Macro Fiber Composite Actuators Research Articles

Performance enhancement of a bioinspired micro air vehicle by integrating a smart composite in its morphing wing

The purpose of this paper is to show the advantages of using a smart composite in a micro air vehicle (MAV) equipped with morphing wing technology. A Macro Fiber Composite (MFC) actuator is attached to the wing’s bottom surface to modify the wing camber during the mission. This material allows the MAV to be optimized according to each flight, thus making it more versatile and attractive to the market. The elongation of the lower surface when a positive voltage is applied to the actuator is translated to an increment in camber, which results in an increment in the maximum lift coefficient, thus enabling the vehicle to fly slower to adapt to any payload. Besides, a reduction in camber results in an increase in aerodynamic efficiency, which improves range and endurance. Several tests of the MAV at prototype level have been carried out at INTA, so as to demonstrate the feasibility of implementing MFC actuators to control and manoeuvre these vehicles. The use of this material in aerospace industry opens up various fields of research in aerospace engineering, such as new features in flight mechanics and aerodynamic performance and new strategies in the design of flight stability and control laws.

Aero-structural optimization and actuation analysis of a morphing wing section with embedded selectively stiff bistable elements

Morphing wings provide a potential avenue to improve aerodynamic performance of aircraft operating at multiple design conditions. Nevertheless, morphing wing design is constrained by the mutually exclusive goals of high load-carrying capacity, low weight, and sufficient aerodynamic control authority via conformal shape adaptation. This trade-off can be addressed by exploiting the stiffness selectivity and shape “lock-in” properties enabled by using bistable beam-like elements within compliant structures. In this paper, we present an aero-structural optimization method to realize morphing structures with selective stiffness and shape “lock-in” capability from embedded bistable elements. We leverage an embeddable beam element with an invertible curved arch that provides stiffness selectivity and camber variation to the proposed rib geometry. Optimization objectives and constraints are designed to maximize the structure’s stiffness change and camber morphing “lock-in” effect when operating at two distinct flight conditions. Using the optimization results, we manufacture a wing section demonstrator with selective stiffness and “lock-in” morphing featuring two optimized ribs, a load-carrying skin made of a carbon reinforced laminate, Macro-Fiber Composite (MFC) actuators, and a servo-controlled mechanism for switching the bistable elements’ states. The power and energy requirements of actuating and holding a target deflection are experimentally measured and compared. The results show that the bistable elements can assist in holding a target deflection at a reduced energy cost. Finally, we test the experimental demonstrator in a low-speed wind tunnel demonstrating the load carrying capability and lift variation achieved from switching states.

Research on Asymmetric Hysteresis Modeling and Feedforward Compensation of Macro Fiber Composite Actuator

Research on Asymmetric Hysteresis Modeling and Feedforward Compensation of Macro Fiber Composite Actuator

Asymmetric Bouc-Wen hysteresis modeling for MFC actuator via hybrid APSO-TRR identification algorithm

Macro fiber composite (MFC) is widely used in active vibration and deformation control. The intrinsic asymmetric hysteresis nonlinearity of MFC affects the control accuracy. In this paper, a modified Bouc-Wen (MBW) model based on the sigmoid function is proposed to describe the asymmetric hysteresis characteristics of MFC, and its parameters are identified by a hybrid algorithm composed of the trust-region reflection method and asynchronous particle swarm optimization. The accuracy of the proposed MBW model is verified though hysteresis tests of MFC under different drive frequencies. The results show that the MBW model can accurately model the asymmetrical hysteresis of the MFC actuator, the modeling error is reduced by 72% compared with the classic Bouc-Wen model. The proposed hybrid parameter identification method saves 95% of the time compared with the particle swarm optimization and asynchronous particle swarm optimization algorithms. • A modified Bouc-Wen (MBW) model is proposed to describe the asymmetric hysteresis characteristics of MFC actuators. • A hybrid algorithm (APSO - TRR) with global and local search ability is proposed for parameter identification. • Performance of proposed APSO - TRR is compared with classical PSO、APSO and TRR algorithms. • Accuracy of proposed asymmetric Bou–Wen model is compared with classical Bou–Wen model.

