Cylindrical Actuator Research Articles

Single Cylinder-Type Piezoelectric Actuator with Two Active Kinematic Pairs

There is an ever-increasing demand for small-size, low-cost, and high-precision positioning systems. Therefore, investigation in this field is performed to search for various solutions that can meet technical requirements of precise multi-degree-of-freedom (DOF) positioning systems. This paper presents a new design of a piezoelectric cylindrical actuator with two active kinematic pairs. This means that a single actuator is used to create vibrations that are transformed into the rotation of the sphere located on the top of the cylinder and at the same time ensure movement of the piezoelectric cylinder on the plane. Numerical and experimental investigations of the piezoelectric cylinder have been performed. A mathematical model of contacting force control was developed to solve the problem of positioning of the rotor when it needs to be rotated or moved according to a specific motion trajectory. The numerical simulation included harmonic response analysis of the actuator to analyze the trajectories of the contact points motion. A prototype actuator has been manufactured and tested. Obtained results confirmed that such a device is suitable for both positioning and movement of the actuator in the plane.

Design and Fabrication of an Optimized Cylindrical Electromagnetic Pulsed Actuator

In this paper, we present a strategy for designing a high-power linear electromagnetic pulsed actuator considering thermal, electromagnetic, and mechanical aspects. The optimization process was based on a first-principle calculation of the maximum current that the different parts of the coil and the materials conforming the device can resist without taking damage or altering their properties significantly due to thermal or mechanical stresses. Specifically, the minimum coil resistance (and the maximum safe current) for a given applied voltage was computed for a variety of wire diameters. Then, we employed a tailored numerical code to compute the coil geometry that produces the maximum pull/push force per ampere for typical commercial permanent magnet sizes. The combination of the optimized coil resistance and the optimized normalized force gives a maximized total force developed in the solenoid actuator. The designed coil was fabricated and characterized in order to analyze its performance. The results were compared with the calculations to perform an experimental validation of the numerical code obtaining and excellent agreement between computed and experimental results.

Releasing systems for aerospace industry based upon Shape Memory Alloys: characterization of materials for actuators

Releasing and deployment maneuvers carried out during space satellites launching are usually performed by utilizing pyrotechnics loads. However, it is considered convenient to replace this technique by others not requiring explosives (Non Explosive Actuators-NEA). This is mainly due to the necessity of reducing highshock and vibrations induced levels, also avoiding the contamination of sensible instruments because of dust and gas release during explosion. In addition, the avoidance of risks associated with storage and manipulation of explosives and the possibility of performing device retesting prior to final mounting are desirable qualities. Among NEA devices, those exploiting the singular mechanical behavior of Shape Memory Alloys (SMA) have reached commercial maturity. In this study, the performance of a NEA device that uses the mechanical stress generated upon reverse transformation of a mechanically constrained SMA actuator (constrained recovery effect) to generate the controlled fracture of a notched bolt is analyzed. Firstly, the mechanical components of the system are described, and the main problems associated with its design are introduced. Then, the results of the experimental characterization performed on a NiTi SMA cylindrical tube actuator with 12.7 and 7.8 mm outer and inner diameter respectively, are presented. After an activation stage in which the cylinder is compressed to induce the martensitic phase (or re-orient the existing martensitic phase), the temperature is raised while a constant displacement condition is imposed. For temperatures near 120 oC, a loads increment of 35 kN (440 MPa) is obtained. The repetition of this loading-unloading-heating-cooling cycle does not generate any important deterioration in the material response. Keywords: Constrained Recovery, SMA actuators, NiTi, Release systems.

Structure design and characteristics analysis of a cylindrical giant magnetostrictive actuator for ball screw preload

In order to achieve automatic adjustment of the double-nut ball screw preload, a magnetostrictive ball screw preload system is proposed. A new cylindrical giant magnetostrictive actuator (CGMA), which is the core component of the preload system, is developed using giant magnetostrictive material (GMM) with a hole. The pretightening force of the CGMA is determined by testing. And the magnetic circuit analysis method is introduced to calculate magnetic field intensity of the actuator with a ball screw shaft. To suppress the thermal effects on the magnetostrictive outputs, an oil cooling method which can directly cool the heat source is adopted. A CGMA test platform is established and the static and dynamic output characteristics are respectively studied. The experimental results indicate that the CGMA has good linearity and no double-frequency effect under the bias magnetic field and the output accuracy of the CGMA is significantly improved with cooling measures. Although the output decreased with screw shaft through the actuator, the performance of CGMA meets the design requirements for ball screw preload with output displacement more than 26 μm and force up to 6200 N. The development of a CGMA will provide a new approach for automatic adjustment of double-nut ball screw preload.

