Photostrictive Actuators Research Articles

Stress-tuning the bulk photovoltaic response in polycrystalline bismuth ferrite films

Bulk or anomalous photovoltaic effect in ferroelectrics has recently sparked interest due to the generation of switchable photovoltages that are not limited by the bandgap of the material. The development of strategies to tune its magnitude is a key for the development of light-driven devices, e.g., photostrictive actuators, photostrictive sensors, or reconfigurable waveguides. In this paper, the bulk photovoltaic effect of polycrystalline solution-deposited bismuth ferrite thin films is studied under different stress conditions induced by different substrates and quantified using a direct strain assessment via x-ray diffraction. An increase in the short-circuit bulk photovoltaic current of 150% is observed with a change from a compressive stress of 0.54 GPa to a tensile stress of 0.93 GPa. This change is attributed to intrinsic piezophotovoltaic effect, demonstrating the potential to strain engineer the bulk photovoltaic effect in thin films.

Fuzzy logic based active vibration control using novel photostrictive composites

Although conventional actuators like piezoelectric and electrostrictive are efficient, but they required hard wiring, which contaminates the control signal and adds to the weight of the structure. The current study presents a wireless control strategy using photostrictive actuators. Owing to the fortunate combination of photovoltaic effect and converse piezoelectric effect, a photostrictive actuator can generate mechanical strain, when irradiated with light intensity. Limited choices of photostrictive material with high electromechanical coupling coefficient give the motivation to design photostrictive composites. The finite element-based formulation incorporating fuzzy logic controller is employed to study the active vibration control response of cantilever structure when equipped with photostrictive composite actuator. A parametric study has been carried out to study the influence of inclusion’s volume fraction on wireless active vibration control of the structure. Control merits have been defined to compare the control performance of different composites. It is found that particulate composites are the better choice for lightweight structure and fiber composites are better if there is no weight constraint.

Nonlinear forced vibration of a curved micro beam with a surface-mounted light-driven actuator

This study addresses the nonlinear forced vibration of a deep curved microbeam with a noncontact actuator. The photostrictive actuator is subjected to an ultraviolet-switching excitation and the governing equations are derived based on the couple stress theory (CST). The von Kármán geometric nonlinearity is utilized to obtain the fundamental equations of thin curved beams in a curvilinear coordinate system. According to the type of boundaries, inextensional condition is applied as a new strategy in such a structure to obtain solution analytically. By using the Galerkin method, the equation of motion is discretized and reduced to the ordinary differential equation. Nonlinear analysis is then carried out on the reduced-order equation by employing the multiple scales method. Based on the obtained results, for the first time, it is reported that qualitative and quantitative response of a deep curved beam is highly affected by the geometrical characteristics and the micro-interactions. It is found that considering the deepness term (1+z/R) in a curved beam makes nonlinear behavior more prominent, whereas ignoring this term could lead to erroneous dynamic predictions particularly when the beam thickness increases. Furthermore, the prominent role of the radius of curvature on the large-amplitude response of the system is investigated. It is shown that as the beam's curvature increases, namely when the beam becomes deeper or a straight beam tends to a curved one, contribution of the nonlinear behavior of the system increases.

Multi-mode optimal fuzzy active vibration control of composite beams laminated with photostrictive actuators

Firstly, a multi-field coupling finite element formulation of composited beam laminated with the photostrictive actuators is developed in this paper. Moreover, an optimal fuzzy active control algorithm is also proposed on the basis of the combination of optimal control and fuzzy one. This method opens a new avenue to resolve the contradiction between the linear system control method and nonlinear actuating characteristics of photostrictive actuators. The desired control for suppressing multi-modal vibration of photoelectric laminated beam is firstly obtained through optimal control and then the fuzzy control is used to approach the desired mechanical strain induced by photostrictive actuators. Thus, the multi-mode vibration control of beam is realized. In the design process of optimal fuzzy controller, the design of fuzzy control is independent of optimal control. The simulation results demonstrate that the proposed control method can effectively realize multi-modal vibration control of photoelectric laminated beams, and the control effect of optimal fuzzy control is better than that of optimal state feedback control.

Artificial Muscles: Mechanisms, Applications, and Challenges.

