An Overview of Piezoelectric Self-Sensing Actuation for Nanopositioning Applications: Electrical Circuits, Displacement, and Force Estimation <s> A. Piezoelectric Effect-Dynamic Electrical Properties <s> Research on shunted piezoelectric transducers, per- formed mainly over the past decade, has generated new opportuni- ties for control of vibration and damping in flexible structures. This is made possible by the strong electromechanical coupling associ- ated with modern piezoelectric transducers. In vibration control applications, a piezoelectric transducer is bonded to, or embedded in a base structure. As the structure deforms, the piezoelectric el- ement strains and converts a portion of the structural vibration energy into electrical energy. By shunting the piezoelectric trans- ducer to an electrical impedance, a part of the induced electrical energy can be dissipated. Hence, the impedance acts as a means of extracting mechanical energy from the base structure. This paper reviews recent research related to the use of shunted piezoelec- tric elements for vibration damping and control. In particular, the paper presents an overview of the literature on piezoelectric shunt damping and discusses recent observations on the feedback nature of piezoelectric shunt damping systems. <s> BIB001 </s> An Overview of Piezoelectric Self-Sensing Actuation for Nanopositioning Applications: Electrical Circuits, Displacement, and Force Estimation <s> A. Piezoelectric Effect-Dynamic Electrical Properties <s> In positioning applications, the drawbacks of piezoelectric actuators are hysteresis, nonlinearity and creep in piezoelectric displacement. Hence, a feedback control using a displacement sensor is usually essential for a precise positioning. Such displacement sensors hinder device miniaturization, necessitate a complicated configuration, and increase the manufacturing cost. In this study, a self-sensing control system using permittivity change detection was demonstrated. This system is based on the linear relationship between the permittivity and the piezoelectric displacement. This linear relationship was verified experimentally. And we examined the self-sensing positioning control using a real-time permittivity change detection system, and the non-linear piezoelectric property was successfully compensated. <s> BIB002 </s> An Overview of Piezoelectric Self-Sensing Actuation for Nanopositioning Applications: Electrical Circuits, Displacement, and Force Estimation <s> A. Piezoelectric Effect-Dynamic Electrical Properties <s> We present a self-sensing control method of piezoelectric actuators that compensate the hysteresis characteristics by using the linear relationship between the permittivity change and the piezoelectric displacement. In this article, improvement of this method is described. Increasing the frequency of the voltage for a permittivity detecting, the sensitivity of the permittivity detection was improved and the accuracy of the displacement sensing could be enhanced. In addition, by applying this self-sensing method, we tried to overcome the creep phenomenon that is a peculiar problem of piezoelectric actuators. <s> BIB003 </s> An Overview of Piezoelectric Self-Sensing Actuation for Nanopositioning Applications: Electrical Circuits, Displacement, and Force Estimation <s> A. Piezoelectric Effect-Dynamic Electrical Properties <s> Abstract We present a self-sensing control method for piezoelectric actuators, which enables high-resolution positioning without an external positioning sensor. One of the present authors previously proposed a self-sensing piezoelectric actuator control system (Kawamata et al. (2008) [1] and Ishikiriyama and Morita (2010) [2] ). In the previous studies, a linear relationship between piezoelectric displacement and permittivity change was discovered, and this linear relationship was applied for positioning control. To detect permittivity changes, a high frequency voltage signal (permittivity detection voltage), in addition to the driving voltage signal, was applied to the actuator. The permittivity change was monitored as the amplitude of the current at the same frequency as the permittivity detection voltage. From this current amplitude, the permittivity change was easily calculated in real time. However, the positioning resolution was insufficient compared to that of traditional external positioning sensors, such as a strain gage sensor. In this study, we improved the positioning resolution by introducing a differential current measurement using two piezoelectric elements, one on each side of a bimorph actuator. The phase of the detected current signal was taken into consideration using a lock-in amplifier. In other words, the conductivity-related current and the permittivity-related current were measured separately. With these improvements, the permittivity change related to the piezoelectric displacement could be measured precisely, and self-sensing feedback control with a positioning error of less than 0.4 μm over a movement range of 80 μm was demonstrated. <s> BIB004 </s> An Overview of Piezoelectric Self-Sensing Actuation for Nanopositioning Applications: Electrical Circuits, Displacement, and Force Estimation <s> A. Piezoelectric Effect-Dynamic Electrical Properties <s> Piezoelectric actuators are typically modeled as capacitive elements for control purposes. An important model parameter, clamped capacitance, is traditionally considered constant and obtained through offline measurements. However, the capacitance value changes with operating conditions such as electric fields, environmental temperatures, and aging. In addition, traditional capacitance measurements are not hysteresis free. In this research, a hysteresis independent