[Phenomena]
Electro-rheological(ER) Fluids are materials which undergo significant instantaneous reversible changes in material characteristics when subjected to electrostatic potentials. The most significant change is associated with the bulk viscosity of the material, hence these fluids can be usefully exploited in vibration-suppression situations where these variable damping characteristics may be employed to actively control the response by tailoring the properties of the ER material. The voltages required activating the phase-change in this ER fluid thickness, but since current densities are in the order of only a few milliamps, the total power required is quite low. Furthermore, the response of these ER fluids to the excitation voltage is typically within 1 millisecond and the bandwidths of these fluids are up to 4 KHz, which is, of course, far beyond the requirements of most practical devices
ER fluids typically comprise a fluid suspension with a finely divided porous polymer dispersed in an insulating liquid medium. The suspension typically has a viscosity of the order of 50 cP. When the suspension is subjected to an a.c. or d.c. electric field, the liquid is then able to withstand a non-vanishing yield stress of typically 10 KPa. Thus, when the fluid is stressed below this threshold, the fluid flow occurs but the yield stress remains constant. This rheological behavior can be modeled as a Bingham body, thereby permitting the rheological behavior of these Newtonian fluids to be tailored to suit each engineering application.
<Electric Behavior of ER Fluid>
[Advantages]
An advantage is that an ER device can control considerably more mechanical power than the electrical power used to control the effect, i.e. it can act as a power amplifier. But the main advantage is the speed of response, there are few other effects able to control such large amounts of mechanical or hydraulic power so rapidly.
[Applications]
Since the change in material characteristics of ER fluids is accomplished by utilizing an electrical field, this vibration suppression philosophy is ideally suited to interface with modern solid-state electronics without the inherent limitations of inertia and speed of response associated with traditional actuators. Typical applications of this technology are numerous in engineering, and include the use of ER fluids in the joints of robotic manipulators, vibration control in aerospace and automotive applications. And the normal application of ER fluids is in fast acting hydraulic valves and clutches. Other common applications are in ER brakes and shock absorbers.
• Research Fields
SSSLab (Smart Structure and System Laboratory) have researched for design and control of automotive, robotic and precision machine utilizing ER fluids.
Bingham character and Damping force analysis of ER fluid
Wear and lubrication analysis of ER fluid
rheological character anaysis of ER fluid under high pressure flow mode
Hysteresis modeling of ER fluid considering temperature using Preisach model
Vibration control of flexible structure using ER squeeze film damper
Vibration control of cantilever beam using ER fluid
Vehicle ABS system control usin ER valve
Position control of cylinder system using ER valve
Position control of transfer table using ER brake and clutch
Vibration control of CD-ROM feeding system using ER mount
Vibration control of vehicle engine using ER engine mount
Vibration control of track vehicle using ER suspension unit
Vibration control of vehicle using ER shock absorber
Vehicle motion analyse using ER suspension and ER brake
