Types Of Actuators Research Articles

Hydraulic Detrusor for Artificial Bladder Active Voiding.

The gold standard treatment for bladder cancer is radical cystectomy that implies bladder removal coupled to urinary diversions. Despite the serious complications and the impossibility of controlled active voiding, bladder substitution with artificial systems is a challenge and cannot represent a real option, yet. In this article, we present hydraulic artificial detrusor prototypes to control and drive the voiding of an artificial bladder (AB). These prototypes rely on two actuator designs (origami and bellows) based either on negative or positive operating pressure, to be combined with an AB structure. Based on the bladder geometry and size, we optimized the actuators in terms of contraction/expansion performances, minimizing the liquid volume required for actuation and exploring different actuator arrangements to maximize the voiding efficiency. To operate the actuators, an ad hoc electrohydraulic circuit was developed for transferring liquid between the actuators and a reservoir, both of them intended to be implanted. The AB, actuators, and reservoir were fabricated with biocompatible flexible thermoplastic materials by a heat-sealing process. We assessed the voiding efficiency with benchtop experiments by varying the actuator type and arrangement at different simulated patient positions (horizontal, 45° tilted, and vertical) to identify the optimal configuration and actuation strategy. The most efficient solution relies on two bellows actuators anchored to the AB. This artificial detrusor design resulted in a voiding efficiency of about 99%, 99%, and 89%, in the vertical, 45° tilted, and horizontal positions, respectively. The relative voiding time was reduced by about 17, 24, and 55 s compared with the unactuated bladder.

Energy-to-Mass Ratio—A Novel Selection Criterion of Pneumatic Motors Used for the Actuation of Wearable Assistive Devices

The requirements to be met by a wearable assistive device are compactness, lightweight and energy efficiency. While the literature discusses the construction and performance of such devices, no information is provided as to the criteria to be applied in selecting such an actuator, capable of satisfying the mentioned conditions. Ensuring the high autonomy of a wearable assistive device requires actuators that can store a large quantity of energy in a small as possible volume, for example, actuators with a high energy density. This paper presents a comparative study of the performance of two types of pneumatic actuators: single-acting cylinders and pneumatic muscles, respectively, and offers information that will enable users to select an optimum solution. The quality indicators considered in conducting the comparative study are size, mass, the developed force and the energy-to-mass ratio. A method is proposed to determine the energy developed by the motors over the entire stroke; based on that, the energy-to-mass ratio is subsequently calculated. This indicator is a valuable tool made available to designers of wearable assistive devices. The conclusion yielded by the study asserts that while pneumatic muscles have larger radial and axial dimensions, they present benefits as to the developed forces and the energy-to-mass ratios.

Electrostatically actuated MEMS in the post-touchdown regime: The thin-dielectric limit and a novel reduced-order model for release dynamics

Microelectromechanical systems (MEMS) often make use of a type of plate-based electrostatic actuator that can, under certain conditions, come into contact with a dielectric-coated electrode. After this “touchdown,” the presence of a free boundary between the contacting and non-contacting regions of the plate induces strong nonlinearities in the system, significantly affecting its dynamics. In this paper we construct and analyze the mechanics of an idealized actuator after touchdown, focusing especially on the case where the dielectric is very thin and neglecting as many sources of nonlinearity as feasible in order to isolate the effect of contact. After characterizing the static equilibria, we construct a reduced-order dynamic model and investigate its application to the problem of vibration-assisted stiction repair, in which structural vibrations are employed to release the actuator from the touchdown configuration. This model has several features that are interesting in their own right, including a saddle–node bifurcation and finite-time blow-up. Our approach synthesizes concepts from configurational mechanics, fracture mechanics, and nonlinear dynamics, and serves as a blueprint for constructing more sophisticated models of touchdown dynamics that incorporate important practical effects.

Computational Modeling of Deep Tissue Heating by an Automatic Thermal Massage Bed: Predicting the Effects on Circulation.

