Research Introduction
Lab of Smart Structures
精密机械与精密仪器系 Precision Machinery and Precision Instrumentation
Contents
1. Smart piezoelectric actuators
2. Piezoelectric transformers
3. Precision control of piezoelectric actuators
4. Energy harvesting
5.Other researches
精密机械与精密仪器系 Precision Machinery and Precision Instrumentation
1. Small Piezoelectric Actuators
a. Fiber torsional actuator
b. Tube actuators and its composite
a. Discovery of torsional actuation
discovery
Experimental measurement
Static response of voltage
Resonance image of the prototype actuator’s free end.
Test setup
Dynamic response of frequency
C. L. Pan, Z. H. Feng, et al., "Small torsional piezoelectric fiber
actuators with helical electrodes,“ Applied Physics Letters, vol. 92, p. 012923, 2008.
Application—Impact piezoelectric motor
Rotor
Piezoelectric fiber motor
Bulk piezo cylinder moter
Impact piezoelectric motor
Impact response of the fiber motor
Impact response of the bulk motor
W. X. Han, Z. H. Feng, et al., "An impact rotary motor based on a fiber torsional piezoelectric actuator,"
Review of Scientific Instruments, vol. 80, p. 014701, 2009.
Impact piezoelectric motor
Miniature optical scanning mirror
For a 15 mm length fiber:
Torsional vibration, 0-30 kHz bandwidth, 0.2° amplitude
Longitudinal vibration, 0-50 kHz bandwidth, 1 μm amplitude
Designed structure
It consists of cantilevers, hinges, and mirror.
Principle of 2-D scanning
Fabrication and test
Results
Measured vertical frequency response of the prototype scanners.
C. L. Pan, Z. H. Feng, et al., "Miniature orthogonal optical scanning mirror excited by torsional piezoelectric
fiber actuator," Sensors and Actuators A: Physical, vol. 165, pp. 329-337, 2011.
b. Piezoelectric scanners used in SPM
Side view and top view of a piezoelectric tube
AFM: Atomic Force Microscope
SPM: Scanning Probe Microscopy
Voltage driving for getting
x direction displacement
Multitube actuators
Advantages:
1.Much more accurate actuation
can be achieved by deliberate
arrangement of the four tubes.
2. Multitube structure has better
performances under certain
conditions.
(a) single-tube actuator, (b) four-tube actuator.
Piezoelectric tubes with film electrodes on their outer and inner surfaces can be
used to compose multitube actuators. The actuator of four piezoelectric tubes can
substitute the traditional single-tube actuator.
Experiments
The end surface of the four-tube actuator.
The trace of a distinct point on
the actuator’s moving head.
Miniature tubular centrifugal
piezoelectric pump
The structure of the centrifugal pump using wobbling
motion of a metal tube to push the liquid out.
(a) The mechanical structure of a prototype pump.
(b) The photograph of the prototype pump.
Y. T. Ma, Z. H. Feng, et al., "Miniature tubular centrifugal piezoelectric pump utilizing wobbling motion,“
Sensors and Actuators A: Physical, vol. 157, pp. 322-327, 2010.
Experimental measurement
233.2Hz
120Vp-p
2.0kPa
Flow rate at different driving
frequencies, under 120Vp-p driving
voltage and 2.0 kPa backpressure. A
maximum flow rate of 7.7ml/min
occurs at 232Hz.。
The relationship between the
flowrate and backpressure at
different driving voltages shows a
good linearity.
精密机械与精密仪器系 Precision Machinery and Precision Instrumentation
Two-Phase Piezoelectric Motor
Structure of the stator:
Structure of the prototype motor:
Stiffness
2.5N/mm
(a)dimensions of the stator
(b) stator settled on the base.
(a)Sectional drawing
(b) external appearance.
Experimental measurement result
Angular speed, output power, and efficiency versus load
Angular speed versus driving voltage amplitude.
Y. T. Ma, Z. H. Feng, et al., "Two-Phase Piezoelectric Motor Using a Multiple-Tube Structure actuator,“
Japanese Journal of Applied Physics, vol. 48, Sep 2009.
2. Piezoelectric Transformer
Radiator heightens power density
of piezoelectric transformers
For a specific PZT-5H sample
considered, this material can
handle 330 W/cm3 at 100 kHz in
theory. However, the maximum
output power density of current
PTs is typically less than 30
W/cm3
Construction and dimensions of proposed
piezoelectric transformer operating in
contour-extensional vibration mode
W. W. Shao, Z. H. Feng, et al., "Radiator heightens power density of piezoelectric transformers,“
Electronics Letters, vol. 46, p. 1662, 2010.
Photograph of the prototype device
PT:
Roughness Ra 0.2 μm.
 copper plate：
Dimensions：32×25×1 mm3
Roughness Ra of 0.02 μm
A layer of grease pad
thickness 0.23 mm
insulation and transfer heat.
