Shear Piezoelectric Actuators Research Articles

Hybrid controller of a linear piezoelectric walking stage relying on stack/shear piezoelectric actuators

This paper proposes a hybrid control strategy of a novel linear piezoelectric walking stage based on two sorts of piezoelectric actuators, which takes the load variation into account. The proposed stage consists of two parallel 4-bar lever amplification mechanisms with flexure hinges actuated by piezoelectric stacks to heighten the vertical distance (that is more tolerable to the assembly discrepancy), two compression springs (that is able to maintain a fixed linear position without powering), and two shear piezoelectric actuators (that can achieve longer and equivalent to walking motion) in a small form factor. The proposed stage has two operating modes, namely a coarse positioning mode with a more extensive travel range and a fine positioning mode with a nanometer-level resolution, to possess excellent performance for the linear piezoelectric walking stage of load variations. One multimodal switching controller and one feedforward-feedback controller conduct the coarse mode and fine mode, respectively. The optimal frequency for a specific load is obtained through a backpropagation neural network in the multimodal switching control. In the feedforward-feedback control, the inverse mathematical model based on the Bouc-Wen hysteresis model is used to mitigate the hysteresis effect in the feedforward part while the proportional–integral–derivative controller in the feedback part handles the external system disturbances. Experimental results show the proposed hybrid coarse/fine mode control strategy's effectiveness to satisfy an efficient and accurate positioning task.

Study of the effects of shear piezoelectric actuators on the performance of laminated composite shells by an isogeometric approach

This paper presents an isogeometric approach based on the Non-Uniform Rational B-Splines (NURBS) to investigate static and free vibration responses of smart composite shells integrated with shear piezoelectric actuators. The degenerated shell formulation according to the Mindlin-Reissner shell theory is combined with the isogeometric approach. To model the laminated smart shells, the Equivalent Single Layer (ESL) theory is used. To consider the electric potential in the shear piezoelectric actuator layers, a sub-layer approach is adopted that assumes linear variation in the thickness direction of the sub-layer. The effect of different mechanical and electrical boundary conditions on transverse deformation and natural frequencies of laminated smart shells by applying the electric field have been investigated. In the case studies, two parallel edges of the considered shell structures are assumed simply supported and the other two with an arbitrary combination of boundary conditions including clamped, free or simply supports. Also, open-circuit and closed-circuit conditions are used as electric boundary conditions. Investigation of the effects of the shear piezoelectric actuator layers on various factors, including the simultaneous mechanical and electrical loadings as well as the radius of curvature of the shell are amongst the objects of this paper. Also, several numerical examples are presented to demonstrate the efficiency and accuracy of the isogeometric approach in the study of shear effects of the piezoelectric actuator layers. The obtained results indicate the reliability and desirability of the proposed approach.

Design of a Linear Walking Stage based on Two Types of Piezoelectric Actuators

Piezoelectric actuators can generate mechanical deformation under the electric field. Although the deformation is extremely small, piezoelectric actuators have high resolution and large output force, and they can also work at high frequency. In this paper, a compact double-foot linear walking stage based on shear and stack piezoelectric actuators is proposed, which features a large motion range and self-locking ability. The proposed stage achieves a stable movement with high speed, high load capacity and high resolution. The stage consists of a clamping mechanism, a driving mechanism, a linear guide, a preload mechanism, and a fixed base. As the core units, the clamping mechanism and the driving mechanism are actuated by stack and shear piezoelectric actuators, respectively. The statics and dynamical models of the proposed stage are analyzed and verified by finite element analysis and MATLAB/Simulink. A prototype is fabricated, and its performance is also tested through a series of experiments. Experimental results show that the prototype can provide a maximum speed of 28.1 μm/s, a driving force up to 4.9 N, and a fine resolution of 30 nm.

