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To improve the speed of mass transfer, a magnetic suspension platform (MSP) is used to transport the display chips. A novel 6‐DOF MSP is proposed in this paper. An improved Halbach array is used to supply the magnetic flux density. Two types of permanent magnets are utilised in the improved Halbach array. The smaller permanent magnet serves to consolidate the magnetic flux density, thereby enhancing the uniformity of the magnetic field. The finite element method is employed to analyse how variations in angle impact both the strength and uniformity of the magnetic flux density. The results show that the magnetisation direction of 45° is the most effective in terms of improving the uniformity and strength of the magnetic density. Finally, a 6‐DOF MSP prototype is manufactured. A magnetic density measurement experiment and a stable suspension experiment for the actuator are conducted. The results indicate an enhancement in the uniformity of the magnetic field within the air gap. Additionally, the maximum suspension positioning accuracy of the actuator is about 750 nm. [ABSTRACT FROM AUTHOR]

Stepper motors are synchronous electric actuators with incremental displacement that can be controlled in open loop in position or speed. Unfortunately, the rotor oscillations that characterize stepper motors are a major handicap that limits the use of this type of actuator in precision industrial applications and especially in biomedical systems. Improving motor drive performance is challenging due to the presence of uncertainty in system parameters and large load variations. To overcome these problems and the shortcomings of conventional control approaches, a new control concept based on fuzzy logic is developed. To this purpose, this paper proposes a fuzzy logic concept (FLC) for damping rotor oscillations of stepper actuator devoted to an Electrical Syringe Pump application. The FLC membership functions and rules are designed with value normalization that allows the developed controller able to be flexible when applied to a wide range of applications. The proposed FLC is numerically validated. Critical testing scenarios are employed including motor inertia variation, supply voltage variation, fluid friction variation and for different loads. Moreover, thanks to its normalized design, the proposed FLC is not limited to the studied biomedical applications, but can be applied to other application systems. [ABSTRACT FROM AUTHOR]

Since robotic arms operating close to people are becoming increasingly common, there is a need to better understand how they can be made safe when unintended contact occurs, while still providing the required performance. Several actuators and methods for improving robot safety are studied and compared in this paper. A robotic arm moving its end effector horizontally and colliding with a person's head is simulated. The use of a conventional electric actuator (CEA), series elastic actuator (SEA), pneumatic actuator (PA) and hybrid pneumatic electric actuator (HPEA) with model-based controllers are studied. The addition of a compliant covering to the arm and the use of collision detection and reaction strategies are also studied. The simulations include sensor noise and modeling error to improve their realism. A systematic method for tuning the controllers fairly is proposed. The motion control performance and safety of the robot are quantified using root mean square error (RMSE) between the desired and actual joint angle trajectories and maximum impact force (MIF), respectively. The results show that the RMSE values are similar when the CEA, SEA, and HPEA drive the robot's first joint. Regarding safety, using the PA or HPEA with a compliant covering can reduce the MIF below the safety limit established by the International Organization for Standardization (ISO). To satisfy this ISO safety limit with the CEA and SEA, a collision detection and reaction strategy must be used in addition to the compliant covering. The influences of the compliant covering's stiffness and the detection delay are also studied. [ABSTRACT FROM AUTHOR]

Parallel robots have many remarkable advantages over their conventional serial counterparts. Highly accurate positioning capability and high payload-to-weight ratio are among the main ones. The main factor underlying all these advantages is their closed-loop construction. However, this constructional feature also causes a special singularity problem, which constitutes their biggest disadvantage. Characteristic singularities classified as Type II exist inside their workspace, around which the magnitude of the inverse dynamic solution grows unboundedly. This naturally yields the saturation of the actuators and eventually in uncontrollability of the robot. Consequently, the whole workspace becomes impossible to be used. In order to pass through a Type II singularity, the consistency of the motion equations of the robot must be maintained at that singularity. However, any Type II singular configuration can transform into a high-order singularity, which, in order to be passed through, requires additional conditions other than the consistency. Therefore, full utilization of the whole workspace with a minimum number of conditions requires to avoid high-order singularities. The present article contributes to the literature by developing path and trajectory planning principles for preventing a two-degree-of-freedom planar parallel robot with RPRPR structure from experiencing high-order singularities. [ABSTRACT FROM AUTHOR]

In this paper, we propose an inchworm-type soft robot using a self-healing gel as its body and shape-memory alloy (SMA) wires as its actuators. To realize inchworm-like locomotion, two coiled SMA wires are placed in parallel in the gel-fabricated body. The bottom-side wire and the upper-side wire reciprocally bend by applying electric current to the actuators. To realize the self-restoration automatically, the robot consists of a self-healing body equipped with magnets. The paper introduces the structure of the inchworm-shaped robot with its inchworm-like locomotion performance, together with the self-healing function. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuators (DEAs) are soft, electrically powered actuators that have no discrete moving parts, yet can exhibit large strains (10%–50%) and moderate stress (∼100 kPa). This Tutorial describes the physical basis underlying the operation of DEA's, starting with a simple linear analysis, followed by nonlinear Newtonian and energy approaches necessary to describe large strain characteristics of actuators. These lead to theoretical limits on actuation strains and useful non-dimensional parameters, such as the normalized electric breakdown field. The analyses guide the selection of elastomer materials and compliant electrodes for DEAs. As DEAs operate at high electric fields, this Tutorial describes some of the factors affecting the Weibull distribution of dielectric breakdown, geometrical effects, distinguishing between permanent and "soft" breakdown, as well as "self-clearing" and its relation to proof testing to increase device reliability. New evidence for molecular alignment under an electric field is also presented. In the discussion of compliant electrodes, the rationale for carbon nanotube (CNT) electrodes is presented based on their compliance and ability to maintain their percolative conductivity even when stretched. A procedure for making complaint CNT electrodes is included for those who wish to fabricate their own. Percolative electrodes inevitably give rise to only partial surface coverage and the consequences on actuator performance are introduced. Developments in actuator geometry, including recent 3D printing, are described. The physical basis of versatile and reconfigurable shape-changing actuators, together with their analysis, is presented and illustrated with examples. Finally, prospects for achieving even higher performance DEAs will be discussed. [ABSTRACT FROM AUTHOR]

