Hydraulic Displacement Amplification Mechanism Research Articles

Development and assessment of large stroke piezo-hydraulic actuator for micro positioning applications

The primary concern with micro-positioning systems is to achieve precise positioning, coupled with the broad stroke of actuation. Over the past few years, the advancement in piezoelectric technology has adequately fulfilled the purpose of precision positioning applications. The advantages of accurate control and positioning accuracy, compactness, minimum wear and tear, enhanced stiffness in conjunction with better dynamic response has led to the extensive utilization of piezoelectric actuators as a precision positioning source. However, the inadequacies of limited positioning stroke, together with the inherent hysteresis hinder the performance of piezoelectric actuators. The present work aims at the development of a new piezo-hydraulic actuator for overcoming the disadvantage of limited stroke of the piezoelectric actuator through hydraulic displacement amplification mechanism (HDAM). The proposed piezo-hydraulic actuator works based on differential area principle and Pascal's law. The prototype of the piezo-hydraulic actuator incorporates amplified piezo actuator (APA) as a primary actuator which deflects a piston causing the fluid to get displaced from larger cross-section to smaller cross-section. This intern leads to amplified motion. An electromechanical model coupled with the Bouc-Wen hysteresis model is implemented in the present work to simulate the displacement and force characteristics of the proposed piezo-hydraulic actuator. The experimental work involved the fabrication and characterization of the proposed piezo-hydraulic actuator. The experimental results are validated by comparing with the simulated results obtained from the mathematical model. The maximum amplification factor of the piezo-hydraulic actuator achieved is about 77.00, which is in close agreement with the theoretical amplification factor of 79, with the error of about 2.53%. When the piezo hydraulic actuator is actuated at 150 V, the amplified piezo actuator achieves a maximum deflection of 129.02 μm which gets amplified to a value of about 9934.69 μm through hydraulic amplification. The fabricated prototype of piezo-hydraulic actuator achieves maximum blocking force of 0.5 N at 150 V.

Surface properties that can be displayed by a microelectromechanical system‐based mechanical tactile display

This study reports the surface properties that a microelectromechanical system (MEMS)-based mechanical tacitle display can present. The display is composed of 3 by 3 large displacement MEMS actuators that comprise hydraulic displacement amplification mechanism and piezoelectric actuators. The control parameters of the display include the displacement, or driving voltage, vibration frequency, and spatial and temporal actuation patterns of the actuators. Roughness and hardness using the newly proposed sample comparison method have been investigated previously. In this study, methods investigating warmness, or thermal conductivity, wettability, or surface energy, and friction were considered. Correlation between the control parameters and the surface properties indicated that the mechanical tactile display is best at controlling the roughness of the surface.

29pm1-E-4 MEMS触覚ディスプレイと触覚センサを用いた擬似的触感の提示

We demonstrate encoding the surface texture using a MEMS-based tactile actuators array. This array is composed of nine piezoelectric actuators and a hydraulic displacement amplification mechanism. It can be applied to a tactile sensor to encode the surface texture into signals. In this work, we prepared micro patterned tactile samples made of Su-8. They have micro stripped patterns on their surface. We only changed the pitch and width of the stripes to control their surface roughness. The experimental result indicate that this tactile sensor enable us to encode the surface texture in the pitch and width range from 200 μm to 900 μm.

20pm3-PM013 触覚センサとの連携による疑似触覚の提示と評価

In this paper, we demonstrate encoding of a surface texture and displaying it to a subject using a MEMS-based tactile display. The tactile display is composed of a piezoelectric actuator array and hydraulic displacement amplification mechanism. We now use the display to encode, or copy, the surface texture by sliding the surface on the display. The obtained waveforms from the piezoelectric actuator array, which worked as the sensor array, was, in turn, amplified to drive the actuator arrays to display the surface texture to the subject whose fingertip was placed onto the display. We successfully copied the surface textures of samples and could even blend the surfaces to create new surfaces with various hardness and roughness. The proposed system is readily applicable to advanced human-computer interactions.

3P2-D07 微細加工触覚サンプルを用いた仮想表面テクスチャの定量化(ハプティックインタフェース)

This paper reports quantification of virtual surface textures produced by the MEMS_based tactile display. Tactile display consists of large displacement MEMS actuator array which is composed of piezoelectric actuators and hydraulic displacement amplification mechanism for large displacement to stimulate human tactile receptors. Tactile display can provide various surface texture to fingertip by controlling the voltages, the vibration frequencies and the time of actuator's driving time. In previous work, we proved that tactile display could create smooth and rough textures by controlling the actuator's parameters. In this study, we newly propose "Sample comparison method". In this method, subjects require to compare between the virtual surface texture and tactile samples and select the sample most similar to displayed tactile feeling. In this paper, we experimented sample comparison experiment using microfabricated tactile samples to quantify the tactile feelings. At last, we successfully show the specific characteristics of surfaces virtually created by the MEMS tactile display.

