Operation Of Actuator Research Articles

Probability-Based Optimal Control Design for Soft Landing of Short-Stroke Actuators

The impact forces during switching operations of short-stroke actuators may cause bouncing, audible noise, and mechanical wear. The application of soft-landing control strategies to these devices aims at minimizing the impact velocities of their moving components to ultimately improve their lifetime and performance. In this brief, a novel approach for soft-landing trajectory planning, including probability functions, is proposed for optimal control of the actuators. The main contribution of the proposal is that it considers the uncertainty in the contact position, and hence, the obtained trajectories are more robust against system uncertainties. The problem is formulated as an optimal control problem and transformed into a two-point boundary value problem for its numerical resolution. Simulated and experimental tests have been performed using a dynamic model and a commercial short-stroke solenoid valve. The results show a significant improvement in the expected velocities and accelerations at contact with respect to past solutions in which the contact position is assumed to be perfectly known.

Atmospheric-pressure pulsed plasma actuators for flow control: shock wave and vortex characteristics

Pulsed plasma actuators are used for an active flow control application since the 2000s. In this paper, we discuss shock wave and vortex characteristics in pulsed plasma actuators after an introduction of research progress on atmospheric-pressure discharge plasma actuators. First, the shock wave characteristics in surface dielectric barrier discharge (SDBD) actuator operating in diffuse-like and multi-streamer modes are discussed. In the most general case, a shock wave in a diffuse-like SDBD actuator is stronger and faster than in a multi-streamer SDBD actuator. Improved plasma actuators, such as the three-electrode SDBD actuator and the plasma synthetic jet actuator have the enhanced shock wave characteristics. Second, in order to investigate the effects of pulse parameters on the shock wave characteristics in nanosecond-pulse SDBD actuator, a particle image velocimetry system is used to capture the formation of starting vortexes at different pulse rise times, pulse durations, and pulse repetition frequencies (PRFs). It is shown that the velocity of a starting vortex significantly increases when the pulse rise time decreases from 400 ns to 50 ns due to a more significant hydrodynamic effect generated during a shorter rise time. This phenomenon is confirmed by calculating a reduced electric field E/N at a short rise time, which turns out to be higher at a shorter rise time than that at a relatively longer rise time. It is also shown that the velocity of a starting vortex increases and its active area enlarges when the PRF increases.

Damping of the longitudinal streak in the boundary layer by ‘plasma panel’ actuator

The group of microdischarges in surface DBD can be used as a virtual roughness element. Localization of the discharge along the electrode span can be performed on the ‘plasma panel’ principle by sectioning the buried electrode and individually controlling sections potential. The paper describes the study of the details of such actuator operation. Data presented include the flowfield induced by discharge and the analysis of the controllability of the created disturbances in a subsonic boundary layer. In the final part of the paper, the control of the low-velocity streak, an object widely present in transitionary and turbulent flows, by an adaptive plasma actuator, is demonstrated.

Experimental results from a Thomson‐coil actuator for a vacuum interrupter in an HVDC breaker

Recent developments in high-voltage direct current transmission technology and the plans for multi-terminals motivate research efforts on the fast DC breaker. A novel concept to interrupt current up to several kiloamperes within a few milliseconds is presently under development, using a vacuum interrupter together with power electronics to create an artificial zero-crossing in the current through the switch. To achieve this objective, one critical component in the concept is an ultra-fast linear mechanical actuator. A prototype has been developed based on a Thomson coil. The experimental results are presented and show how a contact gap in a vacuum interrupter was effectively created in a controlled manner. Current of several kiloamperes was successfully interrupted within 3 ms, thanks to the high-speed operation of the linear actuator.

Study of the effect of adiabatic heating on the operation of the electrodynamic actuator

Electrodynamic actuators are used in hybrid switching systems where a very quick contact separation as well as operation repeatability and long-term reliability are required. The article presents selected results of thermal studies in the electrodynamic drive system. Study was carried out on the ba sis of the 3D electromagneto-thermal model implemented in the Ansys_Maxwell environment. The present model allows to determine the critical parameters related to the heating and to guarantee the correct and repeatable operation of the actuator.

Mechanics of a curved electrode actuator operating in viscous dielectric media: simulation and experiment

Curved electrode electrostatic actuators have been shown to have the potential to manipulate microparticles at high speeds in viscous dielectric media. However, there are no multiphysics models that fully describe the mechanics of these actuators in viscous dielectric media. This work is the first step in the direction of describing the actuator mechanics through Finite Element Method (FEM) simulations and validate it with the experiments. Simulations are performed using the commercial software Coventor MEMS+® and the results are found to be in good agreement with experiments. Two observations are reported in this study. One, for a given media and low actuator displacements, the cutoff frequency of the actuator is independent of the actuation voltage and/or actuator displacement. Two, an actuator immersed in a high viscous media will have higher squeeze film damping and a lower cutoff frequency. Through a simple lumped-parameter model of the actuator, we report that the viscous damping effect by the substrate on the actuator submerged in methanol or water media becomes significant for actuation frequencies >100 Hz.