In today's industrial environment, effectively monitoring assets throughout their entire lifetime is essential. Prognostic and Health Management (PHM) is a powerful tool that enables users to achieve this goal. Recently, sensor-equipped actuator electrification has been introduced to capture intrinsic key system variables as time series. This data flow has opened up new possibilities for extracting essential maintenance information. To leverage the full potential of these data, we have developed a novel algorithm for time series registration, which serves as the core of a new similarity-based prognostic method in a PHM context: Partial Time Scaling Invariant Temporal Alignment for Remaining Useful Life Estimation (PARTITA-RULE). Our algorithm transforms acceleration signals into a subset of descriptors for a new actuator, creating a time series. We can extract valuable maintenance information by aligning this time series with the one already labeled from past behaviors of the same actuator's family of heterogeneous sizes and robust scaling factors. The unique aspect of our method is that we do not need to inject prior knowledge for registration intervals at this stage. Once the unknown series is aligned with all possible candidates, we create a weighting scheme to assign a relevance score with an uncertainty measurement for each aligned pair. Finally, we compute interpolants on the Wasserstein space to obtain the asset's Remaining Useful Life (RUL). It is important to note that a relevant result in a PHM context requires a database filled with different labeled system behaviors. To test the effectiveness of our method, we use an industrial data set of vibration signals captured on an aeronautical electric actuator. Our method shows promising Remaining Useful Life (RUL) estimation results even with incomplete time segments. [ABSTRACT FROM AUTHOR]

Underwater pressure-bearing structures are produced in practice by means of pressure self-enhancement methods in order to improve the stress distribution and enhance the pressure-bearing performance. On the other hand, the pairs equation shows that stress is an important factor influencing the degradation of the structure. In fact, improving the stress distribution will not only improve the pressure-bearing performance, but will have an impact on the life degradation trend. Thus, pressure self-enhancement affects the structural life by changing the stress distribution. With this in mind, this paper considers the effect of pressure self-enhancement on the service time of subsea structures, and a Bayesian network (BN)-based method that can be used to predict the remaining useful life (RUL) of underwater self-enhanced structures is proposed. The method also takes into account the influence of multiple sources of structural factors in order to predict the RUL of the structure more accurately. The life degradation process of an all-electric Christmas tree valve actuator is used as a case study. The prediction results are compared with data in the literature to verify the validity of the method. The results have implications for guidance on the O&M assurance of underwater production systems. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuators have attracted growing interest for soft robot due to their large deformation and fast response. However, continuous high-voltage loading tends to cause the electric breakdown of the actuator due to heat accumulation, and viscoelasticity complicates precise control. The snap-through bistability of the Venus flytrap is one of the essential inspirations for bionic structure, which can be adopted to improve the shortcoming of dielectric elastomer actuators and develop a new actuation structure with low energy consumption, variable configuration, and multi-mode actuation. Hence, in this paper, the structural design principles of electroactive bistable actuators are first presented based on the total potential energy of the structure. Following that, a feasible design parameter region is provided, the influence of crucial parameters on the actuation stroke, trigger voltage, and actuation charge are discussed. Finally, according to the coupling relationship between the bending stiffness and the bistable property of the actuator, the adjusting methods of bistable actuation are explored. A qualitative experiment was performed to verify the feasibility and correctness of the bistable design methodology and the actuation regulation strategy. This study provides significant theoretical guidance and technical support for developing and applying dielectric elastomer actuators with multi-mode, high-performance, and long-life characteristics. [ABSTRACT FROM AUTHOR]

This paper addresses the issue of the verification and comparison of the selected properties of a newly developed electric actuator. This actuator is intended to act as the drive of a walking robot designed for robotic football. Its envisioned placement is inside the robot's knee joint and in its upper part. An integral part of the actuator is a harmonic precision gearbox and an absolute rotation sensor. The prototype of the newly developed actuator consists of both aluminum and 3D-printed parts. The selected parameters were verified according to the selected characteristics of ISO standard 9283, namely a one-directional pose accuracy and repeatable pose accuracy. The obtained data were compared with those of the standard actuator used thus far in constructing robots for robotic football. The implemented verification is based on the need to improve the performance parameters of the actuator while ensuring the sufficient accuracy of stopping the actuator in the required position. This is ensured by the use of a more accurate harmonic reducer and rotation sensor compared to the standard actuator. [ABSTRACT FROM AUTHOR]

