufacturers have placed shorted turns at
the top and bottom of the voice coil to prevent it leaving the gap, but the
sharp noise created by this device when the driver is overdriven is
alarming and was perceived as a problem by owners. Low Qms drivers
are often built with nonconductive formers, made from paper, or various
plastics.
The resonant frequency of the actuator system should be tailored to
the type of effects desired. For example, a resonant frequency in the
range of 80 to 90 Hz is desired to maximize the effect or "punch" of
percussive effects such as kick drums. The motion of the actuator system
should be orthogonal to the direction of the sound waves if a separate
speaker is used. While other types of actuators such as piezoelectric
transducers, voice coils, linear resonant motors, and eccentric rotating
motors can be used, electroactive polymer actuators are particularly well
suited to meet the above criteria for this application. They can be designed
to have intrinsically low Q factors in the appropriate resonant frequency
range of about 50-100 Hz while retaining fast response times and high
power in a small, lightweight, and energy-efficient form factor that is more
easily incorporated into a sensory enhanced audio device. They can be
directly driven by the drive circuit to track and enhance an audio signal or
to produce specifically tailored effects independent of the audio signal.
With the low modulus of the dielectric film in an electroactive polymer
actuator, preferably less than 100 MPa, a smaller inertial mass can be
used to amplify the motion of the actuator than needs to be used with
higher modulus materials such as piezoelectric polymers or crystals. This
lowers the overall volume and mass of the actuator system which may be
an important factor in the design of portable audio devices such as
headphones.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-18-
Before launching into a further description of various embodiments
of the electroactive polymer actuator 122, as shown in connection with
FIGS. 6-8, for example, the description turns briefly to FIGS. 9-11 for a
description of various integrated devices comprising electroactive polymer
based modules suitable for use in audio devices such as headphones.
FIG. 9 is a partial cutaway view of an electroactive polymer system that
may be integrally incorporated into the actuator 122 to provide the
necessary vibratory motion to the headphone 100. Accordingly, in one
embodiment the system comprises a electroactive polymer module 200.
An electroactive polymer actuator 222 is configured to slide an output plate
202 (e.g., sliding surface) relative to a fixed plate 204 (e.g., fixed
surface)
when energized by a voltage "V." The plates 202, 204 are separated by
steel balls, and have features that constrain movement to the desired
direction, limit travel, and withstand drop tests. For integration into a
headphone device, the top plate 202 may be attached to an inertial mass,
such as the mass 130 shown in FIGS. 6-8. In FIG. 9, the top plate 202 of
the electroactive polymer module 200 includes a sliding surface configured
to mount to an inertial mass or the back of a surface that can move bi-
directionally as indicated by arrow 206. Between the output plate 202 and
the fixed plate 204, the electroactive polymer module 200 comprises at
least one electrode 208, optionally at least one divider 210, and at least
one output bar 212 that attach to the sliding surface, e.g., the top plate
202. Frame and divider segments 214 attach to a fixed surface, e.g., the
bottom plate 204. The module 200 may comprise any number of bars 212
configured into arrays to amplify the motion of the sliding surface. The
electroactive polymer module 200 may be coupled to the drive electronics
of an actuator controller circuit via a flex cable 216, A voltage "V"
potential
difference of preferably about 1 kV (preferably anywhere up to 5 kV, more
preferably between 100 V to 5 kV, more preferably between 300 V to 5 kV)
may be applied to first and second electrically conductive elements 218A,
218B of the flex cable.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-19-
Segmenting the electroactive polymer actuator 222 within a given
footprint into (n) sections is a convenient method for setting the passive
stiffness and blocked force of the electroactive polymer system. A pre-
stretched dielectric is held in place by the rigid material that defines an
external frame such as the fixed plate 204 and one or more windows
within the frame. Inside each window is an output bar 212 of the same
rigid frame material, and on one or both sides of the output bar 212 are
electrodes 208. Alternatively, an adhesive may replace the rigid frame
material as disclosed in co-assigned International PCT Patent Application
No. PCT/US2012/021511, filed January 17, 2012 entitled FRAMELESS
ACTUATOR APPARATUS, SYSTEM AND METHOD, which application
claims the benefit, under 35 USC 119(e), of United States provisional
patent application numbers: 61/433,640 filed January 18, 2011 entitled,
"FRAMELESS DESIGN CONCEPT AND PROCESS FLOW"; 61/442,913
filed February 15, 2011 entitled, "FRAME-LESS DESIGN"; 61/447,827
filed March 1, 2011, entitled, "FRAMELESS ACTUATOR, LAMINATION
AND CASING"; 61/477,712 filed April 21, 2011, entitled, "FRAMELESS
APPLICATION"; and 61/545,292 filed October 10, 2011, entitled, "AN
ALTERNATIVE TO Z-MODE ACTUATORS"; the entire disclosure of which
is hereby incorporated by reference. Applying the potential difference (V)
across the dielectric on one side of the output bar 212 creates electrostatic
pressure in the elastomer which causes the electrode area to expand and
exert force on the output bar 212. This force scales with the effective
cross section of the electroactive polymer actuator 222, and therefore
increases linearly with the number of segments, each of which adds to the
effective width of the actuator. The passive spring rate scales with n2, as
each additional segment effectively stiffens the device twice, first by
shortening it in the stretching direction (X) and second by adding to the
width (Y) that resists displacement. Both spring rate and blocked force
scale linearly with the number of dielectric layers (m).
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-20-
Advantages electroactive polymer modules 200 include the ability to
generate low frequency vibrations inside the ear cup housings that can be
felt substantially immediately by the user. In addition, electroactive
polymer modules 200 consume low power, and are well suited for
customizable design and performance options. The electroactive polymer
module 200 is representative of electroactive polymer modules developed
by Artificial Muscle, Inc., of Sunnyvale, CA, USA.
Still with reference to FIG. 9, many of the design variables of the
electroactive polymer module 200, (e.g., thickness, footprint) may be fixed
by the needs of module integrators while other variables (e.g., number of
dielectric layers, operating voltage) may be constrained by cost. Because
actuator geometry ¨ the allocation of footprint to rigid supporting structure
versus active dielectric ¨ does not impact cost much, it may be a
reasonable way to tailor performance of the electroactive polymer module
200 to an application where the module 200 is integrated with a
headphone device, as shown in FIGS. 6-8.
Computer implemented modeling techniques can be employed to
gauge the merits of different actuator geometries, such as: (1) Mechanics
of the Handset/User System; (2) Actuator Performance; and (3) User
Sensation. Together, these three components provide a computer-
implemented process for estimating the capability of candidate designs
and using the estimated capability data to select an electroactive polymer
design suitable for mass production. The model predicts the capability for
two kinds of effects: long effects (gaming and music), and short effects
(key clicks). "Capability" is defined herein as the maximum sensation a
module can produce in service. Such computer-implemented processes
for estimating the capability of candidate designs are described in more
detail in commonly assigned International PCT Patent Application No.
