Macro Fiber Composite Research Articles

Active compound shape/vibration control of piezo-actuated variable camber wing section via hybrid feedback/feedforward control scheme

The new concept of compliant morphing wings with piezoelectric conformal actuators has presented its unique advantages compared with rigid morphing wings, but it has also brought a new challenge to design and control. In this study, a compound shape/vibration control strategy for one kind of piezocomposite actuated wing with variable camber is proposed with the purpose to realize a fast, smooth shape morphing process, while overcoming epiphytic vibration problems due to the necessary structural flexibility. A piezo-actuated variable trailing edge wing section was designed by using a compliant corrugated structure installed with actuators made of Macro Fiber Composite (MFC). A compound shape/vibration control system was designed in terms of active disturbance rejection control (ADRC) strategy combined with a feedforward compensator for the MFC actuators to eliminate the nonlinear hysteretic/creep issues. An experimental device was established for verification. The experimental results show that rapid, accurate shape morphing can be achieved with the proposed hybrid feedforward/feedback control scheme while suppressing structural vibration. The compound control of low-frequency shape control and high-frequency vibration suppression can be synergistically realized, and the deformation and stability while controlling such compliant morphing wings can be properly balanced. The proposed compound control strategy is a feasible way to realize favorable dynamic control performance of compliant morphing wings in the future.

Development and Evaluation of Vibration Canceling System Utilizing Macro-Fiber Composites (MFCs) and Long Short-Term Memory (LSTM) Vibration Prediction AI Algorithms for Road Driving Vibrations.

This study developed an innovative active vibration canceling (AVC) system designed to mitigate non-periodic vibrations during road driving to enhance passenger comfort. The macro-fiber composite (MFC) used in the system is a smart material that is flexible, soft, lightweight, and applicable in many fields as a dual-purpose sensor and actuator. The target vibrations are road vibration data that were collected while driving on standard urban (Seoul) and highway roads at 40 km/s. To predict and cancel the target vibration accurately before passing it, we modeled the vibration prediction algorithm using a long short-term memory recurrent neural network (LSTM RNN). We regenerated vibrations on Seoul and highway roads at 40 km/s using MFCs and measured the displacements of the measured, predicted, and AVC vibrations of each road condition. To evaluate the vibration, we computed the root mean squared error (RMSE) and compared standard deviation (SD) values. The accuracies of LSTM RNN vibration prediction algorithms are 97.27% and 96.36% on Seoul roads and highway roads, respectively, at 40 km/s. Although the vibration ratio compared with the AVC results are different, there was no difference between the values of the AVC vibrations. According to a previous study and the principle of the AVC system, the target vibrations decrease by canceling the inverse vibration of the MFC actuator.

Fracture behavior of composite piezoelectric intelligent structures formed by pasting MFC based on serial multi-scale method

The composite piezoelectric intelligent structures formed by combining piezoelectric materials with composite materials can achieve state perception and deformation control of the structure. Based on the molecular dynamics method, the continuum finite element method and the cohesive force model, the serial multi-scale research on the bonded composite piezoelectric intelligent structure was carried out from the micro, meso and macro scales. Molecular models of adhesive, macro fiber composite (MFC) surface and composite surface were established. The effects of temperature and pressure on the surface interaction energy of adhesive/MFC and adhesive/composite materials were analyzed. The traction-separation (T-S) relationship of cohesive region was obtained by virtual stretching method. Combined with the microscopic observation of the mesoscopic adhesive layer, the representative volume element (RVE) model of the mesoscopic adhesive layer considering the bubble defect was established, and the cohesive relationship curve of the adhesive layer was obtained. A double cantilever beam (DCB) macro finite element model was established to simulate the crack propagation behavior of the adhesive layer, and compared with the experimental results.

