Actuation Speed Research Articles

Large Stepwise Discrete Microsystem Displacements Based on Electrostatic Bending Plate Actuation

We present the design, fabrication, and experimental characterization of microsystems achieving large and stepwise discrete displacements. The systems consist of electrostatic bending plate actuators linked in a chain with increasing electrode gaps to allow a stepwise system displacement. A derived analytic transfer function permits to evaluate the influence of the system components on both the total and the stepwise system displacement. Based on calculation and simulation results, systems featuring 5, 8, 10, 13, and 16 steps are modeled and fabricated using a dicing-free SOI-fabrication process. During experimental voltage- and time-dependent system characterization, the minimum switching speed of the electrostatic actuators is 1 ms. Based on the guiding spring stiffness and the switching time, step-by-step and collective activations of the microsystems are performed and the system properties are derived. Furthermore, we analyze the influence of the number of steps on the total system displacement and present 16-step systems with a total maximum displacement of 230.7 ± 0.9 µm at 54 V.

Considerations and complications with "first principles" dynamic modelling of industrial compressors

Readily available processing hardware and "off-the-shelf" (OTS) simulation software has made "high fidelity" first principles models of both steady and transient states, for both axial and centrifugal industrial compressors, relatively easy to construct. These high-fidelity models are finding their way into "real-time. digital twin" performance monitors, front-end engineering design, and post-design – pre-construction compressor performance evaluation. The compressor models are useful for reliably demonstrating the compressor and – to some degree, based on the complexity of the model – process response to various operating conditions. Once the model is constructed, it is trivial to run a "what-if" analysis of compressor performance to answer questions related to (a) recommendations or validation of the recycle/vent valve size and actuation speed, (b) general piping layout and sizing around the compressor, (c) and hot gas bypass requirements, to name a few. This paper takes a practical approach in discussing the compressor and process parameters necessary for building these dynamic "high-fidelity" industrial-compressor models. We identify compressor inputs and compressor responses that are faithfully modeled by first-principle equations available in the simulation software and those that typically require a compromise between an "ab initio" and data-fitting approximation. We discuss the simulation's tendency to overstate pressure excursions during surge events and understate the compressor operation in the "stonewall" region. We also discuss using the simulator software's compressor-stage enthalpy calculations to predict and quantify the compressor train reverse rotation. We use our broad experience and understanding of the compressor operation and simulation and our experience with the AVEVA™ Dynamic-Simulation "OTS" simulation software as the basis for this discussion.

In-situ polymerization for mechanical strong composite actuators based on anisotropic wood and thermoresponsive polymer

Stimuli-responsive hydrogels hold an irreplaceable statue in intelligent actuation materials because of their reversible stretchability and excellent biocompatibility. However, the poor mechanical performance and complicated fabrication process of anisotropic structures severely limit their further applications. Herein, we report a high-strength thermoresponsive wood-PNIPAM composite hydrogel actuator with complex deformations, through a simple in-situ polymerization. In this composite hydrogel actuator, the anisotropic wood and the thermoresponsive PNIPAM hydrogel hydroel can work together to provide bending and even other complex deformations. Owing to strong interfacial interaction, this actuator perfectly realized the combination of good mechanical properties (∼1.1 MPa) and fast actuation speed (∼0.9 s). In addition, by adjusting the orientation direction of wood, this actuator can achieve various complex deformations. Such composite hydrogel actuator could be a good candidate for intelligent applications, such as intelligent actuators, smart valves, manipulators and even soft robots.

