Characteristics Of Actuator Research Articles

Evolution of a single sessile droplet under the influence of the dielectric barrier discharge plasma actuator

Ice accretion on airplane surfaces has been widely recognized as a significant safety threat, and corresponding investigations of anti-/de-icing technologies have experienced tremendous growth during the last two decades. Dielectric barrier discharge plasma actuators involve different characteristics, such as thermal, acoustic, and flow characteristics, which are well suited for reducing and preventing ice accretion on wing surfaces effectively and safely. However, the correlation between the droplet, as the core of ice formation, and the plasma actuator is still not very clear. In order to understand the anti-/de-icing mechanism of the plasma actuator further, the evolution of a single sessile droplet under the influence of a symmetrical plasma actuator is studied. Interestingly, the oscillation of the droplet is first observed on the initiation of the plasma actuator, which is quite different from the droplet variation under traditional heating or cooling. Then, the flow field inside the droplet under the effect of the induced flow field of the plasma actuator is first uncovered by using the particle image velocimetry system. Subsequently, the evolution process of droplet deformation, deformed droplet moving downstream, deformed droplet moving downstream and evaporating, and water film moving downstream and evaporating is revealed. In addition, the underlying mechanism of the evolution process of the droplet is discussed based on the different characteristics of the plasma actuator. This study provides an in-depth understanding of the correlation between the droplet and the plasma actuation and lay a foundation for proposing the optimized strategy of anti-/de-icing using plasma actuators.

Plasma kernel model and energy transformation characteristic of plasma synthetic jet actuator

This article conducted a theoretical, experimental, and numerical investigation to clarify the plasma kernel model and energy transformation characteristics of the plasma synthetic jet actuator (PSJA). Plasma kernel and blast wave theory were used to describe the formation and evolution of the arc-discharge energy deposition process and build a plasma kernel model. Schlieren experiment visualized the formation and evolution of the synthetic jet flow and used it as a validation of the numerical simulation. Five plasma synthetic jet actuators with different cavity volumes (128–512 mm3) and different discharge energy (2.8–11.3 mJ) were modeled numerically to investigate the energy transformation characteristic of PSJA. Results showed that plasma kernel radius and formation time could be theoretically predicted with specific deposition energy and correspond well with simulation results. The peak pressure and temperature rise in the cavity can also be calculated. Moreover, the proportion of kinetic energy increases linearly with non-dimensional deposition energy, while potential energy has a reverse tendency with non-dimensional cavity volume and deposition energy.

Study of the influence of current pulse parameters on kinematic and energy characteristics of a plasma actuator based on a moving electric arc

In this work, a parametric study of the flow induced during the movement of an arc channel in a transverse constant magnetic field in initially still air is carried out. The analysis of the flow structure, integral energy and kinematic characteristics of the arc acceleration process is carried out. Instantaneous velocity fields in the induced flow were experimentally obtained for the range of discharge current amplitudes from 8 to 160 A and pulse durations from 40 to 380 μs. A parametric study of the flow structure in the wake behind the arc is carried out by the method of two-dimensional numerical simulation in the MHD approximation. In the particular case of a single-mode current pulse, the shape of the current pulse is optimized to maximize the gas momentum in the near-wall region. It is shown that similar conditions for the balance of local acceleration, convective acceleration and viscous forces are observed for the problem of flow past an arc and a cylinder for regimes with a conditionally steady vortex shedding in the wake. In this case, the coincidence of the vortex shedding frequency occurs when the characteristic scale of the streamlined body is chosen equal to half the height of the thermal cavity.

Modeling and mu-synthesis control of a flexible rotor stabilized by active magnetic bearings including current free control

Designing a controller for a magnetically stabilized rotor that experiences non negligible gyroscopic moments requires careful attention on the rotordynamic behavior, the design of the position and current free control as well as the actuator and sensor characteristics. Most of the controller design procedures for magnetic bearings separate the synthesis of the current free controller and the position controller using different methods. This article connects the synthesis of the current free controller and the position controller in the μ-framework. Therefore, the modeling of the rotor, the position controller design and the design of the current free control of a flexible rotor stabilized by active magnetic bearings is described. The rotor is modeled by using the finite element method. Afterwards, the flexible system is reduced to get an appropriate model size for the control design. For the optimization of the controller parameters the μ-synthesis method is applied. However, compared to the general μ-synthesis method in this article an a priori fixed control structure is utilized. This control structure splits up the tilting subsystem to a control path for the nutation mode and one for the precession mode. Thus, the proposed controller has the advantage of a low system order and that the parameter variant nature of the plant is already considered in the control structure. Additionally, the synthesis of the current free controller is added to the μ-framework. Hence, the current free controller is optimized for a plant with defined uncertainties using necessary constraints of the closed loop systems. Finally, the stabilization of the system using the proposed control method is experimentally validated on a turbomolecular pump with a magnetically levitated rotor.

