Actuation Efficiency Research Articles

Study of magnetic field distribution in anisotropic single twin-boundary magnetic shape memory (MSM) element in actuators

Magnetic shape memory effect exhibited by certain alloys at room temperature is known for almost 20 years. The most studied MSM alloys are Ni-Mn-Ga alloys which exhibit up to 12% magnetic field-induced strain (change in shape) depending on microstructure. A multibillion cycle operation without malfunction along with their “smart” properties make them very promising for application in electromagnetic (EM) actuators and sensors. However, considerable twinning stress of MSM crystals resulting in magneto-mechanical hysteresis decreases the efficiency and output force of MSM actuators. Whereas twinning stress of conventional MSM crystals has been significantly decreased over the years, novel crystals with Type II twin boundaries (TBs) possess even lower twinning stress. Unfortunately, the microstructure of MSM crystals with very low twinning stress tends to be unstable leading to their rapid crack growth. Whilst this phenomenon has been studied experimentally, the magnetic field distribution in anisotropic single twin-boundary MSM elements has not been considered yet. This paper analyses the magnetic field distribution in two-variant single twin-boundary MSM elements and discusses its effects on magnetic field-induced stress acting on the twin boundary.

Towards the noise reduction of piezoelectrical-driven synthetic jet actuators

This work details an experimental investigation aimed at reducing the noise output of piezoelectrical-driven synthetic jet actuators while minimising peak jet velocity reduction. The study considers double-chamber actuator for anti-phase noise suppression and lobed orifice as a method to enhance jet turbulent mixing to suppress jet noise. The study involved the design, manufacture and bench test of interchangeable actuator hardware. Hot-wire anemometry and microphone recordings were employed to acquire velocity and sound pressure level measurements respectively across a range of excitation frequencies for a fixed diaphragm clamping and input voltage. The data analysis indicated a 26% noise reduction (16dB) from operating a single-chamber, round orifice actuator to a double-chamber, lobed orifice one at the synthetic jet resonant frequency. Results also showed there was a small reduction in peak jet velocity of 7% (∼3m/s) between these two cases based on orifices of the same discharge area. The electrical-to-fluidic power conversion efficiency of the double-chamber actuator was found to be 15% for both orifice types at the resonant frequency; approximately double the efficiency of a single-chamber actuator.

Effects of Sweeping Jet Actuator Parameters on Flow Separation Control

A parametric experimental study was performed with sweeping jet actuators (fluidic oscillators) to determine their effectiveness in controlling flow separation on an adverse pressure gradient ramp. Parameters that were investigated included actuator placement (that is, pitch and spreading angles, streamwise location) and actuator size. Microvortex generators were also used to provide a reference control case for comparisons. Surface pressure measurements and surface oilflow visualization were used to characterize the effects of these parameters on the actuator performance. Two-dimensional particle image velocimetry measurements of the flowfield over the ramp and hot-wire measurements of the actuator’s jet flow were also obtained for selective cases. The results suggest that an actuator with a wider jet spreading (110 versus 70 deg) placed closer (2.3 versus 7 boundary-layer thickness upstream) to the flow separation location provides better performance. Different actuator sizes obtained by scaling down the actuator geometry produced different jet spreading. Scaling down the actuator (based on the throat dimensions) from to resulted in similar flow control performance; however, scaling down the actuator further to reduced the actuator efficiency by reducing the jet spreading considerably. The results of this study provide insight that can be used to design and select the optimal sweeping jet actuator configuration for flow control applications.

A novel approximate finite-time convergent guidance law with actuator fault

In this paper, a novel approximate finite-time convergent guidance law for missiles is presented to accurately intercept maneuvering targets when the actuators cannot perform as well as usual. First, the governing equations are proposed according to the relationship between missile and target at engagement phase, and a typical nonlinear mathematic model of actuator efficiency is built. Then, an adaptive multiple-input-multiple-output guidance law based on super-twisting algorithm is proposed to drive the line-of-sight angular rate to converge in a small region around zero in finite time. According to the proposed adaptive law, the information about maneuverability of target is not necessary, and the parameter drift problem is also addressed by dead-time control technique. Moreover, the proposed formulation is validated by means of the detailed stability analysis with strict Lyapunov function and simulation results.