A balanced laminate of piezoelectric fiber composite for improved shear piezoelectric actuation of beams

A new balanced laminate of piezoelectric fiber composite (PFC) is presented for the improved shear mode piezoelectric actuation of beams. A micromechanics formulation is first presented for determination of its effective electromechanical properties, and then its shear actuation capability is investigated by means of utilizing it for actuation of bending deformation of a smart sandwich beam. The results reveal an indicatively higher shear actuation capability of the present balanced laminate of PFC over that of the monolithic shear piezoelectric actuators, and thus this laminate of PFC may be a potential material for shear piezoelectric actuators in control of flexible structures.

A Friction-Inertial-Based Rotary Motor: Design, Modelling and Experiments.

A friction–inertial-based rotary motor driven by shear piezoelectric actuators (SPAs) is proposed in this paper, which possesses many superior features, including high resolution, compact size, large load-capacity, and low cost. In order to eliminate the step loss and increase the step size when an external load is applied, the power-function-shape driving signal was used to actuate the rotary motor. According to the step characteristics under this driving signal, two motion modes were observed and defined, namely the stick-shoot motion mode and the stick-slip-shoot motion mode. The former motion mode can realize a large step size while the later one cannot due to the slipping during the rising phase. After analyzing the results from the numerical simulation and the experiment study, it was found that the motion performance of the motor is closely related to the preload and the base number of the driving signal rather than the size of SPAs, which means the motor can be further downsized according to its actual requirements.

A multilayered-cylindrical piezoelectric shear actuator operating in shear (d15) mode

In this work, a multilayered-cylindrical piezoelectric shear actuator (MCPSA) operating in the d15 shear mode was presented for precision actuation under a large mechanical load. The actuator was made of Pb(Zr,Ti)O3 (PZT-51) piezoelectric ceramic rings, which were concentrically assembled together in electrically parallel connection with alternately positive and negative polarizations along the axial direction. Experimental results show that the acquired displacement amplitude at the center of the actuator along the axial direction is around 6.5 μm under the 1 Hz applied voltage of 400 Vpp/mm, and it stayed stably under a mechanical load up to 18 N, which is 7 times larger than that of the previously reported d15 shear actuator. The proposed actuator also shows good displacement linearity with a high resolution of 0.1 μm in responding to a step voltage, indicating its great potential for precision actuation under a large mechanical load.

Dual Actuation of Fast Scanning Axis for High-speed Atomic Force Microscopy

Abstract In order to overcome the limiting trade-off between the imaging speed and scanning range of an atomic force microscope (AFM), this paper combines two piezoelectric actuators as a dual stage actuator (DSA) for a lateral motion (X axis) of the AFM probe with respect to the sample. As the first actuator, a piezoelectric tube actuator of the commercial AFM is utilized. Although the actuator realizes a relatively large actuation range, it has the first mechanical resonance at a low frequency of 2.5 kHz. In the case of high-speed imaging, this resonance impairs the imaging speed and quality. In order to overcome this, a piezoelectric shear actuator with the first resonance at 19 kHz is selected as the second actuator, combined in the commercial AFM. To generate the X-axis motion by synchronizing those two actuators, this paper proposes a feedforward control design for DSAs in the frequency domain, which takes into account the actuator dynamics. In the proposed approach, triangular raster scan is composed as a Fourier series by individually adjusting the complex Fourier coefficients for each actuator. The effectiveness of the DSA and its control is validated by experimental AFM imaging at a scan rate of 200 Hz, where the lowest frequency component is applied to the tube actuator and the other higher components of the scanning signal to the high-speed shear actuator.

