Voltage Displacement Research Articles

Dry Electroactive Paper Actuator Based on Cellulose/Poly(Ethylene Oxide)—Poly(Ethylene Glycol) MicroComposite

Cellulose Electroactive Paper (EAPap) is an attractive material to construct biomimetic actuators and MEMS devices due to its lightweight, biodegradability, large displacement, and low actuation voltage. However, the performance of the actuator is sensitive to humidity levels. In this article, cellulose/poly(ethylene oxide) (PEO)—poly(ethylene glycol) (PEG) microcomposites were fabricated for EAPap actuators working at ambient humidity condition, and the effect of different PEO : PEG ratios (0.95 : 0.05 to 0.99 : 0.01) on the actuation behavior was investigated. Based on the bending displacement, power consumption, and durability, 0.95 :0.05 ratio was identified as an optimum ratio of PEO : PEG to blend with cellulose for EAPap actuator. The actuation mechanism of the cellulose/PEO—PEG actuator was addressed.

Thermal Actuation Based 3-DoF Non-Resonant Microgyroscope Using MetalMUMPs

High force, large displacement and low voltage consumption are a primary concern for microgyroscopes. The chevron-shaped thermal actuators are unique in terms of high force generation combined with the large displacements at a low operating voltage in comparison with traditional electrostatic actuators. A Nickel based 3-DoF micromachined gyroscope comprising 2-DoF drive mode and 1-DoF sense mode oscillator utilizing the chevron-shaped thermal actuators is presented here. Analytical derivations and finite element simulations are carried out to predict the performance of the proposed device using the thermo-physical properties of electroplated nickel. The device sensitivity is improved by utilizing the dynamical amplification of the oscillation in 2-DoF drive mode using an active-passive mass configuration. A comprehensive theoretical description, dynamics and mechanical design considerations of the proposed gyroscopes model are discussed in detail. Parametric optimization of gyroscope, its prototype modeling and fabrication using MetalMUMPs has also been investigated. Dynamic transient simulation results predicted that the sense mass of the proposed device achieved a drive displacement of 4.1μm when a sinusoidal voltage of 0.5V is applied at 1.77 kHz exhibiting a mechanical sensitivity of 1.7μm /°/s in vacuum. The wide bandwidth frequency response of the 2-DoF drive mode oscillator consists of two resonant peaks and a flat region of 2.11 kHz between the peaks defining the operational frequency region. The sense mode resonant frequency can lie anywhere within this region and therefore the amplitude of the response is insensitive to structural parameter variations, enhancing device robustness against such variations. The proposed device has a size of 2.2 × 2.6 mm2, almost one third in comparison with existing M-DoF vibratory gyroscope with an estimated power consumption of 0.26 Watts. These predicted results illustrate that the chevron-shaped thermal actuator has a large voltage-stroke ratio shifting the paradigm in MEMS gyroscope design from the traditional interdigitated comb drive electrostatic actuator. These actuators have low damping compared to electrostatic comb drive actuators which may result in high quality factor microgyroscopes operating at atmospheric pressure.

A new modeling and compensation approach for creep and hysteretic loops in nanosteering by SPM’s piezotubes

This paper addresses a new approach for compensation of nonlinear effects of creep and hysteresis on the piezotube scanners which are used in scanning probe microscopes. Although the significant contribution of nonlinearities, especially hysteresis, originates from noises, researchers did not introduce an effective model for this problem vividly. This paper develops a creep and hysteresis model that is generic, computationally efficient, and mathematically traceable such that it is applicable to random input functions such as undesired voltages, thermal field, eccentricity, and mechanical distortions after a long period of use. A modified Bouc–Wen model was obtained and by an effort-follow treatment, voltage displacement of piezotube was considered. For simultaneous creep and hysteresis modeling, a looseness characteristic was attached to the model. At first, from input voltage, the polarization and axial force were calculated. Then, from this force as an input to hysteresis–creep equations, nonlinearities were modeled. Comparison with experimental results shows that this approach is effective and introduces a new compensation algorithm for rate-independent nonlinearities.