PCT/US2011/000289, filed February 15, 2011, entitled "ELECTROACTIVE
POLYMER APPARATUS AND TECHNIQUES FOR QUANTIFYING
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-21-
CAPABILITY THEREOF," the entire disclosure of which is hereby
incorporated by reference.
FIG. 10 is a schematic diagram of an electroactive polymer system
300 designed to illustrate the principle of operation of electroactive
polymer modules. The electroactive polymer system 300 comprises a
power source 302, shown as a low voltage direct current (DC) battery for
illustrative purposes, electrically coupled to an electroactive polymer
module 304. In accordance with the present disclosure, the power source
(VBatt) represents the output of an audio signal source configured to
generate low frequency audio signals below about 200 Hz, for example,
and in one embodiment between about 2 Hz to about 200 Hz, where the
term "about" stands for 10%. The electroactive polymer module 304
comprises a thin elastomeric dielectric element 306 disposed (e.g.,
sandwiched) between two conductive electrodes 308A, 308B. The
conductive electrodes 308A, 308B are stretchable (e.g., conformable) and
may be printed on the top and bottom portions of the elastomeric dielectric
element 306 using any suitable technique, such as, for example screen
printing. The electroactive polymer module 304 is activated by coupling
the battery 302 (e.g., signal source) to an actuator circuit 310 by closing a
switch 312. The actuator circuit 310 converts the low DC voltage VBatt
signal into a higher DC voltage Vin signal suitable for driving the
electroactive polymer module 304. In accordance with the present
disclosure, an additional circuit may be located within the opening 124
defined by the housing 118, where the circuit is configured to convert the
low voltage low frequency audio signal from the audio signal source, to a
higher voltage signal suitable for driving the electroactive polymer actuator
122 (FIGS. 6-8). Returning to FIG. 10, when the voltage Vin is applied to
the conductive electrodes 308A, 308B the elastomeric dielectric element
306 contracts in the vertical direction (V) and expands in the horizontal
direction (H) under electrostatic pressure. The contraction and expansion
of the elastomeric dielectric element 306 can be harnessed as motion.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
The amount of motion or displacement is proportional to the input voltage
V. The motion or displacement may be amplified by a suitable
configuration of electroactive polymer actuators as described below in
connection with FIGS. 11A, 11B, and 11C.
FIGS. 11A, 11B, 11C illustrate three possible configurations, among
others, of electroactive polymer actuator arrays 400, 420, 440, according
to various embodiments. Various embodiments of electroactive polymer
actuator arrays may comprise any suitable number of bars depending on
the application and physical spacing restrictions of the application.
Additional bars provide additional displacement and therefore may be
employed to enhance the realistic sound reproduction vibration that the
user can sense immediately. The electroactive polymer actuator arrays
400, 420, 440 may be coupled to the drive electronics of an actuator
controller circuit via a corresponding flex cable 402, 422, 442.
FIG. 11A illustrates an example of a one bar electroactive polymer
actuator array 400. The one bar electroactive polymer actuator array 400
comprises a fixed plate 404, an output bar 406, and an elastomeric
dielectric element 408 coupled to the fixed plate 404.
FIG. 11B illustrates an example of a three bar electroactive polymer
actuator array 420 comprising three bars 424, 426, 428 coupled to a fixed
frame 430. Each pair of bars is separated by a divider 432. Each of the
three bars 424, 426, 428 comprises an output bar 434 and an elastomeric
dielectric element 436. The three bar electroactive polymer actuator array
420 amplifies the motion of the sliding surface in comparison to the single
bar electroactive polymer actuator array 400 of FIG. 11A.
FIG. 11C illustrates an example of a six bar electroactive polymer
actuator array 440 comprising six bars 444, 446, 448, 450, 452, 454
coupled to a fixed frame 456, where each pair of bars is separated by a
divider 458. Each of the six bars 444, 446, 448, 450, 452, 454 comprises
an output bar 460 and an elastomeric dielectric element 462. The six bar
electroactive polymer actuator array 440 amplifies the force on the sliding
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-23-
surface in comparison to the single bar electroactive polymer actuator
array 400 of FIG. 11A and the three bar electroactive polymer actuator
array 420 of FIG. 11B.
The electroactive polymer actuator arrays 400, 420, 440 illustrated
in reference to FIGS. 113A-C may be integrated into a variety of
electroactive polymer actuators for headphone applications to achieve
desired effects. For example, in one embodiment, an electroactive
polymer actuator array may be configured to be mounted into an inner
surface of a housing 118 as illustrated in FIGS. 6-8. In the embodiment
shown in FIGS. 6-8, an electroactive polymer actuator array 128 is
integrated with the electroactive polymer actuator 122 to implement a
sensory enhanced headphone.
FIG. 12 is an exploded view of one embodiment of an electroactive
polymer module 500 comprising a flexure suspension system 502 that
may be employed in a sensory enhanced headphone. Examples of
flexure suspension systems that may be employed in the disclosed
embodiments can be found at commonly assigned International PCT
Patent Application No. PCT/US2012/021506, filed on January 17, 2012,
entitled "ELECTROACTIVE POLYMER FLEXURE APPARATUS,
SYSTEM, AND METHOD," which application claims the benefit, under 35
USC 119(e), of United States provisional patent application numbers:
61/433,655, filed January 18, 2011, entitled "SLIDING MECHANISM AND
AMI ACTUATOR INTEGRATION"; 61/477,680, filed April 21, 2011,
entitled "Z-MODE BUMPERS"; 61/493,123, filed June 3,2011, entitled
"FLEXURE SYSTEM DESIGN"; 61/493,588, filed June 6, 2011, entitled
"ELECTRICAL BATTERY CONNECTION"; and 61/494,096, filed June 7,
2011, entitled "BATTERY VIBRATOR FLEXURE WITH METAL BATTERY
CONNECTOR FLEXURE"; the entire disclosure of each of which is hereby
incorporated by reference. In one embodiment, a flexure tray 504 defines
an opening 510 for receiving an electroactive polymer actuator 506 (shown
in exploded view format) therein. One side of the electroactive polymer
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-24-
actuator 506 can be mounted to the bottom portion of the flexure tray 504
and the other side of the actuator 506 can be coupled to a mass 508. The
electroactive polymer actuator 506 and the mass 508 are dimensioned to
fit within the opening 510 defined by the tray 504. As shown in FIG. 12,
the actuator 506 comprises two sets of electroactive polymer actuator
arrays 512, 512'. In other embodiments, one electroactive polymer
actuator array 512 may be employed and in other embodiments, for
example, more than two sets of electroactive polymer actuator arrays 512,
512' may be employed in the electroactive polymer actuator 506. As
shown, the first and second sets of electroactive polymer actuator arrays
512, 512' each comprise an output bar adhesive layer 514A, 514A` to
couple a first set of electroactive polymer actuator arrays 514B, 514B' to
the bottom of the mass 508. A frame-to-frame adhesive layer 514C, 514C'
is used to couple the first set of electroactive polymer actuator arrays
514B, 514B` to a second set of electroactive polymer actuator arrays
5140, 514D'. A base frame adhesive layer 514E, 514E couples the
second set of electroactive polymer actuator arrays 514D, 514D' to the
mounting surface 516 inside the tray 504. As shown in FIG. 12, the
electroactive polymer actuator 506 comprises dual three bar electroactive
polymer actuator arrays. In other embodiments, as described
hereinbelow, any suitable number of electroactive polymer actuator arrays
comprising any suitable number of bars may be employed. Although not
shown in FIG. 12, either the mass 508 or the tray 504 may be physically
and/or electrically connected to a printed circuit board with a flex cable
connector, for example. The flexure suspension system 502 can be used
to implement an acoustic headphone system as described in more detail
hereinbelow. Additional details of the flexure suspension system 502 are
described hereinbelow in connection with FIGS. 47-54.