Dynamic Response of a Composite Fan Blade Excited Instantaneously by Multiple MFC Actuators

The vibration characteristics of a composite fan blade are much more complex than those of a solid titanium fan blade due to the anisotropic material properties and complex excitations coming from unsteady flow and mechanically induced vibration. In this study, the dynamic response measurement of a wide-chord composite fan blade was carried out to study the vibration characteristics using multiple macro fiber composite (MFC) actuators, which can generate complex excitation forces with different frequencies and peak values at different locations. The measured mode shapes and natural frequencies were compared with the finite element simulation results. Based on these results, the responses of the blade under the instantaneous excitation of three MFC actuators with different combinations of several natural frequencies were measured and compared. The results show that the responses of the blade excited by different combinations of MFC actuators with different frequencies were significantly different from those excited by a single MFC actuator. The superposition of different mode shapes may cause the change of the vibration stress state, which indicates that the high cycle fatigue location of the blade under complex excitations may change to an unexpected location. The results will be helpful in understanding the vibration characteristics of the composite blades under complex excitations, and the MFC actuator could be a potential tool in vibration active control.

Multi-Mode Shape Control of Active Compliant Aerospace Structures Using Anisotropic Piezocomposite Materials in Antisymmetric Bimorph Configuration

The mission performance of future advanced aerospace structures can be synthetically improved via active shape control utilizing piezoelectric materials. Multiple work modes are required. Bending/twisting mode control receives special attention for many classic aerospace structures, such as active reflector systems, active blades, and compliant morphing wings. Piezoelectric fiber composite (Piezocomposite) material features in-plane anisotropic actuation, which is very suitable for multiple work modes. In this study, two identical macro-fiber composite (MFC) actuators of the F1 type were bonded to the base plate structure in an “antisymmetric angle-ply bimorph configuration” in order to achieve independent bending/twisting shape control. In terms of the finite element model and homogenization strategy, the locations of bimorph MFCs were determined by considering the effect of trade-off control capabilities on the bending and twisting shapes. The modal characteristics were investigated via both experimental and theoretical approaches. The experimental tests implied that the shape control accuracy was heavily reduced due to various uncertainties and nonlinearities, including hysteresis and the creep effect of the actuators, model errors, and external disturbances. A multi-mode feedback control law was designed and the experimental tests indicated that synthetic (independent and coupled) bending/twisting deformations were achieved with improved shape accuracy. This study provides a feasible multi-mode shape control approach with high surface accuracy, especially by employing piezocomposite materials.

Mode-I fracture control of unidirectional laminated composites using MFC actuators

This article presents an experimental and numerical investigation of Mode-I fracture control in aerospace grade unidirectional laminated composites (AS4/914) using the smart material approach. The P1 type macro fiber composites (MFC) actuators are selected for current research because of their higher free strain, high mechanical flexibility, and good blocking force. The opening mode (Mode-I) interlaminar fracture tests have been carried out on DCB specimens having surface bonded MFC actuator patches under the application of electric voltage within a range of 0–1500 V. These fracture control tests have been performed on pre-cracked (PC) and non pre-cracked (NPC) double cantilever beam specimens. The modified pin force model has been adopted for the evaluation of actuation forces in surface bonded MFC actuators. The XIGA-CZM based numerical formulation is utilized for numerical fracture modeling under electromechanical loading conditions. The MFC actuators have significant control over Mode-I fracture energy under the application of peak operating voltage. The numerical model using a modified pin force model in combination with XIGA-CZM based fracture model shows a good agreement with experimental observations.

