Array Of Actuators Research Articles

Shock wave boundary layer interaction controlled by surface arc plasma actuators

An array of 16 surface arc plasma actuators (SAPAs) is employed to control the shock wave boundary layer interaction (SWBLI) at a 26° compression ramp in a Mach 2.0 flow. A new electrical circuit is used to actuate all 16 SAPAs. The electrical measurement reveals significant augmentation in peak current (200 A) and an energy deposition of 1.05 J, which are the nominal characteristics of the setup. The SAPA array is later applied for SWBLI control. The actuator array is placed upstream of the SWBLI and operates at four different frequencies, namely, 500 Hz, 1 kHz, 2 kHz, and 5 kHz. In the wind tunnel experiment, high-speed schlieren at 25 000 frames per second is used for flow visualization. The shock wave system is modified significantly by the controlling gas blobs (CGBs) or controlling gas bulbs (CGBUs) generated by SAPAs. The foot portion of the separation shock wave disappears, and the oblique shock wave bifurcates when the CGBs pass through the interaction region. The shock weakening effect is further verified through the rms of the schlieren intensity of the same phase.

Understanding Fish Linear Acceleration Using an Undulatory Biorobotic Model with Soft Fluidic Elastomer Actuated Morphing Median Fins.

Although linear accelerations are an important common component of the diversity of fish locomotor behaviors, acceleration is one of the least-understood aspects of propulsion. Analysis of acceleration behavior in fishes with both spiny and soft-rayed median fins demonstrates that fin area is actively modulated when fish accelerate. We implemented an undulatory biomimetic robotic fish model with median fins manufactured using multimaterial three-dimensional printing-a spiny-rayed dorsal fin, soft-rayed dorsal/anal fins, and a caudal fin-whose stiffnesses span three orders of magnitude. We used an array of fluidic elastomeric soft actuators to mimic the dorsal/anal inclinator and erector/depressor muscles of fish, which allowed the soft fins to be erected or folded within 0.3 s. We experimentally show that the biomimetic soft dorsal/anal fin can withstand external loading. We found that erecting the soft dorsal/anal fins significantly enhanced the linear acceleration rate, up to 32.5% over the folded fin state. Surprisingly, even though the projected area of the body (in the lateral plane) increased 16.9% when the median fins were erected, the magnitude of the side force oscillation decreased by 24.8%, which may have led to significantly less side-to-side sway in the robotic swimmer. Visualization of fluid flow in the wake of median fins reveals that during linear acceleration, the soft dorsal fin generates a wake flow opposite in direction to that of the caudal fin, which creates propulsive jets with time-variant circulations and jet angles. Erectable/foldable fins provide a new design space for bioinspired underwater robots with structures that morph to adapt to different locomotor behaviors. This biorobotic fish model is also a potentially promising system for studying the dynamics of complex multifin fish swimming behaviors, including linear acceleration, steady swimming, and burst and coast, which are difficult to analyze in freely swimming fishes.

Investigation of tactile bump array actuated with ionic polymer–metal composite cantilever beams for refreshable braille display application

This paper presents an innovative digitally controllable tactile bump array driven with ionic polymer–metal composite (IPMC) actuators for a refreshable braille display application. The array with 5 × 5 PDMS bump elements was implemented in front of the IPMC cantilever beams as the contact interfaces of fingertips and IPMC actuators. The designed circuit allows to access every single element through unique wire-pair selection so that the actuated electrical signal could directly apply to both electrodes of the IPMC cantilever beam. A soft and thin PDMS layer was realized underneath the IPMC cantilever beams to maintain the level while the IPMC actuators loaded with the bumps in the non-actuation state and to minimize the liquid evaporation containing in the IPMC actuator. The fabricated actuator array is qualitatively tested to ensure that the fingertip can properly feel the force variation when the bump is driven by the IPMC actuator. The displacements of the bumps with different weights under the same driving condition of the IPMC actuators is also measured. A novel method of using the experimental results for in-situ characterization of the Young’s modulus of the IPMC cantilever beam during its operation is developed. This scheme can be employed in the situation in which the cantilever beam is subjected to an unknown external force during its partial motion cycle. The results show that a maximum moment variation of 1.6 μN m can be generated for the fabricated 3 mm × 0.8 mm × 0.2 mm IPMC cantilever beam under an 8-V square wave actuation for 1 s. The maximum blocked forces at the bump surfaces reach 0.68 mN and 0.55 mN for the bumps of masses 4.1 mg and 15.5 mg, respectively.

