Array Of Actuators Research Articles

High-Lift Enhancement of an Airfoil Using Arrays of Discrete Wall Jets

The circulation of a high-lift airfoil is enhanced using a spanwise array of fluidically oscillating wall jets to engender a Coanda-like effect on the suction surface near the cove between the flap and the main element. The actuation jets manipulate the interaction between the main element boundary layer and the cove jet to overcome flow separation over the flap and yield high-lift performance that is comparable to or better than conventional high-lift airfoils. The fluidic actuation enables effective operation at larger flap deflections while diminishing the sensitivity to cove characteristics. The performance of the actuator array varies with both the jet momentum coefficient and the spanwise periodic jet spacing. It is shown that the lift increment per jet, which for a sufficiently sparse jet array is invariant with jet spacing, diminishes as jet spacing is reduced due to spanwise jet interactions. Accordingly, the overall lift increment scales with the number of active jets and jet density, and a characteristic spanwise jet spacing is identified for optimal performance.

Harnessing Deep Learning of Point Clouds for Morphology Mimicking of Universal 3D Shape‐Morphing Devices

Shape‐morphing devices, a crucial branch in soft robotics, hold significant application value in areas like human–machine interfaces, biomimetic robotics, and tools for biological systems. To achieve 3D programmable shape morphing (PSM), the deployment of array‐based actuators is essential. However, a critical knowledge gap in 3D PSM is controlling the complex systems formed by these soft actuator arrays to mimic the morphology of the target shapes. This study, for the first time, represents the configuration of shape‐morphing devices using point cloud data and employing deep learning to map these configurations to control inputs. Shape Morphing Net (SMNet), a method that realizes the regression from point cloud to high‐dimensional control input vectors, is proposed. It has been applied to 3D PSM devices with three different actuator mechanisms, demonstrating its universal applicability to inversely reproduce the target shapes. Further, applied to previous 2D PSM devices, SMNet significantly enhances control precision from 82.23% to 97.68%. In the demonstrations of morphology mimicking, 3D PSM devices successfully replicate arbitrary target shapes obtained either through 3D scanning of physical objects or via 3D modeling software. The results show that within the deformable range of 3D PSM devices, accurate reproduction of the desired shapes is achievable.

A novel underactuated smart surface for parts feeding and sorting

In material handling, numerous solutions have been proposed to enhance the flexibility and adaptability of transport systems. Among these solutions, smart surfaces stand out as one of the most interesting responses, utilizing an array of actuators for common feeding tasks. The current paper focuses on a novel system within this category, notable for its distinguishing factor of being underactuated. With this characteristic, the concept leads to a simplified cost-effective design and a not actively driven functioning, leveraging gravity or object own velocity to manipulate the material flow maintaining top class performances, as the sorting rate reaches 4000 pcs/h. Specifically, the article begins with an introduction of the concept design and its digital model, followed by a description of the experimental setup built to test the surface’s functionality and evaluate the predictions of the virtual counterpart. On top of that, a method to determine the essential parameters for the surface simulation is proposed and applied. As a result, the prototype successfully completed the three main intralogistic tasks experimented, i.e., sorting, slowing, and stopping of packages. Lastly, the digital model outcomes of the same operations were computed and compared with the measured results, demonstrating an accuracy of prediction with displacements and time errors below 7%.

Experimental investigation of a spanwise plasma jet array in a turbulent boundary layer for skin-friction drag reduction

Three different types of particle imaging velocimetry (PIV) measurements, namely planar-PIV, micro-PIV, and stereo-PIV, are integrated to provide a full picture of the interaction between a spanwise plasma jet array and a turbulent boundary layer (TBL) at Reθ = 1208. Quiescent-flow characterization reveals that the plasma actuator array induces a wavy jet. With increasing duty cycle (DC), the peak jet velocity grows yet the height of the jet body decreases. When the TBL is actuated by such a plasma jet array, the spanwise distribution of the relative drag variation exhibits two regions with opposite signs, and the formation of these two regions can be attributed to the upwash and the downwash effects of the plasma-induced vortex, respectively. After spatial-averaging in the plasma actuation zone, net drag reduction (DR = 3.2%) is only achieved at the lowest DC of 10%. Although, by increasing the duty cycle, more drag reduction can be obtained in the upwash zone, the accompanying drag increase in the downwash zone is even prominent.

Controlling cantilevered adaptive X-ray mirrors.