Automatic thermal and mechanical massage beds support self-managed treatment, including reduction of pain and stress, enhanced circulation, and improved mobility. As the devices become more sophisticated (increasing the degrees of freedom), it is essential to identify the settings that best target the desired tissue. To that end, we developed an MRI-derived model of the lower back and simulated the physiological effects of a commercial thermal-mechanical massage bed. Here we specifically estimated the tissue temperature and increased circulation under steady-state conditions for typical thermal actuator settings (i.e., 45–65°C). Energy transfer across nine tissues was simulated with finite element modeling (FEM) and the resulting heating was coupled to blood flow with an empirically-guided model of temperature-dependent circulation. Our findings indicate that thermal massage increases tissue temperature by 3–8°C and 1–3°C at depths of 2 and 3 cm, respectively. Importantly, due to the rapid (non-linear) increase of circulation with local temperature, this is expected to increase blood flow four-fold (4x) at depths occupied by deep tissue and muscle. These predictions are consistent with prior clinical observations of therapeutic benefits derived from spinal thermal massage.

Active vibration control of large space structures: Modelling and experimental testing of offset piezoelectric stack actuators

To meet demanding mission objectives, most current satellites for Earth and Universe observation are equipped with large flexible appendages. However, due to the coupling between spacecraft rigid and elastic dynamics, unwanted elastic vibrations of such flexible elements may compromise the achievement of pointing and stability requirements. Therefore, control solutions aiming at avoiding instabilities and, at worst, the failure of the mission, are currently needed. In this scenario, growing interest has been recently devoted to Active Vibration Control (AVC) strategies relying on the use of smart materials. Among them, piezoelectric patches are the most studied and tested devices for both actuating and sensing purposes. This paper aims to contribute to this line of research by investigating a different type of actuator, namely an Offset Piezoelectric Stack Actuator (OPSA), to assess its performance in damping out elastic vibrations of large space structures. Moreover, special attention is devoted to compare OPSA performance with standard patch actuators behaviour. In order to develop the AVC system, an equivalent electro-mechanical coupled Finite Element (FE) formulation is implemented, integrating both sensors and piezo-stack elements on the passive hosting structure. The final structural model including both electrical inputs/outputs, as well as modified mass and stiffness due to the additional piezo devices, is then obtained. A parametric analysis is carried out to optimize the maximum control action exerted by the OPSA device. Finally, the OPSA numerical model is experimentally validated by mounting it on a cantilever plate, representative of a scaled solar panel. Experimental data are used not only to verify the device expected functioning, but also to tune the parameters in the OPSA FE model, which can be finally integrated in a planar satellite dynamics simulator to evaluate the AVC system efficiency when performing attitude manoeuvres.

Modeling and Parameter Sensitivity Analysis of Valve-Controlled Helical Hydraulic Rotary Actuator System

AbstractAs a type of hydraulic rotary actuator, a helical hydraulic rotary actuator exhibits a large angle, high torque, and compact structure; hence, it has been widely used in various fields. However, its core technology is proprietary to several companies and thus has not been disclosed. Furthermore, the relevant reports are primarily limited to the component level. The dynamic characteristics of the output when a helical rotary actuator is applied to a closed-loop system are investigated from the perspective of driving system design. Two main aspects are considered: one is to establish a reliable mathematical model and the other is to consider the effect of system parameter perturbation on the output. In this study, a detailed mechanical analysis of a helical rotary hydraulic cylinder is first performed, factors such as friction and load are considered, and an accurate dynamic model of the actuator is established. Subsequently, considering the nonlinear characteristics of pressure flow and the dynamic characteristics of the valve, a dynamic model of a valve-controlled helical rotary actuator angle closed-loop system is described based on sixth-order nonlinear state equations, which has never been reported previously. After deriving the system model, a sensitivity analysis of 23 main parameters in the model with a perturbation of 10% is performed under nine operating conditions. Finally, the system dynamics model and sensitivity analysis results are verified via a prototype experiment and co-simulation, which demonstrate the reliability of the theoretical results obtained in this study. The results provide an accurate mathematical model and analysis basis for the structural optimization or control compensation of similar systems.

