Note: Descriptions are shown in the official language in which they were submitted.
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PIEZOELECTRIC ACTUATOR APPARATUS AND METHODS
FIELD OF DISCLOSURE
[0001] The present disclosure relates to piezoelectric actuators, including
but not
limited to, piezoelectric actuator apparatus and methods.
BACKGROUND
[0002] Electronic devices, including portable electronic devices, have gained
widespread use and may provide a variety of functions including, for example,
telephonic, electronic messaging, and other personal information manager (PIM)
application functions. Portable electronic devices include, for example,
several types
of mobile stations such as simple cellular telephones, smart telephones,
wireless
personal digital assistants (PDAs), and laptop computers with wireless 802.11
or
Bluetooth capabilities.
[0003] Portable electronic devices such as PDAs or smart telephones are
generally intended for handheld use and ease of portability. Smaller devices
are
generally desirable for portability. A touch-sensitive display, also known as
a
touchscreen display, is particularly useful on handheld devices, which are
small and
have limited space for user input and output. The information displayed on the
touch-sensitive displays may be modified depending on the functions and
operations being performed. With continued demand for decreased size of
portable
electronic devices, touch-sensitive displays continue to decrease in size. In
addition
to the touch-sensitive display, electronic devices often include a keypad to
input
commands or information.
[0004] Some electronic devices use piezoelectric elements or disks to provide
haptic feedback to a user of an electronic device via, for example, a touch-
sensitive
display. Typically, piezoelectric elements have a conductive layer or shim and
a
piezoelectric material layer. In one known actuator assembly, a set of four
piezo
disks are disposed within shallow wells formed in a support plate. Flexible
conductive leads are coupled to both the shim and the piezoelectric material
layer
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of each piezoelectric element via, for example, conductive adhesive,
soldering, etc.
Such flexible conductive leads are susceptible to cracking, which can result
in
electrical arcing, poor mechanical response and/or insufficient tactile
feedback.
Additionally, coupling the flexible conductive leads to the both the shim and
the
piezoelectric material layer significantly increases manufacturing complexity
and
costs.
[0005] Thus, it is desired to provide an improved piezoelectric actuator
apparatus
while reducing manufacturing complexity and costs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a block diagram of a portable electronic device in accordance
with the disclosure.
[0007] FIG. 2A is a schematic illustration of an example piezoelectric
actuator
apparatus described herein that may be used to implement the example portable
electronic device of FIG. 1.
[0008] FIG. 2B is an exploded view of the example piezoelectric actuator
apparatus of FIG. 2A.
[0009] FIG. 3A is a cross-sectional view of a portion of the example
piezoelectric
actuator apparatus of FIGS. 2A and 2B installed with the portable electronic
device
of FIG. 1.
[0010] FIG. 3B is a plan view of the example assembly of FIG. 3A.
DETAILED DESCRIPTION
[0011] Piezoelectric actuator apparatus to provide tactile or haptic feedback
to,
for example, a touch-sensitive display are described herein. For example, the
actuators may be controlled via a processor or other circuitry to provide
tactile
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= feedback via the touch-sensitive display to simulate, for example,
depression or
actuation of a switch that may be utilized as part of a physical key of a
keyboard
(e.g., a dome switch, snap switch, etc.) or any other type of switch that may
be
simulated. Such tactile feedback may be provided in response to depression and
release of the touch-sensitive display (e.g., a liquid crystal display).
[0012] An example piezoelectric actuator apparatus described herein includes a
support plate having at least one recessed well to receive a conductive
contact that
directly engages a conductive layer of a piezoelectric element to provide a
charge to
the piezoelectric element. The support plate includes a conductive trace or
path
between the conductive contact and a connector of the support plate to
electrically
couple the conductive layer of the piezoelectric element to, for example, a
switch, a
voltage source (e.g., a battery), an integrated circuit, etc. The conductive
contact is
coupled to the connector via a dedicated conductive trace or path so that a
first
piezoelectric element coupled to the support plate is electrically isolated
from a
second piezoelectric element coupled to the support plate. In this manner,
each
piezoelectric elements coupled to the support plate may be analyzed and/or
activated individually, simultaneously, intermittently and/or any other
desired
pattern.