A two-dimensional nano-positioner: Design, modelling and experiments

Abstract In this paper, an X-Y nano-positioner driven by the shear piezoelectric actuators (SPAs) is proposed based on the friction-inertial theory. The nano-positioner can output a two-dimensional motion at a maximum speed of 0.187 mm/s within a 5 mm×5 mm workspace. In order to solve the contradiction between the motion velocity and the motion resolution, the coarse and the fine motion modes are first proposed on the SPAs application. The coarse motion and the fine motion are realized based on the power-function-shaped signal and the combined piecewise-curve signal respectively. The performance of the nano-positioner, e.g. the resolution, the velocity and the fluctuation, are analyzed and discussed based on different driving signals. Compared with other nano-positioners, the proposed system in this paper is superior in respect of compact size, high resolution, high velocity and two switchable motion modes. Furthermore, a prototype system of the proposed nano-positioner has been developed, which is evaluated by using a capacitive sensor based measurement system. Experiment results validate the effectiveness of the proposed methodology that can be employed and extended to a variety of SPA involved systems.

A planar nano-positioner driven by shear piezoelectric actuators

A planar nano-positioner driven by the shear piezoelectric actuators is proposed in this paper based on inertial sliding theory. The performance of the nano-positioner actuated by different driving signals is analyzed and discussed, e.g. the resolution and the average velocity which depend on the frequency, the amplitude and the wave form of the driving curves. Based on the proposed design, a prototype system of the nano-positioner is developed by using a capacitive sensor as the measurement device. The experiment results show that the proposed nano-positioner is capable of outputting two-dimensional motions within an area of 10 mm × 10 mm at a maximum speed of 0.25 mm/s. The corresponding resolution can be as small as 21 nm. The methodology outlined in this paper can be employed and extended to shear piezoelectric actuators involved in high precision positioning systems.

Femtogram aerosol nanoparticle mass sensing utilising vertical silicon nanowire resonators

Vertically aligned silicon nanowire (SiNW)-based resonators were fabricated and utilised to detect aerosol nanoparticles (NPs) by measuring their resonant frequency shifts caused by the additional mass of trapped NPs. Inductively coupled plasma cryogenic dry etching and multiple thermal oxidations are used in the fabrication of silicon nanowire (SiNW) arrays. The SiNWs were coated with gold for contacting to the homebuilt electrostatic NP sampler to collect the flowing NPs. In order to have a dynamic resonance operation in the frequency measurement system, a piezoelectric shear actuator was mounted onto the SiNWs. Examined in a TiO 2 aerosol sampling with a total concentration of ~8500 NP/cm 3 , the fabricated sensor exhibited its feasibility as a nanobalance to measure aerosol NP mass at the femtogram level with a mass sensitivity of 7.1 Hz/fg and a mass resolution of 31.6 fg. The NP sampling efficiency of the developed miniaturised NP sampler was found to be three times higher than that of the commercial nanometer aerosol sampler (NAS, TSI 3089). An ultrasonic removal method was used to detach the adhered NPs and further extend the operating life of the sensor.

Silicon Nanowire Resonators: Aerosol Nanoparticle Mass Sensing in the Workplace

In this article, We focus on silicon nanowire (SiNW)-based resonators that were fabricated and employed to sense aerosol nanoparticles (NPs) by measuring resonant frequency shifts induced by the mass of stuck NPs. The fabrication of SiNW arrays was performed using inductively coupled plasma (ICP) cryogenic dry etching and multiple thermal oxidations. The SiNWs were coated with gold (Au) for contacting to the homebuilt electrostatic NP sampler to collect the flowing NPs. A piezoelectric shear actuator mounted in the frequency measurement system was used to excite the SiNW sensors into resonance. Tested in a titanium dioxide (TiO2) aerosol sampling with a total concentration of ~8,500 NPs/cm3, the sensor displayed its feasibility as a nanobalance to detect aerosol NPs in the femtogram scale with a mass sensitivity of 7.1 Hz/fg and a mass resolution of 31.6 fg. To extend the operating life of the sensor, an ultrasonic removal method was used to detach the adhered NPs.

