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Version: 200705
Piezoelectric multilayer triaxial accelerometer
C. Mangeot1, B. Andersen1, and M. Havránek2
1Noliac Motion, 2Noliac Systems Hejreskovvej 18, Kvistgaard, 3470, Denmark
The accelerometer market
• Conventional systems
– Mostly piezoelectric
– Specific applications for piezoresistive
– Very mature market
– Families of sensors for each environment and performance range
• MEMS
– More recent developments
– Increasing number of applications
Conventional accelerometers
• Market dominated by shear mode sensors
Mass
Housing Piezoelectric element(s)
(ring or plates)
Acceleration direction
Conventional accelerometers
• A few bending type accelerometers
Housing
Bending piezoelectric
element(s)
(ring or plates)
Acceleration direction
Fulcrum
Conventional accelerometers
+ High performance (sensitivity, bandwidth, linearity)
+ Tolerant to environment
+ Large available range
- Complex
- Difficult to miniaturize, heavy
- Costly
Endevco 35A
Brüel Kjaer 4524
Kistler 8690C10
1
10
100
1000
1 10 100 1000
Mass (g)
Acc
eler
atio
n ra
nge
(+/-
G)
Conventional accelerometers
• Market status
MEMS accelerometers
+ Various principles
+ High volume, low cost
+ Light weight
+ Variable performance
- Limited in terms of environment
- Difficult to qualify for aerospace or military applications
- Difficult to customize
Accelerometer development in the Noliac Group
• Cooperation within the group
• Noliac Motion (Denmark)
– Expertise in multilayer piezoelectric elements
• Noliac Ceramics (Czech Republic)
– Expertise in ceramic materials
• Noliac systems (Czech Republic)
– Expertise in piezo transducer development
Ceramic monolithic multilayer triaxial accelerometer (CMMTA)
• 6 regions electrically defined in the same piezoelectric body
• Patent pending
Patent pending
Measurement principle
• X-Y axis
Zones compressed by bending stresses
Zones stretched
by bending stresses Vibration direction
Patent pending
CMMTA
Measurement principle
• X-Y axis: charge movements
Patent pending
CMMTA
Measurement principle
• Z axis
Compressed zone
Stretched zone Vibration
direction
Patent pending
CMMTA
Measurement principle
• Z axis: charge movements
Patent pending
CMMTA
Temperature compensation
• Temperature change: charge movements
Patent pending
CMMTA
SWOT
• Expected advantages
– Low cost (simplicity)
– Compact, lightweight solution
– Temperature compensated
– High sensitivity
– Orthogonality of the axes
– Potential for high temperature application
• Potential disadvantages
– Heterogeneity X-Y vs. Z
– Low stiffness
CMMTA
Prototype design
• Dimensions
– Cross section 2 x 2 mm
– Free length 7 mm
– No seismic mass
– Symmetrical design
• Performance
– Calculated first resonance 15 kHz
– Mass 0,68 grams
CMMTA
Prototype design
• Material
– Noliac Ceramics PCM53
– Soft-doped PZT ceramic
– g31 = -8,4.103 Vm/N
– Tc = 350ºC
• Selected for its temperature stability
• Adaptable design
– High temperature versions possible
– High g versions possible
CMMTA
Prototype design
• Temperature stability
– Impedance at serial resonance
-50%
-40%
-30%
-20%
-10%
0%
10%
20%
30%
-40 -20 0 20 40 60 80 100 120 140 160
Temperature (ºC)
Rel
ativ
e im
peda
nce
at s
eria
l res
onan
ce /
20ºC
(%)
PIC255PCM53Pz27
CMMTA
Prototype design
• Temperature stability
– Sensitivity at serial resonance
CMMTA
-14
-12
-10
-8
-6
-4
-2
0
2
4
-40 -20 0 20 40 60 80 100 120 140 160
Temperature (ºC)
Rel
ativ
e se
nsiti
vity
at s
eria
l res
onan
ce /
20ºC
(dB
)
PIC255PCM53Pz27
Prototypes
• Ceramic multilayer sensor
CMMTA
Prototypes
• Prototype on mount and demonstrator
CMMTA
Performance tests
• X axis
CMMTA
0,75
0,72 0,76
0,69
0,62
0,62
0,63
0,65
0,65
0,66
0,690,71 1,00
0,63 0,86
0,1
1
10
10 100 1000 10000
Frequency (Hz)
Sen
sitiv
ity (p
C/m
.s-2
)
Performance tests
• Y axis
CMMTA
0,660,68
0,66 0,70 0,76
0,75
0,74
0,70 0,73 0,83 0,90 1,17
2,09
4,20
4,06
0,1
1
10
10 100 1000 10000
Frequency (Hz)
Sen
sitiv
ity (p
C/m
.s-2
)
Performance tests
• Z axis
CMMTA
0,87
0,78 0,87
0,81 0,85
0,89
0,87
0,82 0,88 1,09 1,31
2,35
8,56
0,95
0,28
0,1
1
10
10 100 1000 10000
Frequency (Hz)
Sen
sitiv
ity (p
C/m
.s-2
)
Performance tests
• Homogeneity
CMMTA
0,1
1
10
10 100 1000 10000
Frequency (Hz)
Sen
sitiv
ity (p
C/m
.s-2
)
X-Axis
Y-Axis
Z-Axis
Performance
• Homogeneous results for all 3 axes
– Sensitivity 0,6-0,8 pC/m.s-2 for X-Y
– Sensitivity 0,8-1,0 pC/m.s-2 for Z
• Stable response over frequency range
– 10 Hz to 2 kHz
– Low resonance (5 kHz) due to the fixture
CMMTA
Summary
+ High sensitivity
+ Flat and homogeneous response
+ Light weight (0,68g ceramic)
+ Simple construction (low cost)
- Bandwidth limited to 2 kHz for this first prototype
CMMTA
Endevco 35A
Brüel Kjaer 4524
Kistler 8690C10
1
10
100
1000
1 10 100 1000
Mass (g)
Acc
eler
atio
n ra
nge
(+/-
G)
Performance range
• Position on market
Conclusions
• Unique advantages
• Further development
– Packaging
– Integrated electronics
– Range adapted to each measurement
• Develop market potential
– High sensitivity, light weight, temperature stability, compatible with harsh environments
– Aerospace applications
– Instrumentation (f.ex. automotive)
CMMTA
Version: 200705
Thank you for your attention
NOLIAC A/S www.noliac.com Charles Mangeot [email protected]