[0013] Further, the piezoelectric actuator apparatus described herein reduce
manufacturing complexity and costs. In particular, the example piezoelectric
actuator apparatus eliminates the need to couple or attach a flexible
conductive
lead to the conductive layer of the piezoelectric element. Such elimination of
the
conductive lead significantly improves reliability and/or longevity of the
electrical
connection between the conductive layer of the piezoelectric element and the
conductive contacts of the support plate. Additionally or alternatively,
eliminating a
flexible conductive lead to the conductive layer of the piezoelectric element
significantly reduces manufacturing complexity and costs. In the examples
described herein, only the piezoelectric material of the piezoelectric
actuator is
coupled to, for example, a ground via a flexible conductive lead.
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[0014] For simplicity and clarity of illustration, reference numerals may be
repeated among the figures to indicate corresponding or analogous elements.
Numerous details are set forth to provide an understanding of the embodiments
described herein. The embodiments may be practiced without these details. In
other instances, well-known methods, procedures, and components have not been
described in detail to avoid obscuring the examples described. The description
is
not to be considered as limited to the scope of the examples described herein.
[0015] The disclosure generally relates to electronic devices such as, for
example, a portable electronic device in the examples described herein.
Examples
of portable electronic devices include mobile, or handheld, wireless
communication
devices such as pagers, cellular phones, cellular smart-phones, wireless
organizers,
personal digital assistants, wirelessly enabled notebook computers, and so
forth.
The portable electronic device may also be a portable electronic device
without
wireless communication capabilities, such as a handheld electronic game
device,
digital photograph album, digital camera, or other device.
[0016] A block diagram of an example of a portable electronic device 100 is
shown in FIG. 1. The portable electronic device 100 includes multiple
components,
such as a processor 102 that controls the overall operation of the portable
electronic device 100. Communication functions, including data and voice
communications, are performed through a communication subsystem 104. Data
received by the portable electronic device 100 is decompressed and decrypted
by a
decoder 106. The communication subsystem 104 receives messages from and
sends messages to a wireless network 150. The wireless network 150 may be any
type of wireless network, including, but not limited to, data wireless
networks, voice
wireless networks, and networks that support both voice and data
communications.
A power source 142, such as one or more rechargeable batteries or a port to an
external power supply, powers the portable electronic device 100.
[0017] The processor 102 interacts with other components, such as Random
Access Memory (RAM) 108, memory 110, a display 112 with a touch-sensitive
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overlay 114 operably connected to an electronic controller 116 that together
comprise a touch-sensitive display 118, one or more actuator apparatus 120,
one
or more force sensors 122, an auxiliary input/output (I/O) subsystem 124, a
data
port 126, a speaker 128, a microphone 130, short-range communications 132, and
other device subsystems 134. User-interaction with a graphical user interface
is
performed through the touch-sensitive overlay 114. The processor 102 interacts
with the touch-sensitive overlay 114 via the electronic controller 116.
Information,
such as text, characters, symbols, images, icons, and other items that may be
displayed or rendered on a portable electronic device, is displayed on the
touch-
sensitive display 118 via the processor 102. The processor 102 may interact
with
an accelerometer 136 that may be utilized to detect direction of gravitational
forces
or gravity-induced reaction forces.
[0018] To identify a subscriber for network access, the portable electronic
device
100 uses a Subscriber Identity Module or a Removable User Identity Module
(SIM/RUIM) card 138 for communication with a network, such as the wireless
network 150. Alternatively, user identification information may be programmed
into
memory 110.
[0019] The portable electronic device 100 includes an operating system 146 and
software programs or components 148 that are executed by the processor 102 and
are typically stored in a persistent, updatable store such as the memory 110.
Additional applications or programs may be loaded onto the portable electronic
device 100 through the wireless network 150, the auxiliary I/O subsystem 124,
the
data port 126, the short-range communications subsystem 132, or any other
suitable subsystem 134.
[0020] A received signal such as a text message, an e-mail message, or web
page download is processed by the communication subsystem 104 and input to the
processor 102. The processor 102 processes the received signal for output to
the
display 112 and/or to the auxiliary I/O subsystem 124. A subscriber may
generate
data items, for example e-mail messages, which may be transmitted over the
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wireless network 150 through the communication subsystem 104. For voice
communications, the overall operation of the portable electronic device 100 is
similar. The speaker 128 outputs audible information converted from electrical
signals, and the microphone 130 converts audible information into electrical
signals
for processing.
