A novel similarity-based hysteresis empirical model for piezoceramic actuators
Transcript of A novel similarity-based hysteresis empirical model for piezoceramic actuators
Accepted Manuscript
Title: A Novel Similarity-Base Hysteresis Empirical Modelfor Piezoceramic Actuators
Author: <ce:author id="aut0005" biographyid="vt0005">Zhi-Lin Lai<ce:author id="aut0010" biographyid="vt0010">Zhen Chen<ce:author id="aut0015" biographyid="vt0015">Xiang-Dong Liu<ce:author id="aut0020"biographyid="vt0020"> Qing-He Wu
PII: S0924-4247(13)00159-3DOI: http://dx.doi.org/doi:10.1016/j.sna.2013.04.002Reference: SNA 8289
To appear in: Sensors and Actuators A
Received date: 13-9-2012Revised date: 1-4-2013Accepted date: 1-4-2013
Please cite this article as: Zhi-Lin Lai, Zhen Chen, Xiang-Dong Liu, Qing-He Wu, ANovel Similarity-Base Hysteresis Empirical Model for Piezoceramic Actuators, Sensors& Actuators: A. Physical (2013), http://dx.doi.org/10.1016/j.sna.2013.04.002
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A Novel Similarity-Base Hysteresis Empirical Model for
Piezoceramic Actuators
Zhi-Lin Laia,b, Zhen Chen∗a,b, Xiang-Dong Liua,b, Qing-He Wua,b,
aSchool of Automation Beijing Institute of Technology, Beijing 100081, ChinabKey laboratory for Intelligent Control & Decision of Complex Systems Beijing Institute of
Technology
Abstract
This paper presents a novel dynamic hysteresis model for the Piezoceramic
actuators. The model is based on two new phenomena discovered in this paper,
the geometric similarity and the time scale similarity. In order to improve the
accuracy of the model, the method of virtual extremum is proposed to amend
the similarity. In the experiments, four kinds of input signals with different
frequencies are used to test the proposed model. And the outputs predicted
from the proposed model are compared with those obtained from the Preisach
model. The results show that the proposed model gives good accuracy and
performs better than the Preisach model. Especially, with the help of the time
scale similarityit is much easier to build a dynamic model.
Keywords: Piezoelectric actuator; Dynamic hysteresis model; Similarity
model
1. INTRODUCTION
Piezoceramic actuators(PZTs) with advantages of high precision and fast
response have been widely used in nano-positioning technology. Nevertheless,
the hysteresis behavior of PZTs, becomes a major difficulty of the high precision
positioning technology. Many methods have been studied to characterize the
hysteresis phenomenon of PZTs. Among them, the earlier studies of the hys-
teresis modeling focused on the description of the single-loop hysteresis curve,
Preprint submitted to Sensors & Actuators: A. Physical February 7, 2013
*Manuscript(includes changes marked in red font for revision documents)
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for example, using polynomials to capture the major loops[1]. As research con-
tinues, many different models have been proposed to describe the hysteresis of
the piezoceramics. The most widely used model is the Preisach model[2−6], the
Maxwell resistive capacitor (MRC) model [7] and the Bouc-Wen model[8−9].
Besides, several approaches for modeling the hysteresis based on empirical
observations have been developed[10,11,12,13,14], most of which provide physical
insights into the hysteresis phenomenon. Giving several empirical observations,
Jung[10] built reference-models of the PZTs and got satisfactory results. Sun
Lining[11] proposed a turning voltage based mathematical model to describe
hysteresis, in which assumes that the reference curves have an approximately
linear relationship with other curves. By introducing the properties effects at
the turning points (called ”targeting the turning points”, ”curve alignment”,
and ”wiping out” ), Bashash[12] proposed a constitutive memory-based math-
ematical modeling framework. But a large number of memory units must be
used to record the key points of the hysteresis past trajectory that are required
for the prediction of its future response. Then in the Ref [13-14], Bashash gave
the improvement of the proposed model. However, these empirical models are
not rate-dependent and the memory-based hysteresis model still needed many
memory units.
Using the empirical modeling methods, a rate-dependent empirical model
without using many memory units has been proposed for the PZTs in this
paper. Two new phenomena, geometric similarity and time scale similarity, are
introduced to constitute the similarity of hysteresis. The geometric similarity
describes the similarity among the output displacement curves in static; and the
time scale similarity which discloses the relationships of the output displacement
curves with different frequencies is to make the model dynamic. Using the two
similarities, a rate-dependent empirical model can be built. However, large
errors may generate in predicting the outputs of the higher-order sub-loops.
The virtual extremum is proposed to amend the similarity of the displacement
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curves to reduce the modeling errors. Finally, a rate-dependent empirical model
based on the amended similarity is built and verified in the experiments.
The structure of the article is arranged as follows: In section 2, the exper-
imental platform has been introduced; In section 3, the geometric similarity
and the time scale similarity is discovered to describe the similarity relation-
ship of hysteresis of the PZTs; Then, a hysteretic model modeling by the two
similarities is established and amended in section 4. Also in this section, the
wiping-out property and congruency property of the model has been verified;
In section 5, the model has been tested by different kinds of inputs. And the
proposed model is also compared with the Preisach model; Finally, Section 6
concludes the researches.
2. THE EXPERIMENTAL SYSTEM
The researches in this paper are carried out on a PZT experimental system.
Figure 1 shows the structure of the experimental system. The controller can
be seen in figure 2. Where, the cpu is DSP(TMS320LF2407); a 16-bit D/A
converter (AD669) and a 16-bit A/D converter(AD976) are used here. Figure
3 illustrates some of the equipment used in the experiment. The high voltage
power amplifier (HPV series) is used to drive the PZTs(MPT-1JRL/I002); the
output voltages of the power amplifier range from 0V ∼ 150V, and the resolution
of which is 5mV. The input voltages which the PZTs can withstand are -30V
∼ 120V. Considering the safety margin and the driving ability of the power
amplifier, the input voltages of the PZTs are limited in the range of 0V to
100V. A resistance strain gauge sensor has been installed within the platform as
a micrometer to get the displacement signals. The resolution of the resistance
strain gauge sensor is 0.01 µm. And the actual output displacements of the PZTs
are calibrated by a laser interferometer(Agilent 5529A Dynamic Calibrator)
whose resolution is 1nm. Figure 4 is the Laser interferometer.