Stimuli-responsive and on-chip nanomembrane micro-rolls for enhanced macroscopic visual hydrogen detection.

Nanomembrane rolling offers advanced three-dimensional (3D) mesostructures in electronics, optics, and biomedical applications. We demonstrate a high-density and on-chip array of rolled-up nanomembrane actuators with stimuli-responsive function based on the volume expansion of palladium in hydrogen milieu. The uniform stimuli-responsive behavior of high-density nanomembrane rolls leads to huge macroscopic visual detection with more than 50% transmittance change under optimization of micropattern design. The reversible shape changing between rolled and flat (unrolled) statuses can be well explained on the basis of the elastic mechanical model. The strain change in the palladium layer during hydrogen absorption and desorption produces a marked change in the diameter of nanomembrane rolls. We found that a functional palladium layer established an external compressive strain after hydrogen stimuli and thus also reduced the rolls' diameters. The large area of the nanomembrane roll array performs excellent nonelectrical hydrogen detection, with response and recovery speeds within seconds. Our work suggests a new strategy to integrate high-density 3D mesoscale architectures into functional devices and systems.

A heuristic approach for actuator layout designs in deformable mirror devices based on current value optimization

Deformable mirrors are vital components in fundus imaging modality incorporating adaptive optics systems. The application of precisely controlled electric currents to multiple electrodes located under the mirror surface deform its shape so that optical aberrations caused by a patient’s eye can be nullified. The higher number of actuators used, the more accurately the mirror surface can be transformed to a target shape. However, deformable mirror manufacturability limitations demand that the number of electromagnetic actuators be minimized, so there is a pressing need for an efficient method to determine the layout of a minimum number of actuators that will deliver desired aberration correction performance. In this paper, we present an actuator layout design method based on the degree to which each actuator contributes to mirror shaped adjustment, calculated according to the amount of electric current supplied to individual actuators. This method minimizes the number of actuators while preventing the error between a target mirror shape and the actual deformed mirror shape from exceeding a certain limit. To assess the aberration correction performance for each actuator layout, we also provide a method for optimizing the electric currents supplied to an array of actuators that will correctly adjust the mirror surface to target Zernike modes, corresponding to defocus, astigmatism, coma and trefoil aberrations, given the imposition of upper and lower limits upon the currents supplied to the actuators.

Vibration due to non-circularity of a rotating ring having discrete radial supports - With application to thin-walled rotor/magnetic bearing systems

This paper investigates the vibration arising in a thin-walled cylindrical rotor subject to small non-circularity and coupled to discrete space-fixed radial bearing supports. A Fourier series description of rotor non-circularity is incorporated within a mathematical model for vibration of a rotating annulus. This model predicts the multi-harmonic excitation of the rotor wall due to bearing interactions. For each non-circularity harmonic there is a set of distinct critical speeds at which resonance can potentially arise due to flexural mode excitation within the rotor wall. It is shown that whether each potential resonance occurs depends on the multiplicity and symmetry of the bearing supports. Also, a sufficient number of evenly spaced identical supports will eliminate low order resonances. The considered problem is pertinent to the design and operation of thin-walled rotors with active magnetic bearing (AMB) supports, for which small clearances exist between the rotor and bearing and so vibration excitation must be limited to avoid contacts. With this motivation, the mathematical model is further developed for the case of a distributed array of electromagnetic actuators controlled by feedback of measured rotor wall displacements. A case study involving an experimental system with short cylindrical rotor and a single radial AMB support is presented. The results show that flexural mode resonance is largely avoided for the considered design topology. Moreover, numerical predictions based on measured non-circularity show good agreement with measurements of rotor wall vibration, thereby confirming the validity and utility of the theoretical model.

