High-speed Actuator Research Articles

Multi-actuation and PI control: a simple recipe for high-speed and large-range atomic force microscopy.

High speed atomic force microscopy enables observation of dynamic nano-scale processes. However, maintaining a minimal interaction force between the sample and the probe is challenging at high speed specially when using conventional piezo-tubes. While rigid AFM scanners are operational at high speeds with the drawback of reduced tracking range, multi-actuation schemes have shown potential for high-speed and large-range imaging. Here we present a method to seamlessly incorporate additional actuators into conventional AFMs. The equivalent behavior of the resulting multi-actuated setup resembles that of a single high-speed and large-range actuator with maximally flat frequency response. To achieve this, the dynamics of the individual actuators and their couplings are treated through a simple control scheme. Upon the implementation of the proposed technique, commonly used PI controllers are able to meet the requirements of high-speed imaging. This forms an ideal platform for retroactive enhancement of existing AFMs with minimal cost and without compromise on the tracking range. A conventional AFM with tube scanner is retroactively enhanced through the proposed method and shows an order of magnitude improvement in closed loop bandwidth performance while maintaining large range. The effectiveness of the method is demonstrated on various types of samples imaged in contact and tapping modes, in air and in liquid.

Thermomechanical Actuator-Based Three-Axis Optical Scanner for High-Speed Two-Photon Endomicroscope Imaging.

This paper presents the design and characterization of a three-axis thermomechanical actuator-based endoscopic scanner for obtaining ex vivo two-photon images. The scanner consisted of two sub-systems: 1) an optical system (prism, gradient index lens, and optical fiber) that was used to deliver and collect light during imaging and 2) a small-scale silicon electromechanical scanner that could raster scan the focal point of the optics through a specimen. The scanner can be housed within a 7 mm Ø endoscope port and can scan at the speed of 3 kHz × 100 Hz × 30 Hz along three axes throughout a 125 × 125 × 100 μm3 volume. The high-speed thermomechanical actuation was achieved through the use of geometric contouring, pulsing technique, and mechanical frequency multiplication (MFM), where MFM is a new method for increasing the device cycling speed by pairing actuators of unequal forward and returning stroke speeds. Sample cross-sectional images of 15-μm fluorescent beads are presented to demonstrate the resolution and optical cross-sectioning capability of the two-photon imaging system.

High-Speed Actuation and Mechanical Properties of Graphene-Incorporated Shape Memory Polyurethane Nanofibers

We prepared poly(e-caprolactone) (PCL)-based shape memory polyurethane (PU) nanofibers incorporating three kinds of graphene, that is, graphene oxide (GO), PCL-functionalized graphene with PCL (f-GO), and reduced graphene (r-GO) to investigate their mechanical and shape memory properties. Incorporation of graphene into the PU nanofibers increased the modulus and breaking stress compared to that of pure PU nanofibers. In particular, the f-GO nanofibers showed the largest enhancement in mechanical properties because of increased interaction between graphene and the polymer matrix. In the shape memory test, f-GO or r-GO-incorporated PU nanofibers showed actuation speed that was much faster than that of pure PU nanofibers. The shape recovery time of 1 wt % f-GO or r-GO nanofibers was 8 s, whereas that of the PU nanofibers and GO-incorporated nanofibers were 27 and 13 s, respectively. This study demonstrates that incorporation of f-GO into shape memory PU nanofibers can be used effectively to achieve both high...

Methodology and validation for blast and shock testing of structures using high-speed hydraulic actuators

The extreme loads generated by blast events, both man-made and accidental, can cause devastating consequences for structures and their components. Typically, the development of analysis methodologies, design procedures and hardening strategies is driven by conclusions that have been obtained experimentally via field testing with live explosives. These types of experiments, although generally effective, are often expensive and due to the extreme environment, do not provide clear visual evidence and quantitative data of structural response throughout the explosive event.In 2006, a blast simulation facility was designed and constructed in order to provide blast-like loadings on structures and components in a controlled laboratory setting. The Blast Simulator, located at the University of California, San Diego, was the first facility to utilize ultra-fast, hydraulically drive, computer-controlled actuators to generate impulsive loadings on full-scale structures. Because the experiments do not involve explosives and the subsequent fireball, high speed cameras and other instrumentation can be effectively used to produce quantitative, as well as high resolution visual data in a repeatable environment.Since 2006, over 500 experiments have been conducted using the Blast Simulator for both validation studies and exploratory research. This paper serves to summarize the current methodology for imparting blast and shock-like loads, as well as to validate the Blast Simulator’s effectiveness in producing accurate, controllable and repeatable loading on a range of civil and military structures.

