Cylindrical Actuator Research Articles

Design of a Dielectric Elastomer Cylindrical Actuator With Quasi-Constant Available Thrust: Modeling Procedure and Experimental Validation

A novel design for a dielectric elastomer (DE) actuator is presented. The actuator is obtained by coupling a cylindrical DE film with a series of slender beams axially loaded beyond their buckling limit. Similar to previous published solutions, where different actuator geometries were coupled with compliant mechanisms of various topologies, the elastic beams are designed so as to provide a suitable compensating force that allows obtaining a quasi-constant available thrust along the entire actuator stroke. Whilst the elastic beam are sized on the basis of an analytical procedure, the overall system performance is evaluated by means of multiphysics finite element (FE) analysis, accounting for the large deflection of the buckled-beam springs (BBSs) and for the DE material hyperelasticity. Numerical and experimental results are finally provided, which demonstrate the prediction capabilities of the proposed modeling method and confirm that well-behaved cylindrical actuators can be conceived and produced.

Numerical Calculation of the Magnetic Field and Force in Cylindrical Single-Axis Actuator

This paper investigates a kind of cylindrical linear single-axis actuator that is used in the magnetic levitation stage to provide fine movement. The magnetic flux density distribution due to the permanent magnet is determined using the surface charge method, and the magnitude of force generated by the actuator is calculated using the Lorentz force equation. Both of them can be solved by numerical integration. The results are verified by measurements. The magnetic force components are fitted as an analytical style that can be used in the real-time controlling of this actuator for the magnetic levitation stage.

Influence of segmentation of ring-shaped NdFeB magnets with parallel magnetization on cylindrical actuators.

This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines.

Characteristic analysis of two-degree-of- freedom cylindrical actuator

This paper presents the characteristic analysis of the two-degree-of-freedom cylindrical actuator that can move in rotary and linear direction. The actuator uses the permanent magnet that is magnetized in axial direction so that the polarity in rotary and linear direction is generated alternately. When the rotary coil or the linear coil is excited, the mover moves by the principles of PMSM or PMLSM, respectively. As a result, the torque and the thrust are almost out of interference. It was confirmed that the actuator can move in rotary and linear motion independently. Moreover, the iron loss of the mover is smaller than that of the stator in rotary and linear motion, and the hysteresis loss is much larger than the eddy current loss.

Electromechanical response and failure modes of a dielectric elastomer tube actuator with boundary constraints

As a widely used configuration for dielectric elastomer (DE) actuators, DE tube actuators (or cylindrical actuators) are also found to be susceptible to electromechanical instability (EMI), which may lead to a premature electrical breakdown (EB), and inhibit the potential actuation of DE actuators. This work investigates the electromechanical response of a DE tube actuator with and without boundary constraints to demonstrate an alternative to avoid EMI while achieving large actuation. Our simulation results based on the Gent strain energy model show that the EMI of a DE tube actuator can be eliminated, and larger actuation deformation can be achieved by applying boundary constraints. As a result of these constraints, consideration is also given to the possible mechanical buckling failure that may occur. Mechanisms of possible failure modes of constrained and unconstrained DE tube actuators, such as electromechanical instability, electrical breakdown and mechanical buckling, are elucidated. This paper should provide better theoretical guidance on how to improve the actuation performance of DE actuators, thus leading to the optimal design of DE-based devices.

Piezothermoelastic behavior of multilayered pyroelectric cylindrical actuators with weakly conducting interfaces resting on elastic foundations

An exact solution is obtained for multilayered pyroelectric cylindrical (MPC) actuators with weakly conducting interfaces subjected to thermo-electro-mechanical loading. The outer surface of the composite cylindrical actuator is supported by a Winkler-type elastic foundation. At the interface, all the thermal and mechanical quantities as well as the normal electric displacement are assumed to be continuous but the electric potential is discontinuous. The temperature fields are obtained by the transfer matrix method and the piezothermoelastic fields are developed by the state space method combined with the Cayley–Hamilton theorem. Numerical results are presented graphically to show the effects of the elastic foundation, interfacial parameters and heat transfer coefficient on the piezothermoelastic behavior of MPC actuators.