Simulation and Optimal Design of Acoustic Field of Orthotropic Piezoelectric Composite Material Ultrasonic Phased Linear Array Actuator

Simulation and Optimal Design of Acoustic Field of Orthotropic Piezoelectric Composite Material Ultrasonic Phased Linear Array Actuator

Characterization of a piezoelectric MEMS actuator surface toward motion-enabled reconfigurable RF circuits

As an alternative to highly constrained hard-wired reconfigurable RF circuits, a motion-enabled reconfigurable circuit (MERC) offers freedom from transmission line losses and homogeneous materials selection. The creation of a successful MERC requires a precise mechanical mechanism for relocating components. In this work, a piezoelectric MEMS actuator array is modeled and experimentally characterized to assess its viability as a solution to the MERC concept. Actuation and design parameters are evaluated, and the repeatability of high quality on-axis motion at greater than 1 mm s−1 is demonstrated with little positional error. Finally, an initial proof-of-concept circuit reconfiguration has been demonstrated using off-the-shelf RF filter components. Although initial feasibility tests show filter performance degradation with an additional insertion loss of 0.3 dB per contact, out-of-band rejection degradation as high as 10 dB, and ripple performance reduction from 0.25 dB to 1.5 dB, MERC is proven here as an alternative to traditional approaches used in reconfigurable RF circuit applications.

Control of incident shock-induced boundary-layer separation using steady micro-jet actuators at M∞ = 3.5

Experiments were carried out to control an incident shock-induced separation associated with 22° shock generator in a Mach 3.5 flow using an array of steady micro-jet actuators. Four micro-jet actuator configurations based on the variation in their pitch angle [Formula: see text], skew angle [Formula: see text] and span-wise spacing were used. Each of these configurations were placed 14 δ upstream of the interaction and operated with injection pressures ( Poj) varying from 140 to 643 kPa. While no major variations in separation characteristics were observed for Poj < 140 kPa, significant modifications were observed beyond [Formula: see text] of 140 kPa and until 208.5 kPa. Amongst all the four control configurations, micro-jet vortex generator 2 ([Formula: see text] showed the best control with a 2 δ downstream shift in separation point location relative to no-control. The shift is also accompanied with a change in maximum zero-crossing frequency towards higher frequency (almost twice), a reduction in the intermittency length and an increase in the correlation value between the boundary layer just upstream of the interaction and the intermittent region. These results indicate that the effectiveness of micro-jet vortex generator 2 is probably due to the improved entrainment levels in the shear layer induced by the micro-vortices which are generated downstream of these devices. The increase of the skew angle [Formula: see text] from 180° to 270° for the same pitch angle of β = 45° (micro-jet vortex generator 3) seems to have no major impact on the separation characteristics. The reduction in the span-wise spacing (micro-jet vortex generator 4) resulted in deterioration of the flow field due to the jet-to-jet interaction with increasing injection pressures.

Interacting Automultiscopic 3D With Haptic Paint Brush in Immersive Room

In this paper, we propose an interactive artwork system with automultiscopic 3D and haptic paint brush in an immersive room. Our system consists of a 81-view automultiscopic display, a handheld haptic paint brush, and a large-scale color palette station in a CAVE-like cubic room filled with the visual scene of the artwork. The 81-view rendering and multiplexing technology is applied by setting up the virtual cameras in the off-axis layout. The haptic paint brush is designed and implemented using a 2D array of multiple piezoelectric actuators. It provides the tactile feedback of spatial distance information between a virtual brush and a distal 3D object displayed on the automultiscopic display for the precise control of the brush when it is interacting with automultiscopic 3D. We demonstrate a proof-of-concept system that integrates a classic artwork into an innovative interactive system using novel multimedia and interactive technologies and evaluate our system using the handheld haptic brush for its performance and usability to enhance the user experiences.

Low‐Complexity Decentralized Active Damping of One‐Dimensional Structures

In the paper, we propose distributed feedback control laws for active damping of one‐dimensional mechanical structures equipped with dense arrays of force actuators and position and velocity sensors. We consider proportional position and velocity feedback from the neighboring nodes with symmetric gains. Achievable control performance with respect to stability margin and damping ratio is discussed. Compared to full‐featured complex controllers obtained by modern design methods like LQG, H‐infinity, or mu‐synthesis, these simplistic controllers are more suitable for experimental fine tuning and are less case‐dependent, and they shall be easier to implement on the target future smart‐material platforms.

Controller for microfluidic large-scale integration.

Microfluidic devices with integrated valves provide precise, programmable fluid handling platforms for high-throughput biological or chemical assays. However, setting up the infrastructure to control such platforms often requires specific engineering expertise or expensive commercial solutions. To address these obstacles, we present a Kit for Arduino-based Transistor Array Actuation (KATARA), an open-source and low-cost Arduino-based controller that can drive 70 solenoid valves to pneumatically actuate integrated microfluidic valves. We include a python package with a GUI to control the KATARA from a personal computer. No programming experience is required.