[0021] The touch-sensitive display 118 may be any suitable touch-sensitive
display, such as a capacitive, resistive, infrared, surface acoustic wave
(SAW)
touch-sensitive display, strain gauge, optical imaging, dispersive signal
technology,
acoustic pulse recognition, and so forth, as known in the art. A capacitive
touch-
sensitive display includes a capacitive touch-sensitive overlay 114. The
overlay 114
may be an assembly of multiple layers in a stack including, for example, a
substrate, a ground shield layer, a barrier layer, one or more capacitive
touch
sensor layers separated by a substrate or other barrier, and a cover. The
capacitive
touch sensor layers may be any suitable material, such as patterned indium tin
oxide (ITO).
[0022] One or more touches, also known as touch contacts or touch events, may
be detected by the touch-sensitive display 118. The processor 102 may
determine
attributes of the touch, including a location of a touch. Touch location data
may
include an area of contact or a single point of contact, such as a point at or
near a
center of the area of contact. The location of a detected touch may include x
and y
components, e.g., horizontal and vertical components, respectively, with
respect to
one's view of the touch-sensitive display 118. For example, the x location
component may be determined by a signal generated from one touch sensor, and
the y location component may be determined by a signal generated from another
touch sensor. A signal is provided to the controller 116 in response to
detection of a
touch. A touch may be detected from any suitable object, such as a finger,
thumb,
appendage, or other items, for example, a stylus, pen, or other pointer,
depending
on the nature of the touch-sensitive display 118. Multiple simultaneous
touches
may be detected. The touches may be detected by the force sensor 122, which
generates a signal to the processor 102. The processor 102, in turn, provides
a
signal to actuate or activate the actuators 120 to provide tactile feedback to
a user.
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[0023] FIG. 2A illustrates an example piezoelectric actuator assembly 200
described herein that may be used to implement the actuator 120 of FIG. 1.
FIG.
2B illustrates an exploded view of the example piezoelectric actuator assembly
200
of FIG. 2A. Referring to FIGS. 2A and 2B, in this particular example, the
piezoelectric actuator assembly 200 comprises one or more piezoelectric
(piezo)
elements or devices 202a-d that provide tactile feedback to the touch-
sensitive
display 118. As described in greater detail below, each piezoelectric elements
202a-
d may be controlled independently from each other. For example, the
piezoelectric
element 202a may be activated prior to, or instead of, the piezoelectric
element
202b to provide a first tactile feedback. In another example, the
piezoelectric
element 202a may be activated to provide a first tactile feedback (e.g., a
first force
or vibration) that is different than a tactile feedback (e.g., a second force
or
vibration) provided by the piezoelectric element 202b.
[0024] In this particular example, each piezoelectric elements 202a-d
comprises
a piezoelectric material or layer 204 adjacent a second layer material or
substrate
206. The piezoelectric material 204 is fastened or adhered to the substrate
206
via, for example, adhesive, lamination, laser welding, and/or by other
suitable
fastening method(s). The substrate 206 is composed of an electrically
conductive
material to provide an electrical connection to the piezoelectric material
204. The
substrate 206, which may also be referred to as a shim, may be comprised of
nickel
or any other suitable material such as, for example, stainless steel, brass,
etc. The
piezoelectric material 204 may be a piezoelectric (PZT) ceramic disk, and may
have
a single layer of the piezoelectric material 204 or any suitable number of
piezoelectric materials or layers composed of, for example, ceramic, lead
zirconate
titanate or any other suitable piezoelectric material(s).
[0025] The piezoelectric actuator assembly 200 includes a chassis or support
plate 208 composed of a non-conducting or electrical insulating material such
as,
for example, a hard plastic. In this particular example, the support plate 208
is a
unitary piece or structure composed of a hard plastic material. In other
examples,
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the support plate 208 may be a multi-layer support structure having a support
layer
composed of, for example, metal and an insulating layer composed of, for
example,
a plastic material. For example, the support layer composed of metal may be
formed via stamping and may be covered by the insulating layer via over
molding
or vacuum molding.
[0026] In this particular example, the support plate 208 includes a plurality
of
recessed wells or shallow tubs 210a-d. The recessed wells 210a-d are formed
with
the non-conducting or electrical insulating material or layer 204 of the
support plate
208. A plurality of conductive contacts 212a-d such as a copper element or
disk are
disposed within or coupled to the respective recessed wells 210a-d. The
recessed
wells 210a-d may have a depth that may partially or fully receive the
piezoelectric
elements 202a-d. In some examples, the conductive contacts 212a-d may be
integrally formed with the support plate 208. For example, the support plate
208
may be composed of, for example, metal (e.g., aluminum, copper, etc.) that may
be covered by an electrical insulating material (e.g., a plastic material)
that
includes openings that substantially align with the recessed wells 210a-d to
enable
the conductive contacts 212a-d (or portions of the metal support plate 208) to
be
exposed via the openings of the insulating material.