3P2-K06 空気圧アクチュエータによる拮抗冗長ロボットアームの手先位置制御(パラレルロボット・メカニズム)

This paper reveals that the tip trajectory of a three degrees-of-freedom robotic arm satisfies rectilinear locus in the two dimensional plane, even though the command to the robot corresponds to a step input of xy-coordinates. First, we describe a simple model of a redundant three-joint manipulator by means of Lagrangian analysis. By using this manipulator model, we clearly indicate that the tip position control of the robot can be easily achieved by a PID controller designed for the redundant mechanism. In addition, this manuscript compares xy-trajectory of the tip of robot between a pneumatic actuator and a conventional motor joint mechanism. This pneumatic cylindrical actuator is placed at both sides of a joint with antagonistic location. Finally, the tip position trajectory moves according to rectilinear trajectory on xy-plane in both cases of gravity and non-gravity situation. Thus, we can claim that the antagonistic pneumatic actuator mechanism is most suitable for the accurate and stable position control of the redundant robotic manipulator.

Characteristics of Dielectric Electroactive Polymer Cylindrical Actuator under Voltage Activation

The dynamic and static characteristics of a dielectric electroactive polymer(EAP) actuator is the foundation for its reasonable operation and optimizing design. The geometrical deformation of the cylindrical actuator can be depicted through constructing a geometry model; furthermore, the dynamic formulation for the axial linear movement is also deduced based on the electromechanical coupling equations of EAP. The relation curve between the displacement and voltage of the cylindrical actuator, obtained through numerical calculation, reveals that the coating method for the outer and inner layer of the flexible electrodes can influence the actuator displacement. Based on the relationship between voltage and displacement, the main failure forms of the actuator are also discussed. Modifying the one-time-constant viscoelastic model, based on the neo-Hookean springs, to two-time-constant model, the two models are applied to study the dynamic responses of the actuator excited by step and periodic voltage. Comparative analysis of theoretical calculation and experiment results shows that the two-time-parameter viscoelastic model can describe the dynamic displacement more accurately. The displacement amplitude of actuator, under periodic voltage excitation, will be significantly reduced through increasing frequency, while the vibration center offset and vibration amplitude reduced due to "excitation dead zone".

Dielectric elastomer actuators used for pneumatic valve technology

Dielectric elastomer actuators have been investigated for applications in the field of pneumatic automation technology. We have developed different valve designs with stacked dielectric elastomer actuators and with integrated high voltage converters. The actuators were made using VHB-4910 material and a stacker machine for automated fabrication of the cylindrical actuators. Typical characteristics of pneumatic valves such as flow rate, power consumption and dynamic behaviour are presented. For valve construction the force and stroke parameters of the dielectric elastomer actuator have been measured. Further, benefits for valve applications using dielectric elastomers are shown as well as their potential operational area. Finally, challenges are discussed that are relevant for the use of elastomer actuators in valves for industrial applications.

Design for New Actuator Based on Electroactive Polymer

Dielectric elastomer is a kind of electroactive polymer material with optimal performance. As actuator material, dielectric elastomer has shown a good prospect. Based on studying the principle of electroactive polymer, a new type of cylindrical actuator was designed. Its 3-D figure and 2-D dimension drawing was finished by UG software. The animation simulation of the actuator was studied. The simulation results verified the feasibility of design scheme. Electroactive polymer will have broad application prospects in the field of actuator.

Characterization and application of shape-changing panels with embedded rubber muscle actuators