A review of planetary roller screw mechanism for development and new trends

With the rapid development of all electric mechanical equipment in the fields of industrial application, aerospace engineering, and national defense, planetary roller screw mechanism has attracted much attention as a new type actuator of electro-mechanical actuator system. This report systematically reviews previous large number of researches as well as new advancements on five types of planetary roller screw mechanisms from both available literatures and studies presented. Firstly, the general structure, merits, limitations, and the application of five types of planetary roller screw mechanisms are summarized. Then, the development state of the planetary roller screw mechanisms is elaborated in the three aspects: parameter design, contact properties, and performance analysis. Common problems and tendencies of theoretical analysis and calculation models are analyzed. Finally, the research directions and methods in the future on planetary roller screw mechanism are discussed. Key technologies and research challenges are presented in terms of multi-pair dynamic contact and multi-body vibration of system, and the development prospects for various planetary roller screw mechanisms in all electric mechanical equipment are summed up.

Functionality Analysis of Electric Actuators in Renewable Energy Systems-A Review.

Various mechanical, hydraulic, pneumatic, electrical, and hybrid actuators can alter motion per the requirements of particular applications. However, except for electrical ones, all actuators are restricted due to their size, complex auxiliary equipment, frequent need for maintenance, and sluggish environment in renewable applications. This brief review paper highlights some unique and significant research works on applying electrical actuators to renewable applications. Four renewable energy resources, i.e., solar, wind, bio-energy, and geothermal energy, are considered to review electric actuators applicable to renewable energy systems. This review analyses the types of actuators associated with the mentioned renewable application, their functioning, their motion type, present use, advantages, disadvantages, and operational problems. The information gathered in this paper may open up new ways of optimization opportunities and control challenges in electrical actuators, thereby making more efficient systems. Furthermore, some energy-efficient and cost-effective replacements of convectional actuators with new innovative ones are suggested. This work aims to benefit scientists and new entrants working on actuators in renewable energy systems.

Geometric Solutions for General Actuator Routing on Inflated-Beam Soft Growing Robots

Continuum and soft robots can leverage complex actuator shapes to take on useful shapes while actuating only a few of their many degrees of freedom. Continuum robots that also grow increase the range of potential shapes that can be actuated and enable easier access to constrained environments. Existing models for describing the complex kinematics involved in general actuation of continuum robots rely on simulation or well-behaved stress-strain relationships, but the non-linear behavior of the thin-walled inflated-beams used in growing robots makes these techniques difficult to apply. Here we derive kinematic models of single, generally routed tendon paths on a soft pneumatic backbone of inextensible but flexible material from geometric relationships alone. This allows for forward modeling of the resulting shapes with only knowledge of the geometry of the system. We show that this model can accurately predict the shape of the whole robot body and how the model changes with actuation type. We also demonstrate the use of this kinematic model for inverse design, where actuator designs are found based on desired final robot shapes. We deploy these designed actuators on soft pneumatic growing robots to show the benefits of simultaneous growth and shape change.

Design and Fabrication of a Millimeter-Scale Rotary Actuator based on the Twisted Shape Memory Alloy (SMA) Wires

Shape memory alloy (SMA) has been widely used for many engineering and scientific applications, because it is largely deformable with high power density, and can be actuated easily by resistive heating. It is possible to reduce the size of the actuators by integrating or embedding SMA into the structures. While many applications have been reported regarding linear or bending actuators using the SMA wire, the development of a rotary actuator remains important and challenging for the engineering applications. Here, a new type of millimeter-scale rotary actuator is proposed based on the twisted SMA wires. SMA wires are twisted, folded, and integrated into the rotary actuator, and simple change of the twist direction enables the rotary actuator to rotate in the opposite direction. By integrating the oppositely twisted SMA wires into one rotary actuator unit, bidirectional rotary motions are possible. The actuation mechanism, design, and fabrication processes of the proposed rotary actuator are presented and demonstrated with its actuation performance. The fabricated actuators had average rotary working ranges from -38.68±4.92 deg to +45.37±8.79 deg in counterclockwise (CCW) and clockwise (CW) directions. This study will leverage the practical advances in the relevant engineering and scientific applications.

