Composite Actuators Research Articles

Improved active vibration control of a cantilever beam using MFC actuators with Hammerstein model-based hysteresis modeling and VSS-FxLMS control algorithm

This study aims to enhance active vibration control in a cantilever beam using macro fiber composite (MFC) actuators. To address the challenge of accurately modeling the complex hysteresis behavior of MFC actuators, an advanced hysteresis modeling technique is employed, integrating a non-symmetric Bouc–Wen model with an Auto-Regressive model with eXogenous inputs (ARX). The parameter estimation of this model is optimized using an adaptive mutation factor, and multiple mutation strategy differential evolution (AmFMMDE) algorithm. Additionally, a Variable Step Size Filtered-x Least Mean Square (VSS-FxLMS) algorithm with step size adaptation based on normalized error change is utilized for effective vibration control. This approach shows promising potential for practical engineering applications requiring precise and efficient active vibration control.

A Pneumatic Soft Exoskeleton System Based on Segmented Composite Proprioceptive Bending Actuators for Hand Rehabilitation.

Soft pneumatic actuators/robotics have received significant interest in the medical and health fields, due to their intrinsic elasticity and simple control strategies for enabling desired interactions. However, current soft hand pneumatic exoskeletons often exhibit uniform deformation, mismatch the profile of the interacting objects, and seldom quantify the assistive effects during activities of daily life (ADL), such as extension angle and predicted joint stiffness. The lack of quantification poses challenges to the effective and sustainable advancement of rehabilitation technology. This paper introduces the design, modeling, and testing of pneumatic bioinspired segmented composite proprioceptive bending actuators (SCPBAs) for hand rehabilitation in ADL tasks. Inspired by human finger anatomy, the actuator's soft-joint-rigid-bone segmented structure provides a superior fit compared to continuous structures in traditional fiber-reinforced actuators (FRAs). A quasi-static model is established to predict the bending angles based on geometric parameters. Quantitative evaluations of predicted joint stiffness and extension angle utilizing proprioceptive bending are performed. Additionally, a soft under-actuated hand exoskeleton equipped with SCPBAs demonstrates their potential in ADL rehabilitation scenarios.

Reinforced Nacre-Like MXene/Sodium Alginate Composite Films for Bioinspired Actuators Driven by Moisture and Sunlight.

MXene-based soft actuators have attracted increasing attention and shown competitive performance in various intelligent devices such as supercapacitors, bionic robots and artificial muscles. However, the development of robust MXene-based actuators with multi-stimuli responsiveness remains challenging. In this study, a nacre-like structure soft actuator based on MXene and sodium alginate (SA) composite films is prepared using a straightforward solvent casting self-assembly method, which not only enhances the mechanical performance (tensile strength of 72MPa) but also diversifies the stimuli responsiveness of the material. The composite actuators can be powered by external stimuli from renewable energy sources, from moisture inducing a maximum bending angle of 190 degrees at a relative humidity (RH) of 91%, and sunlight irradiation generating a maximum curvature of 1.45 cm-1 under 100mW cm-2. The feasibility of practical applications, including moisture-responsive flowers and walkers, sunlight-responsive oscillators, and smart switches, is demonstrated through comprehensive experimental characterization and performance evaluation. The work presented here provides insight into the design of robust actuators via the utilization and conversion of environmentally renewable energy sources.

Sulphonated-graphene oxide nanocomposite membranes with PVA-ZnO nanostructures and mechanized agitation-enhanced pt coating for soft robotics bending actuator

