Article need for advanced suspension systems

Need for Advanced Suspension Systems

Suspension systems have significantly contributed to vehicle’s safety as well as in
the enhancement of its life span. A good suspension system protects vehicle from
undue wear & tear, which in turn increases the life-span of the vehicle. In this
context, vehicle’s application is very useful for providing its availability. Moreover, it
proactively plays an active part in rendering comfort to vehicle occupants. In
modern times, the significance of suspension systems is much valued than it was
decades ago. Today, the manufacturers have certainly prioritized incorporating
advanced suspension systems in its vehicles, in order to render controllability,
stability and many other component attributes onto its vehicle occupants. Also,
patenting of its suspension system design is carried out by certain vehicle
makers. Future trends of advanced suspension systems could be reflected from
representative patents and innovations in the arena of suspension systems.

Achieving State of Art Suspension systems
Driving comfort and safety is one of the functionalities of vehicle suspension
system. A good suspension system is the efficient carrier of the vehicle body or
its framework, so as to proportionately distribute all forces between the road and
the vehicle body. In order for the suspension system to suit any driving
conditions, introduction of active and semi-active components is mandatory. Fixed
setups of suspension should be technically enhanced by making alterations in
variable shock absorber or springs so attached to it. For instilling efficacy in vehicle
suspension systems, the control behavior of its components ought to be studied.
Also, adapting to certain parameters in relevance to driving excitations must be
understood. It is equally pertinent to identify as well as detect if any faulty
components persist, in order to accommodate design of suspension system. As

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any discussions on suspension systems brings forth the essence of driving safety
and driving comfort, it would be optimal to elaborate these two widely used terms.

Driving Safety
It is meant to signify an optimal suspension design with harmonious combination of
springing, braking, and steering as well as wheel suspension. A quantitative value of
safety can be evaluated by variation in Tire load indication.

Driving Comfort
A quantitative value of Driving comfort can be evaluated by car’s quantity for
motion and vibration of its body. Moreover, in determining Driving comfort level of
any suspension system, it is optimal to keep the external values such as climate
conditions, external noises and vibrations to lowest possible limit, so as to effect an
optimal evaluation of its quantitative value.

The following depict key pointers so as to achieve optimal performance from
suspension systems:

1) It is essential to decrease the frequency sensitive to human body by
decreasing sprung mass peak to near 1 Hz. while attempting to isolate the
sprung mass from other road disturbances. In doing so, suspension system
can achieve greater scalability in the ride quality.

2) For improving stability of the ride, it would be optimal to decrease resonance
frequency of the wheel to around 10 Hz., while essentially keeping the
contact between the road and the tire intact.

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3) A larger deflection in suspension can be sought by using road disturbances to
effect sprung mass to isolate better in relevance to a suspension spring.

4) It is necessary to note that unnecessary suspension deflections, if prevented
with appropriate damping, could enable achieve better road contact.

5) Driving stability and quality thus demand criteria which are pretty conflicting
to each other. It is suggested that for any set of data input in specific stress
and road conditions, comfort and safety will always be compromised where
the passive suspension system is fixed

6) It is also suggested that active or semi-active suspension systems strive to
lessen the conflict.

7) Semi-active suspension systems are based on the theory of meeting the
actual demands by making stiffness of spring and/or damping adapting to
them

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8) However, the mechanism of active suspension system requires an addition
or input of extra force to the already existing passive systems. Thus, active
suspension system is based on mechanism of addition, rather than
adaptation unlike semi-active suspension systems.

9) Any unnecessary loss in performance of active or semi-active suspension can
be prevented by taking changes in parameters such as wear & tear,
temperature, variation in certain other external factors, during process of
designing controller for the aforesaid suspensions. This can also be prevented
by adapting a robust controller by which changes in system behavior could be
controlled by its signals

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Ensuring safety through the concept of Brake-friendly Suspension
Controllable suspension and advanced brake control systems are incorporated in
most of the vehicles in higher segments. Semi-active dampers are the chosen
controllable suspension systems for these purpose. The switching between
emergency modes and normal operative is the presumption in active safety chain
for effectuating real integration of suspension controls. The comfort objectives shall
be the parameters considered to control vehicle suspension in operative mode. The
application of specialized optimized algorithms has to be considered for control of
suspension in emergency mode. Advanced algorithms which have ability to trace
the full potential of vehicle controllable suspension will be used for manoeuvres as
emergency braking.

Concept of Brake-Friendly Suspension
Emergency braking manoeuvre includes Tires which play intermediary or as a
interface between the road and the vehicle. The nonlinear attribute of the coupling
dictates its dependence on varied parameters. The vertical load Fz and the
longitudinal slip κ: µ = µ(Fz,κ), which carries the coefficient between tire and a
given road, causes fluctuation in vertical tire to have influence on breaking distance.
The extension of stopping distance arises as a result of nonlinearity from the
oscillations of vertical force. In the case where braking is completely interrupted,
the decrease in scenario of losing contact between tire and road is effectuated by
controlled suspension. ABS algorithms depict these undesirable situations in worst
scenarios. That the vehicle has not braked during the interval of losing and gaining
contact, is the direct consequence of ABS algorithm and its sampling.

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The mere tradeoff between comfort and road handling are satisfied by current
vehicle suspension designs. Active and Semi-active systems are suggested to
increase performance in suspension systems, considering that passive suspension
design has been almost pushed to its limits. Semi-active systems propose the use of
fail-safe and low energy demands. Certain undesirable vibrations and shortening of
braking distance can be suppressed by optimization of braking manoeuvre and with
the aid of efficiently controlled vehicle suspension system. This is what brake-
friendly suspension can mean to be, so achieved by eradicating the vertical forces of
fluctuation between road and tire. This objective has to be achieved in order to
ensure safety via advanced suspension systems.