Dual-mode biomimetic soft actuator with electrothermal and magneto-responsive performance

Soft actuators with large deformation and high stability in response to multi-stimuli are highly demanded in biomimetic applications. However, most of the present actuators driven by a single stimulus often exhibit low performance and high energy consumption. In this work, a sandwich structural soft actuator (MPDMS/MXene/PTFE) which possesses electrothermal/magnetic coupling actuation is fabricated by combining magnetic NdFeB/Polydimethylsiloxane (MPDMS) composite layer, MXene film, and PTFE tape together. Due to the large difference of thermal expansion coefficient between MPDMS film and PTFE tape, the soft actuator shows a wonderful electrothermal actuation and the bending deformation can reach to as high as 353° under a 3 V power supply. The excellent electrical conductivity of MXene component endows the sandwich film with good thermal management performance, thus the soft MPDMS/MXene/PTFE sandwich films can be applied in the thermal treatment of body and thermal imaging. Most importantly, the soft actuator also exhibits a typical magnetic biomimetic actuation and the programmable actuation performance of the dragonfly actuator can be demonstrated by both experiments and finite element simulations. Eventually, the electrothermal/magnetic coupling actuation is successfully applied in an intelligent crawling robot to overcome the traditional inchworm movement simulation.

Implementation of ANN-Based Auto-Adjustable for a Pneumatic Servo System Embedded on FPGA.

Artificial intelligence techniques for pneumatic robot manipulators have become of deep interest in industrial applications, such as non-high voltage environments, clean operations, and high power-to-weight ratio tasks. The principal advantages of this type of actuator are the implementation of clean energies, low cost, and easy maintenance. The disadvantages of working with pneumatic actuators are that they have non-linear characteristics. This paper proposes an intelligent controller embedded in a programmable logic device to minimize the non-linearities of the air behavior into a 3-degrees-of-freedom robot with pneumatic actuators. In this case, the device is suitable due to several electric valves, direct current motors signals, automatic controllers, and several neural networks. For every degree of freedom, three neurons adjust the gains for each controller. The learning process is constantly tuning the gain value to reach the minimum of the mean square error. Results plot a more appropriate behavior for a transitive time when the neurons work with the automatic controllers with a minimum mean error of mm.

Design of Shape Memory Micro-Actuator Modules with Sequential Actuation

Shape memory alloy film-based micro-actuators have their behaviour controlled by a change in the thermomechanical stress that occurs in the bimorph - shape memory alloy film plus substrate assembly. The modification of the composition of the shape memory alloy leads to a change of the transformation temperature and implicitly of the temperature at which the stress change takes place in the bimorph. The design of micro-actuator blocks in which the composition and/or the temperature control mode of each micro-actuator in the block allows to obtain successive or sequential transformation sequences. The paper analyses the case of cantilever actuator modules with films of different compositions, deposited on the same substrate. It is highlighted how the composition of the alloy film with shape memory influences the modification of the curvature of bimorph cantilever type actuators in the studied block.