Cylindrical soft actuators efficiently convert fluid pressure into mechanical energy and thus offer excellent force-to-weight ratios while behaving similar to biological muscle. McKibben-like rubber muscle actuators (RMAs) were embedded into neat elastomer and act as shape-changing panels. The effect of actuator spacing and modeling methods on the performance of these panels was investigated. Simulations from nonlinear finite element models were compared with results from test panels containing four RMAs that were spaced 0, 1/2, 1, and 1.3 RMA diameters apart. Nonlinear ‘laminated plate’ and ‘rod & plate’ finite element (FE) models of individual (non-embedded) RMAs and panels with embedded RMAs were developed. Due to model complexity and resource limitations, several simplified 2D and 3D FE model types, including a 3D ‘Unit Cell’ were created. After subtracting the ‘activation pressure’ needed to initiate contraction, all the models for the individual actuators produced forces consistent with experimental values, but only the more resource-intensive rod & plate models replicated fiber/braid re-orientation and produced more realistic values for actuator contraction. For panel models, the Full 3D rod & plate model appeared to be the most accurate for panel contraction and force, but was not completed for all configurations due to resource limitations. Most embedded panel FE models produced maximum panel actuator force and maximum contraction when the embedded actuators are spaced between 1/2 and 1 diameter apart. Seven panels with embedded RMAs were experimentally fabricated and tested. Panel tests confirmed that maximum or optimal performance occurs when the RMAs are spaced between 1/2 and 1 diameter apart. The tested actuator force was fairly constant in this range, suggesting that minor design or manufacturing differences may not significantly affect panel performance. However, the amount of axial force and contraction decreases significantly at greater than optimal spacing. This multi-faceted work provides useful design, simulation fabrication, and test characteristics for shape-adaptive panels. Bending panels were demonstrated but not modeled. Developers of future shape-adaptive air vehicles have been provided with additional simulation and design tools.

Multiobjective Optimal Design and Soft Landing Control of an Electromagnetic Valve Actuator for a Camless Engine

This paper presents a multiobjective optimal design and an energy compensation control for the soft valve landing of an electromagnetic valve actuator in internal combustion engines. This axisymmetric and cylindrical actuator is used to achieve continuous and independent valve timing and lifting without mechanical cams, which features a hybrid magnetomotive force with permanent magnet (PM) and electromagnet, and a secondary air gap to prevent the PM irreversibly demagnetizing. The dynamics of the electromagnetic valve are modeled with an equivalent magnetic circuit, which is used to perform both sensitivity analysis and an optimal design function to satisfy multiple objectives, such as magnetic holding force, release current, and its rising time. The energy compensation control in which the positive and negative work of an armature stroke is equalized enables a zero landing velocity to be achieved. The experimental results from a prototype actuator show that the landing velocity can be greatly reduced by adjusting the duty cycle of the landing current, and the actuating power is greatly reduced after the energy compensation control is applied.

Note: Simple and compact piezoelectric mirror actuator with 100 kHz bandwidth, using standard components

We propose a mounting scheme to control the displacement of a mirror (or other small object) by a cylindrical piezoelectric actuator, giving uniform response and no phase lag up to high frequencies. This requires a simple ring holder, and unmodified off-the-shelf components. In our implementation, the piezo-mirror assembly has its first mechanical resonance around 120 kHz, close to the resonance for the bare piezo. The idea is to decouple the fundamental elongation mode of the piezo-mirror assembly from the holder by side-clamping the assembly at its zero-displacement plane for this mode. The main drawback is a reduced mirror displacement, by a factor 2 in our case (mirror displacement is ~2.5 μm). Also, the mirror needs to be light with respect to the piezo: still, we use a standard half-inch mirror. The resulting system is very compact as it fits inside a 1-in. commercial steering mirror post.

Control of a pneumatic drive using electronic pressure valves

The primary task of the electronic pressure (E/P) valves is to control the pressure continuously in different industrial automation processes. Their use in pneumatic drives allows regulating pressures in both cylinder chambers and so it is possible to achieve a direct force controlled actuator. Additionally to the force control, position control of the pneumatic actuator using E/P valves has been presented. A dynamic model for control purposes of the process has been derived, followed by the PID controller tuned according to damping optimum criteria. The control algorithms have been experimentally verified on an industrial cylindrical rod-less actuator controlled by two E/P valves. The control performances are comparable with the set-up with proportional directional control valves (servo-valves). Based on the experimental results, it can be concluded that these valves have potential for successful implementation in industry for position and force control applications.

Fabrication and performance analysis of a DEA cuff designed for dry-suit applications

A method for manufacturing a cylindrical dielectric elastomer actuator (DEA) is presented. The cylindrical DEA can be used in fabricating the cuff area of dry-suits where the garment is very tight and wearing the suit is difficult. When electrically actuated, the DEA expands radially and the suit can be worn more comfortably. In order to study the performance of the DEA, a customized testing setup was designed, and silicone-made cuff samples with different material stiffnesses were tested. Analytical and FEM modeling were considered to evaluate the experimental output. The results revealed that although the stiffness of the DEA material has a direct relationship with the radial constrictive pressure caused by mechanically stretching the DEA, it has a minor effect on the actuation pressure. It was also found that stacking multiple layers of the DEA to fabricate a laminated structure enabled the attainment of a desired variation of pressure required for the implementation of an electrically tunable cuff.

