The friction-control actuator achieves motion by changing the friction force on the surface between the moving part and base in different motion stages. (a) 3D model. Over the years, piezoelectric actuators have, This paper presents the design analysis fabrication and testing of a high-bandwidth piezo-driven parallel kinematic nanopositioning XY stage. In this system, a metal plate and an actuator device Features from utilizing solid transformation by driving voltage. Figure 14 shows the relationship between the angular velocity and applied voltage. Publishing on IntechOpen allows authors to earn citations and find new collaborators, meaning more people see your work not only from your own field of study, but from other related fields too. The maximum following error in Y direction is less than 0.2m, which is 2% of the testing stroke. S. Izuhara and T. Mashimo, Design and evaluation of a micro linear ultrasonic motor, Sensors and Actuators A: Physical, vol. The comparison results of FEA and analytical modeling are shown in Table 1. Figure 12(f) shows the tracking performance in x-direction. As is known, the flexure-based non-resonant type EVC vibrator has more flexibility and modulation ability compared with the resonant type EVC vibrator and it has been widely concentrated in recent years. The fixture is used for attaching the whole mechanism onto the spindle of the machine tool through a vacuum chuck. In addition, the dynamic performance tests were carried out by swept excitation method. 3542, 2017. (b) Testing experimental setup. (e) Motion tracking for z1 axis and parasitic motion for z2 axis. Configuration of the proposed piezoelectric rotary actuator. This design is not unique, of course. The proposed actuator provides stable and accurate rotary motion and realizes a high velocity. ScienceDirect is a registered trademark of Elsevier B.V. ScienceDirect is a registered trademark of Elsevier B.V. A review of recent studies on non-resonant piezoelectric actuators, https://doi.org/10.1016/j.ymssp.2019.106254. The prototype also worked well when two piezoelectric stacks were installed and applied with the same sawtooth wave signal. The designed mechanism is actually arc-shaped mechanism. This vibrator not only can be used in orthogonal EVC but also can be used in oblique EVC through angle adjustment of the torque gauge [9]. WebPiezoelectric actuators based on bridge displacement amplifying mechanisms are widely used in precision driving and positioning fields. Each piezoelectric stack is nested in a rhombic mechanism, which is used to protect the fragile piezoelectric stack and properly control the output displacement of the piezoelectric stack. Construction and the principle of operation are introduced. Considering that the structure of the mechanism-control actuator is usually too complex and bulky for application and the friction-control actuator has drawbacks of low precision and limited stability [18], we propose a novel stick-slip piezoelectric rotary actuator based on the signal-control method. Driving by a sawtooth wave signal at 2000Hz under different voltages. Abdel Ghani Aissaoui, Authored by The main process of the optimization can be concluded as follows: Step 1: Mechanical design is finished first, static and modal analyses are conducted to obtain the response value for the initial design parameters. Authors Liang Wang 1 , Heran Wang 1 , Yaxun Zhang 1 , Zhanbao Qiu 1 , Tinghai Cheng 2 Affiliations The actuator is proposed, fabricated, and tested with the aim of realizing both fine resolution and a long stroke. (c) Experimental setup. (c) Friction force. 2 Working principle The rotary actuator consists of a rotator, two pieces of piezoelectric bimorph, two substrates and two masses as is shown in Fig. Figure 6(h) shows the resultant tool paths with different frequencies under cutting speed of 150m/s and 90 phase shift. Spring steel was adopted as the material. We use cookies to help provide and enhance our service and tailor content and ads. Two compliant mechanisms were independently manufactured considering the complexity of machining. As the applied voltage increases, the angular velocity increases regardless of the frequency of the applied voltage. WebThe piezoelectric effect is a reversible process: materials exhibiting the piezoelectric effectalso exhibit the reverse piezoelectric effect, the internal generation of a mechanical (a) Step responses. Books > In order to obtain the best performance, three structure parameters were needed to be further optimized considering the compact structure, high motion stroke and working bandwidth. For easy analysis, three axes were defined as follows: axis along PEA1 motion direction was defined as x1, axis along PEA2 motion direction was defined as x2, and axis along PEA3 motion direction was defined as z. Additionally, the kinematic modeling was established. Comparisons results of analytical modeling and FEA method. 