Modeling and Design of “Smart Braid” Inductance Sensors for Fiber-Reinforced Elastomeric Enclosures

Fiber-reinforced soft actuators use inextensible fibers to shape the expansion of elastomeric fluid-filled chambers. The classic example, McKibben muscles, is part of a broader class of cylindrical soft actuators known as fiber-reinforced elastomeric enclosures (FREEs). These actuators can be designed to twist while extending or contracting. Using a circuit of conductive, electrically insulated wire as the reinforcing fibers allows one to measure the motion of the actuator with the circuit inductance. These sensors, developed previously for McKibben muscles, are known as “Smart Braids.” This paper extends the concept of Smart Braids to the broader class of two-fiber-family cylindrical FREEs. A dimensionless model for the inductance of Smart Braid FREEs is presented that can be scaled to specific sensor geometries. This model depends only on the ratio of the fiber lengths in the two families and the angle of one of the fibers. The model was validated both numerically and experimentally, predicting the sensitivity of experimental sensors accurately, the largest errors being −11% and 9%. The model presented in this paper will enable high-level design decisions for Smart Braid FREES and optimization without computationally expensive direct numerical simulation.

The Electromechanical Behavior of Dielectric Elastomer Actuator Stiffened by Fiber

Dielectric elastomer is functional material that can convert electrical energy to mechanical energy. In this paper, a cylindrical dielectric elastomer actuator was designed and fabricated by using fiber stiffening to improve its electromechanical performance. the effects of pre-straining, rate of applied voltage and fiber stiffening on the electromechanical behavior were investigated by the experiments. It was found that the best applied load for pre-straining was 524g based on the electromechanical tests at the applied voltage rate of 10V/s. The maximum actuated strain decreased with an increase in rate of applied voltage. When the fibers were embedded in the dielectric elastomer actuator, the maximum actuated strain was 27.5%, doubled the value of 14% without fiber stiffening at the applied voltage rate of 20V/s.

Miniature Soft Electromagnetic Actuators for Robotic Applications

AbstractElectromagnetic actuators (EMAs) serve the majority of motion control needs in fields ranging from industrial robotics to automotive systems and biomedical devices, due to their unmatched combination of speed, precision, force, and scalability. This paper describes the design and fabrication of miniature soft EMAs that operate based on the Lorentz force principle. The actuators are fabricated from silicone polymer, liquid metal (LM) alloy (eutectic gallium indium, EGaIn), and magnetic (NdFeB) powder. They are small, intrinsically deformable, and can be fabricated using simple techniques. The central elements of the actuators are fine, 3D helical coil conductors, which are used as electromagnetic inductors. The coils are formed from stretchable filaments that are filled with a LM alloy. To achieve high power densities, the filaments themselves may be fabricated from colloids of EGaIn microdroplets in a silicone polymer matrix, allowing them to dissipate heat and accommodate high currents, and thus high forces. Millimeter‐scale cylindrical actuators are demonstrated for linear high frequency motion and articulated devices for bending motion. These actuators are applied in a vibrotactile feedback display and in a miniature soft robotic gripper.

The dynamics of a parallel Schönflies-motion generator

A parallel architecture was recently proposed to generate Schönflies motions. The CRRHHRRC closed kinematic chain offers a symmetric single-loop architecture, isostatic design, and high rotatability11The industry-adopted test cycle calls for a rotatability of at least a half-turn. Any SMG capable of rotating its moving platform by more than a half-turn is termed here of high rotatability. of its gripper. This pick-and-place robot uses an innovative cylindrical drive, which is a realization of a two-degree-of-freedom cylindrical actuator. The authors report the kinematics and dynamics analysis of the above-mentioned Schönflies-motion generator, developed at McGill University’s Centre for Intelligent Machines. This analysis is intended to optimize the robot design. Validation of the mathematical model was conducted experimentally. The results reveal the accuracy of the model.