Poly (vinyl alcohol) based gradient cross-linked and reprogrammable humidity-responsive actuators

Actuators are a kind of energy-conversion devices which can perceive external stimulus and undergo reversible deformation or motion to produce a mechanical response. Developing actuators with advanced structures rather than typical bilayer configuration is essential for stable actuations, and installing reprogrammability into actuators for on-demand complex shape transformation within the same piece of material is more convenient and cost-effective for new actuation modes. However, actuators that satisfy these requirements have rarely been reported yet. Herein, a facile and low-cost design strategy for a transparent, gradient cross-linked, patternable and reprogrammable humidity-responsive actuator based on commercial available poly (vinyl alcohol) (PVA) is presented. The actuator is fabricated by grafting PVA with 9-anthracenecarboxylic acid (9-AN) via esterification and then blending with a UV-screening agent 2,2′,4,4′-tetrahydroxybenzophenone (THBP) followed by photo-crosslinking. In such design, the abundant hydroxyl groups in grafted PVA endow the actuator with humidity-responsive ability, the THBP enables the gradient cross-linking of actuator due to the attenuated UV intensity through the film thickness, and the photo-controlled reversible cross-linking of anthracene groups allows the patterning and reprogramming of the actuator. The chemical structure, gradient morphology, and humidity-responsiveness of actuators are thoroughly investigated. The fast actuation speed and large actuation amplitude, the realization of complex shape deformation by photo-controlled programming/reprogramming, and the biomimetic applications such as the soft walking robot are also demonstrated. This study is expected to provide new opportunity for facilely developing high-performance, stable and reprogrammable actuators.

Atomization Control to Improve Soft Actuation Through Vaporization.

Soft actuation through droplet evaporation has significantly improved the actuation speed of methods that utilize liquid vaporization. Instead of boiling bulk liquid, this method implements atomization to disperse small droplets into a heater. Due to the large surface area of the droplets, the liquid evaporates much faster even at small temperature changes. However, further analysis is required to maximize the performance of this complex multi-physics method. This study was conducted to provide further insight into the atomizer and how it affects actuation. Numerical simulations were used to inspect the vibration modes and determine how frequency and voltage affect the atomization process. These results were used to experimentally control the atomizer, and the droplet growth on the heater surface was analyzed to study the evaporation process. A cuboid structure was inflated with the actuator to demonstrate its performance. The results show that simply maximizing the atomization rate creates large droplets on the surface of the heater, which slows down the vaporization process. Thus, an optimal atomization rate should be determined for ideal performance.

Regulatory Control of Mass Flowrate in an Ore Feeding System with Time-Delayed Gain-Variant Dynamics

Brazil is the world leading producer and exporter of iron ore, mainly due to operations of VALE, a global mining company with several operations in the country, delivering iron, copper, manganese, and nickel ores. Those operations are located mainly in the Northern state of Pará, and in the Southeastern state of Minas Gerais. From 2014 to 2019, the company’s average yearly production of iron ore was about 342 million t/year. Most of such production was exported overseas, mainly to Asian and European countries.Mineral processing plants implement several stages of ore beneficiation, necessary to convert raw ore from the mines into ore products. Those plants comprise several processing facilities as crushing, screening, grinding, flotation, and others, which are operated by means of a plantwide digital control system, either SCADA- or DCS-based, using many process control loops.The most important process variable in a mineral processing plant is the ore mass flowrate, measured in t/h. The transportation of ore between mineral facilities is usually done by belt conveyors, and the ore flowrate is measured by a conveyor weigher (also known as dynamic weigher or belt scale), which is a heavy instrument assembled directly in the conveyor structure [18]. The conveyor weigher has two primary sensors: piezoelectric loading cells to sense the unit weight of material on the belt, in t/m; and an incremental encoder to sense the belt moving speed, in m/s. By combining the unity load and the belt speed measurements, the weigher computes the material flowrate, in t/h, with a typical precision of ±0.5% of its full measurement range. The ore flowrate in a conveyor is not defined by the belt speed, but by the speed of the feeder that discharges the ore on the conveyor belt. Therefore, by changing the feeder (actuator) speed it is possible to control the ore flowrate using its measurements provided by the conveyor weigher (sensor).This work describes the modeling and control of ore flowrate for the ore feeding system “RF-A” of the Fábrica Iron Ore Processing Plant, in the city of Ouro Preto, Minas Gerais state, Brazil, operated by VALE. The next section introduces the industrial process and the control problem.

Highly Efficient Uniaxial In-Plane Stretching of a 2D Material via Ion Insertion.