A peristaltic micropump using traveling waves on a polymer membrane

We demonstrate a peristaltic micropump that utilizes traveling waves on polymer membranes to transport liquids. This micropump requires no valves and, more importantly, the traveling waves can be generated by a single actuator. These features enable the design of simple, compact devices. This micropump has a hydraulic displacement amplification mechanism (HDAM) that encapsulates an incompressible fluid with flexible polymer membranes made of polydimethyl siloxane. A microchannel is attached to the top side of the HDAM. We used a cantilever-type piezoelectric actuator to oscillate the flexible membrane at the bottom of the HDAM, while the top-side membrane drives the liquid in the channel. This format enables rectangular parallelepiped micropumps as compact as 36 mm long, 10 mm wide and several millimeters high, depending on the channel height. Experiments using the fabricated micropumps equipped with microchannels of various heights revealed that the flow rate was dependent on the ratio of the amplitude of the traveling waves to the height of the fluidic channel. The manufactured micropump could successfully generate a maximum flow rate of 1.5 ml min−1 at 180 mW.

Demonstration of Vibrational Braille Code Display Using Large Displacement Micro-Electro-Mechanical Systems Actuators

In this paper, we present a vibrational Braille code display with large-displacement micro-electro-mechanical systems (MEMS) actuator arrays. Tactile receptors are more sensitive to vibrational stimuli than to static ones. Therefore, when each cell of the Braille code vibrates at optimal frequencies, subjects can recognize the codes more efficiently. We fabricated a vibrational Braille code display that used actuators consisting of piezoelectric actuators and a hydraulic displacement amplification mechanism (HDAM) as cells. The HDAM that encapsulated incompressible liquids in microchambers with two flexible polymer membranes could amplify the displacement of the MEMS actuator. We investigated the voltage required for subjects to recognize Braille codes when each cell, i.e., the large-displacement MEMS actuator, vibrated at various frequencies. Lower voltages were required at vibration frequencies higher than 50 Hz than at vibration frequencies lower than 50 Hz, which verified that the proposed vibrational Braille code display is efficient by successfully exploiting the characteristics of human tactile receptors.

Demonstration of Vibrational Braille Code Display Using Large Displacement Micro-Electro-Mechanical Systems Actuators

In this paper, we present a vibrational Braille code display with large-displacement micro-electro-mechanical systems (MEMS) actuator arrays. Tactile receptors are more sensitive to vibrational stimuli than to static ones. Therefore, when each cell of the Braille code vibrates at optimal frequencies, subjects can recognize the codes more efficiently. We fabricated a vibrational Braille code display that used actuators consisting of piezoelectric actuators and a hydraulic displacement amplification mechanism (HDAM) as cells. The HDAM that encapsulated incompressible liquids in microchambers with two flexible polymer membranes could amplify the displacement of the MEMS actuator. We investigated the voltage required for subjects to recognize Braille codes when each cell, i.e., the large-displacement MEMS actuator, vibrated at various frequencies. Lower voltages were required at vibration frequencies higher than 50 Hz than at vibration frequencies lower than 50 Hz, which verified that the proposed vibrational Braille code display is efficient by successfully exploiting the characteristics of human tactile receptors.

A dynamic model for a displacement amplified magnetostrictive driver for activemounts

A magnetostrictive actuator with a hydraulic displacement amplification mechanism isdesigned to be used as a driver in active engine mounts. The dynamic response of theactuator is quantified in terms of the output displacement and the magnetostriction. Eddycurrent losses are modeled as a one-dimensional magnetic diffusion problem in cylindricalcoordinates. The Jiles–Atherton model is used to describe the magnetization state of thematerial as a function of applied magnetic fields. Magnetostriction, which is modeled as asingle-valued function of magnetization, provides an input to the mechanical modeldescribing the system vibrations. Friction at the elastomeric seals is modeled using theLuGre (Lund–Grenoble) friction model for lubricated contacts. Results show that themodel accurately describes the dynamic behavior of the actuator up to 500 Hz. An orderanalysis of the data and calculated responses shows that the model describesthe fundamental and higher-order spectral components generated by the device.

