Download Wireless drive of a piezoelectric plate by capacitorlike structure in

Wireless drive of a piezoelectric plate by capacitorlike structure in electric
resonance with an inductor
Satyanarayan Bhuyan, Junhui Hu, and Chang Qing Sun
Citation: J. Appl. Phys. 103, 094915 (2008); doi: 10.1063/1.2908183
View online: http://dx.doi.org/10.1063/1.2908183
View Table of Contents: http://jap.aip.org/resource/1/JAPIAU/v103/i9
Published by the American Institute of Physics.
Related Articles
Polarization relaxation kinetics in ultrathin ferroelectric capacitors
Appl. Phys. Lett. 102, 092901 (2013)
Magnetic field tunable acoustic resonator with ferromagnetic-ferroelectric layered structure
J. Appl. Phys. 113, 17C704 (2013)
High power terahertz radiation source based on electron beam wakefields
Rev. Sci. Instrum. 84, 022706 (2013)
Comparative study of tip cross-sections for efficient galloping energy harvesting
Appl. Phys. Lett. 102, 064105 (2013)
Diagonal control design for atomic force microscope piezoelectric tube nanopositioners
Rev. Sci. Instrum. 84, 023705 (2013)
Additional information on J. Appl. Phys.
Journal Homepage: http://jap.aip.org/
Journal Information: http://jap.aip.org/about/about_the_journal
Top downloads: http://jap.aip.org/features/most_downloaded
Information for Authors: http://jap.aip.org/authors
Downloaded 07 Mar 2013 to 202.6.242.69. Redistribution subject to AIP license or copyright; see http://jap.aip.org/about/rights_and_permissions
JOURNAL OF APPLIED PHYSICS 103, 094915 共2008兲
Wireless drive of a piezoelectric plate by capacitorlike structure in electric
resonance with an inductor
Satyanarayan Bhuyan, Junhui Hu,a兲 and Chang Qing Sun
School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798,
Singapore
共Received 13 December 2007; accepted 14 February 2008; published online 9 May 2008兲
A new technique of wirelessly transmitting electric energy to piezoelectric components is explored.
In the design, an ac electric field is focused to a piezoelectric plate placed between plate-shaped live
and needle ground electrodes which form a capacitorlike electric field generator in series with an
inductor. The transmission of electric energy is enhanced when the capacitorlike electric field
generator and inductor are in electric resonance. Experimentally it has been found that the real
output power delivered to the piezoelectric plate depends on the electrode pattern, vibration mode,
and electrical load of the piezoelectric component and the electric field focused by the needle ground
and live electrodes. When the operating frequency is close to mechanical resonance frequency of the
piezoelectric plate operating in the thickness vibration mode, a maximum output power of 0.264 W
and energy conversion efficiency of 1.02% have been achieved with an input voltage 150 Vrms and
10 mm electrode separation. © 2008 American Institute of Physics. 关DOI: 10.1063/1.2908183兴
I. INTRODUCTION
Piezoelectric actuators are devices capable of converting
electric energy into mechanical displacements. They have
various applications due to their compact size, high precision
positioning, low power consumption, high output force, and
high-power density properties. There has been remarkably
rising interest in the applications of piezoelectric actuators
such as precision positioning,1–10 particle manipulations,11–13
vibration control,14,15 etc.16,17 In the existing driving circuits,
electric energy is applied to the actuators via lead wires soldered on the electrodes of piezoelectric components. However, this method of applying electric energy has some limitations. At large vibration and high input voltage, the
soldered points melt and this causes the breakdown of actuators. The lead wires also hinder the applications of piezoelectric actuators in rotary mechanisms. Therefore, there is a
need to investigate wireless electric energy transmission to
piezoelectric actuators. Earlier, a new technique of wireless
electric energy transmission was proposed by the author.18 In
the technique, ac electric field from a plate-shaped live electrode is focused to a piezoelectric plate by using a needle
ground electrode. But the output power of the driven piezoelectric plate is not high enough. In order to drive a highpower piezoelectric plate wirelessly by an electromagnetic
wave and widen the application range of piezoelectric actuators, the wireless drive of piezoelectric plates needs to be
investigated further.