Intrawell and interwell oscillations for bi-stable cross-ply laminates actuated by MFC under oscillating impulse voltages

The snap-through is a typical geometric nonlinear problem for the bi-stable laminate structures. Using the Macro Fiber Composite (MFC) actuators to actuate the snap-through behavior of the morphing structures has attracted considerable attention. In this paper, the intrawell oscillations and interwell oscillations are studied for the asymmetric four layers cross-ply bi-stable rectangular laminate actuated by the d33 type MFC actuator. It is assumed that the four edges of the bi-stable laminate are free while the geometry center of it is fixed. On the basis of the classical laminated plate theory and the Hamilton’s principle, the equations of motion of the bi-stable laminate which are expressed by curvatures are presented. The stable equilibrium configurations of the bi-stable laminate considering the effects of MFC are given. Under the action of oscillating impulse voltages, the intrawell oscillations and interwell oscillations of the system are analyzed in detail through the frequency-response curves, time response and the phase portraits. The numerical results show that the snap-through behavior is easier to realize for the bi-stable laminate actuated by the oscillating impulse voltages than that actuated by the static voltages. Furthermore, snap-through behavior can be better controlled by changing the amplitude and frequency of the applied voltages in a certain range.

The smart morphing winglet driven by the piezoelectric Macro Fiber Composite actuator

AbstractA smart morphing winglet driven by piezoelectric Macro Fiber Composite (MFC) is designed to adjust cant angle autonomously for various flight conditions. The smart morphing winglet is composed of the MFC actuator, DC-DC converter, power supply, winglet part and wing part. A hinge is designed to transfer the bending deformation of intelligent MFC bending actuator to rotation of the winglet structure so as to achieve the adaptive cant angle. Experimental and numerical work are conducted to evaluate the performance of smart morphing winglet. It is demonstrated that the proposed intelligent MFC bending actuator has an excellent bending performance and load resistance. This smart morphing winglet exhibits the excellent characteristic of flexibility on large deformation and lightweight. Moreover, a series of wind tunnel tests are performed, which demonstrate that the winglet driven by intelligent MFC bending actuator produces sufficient deformation in various wind speed. At high wind speed, the cant angle of the winglet can reach 16 degrees, which is still considered to be very useful for improving the aerodynamic performance of the aircraft. The aerodynamic characteristics are investigated by wind tunnel tests with various attack angles. As a result, when the morphing winglet is actuated, the lift-to-drag ratio could vary up to 11.9% and 6.4%, respectively, under wind speeds of 5.4 and 8.5m/s. Meanwhile, different flight phases such as take-off, cruise and landing are considered to improve aerodynamic performance by adjusting the cant angle of winglet. The smart morphing winglet varies the aerofoil autonomously by controlling the low winglet device input voltage to remain optimal aerodynamic performance during the flight process. It demonstrates the feasibility of piezoelectric composites driving intelligent aircraft.

An Alternative Electro-Mechanical Finite Formulation for Functionally Graded Graphene-Reinforced Composite Beams with Macro-Fiber Composite Actuator.

With its extraordinary physical properties, graphene is regarded as one of the most attractive reinforcements to enhance the mechanical characteristics of composite materials. However, the existing models in the literature might meet severe challenges in the interlaminar-stress prediction of thick, functionally graded, graphene-reinforced-composite (FG-GRC)-laminated beams that have been integrated with piezoelectric macro-fiber-composite (MFC) actuators under electro-mechanical loadings. If the transverse shear deformations cannot be accurately described, then the mechanical performance of the FG-GRC-laminated beams with MFC actuators will be significantly impacted by the electro-mechanical coupling effect and the sudden change of the material characteristics at the interfaces. Therefore, a new electro-mechanical coupled-beam model with only four independent displacement variables is proposed in this paper. Employing the Hu–Washizu (HW) variational principle, the precision of the transverse shear stresses in regard to the electro-mechanical coupling effect can be improved. Moreover, the second-order derivatives of the in-plane displacement parameters have been removed from the transverse-shear-stress components, which can greatly simplify the finite-element implementation. Thus, based on the proposed electro-mechanical coupled model, a simple C0-type finite-element formulation is developed for the interlaminar shear-stress analysis of thick FG-GRC-laminated beams with MFC actuators. The 3D elasticity solutions and the results obtained from other models are used to assess the performance of the proposed finite-element formulation. Additionally, comprehensive parametric studies are performed on the influences of the graphene volume fraction, distribution pattern, electro-mechanical loading, boundary conditions, lamination scheme and geometrical parameters of the beams on the deformations and stresses of the FG-GRC-laminated beams with MFC actuators.