Ring-shaped fluorescence of mineral oil on the front edge of the choke coil

Hydraulic drive is a quite complicated technical system widely used in various industries: transport, agriculture, aviation, aerospace, robotics etc. During operation of the hydraulic actuators there are various modes and physical processes that occur in the working fluid to its devices. It is known that various processes like cavitation, degassing, erosion are observed in hydraulic drive devices, which are deeply studied and fully described in the literature. As follows from the analysis of the literature, the emergence of such a process as the light emission of a liquid in the form of flashes of light, the nature of which is ultrasound, is possible. The paper presents the material on the study of a rare and little-known phenomenon in the devices of hydraulic drives - the glow of the working fluid without ultrasound in it. To fill a certain gap in the study of the nature of the fluorescence of the working fluid, in particular, the fluorescence of mineral oil, the authors of this paper conducted an experimental study of cavitation processes in the transparent model of the hydraulic device - in the diaphragm choke coil.

3D magnetostrictive Preisach model for the analysis of magneto-electric composites

In the present contribution, we compare numerical simulations of magneto-electric composites with experimental measurements. The coupling between electric polarization and magnetization of such materials can improve the operation of sensors and actuators and can enable new technical devices. These composites consist of a ferroelectric and a magnetostrictive phase and generate the ME coupling as a strain-induced product property. However, the responses of the individual phases are highly nonlinear. It is important to predict the behaviors of both phases in an appropriate manner to ensure a realistic prediction of the magneto-electric coefficient. Therefore, we simulate the nonlinear ferroelectric hysteresis curves based on the ferroelectric and ferroelastic switching behavior of the spontaneous polarization directions on the submicroscopic level. Therefore, a switching criterion considering the change in the free energy is evaluated. For the simulation of the magnetostrictive behavior, we derive in this contribution a three-dimensional Preisach model. For this, the classical scalar Preisach model acts on a rotational time-dependent magnetization vector. After a homogenization approach within the finite-element ( $$\hbox {FE}^2$$ )-method, the effective macroscopic hysteresis curves are obtained. Furthermore, the magneto-electric coefficient is obtained from the homogenization and compared with experimental measurements in terms of magnitude and nonlinear behavior.

Development of procedures for determining the parameters of an aircraft servo actuator

Main trends in the use of electro-hydraulic actuators and requirements to parameters were discussed. Necessity of using automatic methods for testing an electro-hydraulic actuator together with the standard hardware of the electronic control unit was substantiated. The procedures for testing the control loop of an electro-hydraulic actuator set forth in this study make it possible to eliminate effects of mutual influence of dynamic and static characteristics of the actuator and hardware of the electronic control unit. Procedures for automatic identification of the actuator model and procedures for automatic determination of main parameters and characteristics of the actuator such as zero shift, dead space, amplitude-frequency, phase-frequency and speed characteristics have been proposed. When introducing the proposed procedures, the problem of processing high-speed characteristics of the actuator having high noisiness associated with the pulse nature of the derivative of the discrete signal of the actuator position (12 bits) was solved. In order to avoid introduction of errors in the waveform, in addition to standard digital filtering methods, it was proposed to approximate the noisy actuator characteristic by means of the Bezier curve. A procedure was proposed to record hysteresis of the speed characteristic by means of a cycle of continuous change of speed of movement of the output link of the actuator during the working stroke. The method for automatic identification of a simplified actuator model can significantly reduce labor costs in processing of experimental data. The parameters of the actuator model obtained for various deviations in parameters and various actuator operating conditions (external factors) can improve quality of synthesis of control algorithms

A Charge Controller for Synchronous Linear Operation of Multiple Piezoelectric Actuators

The charge controller can greatly improve the hysteresis of the piezoceramic without the sensor. It is widely used in open-loop controlled nano-positioning systems. However, conventional charge controllers are not suitable for synchronous high linear operation of multiple piezoelectric actuators. This paper proposes a novel charge control scheme which can be used for synchronous high linear operation of multiple piezoelectric actuators. The control scheme combines similar control and traditional charge control. We verify the feasibility of this control scheme through experiments. The trajectory deviation between the two piezoelectric actuators reaches 0.79% of the travel range, while their respective trajectory errors do not exceed 1.2%. Because the controller in this paper has a simpler grounding configuration, it can also replace the traditional charge controllers for high linearity operation. The experimental results show that the charge controller achieves 0.65% positioning error of the piezoelectric actuator with grounding configuration. In addition, a T-type resistor network has also been introduced into the charge controller, which enables low-frequency linear operation of piezoelectric actuators with small capacitance.