Subsonic aeroelastic behaviors of a composite plate with embedded MFC actuators under hygrothermal environment

Subsonic aeroelastic effects of train-body skin structures have been intensely attractive among researchers due to the improvement of high-speed train speed. In this article, the aeroelastic behaviors of a laminated composite plate with embedded Macro Fiber Composite (MFC) actuators in hygrothermal environment under the subsonic airflow has been investigated. The Von Karman large deflection theory and the subsonic aerodynamic model based on the Bernoulli's equation are applied in the formulation. The principle of virtual work is adopted to obtain the nonlinear aeroelastic equations of the laminated composite panel with embedded MFC actuators. Subsequently, the Newmark method and Newton-Raphson method are combined to solve the framework in order to capture the nonlinear aeroelastic response of the subsonic laminated panel in time domain. Since the presence of moisture concentrations, temperature rises and applied voltages of the embedded MFC actuators will result in additional stiffness effects on composite panels by inducing prestress, thus change the aeroelastic behaviors of the composite panel, the influences of these main parameters on aeroelastic performance are analyzed. The results show that the aeroelastic flutter velocity of the composite panel gets remarkably deteriorated due to the adverse hygrothermal environment and can be strengthened through the applied voltages and appropriate lamination angles of embedded MFC actuators. Besides, the main findings of this study are the anti-symmetric laminate buckles then changes to an periodic oscillation like the limit-cycle-oscillation while there is no such phenomenon for the symmetric ones.

Underwater dynamic modeling and experiments of flexible structure with harmonic actuation of macro fiber composites

Flexible structures driven by smart actuators are promising alternatives for aquatic bionic propulsion vehicles. However, the hydrodynamic effects induced by viscous fluids on the dynamic response of flexible structures remain an ongoing challenge. Thus, this article presents a fluid-structure interaction dynamic model of a flexible underwater structure actuated by macro fiber composite actuators, and the underwater multimodal vibration characteristics are studied. The model is based on the extended Hamilton’s principle, which considers the effects of hydrodynamic forces. The segmented mode shape functions of the flexible structure are derived using the assumed mode method. The study shows that the first two mode shapes of the beam predicted by the model agrees with the experimental results. The underwater dynamic responses of the flexible structure in a board band covering the first two resonance frequencies are also investigated at different actuation levels. The underwater results indicate that the first two resonance frequencies are 1.05 and 6.1 Hz respectively, basically consistent with the simulation ones (1.07 and 6.61 Hz). Correspondingly, the maximum transverse deflections at the end of the beam are 4.81 and 1.31 mm respectively, which are slightly lower than the predicted values of 5.75 and 1.62 mm. Therefore, the validity of the proposed coupled dynamic model is verified, which can be utilized to predict the multimodal dynamic responses of underwater flexible structures actuated by MFC or other smart actuators.

Modeling and analysis of a macro-fiber piezoelectric bimorph energy harvester operating in d33-Mode using Timoshenko theory

Piezoelectric bimorph cantilevered beams are frequently employed in energy harvesting applications. The use of macro-fiber composites, which combine piezoelectric fibers with rectangular cross-sections and interdigitated electrodes, has significantly enhanced their performance by enabling operation in the 33-mode of piezoelectricity, thereby increasing conversion efficiency. In this article, the Timoshenko beam theory is applied to overcome the limitations of the Euler-Bernoulli theory in modeling transverse vibrations of harvesters with low slenderness ratios (length to thickness ratios). The mixture rule formulation is applied to determine the equivalent properties of the macro-fiber composite (MFC) structure. The electromechanical properties of a representative volume element (RVE) bounded by two successive interdigitated electrodes are coupled to the overall electro-elastic dynamic model of the structure using the Timoshenko theory. Frequency response functions for the power and tip vibration displacement of the MFC bimorph beam are determined from the model. Experimental data from the literature are used to validate the improved results predicted by the model developed in this article. A comparative analysis between the electromechanical responses predicted using a model based on Timoshenko and a model based on Euler-Bernoulli theory is conducted showing agreement, for harvesters with large slenderness ratios and discrepancies of up to 30% for low slenderness ratios. It has also been shown that the model based on Euler-Bernoulli theory overestimates both the mechanical and the electrical responses for low slenderness ratios as the shear and rotary inertia effects are not negligible in this case.

