1. ACTIVE SUSPENSION SYSTEM
BY VIJAYKUMAR R. SACHANE
SEMINAR TOPIC

2. Introduction to SUSPENSION
SYSTEM
 Suspension is the term given to the system of
springs, shock absorbers and linkages that
connects a vehicle to its wheels
 Serve a dual purpose – contributing to the car's
handling and braking.
 Protects the vehicle itself and any cargo or
luggage from damage and wear
 In suspension systems, usually two most
important features are expected to be improved
– disturbance absorbing (i.e. passenger comfort)
and attenuation of the disturbance transfer to
the road (i.e. car handling).

3. WHAT IS AN ACTIVE SUSPENSION
SYSTEM
 The Active or adaptive suspension is an automotive
technology that controls the vertical movement of the
wheels with an onboard system rather than the
movement being determined entirely by the road
surface.
 It has two main functionalities, one is to isolate the
vehicle body with its passengers from external
disturbance inputs which mainly come from irregular
road surfaces.
 The other is to maintain a firm contact between the road
and the tyres to provide guidance along the track.

4. The basic function of the vehicle suspension is to
provide comfort to passengers, maximize the
friction between the tyres and the road surface and
provide steering stability with good handling.
In active suspension systems, it employs springs as
the main form of support, however the dampers can
usually be controlled.
A active suspension has the ability to change the
damping characteristics of the shock absorbers
without any use of actuators.

5. SUSPENSION SYSTEM – LAY OUT

6. IMPORTANT PROPERTIES
Spring rate
 The spring rate (or suspension rate) is a component in
setting the vehicle's ride height or its location in the
suspension stroke.Vehicles which carry heavy loads will
often have heavier springs to compensate for the
additional weight that would otherwise collapse a vehicle
to the bottom of its travel (stroke).
 Springs that are too hard or too soft cause the
suspension to become ineffective because they fail to
properly isolate the vehicle from the road.
 Vehicles that commonly experience suspension loads
heavier than normal have heavy or hard springs with a
spring rate close to the upper limit for that vehicle's
weight.

7. DAMPING
 Damping is the control of motion or oscillation, as
seen with the use of hydraulic gates and valves in a
vehicles shock absorber.This may also vary,
intentionally or unintentionally. Like spring rate, the
optimal damping for comfort may be less than for
control.
 ROLL CENTER HEIGHT
 This is important to body roll and to front to rear roll
stiffness distribution. However, the roll stiffness
distribution in most cars is set more by the antiroll
bars than the RCH.The height of the roll center is
related to the amount of jacking forces experienced.

8. VIBRATION MODES OF THE
SUSPENSION ELEMENTS
SUSPENSION SPRINGS
Suspension Springs are the suspension system's
primary line of defense.

9. These variables within the surface of the
street or the backcountry road send force
up through the wheels. .
The suspension spring's task is to absorb
this power and carry your wheels back to a
condition of equilibrium.
You will find several standard types
of Suspension Springs used on
contemporary vehicles: Leaf Springs, Coil
Springs,Torsion Bars, and Air Springs.

10. SUSPENSION BUSHINGS
Suspension Bushings connect your expensive
suspension components together, serve as protective
seals to connection points, and are vital to how they
function.
They make a perfect connection between the
different parts of your suspension system. This
results in perfect suspension alignment and
drastically better handling.

11. SHOCK ABSORBERS (DAMPERS)
It is a device that controls unwanted spring motion
through a process known as dampering.
 ShockAbsorbers slow down and reduce the magnitude
of vibratory motions by turning energy of suspension
movement into energy that can be dissipated through
hydraulics.
A ShockAbsorber is placed between the frame of the
car or truck and the wheels.

12. WORKING OF ACTIVE
SUSPENSION SYSTEM
The active suspension can be arranged in series
OR parallel combination with the passive
suspension such as spring
 The sensor is attached at the top cover to
measure the motion of the suspension system.
 It uses one or more sensors that can generate
sensor signals to indicate the motion.
Then it is coupled to controller having processor.
 It receives the signal & generates control signals.
The control signals are transmitted to amplifier
that drives active suspension element.

