Electro magnetic suspension system

Electro magnetic suspension system

1.INTRODUCTION

Today’s vehicle suspensions use hydraulic dampers (shock absorbers) and springs that

are charged with the tasks of absorbing bumps, minimizing the car's body motions while

accelerating, braking and turning and keeping the tires in contact with the road surface.

Typically, these goals are somewhat at odds with each other. Luxury cars are great at

swallowing bumps and providing a plush ride, but handling usually suffers as the car is prone

to pitch and dive under acceleration and braking, as well as body lean under cornering .On

the other end of the spectrum, stiffly sprung sports cars exhibit minimal body motion as the

car is driven aggressively, as cornering is flat, but the ride quality generally suffers.

In an ongoing research project that has spanned over 24 years Bose has created a

unique electromagnetic suspension system for automobiles that is close to commercial release

and is set to replace traditional shocks and springs with electronic actuators. "This is the first

time a suspension system is the same for a sports car and for a luxury car", said its creator, Dr

Amar Bose, chairman and head of technical design. The result is a ride that is level and bump

free over incredibly rough terrain and when the vehicle turns in to corners.

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2.BACKGROUND

Every automotive suspension has two goals: passenger comfort and vehicle control.

Comfort is provided by isolating the vehicle’s passengers from road disturbances. Control is

achieved by keeping the car body from rolling and pitching excessively, and maintaining

good contact between the tire and the road. Unfortunately, these goals are in conflict. In a

luxury sedan the suspension is usually designed with an emphasis on comfort, but the result is

a vehicle that rolls and pitches while driving and during turning and braking. In sports cars,

where the emphasis is on control, the suspension is designed to reduce roll and pitch, but

comfort is sacrificed.

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3.SIGNIFICANT ADVANCEMENT

The Bose suspension required significant advancements in four key disciplines:

linear electromagnetic motors, power amplifiers, control algorithms, and research vehicles.

Bose took on the challenge of the first three disciplines, and bet on developments that

industry would make on the fourth item. Prototypes of the Bose suspension have been

installed in standard production vehicles. These research vehicles have been tested on a wide

variety of roads, on tracks, and on durability courses.

Linear Electromagnetic Motor: A linear electromagnetic motor is installed at each wheel of a

Bose equipped vehicle. Inside the linear electromagnetic motor are magnets and coils of wire.

Fig3.1 parts of suspension system

When electrical power is applied to the coils, the motor retracts and extends, creating motion

between the wheel and car body. One of the key advantages of an electromagnetic approach

is speed. The linear electromagnetic motor responds quickly enough to counter the effects of

bumps and potholes, maintaining a comfortable ride. Additionally, the motor has been

designed for maximum strength in a small package, allowing it to put out enough force to

prevent the car from rolling and pitching during aggressive driving maneuvers.

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Power Amplifier: The power amplifier delivers electrical power to the motor in response to

signals from the control algorithms. The amplifiers are based on switching amplification

technologies pioneered by Dr. Bose at MIT in the early 1960s – technologies that led to the

founding of Bose Corporation in 1964. The regenerative power amplifiers allow power to

flow into the linear electromagnetic motor and also allow power to be returned from the

motor. For example, when the Bose suspension encounters a pothole, power is used to extend

the motor and isolate the vehicle’s occupants from the disturbance. On the far side of the

pothole, the motor operates as a generator and returns power back through the amplifier. In so

doing, the Bose suspension requires less than a third of the power of a typical vehicle’s air

conditioning system.

Control Algorithms: The Bose suspension system is controlled by a set of mathematical

algorithms developed over the 24 years of research. These control algorithms operate by

observing sensor measurements taken from around the car and sending commands to the

power amplifiers installed in each corner of the vehicle. The goal of the control algorithms is

to allow the car to glide smoothly over roads and to eliminate roll and pitch during driving.

