Search Results (516)

Regenerative vibrations are a major hindrance to flexible cantilever structures during milling, resulting in a reduced tool life and diminished surface finish. In this research, two actively controlled methods are directly compared: a genetic algorithm (GA)-optimized classical proportional-integral-derivative (PID) controller and a GA-optimized fractional-order PID (FOPID) controller for a milling-dependent regenerative force on a flexible cantilever beam via numerical modeling, using piezoelectric actuator/sensor patches. The original aspect lies in synergistically combining fractional-order control with genetic algorithm-based optimization to actively reduce chatter and increase the machining stability of flexible milling systems. The simulation results from the GA-FOPID controller exhibited a reduction in vibration of approximately 92.70% compared with the open-loop system by reducing the RMS value from 1.5058 × 10⁻⁴ m to 1.0996 × 10⁻⁵ m. By reducing the vibration level and enlarging the predicted stable machining region, these improvements could potentially contribute to longer tool life, improved surface finish, and reduced post-processing requirements, although these technological benefits were not directly modeled in the present study. The main innovation of this work involves a unique combination of fractional-order control, PZT actuation, and genetic algorithm optimization in a regenerative milling delay architecture. To the best of the authors’ knowledge, based on the literature surveyed in this work, this combination of techniques has not previously been reported for active chatter suppression. The stability lobe diagram (SLD) analysis, conducted under the single-mode approximation that serves as the reference framework for the like-for-like comparison of the five investigated configurations, shows that the critical axial depth of cut at the representative spindle speed increases from a_p,crit(1500) = 0.061 mm for the uncontrolled system to 0.52 mm under GA-FOPID control. This enlargement of the predicted stable machining region was further confirmed, at a comparable order of magnitude, when the structural model was extended to include the two next bending modes, indicating that the trend is not an artifact of the single-mode simplification. Therefore, although the results were obtained exclusively from numerical simulation and have not yet been experimentally validated, they support the use of optimization-based methods to implement FOPID strategies as a means to increase both reliability and performance of flexible milling configurations. Full article

Vibration-based piezoelectric energy harvesting provides a potential power source for low-consumption devices; however, its prediction requires a consistent representation of localized structural properties and experimentally identified modal behavior. This study presents the structural and modal qualification of an analytical electromechanical model for a 6061-T6 aluminum cantilever beam carrying a finite one-sided PZT-5J piezoelectric patch, with unequal beam and patch widths, under base excitation. The specific contribution is the traceable integration of local neutral-axis relocation, spatially varying mass and flexural rigidity, a finite-patch indicator function, $d_{31}$ electromechanical coupling, multimodal projection, and mode-specific reduced-order equations. Two beam lengths, $275$ and $250 \mathrm{m}\mathrm{m}$, were investigated using broadband shaker excitation, accelerometry, and scanning laser vibrometry. The measured first and second bending frequencies were $16.56$ and $110.31 \mathrm{H}\mathrm{z}$ for the $275 \mathrm{m}\mathrm{m}$ beam and $19.14$ and $125.00 \mathrm{H}\mathrm{z}$ for the $250 \mathrm{m}\mathrm{m}$ beam. Experimental damping ratios obtained from the frequency-response functions ranged from $6.54\times {10}^{-3}$ to $1.55\times {10}^{-2}$. The analytical formulation reproduced the increase in modal frequencies produced by reducing the beam length and captured the measured transverse mode-shape trends. Experimentally identified frequencies, base accelerations, and damping ratios were subsequently introduced into the reduced model to obtain experimentally parameterized model outputs. The largest calculated peak voltage and estimated average electrical power were $155.99 \mathrm{m}\mathrm{V}$ and $1.22 \mathsf{\mu }\mathrm{W}$, respectively, for the first mode of the $275 \mathrm{m}\mathrm{m}$ beam across a reference $10 \mathrm{k}\mathsf{\Omega }$ resistive load. The reported qualification is restricted to the structural and modal response of the two tested configurations; the electrical quantities are calculated outputs rather than independent electrical measurements. Full article