Ionic Polymer-Metal Composite (IPMC) actuators have garnered significant scientific attention in robotics and artificial muscles for their ability to operate at low voltage, high strain capacity, and lightweight construction. The lack of uniform bending in IPMC actuators undermines their control precision and restricts their range of potential applications. This study utilized the unique properties of nanoscale materials and Polyvinyl alcohol (PVA) to develop a membrane for soft robotic bending actuation. Subsequently, a platinum coating was applied to the membrane to mitigate the limitations of IPMCs in soft robotics applications. Herein, mechanized agitation was employed during the solution-casting process to enhance platinum metal (Pt-metal) coating on zinc oxide (ZnO) nanostructures within a PVA- sulphonated graphene oxide nanocomposite, achieving enhanced soft robotics bending actuation capabilities. The resultant membrane composed of sulphonated-graphene oxide and polyvinyl-zinc oxide coated with pt (PsGZ-Pt) was examined by exploring advanced analytical techniques such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction spectroscopy (XRD). Furthermore, the ionic exchange capacity (IEC), proton conductivity (PC), water uptake and water loss characteristics were evaluated to be 2.1 meq. g−1, 1.95 × 10−3 Scm−1, 59.62% at 45 °C and water loss at 9 min immersion found 38%, respectively. Electromechanical studies of the PsGZ-Pt membrane (size 30 mm length, 10 mm width, 0.07 mm thickness) showed an actuation force of 0.3253 mN and a displacement of roughly 22.8 mm at ± 3 VDC. These findings highlighted the PsGZ-Pt membrane’s potential as a low-cost alternative to expensive commercial IPMC actuators based on polymers. These results presented a straightforward, low-cost approach for synthesizing PsGZ-Pt utilizing conventional technologies. The PsGZ-Pt membrane shows promise for generating low-cost, high-performance actuation materials with a wide range of industrial applications.

Bioinspired 4D Printed Tubular/Helicoidal Shape Changing Metacomposites for Programmable Structural Morphing

AbstractBiological structures combine passive shape‐changing with force generation through intricate composite architectures. Natural fibers, with their tubular‐like structures and responsive components, have inspired the design of pneumatic tubular soft composite actuators. However, no development of passive structural actuation is available despite the recent rise of 4D printing. In this study, a biomimicry approach is proposed with inspiration from natural fiber architecture to create a novel concept of thermally active 4D printed tubular metacomposites. These metacomposites exhibit high mechanical performance and 3D‐to‐3D shape‐changing ability triggered by changes in temperature. A rotative printer is proposed for winding a continuous carbon fibers reinforced PolyAmide 6.I composite on a PolyAmide 6.6 polymer mandrel in a similar manner to the structure of cellulose microfibrils within the polysaccharide matrix of natural fiber cell‐walls. The resulting 4D printed tubular metacomposites exhibit programmable rotation and torque in response to thermal variations thanks to the control of their mesostructure and the overall geometry. Energy density values representing a trade‐off between the rotation and the torque are comparable to shape memory alloys when normalized by stiffness. Finally, a proof of concept for an autonomous solar tracker is presented, showcasing its potential for designing autonomous assemblies for structure morphing.

Mechanical Quality Factor Evaluation of Damping Film Materials for Polymer/PZT Composite MEMS Actuator

Mechanical Quality Factor Evaluation of Damping Film Materials for Polymer/PZT Composite MEMS Actuator

Hybrid dynamical modeling of shape memory alloy actuators with phase kinetic equations

Shape memory alloy morphing actuators are a type of composite soft actuator with many attractive properties such as large deformation, small form factor, self-sensing ability, and physical reservoir computing potential. These actuators are composed of active shape memory alloy wires and a passive material to magnify the overall deflection. However, the dynamic modeling of these actuators is difficult due to both shape memory alloy characteristics and the nonlinearity of the passive layer. Here, a hybrid dynamical model is proposed that couples the phase kinetics and thermal modeling for the shape memory alloy with a dynamic Cosserat beam model. This hybrid model is benchmarked against experimental linear and morphing actuators resulting in a root mean squared error of 0.87 mm for the linear actuator and root mean squared error of 1.34 and 1.42 mm for the two morphing actuator configurations evaluated in this work. This model applies continuous phase kinetic equations in a comprehensive hybrid dynamical model to accurately simulate the hysteretic transition of the alloy, which is then coupled to a high deformation beam model. This work can expand the capability and design of novel morphing actuators to achieve specified dynamic characteristics for increased application in robotic fields.

