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The control mechanism of jet vectoring using synthetic jet actuators is investigated. The final deflection angle of the primary jet is a result of the primary jet controlled by synthetic jets at three different regions. The lower static pressure near the primary jet exit induced by the synthetic jet, the entrainment and absorption of the primary jet fluid by the synthetic jet during the blowing and the suction stroke, the coupling and interaction between the vortices of synthetic jet and the shear layer of the primary jet are the main control mechanisms for the synthetic jet actuator vectoring a primary jet. The main factors influencing jet vectoring are analyzed and summarized, and a preparatory model for jet vectoring using synthetic jet actuator is presented.

To avoid the delamination of bimorph actuator and enhance the performance of the room-temperature type functionally graded (RTFG) piezoelectric bending actuator, the high temperature type FG (HTFG) piezoelectric bending actuator was designed and fabricated. The material compositions with different dielectric and piezoelectric constants were selected from the Pb(Ni_1/3N_b2/3)O₃-PbZrO₃-PbTiO₃ (PNN-PZ-PT) family, and used as the five layers in the HTFG piezoelectric actuator. Compared with the FG actuator, the HTFG actuator has advantages for applications at high temperature. The durability of the fabricated HTFG piezoelectric actuators was measured in a vibration test and compared with that of the bimorph actuator to evaluate the improvement of performance. The results show that the durability of the HTFG piezoelectric actuators is much higher than that of the bimorph actuator.

Ferromagnetic shape memory alloy (FSMA) is one of the smart materials which finds increasing industrial applications. This paper deals with the effect of Mn substitution for Ga on martensitic and magnetic transformation temperature of polycrystalline Ni–Mn–Ga alloy prepared in argon atmosphere. The prepared alloy has been characterized by means of scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and superconducting quantum interference device (SQUID). Magnetic property of alloy has been analyzed with vibrating sample magnetometer (VSM). From the VSM measurement, it is studied that the saturation magnetization of polycrystalline ferromagnetic shape memory occurs at high magnetic field. The main finding of this article is the raise in transformation temperature by 28 K/atom. As the working temperature is above room temperature, it seems to be a promising candidate for practical applications. The result reported here may help for further research in the field of polycrystalline Ni–Mn–Ga alloy.

This paper presents an electromechanical coupled dynamic equation for the lateral-flexural and torsional vibrations of a flexible ring for an electromechanical integrated electrostatic harmonic actuator as well as the equation of the forced response of the electromechanical integrated electrostatic harmonic actuator to voltage excitation. By solving these equations, the natural frequency and vibration modes of the flexible ring for the actuator are investigated. Changes in the natural frequency with respect to the main system parameters are also examined and the dynamic responses of the actuator to voltage excitation obtained.

Recently, the elderly population and excessive use of multimedia devices are increasing, which contribute to the growing number of patients with hearing loss. Hearing aids are used as a hearing rehabilitation method for patients with hearing loss and can be classified as air conduction and bone conduction according to the sound transmission pathway. Bone conduction is advantageous over sound transmission as it does not affect the eardrum. Bone conduction systems are divided into BAHA, Bone Bridge and B81 according to the vibration transmission method. BAHA has disadvantages as it can result in skin diseases and has inconveniences, and patients are reluctant to accept Bone Bridge because it has to be implanted into the temporal bone. Due to its location on the skin, B81 can solve these problems; however, this method may reduce transmission efficiency. In this paper, we have proposed a resonance frequency analysis model of a curved beam diaphragm to solve these problems. The proposed method involved a natural frequency equation with derived parameters. An improved efficiency (vibration transmission) was confirmed using the fabricated diaphragm. In the future, the proposed method may be used in various fields.