Analytical investigation of laminated arches with extension and shear piezoelectric actuators

Static deformations in symmetric and antisymmetric cross-ply laminated arches with extension and shear piezoelectric actuators are investigated. The state space approach is used to generate exact solutions for the static response of cross-ply smart arches for arbitrary boundary conditions. A rigorous first order shear deformation arch theory is used in the analysis. Deflections are computed for thirty layer arches with various lamination schemes and boundary conditions incorporating piezoelectric actuators. The feasibility of using extension and shear mode actuators in smart arches is investigated. It is observed that an antisymmetric cross ply cantilever arch with a shear piezoelectric actuator provides twice tip deflection more than that with extension piezoelectric actuators. ► Static response in cross ply smart arches is investigated. ► The state space is used to find exact response for arbitrary boundary conditions. ► A rigorous first order shear deformation arch theory is used in the analysis. ► Deflections are computed for arches with extension and shear piezoelectric actuators.

Analysis of smart cross ply laminated shells with shear piezoelectric actuators

Analytical models and solutions are formulated and developed for the static responses ofcross ply smart laminated shells with shear piezoelectric actuators. The models are basedon a rigorous first-order shell theory. The state-space approach is used to findexact solutions for the static responses of cross ply spherical, cylindrical anddoubly curved shells with various boundary conditions. The smart shells possesstwo parallel edges simply supported and the remaining ones having any possiblecombination of boundary conditions: free, clamped or simply supported. Deflections ofcross ply laminated shells incorporating shear piezoelectric layers are determined.Numerical results for six layer laminates are generated to investigate the shells’static behavior. The exact solutions for deflections can be used as benchmarksfor approximate solutions such as Rayleigh–Ritz and finite element methods.

Vibration Control of a Space Flexible Robot Manipulator Using PZT Actuators

The dynamic analysis and control of flexible robot manipulators have been the main concerns of many recent studies in aeronautics and robotics. Moreover, the complexity of this problem increases when a flexible manipulator carries a payload. In this paper, we proposed a space two-link flexible manipulator with tip payload featuring surface-bonded piezoelectric torsional actuator and shear actuator. The equations of motion for the system are obtained using Hamilton’s principle. A Lyapunov-based controller is proposed to suppress the vibration of the system. Stability of the system is also investigated. The simulation results demonstrate the proposed control strategy is well suited for active control of vibration suppression on flexible manipulators.

Control of torsional vibrations in piezolaminated rods

This paper is concerned with active control of torsional vibrations in laminated rods by piezoelectric shear sensors and actuators. A piezoelectric layer can be used as a sensor by utilizing the direct piezoelectric effect, measuring either the charge on short-circuited electrodes or the voltage on open electrodes. On the other hand, the converse piezoelectric effect enables actuation by applying an electric potential difference to the electrodes of a piezoelectric layer. The sensor and actuator equations are formulated in the framework of an extended Saint-Venant torsion theory considering additional cross-sectional warping due to piezoelectric eigenstrains. A solution of the shape control problem for torsional vibrations is presented, i.e. the necessary distribution of actuation strains in order to completely compensate vibrations caused by external excitations. For the case, in which the external excitations are not known exactly, a feedback control solution is presented using one piezoelectric layer as a sensor and a second one as an actuator. For the examples of a rectangular and a circular cross-section, the theoretical results are validated by three-dimensional finite element computations, showing a very good coincidence. Copyright © 2011 John Wiley & Sons, Ltd.

Compensation of torsional vibrations in rods by piezoelectric actuation

In this paper, the piezoelectric compensation of torsional vibrations in rods caused by external excitations is studied. As an illustrative example, a laminated rod containing piezoelectric shear actuators is assumed to be fixed at the one end, and the other end is subjected to a torsional couple; additionally, a distributed torsional couple per unit length is acting. In such a system, cross-sectional warping is known to be present. The consideration of piezoelectric eigenstrains requires an extension of Saint Venant’s theory of torsion, which is achieved by introducing an additional warping function. Using D’Alembert’s principle, the boundary value problems for Saint Venant’s warping function, the additional warping function and the torsional angle are obtained. From the latter boundary value problems, the distribution of piezoelectric actuation is derived in order to completely compensate the external excitations, i.e. an analytical solution of the corresponding shape control problem is obtained. Finally, the results are verified by means of three-dimensional finite element computations.