Dynamic Characteristics of a Hydraulic Amplification Mechanism for Large Displacement Actuators Systems

We have developed a hydraulic displacement amplification mechanism (HDAM) and studied its dynamic response when combined with a piezoelectric actuator. The HDAM consists of an incompressible fluid sealed in a microcavity by two largely deformable polydimethylsiloxane (PDMS) membranes. The geometry with input and output surfaces having different cross-sectional areas creates amplification. By combining the HDAM with micro-actuators, we can amplify the input displacement generated by the actuators, which is useful for applications requiring large deformation, such as tactile displays. We achieved a mechanism offering up to 18-fold displacement amplification for static actuation and 12-fold for 55 Hz dynamic actuation.

MNM-5B-6 変位増幅機構を用いた進行波型マイクロポンプ(セッション 5B マイクロエネルギー)

In this research, we propose a progressive wave type micropump with hydraulic displacement amplification mechanism. Micropump contains micro-cavities that have different cross-sectional areas between at the upper and lower parts and encapsulate incompressive glycerin with largely-deformable thin PDMS membranes. The flow channel is bonded on the upper part. The lower side is vibrated with the piezo actuator. The progressive wave amplified on the surface of the flow channel according to the difference of the sectional area is generated. As this progressive wave, the fluid is transported.

MEMS-based hydraulic displacement amplification mechanism with completely encapsulated liquid

We developed a MEMS-based hydraulic displacement amplification mechanism (HDAM) with completely encapsulated liquid that can be used in applications that require large-displacement micro-actuators, such as tactile displays and microvalves controlling large mass flows. The HDAM contains a microcavity that is sealed by easily deformable thin polydimethylsiloxane (PDMS) membranes encapsulating an incompressible fluid and whose input and output surfaces have different cross-sectional areas. A displacement applied to the input surface is amplified at the smaller output surface. We patterned silicon wafers, bonded them to form the microcavity, and encapsulated glycerin within the microcavity by using ultraviolet curable resin as an intermediate layer and bonding easily deformable thin PDMS membranes to the silicon structure in a glycerin solution. This bonding-in-solution approach ensures that the encapsulated glycerin is bubble-free. We obtained fifteen-fold of amplification of the input displacement applied by a piezoelectric actuator and demonstrated a 3 × 3 array of actuators displaying rewritable Braille cells.

T1501-1-2 液体封入による変位増幅機構の開発(マイクロ・ナノ技術のロボティクス応用(1))

T1501-1-2 液体封入による変位増幅機構の開発(マイクロ・ナノ技術のロボティクス応用(1))

Liquid Encapsulation by Bonding-in-Liquid Technique

AbstractWe propose and demonstrate Bonding-in-Solution Technique (BiST) for encapsulation of liquid in MEMS devices. Liquid encapsulation enables innovative MEMS devices with various functions, such as hydraulic displacement amplification and scanning mirrors. Interfusion of air bubbles and leakage of the encapsulated liquid must be averted not to deteriorate device performances. Several liquid encapsulation processes have been proposed, such as parylene deposition and polymer thermal bonding. However, they involve vacuum and/or thermal processes and cannot be applied to volatile liquids. In BiST, two structural layers are passively aligned and brought into contact in solution, where the encapsulation cavities are uniformly filled up with the liquid without air bubbles. A UV-curable resin is used as an adhesive that does not require heat or vacuum environment but UV to bond the two layers. The detail processes of BiST are (a)UV-curable adhesive resin is coated onto the bonding surface of a structural layer. The layer contains not only encapsulating cavities but also concave-shaped structures for the following passive alignment. (b) The other layer with convex-shaped structures is brought into contact in solution, when the two layers are passively aligned by matching concave and convex structures. (c) UV light is irradiated and the two layers are permanently bonded while the contact is maintained by the jig. We successfully achieved encapsulation of DI water and glycerin in PDMS and silicon structural layers. No liquid remains in the bonding interface. Since conventional aligners are not applicable to BiST, we experimentally evaluated the accuracy of the passive alignment process in solution that makes use of matching concave and convex structures. We used a PDMS layer with cylinders (concave) and a silicon layer with cavities (convex) to evaluate the alignment in BiST. The height and depth of the cylinders and cavities are designed such that the PDMS cylinders elastically deform when the two layers are brought into contact. The elastic averaging enables the passive alignment of the two layers. We investigated the bonding accuracy with respect to the number of pairs of concave/convex structures and the height of PDMS cylinders while in contact. The bonding accuracy improved as the number of pairs increased while the height of PDMS cylinders did not show a correlation. The alignment accuracy of 5μm in BiST was achieved with 12 pairs of the concave/convex structures. The ultimate goal of our research is to develop innovative MEMS devices with encapsulated liquid, such as a hydraulic displacement amplification mechanism applicable to a tactile display. Glycerin was encapsulated by largely-deformable-PDMS thin membranes and silicon cavities by using BiST. The displacement at the input was successfully amplified at the output associated with the ratio of the cross-sectional areas.