Solution-based process with thermal UV treatment for fabrication of piezoelectric PZT films for an actuator array at temperatures under 450 °C

We report on the fabrication of a low-temperature sol-gel derived lead zirconium titanate (PZT) film and actuator, achieved by introducing a thermal ultraviolet/ozone (UV/O3) treatment. A spin-coated PZT gel film was irradiated with UV light on a heated stage (200°C) in ambient O3, before crystallization. The thermal UV/O3 treatment created a reducing environment inside the PZT gel film, which inhibited the formation of the pyrochlore phase, leading to the direct formation of the perovskite phase after annealing at 450°C. The low-temperature processed PZT film exhibited a preferential (111) orientation. The remanent polarization, coercive field, and leakage current of the PZT film obrained using this fabrication technique, were 23.6μC/cm2, 109.6kV/cm, and 10−6A/cm2, respectively. We also fabricated an actuator using the low-temperature processed PZT film. The maximum displacement was approximately 130nm at 10V, which was close to the prediction of the simulation results. The proposed process shows great promise for the integration of PZT films with other systems.

Flexible Active Skin: Large Reconfigurable Arrays of Individually Addressed Shape Memory Polymer Actuators

AbstractA high‐resolution flexible active skin with a matrix of 32 × 24 individually addressable tactile pixels on a 4 mm pitch is reported, based on shape memory polymer (SMP) actuators. The intrinsic multistable nature of SMPs, and their more than 100‐fold variation in stiffness over a narrow temperature range, enables dense arrays of actuators exhibiting simultaneously large strokes and high holding forces. The control challenge of addressing a very large number of soft actuators is solved by patterning an array of miniature stretchable heaters on a thin SMP membrane, so that one single pneumatic supply is sufficient to rapidly and selectively reconfigure any or all elements. The device consists of a 40 µm thick SMP layer, on which 32 × 24 stretchable heaters are integrated, interconnected by a flexible printed circuit board, and bonded to a stretchable 3D‐printed pneumatic chamber. Each taxel can be individually controlled via row/column addressing, and requires 2.5 s to latch to a different state. The active skin weighs only 55 g and is 2 mm thick. More than 99% of the 768 taxels are fully functional, with a lifetime in excess of 20 000 cycles. This architecture enables applications in haptic displays, active camouflage, biomimetic robots, microfluidics, and new human machine interfaces.

Large displacement bi-directional out-of-plane Lorentz actuator array for surface manipulation

This paper presents a large displacement out-of-plane Lorentz actuator array for surface manipulation. Actuators are formed from single crystal silicon flexible serpentine springs on either side of a rigid crossbar containing a narrow contact pillar. A rigid mounting rail system was employed to enable a 5 × 5 array, which offers scalability of the array size. Analytical and finite element models were used to optimize actuator design. Individual actuators were tested to show linear deflection response of ±150 µm motion, using a ±14.7 mA current in the presence of a 0.48 T magnetic field. This actuator array is suitable for various 2D surface modification applications due to its large deformation with low current and temperature of operation, and narrow contact area to a target surface.

Ink-Jet Printing of Micro-Electro-Mechanical Systems (MEMS)

Beyond printing text on paper, inkjet printing methods have recently been applied to print passive electrical and optical microparts, such as conductors, resistors, solder bumps and polymeric micro lenses. They are also useful to print micro-electro-mechanical systems (MEMS) as sub-millimeter sensor and actuator arrays, such as multifunctional skins applicable to robotic application and ambient monitoring. This paper presents the latest review of a few successful cases of printable MEMS devices. This review shows that inkjet printing is good for printing two-dimensional or surface MEMS devices from a small unit to an array over a large area. In the future, three-dimensional printing of multi-materials, from metal, plastic, to ceramic, will open the possibility of realizing more variety and function of a large-areal MEMS array, for a mobile electro-mechanical systems.

