High-speed Actuator Research Articles

A compact structure and high-speed actuator designed by imitating the movement of wave

By imitating the natural phenomenon of waves pushing leaves, a compact novel wave-type piezoelectric actuator is proposed in this paper. Compared to traditional inchworm piezoelectric actuators, it combines the clamping unit and driving unit into an arc-shaped flexible driving foot (AFDF). Clamping and driving functions are realized by alternately controlling two ends of the AFDF using two piezoelectric stacks (PESs). One motion unit instead of two makes control simpler, the structure more compact and a faster movement speed. The static model of the AFDF is developed to characterize the mapping laws between structural dimensions and actuator amplification ratios, and the dynamic model represents the relationship between the control signals and move displacements, thus demonstrating the feasibility of the actuator. Finally, a prototype was fabricated, and a testing system was set up to conduct performance evaluations of its motion capabilities. At the driving frequencies of 370 Hz and 380 Hz, the maximum forward and reverse motion speeds can reach 4.345mm/s and 4.537mm/s, respectively. In the range of 0.1-10N, there is no significant change in motion speed, and it has good stability. Its resolution for forward and reverse motion can reach 106nm and 109nm, respectively.

A Review on Cushioning Characteristics in High-Speed Hydraulic Actuators

Abstract High speed actuators are an integral part of the fluid power driven systems and cylinder cushioning requirement in these actuators is one of the important aspects. Cushioning is imperative in any high-speed actuator as it not only increases its life but also gives operating comfort to the operator. Fluid power driven systems are very common in many defence and industrial applications due to their high force/torque and power density. This review paper brings out the available literature in the field of hydraulic cylinder cushioning. Literature, consisting mainly of journal articles, research papers and other media contents is analysed for the key parameters of research in this field. The classification of cushioning methodology by different researchers is projected. The methodologies of modelling and simulation work carried out by various authors are analysed. Thereafter the optimization studies done for the cushion piston design in various literature are discussed. Lastly, experimental validation strategies as employed in certain papers are also brought out. Experimental study, and validation of non-conventional cushioning methodology is discussed, which is not much evidenced in the literature.

Hexagonal electrohydraulic modules for rapidly reconfigurable high-speed robots.

Robots made from reconfigurable modular units feature versatility, cost efficiency, and improved sustainability compared with fixed designs. Reconfigurable modules driven by soft actuators provide adaptable actuation, safe interaction, and wide design freedom, but existing soft modules would benefit from high-speed and high-strain actuation, as well as driving methods well-suited to untethered operation. Here, we introduce a class of electrically actuated robotic modules that provide high-speed (a peak contractile strain rate of 4618% per second, 15.8-hertz bandwidth, and a peak specific power of 122 watts per kilogram), high-strain (49% contraction) actuation and that use magnets for reversible mechanical and electrical connections between neighboring modules, thereby serving as building blocks for rapidly reconfigurable and highly agile robotic systems. The actuation performance of each hexagonal electrohydraulic (HEXEL) module is enabled by a synergistic combination of soft and rigid components; a hexagonal exoskeleton of rigid plates amplifies the motion produced by soft electrohydraulic actuators and provides a mechanical structure and connection platform for reconfigurable robots composed of many modules. We characterize the actuation performance of individual HEXEL modules, present a model that captures their quasi-static force-stroke behavior, and demonstrate both a high-jumping and a fast pipe-crawling robot. Using embedded magnetic connections, we arranged multiple modules into reconfigurable robots with diverse functionality, including a high-stroke muscle, a multimodal active array, a table-top active platform, and a fast-rolling robot. We further leveraged the magnetic connections for hosting untethered, snap-on driving electronics, together highlighting the promise of HEXEL modules for creating rapidly reconfigurable high-speed robots.

Development of Ni-Mn-Ga Enabled Micropumps for Hybrid Microdevices in Microelectromechanical Systems

This study selects a single crystalline Ni-Mn-Ga alloy by its exceptional actuator attributes, high actuation speed, precise position control, rapid response to external magnetic fields, and extended operational lifespan. Researchers venture into uncharted territory, aiming to harness the potential of Ni-Mn-Ga alloy to revolutionize micropump performance and refine fluid manipulation within miniature devices. The methodology at the heart of this endeavor involves the seamless integration of this specialized alloy with microdevice technology, giving rise to a set of unique pump components that substantially boost pump efficiency. Crucially, Ni-Mn-Ga is the chosen material for the active part of the micropump. At the same time, MEMS fabrication handles the passive elements, all facilitated by the 0.18 µm semiconductor technology and Sivalco TCAD simulation software. Computational simulations validate the alloy's suitability, impressively achieving an accumulated flow volume of 0.15 x 10e-4 µL in 10 microseconds. Beyond its scientific significance, this research bridges MEMS technology and magnetic-enabled smart materials, showcasing the remarkable capabilities of Ni-Mn-Ga alloy in significantly enhancing micropump performance. These innovative solutions promise to open doors to groundbreaking applications in microfluidic systems across many scientific and industrial domains.