On-chip dynamic strain engineering requires efficient micro-actuators that can generate large in-plane strains. Inorganic electrochemical actuators are unique in that they are driven by low voltages (≈1V) and produce considerable strains (≈1%). However, actuation speed and efficiency are limited by mass transport of ions. Minimizing the number of ions required to actuate is thus key to enabling useful "straintronic" devices. Here, it is shown that the electrochemical intercalation of exceptionally few lithium ions into WTe2 causes large anisotropic in-plane strain: 5% in one in-plane direction and 0.1% in the other. This efficient stretching of the 2D WTe2 layers contrasts to intercalation-induced strains in related materials which are predominantly in the out-of-plane direction. The unusual actuation of Lix WTe2 is linked to the formation of a newly discovered crystallographic phase, referred to as Td', with an exotic atomic arrangement. On-chip low-voltage (<0.2V) control is demonstrated over the transition to the novel phase and its composition. Within the Td'-Li0.5- δ WTe2 phase, a uniaxial in-plane strain of 1.4% is achieved with a change of δ of only 0.075. This makes the in-plane chemical expansion coefficient of Td'-Li0.5-δ WTe2 far greater than of any other single-phase material, enabling fast and efficient planar electrochemical actuation.

Design and Implementation of Line Follower Arduino Mobile Robot Using Matlab Simulink Toolbox

The main problem of line follower robot is how to make the mobile robot follows a desired path (which is a line drawn on the floor) smoothly and accurately in shortest time. In this paper, the design and implementation of a complex line follower mission is presented by using Matlab Simulink toolbox. The motion of mobile robot on the complex path is simulated by using the Robot Simulator which is programed in Matlab to design and test the performance of the proposed line follower algorithm and the designed PID controller. Due to the complexity of selection the parameters of PID controller, the Particle Swarm Optimization (PSO) algorithm are used to select and tune the parameters of designed PID controller. Five Infrared Ray (IR) sensors are used to collect the information about the location of mobile robot with respect to the desired path (black line). Depending on the collected information, the steering angle of the mobile robot will be controlled to maintain the robot on the desired path by controlling the speed of actuators (two DC motors). The obtained simulation results show that, the motion of mobile robot is still stable even the complex maneuver is performed. The hardware design of the robot system is perform by using the Arduino Mobile Robot (AMR). The Simulink Support Package for Arduino and control system toolbox are used to program the AMR. The practical results show that the performances of real mobile robot are exactly the same of the performances of simulated mobile robot.

Design and Control of Pneumatic Systems for Soft Robotics: A Simulation Approach

Pressure control plays a major role in the overall performance of fluid-driven soft robots. Due to the increasing demand for higher speed actuation and precision, a need exists for a practical design methodology that converts actuator performance specifications to a set of minimum pneumatic specifications, such as receiver volume and pressure, and valve conductance. This article presents a systematic parameter selection approach for pneumatic soft robotic systems by taking into consideration the desired closed-loop pressure responses. The two controllers under evaluation here are the PI controller with anti-windup and the on-off controller with hysteresis. Simulations are developed within Simscape Fluids to evaluate the effect of physical components and controller parameters on the actuator performance. The proposed parameter selection procedures are then applied on three soft actuators and their closed-loop pressure responses are experimentally evaluated. The measured pressure responses are in close agreement with the simulations and satisfy the rise time specifications.

Photothermally Driven High-Speed Crystal Actuation and Its Simulation.