Evaluation of two complementary modeling approaches for fiber-reinforced soft actuators

Although robots are increasingly found in a wide range of applications, their use in proximity to humans is still fraught with challenges, primarily due to safety concerns. Roboticists have been seeking to address this situation in recent years through the use of soft robots. Unfortunately, identifying appropriate models for the complete analysis and investigation of soft robots for design and control purposes can be problematic. This paper seeks to address this challenge by proposing two complementary modeling techniques for a particular type of soft robotic actuator known as a Fiber-Reinforced Elastomeric Enclosure (FREE). We propose that researchers can leverage multiple models to fill gaps in the understanding of the behavior of soft robots. We present and evaluate both a dynamic, lumped-parameter model and a finite element model to extend understanding of the practicability of FREEs in soft robotic applications. The results of experimental simulations using a lumped-parameter model show that at low pressures FREE winding angle and radius change no more than 2%. This observation provided confidence that a linearized, dynamic, lumped-mass model could be successfully used for FREE controller development. Results with the lumped-parameter model demonstrate that it predicts the actual rotational motion of a FREE with at most 4% error when a closed-loop controller is embedded in the system. Additionally, finite element analysis was used to study FREE design parameters as well as the workspace achieved with a module comprised of multiple FREEs. Our finite element results indicate that variations in the material properties of the elastic enclosure of a FREE are more significant than variations in fiber properties (primarily because the fibers are essentially inextensible in comparison to the elastic enclosure). Our finite element analysis confirms the results obtained by previous researchers for the impact of variations in winding angle on FREE rotation, and we extend these results to include an analysis of the effect of winding angle on FREE force and moment generation. Finally, finite element results show that a 30^{circ } difference in winding angle dramatically alters the shape of the workspace generated by four FREEs assembled into a module. Concludingly, comments are made about the relative advantages and limitations of lumped-parameter and finite element models of FREEs and FREE modules in providing useful insights into their behavior.

Mode shifting shape memory polymer and hydrogel composite fiber actuators for soft robots

Soft robotics is a promising new field offering robot systems that mimic the versatility and complexity of movement and propulsion seen in natural organisms. Such systems require complex actuation including length expansion/contraction, bending and torsion. To date, such actuators have been configured individually. Here, it is shown that composite fibers formed from a shape memory polymer and a thermo-sensitive hydrogel could be configured into any one of the tensile, torsional and flexural actuators. Furthermore, the programmed mode of actuation could be thermally erased and the same fiber re-programmed into a different type of actuator. The fibers were prepared from poly(N-isopropylacrylamide) with polycaprolactone and the fiber composition was tuned to optimize both shape fixity and the degree of actuation. The fibers could be programmed by heating to 60 ℃ and then cooled under tensile, flexural or torsional load. The fiber was then conditioned by immersing in water at room temperature which induced swelling of the hydrogel phase and shape deformation. The pre-programmed shape of the fiber was then restored when the fiber was heated at 35 ℃ in water to de-swell the thermo-sensitive poly(N-isopropylacrylamide) hydrogel. Reversible actuation was observed through multiple cycles of heating and cooling. The optimized fibers generated torsional strokes of 10 turn/m; bending curvature changes of 0.4 mm−1 or tensile strokes of up to 92%. The composite fibers offer a convenient means for generating a variety of different actuation types for soft robotics.

A droplet-driven micro-surfboard with dual gradients for programmable motion

Self-propelled autonomous devices have great significance in energy, environment, and biomedical engineering, and thus vast achievements have been made in recent years. However, conventional propulsion often requires special chemicals or external energy, limiting their practical applications due to environmental pollution and energy waste. In this work, inspired by the character of a water strider on the water surface, a novel droplet-driven micro-surfboard (DDMS) is developed via femtosecond laser micro/nano fabrication, which can be driven in a green and controllable way. The DDMS is composed of a superhydrophobic sheet with superhydrophilic wedgy grooves. The droplet is put on superhydrophilic wedgy grooves to enter the water and form a jet, which further facilitates the directional motion of the DDMS. Also, a type of actuator with three superhydrophilic wedgy grooves is designed successively to achieve turn direction, which completes the programable motion by adding droplets to the three channels. Finally, an actuator with circular water storage area and a symmetrical vane-like rotating device with two superhydrophilic channels are developed, realizing long-distance and rotational motions. This work provides new insights into pollution-free autonomous devices and shows the great potential of droplet-driven autonomous devices in the fields of micromechanics and intelligent systems.

