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									                   ECE5320 Mechatronics
           Assignment#01:Literature Survey on Sensors an
               Topic: Piezoelectric Bimorph Actuator

                               Prepared by:
                              Vipin Varghese
              Dept. of Electrical and Computer Engineering
                          Utah State University
                Email: Tel: (435)881-6159

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           Reference list.
           To probe further.
           Basic definition of bimorph actuators.
           Basic definition of Piezoelectric Bimorph Actuators.
           Bimorph Actuator Configuration.
           Design of Bimorph Actuators.
           Structure Techniques.
           Major applications.
           Basic Working Principle.
           Characteristics of PZT Bimorph.
           A typical sample configuration in application:
               Weaving Machine
               High Dynamic Pressure Regulator
           Major specifications.
           Advantages and Limitations
           Where to buy.

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                     Reference List
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                   To explore further:
           (survival pointers of web references

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                     What are Bimorph Actuators?
           A bimorph actuator is composed of
           two thin panels of ceramic elements
           bonded together with a flexible metallic
           panel as it's central electrode. By wiring
           these two elements in such a way as to
           make one elongate and the other
           contract by applying voltage, inflection
           deviation occurs conforming to the
           waveform of the applied voltage.

           Bimorphs are operated in d31 mode.
           Courtesy :

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       What are Piezoelectric Bimorph Actuators?
           It can be described as a sandwich-type actuator in which two layers
           of a piezoelectric material are laminated onto one surface of a
           supporting beam or plate. The two piezoelectric layers are generally
           poled in the same direction, typically in the direction normal to the
           supporting beam/plate. When opposing electric fields are applied to
           the two piezoelectric layers, their corresponding dimensional
           changes are of the opposite character, which gives rise to bending of
           the beam.

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            PZT Bimorph Actuator Configuration
             Two Electrode Bimorph (Serial Bimorph):
           Here one of the two ceramic plates is always
           operated opposite to the direction of polarization.
           To avoid depolarization, the maximum electric field
           is limited to few hundred volts per millimeter. These
           type of actuator is widely used in accelerometers and
           force sensors.

             Three Electrode Bimorph (Parallel Bimorph):
           Here the two piezoelectric plates are of the same
           polarization directions and the actuator is driven by
           applying electrical field between surface electrodes
           and the bonding layer

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            Design of PZT Bimorph Actuators
           Cantilever Design: As can be seen from
           the figure, the cantilever design results in an
           uniform upward and downward motion.
           This design can be used in applications
           involving high speed micro fans for cooling
           or nano-precision positioning.

           S-Beam Design: In this design, there
           exists different motions at different areas of
           the actuator upon proper voltage. This kind
           of design can be used in applications like
           bimorph mirrors where depending on the
           voltage applied, the deflection changes at
           various points leading to optical changes

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           Bimorph Structure Techniques
           Apart from bimorph techniques in PZT actuator ,other forms are also
           employed such as:

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                  Major Applications
           Needle control in textile weaving.
           Braille machines.
           Opening/closing valves.
           Small volume pumping.
           Switching applications-touch switches.
           Cooling devices.
           Fiber optical switches.
           High dynamic pressure regulator.
           Hearing Aids.

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                   Basic Working Principle
           Two PZT thin films are stacked co-axially on both sides of a
           thin elastic bronze piece, and an outer ring and an inner ring
           are separately installed and are firmly fixed on outer and
           inner diameter of the elastic piece by two ring covers.

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             Basic Working Principle (cont.)
           When a proper excitation voltage is applied on it, the
           upper PZT thin film expands vertically and contracts
           horizontally, the lower PZT contracts vertically and
           expands horizontally. This establishes the bimorph
           bending, the effect of which produces the deformation.

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           Characteristics of PZT Bimorph
            No load displacement: The
            displacement caused when no
            load is applied.

            Elastic Load displacement:
            The displacement caused when
            an elastic load is applied.

            Static Load displacement:
            The displacement caused when
            an static load is applied.

            Blocked Load displacement:
             The displacement caused when
            an static load is applied.

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           Characteristics of PZT Bimorph (cont)

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Sample configuration in application: Weaving
           The internal 3D design of the module used in SITEX ® M -
           Textile machine used for circular knitting ,with PZT Bimorph
           Actuator is shown below.