Irradiation effect on dielectric properties of hafnium and gadolinium oxide gate dielectrics

Ionizing radiation effects on the electrical properties of HfO2, Gd2O3, and HfO2∕SiO2 based metal-oxide-semiconductor (MOS) capacitors have been studied. High-k dielectrics grown by atomic layer deposition and high-pressure Sputtering were exposed to photon radiation (18MeV photons). Capacitance-voltage curves, deep-level transient spectroscopy, conductance and flat-band voltage transients, and current-voltage techniques were used to characterize the samples. An increment in bulk dielectric trap densities has been observed when the samples were exposed to the ionizing radiation. These traps give rise to a flat-band voltage displacement, the extent of which depends on the gate dielectric used. High-k/silicon interface quality becomes worse after irradiation. An increment in the gate leakage current was also observed when irradiating the samples. Disorder-induced gap state density inside the insulator increases in the case of Gd2O3 MOS based samples, which seems to be the most affected by ionizing radiation.

Tracking control of hysteretic piezoelectric actuator using adaptive rate-dependent controller

With the increasing popularity of actuators involving smart materials like piezoelectric, control of such materials becomes important. The existence of the inherent hysteretic behavior hinders the tracking accuracy of the actuators. To make matters worse, the hysteretic behavior changes with rate. One of the suggested ways is to have a feedforward controller to linearize the relationship between the input and output. Thus, the hysteretic behavior of the actuator must first be modeled by sensing the relationship between the input voltage and output displacement. Unfortunately, the hysteretic behavior is dependent on individual actuator and also environmental conditions like temperature. It is troublesome and costly to model the hysteresis regularly. In addition, the hysteretic behavior of the actuators also changes with age. Most literature model the actuator using a cascade of rate-independent hysteresis operators and a dynamical system. However, the inertial dynamics of the structure is not the only contributing factor. A complete model will be complex. Thus, based on the studies done on the phenomenological hysteretic behavior with rate, this paper proposes an adaptive rate-dependent feedforward controller with Prandtl–Ishlinskii (PI) hysteresis operators for piezoelectric actuators. This adaptive controller is achieved by adapting the coefficients to manipulate the weights of the play operators. Actual experiments are conducted to demonstrate the effectiveness of the adaptive controller. The main contribution of this paper is its ability to perform tracking control of non-periodic motion and is illustrated with the tracking control ability of a couple of different non-periodic waveforms which were created by passing random numbers through a low pass filter with a cutoff frequency of 20 Hz.

Modeling of Piezoelectric Energy Harvesting from an L-shaped Beam-mass Structure with an Application to UAVs

Cantilevered piezoelectric energy harvesters have been extensively investigated in the literature of energy harvesting. As an alternative to conventional cantilevered beams, this article presents the L-shaped beam-mass structure as a new piezoelectric energy harvester configuration. This structure can be tuned to have the first two natural frequencies relatively close to each other, resulting in the possibility of a broader band energy harvesting system. This article describes the important features of the L-shaped piezoelectric energy harvester configuration and develops a linear distributed parameter model for predicting the electromechanically coupled voltage response and displacement response of the harvester structure. After deriving the coupled distributed parameter model, a case study is presented to investigate the electrical power generation performance of the L-shaped energy harvester. A direct application of the L-shaped piezoelectric energy harvester configuration is proposed for use as landing gears in unmanned air vehicle applications and a case study is presented where the results of the L-shaped — energy harvester — landing gear are favorably compared against the published experimental results of a curved beam configuration used for the same purpose.

Output properties of fiber optic sensor for micro-displacement measurement at 77 K and 4.2 K

Fiber optic sensors for micro-displacement measurement are applied to displacement measurement of superconductors. Output characteristics of a fiber optic sensor were measured at 77K and 4.2K. The results show that the linearity between output voltage ratio and displacement is good both at 77K and at 4.2K, and the sensitivity at 77K is higher than that at 4.2K.