The wireless drive of piezoelectric plates is experimentally investigated by using the electric resonance of a capacitorlike electric field generator and an inductor in series. In
the capacitorlike electric field generator, the ac electric field
is focused to a needle ground electrode from a plate-shaped
live electrode through a piezoelectric plate placed in between
a兲
Author to whom correspondence should be addressed. Electronic mail:
[email protected].
0021-8979/2008/103共9兲/094915/5/$23.00
them. The technique enables a relatively large output power
delivered to the piezoelectric plate. The effects of operating
frequency, electric load, electrode pattern, vibration mode,
and position of the piezoelectric plate on the real output
power delivered to the electric load are studied in order to
optimize the electric energy transmission to piezoelectric
plates.
II. EXPERIMENTAL SETUP, CONDITIONS, AND
OPERATING MECHANISM
To transmit a relatively large electric energy to piezoelectric components, a capacitorlike electric field generator
in series with an inductor is used as shown in Fig. 1共a兲. With
a brass plate-shaped live electrode, a stainless steel needle
ground electrode is used to form the capacitorlike electric
field generator. In the electric field generator, the ac electric
field is focused to a needle ground electrode from a plateshaped live electrode through a piezoelectric plate placed in
between them. When the electric field generator and inductor
are in electric resonance, the transmission of electric energy
is enhanced because of the large voltage across the capacitorlike structure. Two types of piezoelectric plates are used in
the experiment. The upper and lower surfaces of the piezoelectric plates are covered with silver metal electrodes. Figure 1共b兲 shows the configuration of plate A which has whole
electrode on its top and bottom surfaces and only has output
section P. Figure 1共c兲 shows the configuration of the plate B,
which has two electrically separated sections P and Q. A
resistance load is connected across the two electrodes of section P for measuring the real power which section P delivers.
The experiments are performed under the following conditions. All the experimental piezoelectric plates are made of
same ceramic material lead zirconate titanate 共PZT兲 with a
size of 30⫻ 8 ⫻ 2 mm3, and are poled along the thickness
direction. The electrode length ratio of section Q to P of
plates A and B is 0:1 and 5:1, respectively. The live electrode
103, 094915-1
© 2008 American Institute of Physics
Downloaded 07 Mar 2013 to 202.6.242.69. Redistribution subject to AIP license or copyright; see http://jap.aip.org/about/rights_and_permissions
094915-2
J. Appl. Phys. 103, 094915 共2008兲
Bhuyan, Hu, and Sun
FIG. 1. 共Color online兲 共a兲 Experimental setup to drive
piezoelectric components wirelessly, 共b兲 configuration
of plate A, and 共c兲 configuration of plate B.
area is 30⫻ 30 cm2. The ground electrode is a metal needle
whose tip is assumed to have zero area. The medium between the live and ground electrodes is air. The inductances
共L兲 are 1.50 and 1.46 mH for piezoelectric plates A and B,
respectively, and thus the electric field generator and inductor are in resonance. To prevent the shift of resonance frequency due to heat generation, the temperature rise of the
piezoelectric plate is kept below 10 ° C in the experiment.
Unless otherwise specified, the piezoelectric plate is placed
equidistantly in between the live and needle ground electrodes positioned perpendicular to each other, the ac input
voltage applied to the series of electric field generator and
inductor is 150 Vrms, distance between the live and needle
ground electrode is 10 mm, and plates operate in the thickness vibration mode. Table I shows the measured resonance
frequencies and equivalent circuit parameters from section P
of plates A and B by an impedance analyzer 共HP4194A兲.
When the capacitorlike electric field generator and inductor are in electric resonance, the current flowing through
the electric field generator is very large. Thus at resonance, a
relatively large ac electric field can be focused to a needle
ground electrode from the plate-shaped live electrode
through a piezoelectric plate placed in between them. The
piezoelectric plate is polarized in the thickness direction.