Research Vehicle: In many of today’s production vehicles, the suspension system is

comprised of front and rear suspension modules that bolt to the underside of the vehicle. The

Bose suspension takes advantage of this configuration by creating replacement front and rear

suspension modules. Using this approach, the research team has been able to retrofit the Bose

suspension into existing production vehicles with minimal modifications. Bose’s front

suspension modules use a modified McPherson strut layout and the rear suspension modules

use a double-wishbone linkage to attach a linear electromagnetic motor between the vehicle

body and each wheel. Torsion springs are used to support the weight of the vehicle. In

addition, the Bose suspension includes a wheel damper at each wheel to keep the tire from

bouncing as it rolls down the road. Unlike conventional dampers, which transmit vibrations

to the vehicle occupants and sacrifice comfort, the wheel damper in the Bose suspension

system operates without pushing against the car body, maintaining passenger comfort.

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Challenges: Every automotive suspension has two goals: passenger comfort and vehicle

control. Isolating the vehicle’s passengers from road disturbances like bumps or potholes

provides comfort. Control is achieved by keeping the car body from rolling and pitching

excessively, and maintaining good contact between the tire and the road.

Unfortunately, these goals are in conflict. In a luxury sedan the suspension is usually

designed with an emphasis on comfort, but the result is a vehicle that rolls and pitches while

driving and during turning and braking. In sports cars, where the emphasis is on control, the

suspension is designed to reduce roll and pitch, but comfort is sacrificed. Bose engineers took

a unique approach to solving this problem, and the result is an entirely new approach to

suspension design.

Solution: In 1980, Bose founder and CEO Dr. Amar Bose conducted a mathematical study to

determine the optimum possible performance of an automotive suspension, ignoring the

limitations of any existing suspension hardware. The result of this 5-year study indicated that

it was possible to achieve performance that was a large step above anything available. After

evaluating conventional and variable spring/damper systems as well as hydraulic approaches,

it was determined that none had the combination of speed, strength, and efficiency that is

necessary to provide the desired results. The study led to electromagnetics as the one

approach that could realize the desired suspension characteristics.

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4.WORKING

The Bose system uses a linear electromagnetic motor (L.E.M.) at each wheel, in lieu of a

conventional shock and spring setup. The L.E.M. has the ability to extend (as if into a

pothole) and retract (as if over a bump) with much greater speed than a fluid damper (taking

just milliseconds). These lightning-fast reflexes and precise movement allow the wheel's

motion to be so finely controlled that the body of the car remains level, regardless of the

goings-on at the wheel level. The L.E.M. can also counteract the body motion of a car while

accelerating, braking and cornering, giving the driver a greater sense of control and

passengers less of a need for Dramamine. To further the smooth ride goal, wheel dampers

inside each wheel hub smooth out small road imperfections, isolating even those nuances

from the passenger compartment. Torsion bars take care of supporting the vehicle, allowing

the Bose system to concentrate on optimizing handling and ride dynamics.

A power amplifier supplies the juice to the L.E.M.s. The amplifier is a regenerative design

that uses the compression force to send power back through the amplifier. Thanks to this

efficient layout, the Bose suspension uses only about a third of the power of a vehicle’s air

conditioning system. There are a few other key components in the system, such as control

algorithms that Bose and his fellow brainiacs developed over a few decades of crunching

numbers.

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Fig4.1 Installed suspension unit in car

The target total weight for the system is 200 pounds, a goal Bose is confident of

attaining.

Suspension:

The main objectives of the suspension system are:

To prevent the road shocks from being transmitted to the vehicle parts, thereby

providing suitable riding and cushioning effect to the occupants.

To keep the vehicle stable while in motion by providing good road holding during

driving cornering and braking.

Provides safe vehicle control and free of irritating vibrations and reduce wear and

tear.

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The different types of suspension system which are available are mentioned below.

Front Suspension:

Solid I-Beam:

It’s a Non-independent design .These is used on trucks and other large vehicles. Its

economical and simple .It has low maintenance but poor handling.