Linear finite-difference bond graph model of an ionic polymer actuator

With the recent growing interest for soft actuation, many new types of ionic polymers working in air have been developed. Due to the interrelated mechanical, electrical, and chemical properties which greatly influence the characteristics of such actuators, their behavior is complex and difficult to understand, predict and optimize. In light of this challenge, an original linear multiphysics finite difference bond graph model was derived to characterize this ionic actuation. This finite difference scheme was divided into two coupled subparts, each related to a specific physical, electrochemical or mechanical domain, and then converted into a bond graph model as this language is particularly suited for systems from multiple energy domains. Simulations were then conducted and a good agreement with the experimental results was obtained. Furthermore, an analysis of the power efficiency of such actuators as a function of space and time was proposed and allowed to evaluate their performance.

An accurate and efficient method for piezoelectric coated functional devices based on the two-dimensional Green’s function for a normal line force and line charge

Because most piezoelectric functional devices, including sensors, actuators and energy harvesters, are in the form of a piezoelectric coated structure, it is valuable to present an accurate and efficient method for obtaining the electro-mechanical coupling fields of this coated structure under mechanical and electrical loads. With this aim, the two-dimensional Green’s function for a normal line force and line charge on the surface of coated structure, which is a combination of an orthotropic piezoelectric coating and orthotropic elastic substrate, is presented in the form of elementary functions based on the general solution method. The corresponding electro-mechanical coupling fields of this coated structure under arbitrary mechanical and electrical loads can then be obtained by the superposition principle and Gauss integration. Numerical results show that the presented method has high computational precision, efficiency and stability. It can be used to design the best coating thickness in functional devices, improve the sensitivity of sensors, and improve the efficiency of actuators and energy harvesters. This method could be an efficient tool for engineers in engineering applications.

Improved analytical modelling and finite element verification of stressed GaN microbeam resonators by piezoelectric actuation

The characteristics of piezoelectric micro-resonators based on vibrating beams essentially depend on two basic physical coefficients, an effective Young’s modulus (Ye) and a piezoelectric coupling factor (e31e). An improved analytic model is proposed with newly derived expressions of Ye and e31e that account for the anisotropic properties of the III-nitride materials and beam width, W. The analytic model applicable to the only axial stress is completed by finite element (FE) simulations that allow any spatial patterns of pre-stress in wafers to be studied. The value of e31e for wider beams is analytically demonstrated to be much higher than the usual e31, and a strong dependence of e31e on W is also confirmed by FE simulations. Resonance frequency (fr) and actuation efficiency (η) are numerically studied for several pre-stress patterns and beam dimensions. The fr is found to be sensitive to the beam width only for resonators under 2D pre-stress while the η to the stress magnitude regardless of stress pattern. Compared with measurements published for some fabricated resonators, both analytic and FE approaches agree well quantitatively for the resonance frequency and qualitatively for the dynamic amplitude. The results of this study can help design optimization, such as appropriate electrode length and suitable beam width, to gain better performance for this type of resonators.

Investigation and Development of the Thermal Preparation System of the Trailbuilder Machinery Hydraulic Actuator

It’s determined that the main part of trailbuilders operated in the North is the technology equipped by the hydraulic actuator. Further development of the northern territories will demand using of various means and ways machinery thermal preparation, and also the machinery of the northern fulfillment. On this basis problems in equipment operation are defined. One of the main is efficiency supplying of a hydraulic actuator. On the basis of the operating conditions’ analysis of trailbuilder hydraulic actuator operation it is determined, that under low negative temperatures the means of thermal preparation are necessary. The existing systems warm up only a hydraulic tank or warming up of the hydro equipment before the machinery operation is carried out under loading with intensive wears. Thus, with the purpose to raise the efficiency of thermal hydraulic actuator, operated far from stationary bases autonomous, energy saving, not expensive in creation and operation systems are necessary. In accordance with the analysis of means and ways of the thermal preparation of the hydraulic actuator and the thermal balance calculations of the (internal) combustion engine the system of the hydraulic actuator heating is offered and is being investigated. It contains a local hydraulic actuator warming up and the system of internal combustion engine heat utilization. Within research operation conditions of the local hydraulic actuator heating are viewed and determined, taking into account constructive changes to the local hydraulic actuator heating. Mathematical modelling of the heat technical process in the modernized hydraulic actuator is considered. As a result temperature changes of the heat-transfer and the hydraulic cylinder in time are determined. To check the theoretical researches and to define dependences on hydraulic actuator warming up, the experimental installation is made. It contains the measuring equipment, a small tank with the heat exchanger of the burnt gases of the internal combustion engine and the hydraulic cylinder with by-pass.