A theoretical solution for the angular displacement of electrostatic one-degree-of-freedomtorsional microactuators

A theoretical solution for the angular displacement of electrostatic one-degree-of-freedom(one-DOF) torsional microactuators has been obtained as a function of the appliedvoltage and geometry. A nonlinear moment balance equation, representing thebehavior of the actuator, is theoretically solved for the angular displacementcorresponding to the applied voltage. The pull-in voltage and angular displacement arealso derived in closed forms to provide a guideline for the maximum voltage andangular displacement of the actuator. The theoretical angular displacement isvalidated by comparing with both static and dynamic responses obtained fromNewton–Raphson method and Park method, respectively. The theoretical pull-in voltage isin good agreement with the numerical solution within an error of 0.32%, while thetheoretical angular displacement follows the numerical solution within an error of1.50%. As such, the angular displacement and the pull-in angular displacement andvoltage that are expressed in closed forms can be used for the design and analysisof one-DOF torsional actuators that are widely employed for various MEMS.

A Method of Hysteresis Modeling and Traction Control for a Piezoelectric Actuator

The dynamic model and displacement control of piezoelectric actuators, which are commercially available materials for managing extremely small displacements in the range of sub-nanometers, are presented. Piezoceramics have electromechanical characteristics that transduce energy between the electrical and mechanical domains. However, they have hysteresis between the input voltage and output displacement, and this behavior is very demanding and complicated. In this paper, we propose a method of designing the control algorithm, and present the dynamic modeling equations that represent the hysteretic behavior between input voltage and output displacement. For this process, the piezoelectric actuator is treated as a second-order linear dynamic system and system constants are determined by the system identification method. Also, a classical PID controller is designed and used to regulate the output displacement of the actuator. To evaluate the performance of the proposed method, numerical simulation results are presented.

Nonlinear vibration analysis of actively loaded sandwich piezoelectric beams with geometric imperfections

Modal analysis is developed for linear and nonlinear vibrations of deformed sandwich piezoelectric beams with initial imperfections. The beam is subjected to axial displacement and active voltage generated by the top and the bottom piezoelectric layers. The mathematical formulation is developed for the multimodal analysis. Using, the one-mode assumption, simplified relationships accounting for the active voltage, the imposed axial displacement and the amplitudes of imperfections are presented for the load–amplitude, the load–frequency and the nonlinear frequency–amplitude. The stability control of deformed beams is analyzed for various load and voltage levels. For statically deformed beams, a nonlinear frequency–amplitude relationship is presented with respect to positive and negative amplitudes. This formulation accounts for the piezoelectric, the imperfection and the load effects. Numerical tests are investigated for various voltage, load and amplitude levels. The under critical frequency behaviours related to deformed beams, showing the transition from softening to hardening effects, are presented for various levels of active voltage, static response and imperfection amplitudes of simply-supported sandwich piezoelectric beams.

Static and dynamic Young’s moduli of chalk from the North Sea

We present results from a study of dynamic and static Young’s moduli of North Sea chalk based on laboratory tests on both dry and water-saturated chalk. We obtained static moduli by using both strain gauge and linear voltage displacement transducer (LVDT) measurements. We investigated the influence of pore fluid on static and dynamic Young’s moduli and evaluated the two methods for obtaining static Young’s modulus. We obtained good agreement between dynamic and static Young’s moduli from strain gauge measurements on dry chalk, but for water-saturated chalk the dynamic Young’s modulus was larger than the measured static Young’s modulus. This difference may be caused in part by the influence of the difference in frequencies of static and dynamic measurements. Another reason for the observed difference may be a practical experimental problem that causes the measured static Young’s modulus for water-saturated chalk to be lower than the true modulus. When we compared dynamic Young’s modulus for dry chalk with that for water-saturated chalk, the dry modulus was larger than the water-saturated modulus, probably owing to shear weakening of the chalk. Young’s modulus from LVDT measurements does not relate to dynamic Young’s modulus for dry or water-saturated rock because the LVDT is not able to accurately measure the small deformations of the samples during loading at relatively low stresses.

Topology optimized electrothermal polysilicon microgrippers

This paper presents the topology optimized design procedure and fabrication of electrothermal polysilicon microgrippers for nanomanipulation purposes. Performance of the optimized microactuators is compared with a conventional three-beam microactuator design through finite element analysis. The accuracy of the finite element model is verified by comparison of simulated and measured displacement vs. bias voltage curves. A considerable improvement in the mechanical stiffness is indicated by AFM force measurements, being 9 times higher compared to the conventional three-beam actuator.