Dynamic hysteresis compensation and iterative learning control for underwater flexible structures actuated by macro fiber composites

Studies on the hydrodynamics of underwater flexible structures are gaining significant attention. To improve the performance and stability of underwater flexible structures in complex water environments, new control strategies must be proposed. This study proposes underwater rate-dependent hysteresis compensation and iterative learning control (ILC) of the flexible structure actuated by macro fiber composites (MFC). The underwater rate-dependent hysteresis model of the MFC partially-actuated structure consists of two components: a modal state space model characterizing the underwater rate-dependent behavior, and a modified Prandtl–Ishlinskii (MPI) model describing the bias bipolar hysteresis. The MPI model is combined with a PI and a polynomial model of fractional orders. To obtain a unique analytic inverse model, constraints for the inverse are proposed. Results show the varying bias ellipse-like hysteresis behaviors are well captured. Tracking performances are greatly improved with the feedforward compensator. Furthermore, an ILC is developed to address model uncertainties and unsteady hydrodynamics. The convergence and robustness of the ILC are discussed. Parameters of the zero-phase and learning filters are determined. Experimental results demonstrate the tracking errors of the underwater structure are significantly reduced. These findings are meaningful for the realization of flexible structures for marine engineering, underwater robots and other fields.

Active vibration control of fluid-conveying pipelines: Theoretical and experimental studies

For the fluid-conveying pipeline with macro-fiber composites (MFC), relevant dynamic modeling and experimental testing studies are rarely found in previous papers. Therefore, this paper has carried out related research work. Firstly, considering the fluid-structure interaction and piezoelectric effects, a semi-analytical modeling method for the fluid-conveying pipeline with MFC attaching to any position is proposed. A new Runge-Kutta-Gear (RKG) time-domain solution method is presented for solving state-space equations with the characteristics of rigid equations, and the design methods of Linear-Quadratic Regulator (LQR) controller and Proportional-Integral-Derivative (PID) controller are introduced, respectively. Secondly, an experimental system for active control and vibration test is built, and the dynamic model and control method are verified by experiments and simulations. Finally, the influence of relevant control parameters in the controller on the active control effect is discussed, and the influence law of fluid parameters such as fluid velocity and fluid pressure on the active control is also clarified. The novelty of this work is that the active vibration control and solution methods for the fluid-conveying pipeline with MFC are proposed, and the feasibility of MFC for pipeline vibration suppression is verified by experiments, which provides a new technical idea for the vibration reduction design of the fluid-conveying pipeline.

Investigations on the dynamic snap-through of MFC bonded self-resetting bistable laminates

Unsymmetric composite laminates having two stable equilibrium configurations have been studied extensively in the recent past due to their potential applications in morphing structures. Surface bonded Macro Fiber Composites (MFC) actuators have been considered as a viable solution to trigger the snap-through transition in bistable laminates. Although MFC bonded bistable laminates are widely used in morphing applications, they might require considerably high voltage inputs to achieve the required levels of actuation control during the shape transition. As a solution, other possible energy sources can be combined with active MFC patches to reduce the snap-through energy required from the single source of MFC actuation. In this work, we examine the dynamic behavior of bistable composite plates actuated using MFC actuators, where external vibration energy has been used to assist with the MFC-controlled actuation between stable states. A refined semi-analytical model based on the Rayleigh–Ritz formulation has been proposed, where the membrane energy and the bending energy are separately evaluated. Bending components are directly evaluated using the approximated transverse displacement functions, whereas the membrane components are evaluated separately by combining compatibility conditions and equilibrium equations. Results from the proposed semi-analytical framework are compared with a full geometrically nonlinear finite element framework and necessary experimental observations. The results show a significant reduction in the snap-through energy demand on MFC layers where external dynamic excitation assists the snap-through process. Additionally, a parametric study is performed using variable stiffness (VS) fiber orientation parameters, achieving bistable laminate-MFC configurations that lower snap-through requirements through the proposed morphing strategy. Thus, the study offers to aid a multi-efficient snap-through strategy for the morphing of multistable composite structures.

Modeling and vibration control of a rotating flexible plate actuated by MFC

The macro fiber composite (MFC) is a novel piezoelectric intelligent material, which is widely used in the field of vibration control due to its flexibility and larger actuation forces than PZT. In this paper, a laminated plate model considering the anisotropy of MFC is developed and applied to the vibration control of a rotating plate. The laminated plate is defined as a layerwise model, which deformation is described by the Absolute Nodal Coordinate Formulation (ANCF). The MFC laminated plate element contains 48 degrees of freedom (DOFs) where the effect of MFC element can be internally incorporated without increasing the DOFs of system. Simultaneously, a neural network PD control is adopted to control the vibration of the rotating plate. Eventually, static, dynamic, and modal analyses are performed to investigate the effects of different parameters. Several vibration simulations are carried out to illustrate the ability of MFC patches on vibration control. The findings in this article would be applied to mechanical prediction and control for rotor blades of helicopters, solar panels, etc.

