2011 12 e416dc68 by 126MSk0

VIEWS: 14 PAGES: 9

									 Measurement of Mechanical Properties for
Elastomers Using Piezoelectric Tactile Sensor



              Name: Kun-Feng Lu(呂昆峰)
         Advisor: Cheng-Hsin Chuang (莊承鑫)


Department of Mechanical Engineering & Institute of Nanotechnology,
          Southern Taiwan University, Tainan Taiwan
                      Date :2011-12-22
                                                                      1
                       Outline

•   Motivation
•   The Concept of Differentiation Material Property
•   Numerical Simulation
•   Sensor Fabrication
•   Experiment Set-up and Measurement System
•   Results and Discussion
•   Conclusions



                                                       2
     The Concept of Differentiation Material Property

     Normal Force
                                          V1
                                               V1/V2 is large for
                                               Hard Material



                              E2 E1 E2   V2
                    Contact

                                 V1 V2

     E2 E1 E2                             V1   V1/V2 is small for
                                               Soft Material
                                          V2

         E1  E2              E2 E1 E2
  E : Inner structure
     1

E : Outer package layer
 2                               V1 V2
                                                             3
   Numerical Simulation
                            Uniform Load of 1N
Inner Structure
                                                                        The specifications of tactile sensor
Package Layer
    (Top)                                                                                          Length        Width   Thickness
                                                                         Materials
                                                                                                    (mm)         (mm)      (mm)
Package Layer
  (Bottom)                                                             Inner Structure               2             2        3
                                                                     Package Layer (Top)             10           10        4
PVDF Film
                                                                   Package Layer (Bottom)            10           10        1
PI Film (Top )
                                                                         PVDF Film                   9             9      28×10-3
PI Film (Bottom)
                                                                        PI Film (Top)                9             9      50×10-3
Elastomer                                                             PI Film (Bottom)               9             9      50×10-3
                                                                         Elastomer                   15           15        10
    The tactile sensor model design of FEM
                          Material Properties for Numerical Simulation
            Property              Units     PVDF        PI Film   Inner Structure        Package    Elastomer
            Density               kg/m³      1780        1353          1570               1083            1030
            Young’ s modulus       MPa       3000        2510          5.45                 1       0.125~5000
                       The sensor imitates the size of human finger, about 10 ×
            Poisson’s ratio       -     0.35     0.34       0.48        0.48                              0.40
                       10 × 5 mm3           -10
            Dielectric constant   Farad/m   11ˣ10
            d211,d233             m/Volt    23ˣ10-12
            d222                  m/Volt    -33ˣ10-12
                                                                                                                           4
       Numerical Simulation
       -Concept Validation
                                                                                                                      Elastomer : E=5GPa
                                                                                        1.6                           Package : E=1MPa
                                                                                                                      Microstructure : E=5.45MPa
                                                                                                    0.35


                                                                                        1.5


                                                                                                     0.3
                                                                                                                        V1
                                                                                                               0.22 (V) Low sensitivity




                                                   Electric Potential Ratio
                                                                       Electric Potential [V] [V]
                                  Extracted Path                                        1.4




                                                                           Output Voltage
                                                                                                                  V2 0.34 (V)



                                                          V1/V2 [V]
                                                                                                    0.25
                                                                                        1.3
                                                                                                                         V1
                                                                                                                             1.51 (Ratio)
       PVDF Film                                                                        1.2
                                                                                                     0.2        Exhibit aV2
                                                                                                                         non-linear uptrend
                                                                                                                    Outer                Inner                  Outer
                                                                                                                Package Layer          Structure            Package Layer
                                                                                          0.15
                                                                                        1.1
                                                                                                                                                      Elastomer : E=125 kPa ~ 5 GPa
   Y(2)                                                                                                                                               Package : E=1 MPa
                                                                                                                                                      Inner Structure : E= 5.45 MPa