Nonlinear viscoelastic dynamic modeling of high-speed polypyrrole-based trilayer bending plate-like actuators based on first-order shear deformation plate theory

In this study, we intend to introduce a nonlinear dynamic theory for analyzing dynamic behavior of plate-like polypyrrole-based trilayer actuators for the first time. Within the displacement field of a first-order shear deformation plate theory and contemplating the nonlinear strain–displacement relations, nonlinear equations of motion are derived using Hamilton’s principle. The nonlinear governing equations are solved using the generalized differential quadrature method together with Newmark’s time integration scheme and the Newton–Raphson iterative method. For the assessment of the accuracy of the present theory, experimental data available in the literature are utilized. Two types of boundary conditions for both steady-state and dynamic analyses are investigated. The present results indicate the importance of considering geometric nonlinearity in the system.

Dynamic compensation by fusing a high-speed actuator and high-speed visual feedback with its application to fast peg-and-hole alignment

This paper presents a dynamic compensation concept to grapple with the dynamic defects of a traditional robot arm, especially while performing high-speed endpoint regulations. The proposed high-speed dynamic compensation concept offers a new point of view for cooperating with a traditional manipulator to realize highly dexterous performance of manipulations. The concept is realized through adoption of a high-speed light-weight actuator as well as endpoint closed loop configured high-speed cameras. The dynamic compensation is analyzed experimentally with 1000 Hz visual feedback and a high-speed finger for a robot arm in the case of one degree of freedom. The advantage of the proposed approach is that the modeling for the robot system’s dynamics is not needed, whereas it is necessary and trivial in order to realize high-speed regulations by traditional approaches. Thus, the control issue becomes easier with the proposed approach. As an application for this concept, fast peg-and-hole alignment with large position and attitude uncertainty is studied. The alignment algorithm is based on a visual compliance strategy. Alignment experiments show that with the proposed concept of dynamic compensation as well as visual compliant motion control, robust and fast convergence was realized for most cases.

A non-explosive test method for generating wide area dynamic blast-type pressure pulse loading on armored panels

The ever-changing face of modern warfare drives the need for improved vehicle armor and the means of testing new protection systems. Test methods to-date have been based on explosive loading or using apparatus such as shock tubes and gas guns to produce representative loading. Each methodology comes with its own set of limitations, such as poor visibility and remote facilities required for explosive testing or limited impact area for the gas gun based methods. A new impact-based method has been developed to address some of these limitations by employing the UC San Diego Blast Simulator, a system composed of high-speed (up to 66 m/s) actuators and a tuned pressure pulse generating projectile. The system has been used to impact a wide area (406 × 406 mm) on large-sized (610 × 610 mm) armor panels at a specific impulse of 7520 Pa s. Panels tested using the non-explosive Blast Simulator were compared to panels subjected to actual blasts with C4 explosive. Metrics of interest were damage modes, extent of damage, and pressure pulse attenuation relative to steel. Results indicate similar damage modes but larger degree of internal damage for the actual blast-tested composite sandwich panels, but a similar level of permanent deformation for the steel panels. The sandwich panels exhibited up to 37% reduction in initial-average transmitted acceleration and 76% reductions in peak transmitted acceleration compared to steel armor panels, at a weight savings of up to 49%. This non-explosive test allows for generating consistent and repeatable wide area pressure pulse loads to facilitate performance comparison and optimization of armor panel designs.