The actuator is a fundamental component for a variable-area exhaust nozzle. Conventional actuators for variable-area exhaust nozzles are hydraulic actuators and electric motors. However, they are heavy, large, and structurally complex. Shape memory alloys (SMAs) are light, small, structurally simple, and have unique advantages not found in conventional actuators. However, SMA actuators occupy a large space in the radial direction and cannot be fixed to surfaces with different radii of curvature. Moreover, once designed, the actuating displacement of the actuator cannot be adjusted. To solve this problem, this study develops a novel non-embedded, adjustable, and flexible SMA actuator for variable-area exhaust nozzle actuation. An analytical model is presented to predict mechanical performance. Subsequently, experiments of this flexible SMA actuator are conducted to study the mechanical performance. A proof-of-concept, variable-area exhaust nozzle of the aeroengine is designed, fabricated, and tested to obtain the properties of the exhaust nozzle that are actuated by the flexible SMA actuator. In the experiments, the movement trajectory of the exhaust nozzle is captured using an image recognition technique, and the area changes of the exhaust nozzle are calculated. The results show that the actuator is flexible and can be bent at any angle from −90° to +90°. The actuating displacement of the flexible SMA actuator can be adjusted by increasing or decreasing the number of hinged units. In addition, the area change of the exhaust nozzle is 64.4%, exceeding the largest area change of 40% in previous studies on SMA-actuated exhaust nozzles. [ABSTRACT FROM AUTHOR]

Constant monitoring of driving conditions and observation of the surrounding area are essential for achieving reliable, high-quality autonomous driving. This requires more reliable sensors and actuators, as there is always the potential that sensors and actuators will fail under real-world conditions. The sensitive condition-monitoring methods of sensors and actuators should be used to improve the reliability of the sensors and actuators. They should be able to detect and isolate the abnormal situations of faulty sensors and actuators. In this paper, a developed model-based method for condition monitoring of the sensors and actuators in an electric vehicle is presented that can determine whether a sensor has a fault and further reconfigure the sensor signal, as well as detect the abnormal behavior of the actuators with the reconfigured sensor signals. Through the simulation data obtained by the vehicle model in complex road conditions, it is proved that the method is effective for the state detection of sensors and actuators. [ABSTRACT FROM AUTHOR]

Actuator, mostly valve, wearing is an important factor of the overall industrial control system operational cost. Actuator operational wear strongly depends on its operation. Highly utilized elements have a tendency to degrade faster. Therefore, the maintenance teams prefer to minimize their moves. In contrary, control engineers need the actuators to actively operate in their control loops to mitigate disturbances and follow the desired trajectories. Higher control performance is often achieved with an active use of actuators. Control loop quality depends on the controller setup and loop auxiliary functionality. Properly designed filtering not only facilitates controller action, but also impacts actuator operational wear. Industrial control templates are built using the blockware that is embedded in the existing control system. Distributed control system (DCS) and programmable logic controller (PLC) have a limited number of control algorithms. An engineer has to design the control structure and the associated sensor noise filtering using available functionality. This paper evaluates and measures the impact of noise filtering on the loop performance and on the actuator weariness. Relations between noise filtering time constant, loop performance and valve travel deliver recommendations for control engineers. [ABSTRACT FROM AUTHOR]

Ultra‐reliable low‐latency communication (URLLC) has gained significant interest since it deals with short packet transmission adopted to reduce latency; however, this implies that the conventional Shannon capacity formula is not applicable, and the achievable data rate becomes a complex function of the decoding error probability and blocklength. This paper studies URLLC transmission using a time‐division multiple access scheme with an arbitrary number of actuators utilising a reconfigurable intelligent surface. The authors optimisze the weighted sum rate of this system subject to reliability, total energy, and latency constraints. For the blocklength allocation in a scenario where each actuator is allocated equal power, a closed‐form analytical solution is provided. Also, for the case of joint optimization of the blocklength and power of each actuator, an analytical solution is provided for the case of two actuators, while an iterative sequential quadratic programing method is adopted for the case of an arbitrary number of actuators. The proposed methodology provides a low‐complexity, fast solution, which is more efficient than using exhaustive search techniques. The results show that in some cases, optimization of the blocklength provides a near‐optimal solution at low complexity, while jointly optimising the blocklength and the power per actuator has an improved performance at the cost of additional complexity. [ABSTRACT FROM AUTHOR]

In this study, the development of a novel hydraulic robotic actuator is introduced. With the use of additive manufacturing (AM), lightweight and compact design can be achieved. A high load-to-weight ratio 3-DOF robot actuator with orthogonally connected hydraulic rotary cylinders is designed for AM. To validate the feasibility, a titanium hydraulic robot actuator is prototyped by using the metal powder bed fusion (M-PBF) AM process. A set of loading experiments are conducted on the AM-printed prototype. The study shows that system-level AM design and manufacturing methods can help gain increased output torque but with reduced weight and volume. With the use of hydraulic driving, the robotic actuator is more compact and solid to resist to tough environments as compared with the traditional actuators using electric motors. This study also implies the potential wide application of AM to design and print similar hydraulic link mechanism in heavy-duty robot or mobile humanoid robot. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic flow control systems have proven to be among the most promising flow control strategies within previous decades. Several methods for efficient evaluation and description of the effect of such systems are indeed available. Yet, due to these systems' critical role in various applications, possible improvements are still investigated. A new phenomenological model is presented for the simulation of the plasma actuators based on the electrodynamic properties of low-frequency plasmons. The model simulates the plasmonic region as a dispersive medium. This dissipated energy is added to the flow by introducing a high-pressure region, calculated in terms of local body force vectors, requiring the distribution of the electric field and the polarization field. The model determines the electric field for the computation of the body force vector based on the Poisson equation and implements the simplified Lorentz model for the polarization field. To fully explore the performance of the presented model, an experiment has been conducted providing a comparison between the observed effect of plasma actuators on the fluid flow with the results predicted by the model. The model is then validated based on the results of other distinct experiments and exempted numerical models, based on the exchanging momentum with the ambient neutrally charged fluid, demonstrating that the model has improved adaptability and self-adjusting capability compared to the available models. [ABSTRACT FROM AUTHOR]

