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 mech ...

filled with

magnetorheological fluid A magnetorheological fluid (MR fluid, or MRF) is a type of smart fluid in a carrier fluid, usually a type of oil. When subjected to a magnetic field, the fluid greatly increases its apparent viscosity, to the point of becoming a viscoelastic ...

, which is controlled by a

magnetic field A magnetic field (sometimes called B-field) is a physical 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 ...

, 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 (likely copper) wound into a electromagnetic coil, coil. A current through the wire creates a magnetic ...

.Primary Suspension
This allows the damping characteristics of the

shock absorber A shock absorber or damper is a mechanical or hydraulics, hydraulic device designed to absorb and Damping ratio, damp shock (mechanics), shock impulses. It does this by converting the kinetic energy of the shock into another form of energy (typic ...

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

viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

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, spring (device), springs, shock absorbers and Linkage (mechanical), linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems must support b ...

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

prosthetic In medicine, a prosthesis (: prostheses; from ), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through physical trauma, disease, or a condition present at birth (Congenital, congenital disord ...

limbs.

Types

Mono tube Mono may refer to: Biology * Infectious mononucleosis, "the kissing disease" * Monocyte, a type of leukocyte (white blood cell) * Monodactylidae, members of which are referred to as monos Technology and computing * Mono (audio), single-cha ...

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

* 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 se ...

Audi TT The Audi TT is a production front-engine, 2-door, 2+2 sports coupé and roadster, manufactured and marketed by Audi from 1998 to 2023 across three generations. For each of its three generations, the TT has been based on consecutive generations ...

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 ...

Cadillac ATS The Cadillac ATS is a compact executive car (D-segment) manufactured by General Motors and marketed by Cadillac from 2012 to 2019, available in both four-door sedan and two-door coupé body styles. In the US, it is the brand's first locally-buil ...

, CTS-V, DTS, XLR, SRX,

STS STS, or sts, may refer to: Medicine * Secondary traumatic stress, a condition which leads to a diminished ability to empathize * Sequence-tagged site, a gene-reference in genomics * Soft-tissue sarcoma * Staurosporine, an antibiotic * STS (gene ...

Chevrolet Corvette The Chevrolet Corvette is a line of American two-door, two-seater sports cars manufactured and marketed by General Motors under the Chevrolet marque since 1953. Throughout eight generations, indicated sequentially as C1 to C8, the Corvette is not ...

, Camaro ZL1,

Ferrari 458 Italia The Ferrari 458 Italia (Type F142) is an Italian mid-engine sports car produced by Ferrari. The 458 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 Turi ...

, 599GTB, F12 Berlinetta, Mustang Mach-E,

Shelby GT 350 The Shelby Mustang is a high-performance variant of the Ford Mustang built by Shelby American from 1965 to 1967 and by the Ford Motor Company from 1968 to 1970. In 2005, Ford revived the Shelby nameplate for a high-performance model of the f ...

, Holden HSV E-Series,and

Lamborghini Huracán The Lamborghini Huracán (Spanish for "Tropical cyclone, hurricane"; ) is a sports car manufactured by Italian automotive manufacturer Lamborghini replacing the previous Lamborghini V10, V10 offering, the Lamborghini Gallardo, Gallardo. The Hu ...

. These systems were produced by the

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

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, that uses magnetically controlled dampers, or shock absorbers, for a highly adaptive ride. As opposed to tradit ...

MillenWorks MillenWorks, known as Rod Millen Motorsports until 2005, was an American automotive technology company started by Rod Millen in 1980. The company began by preparing Millen's rally cars, and evolved into designing and building them. The company d ...

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 primary land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of the United Stat ...

Stryker The Stryker is a family of Eight-wheel drive, 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 L ...

and

HMMWV The High Mobility Multipurpose Wheeled Vehicle (HMMWV; colloquial: Humvee) is a family of Military light utility vehicle, light, four-wheel drive Military vehicle#Military trucks, military trucks and utility vehicles produced by AM General. It ...

for testing by TARDEC.

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 rotary-wing aircraft, rotorwing aircraft or rotorcraft is a heavier-than-air aircraft with rotary wings that spin around a vertical mast to generate lift. Part 1 (Definitions and Abbreviations) of Subchapter A of Chapter I of Title 14 of the U ...

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 Yield may refer to: Measures of output/function Computer science * Yield (multithreading) is an action that occurs in a computer program during multithreading * See generator (computer programming) Physics/chemistry * Yield (chemistry), the amo ...

of the magnetorheological fluid with

electric current An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge c ...

. 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 Scientific visualization, visual aid for visualizing vector fields. It consists of an imaginary integral curve which is tangent to the field Euclidean vector, vector at each point along its length. A diagram showing ...

Viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

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