Fast Component Placement with Optimized Long-Stroke Passive Gravity Compensation Integrated in a Cylindrical/Tubular PM Actuator

Applications such as vibration isolation, gravity compensation, pick-and-place machines, etc., would benefit from (long-stroke) cylindrical/tubular permanent magnet (PM) actuators with integrated passive gravity compensation to minimize the power consumption. As an example, in component placing (pick-and-place) machines on printed circuit boards, passive devices allow the powerless counteraction of translator including nozzles or tooling bits. In these applications, an increasing demand is arising for high-speed actuation with high precision and bandwidth capability mainly due to the placement head being at the foundation of the motion chain, hence, a large mass of this device will result in high force/power requirements for the driving mechanism (i.e. an H-bridge with three linear permanent magnet motors placed in an H-configuration). This paper investigates a tubular actuator topology combined with passive gravity compensation. These two functionalities are separately introduced, where the combination is verified using comprehensive three dimensional (3D) finite element analyses.

Nanostructure fabrication on germanium and silicon by nanocoining imprint technique

Abstract Germanium (Ge) and silicon (Si) material response to indentation with a nanostructured die is investigated. A diamond die attached to a high speed actuator previously used to create large arrays of nanofeatures on metallic surfaces was used to create nanofeatures on Ge and Si samples. The pressure induced transformation of Ge and Si from a diamond cubic brittle phase to a more ductile beta-tin metallic phase due to the nanofeatures on the die was investigated. Results using the dynamic nanocoining method showed chip-like deformation around the individual nanofeatures indicative of the beta-tin phase transformation at the nanofeature level. Micro-Raman measurements confirmed the metallic transition from evidence including metastable and amorphous phases after indentation. Indents created using a common linear indentation method exhibited similar behavior. The Si nanofeature deformation was compared to electroless (EL) nickel and the deformation differed as dictated by the mechanism of material flow. Although not observed in Si, fracture occurred in some Ge indents at higher loads as a result of the lower fracture toughness compared to Si.

Dimensional metrology in the macroscopic range with sub-nanometre resolution

Nanomeasuring machines are devices for solving various positioning and measuring problems in a range of several millimetres with sub-nanometre resolution. These devices are used for positioning, probing and measurements. The combination of this machine with a scanning force microscope leads to improved quality in the calibration of standards. The measurement accuracy and stability of the scanning force microscope are important for the achievable measurement uncertainty. Many systems are influenced by the creep, hysteresis and bending of the included piezo actuators. A scanning force microscope head with a combined deflection detection system that comprises an interferometer and a beam deflection system was developed. Due to this system, it is possible to simultaneously measure the displacement, bending and torsion of the cantilever with only one focussed beam. An additional high-speed piezoelectric actuator for the vertical motion of the cantilever was integrated and is controlled by the bending signal. The outcome of this additional control system is a much higher scan speed. The interferometer system can be used for precise measurement of the vertical cantilever motion. Hence, non-linearity and hysteresis in the actuator do not affect the measurement. The device was used for several calibration measurements on step height and lateral standards. This article deals with the set-up, function and application of a scanning force microscope head for dimensional metrology with the nanomeasuring machines.

High-Speed Magnetic Microrobot Actuation in a Microfluidic Chip by a Fine V-Groove Surface

Microrobots are promising tools for the treatment of biological cells because of their lack of skill dependence, high throughput, and high repeatability. Integration of a microfluidic chip and robotics based on microelectromechanical systems technology is a key challenge for biomedical innovations. In addition to the advantage of environmental control by a microfluidic chip, robots enable physical operations on the cell with high throughput. This paper presents high-speed microrobotic actuation driven by permanent magnets in a microfluidic chip. The developed microrobot has a milli-Newton-level output force from a permanent magnet, micrometer-level positioning accuracy, and drive speed of over 280 mm/s. The riblet surface, which is a regularly arrayed V-groove, reduces fluid friction and enables high-speed actuation. Ni and Si composite fabrication was employed to form the optimum riblet shape on the microrobot's surface by wet and dry etching. The evaluation experiments show that the microrobot can be actuated at a rate of up to 90 Hz, which is more than ten times higher than that of the microrobot without a riblet. Two distinguish applications of the developed microrobots were demonstrated in a microfluidic chip.