This paper develops a reduced-order electromechanical model for piezoelectric energy harvesting from a beam traversed by a moving mass. The beam is described by the Euler–Bernoulli theory, and the coupled equations of motion are derived through modal expansion combined with the linear piezoelectric constitutive relations. Unlike most existing formulations, the model accounts for non-uniform transit by including moving-mass acceleration, accommodates an arbitrary number of piezoelectric patches distributed along the span, and incorporates von Kármán strain–displacement relations. So, moderately large deflections and mid-plane stretching as well as various boundary conditions may be investigated within the same framework. The resulting coupled nonlinear ordinary differential equations are integrated in time using a numerical solver. On the other hand, predictions of midpoint deflection, output voltage, and harvested power are validated against the COMSOL Multiphysics Finite element model. The experimental setup has been established, and a dedicated laboratory experiment provides additional verification under controlled conditions. Parametric analyses investigating the individual and combined effects of the mass ratio, velocity ratio, acceleration profile, patch length, patch position, number of patches, and external load resistance are elaborated. Distributed multi-patch configurations are shown to recover more energy than a single-centered patch once higher modes contribute appreciably to the response. Design charts relating the governing parameters to the harvested power are constructed for each set of support conditions. These results are intended to assist the preliminary sizing and placement of piezoelectric transducers on some practical energy harvesting applications. Full article

Pyropiezoelectric energy harvesting has the potential to utilize both environmental vibrations and time-dependent temperature changes to increase the amount of energy harvested compared to harvesting from only one of the two sources. So far, the investigation of such hybrid energy harvesting approaches has mainly been experimental. This makes it difficult to distinguish between their individual physical effects and complicates the optimization of such harvesters. This work presents a numerical framework for solving transient coupled pyropiezoelectric equations using the finite element method. The numerical method can be applied to simulate hybrid energy harvesters by taking into account external electrical circuits. The numerical simulations enable a targeted analysis of the contributions of mechanical, electrical and thermal effects to the harvested energy. This is illustrated by various numerical examples, such as a simple piezoelectric cuboid, a unimorph, a bimorph and a bimetallic beam with a piezoelectric patch. These are subjected to oscillating deformations and/or temperature changes. The simulations calculate the harvested energy resulting from the individual physical effects, depending on the excitation frequency, the external resistance, and the geometric configuration of the harvester. For a bimetallic beam with a piezoelectric patch, which is used as a low frequency hybrid energy harvester, a geometric optimization based on the simulation results showed a possible increase in the harvested energy of up to 386% under idealized circuit conditions compared to the initial design from the literature. Full article

Multistable energy harvesters have attracted considerable attention due to their shallow potential wells, which facilitate low-energy inter-well oscillations. Although bistable or tristable configurations can be realized using combined magnets or springs, two critical challenges remain: (i) the difficulty in obtaining a higher number of stable equilibrium points and (ii) the inability to arbitrarily prescribe the coordinates of these equilibrium points. To address these issues, this paper proposes a piezoelectric cantilever beam-based multistable energy harvester that allows programmable specification of both the number and the positions of equilibrium points. As demonstrations, a tristable and a pentastable energy harvester with user-defined equilibrium coordinates are designed, and their energy harvesting performances are systematically investigated. Simulation and experimental results show that under an excitation acceleration of 0.1 g, both harvesters can only perform intra-well motion, exhibiting softening nonlinearity. When the excitation acceleration increases to 0.2 g, the pentastable harvester successfully overcomes the maximum potential barrier to achieve inter-well oscillation, displaying hardening nonlinearity and significantly broadening the operational bandwidth, while the tristable harvester remains confined to intra-well motion. At an excitation acceleration of 0.4 g, both harvesters can achieve inter-well oscillation, but the pentastable harvester possesses a wider operational bandwidth and a lower starting frequency for energy harvesting. The proposed method enables the design of multistable vibration energy harvesters without increasing structural complexity with the number of equilibrium points, which is of great significance for optimizing multistable vibration energy harvesters. Full article