The area of artificial muscle is a highly interdisciplinary field of research that has evolved rapidly in the last 30 years. Recent advances in nanomaterial fabrication and characterization, specifically carbon nanotubes and nanowires, have had major contributions in the development of artificial muscles. However, what can artificial muscles really do for humans? This question is considered here by first examining nature's solutions to this design problem and then discussing the structure, actuation mechanism, applications, and limitations of recently developed artificial muscles, including highly oriented semicrystalline polymer fibers; nanocomposite actuators; twisted nanofiber yarns; thermally activated shape-memory alloys; ionic-polymer/metal composites; dielectric-elastomer actuators; conducting polymers; stimuli-responsive gels; piezoelectric, electrostrictive, magnetostrictive, and photostrictive actuators; photoexcited actuators; electrostatic actuators; and pneumatic actuators.

Displacement Control of Photostrictive Actuators for Vibration Control with the Aid of Fuzzy Logic Control along with PSO Algorithm

Vibration in industrial equipment can be continuously monitored for unusual types of operating conditions and the resultant potential failures. Photo restrictive materials, exhibiting light-induced strains, are of interest for future generation wireless remote control photo-actuators, micro-actuators, and micro-sensors applications that exhibit large photo restriction under uniform illumination of ultraviolet light. In our proposed method, we are using fuzzy logic to illustrate the light intensity based on which the distance between the two modes is reduced using Particle Swarm Optimization (PSO) algorithm in such a way as to provide a lesser vibration result. In our proposed technique, the input is used as the velocity of the source and the displacement of the modes, the corresponding output being the light intensity. The optimal light intensity is chosen based on the displacement by means of which the corresponding displacement is again optimized to an extent desired using PSO algorithm to get further reduced vibration in the output. The accuracy of the PSO is done by comparing the result with normalized value and with the Genetic Algorithm and has proved that our proposed method produces optimal result. Thus our proposed method is projected to increase the efficiency in the output with a significant reduction in displacement.

Multimodal Vibration Control of Photo-Electric Laminated Thin Cylindrical Shells Via Self-Organizing Fuzzy Sliding Mode Control

In this paper, a novel multipiece actuator configuration is first proposed. This configuration exhibits several advantages over the existing ones, such as: (1) the ability to overcome the deficiency of one-way actuation of PbLaZrTi (PLZT) actuators and (2) all of the actuators in this configuration being placed on the inner surfaces of a thin cylindrical shell and the removal of extra electrical wires between the end surfaces of the actuators. A new index of modal control factors is defined, and an optimization method for allocating actuator is proposed. By using the proposed method, the PLZT actuators can be located in an optimum position. Moreover, in view of the nonlinear and time-variant characteristics of photostrictive actuators, a self-organizing fuzzy sliding mode control (SOFSMC) method is established to attenuate multimodal vibration of photo-electric laminated thin cylindrical shells. A multilevel sliding mode surface is defined as fuzzy input and the SOFSMC method is used to infer the applied light intensity. Its control rule bank can be developed and adjusted continuously via online learning. In addition, using fuzzy sliding mode, the chatter inherent in conventional sliding mode control is therefore managed effectively while ensuring sliding mode behavior. Case studies demonstrate that the proposed approach can efficiently suppress multimodal vibration of photo-electric laminated thin cylindrical shells. It is also founded that SOFSMC can achieve better control effect than fuzzy neural network control (FNNC).

Simultaneous optimization of photostrictive actuator locations, numbers and light intensities for structural shape control using hierarchical genetic algorithm

The present paper introduces an investigation into simultaneous optimization of the PbLaZrTi-based actuator configuration and corresponding applied light intensity for morphing beam structural shapes. A finite element formulation for multiphysics analysis of coupled opto-electro-thermo-mechanical fields in PbLaZrTi ceramics is derived and verified with the theoretical solution and the commercial software ANSYS. This element is then used to simulate beam bending shape control using the orthotropic PbLaZrTi actuators and the simultaneous optimization. In this procedure, the controlling and geometrical variables are simultaneously optimized via a hierarchical genetic algorithm. A bi-coded chromosome is proposed in a hierarchical mode, which consists of some control genes (i.e. actuator location and number) and parametric genes (i.e. applied light intensity). Whether the parametric gene is activated or not is managed by the value of the first-grade control genes. The numerical results demonstrate that the achieved beam bending shapes correlate remarkably well with the expected ones and the simultaneous optimization of photostrictive actuator locations, numbers and light intensities can result in optimal actuator layout with less PbLaZrTi actuators and irradiated light energy. The simulation results also show that the hierarchical genetic algorithm has more superior performance over the conventional real-coded genetic algorithm.

