Cylindrical Actuator Research Articles

Simplified Polynomial-asymptotic-distribution Actuator Disc (SPAD) method for wind turbine wake simulation based on k-[formula omitted]-[formula omitted] turbulence model

In large wind farms, wake effect has a negative impact on the annual production of wind turbines. As a result, wind turbine wake simulation is important for wind farm micro-sitting to minimize power loss and maximize energy production. Coupled with Reynolds Averaged Navier–Stokes turbulence model, Simplified Uniform-distribution Actuator Disc method is the most widely-used rotor model for wake simulation in engineering practice. The conventional simplified uniform-distribution actuator disc models suffer discrepancies of wake velocity prediction compared with the measurements in the near wake region. The novelty of the current research is to propose a Simplified Polynomial-asymptotic-distribution Actuator Disc method based on k−ϵ−fP turbulence model for cylindrical actuator disc cell region with finite thickness, which is simple for implementation and improves the accuracy of wake simulation compared with conventional method. The proposed method conforms to momentum conservation and is as simple as conventional method because of its polynomial formulation and no requirement for aerodynamics data in Generalized Actuator Disc model. From the verification and validation cases, it can be found that the proposed model has better agreement with both high-fidelity actuator line model and the field test measurements from Lillgrund wind farm compared with conventional model. The proposed actuator disc model has the potential to be applied to the micrositting of large offshore wind farms in the future.

Design and Implementation of a Hybrid-Driven Soft Robot

Currently, soft robots alone cannot obtain the same operating speed as rigid robots, while rigid robots are not safe enough for human-robot interaction. To address this problem, this paper describes a hybrid robot system that combines both rigid and flexible systems for unknown domain exploration. The system consists of a four-wheeled robot chassis and a cylindrical pneumatic soft actuator, and finally, a computer is used to coordinate and control both. The hardware of the robot system is designed, a bending motion model is proposed, and SOFA framework is used to carry out finite element simulation (FEM) to verify the reasonableness of the design; linear motion speeds of up to 0.5 m/s, higher than the existing soft robots investigated, were verified experimentally separately after carrying the new module, and steering ability was retained; and the robot carrying the navigation module is verified to have a certain map building and localization function through the construction of the simultaneous localization and mapping (SLAM) experimental platform. The hybrid robot introduced in this paper can move quickly on flat terrain and can use its soft part to avoid wear and tear.

Numerical and experimental assessment of tilted-helical fiber orientation effects on deformation of pneumatic soft actuators

Pneumatic actuation of fiber-reinforced soft-material slender structures, and specifically inflatable cylinders, plays a key role in soft robotics, particularly for generating sought deformations in terms of, e.g. elongation, expansion, torsion, and bending. Fiber-reinforced tubes were widely investigated, in particular by considering regular helical patterns for the fibers, and multiple sets of fibers were introduced for achieving relatively richer deformations such as coiling (i.e. combined bending and torsion). However, coiling can be obtained even by introducing a single tilted-helical fiber, thus potentially simplifying actuator design and implementation. Therefore, in this study, we numerically investigated the effect of fiber orientation on the coiling behavior of tilted-helical fiber-reinforced cylindrical actuators. Specifically, we used finite element numerical simulations to determine the effect of fiber pitch and tilt angle on the curvature and twist angle of an inflated cylindrical actuator, and we assessed numerical results based on corresponding experiments. Finally, we addressed a preliminary design chart based on the inverse map linking coiling to the corresponding pitch and tilt angle. Our results take an initial step for the design of tilted-helical fiber-reinforced actuators, with potential application to a wider class of inflatable soft actuators to program a desired coiled configuration through the integration of a single tilted-helical fiber.