Motion planning of a fish-like piezoelectric actuated robot using model-based predictive control

This work proposes a novel methodology for planning the motion of fish-like soft robots actuated by macro-fiber composite (MFC) pairs. These structures should mimic oscillatory and undulation movements, which can be accomplished if the amplitude of the tail motion is larger than that of the head motion. Design strategies, such as the use of concentrated and distributed masses, are addressed to mimic fish-like motion since they guarantee suitable mode shapes for the structure. The motion planning proposal explores a model-based predictive control (MPC) strategy for deriving the input signals for the MFC actuators. This model-based control strategy requires the use of reasonably small-sized models. This is accomplished by extracting modal state-space models based on the free–free Euler–Bernoulli beam theory considering the electro-mechanical coupling of the MFC actuator pairs. Numerical results demonstrate the capability of the proposal for deriving bounded input signals that generate oscillatory and undulation movements even in the presence of disturbances. This general approach can be further extended for other applications.

Numerical analysis of Lamb waves propagating through impact damage in a skin-stringer structure composed of interlaminar-toughened CFRP

Many structural health monitoring systems are being developed to detect the impact damages in carbon fiber reinforced plastic (CFRP) structures, which are widely adopted in the aviation industry. In this study, a refined finite element model is established to simulate a Lamb wave propagating through impact damage in a CFRP skin-stringer structure. The accurate stiffness constants are determined for toughened CFRP laminates, which include the resin layers. The impact damage of toughened CFRP laminates is modeled as a truncated-cone-shaped region in which the rigidity is homogeneously reduced. Furthermore, the directive generation of the Lamb wave through a macro fiber composite (MFC) actuator is incorporated in the model. Simulations are performed for several configurations of the MFC and impact damage. The observed tendency of the delay in the arrival time of the lowest antisymmetric Lamb wave mode is noted to be consistent with the experimental results. The proposed model can facilitate the determination of the optimized configuration of MFCs in CFRP structures.

Semi-analytical investigations on bistable cross-ply laminates with MFC actuators

Most existing semi-analytical models to analyse multistable structures are based on the principle of minimum potential energy, which inherently does not satisfy the in-plane equilibrium equations in a strong sense. Although such models predict the multistable shapes with reasonable accuracy, there is a significant discrepancy in predicting the snap-through behaviour when compared to the finite element (FE) or experimental results. In this work, a refined analytical model is derived to analyse a bistable cross-ply elliptical disc using Föppl von Kármán kinematics. The Rayleigh–Ritz approach with a decoupled energy formulation is used, where the stretching and bending energies are separated using the semi-inverse constitutive equation. The in-plane stress resultants are expressed in terms of curvatures using the compatibility and the in-plane equilibrium equations. A closed-form solution for the curvatures is derived to predict the cured bistable shapes of elliptical laminates. A layer of macro fibre composite actuator is added to trigger the snap-through between the stable shapes. Consequently, the critical voltage at which the snap-through occurs is predicted using the analytical model. The model is further extended to square plates, where the solutions of the differential equations emanating from the compatibility and in-plane equilibrium equations are obtained by converting the resulting differential equations into the form of standard FE elasticity problem. The in-plane stress resultants for the square plates are calculated by numerically solving the resulting elasticity problem using a standard FE discretization approach. The solutions are further compared with previous experimental studies and the results from a fully geometrically non-linear FE model.

Low-Computational-Cost Technique for Modeling Macro Fiber Composite Piezoelectric Actuators Using Finite Element Method.

The large number of interdigitated electrodes (IDEs) in a macro fiber composite (MFC) piezoelectric actuator dictates using a very fine finite element (FE) mesh that requires extremely large computational costs, especially with a large number of actuators. The situation becomes infeasible if repeated finite element simulations are required, as in control tasks. In this paper, an efficient technique is proposed for modeling MFC using a finite element method. The proposed technique replaces the MFC actuator with an equivalent simple monolithic piezoceramic actuator using two electrodes only, which dramatically reduces the computational costs. The proposed technique was proven theoretically since it generates the same electric field, strain, and displacement as the physical MFC. Then, it was validated with the detailed FE model using the actual number of IDEs, as well as with experimental tests using triaxial rosette strain gauges. The computational costs for the simplified model compared with the detailed model were dramatically reduced by about 74% for memory usage, 99% for result file size, and 98.6% for computational time. Furthermore, the experimental results successfully verified the proposed technique with good consistency. To show the effectiveness of the proposed technique, it was used to simulate a morphing wing covered almost entirely by MFCs with low computational cost.