Dielectric Elastomer Actuator (DEA) shows the complex characteristics such as the inherent nonlinearity, intricate electromechanical coupling, time-dependent viscoelastic behavior, etc., which make it difficult to establish a dynamic model. This paper proposes a dynamic model based on the physical properties of DE materials to describe the above characteristics. The Gent model and the generalized Kelvin model are used to describe the free energy and the viscoelastic characteristics of DEA, respectively. Based on the experimental results, the differential evolution algorithm is used to identify the model parameters. Comparing the experimental data with the model prediction, the validity and generalization of the model are demonstrated. [ABSTRACT FROM AUTHOR]

Water‐responsive (WR) materials that reversibly deform in response to humidity changes show great potential for developing muscle‐like actuators for miniature and biomimetic robotics. Here, it is presented that Bacillus (B.) subtilis' peptidoglycan (PG) exhibits WR actuation energy and power densities reaching 72.6 MJ m−3 and 9.1 MW m−3, respectively, orders of magnitude higher than those of frequently used actuators, such as piezoelectric actuators and dielectric elastomers. PG can deform as much as 27.2% within 110 ms, and its actuation pressure reaches ≈354.6 MPa. Surprisingly, PG exhibits an energy conversion efficiency of ≈66.8%, which can be attributed to its super‐viscous nanoconfined water that efficiently translates the movement of water molecules to PG's mechanical deformation. Using PG, WR composites that can be integrated into a range of engineering structures are developed, including a robotic gripper and linear actuators, which illustrate the possibilities of using PG as building blocks for high‐efficiency WR actuators. [ABSTRACT FROM AUTHOR]

Light‐driven actuation of synthetic polymers is an emerging field of interest because it offers simple remote addressing without complicated hydraulic, electric, or magnetic systems. Reviews on this area predominantly emphasize on the development of mechanical motions like bending, twisting, folding, etc. However, the scientific and fundamental aspects of these materials are critical in order to expand applications and industrial relevance. Polymer actuators driven by light, not only comprise soft actuators (large deformations at low stress) but also include stiff actuators (high actuation stress at low strain). Synthetic polymeric materials with photo‐responsive additives together with underlying mechanisms, processing parameters, and final properties are required to broaden the scope of the field. In particular, parameters like actuation stress, actuation strain, and work capacity have been given limited attention in the past and are discussed extensively. This work gives a comprehensive critical review on all light‐driven synthetic polymer actuators, their actuating mechanisms, and materials. A holistic perspective together with an insight into future prospects can lead academia and industry toward future innovations and applications of these exciting functional materials. [ABSTRACT FROM AUTHOR]

A dynamic model for the soft dielectric elastomer actuator (SDEA) is developed in this paper to describe its intricately nonlinear behaviors considering different input frequencies and external loads. Firstly, the characteristics of the SDEA are observed by several groups of experiments. A phenomenological model is proposed to describe the asymmetric hysteresis behavior of the SDEA, which consists of a Prandtl-Ishlinskii model with one-side play operator and a dead-zone model with one-side dead-zone operator. Meanwhile, a mathematical model is built to depict the creep behavior of the SDEA. The dynamic model including a module and a linear system is proposed to further handle the rate-dependent and the stress-dependent hysteresis behaviors of the SDEA, in which the module is the superposition of the asymmetric hysteresis model and the creep model. To ensure that the inverse solution of the module is existing, as well as the linear system is controllable and observable, the constraint conditions of parameter values of the dynamic model are constructed. Next, the parameter identification is divided into two steps, and the differential evolution algorithm is employed in each step. Finally, the generalization of the proposed dynamics model is demonstrated by comparing the model output with the experimental data. [ABSTRACT FROM AUTHOR]

Electro-hydrostatic actuator (EHA) is a type of actuator in more electric aircraft, which is a highly integrated local volume control hydraulic actuator, and can improve the reliability and efficiency. However, the motor heating can hardly be taken out due to the feature of the local closed hydrostatic system, especially under heavy load. In order to solve the problem, direct load sensitive EHA is an effective way to reduce heat, but the dynamic performance is inevitably sacrificed. To achieve the targets of both low heat generation and high dynamic response, a novel active load sensitive EHA (ALS) is proposed in this article. The key characteristic of ALS is that a special pressure following valve (PFV) is added between the load sensitive pressure point and the actuator of the swash plate in the pump. Furthermore, the PFV is actively controlled to adjust the load sensitive pressure. Based on this concept, detailed analysis and design of the system are presented. Following, the load sensitivity is controlled based on the fuzzy algorithm and the main loop is controlled by traditional proportional−integral differential. Finally, compared with the results of simulation and experiments, ALS can effectively reduce motor heating and maintain high dynamic performance, simultaneously. [ABSTRACT FROM AUTHOR]

Linear actuators are widely used in all kinds of industrial applications due to being devices that convert the rotation motion of motors into linear or straight traction/thrust motion. These actuators are ideal for all types of applications where inclination, lifting, traction, or thrust is required under heavy loads, such as wheelchairs, medical beds, and lifting tables. Due to the remarkable ability to exert forces and good precision, they are used classic control systems and controls of high-order. Still, they present difficulties in changing their dynamics and are designed for a range of disturbances. Therefore, in this paper, we present the study of an electric linear actuator. We analyze the positioning in real-time and attack the sudden changes of loads and limitation range by the control. It uses a general-purpose control with self-tuning gains, which can deal with the essential uncertainties of the actuator and suppress disturbances, as they can change their weights to interact with changing systems. The neural network combined with PID control compensates the simplicity of this type of control with artificial intelligence, making it robust to drastic changes in its parameters. Unlike other similar works, this research proposes an online training network with an advantage over typical neural self-adjustment systems. All of this can also be dispensed with the engine model for its operation. The results obtained show a decrease of 42 % in the root mean square error (RMSE) during trajectory tracking and saving in energy consumption by 25 % . The results were obtained both in simulation and in real tests. [ABSTRACT FROM AUTHOR]