3D-printing allows for fluid-controlled linear actuators with unconventional shapes

BackgroundPneumatic actuators are widely used in applications like (medical) robots, or prostheses. Pneumatic actuators require a complex manufacturing process and are produced in standardized dimensions to reduce costs. Over the last decade 3D-printing has emerged as a cost-effective and efficient production method in medical applications. 3D-printing can also function as a cost-efficient alternative production method for pneumatic actuators. ObjectiveThe goal of this research is to study the possibility of creating a pneumatic linear actuator with 3D-printing. Furthermore, the aim is to use the advantage of 3D-printing to create pneumatic actuators with non-circular cross-sections. MethodologyTo evaluate the performance of a 3D-printed pneumatic actuator, a test setup was designed and built to measure the leakage and sliding friction force. Furthermore, two pneumatic actuators with a non-conventional cross-sectional shape were designed and their performance was tested and compared with a 3D-printed cylindrical pneumatic actuator, since these tests only ran once, the results are more a guideline. During the manufacturing of the cylinders, no post-processing techniques were used. ResultsThe functioning of a 3D-printed circular pneumatic actuator was proven with low static leakage rates of 2.5%, low dynamic leakage rates of approximately 1%, and a maximum friction force of ▪. Furthermore, the results show that it is possible to print functioning pneumatic cylinders with a non-cylindrical concave cross-section. The non-conventional cylinders were tested up to ▪ with maximum dynamic leakage of ▪. ConclusionThis study demonstrates a method to create functional pneumatic linear actuators with 3D-printing. It was possible to create 3D-printed actuators with a conventional shape, e.g. circular and unconventional shapes e.g. stadium/oval shape and a kidney shape. The leak rates for conventional and unconventional shapes were in the same range. This opens up the world for more design freedom in pneumatic actuators.

Development of Cylindrical Linear Actuator for Vertical Transfer: Fundamental Consideration of Effect of Shape on Thrust Characteristics

Development of Cylindrical Linear Actuator for Vertical Transfer: Fundamental Consideration of Effect of Shape on Thrust Characteristics

A multi-electrode electroelastomer cylindrical actuator for multimodal locomotion and its modeling

Dielectric elastomer actuators (DEAs) have received widespread attention in human-robot interaction and biomedical engineering due to their merits of large deformation, fast response, and excellent biocompatibility. The cylindrical DEA is one of the preferred structures, combining flexibility and compactness. However, the inherent non-linear behavior between the voltage and the actuator makes predicting the output performance during the design process difficult and encumbers its application, especially for multiple degrees of freedom. Herein, a dielectric elastomer spring-roll bending actuator capable of multimodal spatial locomotion using three pairs of electrodes is proposed in this paper. The electromechanical coupling behavior of the actuator under unidirectional bending deformation is described by analyzing the stress process between the spring and the film. The system's damping and excitation frequency relationship is obtained via a semi-analytical method. The experimental results validate the actuator design and show good consistency with the theoretical model. A prototype soft robot capable of running and turning is successfully demonstrated. The actuator also achieves various spatial trajectory paths via the cooperation between electrodes. Thus, the proposed scheme and modeling shed new light on the design and control of dielectric elastomers for multimodal deformation.

Soft End Effector Using Spring Roll Dielectric Elastomer Actuators

Dielectric elastomer actuators (DEAs) offer robust, high-energy-density solutions for soft robotics. The proposed end effector consists of three spring roll configuration DEAs, each acting as a robotic finger, using a 3M VHB-F9473PC adhesive membrane. Spring roll DEAs can be designed to achieve highly specialised actuations depending on the electrode patterning and structural supports. This allows a spring roll DEA-based soft end effector to be tailor-made by simply altering the electrode patterning. The lateral force, bending angle and response time of the actuator are measured experimentally and compared with the predictions of an analytical model. The cylindrical actuator measures 70 mm in length and 15 mm in diameter and achieves a lateral force of 30 mN, a bending angle of 6.8° and a response time of ≈1 s. Spring roll configuration DEAs are shown to reduce the effects of viscoelasticity seen in the membrane, making the actuator more controllable at higher voltages. The dielectric constant of the membrane is shown to be a limiting factor of actuation, with a decrease in dielectric constant resulting in larger actuation. The end effector successfully grips numerous light objects for extended periods, showing the applicability of spring roll DEAs for soft end effectors.