Mechanically responsive crystals have been increasingly explored, mainly based on photoisomerization. However, photoisomerization has some disadvantages for crystal actuation, such as a slow actuation speed, no actuation of thick crystals, and a narrow wavelength range. Here we report photothermally driven fast-bending actuation and simulation of a salicylideneaniline derivative crystal with an o-amino substituent in enol form. Under ultraviolet (UV) light irradiation, these thin (<20 μm) crystals bent but the thick (>40 μm) crystals did not due to photoisomerization; in contrast, thick crystals bent very quickly (in several milliseconds) due to the photothermal effect, even by visible light. Finally, 500 Hz high-frequency bending was achieved by pulsed UV laser irradiation. The generated photothermal energy was estimated based on the photodynamics using femtosecond transient absorption. Photothermal bending is caused by a nonsteady temperature gradient in the thickness direction due to the heat conduction of photothermal energy generated near the crystal surface. The temperature gradient was calculated based on the one-dimensional nonsteady heat conduction equation to simulate photothermally driven crystal bending successfully. Most crystals that absorb light have their own photothermal effects. It is expected that the creation and design of actuation of almost all crystals will be possible via the photothermal effect, which cannot be realized by photoisomerization, and the potential and versatility of crystals as actuation materials will expand in the near future.

Two-Dimensional Nanosheets-Based Soft Electro-Chemo-Mechanical Actuators: Recent Advances in Design, Construction, and Applications.

Soft electro-chemo-mechanical actuators have received enormous interest in biomimetic technologies, wearable electronics, and microelectromechanical systems due to their low voltage-driven large deformation, fast response, high strain, and working durability. Two-dimensional (2D) nanosheets, which can highly promote ion-induced micromotion to macrodeformation, have outstandingly been used as prime actuator electrodes because of their ordered microstructures, tunable interlayer spaces, controllable electrochemical activities, and excellent electrical and mechanical properties. Here, this review primarily focuses on the recent advances in key 2D electro-chemo-mechanical actuator electrodes, including graphene, MXenes, graphitic carbon nitride, molybdenum disulfide, black phosphorus, and graphdiyne. Various synthetic strategies of electrode design, such as microstructural architecture, active-site regulation, and channel construction, for achieving high ionic kinetic transport, charge storage, and electrochemical-mechanical performances are discussed. The advanced structures with diverse building principles that provide ordered and active ionic pathways for high actuation speed and strain are emphasized. Furthermore, the innovative applications of electro-chemo-mechanical actuators toward biomimetic robots and smart devices are highlighted. Finally, the current challenges and future perspectives are also proposed. The aim of this review is to provide the guiding significance for scientific researchers and industrial engineers to design higher performance next-generation electro-chemo-mechanical actuators.

Improvement in Performance of the Sulphuric Acid Transport Installation through Modification of Flow Characteristics Using Electric Actuators

The paper presents a flow model of the installation for tank car filling with sulphuric acid (VI). For the mathematical modelling of the flow process in the industrial installation, a model diagram of the object and experiments carried out during the installation work were applied. The analysis of specific experimental series showed unusual shapes of mass flow characteristics vs. the valve opening level (too wide hysteresis), which markedly deviated from typical flow characteristics that are found in standards and literature. As a result of flow modelling in the sulphuric acid installation, a better-shaped characteristic was presented that should be obtained based on the measuring system values in the absence of the inertia-related error. In the experiments carried out according to the selected procedures, effects of the actuator speed on the characteristics of interest were determined. It was observed that the use of a “slower” actuator (i.e., longer transition time) narrows the characteristics in terms of a reduced difference in flow readings between the valve opening and closing courses. In the specified research procedure for the real flow characteristics, effects of the measurement transducer dynamics in the flow meter on the characteristic course were assessed. It was demonstrated that a faster transducer enabled closer flow recordings to the valve nominal characteristics. The variable speed can improve the positioning precision, with the use of the lowest possible speed rule directly before the positioning point.

Optimization of Phase-Change Material-Elastomer Composite and Integration in Kirigami-Inspired Voxel-Based Actuators.