Spectral element formulation for an electrostrictive material embedded in a beam

In this paper, a spectrally formulated finite element in frequency domain for an electrostrictive material embedded in a composite beam is derived. The presence of quadratic non linearity of the electric field in the constitutive equation poses some challenge in the formulation of the model and we use convolution in the frequency domain. The formulation is carried out using Hamilton’s theorem and this is subsequently applied to a bimorph beam which has electrostrictive wafer mounted on the top as well as bottom surfaces of the beam. The bimorph beam is chosen so that we can control the beam by applying different and independent electric potentials for the top and bottom surfaces of the beam. The non linearity in the constitutive model results in the generation of additional nonlinear waves. The formulated spectral element elegantly captures these nonlinear waves. The efficiency of electrostrictive actuator for both single and multi modal open loop control is studied in detail. This aspect is demonstrated through a number of numerical examples. The studies also show that the control efficiency in electrostrictive actuator is limited by the amplitude of the electric field. When the electric field is beyond a certain level, it can be seen that although the amplitude of the primary wave decreases, non-linearity in the model causes sign reversal and splitting of incident and reflected waves. It can also be seen that the amplitude of nonlinear wave tend to increase with increase in applied electric field. The paper initially investigates the use of electrostrictive material as an actuator and this idea is gradually expanded to the use of electrostrictive material as a sensor. Various numerical experiments are carried out to demonstrate this aspect and its applications in the detection of the crack. It can be seen that the spectral element derived elegantly captures the location and size of the crack.

Pulse controlled microfluidic actuators with ultra low energy consumption

This paper presents the modelling, simulation, implementation and performance analysis of a novel electropermanent magnet based, bistable wireless microactuator for microvalves with milli Joule level energy consumption. The microactuator is powered wirelessly through inductive power transfer with energy buffered in a supercapacitor bank. Two millimeter sized rods of semi hard and hard magnetic materials are placed side by side with a current carrying coil around them. A 120μs pulse of 15V, 2.5A is applied to the coil, which creates or eliminates the externally available magnetic field. The plunger is either attracted or repelled by this magnetic field to open or close the valve respectively. The theoretical analysis and modelling aligns well with the experimental results. The microactuator consume as little as 0.97–2.5mJ of energy per actuation with no energy consumed between actuations. The actuation pulse width needs to be between 44 and 150μs. The actuator is capable of delivering large deflections in the range of 0.3–2.5mm, which is much greater than any of the state-of-the-art valves. The maximum holding force of the actuator is 220mN and the attraction force varies between 9.8–98mN. Energy consumption per actuation, actuation speed and deflection of the novel actuator are much better than any state-of-the-art microvalves, with the added advantages of wireless power and control. The momentary peak power requirement of 40W is met by the supercapacitor energy buffer which stores 90J per charge cycle, sourcing 37500 actuations. The energy efficiency and flexibility of this novel actuator can revolutionize the microactuator industry.

Adaptive Fuzzy Decentralized Control for a Class of Large-Scale Nonlinear Systems With Actuator Faults and Unknown Dead Zones

This paper studies the fault-tolerant control problem for a class of uncertain large-scale nonlinear systems with unknown dead zones and actuator failures, including outage, loss of effectiveness, and stuck. It is assumed that the lower and upper bounds of actuator efficiency factor, the unparametrizable time-varying stuck fault, the system coefficient, and the uncertain functions of our considered systems are unknown. By introducing a smooth function, fuzzy logic systems and a bound estimation approach, a decentralized backstepping design method of fault-tolerant tracking controller is developed for the systems under consideration. The proposed controller can compensate the effects of actuator faults and dead zones completely. It is proved that all the signals in the closed-loop systems are ultimately bounded, and the tracking control performance can be achieved by the proposed controller. In comparing with the existing results, the restrictions on the number of failures are removed and the stuck fault is allowed to be time-varying. Finally, simulation results show the efficiency of the proposed control scheme.

MHD-RLC discharge model and the efficiency characteristics of plasma synthetic jet actuator

Major factors affecting efficiency of plasma synthetic jet actuator (PSJA) are analyzed based on a new discharge model in the present paper. The model couples the magnetohydrodynamics (MHD) equations with the resistor–inductor–capacitor (RLC) equations, and is able to resolve the time-dependent voltage fall on the sheath region and arc region, which is critical in analyzing energy loss in the heating process. This model is integrated into the commercial CFD software by a two-equation method. Results show that in a typical capacitive discharge at microsecond scale, the maximum energy loss is the sheath energy loss, which accounts for nearly half of the discharge energy, while the radiation loss is less than 5%. The discharge time is an important parameter for the PSJA efficiency. A short discharge time less than 1μs will effectively reduce the sheath energy loss, while a longer discharge time will decrease the thermodynamic efficiency.