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Figure 1: The PZT control system Figure 2: The controller
Figure 3: The PZT experiment devices Figure 4: The laser interferometer
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3. THE SIMILARITY OF THE HYSTERESIS NONLINEARITY
In the figure 5, the voltage signal is the input of the PZTs; and the dis-
placement curve is the output of the PZTs. The displacement curve consists of
ascending curve and descending curve. The horizontal axis of the chart which
is labeled by the sample number is time line. The input voltage and the output
displacement can form a hysteresis loop, as shown in figure 6. The maximum
and the minimum point (in figure 5) is the turning point in the hysteresis loop.
In Ref.[15] Madelung proposed that the hysteresis curve can only determine
by the turning point. And how the turning point (maximum/minimum point)
determines the hysteresis curve is what will be study here.
In this section, isosceles triangular input signals (input voltage sequences)
have been used to drive the PZTs. The input voltage sequences have the same
voltage difference (νV) between adjacent points(That’s to say the slope is fixed.).
Define reference curve Dr[n] is the displacement curve driven by the low fre-
quency triangular input with the maximum voltage of 100V and minimum volt-
age of 0V. The geometric similarity does not consider the frequency of the
triangle waves, and the sampling period of the displacement curve keeps the
same. When discussing the time scale similarity, the frequencies of the triangle
waves and the sampling periods are different, but the sampling times are the
same in one cycle of the triangle waves.
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Figure 5: Some basic concepts
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Figure 6: The hysteresis loop
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3.1 The geometric similarity of the displacement curves
1 The relationship between the ascending displacement curves of the PZTs
First, consider the triangle input signals with the same minimum voltages
but different maximum voltages. Figure 7 shows three sets of triangle signals
with the same minimum voltage (0V), and the maximum voltage of the three
signals is 80V, 70V, 60 V, respectively. Figure 8 shows the displacement curves
of the PZTs. And the hysteresis loops can be seen in figure 9. We can see
from the displacement curves that the three ascending curves include by the
rectangular box have the same path. The errors of the three paths shown in
figure 10 are ranged from -0.02 µm to 0.02µm. That means the ascending curves
in the rectangular box have the same track.
0 100 200 300 400 500 600 700 8000
10
20
30
40
50
60
70
80
Sample No.
Vo
lta
ge
(V)
V1
V2
V3
Figure 7: Voltages signals
0 100 200 300 400 500 600 700 800−2
0
2
4
6
8
10
Sample No.
Dis
pla
ce
me
nt(
µm
)
D1
D2
D3
Figure 8: Displacement curves
Then, consider the triangle inputs with the same maximum voltages but
different minimum voltages. Figure 11 shows the driving voltage signals. The
maximum voltage of triangle input signals is 100V, while the minimum voltages
range from 0V to 95V. Figure 12 and figure 13 are the displacement curves and
hysteresis loops, respectively. In Ref.[11], the relationship between the ascending
lines in hysteresis loops is regarded as linear(the line OA,OB,..., in figure 13).
Here, we are interested in the ascending displacement curves in figure 12. Use
D0[n] to describe the ascending displacement curve of the reference curve (the
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0 10 20 30 40 50 60 70 80−2
0
2
4
6
8
10
Voltage(V)
Dis
pla
se
me
nt(
µm
)
L1
L2
L3
Figure 9: Hysteresis loops
0 50 100 150 200 250−0.06
−0.04
−0.02
0
0.02
0.04
0.06
0.08
Sample No.
Dis
pla
ce
me
nt(
µm
)
Error1Error2Error3
Figure 10: Ascending errors
red curve OdO′
d in the figure 12); and use DVmin[n] to describe the ascending
displacement curve driven by the triangle signal with the minimum voltage of
VminV. We can see in figure 12, when Vmin = 50V, the displacement curve
DVmin[n] is the curve JdJ
′
d (in figure 12), and the driving voltage is JvJ′
v in
figure 11. Define a displacement sub curve D0Vmin
[n] (the curve OdJ) which is a
portion of the D0[n] to correspond the curve JdJ′
d. The length of the curve OdJ
is determined by the driving voltage: In figure 11, VJ is the voltage of the point
J, and VJ − VOv= VJ′
v− VJv
. Actually, what we study here is the relationship
between JdJ′
d and OdJ .
Suppose the curve JdJ′
d similar to OdJ , so the two curves meet the Eq.(1).
DVmin[n] = λa ×D0
Vmin[n] + ωa (1)
where, λa ∈ R is the slope of the similarity, ωa ∈ R is the intercept of the
similarity. Because the similarity between the output displacement curves is
relative to the extreme value of the input voltage, the slopes and the intercepts
vary with the extreme value. Here, define ∆Va = Vmin − 0 (the difference of
the minimum voltages between VminV and 0V) to describe the variation of the
extreme. And the driving voltage of JdJ′
d is JvJ′
v (in figure 11), which can be
expressed by V amin[n] = Vmin + n× ν.
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Different PZTs have different characteristics of the hysteresis, so the identifi-
cation of the slopes and the intercepts should be completed through experiments.
According to least-square criterion, we can get the values of λa and ωa corre-
sponding to each extremum voltage. Then, higher order polynomials are used
to fit the variations of parameters (λa and ωa), whose variations follow ∆Va.
The relationship between ∆Va and λa can be seen in figure 14; and the
relationship between ∆Va and ωa can be seen in figure 15. The two curves can
be fitted by the polynomial equations (2) and (3), respectively. The coefficients
of the polynomials can be seen in table 1.