Having generally described various integrated devices comprising
electroactive polymer feedback modules that may be employed in various
embodiments of the electroactive polymer actuator 122 shown in FIGS. 6-
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-25-
8, the description now turns to FIGS. 13-16, which illustrate one
embodiment of the electroactive polymer actuator 122. In FIG. 13, the
housing 118 and the circumaural cushion 108 portions of the ear cup 102
are not shown in order to more clearly illustrate the electroactive polymer
actuator 122 and the speaker 120 elements, according to one
embodiment. In the illustrated embodiment, the electroactive polymer
actuator 122 comprises the standalone tray 126 (e.g., in other
embodiments, the tray 126 may be replaced by a flexure suspension
system), which defines an opening 136 for holding the mass 130 and the
electroactive polymer actuator array 128 (shown in FIGS. 14-15) beneath
the mass 130. The tray 126 comprises a perimeter surface 134 for
attaching the electroactive polymer actuator 122 to the inner wall 132
(FIGS. 7-8) of the housing 118. The tray 126 includes a slot 138 to
receive a flex cable to electrically couple the electroactive polymer
actuator array 128 to an actuator circuit.
FIG. 14 illustrates the electroactive polymer actuator 122 without
the housing 118 and the circumaural cushion 108 portions of the ear cup
102 and further without the mass 130 (FIG. 13) to show the underlying
electroactive polymer actuator array 128, according to one embodiment.
As shown in FIG. 14, the electroactive polymer actuator array 128 is
located in the tray 126. FIG. 15 illustrates the electroactive polymer
actuator shown in FIG. 14 with the tray removed, according to one
embodiment. With reference to FIGS. 14-15, the electroactive polymer
actuator array 128 comprises a rigid frame and dividers 142 separating
electrodes 148 and elastomeric dielectric elements 146. An adhesive
layer 144 is provided on a top surface of the electrodes 148 to adhesively
mount a top surface of the electroactive polymer actuator array 128 to a
bottom surface of the mass 130. Because the electroactive polymer
actuator array 128 comprises three sets of electrodes 148 and elastomeric
dielectric elements 146, the electroactive polymer actuator array 128 may
be referred to as a 3-bar cartridge.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-26-
FIG. 16 illustrates the electroactive polymer actuator 122 shown in
FIG. 15 with the mass 130 and the cartridge portion of the electroactive
polymer actuator array 128 removed to show just the tray 126 and a
bottom rigid frame element 142, according to one embodiment.
FIGS. 17 and 18 illustrate a top view and a sectional view, taken
along section line 18-18, of a electroactive polymer actuator 600
according to one embodiment. The electroactive polymer actuator 600
comprises a flexure suspension system 622 and may be employed in the
headphones 100 in place of the electroactive polymer actuator 122 shown
in FIGS. 1,6-8 and 13-16. The flexure suspension system 622 comprises
a suspension tray 608, a mass 602, and a electroactive polymer actuator
array 624 (shown in FIG. 18). As shown in FIG. 18, the electroactive
polymer actuator 600 comprises a top plate 610 located over the flexure
suspension system 622 and a base plate 612 having frame and divider
segments 614 separating three sets of output bars 616 and elastomeric
dielectric elements 618. Accordingly, the electroactive polymer actuator
600 is a 3-bar inertial electroactive polymer module. The electroactive
polymer actuator 600 comprises electroactive polymer actuators located
within a suspension tray 608 of the flexure suspension system 622. The
suspension tray 608 comprises suspension or flexure arms 604, 606. The
electroactive polymer actuator 600 defines an X-Y plane of vibration. The
flexure suspension system 622 limits travel primarily to one direction, e.g.,
along the Y axis as indicated by the arrow 620. Limited movement in the Z
direction helps to maintain clearances required for free movement in the Y
direction. When the electroactive polymer actuator 600 is energized by a
voltage derived from a low frequency audio signal, the suspension tray
608 moves substantially along the Y axis, as indicated by the arrow 620,
and motion along the X and Z axes is substantially minimized. Thus, the
electroactive polymer actuator 600 comprising the flexure suspension
system 622 substantially reduces or eliminates undesirable acoustic
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
.27..
effects. The flexure suspension system 622 also may be used to generate
acoustic effects to intentionally add artifacts to sound tracks.
In one embodiment, the flexure suspension system 622 comprises
at least one flexure coupled to the electroactive polymer actuator array
624, wherein the flexure enables the flexure suspension system 622 to
move in a predetermined direction when the first and second electrodes in
elastomeric dielectric elements 618 are energized. In one embodiment,
the flexure suspension system 622 comprises at least one travel stop to
limit movement of the suspension tray 608 in the predetermined direction.
In one embodiment, the suspension tray 608 comprises the at least one
flexure arm 604, 606. In one embodiment, the flexure tray 608 comprises
at least one travel stop to limit movement of the flexure suspension system
622 in the predetermined direction. In one embodiment, at least one of the
flexure arms is formed integrally with the suspension tray 608.
FIGS. 19-27 illustrate one embodiment of an electroactive polymer
actuator 700 comprising a flexure suspension system 722 similar to the
flexure suspension system 622 shown in FIGS. 17 and 18. FIG. 19 is a
perspective view of the electroactive polymer actuator 700 and FIG. 20 is
a back view of the actuator, according to one embodiment. FIG. 21 is a
sectional view of the electroactive polymer actuator 700 taken along
section line 21-21 and FIG. 27 is a sectional view of the electroactive
polymer actuator 700 taken along section line 27-27 as shown in FIG. 19,
according to one embodiment. With reference now to FIGS. 19-21 and 27,
in addition to the flexure suspension system 722, in one embodiment, the
electroactive polymer actuator 700 comprises a top plate 710, a base plate
712, and a slot 726 to receive a flex cable 728 to electrically couple the
electroactive polymer actuator array 724 to an electronic drive circuit 740
via first and second electrically conductive elements 736A, 736B. The
base plate 712 includes apertures 730 that reveal the output bar 716
portions of the electroactive polymer actuator array 724.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-28-
FIG. 21 shows a mass 702 and a first adhesive layer 732 located
between the electroactive polymer actuator array 724 and the base plate
712 to adhesively attach the electroactive polymer actuator 700 to the
base plate 712, according to one embodiment. A second adhesive layer
734 is located between the mass 702 and the electroactive polymer
actuator array 724 to adhesively attach the electroactive polymer actuator
array 724 to a bottom surface of the mass 702.
