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 cm@noliac.com