Computational FEA model of a coupled piezoelectric sensor and plate structure for energy harvesting

This paper presents a mathematical model of a piezo-plate energy-harvesting scheme. An analytical method is used to generate a finite element model of the coupled piezoelectric sensor element using Love-Kirchhoff's plate theory. Constitutive equations for a single layer plate element are formulated. The polarisation of the piezoelectric sensor bounded on the upper plate structure is due to ambient vibration exerted on the structure. Forced vibration of the smart structure will create strain energy within the crystalline structure of the piezoelectric material. The resulting electric field generated by the sensor element was modelled using a linear thickness interpolation function and the meshed plate elements were modelled using four-node rectangular elements with three degrees of freedom for each node. The structural eigenmodes and dynamic response of the coupled piezo-plate system were solved by using modal analysis and Newmark-ß integration methods respectively. The analysis is demonstrated with both dynamic displacement and electric voltage responses to an applied step force. Further modelling of the smart structure is aimed at maximising the power generation capability.

The interlaced/progressive scan method to reduce the switching noise caused by data pulse in a plasma display

In plasma display panels, this paper deals with a new scan driving method which can reduce power consumption and which can improve the reliance of driving circuits. The IPS (interlaced/progressive scan) method as a new driving method was proposed and its efficiency was proven by experiments. This method selects a used scan method from interlaced and progressive scan methods in each subfield, according to the input image pattern. From these experimental results, the IPS driving method used less power consumption than the conventional scan method at the special image pattern as a horizontal alternative ON/OFF line pattern. We obtained the maximum decreasing rate of 18.2% regarding power consumption at a special image pattern. In addition, this method improved circuits’ reliance and lowered the amount of heating loss, because this is the driving waveforms of the address electrodes decreased switching noise, which is the high induced overshoot voltage in scan and sustain electrodes or high impulse displacement current in address electrodes. Therefore, we can expect the lower power consumption and reduction of switching noise, which is the overshoot voltage or impulse displacement current, when the proposed IPS driving method is applied to a driving PDP.

A new backward/forward method for solving radial distribution networks with PV nodes

In this paper, a new backward/forward (b/f) methodology for the analysis of distribution systems with constant power loads is presented. In the proposed method, at each iteration, the loads are considered as constant impedances; in the backward sweep all the network variables (bus voltages and branch currents) are evaluated considering a scaling factor which is determined at the end of the backward phase. Indeed the forward sweep is eliminated and the node voltages calculation does not demand the sequentiality needed in the b/f methodology. The developed method, although deriving conceptually from the b/f methodology, presents only the backward phase in which all the network variables are evaluated considering a scaling factor. Moreover the load simulation as impedances is particularly important when the network shows PV nodes for which the voltage displacement and the reactive power are the unknowns. The condition of 90° displacement between the PV node voltage and the current injected by the apparatus for voltage regulation is not usually satisfied in networks solved by methods using constant current load models. The possibility to solve, at each iteration, a network made up of impedances allows to evaluate the reactance that must be inserted into the PV node in order to set the voltage at the prescribed value. In this way the value of this reactance is updated at each iteration and, at the end of the iterative process, whatever it is the displacement of the PV node voltage, the current circulating into the voltage regulating apparatus will be at 90° from it. In the paper, after a description of the PV nodes models reported in the b/f analysis literature, the new method is presented. The way in which the constant power loads are represented by means of a constant impedance model is also illustrated as well as the method for the evaluation of the unknown reactance to be installed at the PV nodes. The results of the executed applications show the efficiency of the model in terms of precision in the calculation of the reactive power required to sustain the voltage at the PV nodes.

