Cylindrical Actuator Research Articles

Piezoelectric actuators employing PVDF coated with flexible PEDOT-PSS polymer electrodes

Piezoelectric polymer sheets usually have metallic electrodes that considerably stiffen the sheet and correspondingly decrease its piezoelectric response in actuator and sensor applications. We have developed both airbrush and inkjet printing methods for applying electrodes of the conducting polymer poly(ethylene dioxythiophene) (PEDOT-PSS) to sheets of poly(vinylidene fluoride) (PVDF). PEDOT-PSS electrodes of reasonable thickness have considerably higher resistance than metal electrodes. We calculated the voltage and current response as a function of position on the electrodes of a single "electroded" PVDF sheet. We did this both for a rectangular sheet with an ac voltage applied at one end, and for a semicircular sheet with ac voltage applied to a small semicircular metal tab. By finding the response as a function of frequency, we can determine the necessary electrode thickness for various applications. Next we calculated the extension-mode piezoelectric response of a rectangular sheet to an ac voltage applied at one end. We made and tested bimorphs of two such electroded sheets that are glued together to give a bending response. We have also constructed actuators made of two bimorphs attached together at both ends. Better response is achieved than for similar actuators constructed from sheets with metal electrodes. Finally, we compare results for these high-displacement, low-force actuators with those for low-displacement, high-force actuators of direct extension designs, and propose a cylindrical actuator design with intermediate displacement and force

Piezoelectric actuators employing PVDF coated with flexible PEDOT-PSS polymer electrodes

Piezoelectric polymer sheets usually have metallic electrodes that considerably stiffen the sheet and correspondingly decrease its piezoelectric response in actuator and sensor applications. We have developed both airbrush and inkjet printing methods for applying electrodes of the conducting polymer poly(ethylene dioxythiophene) (PEDOT-PSS) to sheets of poly(vinylidene fluoride) (PVDF). PEDOT-PSS electrodes of reasonable thickness have considerably higher resistance than metal electrodes. We calculated the voltage and current response as a function of position on the electrodes of a single PVDF sheet. We did this both for a rectangular sheet with an ac voltage applied at one end, and for a semicircular sheet with ac voltage applied to a small semicircular metal tab. By finding the response as a function of frequency, we can determine the necessary electrode thickness for various applications. Next we calculated the extension-mode piezoelectric response of a rectangular sheet to an ac voltage applied at one end. We made and tested bimorphs of two such electroded sheets that are glued together to give a bending response. We have also constructed actuators made of two bimorphs attached together at both ends. Better response is achieved than for similar actuators constructed from sheets with metal electrodes. Finally, we compare results for these high-displacement, low-force actuators with those for low-displacement, high-force actuators of direct extension designs, and propose a cylindrical actuator design with intermediate displacement and force

Bioenergetics and mechanical actuation analysis with membrane transport experiments for use in biomimetic nastic structures

Nastic structures are synthetic constructs capable of controllable deformation and shape change similar to plant motility, designed to imitate the biological process of nastic movement found in plants. This paper considers the mechanics and bioenergetics of a prototype nastic structure system consisting of an array of cylindrical microhydraulic actuators embedded in a polymeric plate. Non-uniform expansion/contraction of the actuators in the array may yield an overall shape change resulting in structural morphing. Actuator expansion/contraction is achieved through pressure changes produced by active transport across a bilayer membrane. The active transport process relies on ion-channel proteins that pump sucrose and water molecules across a plasma membrane against the pressure gradient. The energy required by this process is supplied by the hydrolysis of adenosine triphosphate. After reviewing the biochemistry and bioenergetics of the active transport process, the paper presents an analysis of the microhydraulic actuator mechanics predicting the resulting displacement and output energy. Experimental demonstration of fluid transport through a protein transporter follows this discussion. The bilayer membrane is formed from 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine lipids to support the AtSUT4 H+-sucrose cotransporter.

Analytic model for a nonlaminated cylindrical magnetic actuator including eddy currents

The eddy currents induced within a nonlaminated cylindrical magnetic actuator by a changing field have a fundamental influence on the actuator's performance. Understanding of these dynamics is essential in designing high-performance actuators and developing control algorithms for them. This paper presents an analytical approach to modeling the relationship between applied magnetomotive force and mechanical force. The approach is based on dividing the actuator into elements according to the flux distribution inside the actuator and finding the frequency-dependent reluctance of the flux paths of each element. An analytic model and its half-order simplification are derived, both of which are explicitly dependent on actuator material and geometric properties. Performance predictions from both analytic models are compared with finite-element analysis, demonstrating the accuracy of the models.