Fuzzy neural network multi-modal vibration control of thin cylindrical shells laminated with photostrictive actuators

In this paper, the multi-modal vibration control of a simply supported thin cylindrical shell laminated with photostric- tive actuators is studied. First, the photo-electric/shell coupling equations of a cylindrical shell laminated with the multi-layer actuator configuration are presented. Moreover, in view of the nonlinear and time-variant characteristics of photostrictive actu- ators, a fuzzy neural network (FNN) controller with adaptive learning rates is developed to attenuate multi-mode vibration of photo-electric laminated thin cylindrical shells. This approach has learning ability for responding to the time-varying charac- teristic of the multi-mode vibration induced by disturbance. Its control rule bank can be established and modified continuously by on-line learning. Finally, numerical simulation results are provided to show that the proposed intelligent controller could effectively suppress multi-mode vibration of photo-electric laminated thin cylindrical shells.

Effects of photostrictive actuator and active control of flexible membrane structure

The purpose of this paper is to investigate the flexible structure of parabolic shell using photostrictive actuators. The analysis is made to know its dynamic behavior and light-induced control forces for coupled parabolic shell. The effects of an actuator location as well as membrane and bending components under the control action have been analyzed considering the approximate spherical model. The parabolic membrane shell accuracy is being mathematically approximated and validated comparing the light induced control forces using approximate equivalent spherical shell model. The parabolic shell with kapton smart material and photostrictive actuators has been used to formulate the governing equation in the transverse direction. The Kirchhoff-Love assumptions are used to obtain the governing equation of shell with actuator. The mechanical membrane forces and bending moments for parabolic thin shell with actuator is used to analyze the dynamic effect. The results show that membrane control action is much more significant than bending control action. Photostrictive actuators oriented along circumferential direction (actuator-2) can give better control effect than actuators placed along longitudinal direction (actuator-1). The slight difference is observed between spherical and parabolic shell for a surface with focal length to the diameter ratio of 1.00 or more than unity. Space applications often have the shape of parabolical shells or shell of revolution, due to their required focusing, aiming, or reflecting performance. The present approach is focused that photostrictive actuators can effectively control the vibration of parabolical membrane shell. Also, the actuator's location plays an important role in defining the control force.

Genetic algorithm based wireless vibration control of multiple modal for a beam by using photostrictive actuators

The lanthanum-modified lead zirconate titanate (PLZT) actuator, which are capable of converting photonic energy to mechanical motion, have great potential in applications of remote structural vibration control of smart structures and machines. In this paper, a novel genetic algorithm based controlling algorithm for multi-modal vibration control of beam structures via photostrictive actuators is proposed. Two pairs of photostrictive actuators are laminated with the beams and the alternation of light irradiation is in accordance with the changing of the corresponding modal velocity direction. The modal force indexes for beams with different boundary conditions are derived and a binary-coded GA is used to optimize the locations and sizes of photostrictive actuators to maximize the modal force index and guarantee the overall modal force index induced by two pairs of photostrictive actuators is positive. The control effect of multiple vibration modes of beams under irradiation of set/variable light intensity is analyzed. Numerical results demonstrate that the method is robust and efficient, and the use of strategically positioned actuator patches can effectively control the first two bending modes that dominate the structural vibration.

Independent modal variable structure fuzzy active vibration control of thin plates laminated with photostrictive actuators

Photostrictive actuators can produce photodeformation strains under illumination of ultraviolet lights. They can realize non-contact micro-actuation and vibration control for elastic plate structures. Considering the switching actuation and nonlinear dynamic characteristics of photostrictive actuators, a variable structure fuzzy active control scheme is presented to control the light intensity applied to the actuators. Firstly, independent modal vibration control equations of photoelectric laminated plates are established based on modal analysis techniques. Then, the optimal light switching function is derived to increase the range of sliding modal area, and the light intensity self-adjusting fuzzy active controller is designed. Meanwhile, a continuous function is applied to replace a sign function to reduce the variable structure control (VSC) chattering. Finally, numerical simulation is carried out, and simulation results indicate that the proposed control strategy provides better performance and control effect to plate actuation and control than velocity feedback control, and suppresses vibration effectively.