Phase-change material–elastomer composite (PCMEC) actuators are composed of a soft elastomer matrix embedding a phase-change fluid, typically ethanol, in microbubbles. When increasing the temperature, the phase change in each bubble induces a macroscopic expansion of the matrix. This class of actuators is promising for soft robotic applications because of their high energy density and actuation strain, and their low cost and easy manufacturing. However, several limitations must be addressed, such as the high actuation temperature and slow actuation speed. Moreover, the lack of a consistent design approach limits the possibility to build PCMEC-based soft robots able to achieve complex tasks. In this work, a new approach to manufacture PCMEC actuators with different fluid–elastomer combinations without altering the quality of the samples is proposed. The influence of the phase-change fluid and the elastomer on free elongation and bending is investigated. We demonstrate that choosing an appropriate fluid increases the actuation strain and speed, and decreases the actuation temperature compared with ethanol, allowing PCMECs to be used in close contact with the human body. Similarly, by using different elastomer materials, the actuator stiffness can be modified, and the experimental results showed that the curvature is roughly proportional to the inverse of Young’s modulus of the pure matrix. To demonstrate the potential of the optimized PCMECs, a kirigami-inspired voxel-based design approach is proposed. PCMEC cubes are molded and reinforced externally by paper. Cuts in the paper induce anisotropy into the structure. Elementary voxels deforming according to the basic kinematics (bending, torsion, elongation, compression and shear) are presented. The combination of these voxels into modular and reconfigurable structures could open new possibilities towards the design of flexible robots able to perform complex tasks.

Shape Memory Alloy Capsule Micropump for Drug Delivery Applications.

We introduce a shape memory alloy (SMA) actuated micropump optimized for drug delivery applications. The proposed novel design integrates a built-in replaceable drug reservoir within the pump package forming a self-contained preloaded capsule pump with an overall pump volume of 424.7 μL. The new design results in a compact, simple, and inexpensive micropump and reduces the probability of contamination with attained almost zero dead volume values. The pump consists of NiTi-alloy SMA wires coiled on a flexible polymeric enclosure and actuated by joule heating. Unlike diaphragm and peristaltic SMA micropump designs that actuate transversely, our design is actuated longitudinally along the direction of the highest mechanical compliance resulting in large strokes in the order of 5.6 mm at 27% deflection ratio, actuation speed up to 11 mm/s, and static head pressures up to 14 kPa (105 mmHg) at 7.1 W input power; thus, high throughputs exceeding 2524 μL/min under free convention conditions could be achieved. A model was developed to optimize the pump’s geometrical parameters and the enclosure material. The model concluded that low stiffness enclosure material combined with thinner SMA wire diameter would result in the maximum deflection at the lowest power rating. To prove its viability for drug delivery applications, the pump was operated at a constant discharge volume at a relatively constant static head pressure. Furthermore, a design of bicuspid-inspired polymeric check-valves is presented and integrated onto the pump to regulate the flow. Since the built-in reservoir is replaceable, the pump capsule can be reused multiple times and for multiple drug types.

High-speed giant magnetostrictive actuator using laminated silicon steel core.

The high-frequency eddy current loss limits the output speed of the giant magnetostrictive actuator (GMA). This paper investigates a GMA using a laminated silicon steel core. Compared with the integral silicon steel core, the laminated silicon steel core can reduce the equivalent conductivity and eddy currents. The laminated structure reduces the magnetic reluctance of the core and increases the magnetic field intensity in the giant magnetostrictive material rod. Therefore, the actuator can output large vibration amplitude under high-frequency magnetic field. At the sinusoidal excitation current of 35A (rms) @ 2 kHz, the output vibration amplitude of the actuator using the laminated silicon steel core is 11.1 µm @ 4 kHz, which is 44.2% higher than that of the actuator with the integral silicon steel core. This indicates that the laminated structure of the magnetic core is beneficial to improve the output speed of GMA.

PID Controllers with a Constant Speed Actuator: Implementation Versions and Self-Tuning of Pulse Duration