Multistable States and Snap-Through Instabilities in an Interconnected Dielectric Elastomer Actuators System

Abstract Snap-through instabilities in single and interconnected dielectric elastomer actuators have demonstrated their potential in enabling many functionalities such as large deformation, high-speed actuation, and enhanced flowrates in fluid pumps. However, the nonlinear nature of dielectric elastomers and the complex interplay of mechanics in interconnected inflated actuators, make the modeling of such systems challenging. In this paper, we present a methodology to analytically model the instabilities in a system of three interconnected homogeneous spherical dielectric elastomer actuators through graphical and numerical approaches. The simulation results reveal the presence of a locus of initial stable states that the interconnected actuators can achieve at zero voltage. In specific loading conditions, the system exhibits multiple stable states which can be cyclically transitioned between by selectively applying voltage to specific actuators. In other conditions, the system may undergo two successive instabilities when the voltage applied to a single actuator in the system is increased monotonically. These results retrieve existing experimental results theoretically for the first time and identify a new behavior of cascading instabilities in inflated dielectric elastomer actuators. We hope this work will pave the way for programmable design of multistable systems to unravel new capabilities in dielectric elastomer actuators and soft robotics.

Experiments and study of a low-frequency, high-speed bi-directional piezoelectric stick-slip actuator

Experiments and study of a low-frequency, high-speed bi-directional piezoelectric stick-slip actuator

Experimental characterization of a modified high-speed plasma synthetic jet actuator with oblique-slot exit

In the field of flow control research, oblique jets are known to offer several advantages over vertical jets. To gain a comprehensive insight into the flow field characteristics of a plasma synthetic jet actuator with an oblique-slot exit, the related experiments are conducted. The experiment employed high-speed schlieren imaging techniques and electrical parameter measurements to acquire the flow field characteristics and discharge properties of the oblique-slot actuator, followed by a comparative analysis with a vertical circular orifice actuator. The oblique-slot plasma synthetic jet exhibits a wall-attaching effect and asymmetric flow characteristics, which differ from those of the vertical circular orifice actuator. The actuator generates a wall jet with an initial velocity of 389.5 ± 15.08 m/s, effectively propelling the fluid within the boundary layer. The Mach number of the precursor shock wave in the direction of the jet reaches 1.59, but decreases to just 1.02 in the opposite direction. Over a period in the range of 10–70 μs, the Froude number of the plasma jet decreases from 1841 to 238. The dominant role of the inertial force gradually weakens, while the influence of buoyancy increases, causing the jet boundary to move upward. The oblique-slot jet configuration represents a typical planar jet, exhibiting superior flow control uniformity compared with the vertical circular orifice jet. The results indicate that the high-speed oblique-slot plasma synthetic jet actuator designed in this study possesses distinct advantages over vertical circular orifice actuators for high-speed fluid flow control.

Self-protection soft fluidic robots with rapid large-area self-healing capabilities

Soft fluidic robots have attracted a lot of attention and have broad application prospects. However, poor fluidic power source and easy to damage have been hindering their development, while the lack of intelligent self-protection also brings inconvenience to their applications. Here, we design diversified self-protection soft fluidic robots that integrate soft electrohydrodynamic pumps, actuators, healing electrofluids, and E-skins. We develop high-performance soft electrohydrodynamic pumps, enabling high-speed actuation and large deformation of untethered soft fluidic robots. A healing electrofluid that can form a self-healed film with excellent stretchability and strong adhesion is synthesized, which can achieve rapid and large-areas-damage self-healing of soft materials. We propose multi-functional E-skins to endow robots intelligence, making robots realize a series of self-protection behaviors. Moreover, our robots allow their functionality to be enhanced by the combination of electrodes or actuators. This design strategy enables soft fluidic robots to achieve their high-speed actuation and intelligent self-protection, opening a door for soft robots with physical intelligence.