Modeling the behavior of a prototype cantilevered X-ray adaptive mirror (held from one end) demonstrates its potential for use on high-performance X-ray beamlines. Similar adaptive mirrors are used on X-ray beamlines to compensate optical aberrations, control wavefronts and tune mirror focal distances at will. Controlled by 1D arrays of piezoceramic actuators, these glancing-incidence mirrors can provide nanometre-scale surface shape adjustment capabilities. However, significant engineering challenges remain for mounting them with low distortion and low environmental sensitivity. Finite-element analysis is used to predict the micron-scale full actuation surface shape from each channel and then linear modeling is applied to investigate the mirrors' ability to reach target profiles. Using either uniform or arbitrary spatial weighting, actuator voltages are optimized using a Moore-Penrose matrix inverse, or pseudoinverse, revealing a spatial dependence on the shape fitting with increasing fidelity farther from the mount.

Battery-Free, Wireless Multi-Modal Sensor, and Actuator Array System for Pressure Injury Prevention.

Simultaneous monitoring of critical parameters (e.g., pressure, shear, and temperature) at bony prominences is essential for the prevention of pressure injuries in a systematic manner. However, the development of wireless sensor array for accurate mapping of risk factors has been limited due to the challenges in the convergence of wireless technologies and wearable sensor arrays with a thin and small form factor. Herein, a battery-free, wireless, miniaturized multi-modal sensor array is introduced for continuous mapping of pressure, shear, and temperature at skin interfaces. The sensor array includes an integrated pressure and shear sensor consisting of 3D strain gauges and micromachined components. The mechanically decoupled design of the integrated sensor enables reliable data acquisition of pressure and shear at skin interfaces without the need for additional data processing. The sensor platform enables the analysis of interplay among localized pressure, shear, and temperature in response to changes in the patient's movement, posture, and bed inclination. The validation trials using a novel combination of wireless sensor arrays and customized pneumatic actuator demonstrate the efficacy of the platform in continuous monitoring and efficient redistribution of pressure and shear without repositioning, thereby improving the patient's quality of life.

High-performance and wavelength-transplantable on-chip Fourier transform spectrometer using MEMS in-plane reconfiguration

On-chip spectrometers with high compactness and portability enable new applications in scientific research and industrial development. Fourier transform (FT) spectrometers have the potential to realize a high signal-to-noise ratio. Here we propose and demonstrate a generalized design for high-performance on-chip FT spectrometers. The spectrometer is based on the dynamic in-plane reconfiguration of a waveguide coupler enabled by an integrated comb-drive actuator array. The electrostatic actuation intrinsically features ultra-low power consumption. The coupling gap is crucial to the spectral resolution. The in-plane reconfiguration surmounts the lithography accuracy limitation of the coupling gap, boosting the resolution to 0.2 nm for dual spectral spikes over a large bandwidth of 100 nm (1.5–1.6 μm) within a compact footprint of 75 μm×1000 μm. Meanwhile, the in-plane tuning range can be large enough for arbitrary wavelengths to ensure the effectiveness of spectrum reconstruction. As a result, the proposed spectrometer can be easily transplanted to other operation bands by simply scaling the structural parameters. As a proof-of-concept, a mid-infrared spectrometer is further demonstrated with a dual-spike reconstruction resolution of 1.5 nm and a bandwidth of 300 nm (4–4.3 μm).

Flow Measurements Above A DBD Plasma Actuator Array By Means Of Defocusing PTV

Lagrangian defocusing particle tracking velocimetry (DPTV) measurements are conducted in a thin, wall-parallel volume above a plasma actuator array that is applied to mimic the effect of wall oscillations by inducing alternating, wall-parallel forcing in opposite directions into the air above the actuator surface. The aim of the experiments is to capture the plasma-induced flow structures in otherwise quiescent air in order to increase the understanding of different actuation parameters. For this purpose, high-speed particle image velocimetry equipment with one camera is used in a DPTV setup, where the out-of-plane particle coordinate is obtained through the diameter of a defocused particle image. On this basis, an approach for continuous particle tracking in several consecutive frames is presented, allowing to derive three component, three dimensional velocity and acceleration data. Light reflections that occur on the adjacent actuator surface give raise to particular challenges concerning the measurement uncertainty estimation as well as the calibration procedure for the evaluation of the wall-normal coordinate of tracer particles. To overcome the latter, a calibration approach is presented for which solid particles are applied to the actuator surface and their particle image diameter is captured at different camera positions in a separate measurement. The estimation of in-plane and out-of-plane displacement measurement uncertainties is conducted following a newly-developed procedure where the deviation of particle displacements from a straight track is evaluated for measurements in quasi-quiescent air. The obtained results show the suitability of DPTV measurement technique for the practical application of the characterization of flow structures above a plasma actuator array. The measurement accuracy is found to be limited due to the available illumination, which depends on the used components. The measured flow fields together with optical and electrical measurement data allow for a further analysis of the present forcing strategy. Particularly, by recording phase-resolved, three-dimensional flow velocity and acceleration fields in the vicinity of the wall, the spatio-temporal occurrence and homogeneity of the near-wall forcing effects can be analyzed in future investigations.