Omni Directional Multimaterial Soft Cylindrical Actuator and Its Application as a Steerable Catheter.

Soft actuators with complex range of motion lead to strong interest in applying devices like biomedical catheters and steerable soft pipe inspectors. To facilitate the use of soft actuators in devices where controlled, complex, precise, and fast motion is required, a structurally controlled Omni directional soft cylindrical actuator is fabricated in a modular way using multilayer composite of polylactic acid based conductive Graphene, shape memory polymer, shape memory alloy, and polyurethane. Multiple fabrication techniques are discussed step by step that mainly include fused deposition modeling based 3D printing, dip coating, and UV curing. A mathematical control model is used to generate patterned electrical signals for the Omni directional deformations. Characterizations like structural control, bending, recovery, path, and thermal effect are carried out with and without load (10 g) to verify the new cylindrical design concept. Finally, the application of Omni directional actuator as a steerable catheter is explored by fabricating a scaled version of carotid artery through 3D printing using a semitransparent material.

Detwinning of preloaded martensite in shape memory alloys and its effect on the cyclic behavior of NiTi cylindrical actuators

A multi-mechanism material model is used to investigate the effect of the degree of martensitic detwinning/reorientation occurring at the end of mechanical preloading, on the performance of shape memory tubular and solid cylindrical actuators. A high-temperature ternary Ni50.3Ti29.7Hf20 alloy, showing almost complete transformation behavior, and an ordinary binary Ni49.9Ti50.1 material, depicting incomplete martensitic transformation, are used. The results indicated a clear correlation between the shape memory cyclic actuation behavior and the martensitic deformation character of the selected alloy. More specifically, while the actuation strokes produced by the Ni50.3Ti29.7Hf20 systems consistently followed a direct pattern for the different geometries and torque magnitudes, the results for the Ni49.9Ti50.1 cases indicated a behavior that is counterintuitive to what may be expected under pure mechanical loading conditions. In particular, when subjected to the same, high preload torques, Ni49.9Ti50.1 solid actuator under lesser stresses generated higher twist strokes than a tubular counterpart experiencing higher stresses.

Application of the Thermal Fin Approximation to Modeling Voice Coil Magnetic Fields and Performance

This paper develops an approximate analytical model to describe the magnetic fluxes, forces, and armature reaction in cylindrical voice coil actuators and related electric machines. Magnetic flux is assumed to either lie in an inner region of the actuator and parallel to its axis, or in an outer region of the actuator and oriented radially. A differential reluctance model is derived for this set of assumptions, with a structure and solution set similar to those involved in extended-surface heat transfer (“fins”) and lossy transmission lines. Particular solutions for the force constant, motor constant, coil inductance, and variable-reluctance force are found for a symmetric motor with opposed axial permanent magnets on either side of an iron flux concentrator. The model results for this topology are validated using finite-element analysis and experimental measurements from a prototype.

A Three‐Position Swing Electromagnetic Actuator with an Integrated Eddy Current Brake for Suppression of the Operating Time and Improvement of the Stopping Accuracy

SUMMARYA closed‐loop control system is commonly used in electromagnetic actuators to ensure operating performance. However, this system frequently leads to high costs. We developed a swing electromagnetic actuator with an integrated eddy current brake to reduce the operating time and improve the stopping accuracy. The developed actuator is a three‐position cylindrical actuator moving within a ±120º angle without closed‐loop control. The rotor is composed of a bulk and thin metal laminations and the stator has three sets of pairs of coils. The rotor is stopped at an intermediate position by magnetic force generated by the coils. This paper describes the electromagnetic design and its evaluation by using an FEM simulation to predict its operating characteristics and measure its performance on a test bench. The superiority of our actuator design is verified by comparing these measurements. The operating time is reduced to one‐sixth of that of a laminated rotor and the over travel is compressed to zero. In addition, this actuator has the advantage that it is electrically robust against variations in the power supply.