Soft Robotic Finger with Energy-Coupled Quadrastability.

The performance of the human finger is a significant inspiration for designing soft robotic fingers that can achieve high speed and high force or perform delicate and complex tasks. Existing soft grippers and actuators can be excellent in specific capabilities. However, it is still challenging for them to meet an all-around performance as the human finger, characterized by high actuation speed, wide grasping range, sensing ability, and gentle and high-load grasping capability. The proposed tendon pulley quadrastable (TPQ) finger has combined these qualities in the conducted gripping tasks. A pair of elastic tendons is utilized as the sole energy reservoir to create a novel energy distribution pattern: energy-coupled quadrastability. An energy model is built to analyze and predict the behaviors of the TPQ finger. Mechanical instability is utilized to enhance the actuation speed. The proposed soft lever mechanism endows the TPQ finger with sensing ability. The energy barrier adjusting plates control the energy barrier, adjusting the sensitivity of both active and passive actuation mechanisms. The transition of four stable states forms preplanned trajectories that are applied to create multiple grasping manners. Experiments show that it can respond to stimuli and finish a grasping task in merely 31 ms, and its payload can reach 33.25 kg. At the same time, it can also handle fragile objects such as a piece of rose and grasp a wide range of objects ranging from a thin nut (3.3 mm in height) or a thin card (0.76 mm thick) to a football (220 mm).

High-speed and high-efficient actuation of molecular crystals by photothermally induced natural vibration

High-speed and high-efficient actuation of molecular crystals by photothermally induced natural vibration

A multifunctional soft robotic shape display with high-speed actuation, sensing, and control

Shape displays which actively manipulate surface geometry are an expanding robotics domain with applications to haptics, manufacturing, aerodynamics, and more. However, existing displays often lack high-fidelity shape morphing, high-speed deformation, and embedded state sensing, limiting their potential uses. Here, we demonstrate a multifunctional soft shape display driven by a 10 × 10 array of scalable cellular units which combine high-speed electrohydraulic soft actuation, magnetic-based sensing, and control circuitry. We report high-performance reversible shape morphing up to 50 Hz, sensing of surface deformations with 0.1 mm sensitivity and external forces with 50 mN sensitivity in each cell, which we demonstrate across a multitude of applications including user interaction, image display, sensing of object mass, and dynamic manipulation of solids and liquids. This work showcases the rich multifunctionality and high-performance capabilities that arise from tightly-integrating large numbers of electrohydraulic actuators, soft sensors, and controllers at a previously undemonstrated scale in soft robotics.

Fundamental Investigations of the Deformation Behavior of Single-Crystal Ni-Mn-Ga Alloys and Their Polymer Composites via the Introduction of Various Fields

To meet the great requirements of future technologies, such as robots, single-crystal (SC) Ni-Mn-Ga alloys and their composites were designed and investigated in this study. Ferromagnetic shape memory alloys (FSMAs) are promising materials for applications in high-speed actuators, which are core components of robots; however, there are some issues of embrittlement and small deformation strain. Therefore, in this work, we first prepared SC Ni-Mn-Ga alloys for fundamental investigations of the shape deformations under the application of different fields (e.g., compressive and magnetic fields). Second, the SC Ni-Mn-Ga alloys were integrated with polymers of epoxy resin or silicone rubber to solve the embrittlement problem. The obvious two-stage yielding and sudden intensifying of the magnetization both suggest martensite variant reorientation (MVR) under the compressive and magnetic fields, respectively. Micro-computed tomography (μCT) and an X-ray diffractometer were utilized for the observations of shape deformation brought about by the MVR of the SC Ni-Mn-Ga particles in the polymer matrix. Clear MVR and shape deformation could be found in the compressed composites.

Factors in deformation capacity loss of bolts under singular and consecutive impacts

For structures subjected to extreme loading, such as a blast or impact, the plastic deformation of structural connections is vital to life safety. Despite its importance, a loss of deformation capacity in connections via fracture of bolts has been repeatedly noted experimentally and in situ. To further investigate the dynamic fracture of bolts, this work subjects A325 structural bolts in single shear to impulsive loads using a high-speed hydraulic actuator. This is the first study to report strength and deformation performance for structural bolts fractured via singular and consecutive impacts. Further, this work is the first investigation into the root cause of the deformation capacity loss that has historically coincided with shear bolt fracture. Previous split Hopkinson pressure bar experimentation suggests that rate-induced changes in strain hardening contribute to, but do not fully explain, the loss of deformation capacity in high-strength bolts. Further investigation with scanning electron microscopy suggests that loss of deformation capacity is also due to a rate-induced change in failure mechanism, adiabatic shear banding. These findings impact our understanding of connections that fail via dynamic bolt fracture – behavior changes on the macroscale are the result of underlying rate-dependent fracture mechanisms.