Suntrack Weather: Real Time Solar Power Weather Update

The need for efficient solar energy utilization has become increasingly evident in the face of climate change and growing energy demands. This led to the recognition of the problem of suboptimal energy capture in fixed solar panels. Through extensive research and observations, it was identified that conventional fixed solar panels do not fully harness the available solar energy due to the sun's changing position throughout the day. This realization prompted the exploration of advanced tracking systems to improve energy capture. How the Problem was identified: In addressing the challenge of maximizing solar energy capture, various solar tracking technologies have been developed. Single-axis trackers are among the initial solutions, adjusting panels on a horizontal axis to follow the sun's east-west movement. However, these systems fail to account for the sun's changing altitude throughout the day. Dual-axis solar tracking systems emerged as a more advanced solution, capable of continuously aligning solar panels in both the horizontal and vertical planes. These systems employ an array of sensors, microcontrollers, and actuators to precisely track the sun's position, thereby significantly enhancing energy output. KEYWORDS: Sun-track weather, Real-time, Solar power, Weather update, Sun tracking technology.

Low-Voltage High-Frequency Lamb-Wave-Driven Micromotors.

By leveraging the benefits of a high energy density, miniaturization and integration, acoustic-wave-driven micromotors have recently emerged as powerful tools for microfluidic actuation. In this study, a Lamb-wave-driven micromotor is proposed for the first time. This motor consists of a ring-shaped Lamb wave actuator array with a rotor and a fluid coupling layer in between. On a driving mechanism level, high-frequency Lamb waves of 380 MHz generate strong acoustic streaming effects over an extremely short distance; on a mechanical design level, each Lamb wave actuator incorporates a reflector on one side of the actuator, while an acoustic opening is incorporated on the other side to limit wave energy leakage; and on electrical design level, the electrodes placed on the two sides of the film enhance the capacitance in the vertical direction, which facilitates impedance matching within a smaller area. As a result, the Lamb-wave-driven solution features a much lower driving voltage and a smaller size compared with conventional surface acoustic-wave-driven solutions. For an improved motor performance, actuator array configurations, rotor sizes, and liquid coupling layer thicknesses are examined via simulations and experiments. The results show the micromotor with a rotor with a diameter of 5 mm can achieve a maximum angular velocity of 250 rpm with an input voltage of 6 V. The proposed micromotor is a new prototype for acoustic-wave-driven actuators and demonstrates potential for lab-on-a-chip applications.

Biomimetic array actuators for multisituation low-grade energy harvesting

Low-grade energy resources are abundant and widely available, yet efficiently harnessing and continuously collecting this energy presents a considerable challenge, leading to significant energy losses. In this work, we introduce a biomimetic array actuator constructed with a sodium alginate (SA)-tellurium nanowires (Te NWs)/polyvinylidene fluoride (PVDF) bilayer structure that responds to various stimuli such as low temperature, natural light, and humidity. Significantly, this actuator generates autonomous self-oscillatory motion driven by an internal mechanical feedback loop. Utilizing its high-frequency self-oscillating motion, this actuator efficiently harnesses low-grade energy sources, including waste heat, non-concentrated sunlight, and exhaust steam. Under various driving conditions, including a 60 °C heater, natural light, and 70 °C steam, the 3 × 3 array actuators can generate peak voltages of 1.5 V, 2 V, and 4 V, respectively. This research has the potential to unlock opportunities for a range of low-grade energy harvesting technologies utilizing flexible actuators.

Cooperative transport in sea star locomotion

It is unclear how animals with radial symmetry control locomotion without a brain. Using a combination of experiments, mathematical modeling, and robotics, we tested the extent to which this control emerges in sea stars (Protoreaster nodosus) from the local control of their hundreds of feet and their mechanical interactions with the body. We discovered that these animals compensate for an experimental increase in their submerged weight by recruiting more feet that synchronize in the power stroke of the locomotor cycle during their bouncing gait. Mathematical modeling of the mechanics of a sea star replicated this response to loading without a central controller. A robotic sea star was found to similarly recruit more actuators under higher loads through purely decentralized control. These results suggest that an array of biological or engineered actuators are capable of cooperative transport where the actuators are dynamically recruited by the mechanics of the body. In particular, the body's vertical oscillations serve to recruit feet in greater numbers to overcome the weight to propel the body forward. This form of distributed control contrasts the conventional view of animal locomotion as governed by the central nervous system and offers inspiration for the design of engineered devices with arrays of actuators.