Vibration energy technology holds promise for self-powered miniature wireless sensor devices in underground coal mines. This study proposes a magnetically coupled bistable composite-beam wind energy harvester (BCBWEH) to enhance the response threshold for harvesting weak ambient wind energy. A nonlinear magnetic model based on magnetic dipoles is established, and the system’s dynamic equations are formulated using the lumped parameter method. Numerical simulations analyze the effect of magnetic spacing on static bifurcation, and discuss the influences of initial static position, wind excitation, and magnetic moment on the system’s dynamic behavior; experimental results validate the accuracy of the numerical predictions. By adjusting the magnetic spacing under the same level of excitation, the system’s motion can transition from single-well oscillation to efficient inter-well vibration. When the initial position lies closer to the shallower potential well, relatively small wind excitation can trigger large-amplitude inter-well vibrations, thereby increasing output power. This study offers guidance for optimizing structural configurations and tuning design parameters of piezoelectric energy harvesters based on composite-beam architectures. Full article

Piezoelectric cantilever beams are among the most popular vibration energy harvesting devices. Maximization of the spatial distribution of axial strain along this beam (objective function) increases harvesting efficiency. In vibro-impact systems, mechanical contact can excite higher-order vibration modes, making the second eigenfrequency particularly relevant for energy harvesting under such nonlinear operating conditions. Therefore, the harvester geometry should be designed to maximize the harvested energy associated with this mode. In many practical applications, cantilever-based harvesters are subjected to complex and broadband excitation conditions, where multiple vibration modes, including the second eigenfrequency, contribute to the overall response. Therefore, optimization at the second eigenfrequency is essential for improving energy harvesting performance under realistic operating conditions. In this study, to maximize axial strain, a thickness shape optimal design is proposed, and a finite element-based optimization scheme is constructed to maximize harvesting efficiency. Optimization is performed subject to a fixed second eigenfrequency of the cantilever beam, using the eigenmode equation as the state equation in the optimization procedure. The optimized shape for maximal strain integral at the second bending resonance is determined. Experimental results validate the findings of the optimization, showing an increase in strain for the optimized-shaped beam compared to a uniform-thickness beam with the same eigenfrequency. It should be noted that experimental validation is subject to certain limitations, including manufacturing precision and environmental influences. The manufacturing of specimens can only be achieved within a limited precision, resulting in deviations from the ideal optimized geometry. Additionally, the experimental environment may influence the measured response, and simplified boundary conditions can introduce discrepancies between numerical and experimental results. Full article

Severe shocks and vibrations are common in industrial settings (such as oil drilling at 200–300 °C and heavy machinery); high-temperature piezoelectric gyroscopes’ solid-state architecture provides remarkable shock and vibration tolerance as well as great reliability. This review covers the most recent advances in the creation of high-temperature piezoelectric gyroscopes from three angles: materials, structural design, and circuit design. First, it emphasises how optimising microstructures can greatly improve the materials’ temperature stability (e.g., PZT with d₃₃ = 562 pC/N and LiNbO₃ with Curie temperature ~1210 °C) and piezoelectric coefficient; second, it examines the structural design of piezoelectric gyroscopes based on MEMS/NEMS technology (such as disc-type, ring-type, and beam-type), showing that optimising resonance frequency matching and modal isolation techniques greatly improves the gyroscope’s zero-bias stability (down to 5°/h) and immunity to interference; and third, it summarises the efficacy of optimisation techniques like temperature self-compensation circuit design and structural symmetry design. According to research, problems like high-temperature material ageing (e.g., degradation above 120 °C for silicon-based devices) and the difficulty of system integration continue to limit current technology; in the future, performance bottlenecks will need to be removed through advancements in cross-scale manufacturing technologies and intelligent sensor fusion design. From a multidisciplinary standpoint, this study offers theoretical references and technical recommendations for the industrial use of high-temperature piezoelectric gyroscopes. Full article