Parametric Study of Paraelectric and Peristaltic Pulsed DBD Plasma Actuation for Aerodynamic Flow Control Based on PIV

Using single and multiple dielectric barrier discharge plasma actuators, the velocity fields induced by steady, pulsed, asynchronous, and duty cycle plasma actuation are studied based on Particle Image Velocimetry (PIV). First, the flow fields induced by a single dielectric barrier discharge with different discharge models and actuation parameters are investigated. According to the velocity distributions, a parametric study on the influence of excitation voltages, carrier frequencies, pulse frequencies, and duty ratios on plasma actuation is presented and the optimum actuation parameters are provided. Emphatically, through double actuators alternating discharge, the peristaltic acceleration plasma actuation, a new plasma actuation mode, has been proposed and studied. The efficiency of the plasma actuators in steady and pulsed discharge modes is explored. The velocity field induced by plasma actuation with different phase angles and duty cycle ratios is acquired and the momentum transfer characteristics of the flow field were discussed. Finally, based on the above-mentioned results, the technical superiority and mechanism of the peristaltic acceleration induced by multiple dielectric barrier discharge plasma actuators are analyzed.

Experimental research on multichannel discharge circuit and multi-electrode plasma synthetic jet actuator

To solve the low efficiency of plasma synthetic jet actuator (PSJA), a multichannel discharge technique based on the concept of voltage relay is put forward and a new multi-electrode plasma synthetic jet actuator (ME-PSJA) is designed. The experiment shows the multichannel discharge technique can enlarge the discharge channel distance by multiplying the discharge channel number without increasing the input voltage. With a 1 nF discharge capacitor, the discharge efficiency of three channels discharge increases by 135% compared with the standard one channel discharge. When the discharge capacitor increases to 0.3 μF, four discharge channels still improve the discharge efficiency by 119% as well. Schlieren flow visualization confirms that ME-PSJA also outperforms the 2-electrode PSJA in terms of jet velocity and duration time, and both are increased by about 50%.

Analysis of symmetrical flatness actuator efficiencies for UCM cold rolling mill by 3D elastic–plastic FEM

As the basis for a flatness control system, flatness actuator efficiency describes an actuator’s control ability, but it is difficult to obtain an actuator efficiency factor accurately through rolling tests because of the complicated subsidiary facilities of the mill. This paper proposes a novel simulation approach that is applied to obtain the actuator efficiency factors in terms of work roll bending, intermediate roll bending, and intermediate roll shifting for a six-high Universal Crown Control mill (UCM mill). A three-dimensional (3D) finite element model of the mill was developed to simulate the dynamic strip rolling process. The validation of rolling experiments shows that this model has enough precision, where the relative error of strip thickness between simulated values and actual values is less than 1.0%. The effects of the actuators on strip thickness profile, crown, edge drop, and elongation difference of longitudinal fibers were investigated. In the case of different actuator parameters, the curves of actuator efficiency factors were obtained and quantitatively descripted by truncated Legendre orthogonal polynomials. The mechanism of flatness control was studied based on an analysis of the actuator’s influence rule on the elastic deflection of rolls and 3D distribution of rolling pressure. The results indicate that the curves of actuator efficiency factors have a symmetrical upside-down v-shaped distribution and contain the quadratic and quartic flatness components. The actuator efficiency factors of intermediate roll shifting have a nonignorable variation with the change of actuator parameters. This study is the first attempt to obtain actuator efficiency factors for UCM mill using an elastic–plastic finite element method.

Dumbbell Fluidic Tweezers for Dynamical Trapping and Selective Transport of Microobjects

Mobile microvortices generated by rotating nickel (Ni) nanowires (NW) have been reported as capable of inducing fluidic trapping that can be precisely focused and translated to manipulate microobjects. Here, a new design for significantly enhanced fluidic trapping is reported, which is a dumbbell (DB)‐shaped magnetic actuator, assembled by a Ni NW and two polystyrene microbeads. In contrast to the single mode of tumbling trapping possessed by Ni NW, the magnetic dumbbell is able to perform dynamical trapping and implement on‐demand transport of microobjects in three modes, i.e., tumbling, wobbling, and rolling. Experiments are conducted to demonstrate the robustness and efficacy of the fluidic trap by the DB actuator. And simulations using a finite element model compare the fluidic traps induced by NW and DB, followed by further discussion on the actuation and transport efficiency of NW and DB fluidic tweezers (FT). At last, some practical issues regarding the application of DB FT are addressed.