Openable Double‐Microtube Structure Driven by Pneumatic Balloon Actuator Arrays for Tubular Organ‐on‐a‐Chip

Microfluidic platforms have revolutionized research in biomedical engineering, enabling efficient and controlled experimentation. Here, we present a novel microfluidic device, the double‐microtube, which offers parallel flow of different fluids. The device is fabricated by transforming a flat structure on a substrate using pneumatic balloon actuator arrays. The inner and outer tubes of the device can be independently controlled, allowing for individual opening and closing of each tubular structure. The inner and outer tubes have diameters of 1 mm and 3 mm, respectively. The device has been successfully tested for cell culture, showcasing its potential application for tubular organ‐on‐a‐chip studies, such as blood vessels and the small intestine. The presented double‐microtube structure promises a new level of control for microfluidic studies, offering exciting opportunities for researchers in the field of biomedical engineering. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Numerical Investigation by Applying Microballoon Actuators on High-Altitude Propeller

Microballoon actuators as a potential active flow control device have been studied for years. However, most studies have relied on experimental methods to investigate its effects. In this paper, we utilized the numerical method of steady-state RANS to explore the feasibility of applying microballoon actuators to suppress flow separation on a wing section and a high-altitude propeller. The geometric design, including shapes and positions for microballoons, is introduced, and these microballoons are fully resolved for the numerical models to better assess the influence of sensitive parameters. The turbulent model used in simulations is well validated in comparison with experimental data. In the wing section model, computational results show that at Re=2×105, placing nonrotation microballoons close to the separation point can suppress separation bubbles and decrease drag by 12% before the stall angle of attack. In the propeller model, computational results show that placing a microballoon actuator array with a proper dimension and position on the blade can also effectively suppress the crossflow separation appearing at the trailing edge. At a rotational speed of 450 rpm, the efficiency enhancement can reach a maximum of 1.6%.

Numerical Investigations of Outer-Layer Turbulent Boundary Layer Control for Drag Reduction Through Micro Fluidic-Jet Actuators

Drag reduction through turbulent boundary layer control (TBLC) is an essential way to develop green aviation technologies. Compared with traditional approaches for drag reduction, turbulence drag reduction is a relatively new technology, particularly for skin friction drag reduction, and it is becoming a hotspot problem worldwide. This paper focuses on the research of micro fluidic-jet actuators used for outer-layer boundary layer control with high-performance computing (HPC). This study aims to reduce turbulent drag by reshaping the flow structure within the turbulent boundary layer. To ensure the calculation accuracy of the core region and reduce the consumption of computing resources, a zonal LES/RANS strategy and WMLES method are proposed to simulate the effects of fluidic-actuators for outer-layer boundary control, in which high-performance computing has to be involved. The studies are performed on the classical zero-gradient turbulent flat plate cases, in which three different control strategies named “W-control,” “V-control,” and “VW-control” are used and compared to study the effects of drag reduction under a low Reynolds number at Reτ = 470 and a higher Reynolds number at Reτ = 4700. The mechanism for drag reduction is analysed via a pre-multiplied spectral method and a parallel dynamic mode decomposition (DMD) method. The results show that the present approach can effectively simulate the outer-layer turbulent boundary control where the “V-control” with the fluidic-jet actuator array behaves well to achieve an average drag reduction (DR) rate of more than 5% for the high Reynolds number case of the flat plate boundary layer. The high Reynolds shear stress and turbulent kinetic energy distribution in the boundary layer region show an obvious uplift under the effects of actuators, which is the main mechanism for drag reduction.

Dynamic braille display based on surface-structured PVC gel

Braille displays are a class of human–computer interaction electromechanical devices that display dynamic braille through an array of actuators. However, existing actuators for braille displays suffer from issues such as bulky size, heavy weight, and small tactile displacement, leading to difficulties in improving their resolution and readability. To address the above issues, we developed a novel electroactive artificial muscle actuator and applied it to braille displays. The novel actuator consists of a surface-structured PVC gel and planar electrodes. To investigate the effect of surface structure on the performance of novel PVC gel actuators, four types of surface-structured PVC gels were fabricated by a casting process, and their actuation performance was tested. The results show that the conical and frustum conical array structures are more favorable for improving the displacement of novel PVC gel actuators, while the cylindrical and quadrangular array structures are more favorable for improving their recovery forces. We observed both surface structure and dynamic electrical actuation, suggesting that the actuation of the novel actuator is mainly caused by the deformation of the surface structure of the array. We also analyzed electrowetting effects in PVC gels using the Lippmann–Young equation, to explain the differences in the performance of surface-structured PVC gels with different contact angles. Moreover, six multilayer actuators composed of PVC gels with a conical surface array structure are applied to the braille display unit to display the braille digits from 0 to 9. It has been shown that the novel PVC gel actuator has excellent mechanical properties, which makes it an ideal solution for braille displays.