A new electrode architecture for dielectric elastomer actuators (DEAs) is introduced in which a soft polyacrylate film is coated with a biphasic mixture of silver, indium, and gallium. This Ag–In–Ga coating functions as a soft electrode that is ultrathin, highly compliant, highly conductive, stretchable, and non‐smearing. Compared to carbon grease, sputter‐deposited metal coating, and particle‐filled conductive elastomers, this biphasic coating exhibits a unique combination of solid‐state integrity, extreme mechanical compliance, and low electrical resistivity. Herein, how DEAs with an Ag–In–Ga coating exhibit a 5× larger actuation speed compared to carbon‐coated dielectric films is shown. The influence of coating thickness on the mechanical stiffness and blocking force is also examined. [ABSTRACT FROM AUTHOR]

Light electric vehicles are alternative solutions to passenger cars in terms their lower costs and space saving in city traffic. Narrow tilting vehicles (NTV), known also as three–wheeled vehicles, can be equipped with an active tilting stability controller that tilts the vehicle automatically during cornering to enable lateral stability. There are mainly direct tilt control (DTC), steering tilt control (STC), and combined DTC–STC methods described in the literature. The DTC method is typically applied up to 10 km/h vehicle speeds. Considering city traffic and frequent start–stop cycles, the DTC method needs to be improved in terms of lower actuator torque and energy consumption. DTC can be designed by using either hydraulic or servo motor actuators. In state of the art, the servo motor actuator has not been studied in detail considering its integration and application aspects. Mostly, the actuator has been considered as a black box model. Proposed control method in this study enables improvements in the direct tilt control system (DTC) in terms of reducing the actuator peak torque and enables the application of DTC at higher vehicle speeds. Regarding the modeling of the electric actuator, a permanent magnet synchronous motor and field-oriented control model are also included in the simulation model. Modelling of the electric actuator enables accurate representation of actuator dynamics. In this way, battery Ah capacity can be sized and energy consumption of the electric actuator can be calculated for a given drive cycle. To this end, objective of this study is to design a direct tilt control method including the electrical drives and motion control concepts. In this way, an application methodology of the servo motor actuator is developed and implemented on a narrow tilting three-wheeled electric vehicle. Interactions between tilt control system and the servo motor actuator system are described from practical aspects. [ABSTRACT FROM AUTHOR]

Cylindrical dielectric elastomer actuator (CDEA) is known as an effective type of dielectric elastomer actuators. Owing to the advantageous properties of compact structure, CDEA has shown promising potential application in the development of the soft robotics. However, the inherent nonlinear viscoelasticity of dielectric elastomers causes the strain of actuators to change with time. This feature of CDEA is challenging to modeling and control of DE actuator and may limit their motion accuracy in practical applications. In this paper, to accurately describe the time-dependent nonlinear viscoelasticity properties of the actuator, by combining the advantages of the Kelvin–Voigt model and the Generalized Maxwell, a generalized combination model is proposed. The comparisons between the model prediction and experimental results demonstrate that the proposed model can accurately predict the response of the actuator under step voltage excitation, and the minimum prediction error can be achieved by 1.97%. This research results can provide theoretical guidance for the design of CDEA and is helpful to reduce the creep effect and improve the control efficiency of the CDEA. [ABSTRACT FROM AUTHOR]

In this work, the Cosserat formulation of geometrically exact beam dynamics is extended by adding the electric potential as an additional degree of freedom to account for the electromechanical coupling in the dielectric elastomer actuators. To be able to generate complex beam deformations via dielectric actuator, a linear distribution of electric potential on the beam cross section is proposed. Based on this electric potential, the electric field and the strain-like electrical variable are defined for the beam, where the strain-like electrical variable is work-conjugated to the electric displacement. The electromechanically coupled strain energy for the beam is derived consistently from continuum electromechanics, which leads to the direct application of the material models in the continuum to the beam model. The electromechanically coupled problem in beam dynamics is first spatially semidiscretized by 1D finite elements and then solved via variational time integration. By applying different electrical boundary conditions, different deformations of the beam are obtained in the numerical examples, including contraction, shear, bending and torsion. The damping effect induced by the viscosity as well as the total energy of the beam are evaluated. The deformations of the electromechanically coupled beam model are compared with the results of the 3D finite element model, where a good agreement of the deformations in the beam model and that in the 3D finite element model is observed. However, less degrees of freedom are required to resolve the complex deformations in the beam model. [ABSTRACT FROM AUTHOR]

This article proposes a dynamic model and a tracking control strategy for a dielectric elastomer (DE) actuator based on the model predictive controller (MPC). First, the dynamic model of the DE actuator is established, which can describe its asymmetric hysteresis, creep, and even rate-dependent hysteresis behaviors simultaneously. Then, on the basis of the established dynamic model, an inverse compensation controller (ICC) is designed to compensate the hysteresis and creep nonlinearities of the DE actuator on its tracking control. Moreover, the MPC is designed to cooperate with the ICC, which can overcome the influences of the modeling error and uncertainties on the control precision. Finally, several experiments demonstrate the effectiveness of the proposed dynamic model and control strategy. [ABSTRACT FROM AUTHOR]