λa(∆Va) =
6∑
i=0
ai × (∆Va)6−i (2)
ωa(∆Va) =
3∑
i=0
bi × (∆Va)3−i (3)
Table 1: The coefficients of the polynomial λa(∆Va) and ωa(∆Va)
Polynomial Coefficient Value
λa(∆Va)
a0 5.669× 10−12
a1 -1.356× 10−9
a2 1.198× 10−7
a3 -4.809× 10−6
a4 0.0001
a5 -0.0047
a6 1.0008
ωa(∆Va)
b0 -2.333× 10−7
b1 -0.0004
b2 0.1573
b3 -0.0094
The above analysis shows: when giving an ascending input, the geometric
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0 200 400 600 800 1000
0
20
40
60
80
100
Sample No.
Vol
tage
(V)
Ov
O’v
Av
A’vJ’v
JvJVj
Vov
Vjv
Vj’v
...
...∆Va
...
Figure 11: 20 sets ascending voltage signals
0 200 400 600 800 10000
2
4
6
8
10
Sample No.
Dis
plas
emen
t(µm
)
O’dJ’d A’d
OdAd
Jd
J
...
...
...
Figure 12: 20 sets ascending displacement curves
0 20 40 60 80 1000
2
4
6
8
10
Voltage(V)
Dis
plac
emen
t(µm
)
A
BC
O
...
...
Figure 13: 20 sets hysteresis loops
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0 20 40 60 80 1000.82
0.84
0.86
0.88
0.9
0.92
0.94
0.96
0.98
1
1.02
∆ Va(V)
λ a
Actual points The fitting curve
Figure 14: Relationship between λa and ∆Va
0 20 40 60 80 100−2
0
2
4
6
8
10
12
∆ Va(V)
ωa
Actual pointsThe fitting curve
Figure 15: Relationship between ωa and ∆Va
similarity between DVmin[n] and D0
Vmin[n] can be described by Eq.(4).
DVmin[n] = λa(∆Va)×D0
Vmin[n] + ωa(∆Va) (4)
2 The relationship between the descending displacement curves of the PZTs
First, giving 20 sets of the driving voltage signal as shown in figure 16, which
have the same minimum voltages of 0V and the different maximum voltages
range from 100V to 5V. Figure 17 is the displacement curves driven by the
signals. Just like the ascending curves we study above, We use D0[n] to describe
the ascending displacement curve of the reference curve (the red curve OO′ in
the figure 17); and use DVmax[n] to describe the ascending displacement curve
driven by the triangle signal with the maximum voltage of VmaxV. We also
define a displacement sub curve D0Vmax
[n] (the curve OA in figure 17) which is a
portion of the D0[n] to correspond the curve BB′ in figure 17. Here, the point
A (in figure 17) is determined by the driving voltage: VO − VA = VB − V ′
B(in
figure 16). So, what we study here is the relationship between OA and BB′.
And suppose the displacement curve OA similar to BB′, as shown in figure 17.
So the two curves meet the Eq.(5).
DVmax[n] = λd ×D0
Vmax[n] + ωd (5)
where, λd ∈ R is the slope of the similarity, ωd ∈ R is the intercept of the
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similarity, and they are both related to the ∆Vd = 100 − Vmax(the difference
of the maximum voltages between 100V and VmaxV). And the driving voltage
of displacement curve BB′(in figure 17) is the voltage curveBB′(in figure 16),
which can be expressed by V dmax[n] = Vmax − n× ν.
0 100 200 300 400 500 600 700 800 900
0
20
40
60
80
100
Sample No.
Vo
lta
ge
(V)
BA
OVo
Vb
Va
Vb’ B’ O’
∆Vd
Figure 16: 20 sets descending voltage signals
0 200 400 600 800
0
2
4
6
8
10
Sampling No.
Dis
pla
ce
me
nt(
µ m
)
A
O
O’
B
B’
Figure 17: 20 sets descending displacement curves
According to least-square criterion, we can get the values of λd and ωd
corresponding to each extremum voltage. The relationship between λd and
∆Vd can be seen in Figure 18; and the relationship between ωd and ∆Vd can be
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seen in Figure 19. The two curves can be fitted by the polynomial equations (6)
and (7), respectively. The coefficients of the polynomials can be seen in table 2.
λd(∆Vd) =
7∑
i=0
ci × (∆Vd)7−i (6)
ωd(∆Vd) =
6∑
i=0
di × (∆Vd)6−i (7)
0 20 40 60 80 1001
1.05
1.1
1.15
1.2
1.25
1.3
1.35
1.4
1.45
∆Vd(V)
λd
Actual pointsThe fitting curve
Figure 18: Relationship between λd and ∆Vd
0 20 40 60 80 100−18
−16
−14
−12
−10
−8
−6
−4
−2
0
∆ Vd(V)
ωd
Actual pointsThe fitting curve
Figure 19: Relationship between ωd and ∆Vd
The above analysis shows: when giving an descending input, the geometric
similarity between D0Vmax
[n] and DVmax[n] can be described by Eq.(8).
DVmax[n] = λd(∆Vd)×D0
Vmax[n] + ωd(∆Vd) (8)
3.2 The time-scale similarity of the displacement curves
The hysteresis of the PZTs is rate-dependent. In order to fully describe the
hysteresis of PZTs, the frequency must be considered.