[0027] The piezoelectric elements 202a-d are coupled to the respective
conductive contacts 212a-d, which are disposed within the recessed wells 210a-
d.
More specifically, the substrate 206 of the piezoelectric elements 202a-d is
coupled
to the conductive contacts 212a-d to provide an electrical connection to the
piezoelectric elements 202a-d. For example, the substrate 206 is fastened or
coupled (e.g., directly coupled) to the conductive contacts 212a-d via, for
example,
an electrically conductive bonding agent, adhesive, cement, soldering, or any
other
suitable methods. The support plate 208 mechanically stabilizes the
piezoelectric
elements 202a-d and electrically isolates or insulates the piezoelectric
elements
202a-d from other electrical components adjacent the conductive contacts 212a-
d
and/or stray environmental changes. Further, the support plate 208
electrically
isolates the piezoelectric elements 202a-d from each other. Additionally, in
contrast
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to known piezoelectric actuators, the piezoelectric actuator assembly 200 need
not
include a flexible conductive lead coupled to the substrate 206 (e.g., the
conductive
layer) of the piezoelectric elements 202a-d.
[0028] The support plate 208 also includes a plurality of conductive traces or
connecting strip conductors 214a-d (e.g., copper strips) between each of the
conductive contacts 212a-d and, for example, a connector 215 adjacent an edge
216 of the support plate 208 to provide an electrical connection to the
conductive
contacts 212a-d. For example, the conductive traces 214a-d electrically couple
the
piezoelectric actuator assembly 200 to the connector. More specifically, each
of the
conductive traces 214a-d provides a dedicated electrical trace or conductive
strip
between the respective conductive contacts 212a-d and the connector adjacent
the
edge 216. Thus, each of the piezoelectric elements 202a-d has a dedicated
conductive path to electrically couple the piezoelectric elements 202a-d to,
for
example, the processor 102. The connector may be coupled to the conductive
traces 214a-d via a fastener, soldering or any other suitable method(s).
Although
not shown, the support plate 208 may be disposed on or coupled to a base. The
base may be a printed circuit board or other suitable structure.
[0029] As shown in this particular example, the piezoelectric actuator
assembly
200 includes four piezoelectric elements 202a-d directly coupled to four
conductive
contacts 212a-d via the substrate 206 of the piezoelectric elements 202a-d.
Although not shown, in other examples, the piezoelectric actuator assembly 200
may include any number of piezoelectric elements. For example, the
piezoelectric
actuator assembly 200 may include only one piezoelectric element, a recessed
well,
a conductive contact and an electrical trace. Further, in some examples, a
plurality
of piezoelectric actuator assemblies 200 may be coupled to the portable
electronic
device 100.
[0030] FIG. 3A illustrates a cross-sectional view of a portion of the
piezoelectric
actuator assembly 200 taken along line 3A-3A of FIG. 2A when installed with
the
mobile electronic device 100 of FIG. 1. FIG. 3B illustrates a plan view of the
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example shown in FIG. 3A. The piezoelectric actuator assembly 200 may be
disposed within a housing 302 of the electronic device 100 between the housing
302 and the touch-sensitive display (not shown). The housing 302 may be
comprised of a thermoplastic polymer such as polycarbonate, or other suitable
materials such as plastic, fiberglass, and so forth. The piezoelectric
material or
layer 204 of the piezoelectric element 202b is electrically coupled to a
ground via,
for example, a flexible conductive lead 304.
[0031] In some examples, the force sensor 122 may be disposed adjacent the
piezoelectric actuator assembly 200. The force sensor 122 may be a force-
sensitive
resistor, a strain gauge, a piezoelectric or piezoresistive device, a pressure
sensor,
or any other suitable device(s). Force as utilized throughout the
specification,
including the claims, refers to force measurements, estimates, and/or
calculations,
such as pressure, deformation, stress, strain, force density, force-area
relationships, thrust, torque, and other effects that include force or related
quantities. Although not shown, a conductor or flex electrically connects the
force
sensor 122 to the processor 102. Also, although only force sensor 122 is shown
in
the example of FIGS. 3A and 3B, any suitable number of these devices may be
utilized. In some examples, a piezoelectric device, which may be the
piezoelectric
element 202, may be utilized as a force sensor. In some examples, the force
sensor 122 may be integrally coupled with the piezoelectric actuator assembly
200.