Investigation into Vibration Excitation and Mode Selection of Thin Rectangular Plates with Multiple Bolts and Stand-Off Supports

The flexural vibrations of a thin rectangular plate with multiple rigid-point supports were examined theoretically, numerically, and experimentally. The analytical resonant frequencies and mode shapes obtained via the superposition method were compared with the finite element method (FEM) solutions. Experimental measurements were obtained using an amplitude-fluctuation electronic speckle pattern interferometer (AF-ESPI). The investigations considered two boundary conditions: (1) a completely free rectangular plate with one bolt and stand-off support at the center and (2) a rectangular plate with five bolts and stand-off supports along the short edge. In both cases, the plate was actuated using four macro-fiber composites (MFCs). The vibration characteristics of the plate varied significantly with the number and position of the rigid-point supports and the configuration of the MFC driving voltage. An analytical solution is proposed for frequency selection and mode control through the strategic placement of the rigid-point supports. The proposed solution provides a simple and efficient approach for controlling the vibration mode of the plate in various applications, such as vibration suppression, energy harvesting, and structural health monitoring.

An improved active damping of fan blade using piezoelectric MFC actuators and PSO optimization

This study introduces piezoelectric actuators for blade vibration control and aims to establish both experimental and numerical benchmarks for active vibration control with macro fiber composite (MFC) piezoelectric actuators on engine blades. It also involves optimizing the placement of MFC actuators. Experimental and numerical assessments were conducted on a 3D-printed fan model with integrated piezoelectric MFC actuators. The results confirm the effectiveness of the proposed approach, aided by a PID controller, in significantly reducing and damping blade vibrations. This comprehensive study offers a promising solution to enhance aviation engine performance and longevity.

Comparative Performance Analysis of Inverse Phase Active Vibration Cancellation Using Macro Fiber Composite (MFC) and Vibration Absorption of Silicone Gel for Vibration Reduction.

This study focuses on addressing the issue of unwanted vibrations commonly encountered in various fields by designing an Active Vibration Cancellation (AVC) structure using a flexible piezoelectric composite material macro fiber composite (MFC). A comparative performance analysis was conducted between the AVC and a traditional passive gel that continuously absorbs vibrations. The results showed that AVC was more effective in mitigating vibrations, making it a promising solution for vibration control. The results of this study from extensive vibration-sensing experiments and comparisons revealed that AVC effectively cancels the vibrations and vibration absorption performance of the passive gel. These findings underline the potential of AVC as an efficient method for eliminating and managing undesired vibrations in practical applications. Specifically, AVC demonstrated a high vibration cancellation ratio of approximately 0.96 at frequencies above 10 Hz. In contrast, passive gel exhibited a relatively consistent vibration absorption ratio, approximately 0.70 to 0.75 at all tested frequencies. These quantitative findings emphasize the superior performance of AVC in reducing vibrations to levels below a certain threshold, demonstrating its efficacy for vibration control in real-world scenarios.

Screening significant properties of macro-fiber composite laminate substrate anisotropy with viscoelastic and thermal considerations at the quasi-static level

A macro-fiber composite (MFC) is a class of smart material actuator that employs piezoceramic fibers to extend or contract under an applied electric field. When embedded on a thin substrate, actuated MFCs induce surface pressure, resulting in out-of-plane motion. Design characteristics of the substrate, such as anisotropy, give rise to unique bend/twist behavior. Previous studies on MFC applications have focused on optimizing patch location in relation to the local design to achieve optimal bend/twist motion. However, the resolution to these approaches is restricted to the design space of the application, presenting an absence in piezoelectric laminate design intuition. This research aims to streamline the initial optimization process by analyzing the significant material properties associated with substrate design. To accomplish this, a viscoelastic piezoelectric plate theory model is developed to accurately capture the displacement behavior of the MFC laminate for any given substrate design. Experimental data is used to validate and refine the model, ensuring it closely represents real-world physics. A 2k fractional factorial design of experiments approach is used to identify significant substrate properties per MFC laminate configuration, assigning each material property a two-level coding system. Three configurations are observed, with each exhibiting distinct significant properties and effects compared to others. Furthermore, the study explores the impact of thermal factors on substrate behavior for these MFC laminates, highlighting how significant properties can be temperature dependent. The contributions to the kinematic response due to substrate property perturbation varies uniquely per material property and MFC laminate configuration. Statistical evidence supports the notion that the hysteretic behavior of a material is unaffected by thermal influences and is solely determined by the elastic constants of the substrate. The maximum remanent hysteretic response is shown to be proportional to the maximum actuation response at near room temperature.