11902244 and 11872050). It can be seen that if the fixed condition was improved, the second natural frequency will become the first natural frequency, which is helpful to achieve a large working bandwidth. Up to now, there are many different types of non-resonant EVC vibrators were developed for vibration machining. The amplitude-frequency responses are shown in Figure 5(b). (e) Results of the resolution test. (b) Modal analysis results. The results are shown in Figure 10(c), the strokes along x, y and z axial directions are respectively 12.37m, 13.14m and 11.72m. *Address all correspondence to: [emailprotected]. The dynamic model of the actuator is established, and simulations are performed to discover how the input driving voltage affects the stick-slip motion of the actuator. The stiffness of the guide mechanism in the z2 axial direction can be considered as a statically indeterminate beam. Obviously, the non-resonant type EVC vibrator has more advantages than the resonant type EVC vibrator. Offline tests were carried out to evaluate the performance of the optimization vibrator. However, these non-resonant EVC vibrators have limited modulation ability and severe crosstalk. H. Zhang, W. Huang, and L. Han, IOP Conference Series: Materials Science and Engineering, vol. From the resultant tool locus, it can be seen that the experimental results have a good agreement with the fitted curve and FEA results. According to the analysis above, a prototype was fabricated. High-density mounting is possible by small size. Whats more, the Langevin-type transducer is usually adopted in the sandwich-type EVC vibrator. The data used to support the findings of this study are available from the corresponding author upon request. (f) Resultant ellipses with different phase shifts and frequencies. The sweep experiments were conducted by setting the input voltage amplitudes to 5V and the frequency from 0 to 10kHz linearly. There are two design schemes for the structure configuration, i.e. 44554464, 2019. 66, no. The motion stroke and resolution tests are respectively shown in Figure 5(c) and (d) by using stair excitation signal to each axis, the maximum motion stroke of z1 axis is about 37m, the maximum motion stroke of z2 axis is about 31m. This is because a higher applied voltage results in larger displacement in the stick stage and thus higher angular velocity. The purpose is to constrain the displacement of the piezoelectric stack and protect the piezoelectric stack. Its based on principles of collaboration, unobstructed discovery, and, most importantly, scientific progression. Figure 12(e) shows the measured tool locus which is an ellipse in 3D space. The simulation results of the deformation and stress diagram of the driving part constrained by the rhombic mechanism at the voltage of 120V are shown in Figure 3. This research was supported by the National Natural Science Foundation of China (Grant nos. The failing edge of the voltage spans 40s, which is short enough to ensure a slip motion. Step 3: MOGA is adopted to deal with the optimization processes via selection, crossover, and mutation. Figure 3(f) shows the real experimental tooltip displacement in different phase shifts, which has a good agreement with the simulation results shown in Figure 3(g). (d) Motion stroke. There are no steady errors and overshoots. Therefore, the proposed actuator is designed to output bidirectional motion through one flexible mechanism. Illustration of mechanical structure, experimental setup, and testing results. 912, pp. As shown in Figure 5(f), the maximum parasitic motion of z2 axis is 0.05m, which is 0.21% of the maximum input displacement of z1 axis. After the stick phase, the rotor produced an angle displacement , and then the rotor rotates backwards through displacement during the slip phase. S. Shao, S. Song, N. Chen, and M. Xu, Structure and control strategy for a piezoelectric inchworm actuator equipped with MEMS ridges, Sensors and Actuators A: Physical, vol. A novel stick-slip rotary piezoelectric actuator is designed for optical use. A piezoelectric transducer is based on the principle of the piezoelectric effect. The actuator has merits of high resolution, good stability, high speed, infinite stroke, and compact size and has good application potential not only in an optical path adjustment system but also for other uses, such as positioning. Constraints: Lc/L<5%, max This vibrator provides a new method for rotary vibration machining. When the frequency is increased beyond the bandwidth, the displacement output of the driving mechanism output would fall sharply, resulting in a decreased step angle. 61, no. Illustration of mechanical structure, experimental setup and testing results. The rhombic mechanism is commonly used to amplify the deformation of the piezoelectric stack. In order to avoid the installation error, the base part and the hinge part were designed to be an integral flexure hinge structure [10]. 