real time capacitance measurement technique is proposed. This is achieved by superimposing a high frequency ripple over the normal control voltage signal and comparing the resulting current signal to the voltage ripple. Since the mechanical bandwidth of the actuator is much lower than the ripple voltage, no measurable movement is induced by the measurement technique, and a clamped capacitance is determined. It is demonstrated that the measurement is largely independent of hysteresis and it shows good agreement with an LCR meter. The on-line capacitance measurement is very useful for characterising piezoelectric actuators and for implementing more robust control schemes. <s> BIB005 </s> An Overview of Piezoelectric Self-Sensing Actuation for Nanopositioning Applications: Electrical Circuits, Displacement, and Force Estimation <s> A. Piezoelectric Effect-Dynamic Electrical Properties <s> Abstract Piezoelectric displacement contains hysteresis and creep properties. Therefore, a displacement sensor is indispensable in precise positioning devices; however, the additional space and cost are problems. On the other hand, self-sensing methods that utilize the piezoelectric actuator itself as the displacement sensor have been proposed. With these self-sensing methods, precise positioning becomes possible without an additional displacement sensor. We developed a self-sensing method utilizing the non-hysteresis relationship between the permittivity change and the piezoelectric displacement. Furthermore, a differential current measurement method using two piezoelectric elements with a bimorph actuator could improve the positioning accuracy. In this study, we examine the control of a positioning stage using two multilayered piezoelectric actuators by applying the differential current measurement method for self-sensing control. The results indicate that the differential current measurement method is effective for precise positioning control. The positioning errors due to hysteresis decreased from 0.8 μm to 0.1 μm for a 10 μm displacement range. In addition, permittivity feedback control could compensate for the creep property. <s> BIB006 </s> An Overview of Piezoelectric Self-Sensing Actuation for Nanopositioning Applications: Electrical Circuits, Displacement, and Force Estimation <s> A. Piezoelectric Effect-Dynamic Electrical Properties <s> This letter presents a displacement self-sensing method for piezoelectric actuators that takes into account the effect of the deformation of these latter on their electrical impedance. A self-updating digital electrical impedance equivalent to that of the piezoelement is suggested in order to overcome the mismatch problem met when considering a static analog electrical impedance as classically used. Then, the design of an observer that performs a thorough separation of the electric current due to the direct piezoelectric effect from the measured electric current is proposed in order to estimate the piezoelectric actuator displacement. The experimental results validate the proposed approach and demonstrate the efficiency of the developed self-sensing circuit and its observer to estimate the displacement of the piezoceramics actuator for long duration measurement of constant step signal. <s> BIB007 </s> An Overview of Piezoelectric Self-Sensing Actuation for Nanopositioning Applications: Electrical Circuits, Displacement, and Force Estimation <s> A. Piezoelectric Effect-Dynamic Electrical Properties <s> Abstract This article extends the conventional permittivity change based displacement self-sensing technique for piezoelectric actuators to an impedance change based displacement–force self-sensing technique. The presented methodology evaluates changes in capacitance and resistance at an electrical resonance frequency and uses a third order polynomial fit to estimate displacement and force. Experimental validations show a mean error of 1.8%, and an error standard deviation of 1.9% for displacement and a mean error of 1.7%, and an error standard deviation of 1.8% for force. <s> BIB008
SSA based on the piezoelectric direct effect demands a tedious continual tuning in order to discriminate the signal that is related to the PEA's strain from the dielectric signal, the noisy environmental conductive materials, or outer metal parts, such as electrical wires BIB001 , BIB007 . As already mentioned, SSA based on the piezoelectric direct effect cannot provide a good estimate of the PEA's displacement if its initial state is unknown. Whereas one already knows that applying an electric field and/or an external load induces a deformation in the PEA, recent works have shown that the PEA's impedance is also affected by electric field application BIB007 and external loads BIB008 . Therefore, instead of voltage-/charge-based SSA, many researchers suggested using the change of PEA's electrical properties as a means to estimate its deformation and perceived external force. Kawamata et al. BIB002 were the first to use the linear relationship between the permittivity change and the PEA's displacement for SSA. The permittivity feedback control based on this linear relationship has shown its effectiveness for high-precision positioning BIB004 , BIB003 . Since then, not only the changing relative permittivity BIB006 but also capacitance BIB005 , or capacitance and resistance at the same time BIB008 , have been used to estimate the PEA's displacement and/or perceived force. For an online implementation of the SSA based on the PEA's change of electrical properties, that is, an online estimation of the PEA's generated displacement and the force applied thereto based on its impedance variation, one requires a real-time impedance variation measurement scheme.