On the cyclic stability of the thermomechanical behavior of NiTi shape memory cylindrical actuators

The cyclic performance of cylindrical SMA actuators are investigated, taken into account the individual effects of the (1) selected SMA material, (2) geometric configuration of the actuator, and (3) prior mechanical load path taking to a targeted stressed preload state before starting thermal cycles. The “ordinary”, commercially-available, binary Ni49.9Ti50.1 and a developmental “high temperature” ternary Ni50.3Ti29.7Hf20 alloys are used for comparison. The responses of these alloys are characterized using a multimechanism SMA model. Cylindrical actuator geometries, ranging from thin tubular configuration, where there is more uniformity in stress distribution, to a solid section, having significant non-homogeneities in stress, are utilized. Both proportional and non-proportional loading conditions are examined under limited stress levels and thermal cycles. Based on the results obtained for the alternative actuator designs, the conclusions are: (i) high actuation strokes are produced by Ni49.9Ti50.1 actuators, (ii) the Ni50.3Ti29.7Hf20 actuators show relatively more dimensionally stable actuation performance, (iii) there is a marked difference in the degree of mechanical load-path dependency on cyclic behavior between the Ni49.9Ti50.1 and Ni50.3Ti29.7Hf20 actuators, (iv) the cyclic response of the Ni50.3Ti29.7Hf20 is far less sensitive to the actuator geometry in comparison to the Ni49.9Ti50.1, and (v) differences in actuator performance are connected to the intrinsic transformation behavior of the selected shape memory alloys.

Dynamic Performance of Segmented Active Magnetic Thrust Bearings

In this paper, analytic models are developed for segmented cylindrical electromagnetic actuators having a center hole. Analytic models developed are verified via extensive comparison to results obtained by finite-element analysis. Both analytical and finite-element results demonstrate that the segmentation of the stator results in dramatic improvements in actuator dynamic performance by reducing the effect of eddy currents. A doubling of actuator bandwidth can be expected when six stator cuts are introduced.

Stacked dielectric tubes with electromechanically controlled radii

This work examines the features and capabilities of a tube comprised of stacked cylindrical dielectric layers separated by flexible electrodes with the applicative aim of electrically controlling the inner radius. The study begins with the analysis of the non-homogenous electromechanical response of a single-layer dielectric tube according to well-established coupled models. Two boundary conditions are examined - traction free boundaries and a fixed outer radius. The advantages and limitations of each boundary conditions are discussed. It is shown that dielectric tubes subjected to traction free boundaries experience instabilities, an effect that can be avoided by fixing the outer surface. Next, the electromechanical behavior of a stacked cylindrical actuator comprised of dielectric tubes that are mechanically connected in series and electrically connected in parallel is determined under the two boundary conditions discussed above. It is shown that the stacking of cylindrical layers increases the range of available inner radii at the cost of design limitations. Interestingly, it is found that mounting layers on a stacked cylindrical actuator may lead to instabilities even if the outer radius is fixed.

Design Methodology of a Dual-Halbach Array Linear Actuator with Thermal-Electromagnetic Coupling.

This paper proposes a design methodology for linear actuators, considering thermal and electromagnetic coupling with geometrical and temperature constraints, that maximizes force density and minimizes force ripple. The method allows defining an actuator for given specifications in a step-by-step way so that requirements are met and the temperature within the device is maintained under or equal to its maximum allowed for continuous operation. According to the proposed method, the electromagnetic and thermal models are built with quasi-static parametric finite element models. The methodology was successfully applied to the design of a linear cylindrical actuator with a dual quasi-Halbach array of permanent magnets and a moving-coil. The actuator can produce an axial force of 120 N and a stroke of 80 mm. The paper also presents a comparative analysis between results obtained considering only an electromagnetic model and the thermal-electromagnetic coupled model. This comparison shows that the final designs for both cases differ significantly, especially regarding its active volume and its electrical and magnetic loading. Although in this paper the methodology was employed to design a specific actuator, its structure can be used to design a wide range of linear devices if the parametric models are adjusted for each particular actuator.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ КОМБИНИРОВАННОЙ СИСТЕМЫ ВИБРОЗАЩИТЫ ПРЕЦИЗИОННОГО ОБОРУДОВАНИЯ