Similarity-based Feedback Control with Reduced Capacitive Load for Linear Operation of Piezoelectric Actuators

This paper presents a hysteresis compensating control scheme that uses two piezoelectric transducers with similar hysteretic behavior. The transducers are supplied with the same voltage and the measured displacement of one of them is used to operate the other one in “open-loop”, thereby reducing the hysteresis for a triangular reference signal with a frequency of 1 Hz from 17.5 % to 1.5 %. In order to avoid a significant increase of the capacitive load of the piezo amplifier, two transducers of the same material but different sizes are used, which reduces the required current by 47 % while maintaining the reduced hysteresis of the positioning system.

Finite element modeling and parametric analysis of a dielectric elastomer thin-walled cylindrical actuator

Due to their high energy density, dielectric elastomers have been widely studied over the last decades, in particular, for applications requiring electromechanical actuators. They are commonly designed using thin-walled elastomeric structures, with particularly interesting dielectric properties, that are covered by flexible electrodes in their upper and lower surfaces. Unlike other potential electromechanical materials, such as piezoelectric ceramics, dielectric elastomers may undergo high deformation levels and, thus, present themselves as interesting alternatives for applications that require greater deformations and/or displacements. Nevertheless, in order to profit from this advantage, the design of dielectric elastomer actuators requires predictive models that properly account for both structural and material behavior under high deformations and also electromechanical coupling. The main objective of this work is to present an assessment of existing nonlinear elastic theories well suited to dielectric elastomers that allow to propose a finite element procedure capable of predicting the electromechanical behavior of a plate-type structure. Finite element results are compared to analytical and experimental ones. Then, the procedure is applied to carry out a parametric analysis of a dielectric elastomer cylindrical actuator. The obtained results indicate that the proposed finite element procedure is capable of well representing the actuator operation. It is shown that important deformations and displacements may be obtained with the proposed dielectric elastomer cylindrical actuator, even when subjected to opposing forces, and its performance may be tuned by changing its geometrical properties.

Shock Waves in an Electrochemical Microactuator

The explosive mode of operation of an electrochemical actuator is studied. In this mode of operation, we observe explosion of microbubbles containing the oxygen–hydrogen gas mixture that forms in the working chamber of the actuator during electrochemical water splitting by high-frequency pulses of alternating polarity. We demonstrate that shock wave emission occurs as a result of implosion of the void formed due to the microbubble explosion, rather than the explosion of the microbubble itself. Using the experimentally measured variation in the bubble wall velocity with the distance from the explosion center, we estimate the pressure amplitude at the shock front. The dynamic of microbubble collapse is established using time-resolved photography.

Structure of a Graphene-Modified Electroactive Polymer for Membranes of Biomimetic Systems: Simulation and Experiment

A model is proposed that describes the structure of water filled Nafion-graphene composite forming the body of an electroactive polymer membrane for actuators of biomimetic systems able to work in air and a liquid medium. The model predicts the growth of the ionic conductivity with increasing concentration of a graphene modifier, which is due to that the size of a part of clusters of the Nafion framework containing hydrophobic graphene flakes enlarges together with the pore size. Then the optimal concentration of the graphene modifier is reached, which provides the maximum ionic conductivity and actuation ability of the membrane as well as its elastic properties. The possibility of introducing into Nafion the modifier amount needed to improve the actuator operation is experimentally tested.

An Extended Kalman Filter as an Observer in a Control Structure for Health Monitoring of a Metal–Polymer Hybrid Soft Actuator

This paper presents an innovative nonlinear model of a self-sensing soft actuator and a switching extended Kalman filter, which is used as an observer for health monitoring such as a virtual sensor. Hardware-in-the-loop simulations and measurements justify the observation strategy. An adaptive position control structure based on the discrete wavelet packets transform method is proposed. Stimulus-responsive polymers are relevant for the realization of smart systems (capable of both sensing and actuating) in the context of soft actuators, for example, in bioinspired robotics, orthotic, and prosthetic technology. A real-time implementation of health monitoring techniques is important to guarantee a gentle, fault-free operation of the soft actuator in the presence of loads. The presented case shows a microrobotic application and measured results show the effectiveness of the developed observer regarding the soft actuator temperature to guarantee its longevity. The latter is necessary for normal operation without a test bench, because the states cannot be measured, but they need to be known for the implementation of the proposed health monitoring algorithms.