DYNAMICS OF FRUIT GROWTH IN 'CONFERENCE' PEAR AS AFFECTED BY ROOT PRUNING, IRRIGATION AND CLIMATIC CONDITIONS

In 2002, daily fluctuations in trunk diameter and fruit diameter on ‘Conference’ pear trees were measured with linear voltage displacement transducers. On an average sunny day in July, trunk diameter started to decrease around 10 a.m. when air temperature increased. This continued until 8 p.m. when air temperature started to decline. Fruit diameter growth of ‘Conference’ ceased as soon as trunk diameter started to decrease and resumed immediately after trunk diameter started to increase. When fruit growth took place, the rate of diameter increase was fairly constant and was ~ 0.04 mm/h. Root pruning without irrigation significantly affected tree growth but not fruit growth. Fruit size increase was almost linear from early May up to harvest at the beginning of September and averaged 3.9 mm/week. Relationships between fruit growth, climatic condition, soil water availability and cultural practices are discussed

Investigation of the torsion and bending effects on static stability of electrostatic torsional micromirrors

In this paper the electromechanical behavior of a torsional micromirror was investigated using of a static model with considering torsion and bending characteristics of micro-beams. A set of nonlinear equations based on the parallel plate capacitor model was derived to represent the relationships between the applied voltage, torsion angle, and vertical displacement of the torsional micromirror. Step by step linearization method (Newton’s method) was used to calculate the rotation angle and vertical displacement of the micromirror due to the applied voltage. This method is fast and gave acceptable and accurate results which were in good agreement with the experimental data.

Multiple information fusion and quality classification of aluminum alloy resistance spot welding

Resistance spot welding quality real-time monitoring of aluminum alloy is realized by distributed multiple-sensor synchronous collection system and the related data processing software is also developed by using LABVIEW graphical language.The results show that the endo-expulsion in spot welding is related to the notching curve of voltage and electrode displacement signal.Moreover,there is a correlation between the high frequency impulse amplitude and duration of the electrode pressure signal and the expulsion strength index,and three characteristics simultaneously or separately occur according to the expulsion strength index in spot welding. Resistance spot welding quality can be reflected by nine characteristics of high signal-to-noise ratio,and they become the base of on-line quality classification of aluminum alloy spot welding in future.Furthermore,using principal component analysis may implement the information fusion and data compression.The percentage of spot welding quality classification accuracy can reach 98%.

A MEMS-based tracking milli-mirror for high-density optical disk drives

We present a new MEMS-based milli-mirror for precise tracking in high-density optical disk drives (ODDs). The device consists of a torsionally suspended mirror plate, one pair of torsion springs, which support the mirror plate and offer a restoring torque, and two pairs of electrodes attached to the mirror plate and glass substrate. The dimensions of mirror plate and torsion springs were determined so that a 5 V dc bias ±4.5 V ac drive voltage would provide the mirror with ±0.02° rotation to transmit laser beam spot on spinning disk. The MEMS-based milli-mirror was successfully fabricated using MEMS technology. Displacement–voltage linearization scheme was implemented by differential voltage driving. The static and dynamic performances of mirror prototype, such as capacitance versus driving voltage, rotation angle versus driving voltage, and resonant frequency were characterized and compared well with the simulation solutions. The mechanical resonant frequency of the mirror is expected to be high enough to satisfy the requirement of the servo bandwidth of precise tracking-control in high-density blue-laser optical disk drive.

A modeling and analysis of spring-shaped torsion micromirrors for low-voltage applications

An electrostatic torsion micromirror is designed using the optimized spring-shaped torsion beams and U-shaped groove supporters. The main advantages of this design will be a reduction in the pull-in voltage for low-voltage applications and the function as a switch of the instability mode by adjusting the effective bending stiffness of the torsion beam. In this design, a theoretical model is developed to demonstrate the static characteristics of the electrostatic torsion micromirror. The pull-in effect is investigated specifically to predict the pull-in voltage, pull-in angle, and pull-in displacement. These parameters depend significantly on the electrode size and position, position of the groove, and ratio of the bending and torsion effect of the torsion beam. In addition, the effective torsion and bending stiffness model is provided using the energy method with the objectives to optimize the spring-shaped geometries of the torsion beams and to decrease the pull-in voltage below 2 V. The U-shaped groove supporters are applied in the theoretical model to adjust the effective bending stiffness of the torsion beam and to switch the instability mode of the torsion micromirror. The theoretical analysis is consistent with the numerical simulation using MEMCAD and experimental results measured by an optical projection method.