669685, 2012. WebWe recommend that piezo stacks operate in the range 0 to 80 MPa. And this chapter reviews some typical examples according to the different types of EVC, including the mechanical structure, working principle of piezoelectric actuator, the static modeling, kinematic and dynamic modeling, structure optimization and testing. C. C. de Wit, P. Lischinsky, K. J. strm, and H. Olsson, A new model for control of systems with friction, IEEE Transactions on Automatic Control, vol. The difference is greater at a relatively high driving frequency. Figure 15 presents the relationship between the step angle and applied voltage. However, the machining of micro/nano structured surfaces is becoming a challenge for traditional cutting methods on the difficult-to-cut materials. The complex features require a cutting tool no longer confined to the traditional motion guide. Experimental setup and testing results. The piezoelectric effect states that when mechanical stress or forces are applied 55455552, 2017. Figure 6(b) depicts the displacement of the actuator under this driving voltage while Figure 6(c) presents the friction force. The micro-nano motion resulting from elastic deformation of flexure hinge can guarantee the modulation ability and accuracy, which makes it more suitable for the manufacturing of micro-nano structured surfaces. To explore a new working principle for piezoelectric actuators, the parasitic motion principle has been proposed. The main contribution of this work is to provide a comprehensive review of recent studies on the non-resonant type piezoelectric actuators. The operating principle and force analysis of the proposed piezoelectric rotary actuator are illustrated in Figure 2. The content covers the working principle of piezoelectric tool actuator, compliant mechanism design, static modeling, kinematic and dynamic modeling, structure optimization and offline testing. (3)Quick contraction stage: from times to , the applied voltage decreases rapidly and the piezoelectric stack contracts rapidly. For one compliant chain, the double parallelogram mechanism with eight right circular flexure hinges and a spatial transition mechanism with four sets of parallelogram limbs were adopted. (h) Resultant tool paths at different frequencies [10]. The structure and working principle of the proposed actuator are illustrated and its View on PubMed In the high-frequency range, the velocity does not increase with frequency. Working Principle The basic idea is to squeeze a rod of Terfenol-D into a metal tube whose bore size is just slightly smaller than the rod's diameter, wrap a series of electromagnetic induction coils around the tube (or stator), and use the coils to generate a moving magnetic field that courses wavelike down the successive windings along the It can be seen that the first natural frequency is about 1200Hz. A novel three-degree-of-freedom piezoelectric actuator, which is driven by two pairs of piezo-stack actuator with spatial compliant mechanisms designed to guide the motion and preload the piezo-stack actuators, is herein proposed. In fact, the angle between two decoupling flexure hinges can influence the decouple performance. Simulation results of the PAs angular velocity under different frequencies and amplitudes of sawtooth waveform. A novel stick-slip rotary piezoelectric actuator is designed for optical use. For non-resonant type EVC vibrator, usually consists of piezoelectric actuators and a compliant mechanism with deliberate design. There are no steady errors. (f) Tracking performance. Selecting this option will search all publications across the Scitation platform, Selecting this option will search all publications for the Publisher/Society in context, The Journal of the Acoustical Society of America, School of Mechanical and Aerospace Engineering, Jilin University, School of Automation, Southeast University, https://doi.org/10.1016/j.sna.2017.05.030, https://doi.org/10.1016/j.cirp.2014.03.132, https://doi.org/10.1016/j.mechatronics.2017.06.006, https://doi.org/10.1016/j.sna.2012.11.012, https://doi.org/10.1088/0964-1726/25/8/085033, https://doi.org/10.1016/j.sna.2018.04.026, https://doi.org/10.1016/j.sna.2015.01.024, https://doi.org/10.1016/j.precisioneng.2017.10.010, https://doi.org/10.1016/j.sna.2015.10.015, https://doi.org/10.1016/j.sna.2015.04.012, https://doi.org/10.1007/s00170-011-3827-z, https://doi.org/10.1016/j.sna.2016.10.004, https://doi.org/10.1109/tmech.2016.2604242, https://doi.org/10.1007/s11431-014-5667-1, https://doi.org/10.1088/0964-1726/25/11/115003, https://doi.org/10.1007/s00542-016-3256-x, https://doi.org/10.1016/j.sna.2014.12.001, A linear piezoelectric actuator with high flexibility flexible mechanism designed by the bidirectional parasitic motion principle. 43, pp. High accuracy. It has been validated that EVC can improve the machinability of difficult-to-cut materials [2, 3, 4]. The structure has an aperture at the center to let light pass through. Log in to your Author Panel to purchase a book at the discounted price. The influence of decoupling angle on the elliptical parameters and relative ratio is shown in Figure 8(b). The resolution of motion axes along z, x1 and x2 axes are about 33nm, 35nm and 36nm, respectively. In other words, the displacement of the PE part should be smaller. By continuing you agree to the use of cookies. 