Test results of the combined vibration protection system for suppressing oscillation precision equipment are considered. In-depth analysis was carried out theoretical research in the field of vibration protection systems. These studies are not sufficient to develop in this field of science. In the fact that in general as power elements are considered electromagnetic devices. However, in most cases, electromagnetic fields adversely affect the operation of precision equipment mounted on vibration protection table. This bring about us to seek the possibility of using an actuators using alternative forms of energy. One such case is the energy of the compressed gas. Among the actuators, is widely used in pneumatic systems occupy a special place rubber-cord casing. They have a high load capacity, low stiffness and significantly cheaper than pneumatic cylindrical actuators. However, it has a serious drawback, which is that only provide one-way force direction. Reversal of these devices is carried out by the weight of equipment which installed on them, or by spring element. It is decided in the actuator design of the system to use the reverse gear, like those used in the direct stress machine. Rubber-cord casing mounted on the reverser eliminates the elastic elements of the reverse and make the process controllable. Thus, one shell acts as a passive vibration protection, and the other two in the active system. Working at the same time they combine into vibration protection system. The study developed a mathematical model of combined vibration protection system with throttle control gas pressure in the actuators showed its effectiveness in the low frequency range. For laboratory tests designed and built an experimental complex that includes the oscillation excitation system, the implementation of a combined power system, control system and measuring and computing complex. Tests were conducted on the experimental stand with a speed based automatic control system for protected object. The results show the effectiveness of combined vibration protection system in comparison with the tests of only a passive system. The evaluation of quality combined with vibration protection system uses integral criteria showed its effectiveness compared to a passive vibration protection system with harmonic excitation by up to 40%. Received test results are the difference in the low-frequency range of the working area with a Range of mathematical modeling of data at the level of 10%.

Accurate Dynamic Modeling of Helical Ionic Polymer-Metal Composite Actuator Based on Intrinsic Equations

This paper presents dynamic modeling of an innovative contractible ionic polymer-metal composites (IPMC) actuator with a helical configuration. The helical shaped IPMC actuator is fabricated through the thermal treatment of an IPMC strip, which is helically coiled on a glass rod. This type of a soft actuator can be used to realize not only bending motion but also torsional and longitudinal motion. For the first time, an explicit analytical expression is developed for the computation of mode shapes and dynamic responses of a helical IPMC actuator based on the intrinsic equations of the naturally curved and twisted beam. The numerical transfer-matrix method is used to solve the systems of 12 linear ordinary differential equations with boundary conditions. In particular, the effect of the structural parameters on the performance of the helical IPMC actuator is evaluated, using experimental results and an analytical model. The validation of the proposed model is achieved through comparison with computational results using a commercial finite-element (FE) program as well as experimental results. The present experimental and theoretical results show that diameter, among the structural parameters, plays an important role in the actuation performance of a helical IPMC actuator. The proposed modeling is general and can also be used in solving other cylindrical or noncylindrical helical IPMC actuators with different cross-sectional shapes as well as various end conditions.

1P1-T01 空気圧ソフトアクチュエータを用いた伸長型3自由度湾曲モデルの研究 : 繊維強化型円筒ラバーアクチュエータの理論式の構築と静特性の評価

Pneumatic actuators have a low stiffness and low cost, which enables disposability of system components. They are highly useful for medical use in terms of infection prevention and easiness to compatible with biological systems. We designed a pneumatic soft actuator, called "fiber-reinforced cylindrical rubber actuator (henceforth FCRA)", and manufactured an extension type 3-degrees-of-freedom bending model by combining the three FCRAs. We derived the theoretical formula used to describe and evaluate static properties of our model, and then validated it through various actuation experiments for extension and bending movements. As a result, our theory has successfully explained all the experimental results. We are currently planning to apply the proposed model to the tip part of colonoscopes.

A cylindrical ionic polymer-metal composite-based robotic catheter platform: modeling, design and control

Ionic polymer metal composites (IPMCs) are soft electroactive polymers that have recently gained considerable attention in biomedical engineering as actuators and sensors. This study focuses on modeling, design and control of a cylindrical IPMC actuator with sectored electrodes. The cylindrical IPMC allows for multi-degree of freedom motion and accurate control of the tip location that can be utilized in biomedical active catheter devices. A three-dimensional finite element model is constructed to describe the physics of cylindrical IPMC actuation. The model is implemented to conduct optimization studies that provide conceptual designs that can maximize deflection, force output, and twisting actuation. Also, a cylindrical tube-shaped IPMC is designed and fabricated. This type of IPMC offers the ability to embed a specific tool and accurately control the tool tip location, which is critical in catheter procedures. To effectively utilize the tube-type IPMC, a closed-loop control system is created based on the electromechanical model and tested in different actuation settings. To improve functionality and the user interface the control system is designed to work on a laptop touchpad.