Dynamic performance of a membrane-based variable focus lens with a large aperture.

Dynamic performance is one of the most important characteristics of a variable focus lens. However, there are few studies investigating the dynamic response of a membrane-based variable focus lens. In this paper, we present a mathematical model to describe spring-damping phenomena in theory. The first order natural frequencies with different scales were confirmed via finite element analysis. We also built a dynamic response experiment platform with changeable optical apertures, which was driven by a high-speed piezo stack actuator. A photodiode module was placed behind the lens to measure the variation of light luminance as the lens changed, and a laser displacement sensor was used to measure the deformation of the membrane. A series of data was collected with different optical apertures (20mm, 30mm, 50mm) and different pre-stretching ratios (200%, 300%) under different driving frequencies (from 5Hz to 25Hz in every 5Hz step). The experimental results were consistent with the mathematical model, which showed that the first order natural frequency increased as the aperture decreased or the membrane stiffness increased. This frequency-dependent characteristic of the variable focus lens provides a basis for further research on its dynamic performance.

Development of an Instantaneous Loading Impact Test System for Containment of a Nuclear Power Plant during Aircraft Impact on Steel Bar Joints.

As major projects such as nuclear power plants continuously increase, it is inevitable that loopholes will arise in safety precautions. Airplane anchoring structures, comprising steel joints and acting as a key component of such a major project, directly affect the safety of the project due to their resistance to the instant impact of an airplane. Existing impact testing machines have the limitations of being unable to balance impact velocity and impact force, as well as having inadequate control of impact velocity; they cannot meet the requirements of impact testing for steel mechanical connections in nuclear power plants. This paper discusses the hydraulic-based principle of the impact test system, adopts the hydraulic control mode, and uses the accumulator as the power source to develop an instant loading test system suitable for the entire series of steel joints and small-scale cable impact tests. The system is equipped with a 2000 kN static-pressure-supported high-speed servo linear actuator, a 2 × 22 kW oil pump motor group, a 2.2 kW high-pressure oil pump motor group, and a 9000 L/min nitrogen-charging accumulator group, which can test the impact of large-tonnage instant tensile loading. The maximum impact force of the system is 2000 kN, and the maximum impact rate is 1.5 m/s. Through the impact testing of mechanical connecting components using the developed impact test system, it was found that the strain rate of the specimen before failure was not less than 1 s-1, meeting the requirements of the technical specifications for nuclear power plants. By adjusting the working pressure of the accumulator group, the impact rate could be controlled effectively, thus providing a strong experimental platform for research in the field of engineering for preventing emergencies.

Investigations of the Crystallographic Orientation on the Martensite Variant Reorientation of the Single-Crystal Ni-Mn-Ga Cube and Its Composites for Actuator Applications

High-speed actuators are greatly required in this decade due to the fast development of future technologies, such as Internet-of-Things (IoT) and robots. The ferromagnetic shape memory alloys (FSMAs), whose shape change could be driven by applying an external magnetic field, possess a rapid response. Hence, these materials are considered promising candidates for the applications of future technologies. Among the FSMAs, the Ni-Mn-Ga-based materials were chosen for their large shape deformation strain and appropriate phase transformation temperatures for near-room temperature applications. Nevertheless, it is widely known that both the intrinsic brittleness of the Ni-Mn-Ga alloy and the constraint of shape deformation strain due to the existence of grain boundaries in the polycrystal inhibit the applications. Therefore, various Ni-Mn-Ga-based composite materials were designed in this study, and their shape deformation behaviors induced by compressive or magnetic fields were examined by the in situ micro CT observations. In addition, the dependence of the martensite variant reorientation (MVR) on the crystallographic directions was also investigated. It was found that most of the MVRs are active within the magnetic field range applied in the regime of the <100>p, <110>p, and <111>p of the single-crystal {100}p Ni-Mn-Ga cubes.