Collaborative optimization of multi-physical fields for composite electromagnetic linear actuators

Collaborative optimization of multi-physical fields for composite electromagnetic linear actuators

Enhanced electromechanical performance of Nafion actuator doped by poly(ethylene glycol)‐grafted graphene oxide

AbstractCurrent ionic polymer–metal composite (IPMC) actuators have severe actuation drawbacks (i.e. low force output and poor stability), hampering their applications. To address these issues, poly(ethylene glycol)‐grafted graphene oxide (PEG‐GO) is synthesized and incorporated into a Nafion matrix, thus producing a PEG‐GO hybrid Nafion film with better physiochemical properties for fabricating a high‐performance, low‐cost IPMC actuator. The modification of PEG to GO not only prevents GO agglomeration and sedimentation, but also avoids loss of PEG in water. Driven by a 0.2 Hz, 2.5 V electric field, the hybrid IPMC actuator exhibits superior electromechanical behaviors, i.e. a swing angle of 110.3°, a blocking force of 6.89 mN and a stable working time of 485 s, respectively increasing by 92%, 209% and 294% when compared to a pure Nafion actuator. © 2024 Society of Chemical Industry.

Topological optimal design of composite magnetic actuators to improve driving force and thermal conductivity

Topological optimal design of composite magnetic actuators to improve driving force and thermal conductivity

A humidity-driven film with fast response and continuous rolling locomotion

The widespread availability and easy accessibility of humidity make it essential to explore simple and low-cost methods to prepare structurally and materially efficient humidity-driven actuators with spontaneous and continuous locomotion to facilitate the application of bionic devices, intelligent sensors, and soft robots. Herein, this paper reports a humidity-driven monolayer film actuator. It is self-assembled from agarose (AG) and graphene oxide (GO) modified with polyvinylpyrrolidone (PVP), referred to as PGO, using a simple casting method. The PGO/AG composite film actuator exhibits an ultra-fast humidity response time (124.58° s−1) and recovery time (18.87° s−1), enabling rapid rolling locomotion driven by water evaporation. Notably, the programmable surface patterning of the PGO/AG composite film actuator with graphite results in a shorter single rolling time (0.43 s) and a faster rolling speed (28.73 mm s−1). Based on these advantages, the PGO/AG film actuator can mimic the opening and closing of flowers, mimosas, and fast-crawling robot driven by periodic water vapor (9.9 body length min−1). This finding provides new insights into the design of multifunctional actuators based on humidity-driven films.

Adaptive fixed-time fuzzy fault-tolerant control for robotic manipulator with unknown friction and composite actuator faults

This paper exploits the issue of fixed-time (FT) tracking control (TC) for uncertain robotic manipulator systems (RMS) with composite actuator faults (CAFs), unknown disturbances and joint friction. The fuzzy logic system (FLS) algorithm is introduced to fit the unknown uncertainties including unmodeled parameters, CAFs and joint friction of the RMS, after which a relevant updating algorithm is employed to generate the unidentified boundary of the plant disturbance and FLS approximation error. Then a novel adaptive fuzzy sliding mode (SM) fault-tolerant controller is synthesized, which not only guarantees the boundedness of estimation errors of the involved adaptive parameters, but also actualizes the reachability of the predevised sliding surface. Furthermore, the proof that the system trajectories can achieve the FT convergence to the expected position signals, is then provided on account of the FT stability theory. Ultimately, simulation experiments exhibit the rationality based upon the current control algorithm.