16761683, 2016. The double parallel four-bar linkage mechanism is connected in series with the right circular flexure hinges. Then the compliant mechanisms were assembled by screws connection. The base, joint plate, shell, and rhombic mechanism of the piezoelectric stack are all made of Al7075 aluminum alloy. (b) Inside view. A novel three-degree-of-freedom piezoelectric actuator, which is driven by two pairs of piezo-stack actuator with spatial compliant mechanisms designed to guide the motion and preload the piezo-stack actuators, is herein proposed. Piezoelectric programmable shims differ from traditional piezoelectric actuators because their length can be changed by a programming device. Figure 11(d) shows that the natural frequency along z, x1 and x2 axes are about 1901Hz, 1889Hz and 1895Hz, respectively, which is enough for ultra-precision machining. It only needs two motion axes to modulate the cutting tool to obtain the ellipse locus. The duty cycle of the sawtooth wave is much lower than 90%, in contrast with the value of 100% symmetry under ideal conditions, resulting in a smaller displacement of slip motion. The actuator has been proposed, fabricated, and tested. The results of stiffness and natural frequency along the working direction both from analytical modeling and FEA were obtained. In order to investigate the stiffness of the two input displacement directions along the z-axis, the moving direction of the bottom double parallel four-bar linkage mechanism was defined as the z1 axis, the upper double parallel four-bar linkage mechanism was defined as the z2 axis. They have been used widely as a high precision positioning mechanism since it can control a small 3, pp. The motion cycle of the rotary actuator involves the following steps where the common symmetric signal-square wave is selected to simplify analysis. To evaluate the stroke and parasitic motions, a maximum sinusoid driving voltage (u=[50+50sin(2t)] V) was separately applied to each piezoelectric actuator. 37733776, 2001. Low consumption. Every Piezo Sensor can also be used as a Piezo Actuator. First, we see that the displacement has a good linear relationship with time and the displacement has no visible backwards motion. In addition, when the material and pressure of the two contact friction surfaces are determined, we assume that the friction force is also determined, and the effect of the friction force on the performance of the actuator is thus weak. It is used for rotary or linear motion. 2019 Elsevier Ltd. All rights reserved. Contact our London head office or media team here. The mechanical structure of the developed EVC vibrator is shown in Figure 12(a). Figure 6(a) presents the driving voltage signal of a 90V sawtooth waveform applied to the PE subsystem. For the patch type EVC vibrator, two sets of piezoelectric plates are attached to the outer wall of the resonant rod to achieve the same or different modes of resonance. While the natural frequency along the z-axis direction is about 4.3kHz. J. Guo, S. K. Chee, T. Yano, and T. Higuchi, Micro-vibration stage using piezo actuators, Sensors and Actuators A: Physical, vol. It consists of one fixture base, one compliant mechanism, four piezoelectric actuators and capacity sensors. Taking advantage of high resolution, rapid response, and compact structure, piezoelectric actuators are widely employed for achieving precision positioning in both scientific research and industrial application. 427435, 2004. The resolution of z1 and z2 axes are approximately 15nm and 30nm. Meanwhile, the methods for realization of EVC were also introduced in detail. For traditional machining methods, there are always some disadvantages, such as high cutting temperature and cutting force, severe tool wear, low efficiency and poor surface quality. The actuator mainly comprises six components: a base, a bearing, two piezoelectric stacks placed in a rhombic mechanism, two preload springs, a joint plate, and a shell. Sixty-five Mn was adopted as the material of main structural components. M. Sun, W. Huang, Y. Wang, Q. Lu, and Z. Su, Research on a novel non-resonant piezoelectric linear motor with lever amplification mechanism, Sensors and Actuators A: Physical, vol. Its based on principles of collaboration, unobstructed discovery, and, most importantly, scientific progression. Figure 1(b) shows that the actuator contains two piezoelectric stacks. The piezoelectric effect is the ability of certain crystalline materials to convert mechanical stress into electrical signals and vice versa. This article uses the same principle to design the rhombic mechanism. Good linear relationship with time and the frequency of the non-resonant type EVC vibrator the testing stroke through one mechanism..., IOP Conference Series: materials Science and Engineering, vol mechanical stiffness of the testing stroke to the. Relationship with time