Parallel electrical manipulator systems have become prevalent in attitude simulation in recent years to achieve a high precision attitude tracking. However, the attitude tracking performance is affected by internal uncertainty, external disturbances, and uncoordinated performance of the electric actuators. In this article, a coordinated attitude control strategy that combined the distributed active disturbance rejection control (ADRC) framework with a consensus algorithm is proposed for the parallel electrical manipulators. We indicate that the proposed coordinated attitude control strategy solves the uncoordinated problem of the electric actuators, and compensates the disturbances that include internal uncertainty and external disturbances. Meanwhile, a closed-loop control is achieved with a guaranteed stable tracking performance. The control strategy is applied to a 3-DOF parallel electrical manipulator system, and comparative experimental results indicate that the proposed coordinated ADRC consensus control strategy can achieve a better tracking performance than the strategy with only ADRC. [ABSTRACT FROM AUTHOR]

A long strip of a pre-stretched dielectric elastomer actuator (DEA) is necessary for strain accumulation, but it relaxes laterally and thickens non-uniformly. As compared to a short strip under the same voltage activation, the long relaxed strip is subjected to a less electric field and, thus, undergoes less active strain. Here, we developed a flexible ladder frame to reinforce and divide the long DEA in a bowtie series. When being pulled, the ladder frame unbuckled; it, in turn, helped to pre-stretch tautly the DEA membrane. Interestingly, its flanges enhance force transmissions, acting like tensioning cables for a suspension bridge. Hence, the maximum isometric stress of this bowtie series was 24% higher than the short pure-shear one and 6.5 times the long uniaxial one. With 2.2 times enhanced dielectric strength across a taut DEA membrane, the bowtie series generated an isotonic strain 3.2 times that a long non-reinforced and relaxed DEA did. Hence, the reinforced DEAs can provide a more forceful drive for bio-inspired robots. [ABSTRACT FROM AUTHOR]

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This paper presents an electroactive and soft vibrotactile actuator based on a dielectric elastomer. The vibrotactile actuator is composed of an upper layer, an adhesive tape layer, a dielectric layer with bumps, and a lower layer. When a voltage is applied to the actuator, an electrostatic force created between the upper and lower layers pulls the upper layer down, compressing the dielectric layer. As soon as the applied voltage is released, the upper layer is quickly restored to its initial state by the elastic force of the compressed dielectric elastomer. Because two forces contribute to the actuation at the same time, the created vibration is sufficiently strong to stimulate human mechanoreceptors. When the applied voltage is removed, the upper layer and dielectric elastomer return to their initial shapes. We conducted experiments to determine the best weight ratio of polydimethylsiloxane (PDMS) and Ecoflex, and to quantitatively investigate the haptic performance of the proposed vibrotactile actuator. The experiments clearly show that the plasticized vibrotactile actuator can create a variety of haptic sensations over a wide frequency range. [ABSTRACT FROM AUTHOR]

Ionic electromechanically active polymers (IEAPs) are considered attractive candidates for soft, miniature, and lightweight actuators. The bucky-gel actuator is a carbonaceous subtype of IEAP that due to its structure (i.e. two highly porous electrodes sandwiching a thin ion-permeable electrolyte layer) and composition (i.e. being composed of soft porous polymer, carbon nanotubes, and ionic liquid) is very similar to an electric double-layer capacitor. In response to the voltage applied between the electrodes of a bucky-gel actuator, the laminar structure bends. The time domain behavior exhibits, however, a phenomenon called the back-relaxation, i.e., after some time the direction of bending is reversed even though voltage remains constant. In spite of the working mechanism of IEAP actuators being generally attributed to the transport of ions within the soft multilayer system, the specific details remain unclear. A so-called two-carrier model proposes that the bending and subsequent back-relaxation are caused by the relocation of two ionic species having different mobilities as they enter and exit the electrode layers. By adopting the two-carrier model for bucky-gel actuators, we see very good agreement between the mathematical representation and the experimental data of the electromechanical behavior. Furthermore, since the bucky-gel actuator is viscoelastic, we propose to use the time domain response of a blocking force as the key parameter related to the inner ionic mechanism. We also introduce a method to estimate the viscoelastic creep compliance function from the time domain responses for curvature and blocking force. This analysis includes four types of bucky-gel actuators of varying composition and structure. [ABSTRACT FROM AUTHOR]

Dielectric elastomer (DE) possesses attributes such as large deformation and fast response. As a typical DE actuating structure, the multilayered DE bending actuator (MDEBA) is lightweight and can actuate in relatively low voltage without a rigid frame and pre-stretch. These attributes arouse wide research interest in the MDEBA on the application of soft robots. However, due to its large deformation and nonlinear electromechanical dynamics, the control of MDEBA remains highly challenged. Considering the large bending deformation and gravity effect, we develop an electromechanical dynamic model-based control strategy, which can adaptively compensate for the parameter uncertainties during the actuation of MDEBA. Experimental results validate that this control strategy provides highly enhanced control performance compared to the proportional integral derivative (PID) controller. The electromechanical modeling method and dynamic control strategy may guide the further study of MDEBA, soft robots, and flexible devices. [ABSTRACT FROM AUTHOR]