Multisource Rotating Shield Brachytherapy Apparatus for Prostate Cancer

Our purpose is to present a novel multisource rotating shield brachytherapy (RSBT) apparatus for the simultaneous precise angular and linear positioning of partially shielded 153Gd brachytherapy sources in interstitial needles for the treatment of locally advanced prostate cancer. It is designed to lower the dose to nearby healthy tissues, the urethra in particular, relative to conventional high-dose-rate brachytherapy techniques. Following needle implantation through the patient template, an angular drive mechanism is docked to the patient template. Each needle is coupled to a multisource afterloader catheter by a connector passing through a shaft. The shafts are rotated about their axes by translating a moving template between 2 stationary templates. The shafts' surfaces and moving template holes are helically threaded with the same pattern such that translation of the moving template causes simultaneous rotation of the shafts. The rotation of each shaft is mechanically transmitted to the catheter-source-shield combination, inside the needles, via several key-keyway pairs. The catheter angles are simultaneously incremented throughout treatment, and only a single 360° rotation of all catheters is needed for a full treatment.For each rotation angle, source depth in each needle is controlled by a multisource afterloader, which is proposed as an array of belt-driven linear actuators, each of which drives a wire that controls catheter depth in a needle. Treatment plans demonstrated that RSBT with the proposed apparatus reduced urethralD0.1cm3 (the minimum dose delivered to the hottest 0.1cm3 of the urethra) below that of conventional high-dose-rate brachytherapy by 31% for urethral dose gradient volume within 3mm of the urethra surface.Treatment time to deliver 20Gy with the proposed multisource RSBT apparatus by use of nineteen 62.4-GBq 153Gd sources was 122minutes. The proposed RSBT delivery apparatus enables a mechanically feasible urethra-sparing treatment technique for prostate cancer in a clinically reasonable time frame.

Skin-friction drag reduction in a channel flow with streamwise-aligned plasma actuators

Direct Numerical Simulations in a turbulent channel flow at a moderate Reynolds number are performed in order to investigate the potential of Dielectric Barrier Discharge (DBD) plasma actuators for the reduction of the skin-friction drag. The idea is to use a sparse array of streamwise-aligned plasma actuators to produce near-wall spanwise-orientated jets in order to destroy the events which transport high-speed fluid towards the wall. It is shown that it is possible to reduce the drag by about 33.5% when the streamwise-aligned actuators are configured to generate appropriate spanwise-orientated jets very close to the wall so that the sweeps which are mainly responsible for the skin-friction are destroyed. We demonstrate that it is possible to achieve significant drag reduction with a sparse array of streamwise-aligned plasma actuators, with one order of magnitude less actuators than previous experiments in a similar set-up.

High-Speed Experiments on Combustion-Powered Actuation for Dynamic Stall Suppression

This work documents high-speed wind-tunnel experiments conducted on a pitching airfoil equipped with an array of combustion-powered actuators. The main objective of these experiments was to demonstrate the stall-suppression capability of combustion-powered actuators on a high-lift rotorcraft airfoil (the VR-12) at relevant Mach numbers. Through unsteady pressure measurements at the airfoil surface, it was shown that combustion-powered actuators could positively affect the stall behavior of the VR-12 at Mach numbers up to 0.4. Static airfoil results demonstrated 25 and 50% increases in poststall lift at Mach numbers of 0.4 and 0.3, respectively. Deep dynamic stall results showed cycle-averaged lift coefficient increases up to 11% at Mach 0.4. Furthermore, it was shown that these benefits could be achieved with relatively few pulses during the downstroke and with no need to preanticipate the stall event. The flow mechanisms responsible for stall suppression were investigated using particle image velocimetry. The flow structures found at these Mach numbers appeared to be very similar to the flow structures noted previously at very low Mach numbers.

Laser beam shaping with magnetic fluid-based liquid deformable mirrors**Project supported by the National Natural Science Foundation of China (Grant No. 51675321), Shanghai Municipal Natural Science Foundation, China (Grant No. 15ZR1415800), and the Innovation Program of Shanghai Municipal Education Commission, China (Grant No. 14ZZ092).

A new controllable laser beam shaping technique is demonstrated, where a magnetic fluid-based liquid deformable mirror is proposed to redistribute the laser phase profile and thus change the propagation property of the beam. The mirror is driven by an inner miniature actuator array along with a large outer actuator. The inner actuator array is used for deforming the magnetic fluid surface, while the outer actuator is used to linearize the fluid surface response and amplify the magnitude of the deflection. In comparison to other laser beam shaping techniques, this technique offers the advantages such as simplicity, low cost, large shape deformation, and high adaptability. Based on a fabricated prototype of the liquid deformable mirror, an experimental AO system was set up to produce a desired conical surface shape that shaped the incident beam into a Bessel beam. The experimental results show the effectiveness of the proposed technique for laser beam shaping.