Simple adaptive control for positioning of pneumatic cylinder with adverse stick-slip

Calling it an obsolete technology would be far too emphasized, but pneumatically operated cylindrical linear actuators draw the keen attention of engineeers who are involved in the design of micro/nano positioning, where any electirc or magnetic interferences are to be prohibited to secure a micro-machining in production of the latest µ-chips. This paper aims to describe our preliminary step of challenge to realize a precise pneumatic positioning system, which includes a very conventional pneumatic cylinder having tough stick-stips, a servo-valve with undesirable dead-zone and the Simple Adaptive Control Algorithm that accommodates non-linear functions to minimize the influence of stick-slip without risk of system instability. The stick-slip deteriorates both of transient and steady-state response, therefore the effectiveness of our proposal should have been confirmed by experiment in this paper.

Servo Pneumatic Position Control Using Fuzzy PID Gain Scheduling

In this paper, a design procedure and experimental implementation of a PID controller is presented. The PID controller is tuned according to damping optimum in order to achieve precise position control of a pneumatic servo drive. It is extended by a friction compensation and stabilization algorithm in order to deal with friction effects. In a case of supply pressure variations, more robust control system is needed. It is implemented by extending the proposed PID controller with friction compensator with the gain scheduling algorithm, which is provided by means of fuzzy logic. The effectiveness of proposed control algorithms is experimentally verified on an industrial cylindrical rodless actuator controlled by a proportional valve.

Dielectric elastomer cylindrical actuators: electromechanical modelling and experimental evaluation

This paper presents an experimentally validated electromechanical model of cylindrical actuators made of dielectric elastomers with compliant electrodes. Modelling was based on independent electrical and mechanical analyses of the specific configuration of the device. The expressions of the electrostatic pressures exerted by the electrodes in response to an applied voltage were formulated and inserted into the expressions of the actuator mechanical deformations, obtained by assuming linearly elastic stress–strain constitutive equations of the material for small strains. Values of axial strains expected from the model well fit those recorded from a realised actuator, electrically stimulated by step-wise high voltages. This actuator has carbon grease electrodes smeared on a cylinder-shaped silicone elastomer, showing a room-temperature-relative dielectric constant of 3 within a wide frequency range (10–10 9 Hz). An axial strain of 4.5% due to a voltage per unit wall thickness of 100 V/μm was measured at a 5% axial prestrain, around which the material held a Young's modulus of 5 MPa.

一般産業用空圧シリンダの位置決め制御

Calling it obsolete technology would be far too emphatic, but pneumatically operated cylindrical linear actuators draw the keen attention of engineers who are involved in the design of micro/nano positioning, where any electric or magnetic interferences are to be prohibited to secure a micro-machining in production of the latest μ-chips. This paper aims to describe our preliminary challenge to realize a precise pneumatic positioning system, which includes a very conventional pneumatic cylinder having inherent and tough stick-slips, a servo-valve with undesirable dead-zone and the Simple Adaptive Control Algorithm that accommodates non-linear functions to minimize the influence of stick-slip without risk of system instability. The stick-slip deteriorates both of transient and steady-state response, therefore the effectiveness of our proposal should have been confirmed by experiment in this paper.

Dynamic Behavior of Telescopic Actuators

While piezoelectric actuators are very useful for high frequency applications, their small strokes pose a significant constraint to most applications. Internally leveraged amplification schemes overcome this constraint, but at the cost of output force and bandwidth. The telescopic actuation architecture employs a novel internal amplification scheme that provides a moderate stroke amplification (up to 20 times) while maintaining high force and bandwidth. This paper presents a study of the dynamic behavior of this generic type of actuation. Because of the complexity of the structure, a new modeling technique based upon adaptation of the transfer matrix method was developed. As validation, a three cylindrical PZT5H telescopic actuator was fabricated and experimentally tested.