A long-stroke planar linear actuator equipped with magnetic guide

This paper introduces the design, fabrication and characterization of a micro electromagnetic linear actuator integrated with magnetic guide. The actuator consists of a slider, a stator and a magnetic guide. A magnetic guide is used to replace the mechanical rail of conventional linear actuator to ensure the linear motion and to avoid friction. The purpose of this paper is to study the influence of magnetic guide on the dynamic characteristics of electromagnetic linear actuator and measuring techniques for micro-actuators. To test the resistance to motion and output thrust force of the actuator, a cantilever type force sensor is proposed, which can measure the small force in ∼mN order, and the measurement error is less than 3%. Using this sensor, the output thrust measured is higher than 10 mN when 1 A current is applied, and the friction force of the actuator measured is about 7.73 mN. Two-phase square wave and sine wave current are used to drive the actuator, the minimum driving current and frequency of the actuator are less than 0.1 A and 1 Hz respectively. The actuator attains a maximum stable moving speed of 0.15 m s−1 with the input signal frequency of below 250 Hz. In addition, the anti-interference capability of the actuator is evaluated through simulations and experiments. These results show that the actuator can bear an interference 45 times its own gravity in the directions that are perpendicular to the moving freedom, and can adjust the direction of motion automatically when the rotation angle in three orthogonal directions is less than 6°.

HIL simulation of high-speed train active stability employing active inertial actuators

ABSTRACT To enhance the lateral stability of a certain type of high-speed train under bogie’s active control, characteristics of inertial actuators that generate control force in the active control system are studied, the control delay of the whole Hardware-in-the-Loop (HIL) system is measured, and multi-objective optimisation for feedback parameters with or without the control delay is achieved in this study. A linear model of bogie lateral dynamics, with two inertial actuators, acting on the front and rear end beams, is established for the optimisation. Correspondingly, a nonlinear vehicle model is established in the Simpack platform for both mathematical simulation and HIL simulation to verify the control effects. As the force source of active control, dynamic characteristics of the inertial actuator with different control strategies are examined. Multi-objective optimal control is carried out on the linear active bogie models with and without the delay measured in the experiment to improve the bogie hunting stability. The control method is then evaluated in a nonlinear vehicle model and HIL simulation. Simulation results show that the lateral dynamic performance of the high-speed train can be effectively improved with the active stability system even with a large time delay.

Lagrangian analysis of the flow induced by a dielectric barrier discharge plasma actuator array under burst mode actuation

The dynamic properties of the flow induced by a dielectric barrier discharge (DBD) plasma actuator array are investigated from the Lagrangian perspective. First, numerical simulations based on a body force model are performed to obtain the flow field induced by unsteady plasma actuation in the burst mode. The numerical simulations capture the flow characteristics of plasma actuation well. Subsequently, the ridges of the finite-time Lyapunov exponent field are employed to identify the Lagrangian coherent structures (LCSs). Both the attracting and repelling LCSs organize the plasma-induced flow’s dynamic behaviors. The attracting LCSs visualize the plasma-induced vortices. The vortex formation, development, and merging processes in the unsteady plasma actuation are resolved well by the LCSs. The material transport in the plasma-induced flow is analyzed by tracing the fluid particle motions. Then, the influences of the actuation parameters, duty cycle, and burst frequency on the flow structures are explored via the attracting LCSs. The presented results enhance the understanding of plasma actuation flow physics and promote the optimal use of DBD plasma actuator arrays.

Effects of environmental temperature on the spectral characteristics of RGA plasma-assisted combustion actuator for aero-engines

Using rotating gliding arc (RGA) discharge, a plasma-assisted combustion actuator was designed and used in aero-engines. To study the spectral characteristics of the actuator at the changed environmental temperature, an experimental system for the spectral characteristics of the RGA plasma-assisted combustion actuator was established. The optical emission spectroscopy (OES) of the actuator discharge was measured with an emission spectrometer. It was discovered to primarily include the emission spectroscopy of N2∗ (C3Πu→ B3Πg), N+, N, and O atom. As the environmental temperature increased, OES of N2∗ (C3Πu→ B3Πg) has a fluctuating change rising of first at less than 313K, then falling between 313 K and 353 K, and rising again between 353 K and 373 K. Simultaneously, the emission intensity of N+, N, and O atoms decreased. In addition, the vibrational temperature was calculated by the second positive system (SPS) N2∗ (C3Πu→ B3Πg) and Boltzmann plots. The vibrational temperature decreased by 363–492 K with the increase in environmental temperature. These results are valuable for understanding RGA’s application in aero-engines.