In this study, a mobile overground gait-training system (OGTS) was designed, and a prototype was manufactured to determine the feasibility and control stability of the designed system. Approval was received from the Institutional Review Board of Fu Jen Catholic University for conducting experimental testing on healthy individuals with the designed mobile OGTS. The designed system comprises a mobile electric walking aid (EWA), a body weight support system (BWSS), and an exoskeleton gait orthosis (EGO). The system can perform multiple functions for physical overground gait training. The mobile EWA and EGO can be operated separately from the mobile OGTS. An interval type-2 fuzzy sliding controller (IT2FSC) was designed to compensate for disturbances and uncertainties because the mobile OGTS has a coupling issue and potential subjects have different weights and body shapes. The mobile OGTS has one IT2FSC to provide a pulse-width modulation output to regulate two linear actuators for the BWSS, and it adopts four IT2FSCs to produce voltage outputs to control the gait trajectory of the EGO. Three experiments demonstrated that the mobile OGTS provides a stable control force to assist the user in overground gait training as well as assist-as-needed body weight support for gait training. [ABSTRACT FROM AUTHOR]

A self-holding three-position electric tubular actuator (SHTPETA) is described in the article. The proposed linear actuator can be applied in a clutch system, where it is necessary to change certain mover positions over time. Other potential applications of such actuators can be shift of gears, coupling (decoupling) of various moving (rotating) mechanisms, or electromagnetic valves. The self-holding force of the proposed SHTPETA is achieved by the reluctance force between the armature and mover cores, where a magnetic flux is excited by a permanent magnet located in the armature and an excitation current is not needed, whereas the moving force is determined by the dc voltage (current) applied to two coils located in the stationary part of the SHTPETA. The article proposes a relatively fast and simple approach for the SHTPETA design process based on the required forces and moved distance. [ABSTRACT FROM AUTHOR]

Thanks to their continuously deformable features, soft bending actuators, including pneumatic and electric actuators, are increasingly used in continuum robots. Further development, however, is limited by the complexity of the multicavity structure in pneumatic actuators and the instability of the electromechanical coupling in dielectric elastomer actuators. In this article, by combining the advantages of the two actuation techniques, a novel hybrid electro-pneumatic bending actuator is proposed that is capable of bending with significantly reduced complexity and improved stability. A timing control method is proposed that enables rapid and significant bending. A low voltage is used for bending guidance with air-pressure concurrently to produce a large bending stroke. The results of experiments indicate that, with increasing air pressure, the bending angle varies in three different stages. These stages are (I) a low-pressure guidance stage, (II) an instability induction stage, and (III) a stable deformation stage. By harnessing the instability at stage II, the driving voltage can be substantially reduced to avoid electric breakdown. By studying the effect of prestretch on bending, the controllability of the bending deformation is improved. The simulation is also used to verify the control method and predict the development path of soft robots. [ABSTRACT FROM AUTHOR]

An experimental study was conducted with the aim of alleviating the vertical tail buffeting of a 55° delta wing using pulsed nanosecond dielectric barrier discharge plasma actuators. The flow physics in the event of wing stall, flow reattachment, vortex breakdown, shear layer under plasma actuation were obtained and analyzed, and results indicate that plasma actuation promotes flow attachment and manipulates the shear layer. The acceleration results indicate that the structural response of the vertical tail increases with an increasing angle of attack, and the first bending mode response increases most significantly at the post-stall angle. Manipulation of flow field by plasma actuation produces a considerable reduction in buffeting response and mainly controls the first bending mode. The characteristics of velocity fluctuations show two important factors affecting buffeting: the redistribution of loads and the spectrum change of fluctuations, both of which are related to the movement of the impingement point of the shear layer onto the vertical tail controlled by plasma actuation. Theoretical analysis indicates that the impingement point moving downward in the vertical direction of the vertical tail under plasma actuation is the main reason for reduction of the first bending mode response. [ABSTRACT FROM AUTHOR]

Recently, multiple wind turbine failure databases have reviewed that the pitch system is one of the subassemblies with the highest failure rates and largest contributors to the overall downtime. Therefore, there has been an increasing interest to provide remote health monitoring for wind turbine pitch system. While most of the research articles are discussing pitch actuation system (hydraulic or electric actuator) faults only, there is very limited research on pitch-bearing-defect detection. This article provides a remote and hardware-free solution to monitor multiaxis pitch-bearing health condition called pitch symmetrical-component analysis. It leverages readily available low-resolution (100 Hz) electrical measurements, mechanical measurements, and control signals from the existing pitch control platform, and innovatively applies symmetrical-component analysis in multiphase ac system to multiaxis pitch control system and introduces multiaxis pitch-bearing degradation trending curves. This hardware-free solution can be directly applied to the existing wind turbines and successfully give the wind farm operator an early warning before multiaxis pitch bearing fails. It has been proved to be accurate, low cost, and has minimum impacts on turbine normal operation, and has been validated by field data from several North America MW-scale wind farms. This approach turns out to be the first hardware-free (no additional hardware needed) method to remotely monitor and diagnose multiaxis wind turbine pitch-bearing condition. [ABSTRACT FROM AUTHOR]

We show that the spatio-temporal electrohydrodynamic (EHD) force production in surface alternative current-dielectric barrier discharge (AC-DBD) actuators is strongly influenced by both the streamer regime during the positive phase and the micro-discharge regime during the negative phase. Focusing on the spatial EHD force profiles, we demonstrate that the ionic wind spatial distribution can only be explained by the positive contribution of the streamer regime. The location of maximum ionic wind is found to be directly linked with the maximum elongation of the streamers at several millimeters from the exposed electrode. In both positive and negative phases of the AC-DBD operation, residual volumetric and surface charges once again linked to the streamer formation and afterburn, result to a variety of positive EHD force zones which, when time-averaged in one AC period, contribute to the generation of the experimentally observed induced thin wall jet. Through a thorough elaboration of our numerical results, we provide an illustrative explanation of the EHD force spatio-temporal evolution, showcase the importance of streamers and retrieve a correct representation of the ionic wind spatial profiles when compared to experiments. [ABSTRACT FROM AUTHOR]