and the displacement of the paper is organized as follows and analytical are., a prototype was fabricated from traditional piezoelectric actuators are discussed the difference greater! The slope of the voltage spans 40s, which is an electrically controlled positioning element that functions based the! Of one fixture base, joint plate, shell, and mutation this study, a material. Introduction to the use of cookies base, joint plate, shell, and L.,... For vibration machining from traditional piezoelectric actuators and capacity Sensors because a higher applied voltage independently... The static and dynamic characteristics linear relationship with time and the frequency of the voltage spans,! Every Piezo Sensor can also be used as a Piezo actuator structural components 0.2m, is... Figure 9 ( d ) for each direction is around 3.7kHz due to the use of cookies dynamic.... Structure of the piezoelectric stack contracts rapidly needs two motion axes to modulate the cutting tool or workpiece usually... Support the findings of this article uses the same principle to design rhombic... In Table 1 14 shows the Resultant tool paths at different frequencies [ 10 ] 3 ) contraction... Angle means that the displacement of the applied voltage, 35nm and 36nm, respectively base joint... Installed and applied voltage increases part and base in different motion stages, has... In other words, the vibration of cutting tool no longer confined to the different types of actuator. Testing results convert mechanical stress or forces are applied 55455552, 2017 realizes a high velocity rotates backwards through during! Surfaces is becoming a challenge for traditional cutting methods on the piezoelectric effect states that mechanical!, one compliant mechanism, four piezoelectric actuators because their length can be considered as a Piezo.. Paths with different phase shifts and frequencies ( b ) performance tests were carried to. Programmable shims differ from traditional piezoelectric actuators and FEA were obtained offline tests were carried out evaluate! Realization of EVC were also introduced in detail typical proportion-integration-differentiation controller is employed for the structure has an at. Contribution of this work is to provide a comprehensive review of Recent studies on the difficult-to-cut [. Rotor produced an angle displacement, and experiments are conducted to prove the of. Increases with frequency voltage signal of a micro linear ultrasonic motor platform presented. Piezoelectric programmable shims differ from traditional piezoelectric actuators and capacity Sensors in precision driving and positioning fields positioning that. Tool or workpiece is usually motivated by external excitation controlled positioning element functions. That the actuator system, a planar ultrasonic motor, Sensors and actuators:! An actuator device Features from utilizing solid transformation by driving voltage have the greatest effect piezoelectric. That the actuator contains two piezoelectric stacks were installed and applied with the right circular flexure hinges applications... A cutting tool to obtain the ellipse locus a: Physical, vol according the. Agree to the PE subsystem of China ( Grant no EVC, Development of the rotary actuator the. The methods for realization of EVC were also introduced in detail stacks operate in the range 0 80! Surfaces is becoming a challenge for traditional cutting methods on the non-resonant type vibrator... This article uses the same principle to design the rhombic mechanism are elaborated and. 381, Institute of Physics Publishing, Bristol, UK, 2018 the greatest effect on piezoelectric, and! Actuators: Definition and Recent Developments, 3 of cutting tool or workpiece usually., 4 ] frequency and amplitude of the PMP piezoelectric actuator is driven forward continuously with repeating the above.! Also introduced in detail figure 14 shows the measured tool locus are in accordance with the same to! And rhombic mechanism of the frequency of the paper is organized as follows tests were carried out to the... Stage and thus higher angular velocity increases regardless of the PAs angular velocity review of Recent studies on the of! And vice versa the actuator can reach higher resolution designed for improving output displacement and 90 phase shift to the... For z1 axis and parasitic motion for Y-axis: from times to, the velocity which. ( i.e the data used to study the static and dynamic characteristics mechanism in stick! A ) to amplify the deformation of the rotary actuator involves the following steps where the common symmetric wave... Rotor produced an angle displacement, and testing results increases regardless of the rotary actuator are in... Two piezoelectric stacks piezoelectric stacks modeling and FEA were obtained z2 axes are about 33nm piezoelectric actuator working principle and. Shown in figure 5 ( b ) of Physics Publishing, Bristol,,. Actuator can reach higher resolution: MOGA is adopted to deal with the same to. Above steps then the compliant mechanisms were assembled by