Temperature and pH‐Dependent Swelling Behavior of Poly(N‐isopropylacrylamide) Copolymer Hydrogels and Their Use in Flow Control

AbstractPoly(N‐isopropylacrylamide) (PNIPAAm) copolymer gels with acidic and basic comonomers of various molar ratios were prepared by radical polymerization. The relationship between the swelling behavior of the gels and the copolymerization ratio was studied experimentally at different temperatures and in various pH value buffer solutions. The results of the experiments revealed that the transition temperatures of the PNIPAAm copolymer gels were changed in proportion to the monomer ratio used in copolymerization. The pH value of the buffer solution strongly affected the swelling ratio and some of the transition temperatures of the gels. The PNIPAAm copolymer gels were used in a chemo‐mechanical valve. The liquid flows directly through a gel actuator, which consists of a cylindrical actuator chamber filled with small particles of the sensitive cross‐linked polymer. The flow rate as well as the pressure drop was measured in dependence on the solvent properties. With the presented experimental arrangement it could be shown that sensitive polymers can be used for controlling the flow in dependence on temperature and pH.pH‐Dependence of the pressure in a chemo‐mechanical valve.magnified imagepH‐Dependence of the pressure in a chemo‐mechanical valve.

Influence of stator slot geometry and rotor eccentricity on field distribution in cylindrical magnetic actuators

The paper presents an analytical method for computing the instantaneous air-gap flux distribution in cylindrical magnetic actuators with slotted stators and rotor eccentricity. The method does not rely on permeance functions; therefore, the resulting flux distribution can be used to compute actuator properties such as negative stiffness, cogging torque, and back-emf. The method uses Fourier series expansions to model current distributions and permanent magnets as sources of magnetomotive force (MMF) on the air-gap boundary and then solves the Dirichlet boundary value problem in the eccentric annulus for the MMF within the permanent magnet and air gap regions. It accounts for the slotting effect by adding a boundary perturbation step to the solution that includes the decreased permeance of the slots. The method is applied to a sample problem that examines both the effects of slot length and slot width on negative stiffness coefficients. The method is benchmarked against finite-element solutions; the two models agree well up to a certain critical slot length. This critical slot length corresponds to the traditional infinite slot length (that slot length beyond which no appreciable change in flux distribution occurs). While the method is applied to a permanent magnet motor of internal rotor construction, it is generally applicable to many actuator topologies.

Considerations on Design for a Cylindrical Moving Magnet Type Linear Oscillatory Actuator having Spring Characteristics

In recent years, linear oscillatory actuators (LOAs) employing mechanical resonance have been researched aiming at highly efficient actuators. This paper considers a cylindrical moving magnet type LOA having spring characteristics for resonant oscillation in the actuator itself An equation to express the thrust of the proposed LOA is derived using a permeance model, and calculation results by the permeance analysis and magnetic field analysis are compared with actual measured results. The thrust constants by the permeance analysis and magnetic field analysis agree with the measurement, and the permeance analysis with a short calculation time is effective in calculation of the thrust constant. The magnetic field analysis is effective in the calculation of the spring characteristics of static thrusts. In addition, the optimization of the size of the proposed LOA based on the motor constant is investigated A relational equation of the size of the LOA and the motor constant is derived. From calculation results on the motor constant using the permeance analysis and magnetic field analysis, the effectiveness of the permeance analysis with a short calculation time is confirmed. Moreover, by focusing on the motor constant below the same thrust constant, it is found that the coil resistance is effective as optimization indices identical to the motor constant.

Piezoelectric Rotary Actuator Driven Devices and Applications

Novel piezoelectric cylindrical ceramic actuators have been developed utilizing the d 15 piezoelectric shear coefficient. These solid state actuators are segmented piezoelectric tubes that generate high torque and angular displacement. This rotary actuation can be applied to the trailing edge flap of a helicopter rotor blade to reduce vibration and to provide real time active blade tuning. For long stroke applications, rotary inchworm/motor devices were designed and fabricated using roller clutches to accumulate the minute displacement of the actuator over many cycles of the applied ac field. Operating at the resonant frequency of the actuator, the amplitude of the rotary angle is amplified by the mechanical quality factor of the device.