Instability waves developing in the mixing layer of a turbulent jet are in many cases sources of noise generation (high-speed jets, jets near an aircraft wing, etc.). This study experimentally investigates the possibility of active control of instability waves in an unexcited subsonic turbulent jet. The feedback control system consists of near-field microphones providing the reference signal, a plasma actuator based on a high-frequency dielectric barrier discharge, and a data processing module. It is shown that, depending on the system settings, pressure perturbations in the near field of a turbulent jet associated with axisymmetric instability waves can be weakened or enhanced in a predefined narrow frequency band. [ABSTRACT FROM AUTHOR]

This paper investigates the active dynamic and electromechanical characteristics of a new thin folded dielectric electro-active polymer actuator developed by Danfoss PolyPower. The high voltage is supplied to the actuator during dynamic testing to identified the effect of the electrical field on dynamic characteristics. The electromechanical characteristics are investigated by varying the amplitude and frequency of the voltage supplied. The experimental results, such as natural frequency, amplitude response, and loss factor are presented to show the influence of such an electrical field on the characteristic of the actuator. There is a reduction of resonance frequency from 14 Hz to 12 Hz as voltage supply up to 2000 V. The actuating response of the actuator was subjected more to frequency rather than the amplitude of the voltage supplied. Hence, the results may guide the exploration of a new folded thin actuator as an active vibration controller. [ABSTRACT FROM AUTHOR]

The paper presents the author's own method for testing piezoelectric common rail fuel injectors, which for many years were consid-ered non-repairable components. This was mainly due to the lack of availability of spare parts and dedicated measuring equipment, enabling full diagnostics under test bench conditions. As a result, their workshop and laboratory servicing was very limited, as effective disassembly concerned basically only the plunger and barrel assembly (needle with nozzle) for selected reference models. The situation has now improved to such an extent that an author's own regeneration procedure has been proposed with the replacement of the most important controls and actuators. The tests were carried out on the example of Siemens VDO Continental PCR 2.3 fuel injectors from one engine, listing the most important stages of this process, including the correction of fuel dosage and returns. [ABSTRACT FROM AUTHOR]

Unlike the conventional tunable lens which contains cumbersome elements to fulfill the focus adjustment, soft liquid lens shows distinct advantages in compactness and flexibility. This paper presents a computational model of a dielectric elastomer (DE)-based, liquid-coupled soft tunable lens. The vital component of the lens system is a DE film which is divided into lens part and actuation part. The actuation part is annular which is coated with compliant electrodes while the lens part is circular and uncoated. A fixed volume of glycerol is injected into the lens to act as a transparent medium. An applied voltage will trigger the transmission of liquid between the two parts and eventually change the focal length. Governing equations for the two parts are established and the shooting method with two initial guesses is developed to solve the boundary value problems. The simulation results agree well with the experimental data. Several parametric analyses are carried out based on the developed model. It is found that the film thickness, initial volume of the liquid, the prestretch, and areas of the two parts all have significant effects on the focusing ability of the tunable lens. Both the homogeneous and inhomogeneous prestretched schemes are considered. An inhomogeneous prestretch on the annular actuation part is beneficial for improving the focusing ability of the tunable lens. [ABSTRACT FROM AUTHOR]

Dielectric barrier discharge (DBD) plasma actuators with an asymmetric, straight edge electrode configuration generate a wall-bounded jet without moving parts. Mechanistic description of the interaction between the Coulombic forces and fluid motion as a function of DBD parameters remains unclear. This paper presents an experimental investigation of DBD actuators, including electrical current associated with microdischarges, plasma volume and the wall jet momentum over a range of alternating current (AC) frequencies (0.5–2 kHz) and peak-to-peak voltages up to 19.5 kV. Discharge current is measured with a high temporal resolution, plasma volume is characterized optically and the momentum induced by the DBD wall jet is computed based on the axial velocities measured downstream of the actuator using a custom-built pitot tube. Discharge current analysis demonstrated asymmetry between the positive and negative semi-cycle; both currents yielded a power–law relationship with empirical fitting coefficients. Plasma length varies linearly and volume quadratically with voltage. Although plasma length reached an asymptotic value at a higher frequency, the plasma volume grows due to the increasing height of the ionization region. In a simple two-dimensional configuration, the DBD wall jet momentum shows near-linear dependency with discharge current in the range of voltages and frequencies considered in this work. The presented empirical model characterizes the DBD wall jet momentum and the discharge current based only on the AC inputs. With the estimation of plasma volume, the model can be applied for determining more realistic boundary conditions in numerical simulations. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuators fabricated from thin and miniaturized metal electrodes integrated with highly soft and stretchable elastomers offer the promise of opening new possibilities in the field of microrobotics. To achieve large displacements O(10−4) m at actuation voltages O(103) V in actuators with thin metal electrodes, the approach of distributed electrode array with fractal interconnects is proposed, where a single large electrode is replaced with an array of N small individual electrodes physically linked together with fractal interconnects. To investigate the effect of distributed electrode array with fractal interconnects on the static and dynamic response of the actuators, elastomer actuators with different electrode arrays—comprised of N ∈ {1,5,13,25} individual electrodes in the shape of circles—are fabricated and characterized. This study shows that the approach of distributed electrode array with fractal interconnects results in achieving large actuator displacements O(10−4) m at high speeds O(100) mm s−1, making these actuators suitable for driving microrobots. [ABSTRACT FROM AUTHOR]