A multilayered-cylindrical piezoelectric shear actuator operating in shear (d15) mode

In this work, a multilayered-cylindrical piezoelectric shear actuator (MCPSA) operating in the d15 shear mode was presented for precision actuation under a large mechanical load. The actuator was made of Pb(Zr,Ti)O3 (PZT-51) piezoelectric ceramic rings, which were concentrically assembled together in electrically parallel connection with alternately positive and negative polarizations along the axial direction. Experimental results show that the acquired displacement amplitude at the center of the actuator along the axial direction is around 6.5 μm under the 1 Hz applied voltage of 400 Vpp/mm, and it stayed stably under a mechanical load up to 18 N, which is 7 times larger than that of the previously reported d15 shear actuator. The proposed actuator also shows good displacement linearity with a high resolution of 0.1 μm in responding to a step voltage, indicating its great potential for precision actuation under a large mechanical load.

Description of operation of fast-response solenoid actuator in diesel fuel system model

The performance of the fast-response solenoid actuator (FRSA) of engine fuel systems is characterized by the response time of less than 0.1 ms and the necessity to take into consideration the non-stationary peculiarities of mechanical, hydraulic, electrical and magnetic processes. Simple models for magnetization in static and dynamic hysteresis are used for this purpose. The experimental study of the FRSA performance within the electro-hydraulic injector of the Common Rail demonstrated an agreement between the computational and experimental results. The computation of the processes is not only a tool for analysis, but also a tool for design and optimization of the solenoid actuator of new engine fuels systems.

Study on the Hazard Limitation of Hybrid Circuit Breaker Actuator Operation

The paper deals with a key issue, how to limit the hazard and assure reliability, safety and repeatability of operation of selected critical devices protecting electrical power systems. The main research is focused on the incorrect operation of hybrid switches caused by random disturbances of the thyristor gate signals in the electrodynamic drive coil power supply circuit. Firstly, a pilot experiment on the operation of hybrid circuit breaker actuators under random disturbance conditions was carried out and the results are presented. Next, an in-depth operation analysis, based on experimental and simulation research, according to setting conditions of the circuit breaker actuator parameters such as capacitance, voltage and switching time was performed. A simulation study with the use of a field–circumferential model in the Ansys Maxwell program of electrodynamic propulsion of rectilinear motion, which enables energy transfer from the capacitor bank to the actuator coil power supply at selected time intervals, was executed. The study analysed the impact of the discontinuity of energy transfer on the dynamic properties of the actuator and some recommendations for designers and users on how to limit this hazard are formulated.

Метод діагностування електромагнітного привода вакуумного вимикача на основі вебер-амперних характеристик

The method of diagnosing the electromagnetic actuator of a vacuum circuit breaker is proposed. It was investigated that there is a steady tendency to increase the number of electrical supply violations of responsible energy objects, which leads to negative consequences. Most electric equipment in power systems needs repair or replacement. Outdated oil switches are massively replaced by vacuum. Vacuum switches have several advantages over other types of switching equipment. Most vacuum switches are equipped with electromagnetic actuators. Improper operation of the electromagnetic actuator leads to the failure of the vacuum circuit breaker. The proposed method allows determining the technical state of the electromagnetic actuator of a vacuum circuit breaker. The essence of the method is to measure the reference curve of a magnetic characteristic after the introduction of a new switch into operation or after its overhaul and comparison of this curve with the following measured magnetic characteristics in the course of its further operation. During the operation, the shape of the weber-ampere characteristics of the windings of the electromagnetic actuator of the vacuum circuit-breaker changes. Deviation control from the reference characteristic allows us to estimate the current state of the electromagnet and its degree of wear. An experiment was carried out to simulate the failure of the vacuum circuit breaker, as a result of which the proposed method can determine the deflection factor of weber-ampere characteristics, which evaluates the technical state of the electromagnet and the actuator of the vacuum circuit breaker as a whole. The results of measurement of curves of current, voltage and calculated weber-ampere characteristics for windings of switching on / off switch electromagnet are given. The deflection factors for switching on / off windings are determined when the vacuum circuit breaker malfunctions.

Hydraulic Drive of a Shipping Lock Gate with Automated Frequency-Throttle Control System

This project developed and built a hydraulic actuator prototype with an automated control system for moving the lifting and lowering gates of a shipping lock. In the course of the design engineering, a hydraulic actuator was experimentally developed. Trial operation of a hydraulic actuator was conducted on Lock No. 26 of the Balakovo RGSiS. This design of a hydraulic actuator is recommended to be used in upgrading and designing locks of hydraulic engineering constructions.