Directional sound radiation from a rectangular panel and the high frequency limit.

Directional sound radiation focuses sound in a specific direction and reduces sound radiation in other directions. This study uses a flat panel driven by an actuator array to realize two-dimensional directional sound radiation by the acoustic contrast control algorithm. The aliasing effect at higher frequencies is analyzed based on the modal vibration of the panel, and a method for estimating the high frequency limit is proposed. Actuator arrays with different parameters are simulated to verify the efficacy of the proposed method and compare the acoustic contrast response with the conventional loudspeaker arrays.

Airfoil friction drag reduction based on grid-type and super-dense array plasma actuators

To improve the cruise flight performance of aircraft, two new configurations of plasma actuators (grid-type and super-dense array) were investigated to reduce the turbulent skin friction drag of a low-speed airfoil. The induced jet characteristics of the two actuators in quiescent air were diagnosed with high-speed particle image velocimetry (PIV), and their drag reduction efficiencies were examined under different operating conditions in a wind tunnel. The results showed that the grid-type plasma actuator was capable of producing a wall-normal jet array (peak magnitude: 1.07 m/s) similar to that generated in a micro-blowing technique, while the super-dense array plasma actuator created a wavy wall-parallel jet (magnitude: 0.94 m/s) due to the discrete spanwise electrostatic forces. Under a comparable electrical power consumption level, the super-dense array plasma actuator array significantly outperformed the grid-type configuration, reducing the total airfoil friction drag by approximately 22% at a free-stream velocity of 20 m/s. The magnitude of drag reduction was proportional to the dimensionless jet velocity ratio (r), and a threshold r = 0.014 existed under which little impact on airfoil drag could be discerned.

Adaptive tactile interaction transfer via digitally embroidered smart gloves

Human-machine interfaces for capturing, conveying, and sharing tactile information across time and space hold immense potential for healthcare, augmented and virtual reality, human-robot collaboration, and skill development. To realize this potential, such interfaces should be wearable, unobtrusive, and scalable regarding both resolution and body coverage. Taking a step towards this vision, we present a textile-based wearable human-machine interface with integrated tactile sensors and vibrotactile haptic actuators that are digitally designed and rapidly fabricated. We leverage a digital embroidery machine to seamlessly embed piezoresistive force sensors and arrays of vibrotactile actuators into textiles in a customizable, scalable, and modular manner. We use this process to create gloves that can record, reproduce, and transfer tactile interactions. User studies investigate how people perceive the sensations reproduced by our gloves with integrated vibrotactile haptic actuators. To improve the effectiveness of tactile interaction transfer, we develop a machine-learning pipeline that adaptively models how each individual user reacts to haptic sensations and then optimizes haptic feedback parameters. Our interface showcases adaptive tactile interaction transfer through the implementation of three end-to-end systems: alleviating tactile occlusion, guiding people to perform physical skills, and enabling responsive robot teleoperation.

Experimental Study on Hypersonic Double-Wedge Induced Flow Based on Plasma Active Actuation Array

The double-wedge configuration is a typical characteristic shape of the rudder surface of high-speed aircraft. The impact of the shock wave/boundary layer interaction and the shock wave/shock wave interaction resulting from the double wedge on aircraft aerodynamics cannot be ignored. The aerodynamic performance of the aircraft would be seriously affected. Accordingly, to reduce the wave drag, and to relieve the thermal load and pressure load, flow control is required for the shock wave/shock wave interaction and the shock wave/boundary layer interaction induced by the double-wedge configuration. In this paper, double-wedge shock wave/shock wave interaction is controlled by a high-energy surface arc discharge array and observed by high-speed schlieren flow field measurement at Mach 8. The 30-channel discharge array is set on the primary wedge plane, and actuation is generated. Hypersonic V shock wave/shock wave interaction is effectively controlled by the shock wave array induced by the high-energy surface arc discharge array, which makes the shock wave/shock wave interaction structure disappear or intermittent. The potential control mechanism is to reduce strong shock wave interaction by transforming the type of shock wave interaction. Therefore, the ability of plasma array actuation to control complex shock wave/shock wave interaction is verified, which provides a new method for hypersonic shock wave/shock wave interaction control.