Multimodal passive vibration control of sandwich beams with shunted shear piezoelectricmaterials

This work presents a performance analysis of multimodal passive vibration control of asandwich beam using shear piezoelectric materials, embedded in a sandwich beam core,connected to independent resistive shunt circuits. Shear piezoelectric actuators wererecently shown to be more interesting for higher frequencies and stiffer structures. Inparticular, for shunted damping, it was shown that equivalent material loss factors of up to31% can be achieved by optimizing the shunt circuit. In the present work, special attentionis given to the design of multimodal vibration control through independent shunted shearpiezoelectric sensors. In particular, a parametric analysis is performed to evaluateoptimal configurations for a set of modes to be damped. Then, a methodology toevaluate the modal damping resulting from each shunted piezoelectric sensoris presented using the modal strain energy method. Results show that modaldamping factors of 1%–2% can be obtained for three selected vibration modes.

Vibration Suppression of Timoshenko Beams with Embedded Piezoelectrics Using POF

Abstract —This paper deals with the design of a periodic output feedback controller for a flexible beam structure modeled with Timoshenko beam theory, Finite Element Method, State space methods and embedded piezoelectrics concept. The first 3 modes are considered in modeling the beam. The main objective of this work is to control the vibrations of the beam when subjected to an external force. Shear piezoelectric sensors and actuators are embedded into the top and bottom layers of a flexible aluminum beam structure, thus making it intelligent and self-adaptive. The composite beam is divided into 5 finite elements and the control actuator is placed at finite element position 1, whereas the sensor is varied from position 2 to 5, i.e., from the nearby fixed end to the free end. 4 state space SISO models are thus developed. Periodic Output Feedback (POF) Controllers are designed for the 4 SISO models of the same plant to control the flexural vibrations. The effect of placing the sensor at different locations on the beam is observed and the performance of the controller is evaluated for vibration control. Conclusions are finally drawn.

Refined sandwich model for the vibration of beams with embedded shear piezoelectric actuators and sensors

This work extends a previously presented refined sandwich beam finite element (FE) model to vibration analysis, including dynamic piezoelectric actuation and sensing. The mechanical model is a refinement of the classical sandwich theory (CST), for which the core is modelled with a third-order shear deformation theory (TSDT). The FE model is developed considering, through the beam length, electrically: constant voltage for piezoelectric layers and quadratic third-order variable of the electric potential in the core, while mechanically: linear axial displacement, quadratic bending rotation of the core and cubic transverse displacement of the sandwich beam. Despite the refinement of mechanical and electric behaviours of the piezoelectric core, the model leads to the same number of degrees of freedom as the previous CST one due to a two-step static condensation of the internal dof (bending rotation and core electric potential third-order variable). The results obtained with the proposed FE model are compared to available numerical, analytical and experimental ones. Results confirm that the TSDT and the induced cubic electric potential yield an extra stiffness to the sandwich beam.

Dynamic response and active control of a composite cylindrical shell with piezoelectricshear actuators

This paper presents exact solutions of the dynamic responses of a fully coupled hybridpiezoelastic cylindrical shell with piezoelectric shear actuators (PSAs). The fundamentalresponse quantities of each layer in the shell are expanded into a double Fourier series. Astate-space method is used to represent the response quantities using eight first-orderhomogeneous ordinary differential equations with variable coefficients. The solutions arethen obtained by the Frobenius method. Numerical examples are presented to show theeffects of thickness ratio and location of PSAs on the transverse response of the shellsubjected to mechanical and electric loadings. Finally, an active vibration control model fora simply supported laminated cylindrical shell with piezoelectric shear sensorand actuator layers is established using the negative velocity feedback controlstrategy. Numerical results are presented to verify the feasibility of the controlmodel.