Active Load Sensitive Electro-Hydrostatic Actuator on More Electric Aircraft: Concept, Design, and Control

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.

Analytical Design of a Novel Clamp-On Type Actuator Coil for Magnetic Pulse Forming of Tubular Structures

Electromagnetic forming of tubular workpieces using a pulsed power source is gaining acceptance in the non-conventional metal forming area. It finds extensive use in various industries for metal joining, electromagnetic crimping of wires, tube bulging for manufacturing of automotive parts, etc. This paper describes an analytical design and electromagnetic analysis of a novel clamp-on type uniform pressure electromagnetic actuator that works based on the primary induced currents. A fast analytical method has been developed and used for solving the electromagnetic(EM) fields instead of the conventional coupled numerical models based on Finite Element Method(FEM) technique. The agile manufacturing of the workpieces requires the workpiece assembly to be easily removed and replaced. However, the finished assembly is such that it is impractical to remove it out of the conventional helical actuator in most of the industrial applications. The designed actuator offers a substantial improvement over the conventional helical actuators in terms of flexibility of operation, reduced stress on the coil, reusability, robustness, and a uniform pressure profile on the workpiece. In addition, the paper also identifies important process parameters involved in the novel actuator design. It also develops an analytical model to compare the performance of the novel proposed actuator with a conventional helical actuator for a tube deformation process.

Nanocomposite electrodes using highly conductive sub-millimetre-long single-walled carbon nanotubes pasted with PEDOT:PSS and high-performance actuators

We describe new nanocomposite electrodes and actuators using highly conductive single-walled carbon nanotubes (<1 mm in length) fabricated using the ‘super-growth’ method (SG-SWCNT) pasted with poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and combined with electrostatic double-layer capacitors (EDLCs) and faradaic capacitors (FCs). The electromechanical/chemical properties of the SG-SWCNT/PEDOT:PSS/ionic liquid (IL) electrode and actuator were compared with those of the SG-SWCNT/IL electrode and actuator. The SG-SWCNT/PEDOT:PSS/EMI[C(CN)3] electrode (volume resistivity; 4.26 Ω cm, surface resistivity; 0.55 Ω/sq. and conductivity; 235 S/cm) was a more conductive electrode than the equivalent SG-SWCNT/EMI[C(CN)3] electrodes (36.0 Ω cm, 2.37 Ω/sq. and 28.0 S/cm). This is thought to be a result of the synergy between SG-SWCNT and PEDOT:PSS. The maximum strain of the SG-SWCNT/PEDOT:PSS/EMI[B(CN)4] actuator ranged from 0.39% to 1.88%, which is approximately 1.6–7.5 times larger than that of the SG-SWCNT/EMI[B(CN)4] actuator. The actions of the hybrid actuators differed from those of the SG-SWCNT/IL actuators, which function only as EDLC units. A kinetic model featuring double-layer charging successfully simulated the frequency-dependent displacement responses of both types of actuators. The use of a PEDOT:PSS polymer promotes higher conductivity, specific capacitance, and strain, which is thought to originate in synergy between SG-SWCNT and PEDOT:PSS. Thus, flexible robust films that exploit this synergy are likely to be useful as actuator components in energy conversion and wearable devices.

Use of Magnetomechanical Effect for Energy Harvesting and Data Transfer.

The presented paper describes a method where, with the use of a dedicated SMART Ultrasonic Resonant Power System (SURPS) developed by the authors, a power and data transfer between two devices can be performed at the same time. The proposed solution allows power to be supplied to the sensor, located in a hardly accessible place, with simultaneous data transfer in a half-duplex way (e.g., “question–response”). The power transmission mechanism is based on the excitation of a construction with a sinusoidal wave, with an actuator transforming this wave into useful, electrical power through a harvester device. Data transfer is achieved with the use of the F2F (Frequency Double Frequency) procedure, which is a kind of frequency modulation. To receive optimized parameters for each construction, an original software is developed, which allows the selection of the proper type of actuator, modulation, and frequency.