First, two sets of triangular signals whose only difference is the frequency
will be used here, as shown in figure 20. The different frequencies are labeled
as f0 and f (f0 < f), and the cycle are T0 and T . The displacement curves
are shown in figure 21. And use the DT0[n] and DT [n] to describe the two
displacement curves. In order to compare two displacement curves, the time
scale amplification needs to be carried out. If the cycle of DT0[n] is amplified
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Table 2: The coefficients of the polynomial λd(∆Vd) and ωd(∆Vd)
Polynomial Coefficient Value
λd(∆Vd)
c0 5.233× 10−13
c1 -1.535×10−10
c2 1.773× 10−8
c3 -1.015× 10−6
c4 2.957× 10−5
c5 -0.0004
c6 0.00626
c7 0.999
ωd(∆Vd)
d0 -2.398×10−10
d1 5.903× 10−8
d2 -5.439× 10−6
d3 0.0002
d4 -0.0047
d5 -0.125
d6 -0.0245
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VWXYZ[\]^_`abc ad^_`abc ad efg
Figure 20: Triangular voltage signals with different frequency
hijklmnopqrst ruopqrst ru vwx
Figure 21: Triangular displacement outputs with different frequency
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NT (NT < 1) times to make NT × 1/f0 = 1/f , then the curves after time scale
(labeled DNT×T0[n]) has the same cycle with DT [n]. For example, three sets
of displacement curves with different frequencies are shown in figure 22. The
cycle of the displacement curve in red is 0.01s; that in black is 1s; and in blue
is 100s. Then the time scale amplification is carried out: to make the cycle
of the displacement curve with the frequency of 0.01Hz magnify 1/1000 times,
the cycle of the displacement curve with the frequency of 1Hz magnify 1/100
times, then they can be drawn in the same figure with the displacement curve
of 100Hz, as the figure 23 shown (Also, the time is labeled by the sampling
number.). From figure 23 we can see that the three curves are similar. So, we
suppose DNT×T0[n] similar to DT [n]. And the similarity can be expressed by
the following Equation:
DT [n] = λf ×DNT×T0[n+m] + ωf (9)
where, λf ∈ R is the magnification; ωf ∈ R is to move the curves in vertical
axis direction. m is the phase difference of two sets of curves, which is to move
the curves in horizontal axis direction. In order to obtain these coefficients, the
genetic algorithm is used. The number of species is 100. the genetic generation
is 4000. And the search interval of λf is [1 1.5]; The search interval of ωf is
[-1 1]; The search interval of m is [-10 10], and m is an integer. The indicator
function is the fitting errors. The results are shown in table 3.
Figure 24 and 25 shows the λf and ωf changes with lg(f/f0). The two
curves can be fitted by the polynomial equations (10) and (11), respectively.
The coefficients of the polynomials can be seen in table 4.
λf (lg(f/f0)) =3
∑
i=0
xi × (lg(f/f0))3−i (10)
ωf (lg(f/f0)) =3
∑
i=0
yi × (lg(f/f0))3−i (11)
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iptyz |~ ~ |~ ~ |~ ~
z
Figure 22: Curves before scale amplification
0 200 400 600 800 1000 1200 1400 1600 18000
2
4
6
8
10
Sample No.
Disp
lace
men
t(¦Ìm
)
1180 1200 1220 1240
8.68.8
99.2 Curve of 100Hz
Curve of 1HzCurve of 0.01Hz
Figure 23: Curves after scale amplification
100
101
102
103
104
0.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
Frequency(Hz).
λ f
Actual pointsThe fitting curve
Figure 24: Relationship between λf and
lg(f/f0)
100
101
102
103
104
−0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Frequency(Hz).
ωf
Actual pointsThe fitting curve
Figure 25: Relationship between ωf and
lg(f/f0)
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iptTable 3: The coefficients λf , ωf and m
f/f0 λf ωf m
2 0.9905 0.0041 0
3 0.9889 0.0268 0
4 0.9866 0.0305 0
5 0.9852 0.0339 0
6 0.9836 0.0391 0
7 0.9820 0.0477 0
8 0.9806 0.0558 0
9 0.9800 0.0569 0
10 0.9786 0.0655 0
50 0.9665 0.1087 1
100 0.9589 0.1850 1
1000 0.9338 0.2945 6
10000 0.9252 0.3283 9
Table 4: The coefficients of the polynomial λf (lg(f/f0)) and ωf (lg(f/f0))
Polynomial Coefficient Value
λf (lg(f/f0))
x0 0.000936
x1 -0.00468
x2 -0.014635
x3 0.99748
ωf (lg(f/f0))
x0 -0.011632
x1 0.061259
x2 0.02523
x3 -0.005604
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The time scale similarly has been defined to the displacement curves which
driven by the different frequencies. If the cycle of the displacement curves with
the frequency of f0 is amplified NT times to make DNT ∗T0[n] and DT [n] have
the same cycle, then, the two curves meet the following equation:
DT [n] = λf (lg(f/f0))×DNT×T0[n+m] + ωf (lg(f/f0)) (12)
4. A NOVEL SIMILARITY-BASED MODEL
4.1 Hysteresis model based on the similarity
After giving the geometric similarity and the time scale similarity, a novel
similarity-based model will be built in this section. The new model need the
reference curve Dr[n], which is driven by a triangle inputs with the frequency
of f0, the maximum voltage of Vmax (that’s 100V in this paper.), the minimum
voltage of Vmin (that’s 0V in this paper.). Then, a displacement curve Dc[n]
can be get through the similarities introduced above. Here, Dc[n] is the any
curve with the frequency of f > f0, the maximum voltage of V ′
min > Vmin, the
minimum voltage of V ′
max < Vmax. The ascending and descending curve of Dr[n]
is respectively Dra[n] and Dr
d[n]. In the same way, the ascending and descending
curve of Dc[n] is respectively Dca[n] and Dc
d[n].
The schematic diagram of the modeling is shown in figure 26. Suppose the
frequency of the input signal is f ; the minimum voltage is V ′
min; the maximum
voltage is V ′
max.
Step 1: using the time scale similarly Eq.12, transfer the reference curve into
the curve with the frequency of f :
DrT [n] = λf (lg(f/f0))×Dr
NT×T0[n+m] + ωf (lg(f/f0)) (13)
where, by looking up table, the value of m can be get. Here, we use DrT [n] to
describe the new reference curve of the frequency of f . So, the D0T V ′min[n] to
correspond the D0Vmin[n] , and D0
T V ′max[n] to correspond the D0V max[n].
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Figure 26: Schematic diagram of modeling
Step 2: When meets the minimum/maximum input voltage, using the geo-
metric similarity to obtain the ascending/descending displacement curves driv-
ing by triangular voltage input:
Dca[n] = λa(V
′
min − Vmin)×D0T V ′min[n] + ωa(V
′
min − Vmin) ascending
Dcd[n] = λd(Vmax − V ′
max)×D0T V ′max[n] + ωd(Vmax − V ′
max) descending
(14)
Step 3: Using the displacement curve got in step 2 and their triangular
driving voltage signals, a hysteresis loop can be get, as shown in figure 27.