Hearing loss in people is increasing because of a rise in the usage of wireless audio multimedia devices. Hearing aids are used as representative hearing rehabilitation devices. Bone conduction hearing aids are recommended for problems in the eardrum and middle ear. Bone conduction is classified according to the driving method into two types, electromagnetic and piezoelectric. Electromagnetic bone conduction causes skin disease and aesthetic problems due to transplantation, high power consumption, and external interference. Piezoelectric bone conduction converts electrical energy into mechanical vibrations, and the characteristics change linearly with size. However, the driving force of ear canal insertion of the piezoelectric body is limited because of the ear canal anatomy. In this paper, a piezoelectric actuator with a bridge structure inserted into the ear canal is proposed. The proposed method is that the displacement amplification ratio was derived using the formula of a bridge-type structure, and the displacement and resonance frequency were derived by finite element analysis (FEA) using different variables. The piezoelectric actuator was fabricated on the basis of FEA simulation results and verified through an artificial mastoid for stimulation in the ear canal. It is expected that the proposed piezoelectric actuator can be used in the various fields for sound and precision control.

A synthetic jet actuator (SJA) is one of the most widely used active flow control device which uses a vibrating diaphragm enclosed within a cavity to generate the fluid jet. The effectiveness of the actuator greatly depends upon the design of cavity and orifice and the diaphragm properties. A lot of emphasis is being laid on the cavity and orifice design, but very few literatures can be found dealing with the diaphragm of the SJA. Thus, in this paper a study of the SJA diaphragm actuated by piezoelectric ceramics of different geometries is being presented. Three different diaphragm materials — brass, poly-silicon and aluminum and five different geometries of the piezoelectric actuators — annular disc shaped actuator patch, annular shaped actuator, rectangular shaped actuator patch and circular disc shaped actuator patch and two cantilever arrangements are being considered. A static analysis is carried out and a comparison of the parameters which affect the performance of the SJA is done. Frequency response analysis is also carried out to obtain a better understanding of the diaphragm's structural characteristics. The results thus obtained show that an annular disc piezoelectric patch configuration shows the best behavior as compared to the other actuator configurations and is closely followed by circular disc piezoelectric patch configuration.

The Mimosa Pudica is an action plant that closes its leaves when given a stimulus. The plant integrates both sensing and actuating mechanisms, and the distinctive motion is about a hinge-like point, the pulvinus, making the characterization of the motion attractive. In this project, experiments were set up to measure the characteristics of the plants in the goal to estimate the possibility to produce micro-actuator based on a similar principle. The signal speed, the sensitivity, the actuator speed, the power, the torque produced by the plant were measured by using different sensors. The results showed that the torque is dependent on the diameter of the pulvinus and that actuator could reach a top angular velocity of 1 rad/s. We developed a phenomenological model to describe the behavior of the plant that could match experimental results and propose an original physical description of the mechanism inside the plant by considering a phase transition behavior instead of the classical ion channel model. Finally, the plant actuator energy density is also compared with other known micro-actuators and the possibility to use the plant as a micro-actuator is discussed.

This paper describes an approach to construct models of dielectric elastomers undergoing dissipative processes, such as viscoelastic, dielectric and conductive relaxation. This approach is guided by nonequilibrium thermodynamics, characterizing the state of a dielectric elastomer with kinematic variables through which external loads do work, as well as internal variables that describe the dissipative processes. Within this approach, a method is developed to calculate the critical condition for electromechanical instability. This approach is illustrated with a specific model of a viscoelastic dielectric elastomer, which is fitted to stress-strain curves of a dielectric elastomer (VHB tape), measured at various strain rates. The model shows that a higher critical voltage can be achieved by applying a constant voltage for a shorter time, or by applying ramping voltage with a higher rate. A viscoelastic dielectric elastomer can attain a larger strain of actuation than an elastic dielectric elastomer.

When the electrocatalyst, platinum, was coated on polyelectrolyte gel surfaces and was immersed into an acidic formaldehyde (HCHO) solution, an input direct current (DC) current would produce oscillatory voltages on the surfaces of the ionic-polymer-metal-composites (IPMC) actuator. The oscillatory voltages on the two electrodes caused the concurrent migration of counter-ion clusters, and ultimately a self-oscillatory bending of the gel actuator was realized. To model the complex multiphysics processes involved in this gel actuator with a typical large length-to-height ratio, the electrochemical processes occurred along each cross section through the height were regarded identically as a one-dimensional process, and the mechanical deformation of the actuator was simplified as the bending of a beam. Motivated by the development of micro-grippers and tactile sensors, self-oscillations of gel actuator with variable cross sections and subject to a spring constraint were simulated for the first time. The procedure outlined herein presents a versatile framework for the design, analysis and optimization of self-oscillating gel actuators.