FIG. 22 is a perspective view of the electroactive polymer actuator
700 with the top plate 710 removed to show the underlying mass 702
located within a suspension tray 708 of the flexure suspension system
722, according to one embodiment. The suspension tray 708 comprises
first and second suspension arms 704, 706. As discussed in connection
with FIGS. 17 and 18, the suspension arms 704, 706 formed in the
suspension tray 708 enables the flexure suspension system 722 to move
in a predetermined manner. For example, the suspension arms 704, 706
of the flexure suspension system 722 limit the travel of the mass 702 in the
X-Y plane primarily along the Y axis as indicated by the arrow 720.
Limited movement in the Z direction helps to maintain clearances required
for free movement in the Y direction. Accordingly, when the electroactive
polymer actuator 700 is energized by a higher voltage derived from a low
frequency audio signal, the suspension tray 708 moves in the direction of
motion indicated by arrow 720, which is substantially along the Y axis.
FIG. 23 is a perspective view of the electroactive polymer actuator
700 shown in FIG. 22 with the mass 702 removed to show the underlying
adhesive layer 734 located above the electroactive polymer actuator array
724, according to one embodiment. The adhesive layer 734 adhesively
couples the electroactive polymer actuator array 724`to a bottom surface
of the mass 702. The electroactive polymer actuator array 724 also
comprises a frame and divider segments 714 that separate the three
separate output bars 716 and elastomeric dielectric elements 718.
Because the electroactive polymer actuator array 724 includes three bars,
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-29-
it may be referred to as a 3-bar inertial electroactive polymer module,
without limitation.
FIG. 24 is a perspective view of the electroactive polymer actuator
700 shown in FIG. 23 with the flexure tray 708 removed to better show the
base plate 712 and the underlying 3-bar electroactive polymer actuator
array 724, according to one embodiment. As shown in FIG. 24, the
electroactive polymer actuator array 724 comprises frame and divider
segments 714, output bars 716, elastomeric dielectric elements 718, and a
adhesive layer 734 located above the output bars 716.
FIG. 25 is a perspective view of the electroactive polymer actuator
700 shown in FIG. 24 with the electroactive polymer actuator array 724
removed to show the underlying base plate 712 and the adhesive layer
732, according to one embodiment. The base plate 712 comprises
apertures 730 and the adhesive layer 732 located between the base plate
712 and the electroactive polymer actuator array 724. The first and
second electrical conductors 736A, 736B of the flex circuit 728 are
electrically connected to corresponding first and second terminals 738A,
738B.
FIG. 26 is a perspective view of the electroactive polymer actuator
700 shown in FIG. 25 with the adhesive layer 732 and flex circuit 728
removed to show the underlying base plate 712 and apertures 730,
according to one embodiment.
FIGS. 28-31 illustrate one embodiment of a electroactive polymer
actuator 800. In one embodiment, the electroactive polymer actuator 800
comprises a tray 822, a mass 802, and a slot 826 formed in the tray 822.
The slot 826 is dimensioned to receive a flex cable (nOt shown) to
electrically couple the electroactive polymer actuator array 824 to an
electronic drive circuit. FIG. 30 illustrates a base portion of the tray 822
with the electroactive polymer actuator array 824 removed, according to
one embodiment. The base portion of the tray 822 includes apertures 830
that reveal output bars 816 of the electroactive polymer actuator array 824.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-30-
The mass 802 is adhesively coupled to the electroactive polymer actuator
array 824 by a adhesive layer 834 located therebetween. The
electroactive polymer actuator 800 defines a plane of vibration indicated
by the X-Y plane. The tray 822 limits travel primarily in one direction along
the Y axis as indicated by the arrow 820. Limited movement in the Z
direction helps to maintain clearances required for free movement in the Y
direction. Accordingly, when the actuator 800 is energized by a higher
voltage derived from a low frequency audio signal, the tray 822 moves in
the direction of motion indicated by arrow 820, which is substantially along
the Y axis.
FIG. 29 is a perspective view of the electroactive polymer actuator
800 shown in FIG. 28 with the mass 802 removed to show the underlying
adhesive layer 834, according to one embodiment. As shown, the
adhesive layer 834 is located above the electroactive polymer actuator
array 824, which is located beneath the mass 802. The electroactive
polymer actuator array 824 is adhesively coupled to a bottom surface of
the mass 802 with the adhesive layer 834. The electroactive polymer
actuator array 824 also comprises a frame and divider segments 814 that
separate the three separate output bars 816 and elastomeric dielectric
elements 818 of the electroactive polymer actuator array 824. Because
the electroactive polymer actuator array 824 includes three bars, it may be
referred to as a 3-bar electroactive polymer module, without limitation.
FIG. 31 is perspective view of the electroactive polymer actuator array 824
portion of the electroactive polymer actuator 800, according to one
embodiment.
FIGS. 32 and 33 are graphical representations 900, 950 of test data
illustrating the frequency responses of two types of electroactive polymer
actuators, respectively, where Frequency (Hz) is shown along the
horizontal axis and STROKE (mm) displacement is shown along the
vertical axis. The graph 900 shown in FIG. 32 shows the frequency
response curve of an electroactive polymer actuator without a flexure
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-31-
suspension system and suspended mass, such as the electroactive
polymer actuator 122 (FIGS. 6-8 and 13) and the electroactive polymer
actuator 800 (HG. 28) that relies primarily on the motion of the
electroactive polymer actuator array to move the suspended mass. At
some frequencies (specifically 20Hz to 50Hz) the suspended mass
wobbles because it is free to move in all directions and there is no
limitation or support in the undesired directions. This phenomenon
manifests itself as distortions 902, 904 in the desired direction
displacement and ultimately desired sensation. The graph 950 shown in
FIG. 33 shows the frequency response curve of an electroactive polymer
actuator that utilizes a flexure suspension system, such as the flexure
suspension system 622, 722 of the respective actuators 600, 700 shown in
FIGS. 17-19. Areas 952 and 954 clearly show that the undesired
distortions have been successfully eliminated by the flexure suspension
system 622, 722.
FIGS. 34-40 illustrate one embodiment of an ear cup 1000 that may
be employed in the sensory enhanced headphone 100 shown in FIG. 1.