Twin I-Beam:

Found on many Ford trucks. Its Forged, cast, or stamped axles. Has excellent load capacity. It

requires special equipment for alignment adjustments.

Mac Pherson Strut:

One of the most popular systems .It has one Control Arm. Ideal for front wheel drive. Light

weight and economical. Good ride quality and handling characteristics. It’s used for both

front and rear suspensions.

Short-Long Arm:

Independent design uses an upper and a lower control arm uses either torsion bars or coil

springs Good ride quality and handling characteristics Heavy and complex design requires a

lot of space.

Rear Suspension:

Non Independent Rear Leaf Springs:

It’s a non-independent design Similar to front solid I-beam axle. Used for large load carrying

capacity.

Non Independent Rear Coil Springs:

It’s a non-independent design .Uses coils and control arms instead of leaf springs. Has good

load carrying capacity.

Trailing Arm:

It’s an Independent Design Uses individual lower control arms. Uses coil springs and shocks

for good ride quality.

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Beam:Non-independent design Stamped beam axles. Uses coil springs and trailing arms. Used for

light and simple design.

Bose suspension front corner module

Fig4.2 suspension in front wheelThe Bose suspension system installs easily into the front of the vehicle. A new engine cradle

connects the front suspension to the car body using the original factory mounting hardware,

creating a drop-in replacement module. Bose's front suspension modules use a modified

MacPherson strut layout and the rear suspension modules use a double-wishbone linkage to

attach a linear electromagnetic motor between the vehicle body and each wheel. Torsion

springs are used to support the weight of the vehicle.

In addition, the Bose suspension includes a wheel damper at each wheel to keep the tire from

bouncing as it rolls down the road. Unlike conventional dampers, which transmit vibrations

to the vehicle occupants and sacrifice comfort, the wheel damper in the Bose system operates

without pushing against the car body, maintaining passenger comfort.

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Linear motor:

Fig4.3 linear motor

Linear motor is essentially a multi-phase alternating current (AC) electric motor that has had

its stator "unrolled" so that instead of producing a torque (rotation) it produces a linear force

along its length. The most common mode of operation is as a Lorentz-type actuator, in which

the applied force is linearly proportional to the current and the magnetic field (F = qv × B).

Many designs have been put forward for linear motors, falling into two major categories,

low-acceleration and high-acceleration linear motors. Low-acceleration linear motors are

suitable for maglev trains and other ground-based transportation applications. High-

acceleration linear motors are normally quite short, and are designed to accelerate an object

up to a very high speed and then release the object, like roller coasters.

They are usually used for studies of hypervelocity collisions, as weapons, or as mass drivers

for spacecraft propulsion. The high-acceleration motors are usually of the linear induction

design (LIM) with an active three-phase winding on one side of the air-gap and a passive

conductor plate on the other side. The low-acceleration, high speed and high power motors

are usually of the linear synchronous design (LSM), with an active winding on one side of the

air-gap and an array of alternate-pole magnets on the other side. These magnets can be

permanent magnets or energized magnets. The Transrapid Shanghai motor is an LSM.

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Fig4.4 bose suspension system

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5.COMPARISON

On A Bumpy Surface: Two vehicles of the same make and model are driven over a bump

course at night.The vehicle on the top has the original factory installed suspension and the

vehicle on the bottom has a BOSE suspension system. Both vehicles are being driven at the

same speed. The lexus with the standard factory installed suspension (below).

Fig5.1 A Lexus with a standard suspension

Joggles as it coasts along a bumpy surface, while another Lexus with the BOSE suspension

system (below) sails along the same road unperturbed.

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Fig5.2 A Lexus with the Bose system

Body Roll While Cornering: Two vehicles of the same make and model are shown

performing an aggressive cornering maneuver.