[0032] A pad 306 may be disposed on the force sensor 122 such that the pad
306, the force sensor 122, and the piezoelectric actuator assembly 200 are
compressively stacked as shown in FIG. 3B. However, in other examples, the pad
306 may be disposed between the piezoelectric element 202b and the force
sensor
122. The pad 306 may be compressible and may be composed of silicone, a hard
rubber, polyester, polycarbonate and/or any other compressible or compliant
material(s). The pad 306 provides at least minimal shock-absorbing or
buffering
protection for the piezoelectric actuator assembly 200, for example, in the
event
the portable electronic device 100 is dropped, resulting in a more resilient
device
100. Further, the pad 306 does not substantially dampen the force applied to
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the touch-sensitive display 118. Additionally or alternatively, the pad 306
facilitates
the focus of forces exerted on the touch-sensitive display 118 onto the force
sensor
122. The pad 306 transfers forces between the touch-sensitive display 118 and
the
piezoelectric actuator assembly 200, whether the force sensor 122 is above or
below the pad 306 and is advantageously flexible to facilitate provision of
tactile
feedback from the piezoelectric actuator assembly 200 to the touch-sensitive
display 118. The pad 306 may also facilitate greater or more lax tolerances,
such as
mechanical tolerances, in assembling and manufacturing the portable electronic
device 100 and its assemblies because the pad 306 may "absorb" unevenness in
spacing between the force sensor 122, the piezoelectric actuator assembly 200
and/or the touch-sensitive display 118. The force sensor 122 may be optionally
fastened to the pad 306, the piezoelectric actuator assembly 200, the housing
302
or any combination thereof. An adhesive, lamination, or other suitable
measures/processes may be utilized as a fastening mechanism.
[0033] Although not shown, in some examples, absent an external force and/or
absent a charge on the piezoelectric elements 202a-d, one or more of the
piezoelectric elements 202a-d may be slightly bent due to a mechanical pre-
load.
The pre-load results in bent or curved piezoelectric elements 202a-d, such as
a leaf
spring, to facilitate provision of tactile feedback in a direction toward the
touch-
sensitive display 118 and in the opposite direction from the touch-sensitive
display
118. Thus, tactile feedback to the touch-sensitive display 118 may simulate
the
depression and release of a physical key such as a key of a keyboard or a dome
switch. For example, the pre-load of the piezoelectric actuator assembly 200
may
result in a displacement of a center of the piezoelectric element 202b in the
direction toward the housing 302 of between about 50 and 100 microns. Any
other
suitable pre-load or displacement may be utilized. The piezoelectric element
202b
may be further displaced toward the housing 302 (e.g., 50 to 100 microns) when
the touch-sensitive display 118 is depressed by an applied force that moves or
pivots the touch-sensitive display 118 toward the housing 302. In some
examples,
the touch-sensitive display 118 compressively stacks the piezoelectric
actuator
assembly 200, force sensor 122, and pad 306 against a base or housing 302,
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resulting in a pre-load of the piezoelectric actuator assembly 200. In other
examples, the substrate 206 and piezoelectric material 204 may be manufactured
with a slight curve or pre-warp, for example, by curing the piezoelectric
material
204 (e.g., a ceramic material) to the substrate 206 (e.g., a metal shim) with
acrylic
adhesive. The preload facilitates mechanical coupling between the
piezoelectric
actuator assembly 200 and the touch-sensitive display 118. The portable
electronic
device 100 may further include a biasing element disposed in the housing 302
to
bias the touch-sensitive display 118 toward the piezoelectric actuator
assembly 200
and pre-load the piezoelectric actuator assembly 200.
[0034] In operation, the touch-sensitive display 118 may be depressible,
pivotable, and/or movable when force is applied to the touch-sensitive display
118.