FIGS. 34 and 35 are perspective sectional views of the ear cup 1000 and
FIG. 36 is a front sectional view of the ear cup, according to one
embodiment. With reference now in particular to FIGS. 34-36, in one
embodiment the right ear cup 1000 comprises a circumaural cushion 1008
and a housing 1018, which defines an opening 1024 suitable for mounting
a speaker 1020 and a electroactive polymer actuator 1022 therein. In the
embodiment illustrated in FIGS. 34-36, the electroactive polymer actuator
1022 may be referred to as an electroactive polymer module. More
particularly, in the embodiment illustrated in FIGS. 34-36, the electroactive
polymer actuator 1022 may be referred to as a 3-bar inertial electroactive
polymer module, without limitation. As shown, the speaker 1020 can be
mounted directly behind a perforated speaker grill 1012. In other
embodiments, however, the location of the speaker 1020 may vary. In one
embodiment, the actuator 1022 comprises a standalone tray 1026
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-32-
configured to receive an electroactive polymer actuator array 1028 and a
mass 1030 therein. The electroactive polymer actuator 1022 is mounted
to a sound cavity 1050, which is mounted directly behind the speaker
1020. In other embodiments, the actuator 1022 may comprise a flexure
suspension system, such as the flexure suspension system 622, 722 of
the respective actuators 600, 700 shown in FIGS. 17-19, for example, to
mechanically correct for minor distortions at the lower frequencies (e.g.,
less than 200 Hz). The actuator 1022 also comprises a electroactive
polymer actuator array 1028 and a mass 1030.
FIGS. 37-41 illustrate various elements of the ear cup 1000 with
other elements removed in order to show the underlying structures,
according to one embodiment. Accordingly, FIG. 37 illustrates one
embodiment of the ear cup 1000 with the circumaural cushion 1008 and
the housing 1018 removed to expose the underlying standalone tray 1026
mounted to the sound cavity 1050 behind the speaker 1020.
FIG. 38 illustrates the ear cup 1000 shown in FIG. 37 without the
standalone module housing 1026 to expose the electroactive polymer
actuator array 1028, according to one embodiment. The electroactive
polymer actuator array 1028 comprises a rigid frame and dividers 1042
separating output bars 1048 and elastomeric dielectric elements 1046. An
adhesive layer 1044 is provided on the output bars 1048 to adhesively
mount the electroactive polymer actuator array 1028 to the standalone tray
1026. A mass 1030 may suspended from flexures (not shown) attached to
standalone tray 1026. A second adhesive layer (not shown) may be
provided to adhesively mount the standalone tray 1026 to the sound cavity
1050.
FIG. 39 illustrates the ear cup 1000 shown in FIG. 38 without the
electroactive polymer actuator array 1028 to show the underlying mass
1030, according to one embodiment. FIG. 40 illustrates the ear cup 1000
shown in FIG. 39 without the underlying mass 1030 and FIG. 41 is a
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-33-
bottom view of the sound cavity 1050 showing the speaker 1020 mounted
therein, according to one embodiment.
Having described various electroactive polymer headphone
embodiments including mechanical techniques for reducing acoustic
noise, the disclosure now turns to electronic methods of reducing the
acoustic noise that can be implemented into any of the embodiments of
the electroactive polymer actuators described herein. Embodiments of
electronic acoustic noise reduction techniques employing non-linear
inverse transforms to remove unwanted acoustic artifacts are described
hereinbelow. First, however, the disclosure turns briefly to FIG. 42, which
illustrates one embodiment of sensory enhanced headphone 1100
comprising an electroactive polymer actuator 1102 contained in a first
housing portion 1104 of an ear cup 1110. A circuit board 1106 comprising
electronic circuits for driving the electroactive polymer actuator 1102 at low
audio frequencies and for reducing unwanted acoustic noise is also
shown. The circuit board 1106 may be mounted behind the electroactive
polymer actuator 1102. The entire assembly of the electroactive polymer
actuator 1102 and the circuit board 1106 may be located between the first
housing portion 1104 and a second housing portion 1108.
FIG. 43 is a block diagram 1200 of an electronic circuit for
generating low frequency audio signals for driving the electroactive
polymer actuators and for reducing unwanted audio noise, according to
one embodiment. A variety of signal conditioning, amplifying,
compensating, and driving circuits are also implemented. In particular, an
analog audio signal module 1202 receives analog audio signal from a
differential amplifier source. In one embodiment, the differential amplifier
may be implemented with any suitable integrated circuit amplifier, such as,
for example an AD822 single-supply, rail-to-rail low power field effect
transistor-input operational amplifier, available from Analog Devices, Inc.
of Norwood, MA, or any suitable equivalent thereof.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-34-
An automatic gain control module 1204 receives the output signal
from the analog audio signal module 1202 and provides automatic gain
control from 0 dB to 20 dB, for example, or any suitable gain. In one
embodiment, the automatic gain control module 1204 may be
implemented with any suitable integrated circuit amplifier such as, for
example, a MAX9814 microphone amplifier with automatic gain control
and low-noise microphone bias, available from Maxim Integrated Products,
Inc. of Sunnyvale, CA, or any suitable equivalent thereof. In one
embodiment, the automatic gain control module 1204 is configured to
control the volume of vibration for driving the electroactive polymer
actuators in each of the ear cups differently from the volume of the actual
audio sound signal. Although the vibration level for driving the
electroactive polymer actuators in each of the ear cups is different from the
volume of the actual audio sound signal, the vibration level gain is
correlated or based on the audio sound level gain. In various
embodiments, the relationship between the vibration level gain and the
audio sound level gain may be linear or non-linear depending on the
specific design implementation. In one embodiment, the relationship
between the gains is non-linear in order to approximate a non-linear
function such as sine, square-root, logarithmic, exponential, and the like.
In the illustrated embodiment, the relationship between the vibration level
gain and the audio sound level gain is a non-linear function that
approximates a square-root function. In other words, the vibration level
gain is approximately correlated to the square-root of the audio sound
level gain. Thus, the electroactive polymer actuator vibrations track the
incoming low frequency audio and give the sensation of low frequency
audio without creating high pressure acoustical waves, which may be
potentially dangerous to the eardrum.
In one embodiment, the vibration level gain approximates a square-
root of the audio sound level gain as shown in TABLE 1.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-35-
TABLE 1
Audio Sound Audio Sound I Vibration Level Vibration Level
Level Gain (dB) Level Gain j Gain (dB)
Gain
3.16 5 1.78
10
10 3.16 ..
31.6 ........... 15 5.62
100 20 ___________ 10
From the automatic gain control module 1204, the signal is passed
to a low frequency digital filter module 1206. The low frequency digital
5 filter module 1206 may be implemented using any suitable circuit
technique and may comprise a microcontroller and a programmable gate
array circuit, among other digital or analog processing circuit elements. In
one embodiment, the low frequency digital filter module 1206 may be
implemented with any suitable programmable system, such as, for
10 example a CY8C29466 programmable system-on-chip controller, available
from Cypress Semiconductor Corporation, of San Jose, CA, or any
suitable equivalent thereof.
A low frequency amplifier module 1208 amplifies the output of the
low frequency digital filter 1206 and the output is passed to the
15 programmable gate array circuit. In one embodiment, the low frequency
amplifier module 1208 may be implemented using any suitable integrated
circuit amplifier such as the MAX9618 low-power, zero-drift operational
amplifier, available from Maxim Integrated Products, Inc. of Sunnyvale,
CA, or any suitable equivalent thereof.