NOTE: The triangular driving voltage signals are the isosceles triangle sig-
nals, and whose maximum value and minimum value is determined by the input
signal. And the slope of the isosceles triangle is fixed. The triangular voltage
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can be expressed by Eq.(15):
V Ta [n] = V ′
min + n× ν ascending
V Td [n] = V ′
max − n× ν descending(15)
where, the ν is the voltage difference between adjacent points in triangular
voltage sequences.
¡¢¢£¤ ¥¤ ¦¤ §¤ ¨¤ ©¤ ª¤ «¤ ¬¤¦ª¬
¥¤¢¡®¯°±
²³³ ´³³ µ³³ ¶³³ ·³³³³²³´³µ³¶³ ¸ ¹¢¡®¯ º®»£¡ ¹¯ ¼¢½¸®¾¢¡®¯
²³³ ´³³ µ³³ ¶³³ ·³³³³·²¿ÀµÁ¶Â
º®»£¡ ¹¯ ¼¢½
à ®¹¯Ä¡®Å¢¡®¯ ¯¹®¡Ã ®¹¯Ä¡®Æ £¡®Ç»¹ÇÄÅ
Figure 27: The establishment of intermediate hysteresis loop
Step 4: Using the hysteresis loop consists of Eq.(14)and Eq.(15) to get the
output displacements.
4.2 The amending of the similarity model
In actually, the geometric similarity is just the total describe of the rela-
tionship of the hysteresis loops between the reference loop (Corresponding to
the reference curve.) and the internal loops having the turning points(like the
points A, B, C, D in figure 28.) on it , which is called first-order segment. For
the other internal hysteresis loops whose turning points are not in the reference
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ÈÉÊËÌËÍËÎÏËÐÑÏËÎÒÓÎÔÏÕÍÖË
ÊËÌËÍËÎÏË ÒËÑÏËÎÒÓÎÔÏÕÍÖË×Ø ÙÚÛÜ
ÝÞ ßà áâãäåÐÔËæâç
Figure 28: Relationship of turning points and the hysteresis loop
loop (Like the points E and F. ), the similarity Eq.(14) may bring some errors.
Therefore, the proposed displacement curve similarity should be amended as
follow:
Dma [n] = La(N1)× Dc
a[n] + Ca(N1) ascending
Dmd [n] = Ld(N2)× Dc
d[n] + Cd(N2) descending(16)
where, Dm[n] is to describe the displacement curves being modified. La(N1)
and Ld(N2) is the correction factor of the slope; and Ca(N1) and Cd(N2) is
the correction factor of the displacement migration. All of the four factors are
relative to the max/min voltage (the turning points). N1 is the latest sam-
pling number of the minimum voltage; N2 is the latest sampling number of the
maximum voltage.
1. La(N1) and Ld(N2)
The hysteresis loop has a phenomenon: the ascending curves will converge
to one point; and the descending curves will also converge to the other point
[11]. As shown in figure 29, four different lines (La, Lb, Lc, Ld) are excited by
different input signals which are all have a maximum voltage of 100V. We can
see from the displacement curves that all the curves have the same maximum
displacement. The minimum voltages (0V) also have the same property. With
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the help of those properties, a method can be proposed to get the La(N1) and
Ld(N2).
Here a concept of virtual extrimum (include the virtual upper limit and the
virtual lower limit. ) has been introduced. Suppose that all the ascending
voltage signals will rise to the virtual upper limit; and all the descending volt-
age signals will down to 0 V (virtual lower limit). According the properties
mentioned above, all the virtual maximum displacements and virtual minimum
displacements converge to one point, respectively. As shown in figure 30, the
virtual upper limit predicted by the model is the point B (The displacement
is r′), however, it should be A (The displacement is r). So we use La(N1) to
modify the ascending curve O1B to the curve O1A. Support the displacement
of point O1 is ro, then we can get:
La(N1) = (r − ro)/(r′− ro) = (r −Dm
d [N1 − 1])/(r′ −Dmd [N1 − 1]) (17)
And in the descending process, the same conclusion can be get. In the
figure 30, the virtual lower limit predicted by the model is the point D (The
displacement is d′), however, it should be C (The displacement is d ). So we
use Ld(N2) to modify the descending curve O2D to the curve O2C. Support
the displacement of point O2 is d0, then we can get:
Ld(N2) = (d− do)/(d′− do) = (d−Dm
a [N2 − 1])/(d′ −Dma [N2 − 1]) (18)
2. Ca(N1) and Cd(N2)
As we know, if the input signals are continuous, then the output displace-
ments are also the continuous. So, the displacements in turning points should
be continuous. Then, we can get:
Ca(N1) = Dma [N1 − 1]− La(N1)×Dc
a[N1]
Cd(N2) = Dmd [N2 − 1]− Ld[N2]×Dc
d[N2](19)
4.3 Wiping-Out Property and Congruency property verification of the simi-
larity model
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0 200 400 600 800 1000 1200 1400 1600 1800 2000−2
0
2
4
6
8
10
12
Sample No.
Dis
pla
se
me
nt(
¦Ìm
)
LaLbLcLd
100V
Figure 29: Inputs with the same maximum
voltage
0 200 400 600 800 1000 1200 1400 1600 1800 2000−2
0
2
4
6
8
10
12
Sample No.
Dis
pla
se
me
nt(
¦Ìm
)
100VB
CD
0V
A
O2
O1
N1 N2
Figure 30: Sketch of amendment
Wiping-Out Property and Congruency property is two important properties
of the Hysteresis mentioned by Mayergoyz [3].
Wiping-Out property means: the input maximum will wipe out the history
maximums which are smaller; and the input minimum will wipe out the history
minimums which are bigger. The wiped out historical maximums or minimums
will exert no influence to the new outputs anymore.