Hysteresis modeling and feedforward compensation of a flexible structure actuated by macro fiber composites using bias bipolar Prandtl-Ishlinskii model

As a novel fiber-based piezoelectric composite material, macro fiber composites (MFC) affords notable advantages of good flexibility, high deformability, and large actuation ability. However, the intrinsic hysteresis behavior of the MFC decreases the positioning precision and performance of the flexible structure actuated by MFC actuators. A bias bipolar Prandtl-Ishlinskii (BBPI) model is presented to describe the bias bipolar hysteresis nonlinearity of a MFC-actuated flexible cantilever. The BBPI hysteresis model is composed of two parts: a superposition of the weighted play operators of the classical Prandtl-Ishlinskii (PI) model is employed to characterize the symmetric hysteresis. And a superposition of the weighted dead-zone operators is cascaded to deal with the bias bipolar behavior. Experimental identification results demonstrate that the presented BBPI model exhibits better modeling performance than the classical PI model. A feedforward compensation strategy based on the inverse BBPI hysteresis model is proposed. Experiments on trajectories tracking subject to a triangular wave, sinusoidal wave, and triangular wave with random amplitudes are carried out. Experimental results demonstrate the feasibility and effectiveness of the proposed BBPI model and the inverse feedforward compensator.

Cantilever-based micro thrust measurement and pressure field distribution of biomimetic robot fish actuated by macro fiber composites (MFCs) actuators

Underwater autonomous vehicles (UAVs) actuated by smart actuators have attracted increasing attention. A miniature macro fiber composite (MFC)-actuated robot fish inspired by koi fish is developed. A cantilever mechanism is designed to transfer the dynamic micro thrust of the robot fish. Three design indexes, namely the bending stiffness, the ratio of the bending stiffness to the torsional stiffness, and the natural frequency of the cantilever transducer are proposed. Thus, a simple and effective method to determine the structural parameters of the cantilever-based micro thrust force measurement system is presented. Calibration results demonstrated that the parameters of the proposed cantilever transducer match well with the designed indexes. Dynamic variation mechanisms of the micro thrust force associated with the swimming behaviors of the robot fish are well captured using the proposed measurement system. Experimental results show that the MFC-actuated robot fish obtains the biggest mean thrust of 1.73 mN in the case of the largest oscillating velocity. The maximum instant thrust grows with the increment of the oscillating frequency, and achieves its maximum of 7.35 mN in the case of 10 Hz. While the maximum instant drag first decreases then increases as the actuation frequency increases, and obtains its minimum of −2.62 mN in the case of the maximum oscillating velocity. On the contrary, variations of the thrust pattern/oscillating period are reversed to those of the maximum instant drag. Computational fluid dynamics results demonstrate that variations of the instant thrust are fully determined by the distribution and intensity of the concentrated pressure regions induced by the oscillating caudal fin. The cycle-averaged velocity fields are closely related to the mean thrust generated by the MFC-actuated robot fish. As a result, the fluid–structure interaction mechanisms associated with the thrust variations of the MFC-actuated robot fish are revealed. This study may be useful for the design and realization of UAVs actuated by smart actuators.

Large deflection electro-mechanical analysis of composite structures bonded with macro-fiber composite actuators considering thermal loads