20 The output of the low frequency digital filter 1206 is provided to a
non-linear inverse transform circuit (square root circuit) such as an inverse
polynomial circuit 1210, which provides the electronic audio signal
compensation to remove unwanted distortions in the audio signal used to
vibrate the electroactive polymer actuators. In other words, the inverse
25 polynomial circuit 1210 approximates an inverse function to linearize
the
electroactive polymer actuators, for example. In various embodiments, the
inverse polynomial circuit 1210 may be implemented using integrated
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-36-
circuits, programmable circuits, piecewise linear circuits and/or any
combinations thereof. In one embodiment a piecewise linear circuit can be
used to approximate a non-linear function, such as sine, square-root,
logarithmic, exponential, and the like, for example. The quality of the
approximation depends on the number of segments employed by the
piecewise linear circuit and the strategy used in determining the segments.
Generally speaking, there are two approaches to building piecewise linear
circuits: (1) non-linear voltage dividers with diodes (or transistors) used to
switch between the segments and (2) summing the outputs of a chain of
saturating amplifiers. Both of these approaches may be employed and are
technically equivalent although each has its advantages and
disadvantages.
The diode approach has the advantage of simplicity but the
disadvantages include temperature dependence on the switching
thresholds and relatively slow response. The saturating amplifier method
has the disadvantage of complexity but the advantages of minimal
temperature dependence on thresholds and high speed. In various
embodiments, the inverse polynomial circuit 1210 may be implemented as
a compression or an expansion circuit, each type having a different circuit
topology. A compression circuit compresses the dynamic range of an
input signal whereas an expansion circuit expands the dynamic range.
Examples of compression circuits include square-root, logarithmic, and
sine and generally employ non-linear voltage divider techniques. One
example of an expansion circuit is an exponential function. In other
embodiments, a combination of compression and expansion circuits may
be employed to implement the inverse polynomial circuit 1210 to linearize
electroactive polymer actuators, for example. One embodiment of a
piecewise linear circuit using diode switching to approximate an inverse
square-root function is described in more detail herein in connection with
FIG. 46.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-37-
The output of the inverse polynomial circuit 1210 is provided to a
high voltage power amplifier 1212 for amplification to a level sufficient to
drive the electroactive polymer actuator module, In general, the voltage
required to drive the electroactive polymer actuator module may range
from a few hundred volts (V) to several thousand volts (kV), with a nominal
driving voltage of about 1kV. A left channel output 1214L of the high
voltage amplifier 1212 is provided to a left reflex actuator and mass 1216L,
e.g., to an electroactive polymer actuator located in a left ear cup of the
headphones. A right channel output 1214R of the high voltage amplifier
1212 is provided to a right reflex actuator and mass 1216R, e.g., to an
electroactive polymer actuator located in a right ear cup of the
headphones. In one embodiment, single phase actuators can be
improved using a square root circuit in the sensory enhanced headphones
comprising electroactive polymer actuators. Non-linear control techniques
also may be employed in multi-phase actuators, for example.
In one embodiment, the electronic circuit includes a visual feedback
display module 1218. In this embodiment, a blue display (e.g., light
emitting diode or LED) indicates audio signals. A green display indicates
processed signals. An orange/red display indicates mixed and high
voltage signals. Those skilled in the art will appreciate any combination of
desired colors may be used to provide the visual feedback.
FIG. 44 is a graphical representation of harmonic distortion
measurements 1300 without the use of the inverse polynomial circuit 1210
(e.g., "inverse square root circuit") shown in FIG. 43, according to one
embodiment. The bottom trace 1302 is a measured acceleration
waveform at 100 Hz without the square root circuit 1210 and the top trace
1304 is the Fourier transform showing a high second harmonic 1306.
FIG. 45 is a graphical representation of harmonic distortion
measurements 1350 with the Inverse Polynomial Circuit 1210 ("square
root circuit") shown in FIG, 43, according to one embodiment. The bottom
trace 1352 is a measured acceleration waveform at 100 Hz with the
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-38-
square root circuit 1210 and the top trace 1354 is the Fourier transform
showing a significantly reduced second harmonic 1356.
FIG. 46 illustrates one embodiment of an inverse polynomial circuit
1210 described in FIG. 43 employing a piecewise linear circuit using diode
switching to approximate an inverse square-root function. As described in
connection with FIG. 43, other nonlinear circuit topologies may be
employed to implement a linearization function to linearize the
electroactive polymer actuators and the topology described in connection
with FIG. 46 is but one example. Accordingly, embodiments of inverse
polynomial circuits should not be limited in this context. In the
embodiment illustrated in FIG. 46, the inverse polynomial circuit 1210
comprises a voltage-to-current converter circuit 1220, a piecewise linear
circuit 1230 employing a diode switching topology, and a final gain
amplifier 1240. The output voltage 1/0 is provided to a high voltage power
amplifier 1212, as shown in FIG. 43, for example.
The voltage-to-current converter circuit 1220 employs a first
amplifier Al and resistors R1-R4 to generate a current i that is proportional
to the input voltage Vin, from the low frequency digital filter module 1206 in
FIG. 43. The current i is provided to the piecewise linear circuit 1230,
which his configured to approximate an inverse square-root function
(current-to-voltage) using R5-R15 and diodes Dl-D5. The final gain
amplifier 1240, which included resistors R16-R17 and a second amplifier
A2, sets the final scaling (with R16 and R17) and could be any value
between 1 and 100, but typically is between 1 and 2.
In the illustrated embodiment, the piecewise linear circuit 1230
includes five segments that are switched in depending on the current i and
the node voltage vn that develops. Each segment has a break point
voltage that approximates a different slope based on the input voltage
range of vn. For example, the first segment has a first breakpoint voltage
Vi equal to VA plus the diode voltage drop across Dl. Similarly, the
second segment has a second breakpoint voltage V2 equal to VB plus the
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-39-
diode voltage drop across D2, and so on, up to segment five, which has a
fifth breakpoint voltage V5 equal to VE plus the diode voltage drop across
D5. Each segment has a different slope that is based on the parallel
combination of resistors R5-R15. As each segment is switched in, the
slope changes such that the voltage ttri at the node approximates an
inverse square-root function depending on the values selected for the
resistors. The piecewise linear circuit 1230 also may implement a square-
root or other non-linear function depending on the resistor values selected.
The amplifiers Al and A2 may be any suitable integrated circuit amplifier,
such as, for example, an AD823 rail-to-rail FET-input operational amplifier,
available from Analog Devices, Inc. of Norwood, MA, or any suitable
equivalent thereof. In one embodiment, the voltage V+ may be +5V, for
example.
In one embodiment, the resistors R1-R4 to implement the voltage-
to-current converter circuit 1220, the resistors R5-R15 to implement the a
piecewise linear circuit 1230, and the resistors R16-R17 to implement the
final gain amplifier 1240 are shown in TABLE 2. It will be appreciated that
the values of the resistors may have different tolerances depending on the
level of accuracy to be achieved and may be - 10%, - 5, - 1, or may be
trimmed to any suitable value.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-40-
............................................. TABLE 2
Resistor ................ I Value (1(0) ( 10%, 5, 1, or trimmed)
R1 2 _______________________________________
_______________ R2 ...
........................................... 2 ______________
R3 10
............... R4
___________________________________________
¨ R5 ...................................... 3
R6 3 ..