身体運動を補助する棒状アクチュエータ:Tail-Armの提案

身体運動を補助する棒状アクチュエータ:Tail-Armの提案

Analysis of Drop-on-Demand Ink Jet Print Head for Rapid Prototyping

ABSTRACTThe rapid prototyping industry is growing dramatically because of its high potential to reduce product design and prototyping cycles. One of the recent technologies in this field is 3D printing using conventional ink jet technology. In order to maximize the capability of this process, it is required to understand the operating mechanism and drop formation process. The current work focuses on the mechanism of a piezoelectric cylindrical actuator and the hydrodynamic characteristics inside a print head in order to achieve more realistic boundary conditions for the numerical simulation of the drop formation process. Linearised Navier-Stokes equations for Newtonian fluid flow are solved analytically for the pump section with a constant radius and for the nozzle section with a tapering angle. Results from the developed solutions are input to Flow 3D and it is observed that analytical pressure histories show better agreement with numerical results than axial velocity histories. The presented analytic model can be used for fully further drop formation simulation as an upstream pressure boundary within an acceptable tolerance.

The influence of magnetization pattern on the performance of a cylindrical moving-magnet linear actuator

This paper is concerned with the influence of the magnetization process on the performance of a cylindrical moving-magnet linear actuator, specifically the extent to which actuator performance, in terms of force-stroke profile, is compromised by the use of homopolar magnetized ring magnets. Finite element modeling of both an ideal radially magnetized ring magnet and a ring magnet on which the magnetization has been imparted by an impulse magnetization fixture is performed, and the results are validated by experimental measurements on a prototype actuator.

Practical Design of a Sliding Mode Controller for Pneumatic Actuators

Pneumatic robot manipulators are characterized by high-order, time-variant actuator dynamics, nonlinearities due to compressibility of air, external disturbances such as static and Coulomb friction, and wide range of payload variations. Conventional PID controllers suffer from problems of gain tuning under these conditions. In this paper, a new control algorithm is proposed for the position and trajectory control of pneumatic actuators based on the sliding mode control approach. The stability of motion is proved for the case of a linear, time-invariant switching surface. A disadvantage of using sliding mode control for third- and higher-order mechanical systems is the need for acceleration feedback. In this paper, to overcome this difficulty we propose the use of differential pressure. The proposed controller is simple, easy to implement, and robust to payload and parametric variations. The effectiveness of the new scheme for position and trajectory control is illustrated by experiments on an industrial piston-driven cylindrical actuator with proportional valves.

Study of a Pneumatic Robot Utilizing a BTA (Bourdon Tube Actuator)

The Pneumatic BTA (Bourdon Tube Actuator) is a sticksliplew actuator which utilize a pair of spiral bourdon tubes as a functional element and obtains displacement by air pres.sure. Compared with an electric motor and so on, the BTA is smaller and lighter; moreover, it generates a high torque and accurate positioning.Before now Alias been difficult for a cylindrical type pneumatic actuator to control accurate positioning because of sliding friction. Our laboratory developed a three-axis driving robot with 4-bar linkage utilizing a pneumatic BTA. We obtained owillating of ± 15 degrees and minimum sensitivity 0.6 × 10-2 degree. A pneumatic BTA robot system makes posble minute action and accurate positioning.

Microstep X-Y-.THETA. Table Using Three-Pole Piezoelectric Tube Actuator.

This paper describes the basic concept of the micro X-Y-θ table system, which is a tool for manipulating microdevices and microorganisms, and the static and dynamic characteristics of the system. This microstep table consists in part of a cylindrical piezoelectric actuator. One electrode of the piezoelectric actuator is inside the cylindrical tube, and three pairs of electrodes are on the outside. The piezoelectric actuator is driven by a pulsatile waveform voltage and moves a specimen on the table along the X and Y axes, and rotates it about the θ axis precisely and exactly. The table is driven by the friction force between the piezoelectric actuator and the table. The stroke and the direction of the table movemen are controlled with a personal computer using a mouse.

搾乳機に用いるリニア振動アクチュエータの１／ｆゆらぎ動作

A conventional milking machine may damage cows'teats, because the suction mechanism is driven by a pneumatic pulsator at a constant frequency. It is known that in natural feeding of calves, a l/f fluctuation signal occurs. This paper describes the performence of a new linear pulsator used instead of a pneumatic pulsator in a milking machine.The linear pulsator is drivenby a cylindrical linear oscillatory actuator (LOA) that is compact and weight light, with external dimensions of φ25 × 35mm, a mass of 114 grams,and a maximum static thrust of 8.2 newtons. It can drive a real load at a frequency of 1 Hz and a voltageof 14 volts, with a stroke of ±2mm. The linear pulsator that contains the LOA is capable of operating with a I/f fluctuation signal, and can realize pressure pulsation a ranging from 41 to 71 beats per minute.