Performance Limits of Microactuation with Vanadium Dioxide as a Solid Engine

Miniaturization of the steam engine to the microscale is hampered by severe technical challenges. Microscale mechanical motion is typically actuated with other mechanisms ranging from electrostatic interaction, thermal expansion, and piezoelectricity to more exotic types including shape memory, electrochemical reaction, and thermal responsivity of polymers. These mechanisms typically offer either large-amplitude or high-speed actuation, but not both. In this work we demonstrate the working principle of a microscale solid engine (μSE) based on the phase transition of VO2 at 68 °C with large transformation strain (up to 2%), analogous to the steam engine invoking large volume change in a liquid-vapor phase transition. Compared to polycrystal thin films, single-crystal VO2 nanobeam-based bimorphs deliver higher performance of actuation both with high amplitude (greater than bimorph length) and at high speed (greater than 4 kHz in air and greater than 60 Hz in water). The energy efficiency of the devices is calculated to be equivalent to thermoelectrics with figure of merit ZT = 2 at the working temperatures, and much higher than other bimorph actuators. The bimorph μSE can be easily scaled down to the nanoscale, and operates with high stability in near-room-temperature, ambient, or aqueous conditions. On the basis of the μSE, we demonstrate a macroscopic smart composite of VO2 bimorphs embedded in a polymer, producing high-amplitude actuation at the millimeter scale.

Application of the Novint Falcon haptic device as an actuator in real-time control

AbstractThis paper describes the development of an embedded system whose purpose is to control the Novint Falcon as a robot, and to develop a control experiment that demonstrates the use the Novint Falcon as a robotic actuator. The Novint Falcon, which is a PC input device, is “haptic” in the sense that it has a force feedback component. Its relatively low cost compared with other platforms makes it a good candidate for academic application in robot modeling and control. An embedded system is developed to interface with the multiple motors and sensors present in the Novint Falcon, which is subsequently used to control three independent Novint Falcons for a “ballon- plate” experiment. The results show that the device is a viable solution for high-speed actuation of small-scale mechanical systems.

High speed adaptive liquid microlens array

Liquid microlenses are attractive for adaptive optics because they offer the potential for both high speed actuation and parallelization into large arrays. Yet, in conventional designs, resonances of the liquid and the complexity of driving mechanisms and/or the device architecture have hampered a successful integration of both aspects. Here we present an array of up to 100 microlenses with synchronous modulation of the focal length at frequencies beyond 1 kHz using electrowetting. Our novel concept combines pinned contact lines at the edge of each microlens with an electrowetting controlled regulation of the pressure that actuates all microlenses in parallel. This design enables the development of various shapes of microlenses. The design presented here has potential applications in rapid parallel optical switches, artificial compound eye and three dimensional imaging.

고속 공기압 실린더의 피스톤 실 단면형상 변화에 따른 마찰특성

The paper deals with the design of a new low-friction seal for a pneumatic cylinder with high speed actuation. The seal performance with variation of the cross sections in piston seals with elastomeric material was investigated to minimize the friction forces using ABAQUS. The contact stress and strain distributions and frictional forces of the piston seals were investigated with variation of interference fits, supply pressures and friction coefficients. To develop adequate and productive procedures, the finite element models of the piston seals were created and nonlinear analysis of a seal design was conducted in order to build further knowledge and understanding of the seal`s performance characteristics.

MEMS Grating with Interdigitated-Comb Structure

Grating as an important spectral component can be applied to spectral analysis, filtering, dispersion compensation, sensing and so on. Their advantages are compactness, potentially high actuation speed and the ability to deflect light at large angles. In this paper, a MEMS interdigitated-comb grating actuated by a comb-drive actuator is presented. An experiment is performed to demonstrate how the proposed grating works with an applied voltage. At 85V, the displacement of comb-drive actuator can achieve 2.1μm; accordingly the gap between the interdigitated-comb gratings varies by 2.1μm. The mechanical and the optical sensing properties of the MEMS grating are both analyzed in this paper. This grating can be widely used in optical sensor and to detect the micro-displacement.