Investigation of free vibration of piezoelectric actuator reinforced with functionally graded Boron Nitride nanotube using timoshenko beam model and differential quadrature method

The vibrational characteristics and natural frequencies of Boron Nitride Nanotube (BNNT)-reinforced piezoelectric beams, based on the Timoshenko model, have been studied for the first time in this paper. Four types of functionally graded (FG) distribution patterns of BNNT reinforcements were considered for the FG-BNNT-reinforced piezoelectric beam. It is assumed that the material properties of FG-BNNT-reinforced beams are estimated using the Representative Volume Element (RVE) micromechanical model. The FG-BNNT-reinforced piezoelectric beam with different Boundary Conditions (BCs) is exposed to electrical voltage. Coupled partial differential equations of the system have been derived with the aid of Hamilton's principle and then converted into corresponding dimensionless equations using dimensionless variables. The differential quadrature method (DQM) has been used to obtain the natural frequencies and shape modes. According to the convergence analysis, twelve grid points were enough to obtain an accurate result for the analysis. To confirm the accuracy and reliability of the present study, the obtained results were validated with frequencies from the literature. Also, the effects of BNNT volume fraction and its reinforcement pattern, as well as applied voltage, on dimensionless natural frequencies have been investigated for different BCs. The results show that applying electric loadings can be utilized as well as controlling parameters to modify the resonance frequency of the composite actuator. More specifically, it is shown that applying voltages to a FG-BNNT-reinforced piezoelectric beam changes the natural frequency for each reinforcement pattern, BCs, and mode numbers. Such ability could be employed when designing reinforced piezoelectric composites for vibrational applications.

Numerical analysis of an innovative solar collector utilizing bistable composite laminates and macro fiber composite actuators

Innovative designs for solar collectors have attracted substantial academic and industrial interests owing to the high efficiency of solar panels in the recent past. This paper proposes the analysis and numerical design of a novel solar collector model composed of bistable laminates bonded with Macro Fiber Composite (MFC) actuators and solar cells. The bistable cross-ply laminate serves as the steering mechanism in this design by providing multiple stable shapes for the innovative solar collector design. Bistable morphing structures have received growing interest in aerospace structures and wind turbines due to their rapid shape-changing ability in response to changes in operating conditions, and this paper aims to integrate them more into the solar energy sector. The snap-through and snap-back motion of bistable laminates can be controlled by the voltage inputs of MFC actuators. The change of bistable laminate shape holds the solar cell in a position approximately at the latitude angle of the place to capture maximum solar energy. A systematic finite element parametric study has been performed to identify the optimum size and location of MFC actuators to achieve an energy-efficient snap-through and snap-back transition. As a result, a numerical design of a solar collector with six bistable elements has been proposed. In order to check the feasibility of the proposed designs, a numerical study has been performed to evaluate the total energy output and to optimize the solar panel tilt angle. ASHRAE’s solar irradiation model proposed in the literature has been used to identify the optimum solar panel tilt angle for maximum annual solar irradiation. This innovative solar collector model has demonstrated promising results, holds the potential for widespread application across various engineering domains, and paves the way for increased adoption of intelligent structures in everyday life.

Development of a novel two-way 3D printed flexible spiral composite actuator based on shape memory alloy wire and its control

Soft robotics find its applications across numerous of scientific and industrial fields, spanning from medicine and surgery to gripper technology, assistive devices, and exploration in underwater and space. The study introduces a soft actuator design for soft robotics, produced using 3D printing technology, offering an efficient alternative to traditional molding and curing methods. A shape memory alloy wire is integrated to the spiral body printed using a flexible filament. The spiral enhances the actuation stroke (AS) to 2 cm for a wire of 189 mm in length, while actuation in the literature is typically accomplished through an axial AS of 3%–5% of the wire’s length. Four types of spirals with increasing gaps are prepared to observe the cooling effect. Their performances are evaluated in terms of AS and time through image processing in order to determine the optimal configuration. An electrical current constraint is established to prevent potential damage, and spiral control is attained using a proportional–integral–derivative controller. Moreover, a pick and place operation showcases the spiral’s ability to autonomously lift a gripped object weighing 6.5 g, achieving a specific displacement of 6.5 mm. Subsequently, the object is lifted down to its initial position using a two-way actuator that utilizes the stored energy within the spiral’s structure and elastic effect. The proposed actuator has the potential to be widely applied across various soft robotic applications, including medical robots, delicate gripping robots, and bioinspired robots.