The article considers three implementation versions of controllers operating with constant speed actuators that are used in automation systems of a technological process: with a relay-pulse control unit (RPCU) with a lagging feedback and topping differentiator (a real differentiating element, RD), with calculating the output according to a PID algorithm and using the actuator model for its implementation, and with calculating the control output speed and using a pulse-width modulator. Formulas for calculating the parameters of the RPCU and RD primary components from the condition of approaching the equivalent PID algorithm are given. The system version with a PID controller with the actuator control proceeding from its model is considered in two options: with individual integrators for the controller’s integral component and the actuator model, and with a common integrator for the controller’s integral component and the actuator model. In the latter option, the signal from the actuator model is subtracted from the controller’s integral component, due to which the possibility of the integrator’s output to reach the integral component’s limit values is ruled out. The versions are compared by analyzing the automatic control system performance in the pulsed actuator’s operation mode based on simulation for the superheated steam temperature control section of a steam boiler equipped with a surface steam desuperheater. The analysis was carried out taking into account both the usual dynamic accuracy indicators and the number of actuators switched into operation during the transient. It is shown that the advantage of the version with the PID algorithm and common integrator for the integral component and the actuator model is that there is no need in this case to calculate the controlled variable second derivative; in addition, this version is free from the problem connected with accumulation of the difference between the signals from the actuator and its model. This version can be considered to be more preferred in implementing a PID algorithm in the software of programmed controllers. Recommendations for self-tuning of pulse duration and the control unit relay element parameters during the control process depending on the algorithm’s individual components are given. By using the proposed recommendations, it becomes possible to achieve an essentially lower actuator switching frequency during the control process.

High strain rate in situ micropillar compression of a Zr-based metallic glass

High strain rate micromechanical testing can assist researchers in elucidating complex deformation mechanisms in advanced material systems. In this work, the interactions of atomic-scale chemistry and strain rate in affecting the deformation response of a Zr-based metallic glass was studied by varying the concentration of oxygen dissolved into the local structure. Compression of micropillars over six decades of strain rate uncovered a remarkable reversal of the strain rate sensitivity from negative to positive above ~ 5 s−1 due to a delocalisation of shear transformation events within the pre-yield linear regime for both samples, while a higher oxygen content was found to generally decrease the strain rate sensitivity effect. It was also identified that the shear band propagation speed increases with the actuation speed, leading to a transition in the deformation behaviour from serrated to apparent non-serrated plastic flow at ~ 5 s−1.Graphic abstract

A microwave powered polymeric artificial muscle

Twisted and coiled polymer fibres are vastly used to fabricate artificial muscles with stroke and stress outputs rivalling those of mammalian muscles. The thermal stimulation of these fibres, however, requires a tethered power source, limiting their application as truly autonomous system. Here, a novel type of coiled polymer actuator is demonstrated where thermal stimulation is realized via microwave radiation. This helical writhe shaped actuator is made of carbon nanotube (CNT) filled highly-drawn nylon 6 fibres and offers muscle-like linear movements when microwave-irradiated. The embedded CNTs absorb the external electromagnetic energy and act as volumetric heating sources in the fibres. When stimulated via microwave radiation, the unique anisotropic thermal expansion phenomenon of highly-drawn fibres provides >8% reversible length contraction of the writhe muscle with a starting actuation speed of ~0.8%/sec. The maximum specific work output is calculated to be ~0.2 kJ/kg, which is >5 fold higher than that for natural muscle. The developed technology offers an opportunity to stimulate the state-of-art thermoresponsive artificial muscles wirelessly and/or to use them for autonomous soft robotic application.

Research of pneumatic cylinder actuator’s dynamics

Pneumatic actuators are widely used in industry as the most reliable automation tools. The performance of automated systems depends on the speed of pneumatic actuators. Therefore, the development of methods for studying the dynamic processes of pneumatic actuators is an urgent task. This paper proposes a mathematical model of a pneumatic actuator of the hoist, which is convenient for computer calculations using universal mathematical packages. Friction forces on transient processes in a pneumatic actuators are investigated as an example of the application of a mathematical model.

Mathematical model of a single-acting pneumatic cylinder actuator

Pneumatic actuators are widely used in industry as the most reliable automation tools. The efficiency of automated systems depends on the speed of pneumatic actuators. Therefore, the development of methods studying the dynamic processes of pneumatic actuators is an urgent task. this paper concerns a mathematical model of a single-acting pneumatic cylinder actuator, which is convenient for computer calculations using universal mathematical packages. As an example of the application of a mathematical model, paper shows the influence of the piston diameter on transient processes in a pneumatic actuator.