Homogeneous Electrorheological Fluid Research Articles

Combination of Homogeneous Electro-rheological Fluid and Multi- Electrodes Damper for A Better Control of Car Suspension Motion

Combination of Homogeneous Electro-rheological Fluid and Multi- Electrodes Damper for A Better Control of Car Suspension Motion

FLOW CHARACTERISTICS OF A LIQUID CRYSTAL MIXTURE IN A CIRCULAR PIPE ELECTRODE

A circular pipe electrode was developed to control the pressure and the flow rate of the ER(Electro-rheological) fluids by one of the authors. The shape of the electrode is a circular pipe and some parts of the inner surface of the pipe are the electrode. The diameter of the tube is 1mm and the four pairs of the electrode are used. In the present study a liquid crystal mixture is selected for a homogeneous ER fluid and the pressure drop of the circular pipe electrode is measured for the constant flow rates under application of the voltages. The voltages are added in the peripheral direction. The director which is the average direction of the molecular of the liquid crystal is perpendicular to the flow direction. On the other hands, numerical analysis of the electric fields and the flow in the circular pipe electrode is conducted and the relations between the flow rate and the pressure are obtained for various electric field intensities, which almost agree with experimental results. The emphasized point of the present flow analysis is assuming that the viscosity of a liquid crystal mixture distributes in the flow field. Furthermore the pulse-wave voltages are added to the electrodes to control the pressure drop using the pulse width modulation. It is found that the pressure can be controlled using the pulse width modulation in the some range of the parameters.

Viscous Control of Homogeneous ER Fluid Using a Variable Structure Control

Homogeneous electrorheological (ER) fluid is a smart fluid whose appearance viscous coefficient can be controlled by applying an electric field. Therefore, the application of this fluid can create a damping device in a mechanical system. However, the ER effect of the fluid is easily changed by shear rate or temperature variation. In this study, a viscous coefficient control method using a variable structure control is proposed, and the application of the control method to a clutch using homogeneous ER fluid is demonstrated. Further, in order to discuss the effectiveness of the proposed viscous controller, the ER clutch is used for vibration control of the flexible joint arm. Our results show that the viscous coefficient of the clutch was accurately and speedily controlled by the proposed control method. Thus, it is possible to obtain a reliable ER device that is not influenced by variations in this fluid property.

Influence of Electric Fields on the Flow of a Liquid Crystal Mixture in Circular-Pipe Electrodes

Two types of circular-pipe electrode are designed to control the pressure and flow rate of electrorheological(ER) fluids under the application of an electric field. The shape of the electrode is a circular pipe and some parts of the inner surface of the pipe are made of electrode strips. A liquid crystal mixture is selected as a homogeneous ER fluid and the pressure drop in the circular-pipe electrode is measured at constant flow rates. On the other hand, numerical analysis of the electric field and the fluid flow in the circular-pipe electrode is conducted. It is assumed that the viscosity, which depends on the electric field intensity, is distributed in the flow fields. The relationships between the flow rate and the pressure are simulated numerically for various electric field intensities, which agree with experimental results. The difference in the ER effect between the two types of electrodes is discussed on the basis of the distributions of the electric field intensity and the pressure drop. Furthermore, the influence of both the number of electrode strips and the gaps between electrode strips in the pipe on the flow rate vs. pressure characteristics is investigated numerically, and a comparison of the flow characteristics between the present electrodes and two types of parallel-plate electrodes is conducted.

A Valve-Integrated Microactuator Using Homogeneous ER Fluid

For micromachines using fluid power with high power density, a valve-integrated microactuator using homogeneous ER (electro-rheological) fluid is proposed and developed. For higher performance of the micro ER valve that controls the flow of homogeneous ER fluid using the viscosity change due to the applied electric field, the characteristics of the micro ER valve with different ER fluids are experimentally investigated. Also, a polyimide-diaphragm fluid microactuator is proposed, fabricated, and tested. Then the valve-integrated microactuator is fabricated using above devices and the characteristics are experimentally examined. A micro gripper driven by the microactuator is demonstrated.