Using the input signals S1 and S2, as shown in figure 31(a) (after the point
H , the input signals are the same.), we can get the model output curves S1 and
S2 in figure 31(b). We can see from the figure 31(b), curve S1 and S2 have the
same displacement in point C, that’s to say: the extremum value A does not
exert influence on C (extremum value A is wiped out); and after the point H ,
S1 and S2 have the same path, that’s to say: after the point H , those points
A,B,D,E, F,G are all wiped out. In the figure 31(b) also has curve S2′, which
is the output of the model does not amend. We can see from the figure, S2′ and
S1 does not overlap after point H . That’s to say, the model without amending
dose’t have the wiping out property.
Congruency property: if the inputs have the same two consecutive extremum
values, then the two minor (internal) hysteresis loops are congruent. As shown in
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0 500 1000 1500 20000
20
40
60
80
100
120
Sample No.
Volta
ge(V
)
S1S2
A
B
C
D
E
F
G
H
I
(a) Input signals
200 400 600 800 1000 1200 1400 1600 1800 2000
0
2
4
6
8
10
12
Sample No.
Disp
lase
men
t(µm
)
1800 180510.52510.53
10.535
S1S2S2’
1500 16002
2.5
FB
D
E
G
IA
C
H
(b) Displacement curves
Figure 31: Wiping-Out Property
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figure 32(a), the extremum values of the model inputs are (20, 80, 20, 100, 20, 80, 20V ).
There are two consecutive extremum values (20, 80, 20V )(labeled 1, and 2 in fig-
ure 32(a).), which have the two minor (internal) hysteresis loops are congruent
(labeled 1,and 2 in figure 32(b) ).
0 500 1000 1500 20000
20
40
60
80
100
Volta
ge(V
)
Sample No.
1 2
(a) Input signals
20 40 60 80 1002
4
6
8
10
12
Voltage(V)
Disp
lacem
ent(u
m)
78 808
8.2
8.4
12
(b) Hysteresis loops
Figure 32: Congruency Property
4.4 The memory space and the computation complexity of the model
Figure 33 is an implementation of the modeling. From the Figure, we can
see that three important steps should do in the implementation.
1. Update the parameters of the time scale similarly when the frequency of
the input signal is changed.
2. Update the parameters of the geometric similarity when meets the mini-
mum/maximum input voltage.
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Get, , ,a a a aL C !
Update, ,f f m !
Ascending
hysteresis
loop
Get, , ,d d d dL C !
Descending
hysteresis
loop
Output
Figure 33: An implementation of the modeling
3. Using the reference hysteresis loop (Created by the reference curve and
its driving voltage.) to find the output displacement corresponded to the input
voltage. And calculate the output of the model with the help of the parameters
get in step 1 and 2.
And now, we analyze the implementation in two aspects: memory space and
the computation complexity.
1. Memory space:
Because the parameters in step 1 are got from the Eq.10, Eq.11; the param-
eters in step 2 are got from the Eq.2, Eq.3, Eq.6, Eq.7, Eq.17, Eq.18 and Eq.19.
And in the step 3, the reference hysteresis loop is stored by two polynomials.
Therefore, a low number memory spaces are enough in this implementation.
2. Computation complexity:
Computational complexity is a measure of the resource needed to perform a
computation. Often, it used to reflect the run-time of an algorithm. It can be
seen clearly in the Figure 33: time is consumed in the three steps mentioned in
this section. The step 1 will be run when the frequency changed; and the step 2
will be run when encounters extremums. So, step 1 and step 2 is executed in a
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low frequency. As a result, the run-time of the implementation is determined by
step 3 which will be executed in every cycle. In step 3, a polynomial about the
reference hysteresis loop is executed. And the parameters get in step 1 and step
2 are involved in the calculation according the Eq.14 and Eq.16. Here, we can
find that the computational complexity of the implementation is determined by
the polynomials of the hysteresis loop.
In figure 34, two polynomials are used to fitting the hysteresis loop (Divided
into the ascending part and the descending part). The order of the two polyno-
mials is 3. And the polynomials shown in Eq.20, where La and Ld is the output
displacement of the hysteresis loop, V ol is the input voltage. And the coeffi-
cients of the two polynomials are in table 5. So the computational complexity
of the implementation is O(3).
La(V ol) =3∑
i=0
Lai × (V ol)3−i ascending
Ld(V ol) =3∑
i=0
Ldi × (V ol)3−i descending
(20)
−20 0 20 40 60 80 1000
2
4
6
8
10
12
Voltage(V)
Dis
plac
emen
t(µm
)
48.5 49 49.56.92
6.94
6.96
6.98
7
7.02
Ascending hysteresis curve
Descending hysteresis curve
Figure 34: Fitting the hysteresis loop
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Table 5: The polynomial coefficients of hysteresis loop
Polynomial Coefficient Value
La(V ol))
La0 -4.4656×10−6
La1 0.0008
La2 0.0825
La3 0.1806
Ld(V ol))
Lb0 -1.1201×10−6
Ld1 -0.00025
Ld2 0.1496
Ld3 0.3613
5. EXPERIMENT
Although the similarities are concluded using the triangular input voltage,
the model also can be used when giving other input signals. In this section, 4
kinds of input signals are used to verify the model we proposed. The reference
curve with a frequency of 0.01Hz is used to establish the model. And a Preisach
model has been built to compare with the new model. Here, the Preisach model
is built according to the Eq.(21) as follows [2]:
f(t) =n−1∑
k=1
[F (αk, βk−1)− F (αk, βk)] + F (u(t), βk) ascending
f(t) =n−1∑
k=1
[F (αk, βk−1)− F (αk, βk)] + [F (αn, βn−1)− F (αn, u(t))] descending
(21)
where f(t) is the output displacement of the system and u(t) is the input voltage.
F (α, β) = fα− fαβ. ( fα presents the output of the first-order hysteresis curves
when u(t) = α . fαβ presents the output of the first-order hysteresis curves
when the input u(t) decline down to β from α .)