Creation of asymmetrically constructed cylindrical liquid crystal actuators with controllable thermal rolling

AbstractIn this study, we demonstrate a predesigned method for the fabrication of rolling direction controllable asymmetrically constructed cylindrical liquid crystal elastomers (CLCEs). Cylindrical liquid crystal elastomers were fabricated by Michael addition, and the synthesized CLCE prepolymers were then uniaxially stretched with a twisted angle and fixed with UV polymerization. The synthesized asymmetrically constructed CLCEs reveal that the gravity center shifts from the geometric center, showing thermal actuation. The location of the asymmetric gravity center of each of the synthesized CLCEs was estimated. Based on the location of the gravity center, rolling direction control of the synthesized CLCEs was achieved. For one synthesized CLCE, both clockwise and counterclockwise rolling are possible depending on the location of the gravity center when it was placed on a hot plate. The creation of direction controllable cylindrical thermally sensitive LCE actuators is a novel skill, which opens a new avenue for the fabrication of smart functional materials.

Design and Analysis of Mechanical Characteristics of EAP Flexible Drivers

Electroactive polymer(EAP) is a “smart material” with high energy density, high electromechanical energy conversion efficiency, simple structure, good adaptability to the working environment, etc. It can be made into various shapes to realize flexible drivers. At present, the common EAP actuator is mainly composed of EAP film wound on a spring, and the output performance of this type of actuator is related to the spring stiffness, film prestretching rate, voltage, and other factors. Its working process is actually an electromechanical coupling process. In this paper, two types of cylindrical actuators are designed and tested. The electromechanical coupling mathematical model is constructed to simulate the driver. According to the experimental and simulation results, the relationship between the output displacement and elongation strain of EAP actuator and voltage, spring stiffness, and tensile rate is analyzed. It provides a reference and basis for the design of similar actuators.

Fabrication and performance analysis of high-performance cylindrical ionic polymer-metal composite actuators with various diameters

Ionic polymer-metal composites (IPMCs) are electroactive polymer actuators that have been used as artificial muscles and have broad application prospects. In order to further improve the actuation performance of cylindrical IPMCs, Nafion rods with different diameters were prepared by extrusion process, and cylindrical IPMCs with high-quality Pt electrode layers were prepared by electroless plating in this study. The electrochemical properties and actuation performance of cylindrical IPMCs with various diameters were investigated. The tests show that the prepared cylindrical IPMCs have excellent electromechanical properties. As diameter increases, the blocking force and counter back-relaxation ability both increase significantly. Furthermore, the IPMCs with diameter of 3.0 mm under a DC voltage exhibits a superior blocking force (323.9 mN) and excellent power density (up to 139.41 W m−3). Moreover, the thick cylindrical IPMC can lift objects 400 times its weight, demonstrating exceptional load capacity, which shows great prospect of realizing artificial muscles.

Free radial oscillations of an actuated cylindrical tube

This work investigates the free radial oscillations of an electrically actuated cylindrical tube. Classical Knowles’ tube problem is explored here with the application of an external electric field. One of the prime objectives is to study the effect of sudden pressure removal from the cylindrical actuator. We attempt to correlate our problem physiologically with an arterial tissue actuation. The tube is introduced to an electrical actuation with an externally applied electric field and is subjected to a sudden pressure which is removed instantly to explore the purely free radial oscillations. Generally, such kind dynamic effects are neglected in designing cylindrical actuators. The dielectric cylindrical tube is assumed to be incompressible, isotropic, and infinite. The obtained results assert that the application of an external electric field reduces the amplitude of the radial oscillations and thus makes the tube contract. Essentially, the actuation is elevating the stiffness of the tube. A similar effect is also observed in the blood vessels, wherein the electric signaling helps the vessels to contract. We propose a complete analytical solution approach that is highly significant in designing cylindrical muscle actuators for various futuristic applications in the biomimetic and medical field.

Theoretical Analysis of Active Flow Ripple Control in Positive Displacement Pumps

Positive displacement machines present a well-known major drawback that is the oscillation in delivered flow rate. This paper presents two active solutions for reducing the flow ripple generated by a pump with an external device actuated by means of a piezo-stack actuator. The work is focused on a theoretical analysis, with the aim of collecting information about the performance of the solutions proposed and their main advantages and drawbacks. The active methods proposed involve a cylindrical actuator connected to the delivery line of the pump. The piston could be actuated directly by a piezo-stack actuator or by a differential pressure modulated by a proportional piezo actuated valve. The actuators were modelled and a control algorithm based on Least Mean Square algorithm was used to achieve the adaptability for both systems at different operating conditions. The developed mathematical model permits to define the great potential of these solutions that can drastically reduce the flow ripple. The first architecture presented resulted as the best solution, while the second one allowed reduction of the production cost.