Experimental method to quantify the efficiency of the first two operational stages of nanosecond dielectric barrier discharge plasma actuators

A method to quantify the efficiency of the first two operational stages of a nanosecond dielectric barrier discharge (ns-DBD) plasma actuator is proposed. The method is based on the independent measurements of the energy of electrical pulses and the useful part of the energy which heats up the gas in the discharge region. Energy input is calculated via a back current shunt technique as the difference between the energy given and the energy reflected back. The ratio of the difference of the latter two quantities and the energy input gives the electrical efficiency (ηE) of a ns-DBD. The extent of the energy deposited is estimated via Schlieren visualizations and infrared thermography measurements. Then, the ideal power flux obtained if all the inputted energy was converted into heat is calculated. Transient surface temperature was measured via infrared thermography and used to solve a 1D inverse heat transfer problem in a direction normal to the surface. It gives as output the actual power flux. The estimated ratio between the two power fluxes represents a quantification of the mechanical fluid efficiency (ηFM) of a ns-DBD plasma actuator. Results show an inverse proportionality between ηE, and ηFM, and the thickness of the barrier. The efficiency of the first two operational stages of a ns-DBD is further defined as η = ηE · ηFM.

Improving actuation efficiency through variable recruitment hydraulic McKibben muscles: modeling, orderly recruitment control, and experiments

Hydraulic control systems have become increasingly popular as the means of actuation for human-scale legged robots and assistive devices. One of the biggest limitations to these systems is their run time untethered from a power source. One way to increase endurance is by improving actuation efficiency. We investigate reducing servovalve throttling losses by using a selective recruitment artificial muscle bundle comprised of three motor units. Each motor unit is made up of a pair of hydraulic McKibben muscles connected to one servovalve. The pressure and recruitment state of the artificial muscle bundle can be adjusted to match the load in an efficient manner, much like the firing rate and total number of recruited motor units is adjusted in skeletal muscle. A volume-based effective initial braid angle is used in the model of each recruitment level. This semi-empirical model is utilized to predict the efficiency gains of the proposed variable recruitment actuation scheme versus a throttling-only approach. A real-time orderly recruitment controller with pressure-based thresholds is developed. This controller is used to experimentally validate the model-predicted efficiency gains of recruitment on a robot arm. The results show that utilizing variable recruitment allows for much higher efficiencies over a broader operating envelope.

Analysis of solenoid based linear compressor for household refrigerator

This article presents the analytical modeling of an oil-free solenoid actuator based linear compressor used in household refrigerators. The stator coil was excited with the pulse width modulated signal which caused linear oscillations in the armature using helical spring. Dynamic characteristics of the linear compressor were studied analytically considering the nonlinearity of the gas and electromagnetic force. The system dynamic models were validated with the finite element simulation as well as a specially designed experimental setup. Frequency response functions of stroke to current as well as pressure to current ratios were generated to evaluate the effect of excitation frequency on the compressor performance. The higher efficiency of the solenoid actuator was achieved when excited at the natural frequency. The results show that the natural frequency of the designed system is around 19 Hz and the work done in a cycle is approximately 1.3 J. Additionally, 47% isentropic and 87% electrical efficiency were achieved.

Electro-mechanical efficiency of plasma synthetic jet actuator driven by capacitive discharge

A simplified model is established to estimate the jet exit density variation of a plasma synthetic jet actuator (PSJA) driven by a capacitive arc discharge. This model, in conjunction with phase-locked planar particle imaging velocimetry (PIV) measurements, enables the calculation of jet mechanical energy for different operating conditions. Discharge energy is directly calculated based on waveforms of applied voltage and discharge current. The ratio of jet mechanical energy to discharge energy provides the absolute electro-mechanical efficiency. Results indicate that PSJA is characterized by a rather low electro-mechanical efficiency in the order of 0.1%, while the maximum observed value under tested conditions is 0.22%. Electro-mechanical efficiency improves significantly with nondimensional energy deposition, and appears largely independent of jet exit diameter.