Precision tilt stages capable of high angular resolution and low cross-axis coupling are essential for applications such as free-space optical communication, adaptive optics, and micro/nano-positioning. In this study, a two-degree-of-freedom compliant tilt stage based on differential actuation of positive and negative Poisson’s ratio folded-beam structures is proposed. The stage incorporates four circumferential compliant motion units, each consisting of a W-shaped positive Poisson’s ratio folded beam, an M-shaped negative Poisson’s ratio folded beam, a lever amplification mechanism, and compliant decoupling leaf springs. By exploiting the opposite out-of-plane deformation tendencies of the two folded-beam types under identical input forces, a push–pull differential driving effect is generated, enabling independent tilting motion about two orthogonal axes with enhanced angular output. The lever amplification mechanisms enlarge the small displacement of the piezoelectric actuators, while the decoupling leaf springs suppress parasitic motion and reduce cross-axis coupling. A static analytical model is established based on compliance analysis and force–moment equilibrium. The model predictions are validated through finite element analysis, with errors of 4.77% and 4.80% for the two axes, respectively. Experimental results obtained from a stereolithography-fabricated prototype demonstrate maximum tilt angles of 9.19 mrad and 8.80 mrad about the x- and y-axes under a 150 V driving voltage, while the corresponding coupling angles are only 0.043 mrad and 0.040 mrad, yielding coupling ratios below 0.5%. The proposed design achieves a favorable combination of compact monolithic structure, effective displacement amplification, and excellent decoupling performance, offering a practical solution for precision optical adjustment, beam steering, and micro/nano-positioning systems. Full article

Metasurfaces have emerged as a powerful platform for subwavelength light manipulation, attracting widespread interest for their potential to replace bulky optical components. However, most metasurfaces are statically designed with fixed functionalities. Here, we demonstrate a high-efficiency tunable meta-waveplate by heterogeneously integrating a phase-change Sb₂Se₃ layer with a piezoelectric MEMS mirror. Leveraging the reversible amorphous–crystalline transition of Sb₂Se₃, combined with MEMS-enabled nanoscale air gap tuning, the metasurface achieves dynamic switching among zero-, half-, and quarter-waveplate functionalities at the communication wavelength of 1550 nm. The device exhibits stable polarization conversion performance under various rotation angles. Furthermore, we developed a nano-quarter-waveplate library on this platform, which provides extensive phase control over the reflected field and enables programmable beam deflection. This tunable architecture opens new avenues for adaptive photonics with dynamically switchable functionalities. Full article

Deep learning networks facilitate automated metal material/structural stress identification when employing the electromechanical impedance/admittance (EMI/EMA) of piezoelectric ceramic (PZT) transducers, while insufficient data quantity and low quality usually restrict the performance of data-driven deep networks. To address this problem, this paper innovatively proposed an original data enhancement method using the EMA generative adversarial network (EMAGAN) to overcome measurement data inefficiency and deficiency for deep learning-based stress identification, which is difficult to accomplish using the traditional EMA technique. In this method, a novel data-normalized algorithm was tuned to collaboratively foster the EMAGAN-based dataset generation. Then, the synthetic datasets incorporated with original ones were fed into an adaptively established one-dimensional convolutional neural network (1DCNN) for accurate stress prediction. A validating experiment was performed on an aluminum beam specimen subjected to uniaxial tensile load until failure, which was continuously monitored via two surface-bonded PZT transducers. The efficacy of the generated EMA datasets was evaluated through comparison with the raw ones in terms of statistical errors and deep learning-based aluminum structural stress identification. The results demonstrated that the EMAGAN generated high-accuracy EMA data which exceeded 380 times that of the normal collection method, and the EMAGAN paired with 1DCNN provides a promising way for EMA data-driven metal structural stress identification with high efficiency, intelligence and accuracy. Full article