Suitability of Different Analytical Derivations of Electrically Induced Stress States in Planar and Cylindrical Dielectric Elastomer Actuators.

Dielectric elastomers (DE) belong to a very performant and efficient class of functional materials for actuators, while being compliant, low-weight and silent, they offer high energy efficiencies and large deformations under an applied electric field. In this work, a comparison of different approaches to derive expressions for the electrically induced stress states in dielectric materials is given. In particular, the focus is on three different ways to analytically describe stress states in planar actuator setups and to show how they are connected to each other regarding their resulting deformations. This is the basis to evaluate the suitability of these approaches for cylindrical actuator geometries together with exemplary calculations for concrete use cases. As an outcome, conclusions on the suitability of the different approaches for certain actuator setups are drawn. In particular cylindrical actuator geometries are taken into account and a recommendation on which approach is useful to describe a certain actuator effect is given.

Modeling and analysis of an electro-magneto-elastic rotating cylindrical tube actuator

This paper presents the static modeling and analysis of a novel cylindrical tube actuator subjected to a rotation about longitudinal axis with an internally applied air pressure under an electromagnetic field. The current tube actuator belongs to a smart actuator category and is made of an electro-magneto-active polymer filled with a particular volume fraction of suitable fillers. A continuum mechanics-based electro-magneto-mechanical model is developed to predict the response of the actuator for a combined pressure and electromagnetic field loading. To validate the same, the model is compared with the outputs of an existing spring roll actuator. Parametric studies are subsequently performed for varying input pressure, electric field, magnetic field, fillers content, and actuator’s rotational speed. The output sensitivity in terms of strain intensity at inner and outer surfaces of the actuator is also checked at different controlling inputs. In addition, various electro-magneto-mechanical instability curves are drawn to examine the critical inflation of the tube actuator. In general, the developed model provides initial steps toward the modern actuator designs for applications where a precise control with high load-carrying capability of the actuator plays a significant role.

A Pneumatic Novel Combined Soft Robotic Gripper with High Load Capacity and Large Grasping Range

Pneumatic soft grippers have been widely studied. However, the structures and material properties of existing pneumatic soft grippers limit their load capacity and manipulation range. In this article, inspired by sea lampreys, we present a pneumatic novel combined soft gripper to achieve a high load capacity and a large grasping range. This soft gripper consists of a cylindrical soft actuator and a detachable sucker. Three internal air chambers of the cylindrical soft actuator are inflated, which enables them to hold objects. Under vacuum pressure, the cylindrical soft actuator and the detachable sucker can both adsorb objects. A finite element model was constructed to simulate three inflation chambers for predicting the grasping range of the cylindrical soft actuator. The validity of the finite element model was established by an experiment. The mechanism of holding force and adsorption force were analyzed. Several groups of experiments were conducted to determine adsorption range, holding force, and adsorption force. In addition, practical applications further indicated that the novel combined soft gripper has a high load capacity (10.85 kg) at a low pressure (16 kPa) and a large grasping range (minimum diameter of the object: d = 6 mm), being able to lift a variety of objects with different weights, material properties, and shapes.

Evaluation of Cylindrical Asymmetric Surface Dielectric Barrier Discharge Actuators for Surface Decontamination and Mixing

Surface dielectric barrier discharge (SDBD) was used to evaluate cylindrical plasma actuators for inactivation of Salmonella enterica. A cylindrical SDBD configuration was evaluated to determine if the inherent induced body force could be leveraged to impel plasma species, such as reactive oxygen and nitrogen species (RONS), as an apparatus to sterilize surfaces. The cylindrical structure is evaluated in this study to observe whether an increase in mixing is possible to efficiently distribute the plasma species, thereby improving bacterial inactivation efficiency. The increase in induced airflow of SDBD actuators with increased numbers of electrodes correlates with increased bacterial inactivation. These results suggest that improving the particle velocity, airflow mixing tendencies, and plasma volume for the same power inputs (same net power to the actuators) results in increased surface decontamination efficiency.