For example, the touch-sensitive display 118 may be movable between two or
more
positions by force exerted on the overlay 114 by a user when a user applies a
force
to the touch-screen display to select one or more graphics displayed on the
touch-
screen display. In response to the force on the overlay 114, the touch-
sensitive
display 118 may deflect away from the force, thereby causing the force sensor
122
to detect that the touch-sensitive display 118 has moved. This detection
enables
the portable electronic device 100 to determine that a user has selected one
or
more graphics displayed on the display 112. That is, a user may use his/her
finger
to highlight a graphic, an action which is detected by the overlay 114.
Subsequently, when desiring to select or "click" the highlighted information,
the
user depresses the touch-sensitive display 118 using his/her finger. The
depression
of the touch-sensitive display 118, which is due to, for example, the force of
a
user's finger, is detected by the force sensor 122 and registered as a
selection.
When the touch-sensitive display 118 is depressed, the force sensor 122
generates
a force signal that is received and interpreted by the microprocessor 102. The
force
sensor 122 detects a force imparted to the touch-screen display and generates
the
signal to the processor 102 via a conductive member coupled to the force
sensor
122. The touch may be detected via, for example, a separate detector circuit
which
triggers or causes the processor 102 to activate the piezoelectric actuator
assembly
200. However, in other examples, the example piezoelectric actuator assembly
200
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can be used with a non-movable screen or touch sensitive display (e.g., a
touch
sensitive display that does not move relative to the housing 302).
[0035] The processor 102 then causes the piezoelectric actuator assembly 200
to
activate to provide a tactile feedback (e.g., a vibration) to a user. More
specifically,
the processor 102 generates and provides an actuation signal to the
piezoelectric
actuator assembly 200 to provide tactile feedback to the touch-sensitive
display
118. This tactile feedback allows a user to easily distinguish between a
highlight
action and a selection action when interacting with the portable electronic
device
100. The piezoelectric actuator assembly 200 may be actuated by pressing
anywhere on the touch-sensitive display 118.
[0036] The actuation signal includes duration, magnitude or intensity, and
frequency of feedback information for the piezoelectric actuator assembly 200.
The
actuation signal may be based at least in part on the force or the force
signal
provided by the force sensor 122. The intensity of the feedback may be varied
in
relation to the amount of the applied force. The piezoelectric actuator
assembly 200
may vibrate the touch-sensitive display 118 with respect to the housing 302.
The
touch-sensitive display 118 may vibrate, for example, at one or more
frequencies
between about 100 and 160 Hz. Alternatively, the touch-sensitive display 118
may
vibrate at multiple frequencies, for example, vibrating at 50 Hz for a tenth
of a
second and then vibrating at 100 Hz for a tenth of a second. The piezoelectric
actuator assembly 200 may be controlled to vibrate the touch-sensitive display
118
over various or varied distances. In other examples, the piezoelectric
actuator
assembly 200 may be controlled to vibrate the touch-sensitive display 118
across a
varying frequency sweep, for example, 0 Hz to 150 Hz and back to 0 Hz in three
tenths of a second. Other tactile feedback, such as pulses, clicks, or pops,
may be
provided by the piezoelectric actuator assembly 200.
[0037] The actuation signal causes, for example, the power source 142 to
provide a charge (e.g., a voltage or current) to the piezoelectric actuator
assembly
200. The processor 102 causes the power source 142 to apply a voltage or
current
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to the piezoelectric elements 202a-d via the respective conductive traces 214a-
d to
operate the piezoelectric actuator assembly 200. More specifically, the
voltage or
current is applied to the piezoelectric elements 202a-d via the connector,
which is
electrically coupled to the substrate 206 (e.g., the shim or conductive layer)
of the
piezoelectric elements 202a-d via the conductive contacts 212a-d and the
conductive traces 214a-d. Because each of the piezoelectric elements 202a-d
are
coupled to the connector via dedicated conductive traces 214a-d, each
piezoelectric
element 202a-d may be actuated or analyzed individually.
[0038] When a charge is applied to the piezoelectric actuator assembly 200,
the
substrate 206 bends when the piezoelectric material 204 (e.g., the PZT disk)
contracts diametrically, as a result of buildup of charge at the piezoelectric
material
204 or in response to a force, such as an external force applied to the touch-
sensitive display 118. In particular, contraction of the piezoelectric
material 204
applies a spring-like force, for example, opposing a force externally applied
to the
touch-sensitive display 118. The charge may be adjusted by varying the applied
voltage, e.g., 150 V, or current via the respective conductive traces 214a-d,
thereby controlling the force applied by each of the piezoelectric elements
202a-d.