Fig5.3 A Lexus with a standard suspension

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Fig5.4 A Lexus with the BOSE suspension

In the photo, the Lexus car without the BOSE system leans as it turns a corner, while the car

with the Bose system remains stable.

Body Pitch on braking & accelerating: The front end of the car dips when the driver of a

Lexus fitted with the standard factory fitted suspension system slams brakes. In a Lexus with

the BOSE suspension system; drivers quickly notice the elimination of body pitch during

hard braking and acceleration. Professional test drivers have reported an increased sense of

control and confidence resulting from these behaviors.

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6.VEHICLE PERFORMANCE

Vehicles equipped with the Bose suspension have been tested on a variety of roads and under

many different conditions, demonstrating the comfort and control benefits drivers will

encounter during day to-day driving. In addition, the vehicles have undergone handling and

durability testing at independent proving grounds. When test drivers execute aggressive

cornering maneuvers like a lane change, the elimination of body roll is appreciated

immediately. Similarly, drivers quickly notice the elimination of body pitch during hard

braking and acceleration. Professional test drivers have reported an increased sense of control

and confidence resulting from these behaviors. When test drivers take the Boss suspension

over bumpy roads, they report that the reduction in overall body motion and jarring vibrations

results in increased comfort and control.

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7.FEATURES

The system draws about two horsepower or one-third the load of a typical air

conditioner. While it can exert 50 kilowatts (67 horsepower) of energy to leap a

2x6(plank) covers 49 kilowatts cushioning the landing, with the shocks working like

generators.

Torsion bars and shock units weigh about what two conventional springs and shocks.

The controllers and upsized alternator also add some weight, but the total should be

less than that of a hydraulic active suspension.

The system lets a vehicle ride lower at highway speeds to produce less drag and

improve handling

To save power the system is regenerative. When the far side of a pothole helps to

push the wheel up almost all the power is recovered. The motors momentarily become

generators, shunting the recovered energy to storage, either in the engine battery or in

some other device. The system ends up consuming one-third of the energy used by a

cars air-conditioner.

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8.DISADVANTAGES

Every system has some disadvantages attached to it.Some of the drawbacks can be

grouped as below.

The main drawback of the system is the cost.As it uses nyodinium magnets which

are costly to manufacture. Thus this makes this suspension system costlier than any

other suspension available.Thus this system can be seen in only high end cars

The second drawback is ,when this system breakdowns its very difficult and costly

affair to repair it .The other system available can be easily be repaired

The system is very complex and requires high precision machinery and skilled

workers to manufacture

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9.FUTURE PROSPECTS

Dr. Bose stated that within five years the company hopes to have the Bose suspension

offered on one or more high-end luxury cars, and thanks to the system's modular design, it

shouldn't be much of a problem to install at the factory. A manufacturer will be chosen to co-

develop a production application for sale after three or four years.

GM is expected to be the first development partner, given the long relationship

between the companies. The biggest setback would be the cost as it is going to cost more than

any suspension does now. The neodymium iron in the magnets is the most expensive part.

Expect to see electromagnetic suspensions only on very expensive cars first, and probably

never on cheap ones, though we imagine that the cost would come down as production goes

up.

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10.CONCLUSION

For the first time, the Bose suspension demonstrates the ability to combine in one automobile

a much smoother ride than any luxury sedan, and less roll and pitch than any sports car. This

performance results from a proprietary combination of suspension hardware and control

algorithms

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11.REFERENCE

1. “Electromagnetic Suspension Systems”,

http://www.bose.com/learning/project_sound/bose_suspension.jsp.

2. “Bose Redefines Automobile Suspension System”, http

http://www.gizmag.com/go/3259/

3. “Electronic Suspension” http://auto.howstuffworks.com/car-suspension9.htm.

4. “Future of Car Suspensions”, http://www.wikipedia.com.

5. “Motorcycle dynamics” by Cossalter.

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http://www.wikipedia.com/


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Electro magnetic suspension system