Finite Element Modeling of Photostrictive Optical Actuators

This article reports development of a finite element for analysis of photostrictive thin films. The photostrictive effect can be thought of as a superposition of a bulk photovoltaic effect and the converse piezoelectric effect. Photostrictive materials can produce strain as a result of irradiation from high-intensity light. Neither electric lead wires nor electric circuits are required. Thus, photostrictive actuators are relatively immune from electrical interference. They have potential use in numerous MEMS devices. In this article, the details of the developed photostrictive thin film finite element are given. The element has been implemented in an in-house finite element code. Results of two verification studies are given. A steel simply supported beam with one PLZT actuator bonded on top of the beam was analyzed. The finite element displacement computations for transverse deflection matched the analytical results computed by another author within about 2%. In a second comparison, transverse deflection for a silicon cantilever beam with a PLZT actuator bonded on the whole top surface of the beam was computed. The finite element computations matched the analytical analysis approach of another author within about 1%.

Independent modal variable structure fuzzy active vibration control of cylindrical thin shells laminated with photostrictive actuators

Photostrictive actuator, which can produce photodeformation strains under the activation of ultraviolet lights, is a new promising non-contact photoactuation technique for active vibration control of flexible structures. Generally, the membrane control action plays a major role in vibration control of flexible thin shell structures. However, it is unfortunate that the existing photostrictive actuator configuration can not induce negative membrane control forces. In this paper, a novel multi-layer actuator configuration is first presented to remedy this deficiency, followed by presenting the photostrictive/shell coupling equations of thin cylindrical shells laminated with the proposed multi-layer actuator configuration. Moreover, considering the time-variant and nonlinear dynamic characteristics of photostrictive actuator, variable structure self-adjusting parameter fuzzy active controller is explored to overcome disadvantages of conventional control schemes, in which off-line fuzzy control table is adopted. The optimal switching surface is derived to increase the range of sliding mode to facilitate vibration suppression. A continuous function is used to replace the sign function for reducing the variable structure control chattering. Finally, two case studies are carried out to evaluate the effectiveness of the proposed actuator configuration and the control scheme. Numerical simulation results demonstrate that the proposed actuator configuration is effective in shell actuation and control. It is also suggested that the proposed control strategy could give better control responses than the proportional velocity feedback.

Independent Modal Variable Structure Fuzzy Active Vibration Control of Cylindrical Thin Shells Laminated with Photostrictive Actuators

Photostrictive actuator, which can produce photodeformation strains under the activation of ultraviolet lights, is a new promising non-contact photoactuation technique for active vibration control of flexible structures. Generally, the membrane control action plays a major role in vibration control of flexible thin shell structures. However, it is unfortunate that the existing photostrictive actuator configuration can not induce negative membrane control forces. In this paper, a novel multi-layer actuator configuration is first presented to remedy this deficiency, followed by presenting the photostrictive/shell coupling equations of thin cylindrical shells laminated with the proposed multi-layer actuator configuration. Moreover, considering the time-variant and nonlinear dynamic characteristics of photostrictive actuator, variable structure self-adjusting parameter fuzzy active controller is explored to overcome disadvantages of conventional control schemes, in which off-line fuzzy control table is adopted. The optimal switching surface is derived to increase the range of sliding mode to facilitate vibration suppression. A continuous function is used to replace the sign function for reducing the variable structure control chattering. Finally, two case studies are carried out to evaluate the effectiveness of the proposed actuator configuration and the control scheme. Numerical simulation results demonstrate that the proposed actuator configuration is effective in shell actuation and control. It is also suggested that the proposed control strategy could give better control responses than the proportional velocity feedback.

Genetic algorithm based LQR vibration wireless control of laminated plate using photostrictive actuators

A photostrictive type of opto-electromechanical actuator activated by high-energy lights can introduce actuation and control effects without hard-wired connections. This paper addresses the controllability aspect in wireless vibration control of plate structures via photostrictive actuators. A modal force index, which has taken into account the mode number, the spatial distribution, and the dimension of the actuator, is chosen as an objective function to determine the optimal locations of photostrictive actuators. A linear methodology is proposed in this paper and the vibration equation is written in the standard state-space form. A binary-coded GA based combined optimal placement and LQR (linear quadratic regulator) control scheme has been incorporated, which maximizes the modal force index, the closed loop damping and minimizes input light intensity to the actuators. In the present method only three weighting factors have been used to search optimal Q and R matrices using GA, which reduces chromosome length and hence minimizes computational time. Numerical results demonstrate that the use of strategically positioned actuator patches can effectively control the fundamental modes that dominate the structural vibration.

