which were mainly based on linear dynamical mod-
els(Clayton and Devasia, 2009). Wu presented a 2-
DOF feedforward-feedback controller (Wu and Zou,
2009). Leaning also proposed a notch filter and a
inversion-based feedforward controller to enhance the
high-gain feedback(Leaning and Devasia, 2007). In-
telligent feedback controllers were also investigated.
Liaw used neural network to enhance the motion
tracking of piezo-based flexible mechanisms(Liaw
and Shirinzadeh, 2009). Shieh and Hsu investigates
the adaptive control (Shieh and Hsu, 2008). Ad-
ditionally, dynamic hysteresis models were investi-
gated to achieve high bandwidth tracking(Jiang and
Chen, 2010; Janaiden and Rakheja, 2008). Based on
rate-dependent Prandtl-Ishlinskii (P-I) hysteresis, Tan
proposed the hysteresis-based inversion to extend the
tracking bandwidth(Tan and Ang, 2009), but it is dif-
ficult to design modern control techniques using rate-
dependent hysteresis. Alternatively, most modern
controllers are designed using non-hysteretic models.
In this paper, the H
∞
composite control is designed
using the proposed hysteretic dynamics of PMS. The
proposed composite controller comprises of an sep-
arate H
∞
feedback controller and an inversion-based
feedforwardcontroller. More accurate tracking is thus
presented at high frequencies.
This paper is organized as follows. First, Section
2 presents the modeling of the coupled hysteretic dy-
namics with physical meanings. Next, Section 3 pro-
vides the analysis of the composite control strategy of
the hysteretic dynamics. Then, the H
∞
composite con-
trol strategy is developed in Section 4. To validate the
proposed modeling and control approaches, the ex-
perimental studies are provided in Section 5. Finally,
Section 6 makes a conclusion of this paper.
2 COUPLED HYSTERETIC
DYNAMICS IN PMS
In this section, the multi-field modeling of the hys-
teretic dynamics in PMS is presented. The hysteretic
dynamics model is derived from the material, elec-
trical and mechanical fields. The complete model of
the hysteretic dynamics consists of the static Preisach
hysteresis effect, creep effect, electrical and vibration
dynamics.
Fig. 1 shows the complete hysteretic model struc-
ture of PMS. The hysteretic model is derived as fol-
lows. First, the electrical model of the voltage ampli-
fier is presented. Next, the hysteresis effect due to the
lead zirconate titanate (PZT) stack is proposed using
the classical Preisach model. Additionally, the creep
effect is presented using a transfer function. Then, the
electrical model of PZT stack is proposed. Moreover,
the mechanical vibration dynamics is derived using
stiff and damping parameters. Finally, the character-
istics of the hysteretic dynamics are proposed.
RLC effect
(Amplifier)
Hysteresis
(PZT)
RC effect
˄PZT˅
Mechanical
vibration
Creep effect
(PZT)
0
u
u
Figure 1: Model structure of PMS(u
0
denotes the input volt-
age of the voltage amplifier, u denotes the output voltage
of the voltage amplifier, u
p
denotes the voltage of the PZT
stack, F denotes the actuating force due to the inverse piezo-
electric effect, x denotes the displacement of PMS, and y
denotes the drifted displacement of PMS).
2.1 Electrical Model of the Voltage
Amplifier
The power and bandwidth of voltage amplifiers are
limited. As the input frequency increases, the current
reduces and the phase delay increases. To describe
this dynamic response, the deduced electrical dynam-
ics of the voltage amplifier is presented.
Fig. 2 shows the sketch of deduced RLC electrical
dynamics of the voltage amplifier where the amplify-
ing factor is not presented. R
V
, L
V
and C
V
represent
the resistance, inductance and capacitance of the volt-
age amplifier, respectively. u
0
and u represents the
input and output voltage, respectively. Then,
U(s)
U
0
(s)
=
1/(L
V
C
V
)
s
2
+ s/(R
V
C
V
) + 1/(L
V
C
V
)
, (1)
Let ω
n1
= 1/
√
LC and ξ
n1
= 1/(2R
V
)
√
L
V
C
V
, equa-
tion (1) can be rewritten as
U(s)
U
0
(s)
=
ω
2
n1
s
2
+ 2ξ
n1
ω
n1
s+ ω
2
n1
. (2)
2.2 Preisach Hysteresis Model
The hysteresis effect of PZT material (stack) are
described using Preisach model. Fig. 3 shows the
hysteresis effect and RC electrical dynamics in the
PZT stack. Γ represents the hysteresis effect. R and
C represent the resistance and capacitance of the PZT
stack, respectively. T
em
represents the electromechan-
ical transformer ratio of the PZT material. i is the
conductor current, u is the input voltage of the PZT
stack, u
p
is the effective voltage for the PZT stack.
The hysteresis between the input voltage and
the effective PZT voltage can be represented as
the following Preisach model (Mayergozy, 2003)
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