--------------- R7 3
R8 3
R9 3
R10 7.8
_______________ R11 5 ..........
R12 _______________________________________ 10 __
,
R13 20 .............
_______________ R14 100
R15 1000
R16 ....................................... 1
R17
10
FIGS. 47-54 illustrate additional details of flexure suspension
systems according to disclosed embodiments. FIG. 47 is a partial cutaway
5 view of the electroactive polymer module 500 shown in FIG. 12 comprising
a flexure suspension system, according to one embodiment.
FIG. 48 is a schematic illustration of one embodiment of the
electroactive polymer module 500 shown in FIGS. 12 comprising the
flexure suspension system 506 shown in FIGS. 12 and 47 comprising a
10 flexure tray 504, according to one embodiment. With reference to FIGS.
47 and 48, the flexure tray 504 comprises flexures 570, travel stops 572,
574, and a mass 508 located within the opening defined by the flexure tray
504. The flexures 570 and travel stops 572, 574 can be molded into the
flexure tray 504 or can be provided as separate components. As
previously discussed, the flexure tray 504 is coupled to a mounting surface
568, which acts as a mechanical ground for the flexure suspension system
502. The flexures 570 located in one or more locations enable the flexure
tray 504 to vibrate in one or more directions of motion. In the illustrated
embodiment, the flexure tray 504 comprises four separate flexures 570
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-41-
that enable the flexure tray 504 to move in the X and Y-directions. The
flexure tray 504 also comprises X-travel stops 572 and Y-travel stops 574
to limit travel or movement in a predetermined direction and prevent
damage from shock type movement. The X- and Y-travel stops 572, 574
are provided to constrain the motion of the flexure tray 504 in the X and Y-
directions of motion, as discussed in more detail with reference to FIGS,
49 and 60 below, such that the flexure suspension system 502 can limit
unwanted vibrations in undesired directions of movement.
FIG. 49 illustrates an X and Y axes vibration motion diagram 580 for
modeling the motion of the flexure suspension system 502 shown in FIGS.
12 and 47-48 in the X and Y-directions, according to one embodiment.
FIG. 50 illustrates an X and Z axes vibration motion diagram 582 for
modeling the motion of the flexure suspension system 502 shown in FIGS.
12 and 47-48 in the X and Z-directions, according to one embodiment.
With reference now to FIGS. 12 and 47-50, kfx = combined stiffness of the
flexures 570 and electrical connections in the X-axis, kax = active stiffness
of the electroactive polymer actuator 506 in the X-axis, kfz = combined
stiffness of the flexures 570 and electrical connection in the Z-axis, kaz =
stiffness of the electroactive polymer actuator 506 in the Z-axis, mtray
Mbatt = total sprung mass consisting of the mass 508 and any other support
structure in motion.
X-Axis Compliance
Compliance in the X-axis is one factor to consider when evaluating
the performance of the flexure suspension system 502. Combined non- =
actuator stiffness (kfx) should be reduced as much as possible and kept
below about 10% of the actuator stiffness (kax), for example. Additional
stiffness from electrical interconnects should be factored into the non-
actuator stiffness calculations. Stiffness of the flexures 570 in the X-axis
provides suitable movement control with proper use of the travel stops
572, 574.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-42-
Z-Axis Compliance
Compliance in the Z-axis should be reduced as much as possible to
reduce deflection of the dynamic mass due to gravity or user input, and in
particular, when the flexure suspension system 502 is integrated with a
touch surface (e.g., touch screen or touch pad) suspension application
where unrestricted X-axis movement of the assembly should be insured
during user input. Ideally the total Z-axis stiffness can be over 300X the
total X-axis stiffness. If negative Z-direction (¨Z-direction) travel stops
are
not used, the flexure 570 should be configured to withstand force and
shock that may be experienced during removal of the mass 508.
Y-Axis Compliance
With properly designed flexures 570, compliance in the Y-axis is
relatively small as the flexure 570 beams are either in compression or
tension. Any compliance in the Y-axis is the result of buckling or
stretching of the flexure 570, which is undesirable in all situations. The
amount of deflection in the Y-axis should be minimized to prevent damage
to the flexures 570 during movement, for example.
TABLE 3 below provides total flexure stiffness based on stiffness
being less than 10% of total electroactive polymer actuator 506 stiffness,
according to one embodiment, where the values provided are approximate
example values.
TABLE 3
Total Flexure Stiffness (Stiffness < 10% of total Electroactive Polymer ---
Actuator Stiffness)
Sprung Mass
(mbatt
12.5g 25g === 125g 150g
3-Bar Actuator
2 4 õ, 20 24
Layers
Total Actuator
2.8kN/m 5.6kN/rn
2810,1/m 30.8kN/m
Stiffness (kax)
Total Flexure X-
Stiffness 125N/m 250N/m
1.25kN/m 1.375kNim
Allowance (kfx)
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-43-
FIG. 51 is a schematic diagram 584 illustrating the flexure tray 504
travel stop 572, 574 features of the flexure suspension system 502 shown
in FIGS. 12 and 47-48, according to one embodiment. In the flexure
suspension system 502 illustrated in FIG. 51, an electroactive polymer
layer 586 is distributed through a plurality of screen printed electroactive
polymer actuator frames 588 that are alternatively attached to the
mounting surface 568 of a device and the base of the flexure tray 504 by
an adhesive sheet 590. The flexure 570 is represented symbolically for
convenience and clarity. In one embodiment, the stops 572, 574 are
provided where possible while allowing free movement of the dynamic
mass under normal loads. The travel stops 572, 574 prevent over
extension and damage to the flexures 570 and the electroactive polymer
actuator 506. The embodiment of the flexure 570 presented herein lends
itself well to built-in travel stops 572, 574 in all axes except for the --Z-
direction where pulling of the mass 508 out of the flexure tray 504 may
cause damage. A positive Z-direction (+Z-direction) stop may be
implemented using the actuator frame itself, which may be suitable to
survive industry standard drop testing up to 1.5m, for example.
TABLE 4 below provides flexure tray stop 572, 574 clearances,
according to one embodiment. The clearances labeled A-F in TABLE 4
below are approximate example values and correspond to similarly labeled
clearances in FIG. 51.
TABLE 4 .....................................
Flexure Tra Stop Clearances
Dimension Minimum Average _______ Maximum
...... A 0.1 mm ............ 0.25 mm 0.5 mm
0.1 mm 0.25 mm 1.0 mm
0.1 mm 0.25 mm 0.29 mm
0.2 mm 0.5 mm 1.0 mm
N/A 0.4/0.6 mm N/A
1!