Variable viscous control of a homogeneous ER fluid device considering its dynamic characteristics

Homogeneous electro-rheological (ER) fluid is one of the intelligent fluids, having properties by which their apparent viscosity coefficient can be controlled according to the strength of an electric field applied to them. However, the ER effect of the fluid is easily changed by shear rate variation or temperature variation. Therefore, it is desirable for this fluid to be compensated by a feedback controller considering its dynamic characteristic. In this study, a continuous and accurate viscous control method is proposed, in order to enable a more effective use of the ER fluid, and demonstrate the application of the control method to a developed homogeneous ER clutch using a personal computer. The results of our experiment clearly show that the viscous coefficient of the clutch has been accurately and speedily controlled to the desirable viscous coefficient by the proposed control method. Therefore, by applying the proposed control method, it is possible to obtain a reliable ER device without being influenced by variations of this fluid property.

ER Effects of Homogeneous ER Fluid on One-Sided Pattern Electrodes (3rd Report, Proposal of Viscosity Calculation Method)

The ER (electro-rheological) fluid is a substance that can change its apparent viscosity by applying an electric field. We have proposed one-sided pattern electrodes that have some advantages. Then, we have shown the ER effects of a homogeneous ER fluid on the proposed pattern electrodes experimentally. In this paper, we consider a calculation method for the viscosity by using FEM. The relationship between the configurations and viscosity in investigated.

Smart property of homogeneous electrorheological fluid and its application in reducing seismic responses of engineering structures

The smart properties of homogeneous electrorheological fluid (HERF) containing side—chain type liquid crystalline polymer were studied and an actual HERF damper with an adjustable viscosity was produced. A mechanical model of the HERF smart damper was established on the basis of experiment and theoretical analysis. Then a controlled equation of SDOF structure by HERF damper was derived and a semi-active control strategy based on optimal sliding displacement of damper was presented. The simulation results for a single story frame structure indicate that HERF, which may avoid some defects of common particles-suspended ER fluids, is an excellent smart material with better stability. Using the semi-active control strategy presented, HERF smart damper controlled could effectively reduce seismic responses of structures and keeps the control stable at all times.

ER EFFECT OF LIQUID CRYSTAL FLOWING BETWEEN TWO PARALLEL-PLATE ELECTRODES

Liquid crystal is one of homogeneous ER(Electro-rheological) fluids in some range of temperature. Transient responses of pressure drop are examined when liquid crystal flows between two parallel-plate electrodes for constant flow rates. When voltages are applied on the liquid crystal and removed, the pressure responses of the inlet of electrodes are measured with the pressure transducer. At the same time, liquid crystal between the transparent electrodes made of glass is visualized with the high-speed video camera to investigate the time history of the director of the liquid crystal. Outlet of the flow channel with two parallel-plate electrodes is atmosphere. Relation between the flow visualization results and the changes of pressure drop is investigated especially for transient period. In the present experiment the flow rates change from 0.001 cc/sec(velocity is 1 mm/sec) to 0.003 cc/sec and the electric field intensity is from 0.2 kV/mm to 1 kV/mm. The gap of the electrodes is 0.2 mm. The isotropic-nematic transition is 35.5°C and smectic-nematic transition is 23.1°C. The open-loop test facility with the liquid crystal is set in a pyrostat to keep the temperature constant.

Impedance Control of a Single Shaft-Type Clutch Using Homogeneous Electrorheological Fluid

This study demonstrates the application of a precise and variable impedance control to the homogeneous electrorheological (ER) clutch. The viscous coefficient of a homogeneous ER fluid can be changed by the application of an electric field. However, the ER effect of the fluid is easily changed by shear rate variation or temperature variation. Therefore, some feedback compensations are necessary for these systems to maintain a more precise viscosity.In this paper, we apply a force-based impedance control to the homogeneous ER clutch in order to use ER fluid more effectively. First, we study the fundamental characteristics of the homogeneous ER clutch. Next, we apply the viscous control based on the force control in order to maintain a more precise viscosity. The results of our experiment clearly show that the viscosity of the clutch has been accurately and stably controlled by the proposed control method.