1 The triangular signals
The maximum and the minimum voltage of the input triangular are respec-
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tively 80V and 20V. The results of this experiment with the frequency of 0.1Hz
are shown in figure 35(a-b). The results of this experiment with the frequency
of 100Hz are shown in figure 35(c-d). The specific data can be seen in table 6
and 7.
0 5 10 15 20 25 300
2
4
6
8
10
Time(s)
Dis
pla
se
me
nt(
µm
)
New model output of 0.1HzActual output of 0.1HzPreisach model output
(a) Displacement curves of low fre-
quency
0 5 10 15 20 25 30 34−0.6
−0.4
−0.2
0
0.2
0.4
0.6
Time(s)
Dis
pla
se
me
nt(
µm
)
New model error of 0.1HzPreisach error of 0.1Hz
(b) Error curve of low frequency
0.005 0.010 0.015 0.020 0.025 0.030 0.034
2
3
4
5
6
7
8
9
10
11
Time(s)
Dis
pla
se
me
nt(
µm
)
New model out put of 100HzActual output of 100HzPreisach model output
(c) Displacement curves of high fre-
quency
0 0.005 0.010 0.015 0.020 0.025 0.030 0.034−0.8
−0.6
−0.4
−0.2
0
0.2
0.4
0.6
Time(s)
Dis
pla
se
me
nt(
µm
)
New model error of 100HzPreisach error of 100Hz
(d) Error curve of high frequency
Figure 35: Triangle inputs
2 The sinusoidal signals
The maximum and the minimum voltage of the sinusoidal input are 65V and
5V, respectively. The results of this experiment with the frequency of 0.1Hz are
shown in figure 36(a-b). The results of this experiment with the frequency of
100Hz are shown in figure 36(c-d). The specific data can be seen in table 6 and
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7.
5 10 15 20 25 30 34
1
2
3
4
5
6
7
8
9
Time(s)
Dis
pla
se
me
nt(
µm
)
New model output of 0.1HzActual output of 0.1HzPreisach model output
(a) Displacement curves of low fre-
quency
5 10 15 20 25 30 34
−0.4
−0.3
−0.2
−0.1
0
0.1
0.2
Time(s)
Dis
pla
se
me
nt(
µm
)
New model error of 0.1HPreisach error of 0.1Hz
(b) Error curve of low frequency
−0 0.005 0.010 0.015 0.020 0.025 0.030
1
2
3
4
5
6
7
8
9
Time(s)
Dis
pla
se
me
nt(
µm
)
New model output of 100HzActual output of 100HzPreisach model output
(c) Displacement curves of high fre-
quency
0 0.005 0.010 0.015 0.020 0.025 0.030 0.034−0.8
−0.6
−0.4
−0.2
0
0.2
0.4
0.6
Time(s)
Dis
pla
se
me
nt(
µm
)
New model error of 100HPreisach error of 100Hz
(d) Error curve of high frequency
Figure 36: Sinusoidal inputs
3 The attenuate sinusoidal signals
The results of this experiment with low frequency are shown in figure 37(a-
b). The results of this experiment with high frequency are shown in figure
37(c-d). The specific data can be seen in table 6 and 7.
4 The mixed signals
The results of this experiment with low frequency are shown in figure 38(a-
b). The results of this experiment with high frequency are shown in figure
38(c-d). The specific data can be seen in table 6 and 7.
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0 5 10 15 20 25 30 34−1
0
1
2
3
4
5
6
7
8
Time(s)
Dis
pla
se
me
nt(
µm
)
New model output of low frequencyActual output of low frequencyPreisach model output
(a) Displacement curves of low fre-
quency
5 10 15 20 25 30 34
−0.5
−0.4
−0.3
−0.2
−0.1
0
0.1
Time(s)
Dis
pla
se
me
nt(
µm
)
New model error of low frequencyPreisach error of low frequency
(b) Error curve of low frequency
0 0.005 0.010 0.015 0.020 0.025 0.030 0.034−1
0
1
2
3
4
5
6
7
8
Time(s)
Dis
pla
se
me
nt(
µm
)
New model output of high frequencyActual output of high frequencyPreisach model output
(c) Displacement curves of high fre-
quency
0 0.005 0.010 0.015 0.020 0.025 0.030 0.034−0.7
−0.6
−0.5
−0.4
−0.3
−0.2
−0.1
0
0.1
0.2
Dis
pla
se
me
nt(
µm
)
Time(s)
New model error of high frequencyPreisach error of high frequency
(d) Error curve of high frequency
Figure 37: Attenuate sinusoidal inputs
Table 6: The performance of the new model
Frequency Triangular Sinusoidal Attenuate Mixed
Low
Max output(µm) 9.12 7.26 6.91 10.41
range(µm) −0.15 ∼ 0.0 −0.1 ∼ 0.1 −0.07 ∼ 0.1 −0.17 ∼ 0.17
Relative error(%) 1.64 1.38 1.45 1.63
High
Max output(µm) 8.86 7.06 6.79 10.0
range(µm) −0.16 ∼ 0.03 −0.03 ∼ 0.18 −0.08 ∼ 0.14 −0.01 ∼ 0.24
Relative error(%) 1.81 2.55 2.06 2.4
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0 5 10 15 20 25 30 34
0
2
4
6
8
10
12
Time(s)
Dis
pla
se
me
nt(
µm
)
New model output of low frequencyActual output of low frequencyPreisach model output
(a) Displacement curves of low fre-
quency
0 5 10 15 20 25 30 34
−0.4
−0.3
−0.2
−0.1
0
0.1
0.2
0.3
0.4
Time(s)
Dis
pla
se
me
nt(
µm
)
New model error of low frequencyPreisach error of low frequency
(b) Error curve of low frequency
0 0.005 0.010 0.015 0.020 0.025 0.030 0.034
0
2
4
6
8
10
12
Time(s)
Dis
pla
se
me
nt(
µm
)
New model output of high frequencyActual output of high frequencyPreisach model output
(c) Displacement curves of high fre-
quency
0.005 0.010 0.015 0.020 0.025 0.030 0.034
−1
−0.8
−0.6
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
Time(s)
Dis
pla
se
me
nt(
µm
)
New model error of high frequencyPreisach error of high frequency
(d) Error curve of high frequency
Figure 38: Mixed inputs
Table 7: The performance of the Preisach model
Frequency Triangular Sinusoidal Attenuate Mixed
Low
Max output(µm) 9.39 7.56 7.22 10.58
range(µm) −0.35 ∼ 0.0 −0.38 ∼ 0.0 −0.53 ∼ 0.17 −0.35 ∼ 0.22
Relative error(%) 3.73 5.03 7.34 3.3
High
Max output(µm) 9.39 7.56 7.22 10.58
range(µm) −0.62 ∼ 0.18 −0.63 ∼ 0.17 −0.65 ∼ 0.57 −0.91 ∼ 0.46
Relative error(%) 6.6 8.33 7.89 8.6
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6. CONCLUSION
A novel similarity-base hysteresis empirical model for PZTs has been in-
troduced in this paper. First, using the triangle inputs with different extreme
points, the geometric similarity of the displacement curves has been presented;
and using the triangle inputs with different frequencies, the time scale similarity
of the displacement curves has been presented. Then, the similarity-based hys-
teresis model can be obtained. However, the similarity is just the total describe
of the relationship between the reference curve and the displacement curves
having the turning points on it. For others, big errors may be caused. So, some
methods have been proposed to amend the model. The proposed model is easily
built; saving memory space; and with the appropriate time complexity; more
important, the dynamic of the model is solved in a new and easy way.