BNT‐based relaxor/ferroelectric systems: Improved field‐induced strain property in the layered composite ceramics

AbstractBoth high strain and low driving electric‐field are important characteristics of the piezoelectric actuators for industrial applications, but they are difficult to achieve together in a single material system. In this work, the layered and inlay‐onlay structures of relaxor/ferroelectric composites were prepared by selecting relaxor phase (0.94Bi0.5(Na0.82K0.18)0.5TiO3‐0.06NaNbO3, BNKT‐6NN) and ferroelectric phase (0.9Bi0.5Na0.5TiO3‐0.1Bi0.2Sr0.7TiO3, BNT‐10BST) with the volume ratio of 1:1. By comparing the field‐induced strains under same electric‐field, the S33 of the BNKT‐6NN/BNT‐10BST layered composites (0.17%) was greater than that of the inlay‐onlay composites (0.08%) and exhibited excellent temperature stability. The superiority in field‐induced strain for the layered composite ceramic was originated from the inhomogeneous distribution of internal electric‐field between relaxor and ferroelectric phase and thereby could modulate the polar nanoregions to ferroelectric phase transition. In addition, the restricted phase boundary between relaxor and ferroelectric phase enhanced the potential barrier energy (Ea = 1.47 eV) and hindered the jump of defective ions (mainly oxygen vacancies) of the BNKT‐6NN/BNT‐10BST layered composites. The outstanding electrical properties of layered composite ceramics provide a new idea for further improving field‐induced strain performance.

Study on the actuation characteristics of a graphene oxide‐modified biological gel electroactive actuator

AbstractTo overcome the poor conductivity of electrode film in bio‐gel electroactive actuator, graphene was introduced into its structure to prepare a kind of bio‐gel electroactive actuator based on chitosan, and its actuation characteristics were analyzed. First of all, the output characteristics of the electroactive actuator prepared with the addition of graphene oxide （GO）were tested to obtain the variation patterns of bending force and displacement. Second, electrochemical and microscopic tests were carried out and the water retention rate was analyzed to explore the internal reasons for the improvement of output characteristics. Third, how the mass fraction of GO influences the polymer electroactive actuator's bending force performance was comprehensively analyzed. The results show that adding GO significantly improved the electroactive actuator's performance. Adding graphene oxide into the polymer actuator was proved to be an effective strategy to improve the actuator's actuation properties.

Analytical Modeling of a Soft Pneu-Net Actuator Subjected to Planar Tip Contact

Soft actuators are compliant structures that are generally made of elastomers and generates large deformation. The behavior of these structures cannot be estimated accurately using infinitesimal strain theories. The objective of soft robotics applications is the controlled large deformation of these structures. In this article, we propose an analytical model for a pneu-net soft actuator. The model is based on the Euler–Bernoulli finite strain hyperelastic thin cantilever beam theory. The deformation of the air chambers is modeled using finite strain membrane theory. The analytical model is developed for two different states of the actuator: 1) free space; and 2) when the actuator was subjected to tip contact. The proposed theoretical model predicts the deformation and force characteristics of the actuator for the grasping state. The theoretical formulation of the developed model is different from previously developed infinitesimal strain models for the actuator, as it considers the axial stretch and forces applied to the actuator. In addition, it can be theoretically implemented on similar structured actuators for various applications. The theoretically calculated deformation and force characteristics of different actuators are compared with the finite element (FE) model and experimental characteristics. The results suggest that the proposed model can predict the actuator deformation and force characteristics as accurately as the FE model, but the computation time of the proposed model is less than 1% that of the FE model. The proposed model is further implemented on a three-finger gripper to predict the air pressure required for a stable grasp of different objects and is validated experimentally.

Asymmetric Bouc-Wen hysteresis modeling for MFC actuator via hybrid APSO-TRR identification algorithm

Macro fiber composite (MFC) is widely used in active vibration and deformation control. The intrinsic asymmetric hysteresis nonlinearity of MFC affects the control accuracy. In this paper, a modified Bouc-Wen (MBW) model based on the sigmoid function is proposed to describe the asymmetric hysteresis characteristics of MFC, and its parameters are identified by a hybrid algorithm composed of the trust-region reflection method and asynchronous particle swarm optimization. The accuracy of the proposed MBW model is verified though hysteresis tests of MFC under different drive frequencies. The results show that the MBW model can accurately model the asymmetrical hysteresis of the MFC actuator, the modeling error is reduced by 72% compared with the classic Bouc-Wen model. The proposed hybrid parameter identification method saves 95% of the time compared with the particle swarm optimization and asynchronous particle swarm optimization algorithms. • A modified Bouc-Wen (MBW) model is proposed to describe the asymmetric hysteresis characteristics of MFC actuators. • A hybrid algorithm (APSO - TRR) with global and local search ability is proposed for parameter identification. • Performance of proposed APSO - TRR is compared with classical PSO、APSO and TRR algorithms. • Accuracy of proposed asymmetric Bou–Wen model is compared with classical Bou–Wen model.

