A magnetorheological damper or magnetorheological shock absorber is a

damper A damper is a device that deadens, restrains, or depresses. It may refer to: Music * Damper pedal, a device that mutes musical tones, particularly in stringed instruments * A mute for various brass instruments Structure * Damper (flow), a mechan ...

filled with magnetorheological fluid, which is controlled by a

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

, usually using an

electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in ...

.Primary Suspension
This allows the damping characteristics of the

shock absorber A shock absorber or damper is a mechanical or hydraulic device designed to absorb and damp shock impulses. It does this by converting the kinetic energy of the shock into another form of energy (typically heat) which is then dissipated. Most ...

to be continuously controlled by varying the power of the electromagnet. Fluid

viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the int ...

increases within the damper as electromagnet intensity increases. This type of shock absorber has several applications, most notably in semi-active

vehicle suspension Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems must support both road holding/ handling and ride ...

s which may adapt to road conditions, as they are monitored through sensors in the vehicle, and in

prosthetic In medicine, a prosthesis (plural: prostheses; from grc, πρόσθεσις, prósthesis, addition, application, attachment), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trau ...

limbs.

Types

Mono tube Mono may refer to: Common meanings * Infectious mononucleosis, "the kissing disease" * Monaural, monophonic sound reproduction, often shortened to mono * Mono-, a numerical prefix representing anything single Music Performers * Mono (Japanese b ...

Twin tube Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...

* Double-ended MR damper * VIP MR damper

Commercial applications

Many applications have been proposed using magnetorheological (MR) dampers. While vehicle applications are the most common use of MR dampers, useful medical applications have risen as well, including implants and rehabilitation methods. Since MR dampers are not yet perfect, they are limited in terms of application. Disadvantages do exist when using a large scale MR damper, for example, particle settling within the carrier fluid may occur that inhibits some possible application.

History

The technology was originally developed by General Motors Delphi Automotive Division based in the USA and then developed further by BeijingWest Industries in China after BeijingWest Industries bought the technology from General Motors. BeijingWest Industries has subsequently introduced improvements including a redesigned ECU and the introduction of a dual coil system. The first car to use the technology was the 2002.5 Cadillac Seville STS, and the first sports car to use the technology was the 2003 C5 Corvette.

Automotive

These types of systems are available from OEMs for several vehicles, including the

Acura MDX The Acura MDX is a mid-size luxury crossover SUV with three-row seating produced by the Japanese automaker Honda under its luxury Acura division since 2000. The alphanumeric moniker stands for "Multi-Dimensional" luxury. It has ranked as the seco ...

, Audi TT and R8,

Buick Lucerne The Buick Lucerne is a full-size car manufactured by General Motors from 2005 to 2011. Named for the city of Lucerne, Switzerland, it served as Buick's top-of-the-line sedan until it was replaced by the second generation Buick LaCrosse. History T ...

, Cadillac ATS, CTS-V, DTS, XLR, SRX, STS,

Chevrolet Corvette The Chevrolet Corvette is a two-door, two-passenger luxury sports car manufactured and marketed by Chevrolet since 1953. With eight design generations, noted sequentially from C1 to C8, the Corvette is noted for its performance and distinctiv ...

, Camaro ZL1,

Ferrari 458 Italia The Ferrari 458 Italia (Type F142) is a mid-engine sports car produced by Ferrari. The F458 is the successor of the F430, and was first officially unveiled at the 2009 Frankfurt Motor Show. It was succeeded by the 488 GTB (Gran Turismo Berl ...

, 599GTB, F12 Berlinetta, Mustang Mach-E, Shelby GT 350, Holden HSV E-Series, and

Lamborghini Huracán The Lamborghini Huracán (Spanish for "hurricane"; ) is a sports car manufactured by Italian automotive manufacturer Lamborghini replacing the previous V10 offering, the Gallardo. The Huracán was revealed online in December 2013, making its w ...

. These systems were produced by the

Delphi Corporation Aptiv PLC is an Irish-American automotive technology supplier with headquarters in Dublin. Aptiv grew out of the now-defunct American company, Delphi Automotive Systems, which itself was formerly a component of General Motors. History The co ...

and now by BWI Group under the proprietary name

MagneRide MagneRide is an automotive adaptive suspension with magnetorheological damper system developed by the Delphi Automotive corporation, during a period when the company was a subsidiary of General Motors (GM), that uses magnetically controlled damp ...

. MillenWorks has also included them in several military vehicles including the

MillenWorks Light Utility Vehicle The MillenWorks Light Utility Vehicle (LUV) is a prototype testbed for automotive technologies. It was designed and built by MillenWorks under contract to the Tank Automotive Research, Development and Engineering Center. Textron Marine and Land ...

, and in retrofits to the

US Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...

Stryker The Stryker is a family of eight-wheeled armored fighting vehicles derived from the Canadian LAV III. Stryker vehicles are produced by General Dynamics Land Systems-Canada (GDLS-C) for the United States Army in a plant in London, Ontario. I ...

and

HMMWV The High Mobility Multipurpose Wheeled Vehicle (HMMWV; colloquial: Humvee) is a family of light, four-wheel drive, military trucks and utility vehicles produced by AM General. It has largely supplanted the roles previously performed by the ori ...

for testing by

TARDEC The United States Army DEVCOM Ground Vehicle Systems Center (GVSC) (formerly United States Army Tank Automotive Research, Development and Engineering Center (TARDEC)), located in Warren, Michigan, is the United States Armed Forces' research and ...

Aviation

MRF-based dampers are excellent candidates for stability augmentation of the lead-lag (in-plane bending) mode of rotor blades in helicopters. MRF-based squeeze film dampers are being designed for use in the

rotary wing A rotorcraft or rotary-wing aircraft is a heavier-than-air aircraft with rotary wings or rotor blades, which generate lift by rotating around a vertical mast. Several rotor blades mounted on a single mast are referred to as a rotor. The Inte ...

industry to isolate vibrations from the aircraft structure and crew.

Control

A magnetorheological damper is controlled by algorithms specifically designed for the purpose. There are plenty of alternatives, such as skyhook or groundhook algorithms.Magnetorheological Damper Laboratory
The idea of the algorithms is to control the yield point shear stress of the magnetorheological fluid with

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...

. When the fluid is in the presence of an applied

, the suspended metal particles align according to the

field line A field line is a graphical visual aid for visualizing vector fields. It consists of an imaginary directed line which is tangent to the field vector at each point along its length. A diagram showing a representative set of neighboring field ...

Viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the int ...

of the fluid increases according to the intensity of the magnetic field. When this occurs at the right instant, the properties of the damper change helps in attenuating an undesired shock or vibration. The relative efficacy of magnetorheological dampers to active and passive control strategies is usually comparable.

References

{{Reflist Shock absorbers Automotive suspension technologies Biological engineering Prosthetics