1F N/A 0.13 mm N/A 1
FIG. 52 is a schematic diagram 592 of a flexure linkage 594 beam
model, according to one embodiment. The flexure linkages 594 can be
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-44-
made from a number of materials. In one embodiment, the flexure
linkages 594 may be made of plastic using an injection molded set of
linkages built into the handset back-shell or a tablet battery mount frame,
for example. In such embodiments, the flexure linkage material may be
made of a moldable plastic such as acrylonitrile-butadiene-styrene, for
example, without limitation. Applications involving larger Z-direction loads
and/or having limited space, flexure linkages 594 may be made of sheet
metal and can be molded into a plastic frame. Alternatively, an entire
stamped sheet metal subassembly can be made and used in applications
that require the larger Z-direction loads. The stiffness of an individual
linkage 594 can be calculated using the beam model shown in FIG. 52, for
example, where the deflection of the flexure linkage 594 in the X- and Z-
directions (dx and dz) under corresponding forces (Fx and Fz) is modeled.
FIG. 53 illustrates one embodiment of a flexure tray 504 without the
mass 508. The flexure tray 504 comprises a rigid outer frame 596 that is
fixedly mounted to a mounting surface. In the illustrated embodiment, the
rigid outer frame 596 may be fixedly mounted to the mounting surface by
way of fasteners inserted through one or more apertures 598. Typical
fasteners include screws, bolts, rivets, and the like. As shown in FIG. 53,
the flexure tray 504 comprises flexures 570 that enable the flexure tray
504 to move in the X and Y-direction to provide a vibro-electroactive
polymer stimulus of the user. Also shown are the X-travel stops 572 and
Y-travel stops 574 to prevent over extension and damage to the flexures
570 and electroactive polymer actuator.
FIG. 54 illustrates a segment 599 of one embodiment of the flexure
tray 504. The segment 599 shows the diameters (pi and (P2 of the flexure
570 as well as the overlapping distance di between two flexure segments
and the distance d2 between bent segments of the flexure 570. TABLE 5
provides reference design flexure parameters, according to one
embodiment, where the values provided are approximate example values.
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-45-
_______________________________ TABLE 5
Reference Design Flexure Parameters
Material P430 ABS Plus (3D printed FDM
process)
Actuator 8L 3-Bar
Sprung Mass /
jilbatt altray) 609 ...................................................
L = 15 mm
b = 0.3 mm
h = 5 mm _________________________________
kx = 92 Nim
N = 6
_____________________________ kfx(total) 552 N/m
_______________________________ ktz = 153.3k Nim
It is to be appreciated that the embodiments described herein
illustrate example implementations, and that the functional elements,
logical blocks, program modules, and circuits elements may be
implemented in various other ways which are consistent with the described
embodiments. Furthermore, the operations performed by such functional
elements, logical blocks, program modules, and circuits elements may be
combined and/or separated for a given implementation and may be
performed by a greater number or fewer number of components or
program modules. As will be apparent to those of skill in the art upon
reading the present disclosure, each of the individual embodiments
described and illustrated herein has discrete components and features
which may be readily separated from or combined with the features of any
of the other several embodiments without departing from the scope of the
present disclosure. Any recited method can be carried out in the order of
events recited or in any other order which is logically possible.
Although certain modules and/or blocks may be described by way
of example, it can be appreciated that a greater or lesser number of
modules and/or blocks may be used and still fall within the scope of the
embodiments. Further, although various embodiments may be described
in terms of modules and/or blocks to facilitate description, such modules
and/or blocks may be implemented by one or more hardware components
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-46-
(e.g., processors, digital signal processors, programmable logic devices,
application-specific integrated circuits, circuits, registers), software
components (e.g., programs, subroutines, logic) and/or combination
thereof.
Numerous specific details have been set forth herein to provide a
thorough understanding of the embodiments. It will be understood by
those skilled in the art, however, that the embodiments may be practiced
without these specific details. In other instances, well-known operations,
components and circuits have not been described in detail so as not to
obscure the embodiments. It can be appreciated that the specific
structural and functional details disclosed herein may be representative
and do not necessarily limit the scope of the embodiments.
It is worthy to note that any reference to "one embodiment" or "an
embodiment" means that a particular feature, structure, or characteristic
described in connection with the embodiment is included in at least one
embodiment. The appearances of the phrase "in one embodiment" or "in
one aspect" in the specification are not necessarily all referring to the
same embodiment.
It is worthy to note that some embodiments may be described using
the expression "coupled" and "connected" along with their derivatives.
These terms are not intended as synonyms for each other. For example,
some embodiments may be described using the terms "connected" and/or
"coupled" to indicate that two or more elements are in direct physical or
electrical contact with each other. The term "coupled," however, may also
mean that two or more elements are not in direct contact with each other,
but yet still co-operate or interact with each other.
It will be appreciated that those skilled in the art will be able to
devise various arrangements which, although not explicitly described or
shown herein, embody the principles of the present disclosure and are
included within the scope thereof. Furthermore, all examples and
conditional language recited herein are principally intended to aid the
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-47-
reader in understanding the principles described in the present disclosure
and the concepts contributed to furthering the art, and are to be construed
as being without limitation to such specifically recited examples and
conditions. Moreover, all statements herein reciting principles,
embodiments, and embodiments as well as specific examples thereof, are
intended to encompass both structural and functional equivalents thereof.
Additionally, it is intended that such equivalents include both currently
known equivalents and equivalents developed in the future, i.e., any
elements developed that perform the same function, regardless of
structure. The scope of the present disclosure, therefore, is not intended
to be limited to the exemplary embodiments and embodiments shown and
described herein. Rather, the scope of present disclosure is embodied by
the appended claims.
The terms "a" and "an" and 'the" and similar referents used in the
context of the present disclosure (especially in the context of the following
claims) are to be construed to cover both the singular and the plural,
unless otherwise indicated herein or clearly contradicted by context.
Recitation of ranges of values herein is merely intended to serve as a
shorthand method of referring individually to each separate value falling
within the range. Unless otherwise indicated herein, each individual value
is incorporated into the specification as if it were individually recited
herein.
All methods described herein can be performed in any suitable order
unless otherwise indicated herein or otherwise clearly contradicted by
context. The use of any and all examples, or exemplary language (e.g.,
"such as," "in the case," "by way of example") provided herein is intended
merely to better illuminate the invention and does not pose a limitation on
the scope of the invention otherwise claimed. No language in the
specification should be construed as indicating any non-claimed element
essential to the practice of the invention. It is further noted that the
claims
may be drafted to exclude any optional element. As such, this statement
is intended to serve as antecedent basis for use of such exclusive
CA 02839339 2013-12-13
WO 2012/173669
PCT/US2012/026421
-48-
terminology as solely, only and the like in connection with the recitation of
claim elements, or use of a negative limitation.
Groupings of alternative elements or embodiments disclosed herein
are not to be construed as limitations. Each group member may be
referred to and claimed individually or in any combination with other
members of the group or other elements found herein. It is anticipated
that one or more members of a group may be included in, or deleted from,
a group for reasons of convenience and/or patentability.
While certain features of the embodiments have been illustrated as
described above, many modifications, substitutions, changes and
equivalents will now occur to those skilled in the art. It is therefore to be
understood that the appended claims are intended to cover all such
modifications and changes as fall within the scope of the disclosed
embodiments and appended claims.