When an ac electric field penetrates the piezoelectric plate, a
mechanical vibration can be stimulated in the piezoelectric
plate by the converse piezoelectric effect. When the frequency of ac electric field is close to mechanical resonance
frequency of the piezoelectric plate, a mechanical resonance
can be excited in the plate. This mechanical resonance can
generate a relatively large voltage across the output electrodes due to the piezoelectric effect.
III. EXPERIMENTAL RESULTS AND DISCUSSION
Figures 2共a兲 and 2共b兲 show the frequency characteristics
of the output power of both piezoelectric plates A and B
operating in the thickness vibration mode, placed inside the
capacitorlike electric field generator. Figure 2共a兲 represents
the result when the electric field generator is electrically
resonant with the inductor. Figure 2共b兲 represents the result
without the inductor. It is observed that at the resonance
frequencies of 772 and 782 kHz of plates A and B, respectively, a maximum output power is achieved. When the frequency of ac electric field is close to mechanical resonance
frequency of the plate, a relatively large vibration can be
excited in the plate by the converse piezoelectric effect. This
mechanical resonance generates a relatively large voltage at
the section P by the piezoelectric effect. It is also seen that
when the electric field generator and inductor are in electrical
resonance the output power of the piezoelectric plate is significantly higher than that of the electric field generator with-
TABLE I. Parameters of the section P of piezoelectric plates.
Piezoelectric
plates
Resonance
frequency
f r 共kHz兲
Equivalent
resistance
Rm 共⍀兲
Equivalent
inductance
Lm 共mH兲
Equivalent
capacitance
Cm 共pF兲
Clamped
capacitance
Cd 共pF兲
Plate A
Plate Ba
772
782
42
286
16.3
117
2.52
0.368
712.2
202.8
a
Section Q is open circuit.
Downloaded 07 Mar 2013 to 202.6.242.69. Redistribution subject to AIP license or copyright; see http://jap.aip.org/about/rights_and_permissions
094915-3
Bhuyan, Hu, and Sun
J. Appl. Phys. 103, 094915 共2008兲
FIG. 3. 共Color online兲 Dependence of the output power on the electrical
load and electrode length ratio at resonance frequency of the thickness vibration mode.
FIG. 2. 共Color online兲 Frequency characteristics of the output power of
piezoelectric plates A and B at the optimum load resistance for 共a兲 electric
field generator with inductor and 共b兲 electric field generator without an
inductor.
out an inductor. When the electric field generator is in series
electric resonance with an inductor, the voltage across the
capacitorlike structure is eight times greater than the ac
source voltage. Thus at resonance, a relatively large amount
of ac electric field can be focused to the needle ground electrode and hence a relatively large electric energy can be
transmitted to the piezoelectric plate placed in between the
live and needle ground electrodes. Therefore, for a given
input ac voltage Vin, the output power is larger for an electric
field generator which is in electric resonance with an inductor.
Figure 3 shows the dependence of output power at resonance on the electrical load for the piezoelectric plates, operating in the thickness vibration mode. It is seen that the
output power at resonance reaches the maximum at an optimum load resistance. For plate B whose electrode length