A Virtual Work Model for the Design and Parameter Identification of Cylindrical Pressure-Driven Soft Actuators

Abstract In this paper, we derive a model based on the principle of virtual work to describe the deformations of cylindrical pressure-driven soft actuators with four types of fiber reinforcement and with externally applied forces. Such cylindrical actuators are often used as the basis for multi-chamber soft robotic systems, for example, bending actuators. In the virtual work model, each type of reinforcement leads to particular geometric constraints; the energy of the stretched material is determined by the Yeoh material model. Finally, the stretch of the actuator is solved numerically by a minimization problem. The virtual work model yielded only little deviations of the predicted stretch relative to finite element simulations in abaqus. The key contribution of the virtual work model is improved parameter identification for the modeling of cylindrical soft actuators, as it illustrates the possibility to distinguish between material-dependent behavior and geometry-dependent behavior of these actuators. Also, the virtual work model is applicable in the design process of the investigated actuators. We demonstrate that an optimization of the actuator’s inner and outer radii and of its fiber angle, respectively, is possible and we derive design rules including criteria for the choice of fiber reinforcement.

The Prospect of Combining a Point Absorber Wave Energy Converter with a Floating Offshore Wind Turbine

With recent advances in offshore floating wind and wave energy technology, questions have emerged as to whether the two technologies can be combined to reduce their overall levelised cost of energy. In this paper, the potential for combining a floating offshore wind turbine to a point absorbing wave energy converter is investigated. The focus of the investigation is how much power might be produced by a combined floating wind and wave energy converter system, and the resultant changes in motion of the floating wind platform. A model for the combined wave and wind system is developed which uses the standardised NREL OC3 5 MW spar type wind turbine and a cylindrical buoyant actuator (BA), which is attached to the spar via a generic wave power take-off system (modelled as a spring-damper system). Modelling is conducted in the frequency domain and the tests span a wide range of parameters, such as wave conditions, BA sizes, and power take-off coupling arrangements. It is found that the optimal (with respect to power production) BA size is a draft and radius of approximately 14 m. It is found that this BA can theoretically produce power in the range of 0.3 to 0.5 MW for waves with a significant wave height of 2 m, and has the potential to produce power greater or near to 1 MW for waves with a significant wave height of at least 3 m. However, it is also found that, in terms of the relative capture width, significantly smaller BAs are optimal, and that these smaller BA sizes less significantly alter the motion of the floating wind platform.

Compact Pneumatic Clutch With Integrated Stiffness Variation and Position Feedback

Stiffness variation and real-time position feedback are critical for any robotic system but most importantly for active and wearable devices to interact with the user and environment. Currently, for compact sizes, there is a lack of solutions bringing high-fidelity feedback and maintaining design and functional integrity. In this work, we propose a novel minimal clutch with integrated stiffness variation and real-time position feedback whose performance surpasses conventional jamming solutions. We introduce integrated design, modeling, and verification of the clutch in detail. Preliminary experimental results show the change in impedance force of the clutch is close to 24-fold at the maximum force density of 15.64 N/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . We validated the clutch experimentally in (1) enhancing the bending stiffness of a soft actuator to increase a soft manipulator's gripping force by 73%; (2) enabling a soft cylindrical actuator to execute omnidirectional movement; (3) providing real-time position feedback for hand posture detection and impedance force for kinesthetic haptic feedback. This manuscript presents the functional components with a focus on the integrated design methodology, which will have an impact on the development of soft robots and wearable devices.

Research and analysis of resonant and stiffness of cylindrical dielectric elastomer actuator

Dielectric elastomer actuators draw great interest in the emerging technology of soft actuations. The drifting of resonance frequency and variable stiffness are commonly existed in soft actuations. This work studied the dynamic performances of a cylindrical dielectric elastomer actuator with coupled loads of tensile forces and variable voltages. The equation of motion for the axial are derived from Euler–Lagrange equation and are reduced into linear ordinary differential equations by the weighted average equivalent linearization method. It is found that the resonant frequency as well as the dynamic behavior can be tuned by variable electrical stimulus on the actuator. An analytical solution of the resonant frequency and equivalent stiffness have been derived in this paper, and have been verified by numerical simulations and experimental measurements. By changing the excitation voltages, the stiffness can be tuned as variable and controllable, which paves the way for future applications of the DE actuators with better performances and resilience.