Elastic analysis of exponentially graded piezoelectric cylindrical structures as sensors and actuators

An analytical solution is obtained for functionally graded piezoelectric cylindrical structures, and the electroelastic behavior is investigated. The material properties are assumed to vary as an exponential function along the radial direction of the cylinder. The cylindrical structure acts as sensor or actuator and is subjected to mechanical and electrical loads at its inner and outer cylindrical surfaces. Based on the linear piezoelectricity theory, the governing equation in terms of the radial displacement is obtained as a second-order nonhomogeneous ordinary differential equation with variable coefficients, and its solution is obtained by the Frobenius series method. The illustrative examples show that the material nonhomogeneity has significant effect on the electroelastic fields of functionally graded piezoelectric cylindrical sensors and actuators.

CYLINDRICAL PIEZOELECTRIC MOBILE ACTUATOR BASED ON TRAVELLING WAVE

A design of cylindrical type piezoelectric mobile actuator is proposed and analyzed in the paper. Traveling wave is generated on the top area of the actuator applying harmonic oscillations with different phases. Electrodes of piezoceramic elements are excited by harmonic voltage with phase difference of 2π / 3. Numerical modeling based on finite element method was performed to find resonant frequencies and modal shapes of the actuator and to calculate the trajectories of the upper points movements under excitation scheme. Path-Planning algorithm presented for cylindrical piezoelectric mobile actuator.DOI: http://dx.doi.org/10.5755/j01.mech.18.5.2698

Investigation of Human Masticatory Movements Using ADAMS and MATLAB/SIMULINK

A jaw mechanism based on the biomechanical findings of human mastication system is being developed to simulate jaw motion and investigate its effect on jaw function to provide the basis for jaw model. Following an investigation into the biological process of mastication, a linear cylindrical actuator is used to replace a group of muscles, and it can act bio-directionally with both origin and insertion attached to the skull and the mandible via spherical joints. The trajectory of the incisal point can be reproduced through programming the six actuations. So it builds the functional `relation between incisal point and six actuators. Co-simulations for motion and control have been conducted using the ADMAS and SIMULINK and the results have indicated that the jaw mechanism enables the jaw behaviors to be reproduced perfectly.

A bio-inspired multi degree of freedom actuator based on a novel cylindrical ionic polymer–metal composite material

In this work, we explore a promising electroactive polymer (EAP), called ionic polymer–metal composite (IPMC) as a material to use as a multi degree of freedom actuator. Configuration of our interest is a cylindrical IPMC with 2-DOF electromechanical actuation capability. The desired functionality was achieved by fabricating unique inter-digitated electrodes. First, a 3D finite element (FE) model was introduced as a design tool to validate if the concept of cylindrical actuators would work. The FE model is based upon the physical transport processes—field induced migration and diffusion of ions. Second, based upon the FE modeling we fabricated a prototype exhibiting desired electromechanical output. The prototype of cylindrical IPMC has a diameter of 1 mm and a 20 mm length. We have successfully demonstrated that the 2-DOF bending of the fabricated cylindrical IPMCs is feasible. Furthermore, the experimental results have given new insight into the physics that is behind the actuation phenomenon of IPMC.

Large, uni-directional actuation in dielectric elastomers achieved by fiber stiffening

Cylindrical actuators are made with dielectric elastomer sheets stiffened with fibers in the hoop direction. When a voltage is applied through the thickness of the sheets, large actuation strains are achievable in the axial direction, with or without pre-straining and mechanical loading. For example, actuation strains of 35.8% for a cylinder with a prestrain of 40%, and 28.6% for a cylinder without pre-strain have been achieved without any optimization. Furthermore, the actuation strain is independent of the aspect ratio of the cylinder, so that both large strains and large displacements are readily actuated by using long cylinders.