ratio of Q to P is 5:1, the output power at resonance reaches
the maximum at 1365 ⍀ and the maximum output power is
0.264 W. The equivalent circuit of the plates is shown in Fig.
4, which can be used to explain these results. When the load
resistance RL is not much larger than 1 / 共␻Cd兲, the output
voltage V0 increases with RL for a given voltage Vs. When RL
is much larger than 1 / 共␻Cd兲, the load branch can be regarded as open circuit. So, V0 is constant and the output
power 共V20 / RL兲 decreases as the electrical load RL
increases.19
Figure 5 shows a comparison of the maximum output
power between the plates operating in various resonance
modes for different electrode length ratio of Q to P. The
maximum output power is measured when the electric field
generator is in resonance with an inductor for different resonant modes. The optimum load of each measuring point depends on the resonance mode and electrode length ratio. It is
seen that a high output power is achieved for large electrode
length ratio of Q to P, and the maximum output power at
resonance of plate B 共electrode length ratio Q: P = 5:1兲 is
higher than that of plate A 共electrode length ratio Q: P
= 0 : 1兲. When the electrode length ratio of Q to P increases,
FIG. 4. Equivalent circuit of the piezoelectric plate. Vs is the source voltage,
V0 is the output voltage, Cd is the clamped capacitance, and Lm, Cm, and Rm
are the equivalent inductance, capacitance, and mechanical resistance,
respectively.
Downloaded 07 Mar 2013 to 202.6.242.69. Redistribution subject to AIP license or copyright; see http://jap.aip.org/about/rights_and_permissions
094915-4
Bhuyan, Hu, and Sun
FIG. 5. 共Color online兲 Effect of the electrode length ratio on the maximum
output power of plates operating in different resonance modes when the
electric field generator is in electric resonance with the inductor. The maximum power is for frequency and electrical load.
the clamped capacitance 共Cd兲 of section P decreases. Then,
1 / 共␻Cd兲 increases with the decrease of Cd for a given frequency. This increases the output voltage V0. When the
change of RL is not very large, the output power increases as
the output voltage V0 increases. Hence the output power at
resonance of plate B is higher than that of the plate A.
Figure 6 shows the effect of vibration modes on the output power at the optimum load and resonance frequency. The
output power is measured for plate B when the electric field
generator is in electric resonance with an inductor. It is seen
that the output power of the piezoelectric plate operating in
the thickness vibration mode is significantly higher than that
of the plate operating in the width and length extensional
vibration modes. Thus, the vibration mode has an effect on
the output power of the piezoelectric plate.
Figure 7 shows the dependence of the output power at
resonance on the distance between the lower surface of piezoelectric plate and needle ground. The output power is
measured for plates A and B operating in the thickness vibration mode, when the electric field generator and an inductor are in electric resonance. It is seen that the maximum
output power increases with the decrease in the distance between the piezoelectric plate and needle ground for a given
input ac voltage. This is because the electric field at the
piezoelectric plate increases as the plate is moved towards
the needle ground.
Figure 8共a兲 shows frequency characteristic of the energy
conversion efficiency 共the ratio of the real power delivered to
the electrical load resistor to real power supplied by the ac
input voltage source兲 at the optimum electrical load resis-
J. Appl. Phys. 103, 094915 共2008兲
FIG. 6. Effect of vibration modes on the output power of plate B when the
electric field generator is in electric resonance with the inductor.
tance of piezoelectric plates A and B, operating in the thickness vibration mode. It is seen that when the electric field
generator and inductor are in electric resonance an efficiency
of 1.02% has been achieved for plate B at the resonance
frequency of 782 kHz and electric load resistance of 1365 ⍀
which is lower than that of the efficiency of 1.18% achieved
FIG. 7. 共Color online兲 Dependence of the maximum output power on the
distance between the piezoelectric plate and needle ground electrode. The
maximum power is for frequency and electrical load.
Downloaded 07 Mar 2013 to 202.6.242.69. Redistribution subject to AIP license or copyright; see http://jap.aip.org/about/rights_and_permissions
094915-5
J. Appl. Phys. 103, 094915 共2008兲
Bhuyan, Hu, and Sun
IV. CONCLUSIONS
In this work, an improved method of wireless drive of a
piezoelectric plate is explored by using the electric resonance
of a capacitorlike electric field generator and an inductor in
series. In the capacitorlike electric field generator, the ac
electric field is focused to a needle ground electrode from a
plate-shaped live electrode through a piezoelectric plate
placed in between them. When the capacitorlike electric field
generator and inductor are in electric resonance, the wireless
electric energy transmission can be enhanced. The technique
enables a relatively large output power delivered to the piezoelectric plate. The output power attains the maximum at
the resonance of piezoelectric plate and the plate with properly divided electrode has a larger output power than the one
with whole electrode. The real output power achieved by the
piezoelectric plate depends on the electrode pattern, vibration mode, and electrical load of the piezoelectric component, and the electric field focused by the needle ground and
live electrodes. At resonance frequency of 782 kHz, a maximum output power of 0.264 W and energy conversion efficiency of 1.02% have been achieved by the piezoelectric
plate operating in the thickness vibration mode with a needle
ground electrode, input voltage of 150 Vrms, and 10 mm
electrode separation. Methods of increasing the transmission
power and energy conversion efficiency will be investigated
further theoretically and experimentally.