Real-time monitoring of surface cracks in reinforced concrete (RC) beams is critical to structural safety and service performance evaluation. Current structural crack monitoring still faces prominent scientific and technical bottlenecks: conventional unidirectional sensors cannot achieve multi-directional collaborative sensing, rigid piezoelectric materials exhibit poor compatibility with the large deformation of concrete, and there is a lack of quantitative mapping relationships from sensing signals to crack parameters, making it difficult to simultaneously measure crack width, angle, and morphology. This paper presents a novel ring-shaped piezoelectric sensor based on polyvinylidene fluoride (PVDF) and an annular piezoelectric sensing mechanism for real-time monitoring of crack angle, width, and morphology. The sensor incorporates a laminated structure with four strip sensing units for multi-directional strain detection. Experiments were conducted on RC beams under various loading conditions, and finite element analysis was performed using COMSOL Multiphysics. An innovative crack damage index (B) was introduced to assess structural damage quantitatively. Results demonstrate high sensor sensitivity and stable output. Voltage signals increase both with crack width and crack angle, showing responses of 0.045 mV, 0.041 mV, and 0.023 mV for crack angles of 60°, 45°, and 30°, respectively, at a crack width of 9 mm. Strong consistency between experimental and simulation data validates the effectiveness of the mechanism in monitoring the direction, width, and types of cracks. The crack damage index B exhibits a positive correlation with the structural stress response, enabling a quantitative assessment of damage. This study is applicable to the prestressed concrete box girders and T-beams commonly used in large-span bridges, which are typically with a main span of 20–50 m, a beam length of 6–30 m, a section height of 1.2–2.5 m, and designed for Grade C35–C50 concrete. The findings provide a practical foundation for real-time crack monitoring in large-scale bridge beam members. Full article

This paper presents a numerical investigation into a prototype energy harvesting system utilizing airflow around a bluff-body. The system consists of a flexible cantilever beam in a flag configuration with bonded piezoelectric transducers, integrated with a nonlinear triple-well potential established by auxiliary elastic elements. Three distinct bluff-body geometries—triangular, square, and semi-circular—with characteristic heights of 20 mm and 30 mm were analyzed. Aerodynamic excitation parameters were identified using CFD simulations, comparing exact and simplified mathematical representations of the lift force. The system’s dynamical response was evaluated through bifurcation diagrams, Diagrams of Coexisting Solutions (DS), and 3D Poincaré sections for zero and variable initial conditions. The results indicate that the triangular cross-section provides the widest frequency band for high-amplitude inter-well oscillations, maximizing energy harvesting effectiveness. A key innovation of this study is the demonstration that the simplified excitation model provides sufficient accuracy for rapid engineering design while significantly reducing computational overhead. Furthermore, it highlights the practical applicability of a flag-type system integrated with flexible elements to stabilize the beam’s free end. Full article

Resonant electromechanical de-icing uses piezoelectric actuators to generate stresses high enough to fracture and shed ice, offering an energy-efficient alternative to conventional systems. This work focuses on prestressed piezoelectric actuators composed of a ceramic stack clamped between two brackets, addressing limitations of previous designs such as mechanical losses and screw fatigue. A new architecture is proposed, featuring a variable-cross-section screw that concentrates deformation in a thinned central region and brackets bonded to the structure to reduce losses. An analytical sizing method is developed using multi-beam longitudinal vibration modelling and two de-icing criteria, including a newly introduced one. The analysis shows how actuator geometry and modal shapes influence de-icing performance, required voltage, and mechanical stresses, highlighting key trade-offs. A dedicated prototype is designed and experimentally tested, with results in good agreement with the analytical predictions. Full article

High-frequency surface acoustic wave (SAW) devices require piezoelectric thin films combining strong electromechanical coupling, high acoustic velocity, and compatibility with scalable fabrication. Lithium niobate (LiNbO₃) is a promising material, but the growth of high-quality thin films remains challenging because of lithium volatility and process-control issues. In this work, chemical beam epitaxy (CBE) was investigated as an alternative route for the deposition of c-axis-oriented LiNbO₃ thin films on C-plane sapphire at a relatively low growth temperature of 400 °C. Structural characterization confirmed high crystalline quality, with clear (006) and (0012) XRD reflections and a rocking-curve full width at half maximum of 0.04°. To evaluate acoustic performance, a SAW delay line and a one-port resonator were fabricated on 350 nm thick films using e-beam lithography. The devices operated in the 1–3 GHz range and exhibited electromechanical coupling factors of about 0.3% for the Rayleigh mode at 1.7 GHz and 3% for the Sezawa mode at 2.75 GHz. Propagation velocities ranged from 5094 to 8250 m/s, and the Rayleigh-mode resonator quality factor reached about 500. These results demonstrate the feasibility of CBE-grown LiNbO₃ films for SAW device applications. Full article