It can be seen from the modeling process, the hysteresis loops corresponding
to each ascending process and decreasing process have been given (in Figure
27). As we know, the hysteresis loops are the input-output relationship of the
PZTs, so using those loops the inverse model can also be built. And that’s what
we will do next.
However, Problems are still exist: It is found that the trajectory in initial
stage is different from the later stage, although the input signal is the same (It
can be seen clear in figure 31(c-d)); The errors mainly caused by the approx-
imation of the higher-order sub-loops, so methods should be used to improve
it.
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Biography of the authors Zhilin Lai born in 1984, he received B.S. degree from Nanchang University in 2006 and M.S. degree from Beijing Institute of Technology (BIT) in 2009. Now he is a Ph.D. candidate in BIT. His main research interest lies in hysteresis modeling and compensation. Zhen Chen born in 1976, he received M.S. and Ph.D. degrees from BIT in 2005 and 2008, respectively. He is currently a lecturer with Automation College in BIT. His research interest is servo system design and control. Xiangdong LIU born in 1971, he received M.S. and Ph.D. degrees from Harbin Institute of Technology (HIT) in 1995 and 1998, respectively. From 1998 to 2000, he did his post doctor research in mechanical postdoctoral research center in HIT. He is currently a professor with Automation College in Beijing Institute of Technology (BIT). His research interests include high-precision servo control, spacecraft attitude control, Chaos theory. Qinghe Wu received the B.S. degree in electrical engineering from Huazhong University of Science and Technology, in 1982, the post-graduate diploma and the Dr. Tech. Sci. degrees from the Swiss Federal Institute of Technology (ETH), in 1984 and 1990, respectively. He is currently a professor with Automation College in Beijing Institute of Technology (BIT). His research interest mainly covers robust control theory and multidimensional systems.
Biography of the authors
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Figure List
Figure 1 The PZT control system
Figure 2 The controller
Figure 3 The PZT experiment devices
Figure 4 The laser interferometer
Figure 5 Some basic concepts
Figure 6 The hysteresis loop
Figure 7 Voltages signals
Figure 8 Displacement curves
Figure 9 Hysteresis loops
Figure 10 Ascending errors
Figure 11 20 sets ascending voltage signals
Figure 12 20 sets ascending displacement curves
Figure 13 20 sets hysteresis loops
Figure 14 Relationship between a and aV
Figure 15 Relationship between a and aV
Figure 16 20 sets descending voltage signals
Figure 17 20 sets descending displacement curves
Figure 18 Relationship between d and dV
Figure 19 Relationship between d and dV
Figure 20 Triangular voltage signals with different frequency
Figure 21 Triangular displacement outputs with different frequency
Figure 22 Curves before scale amplification
Figure 23 Curves after scale amplification
Figure 24 Relationship between f and 0lg( / )f f
Figure 25 Relationship between f and 0lg( / )f f
Figure 26 Schematic diagram of modeling
Figure 27 The establishment of intermediate hysteresis loop
Figure 28 Relationship of turning points and the hysteresis loop
Figure 29 Inputs with the same maximum voltage
Figure 30 Sketch of amendment
Figure 31 Wiping-Out Property
(a) Input signals
(b) Displacement curves
Figure 32 Congruency Property
(a) Input signals
(b) Hysteresis loops
Figure 33 An implementation of the modeling
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Figure 34 Fitting the hysteresis loop
Figure 35 Triangle inputs
(a) Displacement curves of low frequency
(b) Error curve of low frequency
(c) Displacement curves of high frequency
(d) Error curve of high frequency
Figure 36 Sinusoidal inputs
(a) Displacement curves of low frequency
(b) Error curve of low frequency
(c) Displacement curves of high frequency
(d) Error curve of high frequency
Figure 37 Attenuate sinusoidal inputs
(a) Displacement curves of low frequency
(b) Error curve of low frequency
(c) Displacement curves of high frequency
(d) Error curve of high frequency
Figure 38 Mixed inputs
(a) Displacement curves of low frequency
(b) Error curve of low frequency
(c) Displacement curves of high frequency
(d) Error curve of high frequency
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1. Two new phenomena have been discovered in this paper, the geometric similarity and the time scale similarity. 2. The use of the time scale similarity can make the hysteresis model dynamic in an easy way. 3. ‘Virtual extremum’ is a good way to improve the precision of the model. 4. The proposed model are easily built; and saving computational time and memory space.
*Highlights (for review)