Numerical and experimental studies of a morphing airfoil with trailing edge high-frequency flapping

The aerodynamic performance of a morphing airfoil is numerically and experimentally investigated. The morphing airfoil is designed based on macro fiber composites, capable of trailing edge flapping during 10–90 Hz with a maximum amplitude of 0.55 mm. A numerical model with flexible deformation walls based on the experiment is established to precisely restore the actual dynamic morphing instead of segmental deformation to explore the transient aerodynamic performance of high-frequency flapping. The drag coefficient is reduced by 2.07% at the flapping frequency (ff) of 37.5 Hz compared with the rigid airfoil, while the drag coefficient and the lift coefficient increase by 4.8% and 5.8% for ff at 600 Hz. The vortex is broken up by flapping, and the corresponding position has been forwarded to the tail. Dynamic mode decomposition shows that the wing's flapping dominates the second mode and the high-frequency vortex has changed to low-frequency. The energy of higher modes is transferred to lower-order modes that the first mode's power has risen sharply from 49.29% of the rigid airfoil to 91.83%. In the wind tunnel experiment, the lift and drag forces are increased by 1.88% and 0.77% at the flapping frequency of 40 Hz, respectively. Furthermore, the lift force frequency is locked by flapping and changes from 124.9 Hz of the rigid airfoil to the flapping frequency, consistent with the computational fluid dynamics results. The research has provided a solution to reduce the drag force and increase the lift force of the aircraft by the trailing edge flapping.

Dynamic response of piezoelectrically actuated bistable cross-ply laminates under oscillating impulse voltages

Multistable composite laminates are ideal candidates for morphing applications due to their ability to switch between multiple stable states with proper actuation mechanisms. Surface-bonded macro fiber composite (MFC) actuators to trigger snap-through between one stable shape to another by applying external voltages have attracted considerable attention recently. In this work, dynamic snap-through of bistable unsymmetric cross-ply laminate using MFC actuators under oscillating impulse voltages has been investigated. Both unimorph and bimorph laminate-MFC configurations are considered for the analysis. The stable equilibrium configurations of the MFC-actuated bistable laminate, considering the effects of MFC bondage, are discussed using the proposed finite element (FE) framework. Under the action of oscillating impulse voltages, the single-well and cross-well oscillations of the active bistable plate are analyzed in detail through time responses and phase portraits. The FE results show the advantage of actuating MFC layers through the oscillating impulse voltages as it leads to a reduction in the maximum snap-through voltage requirements.

Electroactive morphing effects on the aerodynamic performance through wobulation around an A320 wing with vibrating trailing edge at high Reynolds number

This study aims to investigate the effects of electroactive morphing on a 70cm chord A320 wing by means of near trailing edge slight deformation and vibration. Wing morphing is performed by Macro Fiber Composites (MFC) piezoelectric actuators distributed along the span of the “Reduced Scale” (RS) prototype of the H2020 European research project “Smart Morphing and Sensing for aeronautical configurations” - (SMS). The configuration studied corresponds to a low-subsonic regime (Mach number 0.063) with a 10∘ incidence and a Reynolds number of 1 Million. The numerical simulations are carried out with the Navier-Stokes Multi-Block (NSMB) solver, which takes into account the deformation of the rear part of the wing implemented experimentally with the piezoelectric actuators. A detailed physical analysis of the morphing effects on the wake dynamics and on the aerodynamic performance is conducted with a constant amplitude of 0.7mm over a wide range of actuation frequencies [10-600]Hz. Optimal vibration ranges of [180-192]Hz and [205-215]Hz were found to respectively provide a 1% drag reduction and a 2% lift-to-drag ratio increase compared to the non-morphing (static) configuration. The natural frequencies associated with the shear layer Kelvin-Helmholtz (KH) vortices and the Von-Kármán (VK) vortex shedding were found to play a central role in the modification of the wake dynamics by morphing as well as in the increase of the aerodynamic performance. Actuating at (or close to) the upper shear layer (USL) natural frequency (∼185Hz) provides an order of 1% drag reduction and 1% lift-to-drag ratio increase, while actuating at (or close to) the lower shear layer (LSL) natural frequency (∼208Hz) provides an order of 8% lift increase and 2% lift-to-drag increase. Furthermore, the linear modulation in time of the actuation frequency (wobulation) demonstrated, through an appropriate mapping, the ability to quickly and efficiently detect optimal constant actuation frequency ranges providing aerodynamic performance increase and simultaneously reducing the amplitude of the main instability modes.