Development of IPMC actuators with high bending uniformity and orientation

Ionic polymer-metal composite (IPMC) actuators have attracted considerable scientific interest in the field of robotics and artificial muscles due to their low operating voltage, high strain capacity, and lightweight. However, the non-uniform bending of IPMC actuators affects their control accuracy and limits their potential applications. In this work, the surface voltage of IPMC actuators was measured and the internal electric field distribution was numerically computed. It was concluded that the non-uniform bending is mainly due to the non-uniform distribution of hydrated cations inside the IPMC as a result of the inhomogeneous electric field. The bending uniformity is improved by sputtering a gold layer on the surface of the IPMC actuator, and a support strip is introduced to limit the bending of the IPMC in the width direction, resulting in an improvement of its pointing characteristics. It is found that the bending uniformity of IPMC improved by 35.27% and 119.48% by sputtering at an input voltage of 2.5 V and 5 V respectively. When the input voltage is fixed at 2.5 V and 5 V, the bending in the width direction is reduced by 75.68% and 93.12% with the support structure, respectively.

Ionic Liquid Crystal-Polymer Composite Electromechanical Actuators: Design of Two-Dimensional Molecular Assemblies for Efficient Ion Transport and Effect of Electrodes on Actuator Performance.

We present the development of free-standing ionic liquid crystal-polymer composite electrolyte films aimed at achieving high-frequency response electromechanical actuators. Our approach entails designing novel layered ionic liquid-crystalline (LC) assemblies by complexing a mesomorphic dimethylphosphate with either a lithium salt or a room-temperature ionic liquid through the formation of ion-dipole interactions or hydrogen bonds. These electrolytes, exhibiting room-temperature ionic conductivities on the order of 10-4 S cm-1 and wide LC temperature ranges up to 77 °C, were successfully integrated into porous polymer networks. We systematically investigated the impact of ions and electrodes on the performance of ionic electroactive actuators. Specifically, the Li+-based liquid crystal-polymer composite actuator with PEDOT:PSS electrodes demonstrated the highest bending deformation, achieving a strain of 0.68% and exhibiting a broad frequency response up to 110 Hz, with a peak-to-peak displacement of 3 μm. In contrast, the ionic-liquid-based liquid crystal-polymer composite actuator with active carbon electrodes showcased a bending response at a maximum frequency of 50 Hz and a force generation of 0.48 mN, without exhibiting the back relaxation phenomenon. These findings offer valuable insights for advancing high-performance electromechanical systems with applications ranging from soft robotics to haptic interfaces.

Aerodynamic Modeling and Design Optimization of a Variable-Camber Piezocomposite Rotor

Multirotor vehicles typically use either complex mechanisms to vary blade pitch angle or speed control to vary thrust and torque to attain stability and maneuverability. Alternatively, thrust and torque can be varied by morphing the blades without the use of complex mechanisms and without varying the rotor speed. This method could be faster to change thrust, more efficient, and it may require fewer mechanical components. This paper presents an experimentally validated aerodynamic model with an empirical static-aeroelastic correction to predict the thrust and torque coefficient of a mechanism-free rotor with Macro-Fiber Composite actuators. A variable-camber piezocomposite rotor prototype is experimentally tested on a static-thrust setup. The experiment is used to identify the so-called unknown coefficients of the model (e.g., related to the shape of the blade induced by the piezoelectric device) and to identify a correction to account for flow-induced deformations. Using the identified model, several parametric analyses are conducted to predict thrust and torque coefficients as a function of rotor speed and the electrical excitation of the piezocomposite actuators. In addition, the model is used for design optimization, leading to several optimal designs based on a limited parameter space. Three different objective functions are used: maximizing thrust, minimizing torque, and maximizing thrust-to-torque ratio. The operational aerodynamic characteristics of these designs are also presented.

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.