W. G. Cady, Piezoelectricity 共McGraw-Hill, New York, 1946兲, p. 45.
T. Ikeda, Fundamentals of Piezoelectric Materials Science 共Ohm Publishing Co., Tokyo, 1984兲, p. 209.
3
A. Kumada, Jpn. J. Appl. Phys., Suppl. 24 739 共1985兲.
4
K. Nakamura, M. Kurosawa, and S. Ueha, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 40, 402 共1993兲.
5
S. Ueha and Y. Tomikawa, Ultrasonic Motors 共Oxford University Press,
Oxford, 1993兲, p. 1.
6
S. Lin, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 44, 1189 共1997兲.
7
K. Yao, B. Koc, and K. Uchino, IEEE Trans. Ultrason. Ferroelectr. Freq.
Control 48, 1066 共2001兲.
8
Y. Chen, T. Zhou, Q. Zhang, X. Cheng, and S. Chen, Ultrasonics 39, 667
共2002兲.
9
J. R. Friend, J. Satonobu, K. Nakamura, S. Ueha, and D. S. Stutts, IEEE
Trans. Ultrason. Ferroelectr. Freq. Control 50, 179 共2003兲.
10
J. L. Pons, Emerging Actuator Technologies 共Wiley, Chichester, 2005兲, p.
46.
11
W. T. Coakley, D. W. Bardsley, and M. A. Grundly, J. Chem. Technol.
Biotechnol. 44, 42 共1989兲.
12
J. Wu, J. Acoust. Soc. Am. 89, 2140 共1991兲.
13
S. Gupta and D. L. Feke, Ultrasonics 35, 131 共1997兲.
14
G. Gibbs and C. Fuller, J. Acoust. Soc. Am. 92, 3221 共1992兲.
15
J. S. Yang and X. Zhang, Int. J. Appl. Electromagn. Mech. 16, 29 共2002兲.
16
D. L. Miller, W. L. Nyborg, and C. C. Whitcomb, Science 205, 505
共1979兲.
17
P. Muralt, A. Kholkin, M. Kohli, and T. Maeder, Sens. Actuators, A 53,
398 共1996兲.
18
S. Bhuyan and J. H. Hu, Appl. Phys. Lett. 91, 26, 共2007兲.
19
J. H. Hu, H. L. Li, H. L. W. Chan, and C. L. Choy, Sens. Actuators, A 88,
79 共2001兲.
1
2
FIG. 8. 共Color online兲 共a兲 Frequency dependence of energy conversion efficiency at the optimum electrical load of piezoelectric plates and 共b兲 dependence of efficiency on the electrical load when the electric field generator is
in electric resonance with the inductor.
without inductor. Due to the internal resistance of the inductor, the efficiency achieved with inductor is less than that
achieved without inductor. Figure 8共b兲 shows the dependence of efficiency on the electrical load, when the electric
field generator and inductor are in electric resonance for piezoelectric plate B operating in the thickness vibration mode.
It is seen that the energy conversion efficiency depends on
the electrical load and a maximum efficiency of 1.12% is
achieved for plate B at the resonance frequency of 782 kHz
and electric load resistance of 1450 ⍀.
Downloaded 07 Mar 2013 to 202.6.242.69. Redistribution subject to AIP license or copyright; see http://jap.aip.org/about/rights_and_permissions