A spring with a stiffness of 1
N/mm is attached to a bolt；a
thread pitch of 0.5 mm to supply
variable pressing force .
Results of test
When the input voltage increased to 150 Vpp,
the temperature rise of the free PT increased rapidly
over 30 ºC and then continued up to a higher value.
The characteristics of PT became quite unstable.
Based on this research, it is hoped to make metal-cased piezoelectric transformers,
which will have wide application potential in many fields.
3. Precision Control of Piezoelectric
Actuators
Charge pump controller
Hysteresis of piezoelectric actuators
Configuration of the voltage amplifier
Configuration of the charge amplifier
Piezoelectric actuators hysteresis
Switched capacitor charge pump
reduces hysteresis
Floating ground
Principle of switched charge pump
Piezoelectric actuators hysteresis
精密机械与精密仪器系 Precision Machinery and Precision Instrumentation
Experimental setup
精密机械与精密仪器系 Precision Machinery and Precision Instrumentation
Displacement resonance of
piezoelectric stack
control with large steps
control with small steps.
Displacement step is 15 nm
Charge
Voltage
The hysteresis of the voltage and
charge drive
精密机械与精密仪器系 Precision Machinery and Precision Instrumentation
The result of the three control
methods
0.02Hz
0.1Hz
0.5Hz 1Hz
5Hz
20Hz
Voltage 8.15%
8.17% 8.41% 9.21%
10.5%
10.8%
Charge 9.37%
9.19% 7.16% 4.21%
0.2%
4.65%
Switch
1.55% 1.47% 1.13%
0.72%
0.71%
1.84%
L. Huang, Z. H. Feng, et al., "Switched capacitor charge pump reduces hysteresis of piezoelectric
actuators over a large frequency range," Review of Scientific Instruments, vol. 81, p. 094701, 2010.
Charge pump controller for grounded
piezoelectric actuators
Schematic charge pump controller for the grounded load
4. Energy Harvesting
Maximum mechanical energy harvesting
strategy for a piezoelement
Standard circuit for energy harvesting
Proposed energy harvesting system using a
piezoelectric element.
W. Q. Liu, Z. H. Feng, et al., "Maximum mechanical energy harvesting strategy for a piezoelement,"
Smart Materials and Structures, vol. 16, pp. 2130-2136, 2007.
Analytical process
Proposed cycle for output maximum energy
For a fixed material and structure, the system would
exhibit a better performance following the use of the
control method suggested. This will greatly improve the
design of the power generator.
Right-angle piezoelectric cantilever
Right-angle cantilever uniform
strain distribution of piezoelement
精密机械与精密仪器系 Precision Machinery and Precision Instrumentation
Results of test
It has been determined that the competence
of the right-angle cantilever for energy harvesting under a
strain limit is 2 times larger than that of the traditional
cantilever. The right-angle cantilever system produces more
electrical energy compared to a traditional cantilever.
Strain distribution in the surface of PZT element
during vibration.
Frequency response for the two devices at sinusoidal
vibration amplitude of 2.5 m s−2
.
J. W. Xu, Z. H. Feng, et al., "Right-angle piezoelectric cantilever with improved energy harvesting efficiency,"
Applied Physics Letters, vol. 96, p. 152904, 2010.
Piezoelectric Wind-Energy-Harvesting
Device with Reed and Resonant Cavity
Outline drawing of the wind-energy-harvesting device.
Equivalent circuit
精密机械与精密仪器系 Precision Machinery and Precision Instrumentation
The device was investigated with a wind speed ranging
from 2.8 to 10m/s. An output power of 0.5–4.5mW was obtained
with a matching load of 0.46MΩ. The energy conversion
efficiency of the device could reach up to 2.4%.
Results of test
The relationships between output power,
the load resistance, and the wind speed.
Output power and the energy conversion
efficiency with a resistive load 0.46MΩ
J. Ji, Z. H. Feng, et al., "Piezoelectric Wind-Energy-Harvesting Device with Reed and Resonant Cavity,"
Japanese Journal of Applied Physics, vol. 49, p. 050204, 2010.
5. Other Researches
Signal Conditioning Methods for
Piezoelectric Sensors
The equivalent circuit of a piezoelectric element linked with a charge amplifier.
The equivalent circuit of a piezoelectric sensor linked with a voltage amplifier.
The influence of preamplifiers on the
piezoelectric sensor’s dynamic property
Experimental setup.
W. Q. Liu, Z. H. Feng, et al., "The influence of preamplifiers on the piezoelectric sensor’s dynamic property,"
Review of Scientific Instruments, vol. 78, p. 125107, 2007.
Two Vibrating Coils
A High-sensitive Static Vector
Magnetometer based on 2D vibration
Reflection method to measure vibration angle
Schematic diagram of device configuration
The linear range is about 100 μT, which is available in
earth magnet detection, navigation, vehicle detection and so on.
Science
High-speed Electrically
Actuated Elastomer
精密机械与精密仪器系 Precision Machinery and Precision Instrumentation