Adaptive active vibration control for composite laminated plate: Theory and experiments

In this paper, an analysis model of adaptive active vibration control system of composite laminated plate using macro fiber composite (MFC) piezoelectric patches is presented, and the experimental testing is carried out. Electromechanical coupling equations of the composite laminated plate are established by considering the influence of the mass and stiffness of MFC piezoelectric patches. The adaptive active vibration control scheme for composite laminated plate based on the filtered-x least mean square (FxLMS) algorithm is proposed. The accuracy of the present analysis model is validated by the results of experimental test and finite element method (FEM). It can be found that the vibration responses nearby the first and second natural frequencies of the composite laminated plate can be rapidly and greatly suppressed by the adaptive active control system and experimental test. Moreover, the dynamic responses of the composite plate under multi-frequency excitation and random excitation can be fast controlled by the presented adaptive active control system. The novelty of this work is that a theoritical analysis model of adaptive closed-loop control system based on the MFC piezoelectric patches is presented for vibration suppression of composite laminated plate, and the effectiveness of the proposed adaptive active model are validated by experimental testing.

Adaptive iterative learning control and inverse compensation of macro fiber composite system with hysteresis

Macro fiber composite (MFC) actuators, which exhibit excellent flexibility and strong deformability, are widely used in aerospace exploration, flexible robotics, and other applications. However, the rate-dependent hysteresis nonlinearity of the flexible beam driven by MFCs significantly affects positioning accuracy. This study utilizes a new Hammerstein model to describe the hysteresis of an MFC system and proposes a control strategy that combines adaptive iterative learning control and inverse compensation. The adaptive iterative learning control allows the learning gain parameters to be adjusted based on the tracking error. A high gain ensures the convergence speed of iterative learning, whereas a small learning gain provides high robustness and convergence accuracy. Trajectory tracking experiments are conducted to verify the effectiveness of the proposed control strategy. Compared with the case of direct inverse compensation, after the sixth iteration, the tracking maximum absolute error, relative error, and corresponding root mean square error of the proposed control strategy reduce by 73% on average. Moreover, compared with the case of P-type iterative learning control combined with inverse compensation, the metrics above reduce by 12% on average. The proposed control strategy offers higher tracking accuracy and greater practicality in the trajectory tracking of MFC systems.

Hydrodynamic energy collection using a cylinder with different cross sections based on macro-fiber composite

With the rapid development of small and microelectronic devices, energy utilization from the surrounding environment has been paid significant attention. This study aims to enhance the performance of energy harvesting devices utilizing a macro-fiber composite (MFC) attached to a cantilever beam with a cylinder attached at the free end with three different cross sections, namely circular, square, and triangular. Experiments were conducted in a low-speed circulating water flume at Reynolds numbers ranging within 770–8800. Three oscillation modes based on different cross sections can be observed: (1) vortex-induced vibration (VIV) for the circular cylinder water energy harvester (CWEH); (2) combined VIV-galloping for the triangular cylinder water energy harvester (TWEH); and (3) separated weak vortex-induced vibration-galloping for the square cylinder water energy harvester. The characteristics of the MFC water energy harvester are revealed through the vibration mechanism analysis. The effects of flow velocity, resistance, and cross section on the energy harvester were studied, and the flow field was analyzed. The energy harvesting results indicate that the TWEH exhibits the highest voltage, power, power density, and efficiency among the three devices; the maximum voltage, power, power density, and efficiency achieved are 28.9 V, 241.1 μW, 512.6 μW/cm3, and 0.23%, respectively. Despite the TWEH exhibiting a maximum efficiency that is 0.68 times that of the CWEH, it is noteworthy that the TWEH presents a superior performance in terms of maximum voltage, power, and power density by factors of 2.77, 7.37, and 7.38, respectively, compared to the CWEH. Hence, the research suggests that the TWEH is the most suitable device for energy collection under low-speed water flow conditions.