Global Trend towards vehicle weight reduction
The EU regulatory authorities have proposed that 2020 vehicle manufacturing
targets fulfil requirement of having lighter cars. The regulatory authorities have
endorsed one of the technical requirement of 2020 fleet of passenger cars would be
to have emissions of not more than 95g CO2/km. This restriction in carbon emission
would in fact set trend for every manufacturer indirectly lower the weight of the car.

Manufacturers have adhered to the proposed regulatory requirement by bringing
innovative tools to effect weight reduction in cars. In the process of doing this, CFRP
structures are going to replace metal structural components in car’s seating
arrangement, thereby effecting 20% reduction in weight via polyamide structures
used in seats. Moreover, plastic and certain other materials which are suggested to
replace PU foams will further reduce weight in overall seating. Along with innovative
materials, the market is pampered with innovative designs such as TU Delft and
BMW massage system in order to adhere with weight reduction requirement.

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With European commission striving to make Europe a zero carbon society by 2050,
vehicle manufacturers will have to adhere to certain stringent regulatory targets,
which in fact would enable production of lighter cars by using innovative materials
and design. This is sure to benefit the consumers who will get the best of both the
worlds - Quality and Performance.

Determinants of Advanced Suspension systems
Vehicle manufacturers are constantly striving new ways to quench their customer
needs in advanced suspension systems, by optimizing manufacturing standards
and improve applications of manufacture. In fact, the type of suspension to be used
on vehicle will be decided by the application of the vehicle. Moreover, whether
suspension would be a spring or an air will be determined by different performance
metrics, roll stability and durability aspects as well.

Although application of vehicle is one of the determinants in choosing suspension
system, it is unanimously agreed that the key determinant of suspension system
is their ability to handle pressures of different environment. For e.g. spring
suspensions are optimal for highway trailer but could be not so useful on a BMW.
Different company manufacturers think of different priorities in manufacture of
advanced suspension systems. For some it is still the old process manufacturing
suspensions that is important, so long as the suspensions are proven to fulfil their
customer needs. While for some others, the manufacturing line focuses on
productivity and zero maintenance to its end users. Such manufacturers make
suspensions which offer its customers minimal initial investment and almost
negligible long term maintenance. Yet for some others, it is the type of suspension
which makes important part of its customer’s choice. For instance, certain
manufacturers thrive on manufacturing Air suspensions on the basis of it comprising

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of air systems which along with air bags can be susceptible to break downs. Air
suspensions are termed essentially to be highway applications, which are
appropriate for fast cars to render comfort to its passengers and drivers preferring
high speed dynamics from suspension. Moreover, irrespective of whatever the
chassis load is, Air suspension with its optimized spring rate assists vehicle
optimally on on-highway trail. However, for vehicles that have high center of gravity
and which are more or less of off-road nature, Air suspension may not suffice.

Certain manufacturers prefer manufacturing suspensions that would enable
eliminate the need of certain other components within suspension systems. For
e.g. the mechanics involved in spring suspensions, eradicate the necessity for shock
absorbers via process of self-damping. Moreover, these suspensions maintain a
constant spring rate. Irrespective whether the vehicle is loaded or not, the spring
rate will be constant. However, for some spring suspensions lack good roll stability
attributes for enabling a free flowing smooth ride. The maintaining of constant
spring rate is not always good as this attribute of spring suspensions causes an
uncomfortable or stiff ride for operators. Therefore to overcome this problem its
manufacturers have introduced rubber spring suspensions. As these provide highly
variable spring rate, the ride provided by them is better than the ordinary spring
suspensions.

Lighter weight suspensions
Suspension companies are now optimizing their product line by introduction of
lighter weight suspension systems. For doing this, the use of higher strength steel
is made. Higher strength steel enables the same durability and desired carrying
capacity from manufactured suspension systems. In fact the use of higher
strength steel saves the company of the amount of steel being used in suspensions

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manufacture, thus aiding in reducing the manufacturing costs. This innovative
technique is used for manufacturing lighter weight suspension springs as well as the
frame.

The weight of suspensions can also be reduced by using rubber spring technology.
In fact, the rubber springs weigh much less, although they have the endurance to
carry the same weight as higher steel suspensions. While a rubber spring weighs
less than 900 lbs., a steel spring could weigh between 1200 to 1400 lbs.

Reduction in suspension weight can be also effected by post vulcanized bonding
process as well. The PV bonding process eradicates the need for clamps or bolts,
thereby causing in overall reduction of suspension weight.

Future trends in Suspension systems
Suspension design will continue to face optimization and innovation from
manufacturers. For e.g. efforts taken by manufacturers to reduce weight is due to
benefits derived from weight reduction as well as compliance with regulatory
authorities. Likewise, suspension systems will continue to face investigations for
entry of new technologies or to aid existing technologies enables other process
applications. As aforesaid, advanced suspension systems does not necessarily
mean new innovative technologies or its applications, but also mean to perceive
what the manufacturers or the end users perceive it to be. However, it is essential
to find the right suspension for particular applications enable its function rather than
searching for a new technology suspension system without reference to vehicle
application or its end user. It will although be optimal for a manufacturer to produce
suspension system providing safety, comfort, durability, with minimum costs and
weight.

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References:

http://www.carbibles.com/suspension_bible.html
www.frost.com
www.benthamscience.com
http://autoshepherd.com/category/Steering-Suspension/1072

Want to know more about suspension systems?
Check out our Download Centre, where you will find more articles,
white papers and interviews regarding this topic:
http://bit.ly/suspension-articles

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