                                                                                             1
                                                                                               0.1
                                                                                            1E+005                1E+006        1E+007             1E+008        1E+009           1E+010
                                                                                                           0          0.002            0.004            0.006             0.008
Z(3)    X(1)                                                                                                               Young's Modulus [Pa]
                                                                                                                                    Distance [m]
           The contour of electric potential                                                               TheDifferent Young’s modulus of
                                                                                                              profile of electric potential along
                on the PVDF surface                                                                                 simulation result
                                                                                                                    an extracted path             5
       Sensor Fabrication
(i)    FPC thin film                (vii) Bonding                        Cu               PI          PR          Mask

                                                                         Ag               PVDF        PDMS        PMMA

(ii)   Coat PR →Exposure →Develop                                       Silicone rubber          Adhesion layer
                                    (viii) PMMA master by machining



                                    (ix)   Inner structure molding by
(iii) Wet etching electrode
                                           silicone rubber




                                    (x)    Bonding silicone rubber
(iv) Strip PR                              structure upon electrodes




(v)    PVDF thin film

                                    (xi)   Package with PDMS



(vi) Strip Ag layer on PVDF thin
     film surface
                                                                        Photograph of flexible tactile sensor
                                                                             with structural electrode                   6
Experiment Set-up
-Measurement System of Mechanical Properties of Elastomers
      Linear Power         Digital Phosphor                  Computer
        Amplifier            Oscilloscope


                                      Shaker
 Function Generator


                         Signal
                       Conditioner                     Charge Amplifier


 Single-Axis DC
 Motor Controller      3-Axis Stage
                                                                Force Sensor
                  PMMA
             (15mm ×15mm×2mm)                                   DUT
                                                                Tactile Sensor
               Photograph of elastomers measurement device
                                                                                 7
  Results and Discussion
  -Measuring Mechanical Properties of Elastomers
                                                                 2.2
                                                                0.04
                                                                                   Dow Corning 3120 RTV Rubber
                                                                               Device Under Test : Sylgard 184 Silicone Elastomer
                                                                                   Sylgard 160 Silicone Elastomer
                                                                                           Output Signal of Inner Structure
       Uniform Load                                               2
                                                                                   Sylgard 184 Silicone Elastomer
                                                                                           Output Signal of Outer Structure
                                                                                   Sylgard 170 Silicone Elastomer
                                                                                   Sylgard 186 Silicone Elastomer
                                                                0.02




                                          Sensor Output Ratio
                                                                                   Dow Corning 3-4207 Dielectric Tough Gel
                                                                 1.8               Dow Corning 3-4220 Dielectric Firm Gel




                                        ElectricV1/V2 [V] [V]
                                                 Potential
                                                                          ◎ Exhibit a non-linear uptrend
                                                                1.60




                                                                 1.4


                                                                -0.02
                                                                                              Outer Package Layer
                                                                1.2

                                                                          Inner Structure
Elastomer                                                       -0.04
                                                                   1
                                                                     00          20
                                                                                 0.4           40
                                                                                               0.8           60
                                                                                                             1.2           80
                                                                                                                           1.6      100
                                                                                                                                     2
                         Outer Package Layer                                           Hardness [Shore 00]
                Inner Structure                                                             Time [s]
 The illustration of measurement of                                        Estimating electric potential ratio for
                                                                           Grapher of capturing oscilloscope
 mechanical properties for elastomers                                                of elastomer samples
                                                                                all the output signal
                                                                                                                   8
Conclusions

• We have proposed a simple measurement method for determination of
  the hardness of elastomers based on tactile sensor with structural
  electrodes. With a periodic loading, the voltage ratio obtained from
  hard inner structure and soft packaging layer can be regarded as an
  indicator of hardness for contacted object.



• The tactile sensor can provide the information of hardness to in-situ
  feedback control as grasping object for robotic, and the in-vivo
  measurement of tissue for the minimally invasive surgery.




                                                                          9

								
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