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Sample configuration in application: Weaving
    SITEX M - Textile machine module :
    The picture shows the actual module used
    in the textile weaving machine. Each of
    these modules uses the PZT bimorph
    actuator configuration shown in the earlier

    SITEX M Circular knitting machines :
    The figure shows the Circular knitting
    machine with each module in place to
    control the needles in the proper direction
    by use of PZT bimorph actuator.


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           High - dynamic pressure regulator
             The figure shows the pressure regulator constructed using
             PZT bimorph actuator. Depending upon the flap position
             and the applied voltage to the actuator bending
             (displacement) takes place.


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                        Major specifications
           For bimorph actuator specifications, we need to take into
           account the following parameters:
           Performance Characteristics:
                Maximum Displacement (mm/V)
                Blocked Force (N)
                Maximum Voltage (volts)
                Stiffness (N/mm)
                Resonance Frequency (Hz)
                Capacitance (F)
                Response Time (ms)

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                     Major specifications (cont)
           Physical Specifications
              •   Length (mm)
              •   Diameter/Height (mm)
              •   Thickness (mm)
              •   Mass (g)

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           Major specifications (cont)

                   h = thickness
                   Lt = total length
                   L = free length
                   w = width
                   z = deflection.

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                      Major specifications(cont)
           For a parallel PZT bimorph actuator the specification can be given as:

                  Maximum Displacement = 9 * 10 10 L2
                                                        mm /V

                  Bending = 7 * 10 11 3 mm / N

                  Resonant Frequency = 400 * 2 Hz

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           Major specifications(cont)
           Charge Output =           8 * 10 8 2 (C / N )
                                              8   Lt w
           Capacitance =             8 * 10             (F )
           Voltage Output =          10  2 *        (V / N )
                                              h Lt w

           Blocking Force (stiffness) =      10 * (N /V )

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                    Major specifications (cont)
           Here the constants for each of the formula has been calculated
           with respect to a specific piezoelectric substance been used.

           There are other factors to be considered too along with this
           specifications like:

           Young’s Modulus
           Operating Temperature
           Storage Temperature
           Mechanical quality factor,etc.

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           Unlimited Resolution : A bimorph piezoelectric actuator can produce
           extremely fine position changes down to the sub nanometer range. The
           smallest changes in operating voltage are converted into smooth
           movements. Motion is not influenced by stiction/friction or threshold
           Large Force Generation: Piezoelectric bimorph actuators can
           generate a force of several 10,000 N. It can also bear loads up to several
           tons and position within a range of more than 100 μm with sub-
           nanometer resolution.
           No Magnetic Fields: Piezoelectric bimorph actuators are especially
           well-suited for applications where magnetic fields cannot be tolerated.
           Low Power Consumption: The piezoelectric effect directly converts
           electrical energy into motion, absorbing electrical energy during
           movement only. Static operation, even holding heavy loads, does not
           consume power.

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                           Advantages (cont)
           No Wear and Tear: A piezoelectric actuator has neither gears nor
           rotating shafts. Its displacement is based on pure solid-state effects and
           exhibits no wear and tear.

           Vacuum and Clean-Room Compatible: Bimorph PZT actuators
           employ ceramic elements that do not need any lubricants and exhibit no
           wear or abrasion. This makes them clean-room compatible and ideally
           suited for ultra-high-vacuum applications.

           Operation at Cryogenic Temperatures: The piezoelectric effect is
           based on electric fields and functions down to almost zero Kelvin, albeit
           at reduced specifications.

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           There are three major limitations to the bimorph piezoelectric actuator.

                  The shaping of the electrodes and laminate.
                  The bandwidth.
                  Blocking force.

               The Shaping of the electrodes and laminate can be in several forms
               • C-shape
               • Bar, rectangular
               • Disk
              Each shape will have a different response time and force when a specific
              voltage is applied.

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                          Limitations (cont)
           Shaping can also effect bandwidth.
           A larger laminar area will cause the bandwidth to drop. As the
           bandwidth drops the response time also drops.
           This could either be an advantage or a disadvantage depending on the
           Blocking force is also determined by the deflection and compliance of
           the two laminar surfaces.
           This ends up being inversely proportional to the length which indicates
           longer the lamina the less force it is able to exert.

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                              Where to Buy?
           There are many companies around which supply these kind of actuators
           depending upon design and demand.

           Some of the companies and the links (Click the logo) are:

                                                      FUJI & CO


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