The charge on the piezoelectric elements 202a-d may be removed by a controlled
discharge current that causes the piezoelectric material 204 to expand,
thereby
decreasing the force exerted by the substrate 206. The charge may
advantageously
be removed over a relatively short period of time to provide tactile feedback
to the
user via the touch-sensitive display 118. The pad 306 provides a bumper or
cushion (e.g., a shock-absorber) for the piezoelectric actuator assembly 200.
[0039] The processor 102 may analyze and/or activate the piezoelectric
elements
202a-d individually, simultaneously, intermittently, or in any delayed pattern
or
alternate combination. For example, the processor 102 may cause the
piezoelectric
element 202a to activate prior to activating the piezoelectric elements 202b-
d.
Thus, a charge or voltage may be applied independently to each of the
piezoelectric
elements 202a-d via the connector and the dedicated conductive traces 214a-d
to
operate or activate one or more of the plurality of piezoelectric elements
202a-d.
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For example, the first piezoelectric element 202a may receive a first charge
(e.g., a
first voltage) that may be different (e.g., greater) than a second charge
(e.g., a
second voltage) provided to the piezoelectric element 202b. In this manner,
the
piezoelectric element 202a may provide a first tactile feedback (e.g., a first
force)
to the user that is different than a second tactile feedback (e.g., a second
force)
provided by the piezoelectric element 202b. In another example, the
piezoelectric
elements 202a and 202c may be activated, and the piezoelectric elements 202b
and 202d may be activated after a predetermined time interval from when the
piezoelectric elements 202a and 202c where activated. Thus, the conductive
contacts 212a-d are separately switchable to independently power any one of
the
plurality of piezoelectric elements 202a-d either independently,
simultaneously,
intermittently, in a delayed pattern, and/or in any other suitable pattern or
combination.
[0040] The arrangement of piezoelectric actuator assembly 200 may be utilized
to provide tactile feedback instead of a vibrator motor, for example, when a
vibration is utilized to notify a user of an incoming phone call instead of a
ring tone
or other audible notification. Thus, a vibrator motor may be eliminated from
the
design of the portable electronic device 100. Further, the actuation signal
may be
varied according to the identity of a caller of a voice communication or
sender of a
voice communication, thereby providing a tailored notification.
[0041] The piezoelectric actuator assembly 200 may emulate the feel of a dome
switch collapse and subsequent release, which is similar to simulating the
press and
release of a key of a keyboard. When a force exerted on the touch sensitive
display
118 meets a first force threshold, an actuation signal may be sent to the
piezoelectric actuator assembly 200 to simulate the collapse of a dome switch.
When the force applied to the touch sensitive display 118 falls below a second
force
threshold, which may be lower than the first force threshold, an actuation
signal
may be sent to the piezoelectric actuator assembly 200 to simulate the release
of a
dome switch. Thus, each time a virtual or soft key is selected by depressing
and
releasing the touch-sensitive display 118 in accordance with force thresholds,
tactile feedback simulating the press and release of a key is provided via the
CA 02751808 2014-09-19
piezoelectric actuator assembly 200. Such feedback simulates typing on a
keyboard
comprised of physical keys. Similar or other feedback may be provided when a
user
selects other displayed options, such as decision windows, e.g., a displayed
delete
or unlock box. Feedback may be provided during the operation of a camera of a
portable electronic device 100. For example, depression of the touch-sensitive
display 118 may act as a shutter to take and record a digital picture, and the
feedback may simulate the feel of a shutter press and release.
[0042] Feedback loops resulting from the triggering of the piezoelectric
actuator
assembly 200 due to forces applied by the piezoelectric actuator assembly 200
may
be addressed in software, for example, by any combination of time delays,
force
thresholds conditions, and so forth.
[0043] The methods described herein may be carried out by software executed,
for example, by the processor 102. Coding of software for carrying out such a
method is within the scope of a person of ordinary skill in the art given the
present
description. A computer-readable medium having computer-readable code may be
executed by at least one processor of the portable electronic device 100 to
perform
the methods described herein.
[0044] The present disclosure may be embodied in other specific forms without
departing from its
essential characteristics. The described embodiments are
to be considered in all respects only as illustrative and not restrictive. The
scope of
the disclosure is, therefore, indicated by the appended claims rather than by
the
foregoing description. All changes that come within the meaning and range of
equivalency of the claims are to be embraced within their scope.
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