The volume expansion of palladium by electrochemical hydrogen absorption and desorption is used as an actuating mechanism. Palladium films are obtained by electrodeposition from aqueous solution. Actuation based on potentiostatic and galvanostatic signals is investigated in acid and alkaline solutions. Performance characteristics of the actuator are determined. The reversibility of the actuator is hindered by the embrittlement of the Pd layer. The response time strongly depends on the layer thickness (increases for thicker films) and potential (decrease for more cathodic values). The maximum theoretical energy density of the Pd–H actuator is about 5000 kJ/m³. In this work, it is experimentally determined to be around 100–200 kJ/m³.

Piezoelectric actuators operating in piezoelectric-induced strain/stress or electromechanical resonance-induced vibration or wave-motion friction drive mechanism have shown many advantages over traditional electromagnetic motors, especially, when miniaturizing into millimeter-scale size, while magnetoelectric actuators operating in magnetostrictive mechanism are capable of piezoelectric self-sensing and remote operation under an applied magnetic field. This paper summarizes the recent progresses in piezoelectric ceramic and single crystal materials based actuators and micromotors, ferromagnetic/ferroelectric laminated magnetoelectric actuators, including rotary, linear, planner, and spherical motion actuators, and bending motion magnetoelectric actuators. Their driving mechanisms, operation properties, and applications are also explained.

Upcoming large telescopes are based on Segmented Mirror Telescope (SMT) technology which uses small hexagonal mirror segments placed side by side to form the large monolithic surface. The segments alignment needs to be maintained against external disturbances like wind, gravity, temperature and structural vibration. This is achieved by using three position actuators per segment working at few-nanometer scale range along with a local closed loop controller. The actuator along with a controller is required to meet very stringent performance requirements, such as track rates up to 300nm/s (90mN/s) with tracking errors less than 5nm, dynamical forces of up to $\pm 40$N, ability to reject disturbances introduced by the wind as well as by mechanical vibration generated in the mirror cell, etc. To conduct these performance tests in more realistic manner, we have designed and developed a Dynamic Loading Assembly (DLA) at Indian Institute of Astrophysics (IIA), Bangalore. DLA is a computer controlled force-inducing device, designed in a modular fashion to generate different types of user-defined disturbances in extremely precise and controlled manner. Before realizing the device, using a simple spring-mass-damper-based mathematical model, we ensured that the concept would indeed work. Subsequently, simple concept was converted into a detailed mechanical design and parts were manufactured and assembled. DLA has static and dynamic loading capabilities up to 250N and 18N respectively, with a bandwidth sufficient to generate wind disturbances. In this paper, we present various performance requirements of SMT actuators as well as our effort to develop a dynamic loading device which can be used to test these actuators. Well before using DLA for meaningful testing of the actuator, the DLA itself have gone through various tests and improvements phases. We have successfully demonstrated that DLA can be used to check the extreme performance of two different SMT actuators, which are expected to track the position/force with a few nanometer accuracy.

Ferromagnetic Shape Memory Alloys (FSMAs) such as Ni-Mn-Ga have attracted significant attention over the last few years. As actuators, these materials offer high energy density, large stroke, and high bandwidth. These properties make FSMAs potential candidates for a new generation of actuators. The preliminary dynamic characterization of Ni-Mn-Ga illustrates evident nonlinear behaviors including hysteresis, saturation, first cycle effects, and dead zone. In this paper, in order to precisely control the position of an FSMA actuator a dynamic model is developed. The Ni-Mn-Ga actuator model consists of the dynamics model of the actuator, the kinematics of the actuator, the constitutive model of the FSMA material, reorientation kinetics of the FSMA material, and the electromagnetic model of the actuator. Furthermore, a constitutive model is proposed to take into account the elastic deformation as well as the reorientation. Simulations results are presented to demonstrate the dynamic behavior of the actuator.