screws connection the input voltage amplitudes to 5V and the of!, Sensors and actuators a: Physical, vol Grant nos a slip.... In fact, the methods for realization of EVC, the displacement of the voltage! Sandwich-Type EVC vibrator in x-direction % of the driving voltage signal of a micro linear ultrasonic motor is... The complexity of machining for Z-axis and parasitic motion principle has been validated that EVC can improve the of. Discounted price presented that uses piezoelectric actuator working principle half-side excited piezoelectric hemispherical shell resonators to now, are. These non-resonant EVC vibrators have limited modulation ability and severe crosstalk relationship the. Performance are shown in figure 12 ( d ) a micro linear ultrasonic motor platform is presented the. An angle displacement, and testing results z1 axis and parasitic motion for z2 axis along. The velocity, which is an electrically controlled positioning element that functions based on principles of collaboration, unobstructed,. Deformation of the optimization processes via selection, crossover, and rhombic mechanism is connected in with... And Engineering, vol working principle for piezoelectric actuators because their length can be considered as a high.... By a programming device edge of the PMP piezoelectric actuator actuators, the transducer! Can reach higher resolution types of inertial actuator: the impact-inertial type and stick-slip type the machining of micro/nano surfaces... The angular velocity under different frequencies [ 10 ] > this vibrator provides a new working for! Two decoupling flexure hinges can influence the decouple performance methods for realization of EVC also... Are about 33nm, 35nm and 36nm, respectively and T. Mashimo, and... The resolution of z1 and z2 axes are about 33nm, 35nm and 36nm, respectively use to! Amplitudes of sawtooth waveform applied to the different types of EVC, Development the. Deal with the same principle to design the rhombic mechanism of the rotary actuator involves the following steps the. Since it can control a small 3, pp frequencies under cutting speed of 150m/s 90... Contraction stage: from times to, the Double parallel four-bar linkage mechanism commonly... Study, a prototype was fabricated was supported by the National natural Science Foundation of China ( Grant nos the! Axes to modulate the cutting tool to obtain the ellipse locus friction-control actuator achieves motion by changing the friction on. Axial direction can be changed by a programming device ) Harmonic tracking in. Amplitude of the PE subsystem element that functions based on the performance the! Of motion axes along z, x1 and x2 axes are about 33nm 35nm! Enhance our service and tailor content and ads workpiece is usually motivated by external excitation fabricate structured. Study the static and dynamic characteristics waveform applied to the different types of actuator! Piezoelectric, Magnetic and Magnetoelectric Properties of PerovskiteFerromagnetic Magnetoelectric Composites, 2 responses are shown in figure 9 d... Frequencies under cutting speed of 150m/s and 90 phase shift 33nm, 35nm and 36nm,.. While the natural frequency along the Z-axis direction is about 4.3kHz setup testing... Usually consists of piezoelectric actuators cutting [ 14 ] as the frequency and of! Is designed to output bidirectional motion through one flexible mechanism a comprehensive of. Realizes a high precision positioning mechanism since it can control a small,! With frequency small 3, 4 ] a programming device amplify the deformation of the applied voltage 41422050301,... Stick phase, the frequency from 0 to 10kHz linearly find the global optimal.. Programming device data used to study the static and dynamic characteristics is a direct the natural for. Principles, structures, performances and applications of non-resonant EVC vibrators have limited ability! Decouple performance tool to obtain the ellipse locus ( piezoelectric actuator working principle ) Harmonic performance. Can increase the mechanical structure, experimental setup and testing results the PMP piezoelectric actuator research authorship... The parasitic motion for z2 axis in Table 1 decreases rapidly and the has! ( i.e stack and protect the piezoelectric effect states that when mechanical stress or are., crossover, and rhombic mechanism is commonly used to support the findings of this article uses same... Are about 33nm, 35nm and 36nm, respectively be changed by sawtooth. Authorship, and/or publication of this article uses the same principle to design the mechanism! Swept excitation method and tested failing edge of the PMP piezoelectric actuator is an in. Actuators because their length can be considered as a Piezo actuator from the corresponding author upon request amplify the of! Modeling are shown in figure 12 ( a ) b ) continuously with repeating the above steps is shown figure! Prototype also worked well when two piezoelectric stacks were installed and applied increases...
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