A constraint-flow based method of synthesizing XYθ compliant parallel mechanisms with decoupled motion and actuation characteristics

It is an open challenge to synthesize XYθ compliant parallel mechanisms (CPMs) with decoupled motion and actuation characteristics for increasing applications from semiconductor manufacture to bio-nanotechnology. The key issue in the synthesis is to obtain the permitted constraints of the constituent compliant modules. In this paper, a constraint-flow based method is proposed to address this need, and up to 6859 constraint combinations are derived for the compliant modules, leading to a great number of possible synthesis schemes. Two case studies of schemes are presented to demonstrate the proposed synthesis method. One of the designs is analytically modelled, with less than 6.45% difference compared with the FEA results. A prototype of the design is also fabricated and experimentally tested. The analytical, FEA and/or experimental results show that the couplings are less than 3.9%, the translation resolution is 5 nm, and the rotation resolution is 50 nrad. The introduced constraint flow concept is not limited to the application of synthesizing decoupled XYθ CPMs, but also is an alternative and effective method in synthesizing other types of CPMs.

Rapid, Energy-saving Bioinspired Soft Switching Valve Embedded in Snapping Membrane Actuator

In nature, organisms widely use the interaction of muscle contraction and biological pipelines to form an efficient fluid control mechanism. Herein, a pneumatically powered, Bioinspired Soft Switching valve (BSS valve) with short response time and low-energy consumption is described. The BSS valve is composed of flexible walls, a flexible tube and symmetrically arranged Snapping Membrane actuator (SM actuator). It functions based on tube deformation throttling caused by instability of SM actuator membrane. To realize rapid preparation of customized BSS valve, the modular manufacturing method suitable for different materials and structures based on 3D printing and mold forming was developed. Using the membrane flip rate as indicators, the displacement transient response characteristics of three structures actuators were studied, The results proved that spherical and spherical cap membrane SM actuator achieved rapid displacement response under the low critical pressure threshold. Furthermore, with critical buckling pressure and capacity utilization efficiency as indicators, we analyzed the characteristics of SM actuators with different radius and wall thickness to obtain reasonable structural parameters configuration of SM actuators. The influence of radius and thickness on SM actuator is revealed, and theoretical model formulas were formed. Two different configurations are presented. (1) Customized BSS valve structures can achieve sequential motion of flexible gripper. (2) BSS valve embedded in soft pump. The performance tests confirmed it has significant advantages in energy consumption, specific pressure, specific flow, high-frequency cycle load life, and valve can be integrated into the soft pump fluid system as a throttling unit, and provides an idea for fluid drive control integration.

Jelly-Z: Twisted and coiled polymer muscle actuated jellyfish robot for environmental monitoring

Silent underwater actuation and object detection are desired for certain applications in environmental monitoring. However, several challenges need to be faced when addressing simultaneously the issues of actuation and object detection using vision system. This paper presents a swimming underwater soft robot inspired by the moon jellyfish (Aurelia aurita) species and other similar robots; however, this robot uniquely utilizes novel artificial muscles and incorporates camera for visual information processing. The actuation characteristics of the novel artificial muscles in water are presented which can be used for any other applications. The bio-inspired robot, Jelly-Z, has the following characteristics: (1) The integration of three 60 mm-long twisted, and coiled polymer fishing line (TCPFL) muscles in a silicone bell to achieve contraction and expansion motions for swimming; (2) A Jevois camera is mounted on Jelly-Z to perform object detection while swimming using a pre-trained neural network; (3) Jelly-Z weighs a total of 215 g with all its components and is capable of swimming 360 mm in 63 seconds. The present work shows, for the first time, the integration of camera detection and TCPFL actuators in an underwater soft jellyfish robot, and the associated performance characteristics. This kind of robot can be a good platform for monitoring of aquatic environment either for detection of objects by estimating the percentage of similarity to pre-trained network or by mounting sensors to monitor water quality when fully developed.