In this paper, static analysis of laminated composite plates and shells bonded with macro-fiber composite (MFC) actuators under thermo-electro-mechanical loads is considered. Most earlier studies in the literature focused on the effects of MFC actuation power and fiber orientations on shape deformation of composite plates/shells subjected to electrical voltage only. Also most of the earlier studies on MFC- $$\hbox {d}_{33}$$ bonded smart structures in literature are performed by commercial softwares like Ansys or Abaqus using the thermal strain equivalent approach to model the piezomechanical coupling. Here, our earlier developed geometrically nonlinear plate and shell finite elements considering finite rotation theory are extended for MFC actuator-bonded composite structures taking into account additionally the response to temperature gradients. An improved Reissner–Mindlin hypothesis is considered to derive the variational formulation, in which a parabolic assumption of transverse shear strains across the thickness is assumed. MFC actuators dominated by the $$\hbox {d}_{33}$$ effect (MFC- $$\hbox {d}_{33}$$ ) with arbitrary fiber orientations are considered. The numerical model is validated with composite beams and plates by comparing the results of simulations with experimental investigations existing in the literature. An angle-ply composite shell structure is studied in detail concerning geometrically nonlinear analysis of bending and twisting deformations under different MFC- $$\hbox {d}_{33}$$ fiber orientations under electric loading. Shape control of thermally induced deformations of composite plates and shells is performed using bonded MFC- $$\hbox {d}_{33}$$ actuators and the significance of the present geometrically nonlinear model is highlighted.

Condition assessment of timber utility poles using ultrasonic guided waves

In this study, guided stress waves were used to evaluate the conditions of a timber utility pole experimentally and numerically using COMSOL Multiphysics. Macro Fiber Composites (MFCs), due to their flexibility and convenience to install on curved surfaces, were used to actuate and sense guided waves along the tested specimens. Based on the wave propagation characteristics in these types of structures, an MFC actuator ring, which was developed in the previous work, was applied to tune and enhance the propagating wave modes. The designed ring was used to excite longitudinal ultrasonic wave modes, mainly L(0,1), to determine the embedded length of the pole and damage localization, in both traction free and embedded conditions.Embedding the timber in the soil had minimum impact on the wave propagation characteristics, given that the waves were confined in the timber pole with minimal leakage to the surrounding. The embedded length was determined accurately for the sound and the damaged timber specimen, using both experimental and numerical data with an error of less than 3%. The deterioration in the timber structure, within the embedded region, was also evaluated with high accuracy of 93%. Based on the obtained results, guided waves have a high potential to be used as a non-destructive tool for the assessment and evaluation of timber utility poles.

Electricity-structure-fluid coupled modelling and experiment of underwater flexible structure with partially distributed macro fiber composites

Dynamic oscillating behavior of the flexible structure immerged in viscous fluids has attracted growing attention and been widely used in various practical applications. A general electricity-structure-fluid coupled model for the forced dynamic responses of a cantilever immersed in fluids, with partially distributed macro fiber composite, is proposed in this paper. Based on the classical Euler–Bernoulli beam theory, the first mass-normalized mode shape of the cantilever with partially bonded macro fiber composite is determined using assumed mode method. The attachment of the macro fiber composite actuators stiffens the macro fiber composite-bonded portion of the cantilever. The established mode shape matches perfectly with experimental results. Considering the macro fiber composite actuator as a set of representative elements connected in parallel, the internally actuation moment provided by the macro fiber composite actuators is obtained. The hydrodynamic load caused by the surrounding fluids, decomposed into the added mass and hydrodynamic damping parts, is also added to the theoretical model in the frequency-domain form. The predicted in-air and underwater dynamic behaviors of the flexible beam are consistent with the experimental results at different auction levels. Thus, the obtained general electricity-structure-fluid coupled model can be used to predict the forced dynamic responses of flexible structure with partially bonded actuators immersed in fluids.

A multifunctional high strain composite (HSC) hinge for deployable in-space optomechanics

Deployable, large aperture space optics require precision phasing of segmented and uniquesparsely-filled primaries for optical alignment which introduce challenges to these already complex optomechanical designs. This work presents a multifunctional high strain composite hinge with integrated piezoelectric actuation capabilities to support deployable space telescopes and address these challenges. Finite element simulations and experimental testing are utilized to design and validate the multifunctional high strain composite hinge. Macro Fiber Composite actuators are integrated with the high strain composite hinge in a specific layout based on the finite element analyses to induce piston, pitch, and roll tip motions for precision optical alignment after deployment. A feedback control system is implemented to demonstrate an actuation resolution of better than 25 nm over a 15 µm range for a single degree of freedom, validating the multifunctional high strain composite hinge for alignment to levels required for visible wavelength optical systems.