Electro-rheological effects of liquid crystalline polymer on one-sided pattern electrodes

In most industrial robots, serious problems of vibratory behavior are caused because of elasticity in the drive systems. An electro-rheological (ER) fluid is a substance that can change its apparent viscosity by the application of an electric field, and homogeneous ER fluids are effective in reducing vibration in robots. Conventional research into ER fluids is based on parallel electrodes with ER fluids between them. Since a high voltage is required for use of ER fluids with parallel electrodes, problems of cost, safety and wiring for practical applications are of concern. In this article, we propose one-sided pattern electrodes that solve some of the above problems. A one-sided pattern electrode is an electrode in a pattern arranged on only one of the two surfaces of a pair of electrodes, with an insulator arranged on the other surface. We developed two kinds of one-sided pattern electrodes: a concentric circle form and a radial form, experimentally verifying the manifestation of ER effects in a liquid crystalline polymer (a homogeneous ER fluid). In addition, the effect of disk gap upon viscosity change was investigated.

Fluidic actuation by electrorheological microdevices

Electrorheological microdevices with planar and cylindrical geometry have been developed for control of fluidic microactuators. The devices consist of capacitor elements of 50 μm gap size, which confine a flow channel of 10–20 mm length. A homogeneous electrorheological fluid (ERF) is used for operation of the devices displaying a viscosity change of about 25 for a voltage of 500 V at a pressure difference of 2000 hPa. The maximum control power is 0.65 mW. Switching times are in the order of 50 ms. The microdevices have been used to control the motion of a micropiston with 1 mm stroke fabricated by the LIGA technology.

A Micro Fluid Control System Using Homogeneous ER Fluid.

To realize practical micromachines using fluid power with high power density, a micro fluid control system using homogeneous ER (Electro-rheological) fluid is proposed and developed. The homogeneous ER fluid whose viscosity is changed by the applied electric field strength is expected to be suitable for compact micromachines as a working fluid. Firstly, a new micro ER valve using homogeneous ER fluid is proposed and fabricated with 9mm in diameter. Static and dynamic characteristics are investigated. With supply pressure of 25 kPa and electric field strength change of 1.0 kV/mm, it is ascertained that the controllable pressure range is 10 kPa and the bandwidth is 0.5 Hz. Secondly, for pumping of homogeneous ER fluid having much higher viscosity than tap water, some improvements such as redesign of check valves and an application of a boost pressure are performed. Output characteristics of a resonantly-driven piezoelectric micropump with the size of φ9×10mm are experimentally investigated and the effectiveness of those improvements is verified. Maximum flow rate of 15 mm3/s and maximum pumping pressure of 0.2 MPa are obtained. Finally, an open-loop micro position control system is fabricated, which consists of the micropump, the micro ER valve and a bellows microactuator. Through basic experiments, it is confirmed that the output displacement of 23 μm and the bandwidth of 0.3 Hz are realized.

A Microvalve Using Homogeneous ER Fluids.

To realize practical high power micromachines using fluid power with high power density, microvalves that can be mounted on such micromachines are required. In this study, a new microvalve using homogeneous ER fluids called the micro ER valve is proposed and fabricated. The homogeneous ER (Electro-rheological) fluids such as nematic liquid crystals whose apparent viscosity its controlled by the applied electric field strength are expected to be suitable for micromachines because they have no particles in them. The proposed micro ER valve features simple, compact and reliable structure without moving parts. Firstly, a 2-port valve with a pair of parallel plate electrodes is fabricated and the static and dynamic characteristics are experimentally invstigated. The viscosity change rate of 2.7 and the rise time of about 150 ms are obtained. Secondly, based on the obtained results, a 3-port micro ER valve with 4.5 mm in diameter and 5.2 mm in height is designed and fabricated and the basic characteristics are experimentally investigated. With electric field strength change of 3.0 kV/mm and supply pressure of 0.34 MPa, the controllable pressure of 0.13 MPa and the bandwidth of 0.6 Hz are realized. Also an application to position control of a bellows microactuator is performed.