Технологические аспекты повышения эксплуатационных характеристик силовых гироскопов космических аппаратов систем дистанционного зондирования Земли

The article considers the problems of controlling the preliminary axial load on the ball-bearing support of a power gyroscope rotor by the frequency method. The study of the effect of the power gyroscope rotor rotation speed on the natural oscillation frequency under varying environmental conditions was performed on a special installation that combines a thermal, vacuum chambers and vibration installation using statistical methods for identifying and optimizing complex systems. The relationship between the natural frequency of the rotor forced oscillations and the speed of rotation, ambient temperature and pressure is identified in the form of a mathematical model, with the effect of each parameter under study being of nonlinear character. It is found that the effect of the rotation speed on the natural frequency of power gyroscope rotor oscillations changes significantly at different values of ambient temperature and pressure, and the value of the natural frequency is maximum at the static position of the rotor. The results of the study allow performing natural frequency technological control at different stages of instrument assembling under controlled conditions and can be used in the development of methods for controlling the frequency characteristics of inertial actuators of orientation and stabilization systems

Implicit Implementation of Nonsmooth Controllers to Nonsmooth Actuators

This article presents an approach to implement a sliding-mode position controller to a plant equipped with a nonsmooth actuator. The actuator is modeled as a set-valued function from the control input and the velocity to the actuator force, which is motivated by quasi-static characteristics of hydraulic actuators shown in a previous study. The implementation of the sliding-mode controller is performed with the implicit discretization of the nominal plant model and the controller, which copes with the difficulties caused by the set-valuedness, such as numerical chattering. Stability analyses both in the continuous-time and discrete-time domains are presented. Simulation results illustrate the theoretical findings.

A novel adaptive backstepping sliding mode control for a lightweight autonomous underwater vehicle with input saturation

Accurate depth and heading control play an essential role for autonomous underwater vehicles (AUVs) in near-seabed exploration and ocean surveys. This paper proposed a novel adaptive backstepping sliding mode control (ABSMC) algorithm for a lightweight autonomous underwater helicopter (AUH) subject to highly coupled nonlinearities, unknown system parameters, disturbances uncertainties, and input saturation. This algorithm adopted a conditional adaptation algorithm to govern adaptation so that gains only adapt when necessary to improve stability. Different reaching laws were selected for heading and depth control to reduce system chattering. For thruster saturation, we proposed an anti-windup compensator for auxiliary dynamic compensation based on system states; it can make the controller output change smoothly in the event of input saturation to better meet the response characteristics of the actual physical actuator. The mathematical proofs of the proposed algorithms are presented. Simulation results are presented to illustrate the effectiveness of the proposed control method. Moreover, extensive experimental results show that the proposed algorithm has better control performance than PID and sliding mode controllers and demonstrate its adaptive capability to system state changes.

Electrical and aerodynamic characteristics of sliding discharge based on a microsecond pulsed plasma supply

Plasma flow control technology has broad prospects for application. Compared with conventional dielectric barrier discharge plasma actuators (DBD-PA), the sliding discharge plasma actuator (SD-PA) has the advantages of a large discharge area and a deflectable induced jet. To achieve the basic performance requirements of light weight, low cost, and high reliability required for UAV (Unmanned Aerial Vehicle) plasma flight experiments, this work designed a microsecond pulse plasma supply that can be used for sliding discharge plasma actuators. In this study, the topology of the primary circuit of the microsecond pulse supply is determined, the waveform of the output terminal of the microsecond pulse plasma supply is detected using the Simulink simulation platform, and the design of the actuation voltage, the pulse frequency modulation function and the construction of the hardware circuit are achieved. Using electrical diagnosis and flow field analysis, the actuation characteristics and flow characteristics of sliding discharge plasma under microsecond pulse actuation are studied, the optimal electrical actuation parameters and flow field characteristics are described.

Design of an adaptive feedforward/feedback combined control for piezoelectric actuated micro positioning stage

This paper proposes a novel feedforward/feedback combined control applied to a piezoelectric （PZT） actuated micro positioning stage. Based on the rate-dependent P–I inverse hysteresis model, a feedforward controller is built to compensate the hysteresis characteristics of the piezoelectric actuators, and the relevant parameters of the model are obtained through system identification. An adaptive control algorithm is adopted in feedback controller to reduce the influence of external disturbance. By introducing error-related forgetting factors to adjust the weight of old data and new data in real time, the robustness and accuracy of the control system are improved. The simulations are carried out to estimate the performance of the time-varying forgetting factors based adaptive algorithm. Finally, experimental tests are conducted to investigate the performance of the proposed feedforward/feedback combined control. The experimental results indicates that the settling time is 53 ms corresponding to the square wave signal and the maximum tracking error of a sine trajectory with the frequency of 20 Hz is 1.63 μm.