Magnetic shape memory effect in orbital-spin-coupled system MnV2O4

Magnetic-field(H)-induced shape memory effect without temperature variation is demonstrated by a combination of H-sweep and H-rotation in an orbital-spin-coupled spinel-type insulating system MnV2O4. A rotation of the direction of a magnetic field of 5 T in the low-temperature tetragonal phase gives rise to a large macroscopic strain up to 1%, which stems from a 90° rotation of tetragonal domains. The results show several possible ways of macroscopic shape control in this class of matter, and may open a possibility of high-speed actuators free from the eddy current.

Polyethylene oxide–polytetrahydrofurane–PEDOT conducting interpenetrating polymernetworks for high speed actuators

In recent years, numerous studies on electro-active polymer (EAP) actuators have beenreported. One promising technology is the elaboration of electronic conductingpolymer-based actuators with interpenetrating polymer network (IPNs) architecture. Inthis study, the synthesis and characterisation of conducting IPNs for actuatorapplications is described. The IPNs are synthesised from polyethylene oxide (PEO)and polytetrahydrofurane (PTHF) networks in which the conducting polymer(poly(3,4-ethylenedioxythiophene)) is incorporated. In a first step, PEO/PTHF IPNswere prepared via an ‘in situ’ process using poly(ethylene glycol) methacrylateand dimethacrylate and hydroxytelechelic PTHF as starting materials. The IPNmechanical properties were examined by DMA and tensile strength tests.N-ethylmethylimidazolium bis(trifluoromethanesulfonyl)imide(EMITFSI) swollen PEO/PTHF IPNs show ionic conductivities up to10−3 S cm−1 at30 °C. In a second step, the conducting IPN actuators were prepared byoxidative polymerisation of 3,4-ethylenedioxithiophene (EDOT) usingFeCl3 as an oxidising agent within the PEO/PTHF IPN host matrix. The frequency response performanceof the bending conducting IPN actuator was then evaluated. The resulting actuator exhibits amechanical resonance frequency of up to 125 Hz with 0.75% strain for an applied potential of ± 5 V.

Capacitive and faradic charge components in high-speed carbon nanotube actuator

When submitted to square-wave potentials of ±2 V, single-walled carbon nanotube films with an ionic liquid, taking part of an actuator, show high-frequency electromechanical responses (up to 100 Hz), with anodic current evolutions showing two maxima. Similar anodic chronoamperometric responses have been obtained from films of conducting polymers exchanging balancing anions with the electrolyte during reaction, being described by two stretched exponential functions deduced on physico-chemical bases: oxidation under nucleation–relaxation structural control and oxidation/swelling completion under diffusion control. Now by adding a third stretched function, describing a greater contribution now of the charge of the electrical double layer, a good mathematical fit of the chronoamperometric response of the carbon nanotube films was carried out. By recovering the original physico-chemical meaning of the electrochemical stretched functions, capacitive and structural faradic components of the chronoamperometric charge were quantified as a function of the applied frequency (1–10 Hz). The capacitive component of the charge ranges with frequency between 8.6% and 12.2% of the involved charge. The faradic (reactive) component ranges between 91.4% and 87.8%, being the main contributor to the volume variations in the actuating films. The order of magnitude of the diffusion coefficients was 10 −6 cm 2 s −1, in good agreement with the fast response of the reactive actuators constructed with those materials. A good separation of capacitive and faradic components will allow a better design of electrochemical applications of single-walled carbon nanotube films.

Light-Driven Droplet Manipulation Technologies for Lab-on-a-Chip Applications

Droplet-based (digital) microfluidics has been demonstrated in many lab-on-a-chip applications due to its free cross-contamination and no dispersion nature. Droplet manipulation mechanisms are versatile, and each has unique advantages and limitations. Recently, the idea of manipulating droplets with light beams either through optical forces or light-induced physical mechanisms has attracted some interests, since light can achieve 3D addressing, carry high energy density for high speed actuation, and be patterned and dynamically reconfigured to generate a large number of light beams for massively parallel manipulation. This paper reviews recent developments of various optical technologies for droplet manipulation and their applications in lab-on-a-chip.