On-Chip Self-Sensing Piezoelectric Micro-Lens Actuator With Feedback Control

High-speed micro-lens actuators are required for fast auto-focusing in miniaturized cameras. The speed can be enhanced by adding damping at the resonance frequency through feedback control. Previous approaches to implement the feedback control were based on expensive off-chip bulky laser sensors that are not suitable for miniaturized cameras. In this paper, using an on-chip self-sensing piezoelectric sensor with a novel readout circuit, a passive resonant controller is designed, implemented, and tested. The stability of the closed-loop micro-lens actuator is guaranteed through the use of mixed negative-imaginary and passivity theory in the controller design. The performance of the controller with the on-chip self-sensing piezoelectric sensor and readout circuit is compared to that off-chip laser sensor, and results show comparable performance. The closed-loop micro-lens actuator with the on-chip piezoelectric sensor damps the fundamental resonance mode by 20.6 dB, which is similar to the 21.9 dB reduction obtained using the off-chip laser sensor. The settling time for the closed-loop actuator using the on-chip self-sensing piezoelectric sensor is less than 10 ms, which is also comparable to the 8 ms obtained with the off-chip laser sensor. The signal-to-noise ratios for the on-chip self-sensing piezoelectric sensor and off-chip laser sensor are 108 dB and 118 dB, respectively. These results show that the piezoelectric micro-lens actuator using the on-chip self-sensing piezoelectric sensor can replace the bulky and expensive off-chip laser sensor without sacrificing performance, making it more appealing for portable micro-optics devices.

Four-Dimensional Printing of Temperature-Responsive Liquid Crystal Elastomers with Programmable Shape-Changing Behavior.

Liquid crystal elastomers (LCEs) are polymer networks that exhibit anisotropic liquid crystalline properties while maintaining the properties of elastomers, presenting reversible high-speed and large-scale actuation in response to external stimuli. Herein, we formulated a non-toxic, low-temperature liquid crystal (LC) ink for temperature-controlled direct ink writing 3D printing. The rheological properties of the LC ink were verified under different temperatures given the phase transition temperature of 63 °C measured by the DSC test. Afterwards, the effects of printing speed, printing temperature, and actuation temperature on the actuation strain of printed LCEs structures were investigated within adjustable ranges. In addition, it was demonstrated that the printing direction can modulate the LCEs to exhibit different actuation behaviors. Finally, by sequentially conforming structures and programming the printing parameters, it showed the deformation behavior of a variety of complex structures. By integrating with 4D printing and digital device architectures, this unique reversible deformation property will help LCEs presented here apply to mechanical actuators, smart surfaces, micro-robots, etc.

Ultra-High-Throughput and Low-Volume Analysis of Intact Proteins with LAP-MALDI MS.

High-throughput (HTP) mass spectrometry (MS) is a rapidly growing field, with many techniques evolving to accommodate ever increasing sample analysis rates. Many of these techniques, such as AEMS and IR-MALDESI MS, require volumes of at least 20-50 μL for analysis. Here, liquid atmospheric pressure-matrix-assisted laser desorption/ionization (LAP-MALDI) MS is presented as an alternative for ultra-high-throughput analysis of proteins requiring only femtomole quantities of protein in 0.5 μL droplets. By moving a 384-well microtiter sample plate with a high-speed XY-stage actuator, sample acquisition rates of up to 10 samples per second have been achieved at a data acquisition rate of 200 spectra per scan. It is shown that protein mixture solutions with concentrations of ≤2 μM can be analyzed at this speed, while individual protein solutions can be analyzed at concentrations of ≤0.2 μM. Thus, LAP-MALDI MS provides a promising platform for multiplexed HTP protein analysis.

Photothermally induced natural vibration for versatile and high-speed actuation of crystals

The flourishing field of soft robotics requires versatile actuation methodology. Natural vibration is a physical phenomenon that can occur in any material. Here, we report high-speed bending of anisole crystals by natural vibration induced by the photothermal effect. Rod-shaped crystal cantilevers undergo small, fast repetitive bending (~0.2°) due to natural vibration accompanied by large photothermal bending (~1°) under ultraviolet light irradiation. The natural vibration is greatly amplified by resonance upon pulsed light irradiation at the natural frequency to realise high frequency (~700 Hz), large bending (~4°), and high energy conversion efficiency from light to mechanical energy. The natural vibration is induced by the thermal load generated by the temperature gradient in the crystal due to the photothermal effect. The bending behaviour is successfully simulated using finite element analysis. Any light-absorbing crystal can be actuated by photothermally induced natural vibration. This finding of versatile crystal actuation can lead to the development of soft robots with high-speed and high-efficient actuation capabilities.