Cylindrical Shell Control With Center- and Corner-Placed Photostrictive Skew-Quad Actuator Systems

Light-driven photostrictive actuators can induce control actions for wireless non-contact actuation and control of precision structures and systems. Conventional distributed actuators laminated on shells and plates usually only introduce uniform control forces and moments. Structural actuation and control based on uniform control forces and moments have been investigated for over two decades. This paper is to exploit a new photostrictive actuator design, i.e., a skew-quad (SQ) actuator system. This new distributed SQ actuator system laminated on shells and plates can introduce non-uniform control forces and moments. The new SQ actuator system is composed of four pieces of photostrictive materials and the inner two edges of each piece are bonded to a cross fixture. Under the irradiation of high-energy lights, each piece generates non-uniform control forces and moments, due to its uneven non-symmetrical boundary conditions. Modal actuation characteristics of a cylindrical shell coupled with the center-placed and corner-placed SQ actuator systems are evaluated respectively. A paired-design regulating positive/negative control forces of each actuator region is also proposed and evaluated to improve the control effectiveness of the center-located SQ actuator system. Parametric analysis proves improved control effectiveness of unsymmetrical shell modes.

A piezoelectric single-crystal ultrasonic microactuator for driving optics

At the millimeter scale, the motions or force out puts generated by conventional piezoelectric, magnetostrictive, photostrictive, or electromagnetic actuators are very limited. Here, we report a piezoelectric ultrasonic microactuator (size: 1.5 × 1.5 × 5 mm, weight: 0.1 g) made of PIN-PMN-PT single crystal. The actuator converts its high-frequency microscopic displacements (nanometer to micrometer scale) into a macro scopic, centimeter-scale linear movement of a slider via frictional force, resulting in a speed up to 50 mm/s and a very high unit volume direct driving force of 26 mN/mm(3) (which is ~100 times higher than a voice coil motor and ~4 times higher than a piezoceramic ultrasonic motor). This work shows the feasibility of using piezoelectric single-crystal-based ultrasonic microactuator for miniature drive of optics in next-generation mobiles and cameras.

Finite element modeling analysis of photostrictively driven optical actuators for excitationof microdevices

Photostriction is a phenomenon in which strain is induced in the sample by incident light. Inprinciple, this effect arises from a superposition of the photovoltaic effect, i.e. the generation oflarge voltage from the irradiation of light, and the converse piezoelectric effect, i.e. expansion orcontraction under the voltage applied. Photostrictive materials are ferrodielectric ceramicsthat have a photostrictive effect. Some photostrictive materials are (Pb, La)(Zr, Ti)O3 ceramicsdoped with WO3, called PLZT, which exhibit large photostriction under uniform illumination withhigh-energy light. They have potential use in numerous micro-electro-mechanical system(MEMS) devices where actuation of microbeams is a common phenomenon. The objectiveof this research is to develop and analyze a finite element model to study the feasibility ofphotostrictively driven actuators for excitation of microdevices. Much work hasbeen carried out toward developing microdevices which are capacitively driven orpiezoelectrically driven. The effect of different parameters such as actuator thickness,incident light intensity and convective heat transfer coefficient on the actuation of a beamusing thin film photostrictive actuators has been investigated. Also the derived finiteelement for static analysis of photostrictive thin films has been used to investigate theapplication of photostrictive actuators for different structures and various boundaryconditions of microbeams with various actuator locations and lengths. A successfulconclusion of these tasks will affirm the potential of the technology for use in actualmicrodevices.

Finite element simulation of wireless structural vibration control with photostrictive actuators

A recently emerging family of smart materials, photostrictive materials, exhibit large photostriction under uniform illumination of high-energy light. This photostriction mechanism arises from a superposition phenomenon of photovoltaic and converse piezoelectric effects. A photostrictive type of opto-electromechanical actuator activated by high-energy lights can introduce actuation and control effects without hard-wired connections. The control light intensity applied to the actuator is proportional to the transverse velocity at a positioned point, which is measured by a laser vibrometer. In this paper, photostrictive films are numerically analyzed to evaluate their use as wireless actuators for future remote vibration control of flexible structures. A novel opto-electromechanical solid shell finite element formulation is developed for accurate analysis of the multiple physics effects of photovoltaic, pyroelectric and thermal expansion of photostrictive materials. Available experimental data and analytical solutions have been used to verify the present finite element results. The simulation in this study demonstrates that the present formulation is very reliable, accurate and also computationally efficient and that the use of photostrictive actuators can provide good controllability of structural vibration.