14. Sensors And Controller

15. Roll on Corners

16. Some productions vehicles with active
Suspension
Mitsubishi Galant- "Dynamic ECS", world’s first production
semi-active electronically controlled suspension
system(1987)
BMW M3 - "BOGE adjustable damping" system(1989)
Infiniti Q45 - "Full-Active Suspension (FAS)", world's first
production fully active suspension system(1990)
Lexus GS- Active Stabilizer Suspension System(2007)

17. DIFFERENCE BETWEEN ACTIVE &
PASSIVE SUSPENSION SYSTEM

18. Let us consider the work of passive vibration isolation
system by the example of a suspension bracket of the
automobile. In any suspension bracket there are
elastic elements, which soften pushes and impacts of
the road. Other not less important element of a
suspension bracket is the shock-absorber -- the device
which is intended to terminate excited the oscillation.
Many drivers think that shock-absorbers is only the
means to maintain comfort. Actually functions of this
element of a suspension bracket are directly
connected to maintenance of contact of a wheel with
road, i.e. with controllability of the automobile and
traffic safety.

19. First animation shows that too hard suspension
system of a car results in throwing of the car on
unevenness of the road, while too soft suspension
system will swing the car, which results in lost of the
contact between the wheels and the road.
In second animation active vibration isolation
system among the spring there is feedback circuit
which consists of a piezoelectric accelerometer, an
analog control circuit, and an electromagnetic
transducer.The spring supports the weight of the
table top and the device which is mounted on the
table.The motion of the table top is detected by a
highly sensitive piezoelectric accelerometer
consisting of a mass resting on a piezoelectric disc
and covered by a housing.

20. MATHEMATICAL MODEL OF ACTIVE
SUSPENSION SYSTEM
 The model can be used for determining the
adjustable arm’s angle for which the system
produces a required force.
 The trailing arm joins the unsprung mass (wheel
unit) to the sprung mass (the car body) and
provides a connection to the primary spring and
damper.The adjustable arm defines the position
at which the secondary spring is attached to the
suspension system.

23. Where
For small suspension deflections, it is assumed that
the point at which the secondary spring is attached to
the suspension system moves along a circular
trajectory
Where

25. ADVANTAGES
 Improved Steering, Handling and
Braking
In a rigid suspension, if one wheel jogs or bounces, the entire
axle tilts, causing the opposing wheel to tip in or out at the top,
no longer rolling straight ahead, an effect called "bump steer".
Rigid axles are also less responsive on turns and vehicles
carrying heavy loads are subject to instability called "shimmy",
caused by forces translated across the axle from wheel to
wheel.
During hard braking, solid beam suspension can cause the
front of the vehicle to nose dive and twist. Independent front
suspension (IFS) corrects or vastly improves all of these effects
by allowing wheels on the same axle to respond independently
to driving conditions.

26.  Ride Quality
Ride quality is a concern that has evolved with our
culture's increasing dependency on automobiles for
recreational and commuter travel.
 Overall ride quality, or how comfortable a car feels to ride
in or drive, is measured by a combination of factors,
including noise and vibration, the translation of bumpy road
surface to passengers, the smoothness of the car's steering
and how well a car handles and corners.
Active suspension system solves some of these problems
by de-coupling the front wheels, improving overall stability
and creating isolation between the suspension and the
vehicle chassis.

27.  Size and Fuel Efficiency
It is difficult to beat a solid axle for strength and
simplicity, but the price of that strength is size and mass.
For heavy duty vehicles and the solid steel cruisers of the
1940s and 1950s, a rigid axle made good design sense.
 As passenger vehicles have gotten smaller and more
performance-oriented, heavy, bulky, rigid axles are no
longer practical, particularly because heavier vehicles burn
more fuel. Independent front suspensions have evolved
with modern car materials, creating lighter, more flexible
and responsive vehicles.

28. DISADVANTAGES
Need for a large external power source
Complex control algorithms
Complex closed-loop control systems.
Requirement of fast-acting devices
Increased cost

29. In the case of active suspension system, as in any
other innovations of automotive technology, today's
innovation is tomorrow's standard feature.
Inspite of its high initial cost, let us expect to see
them in the Indian roads soon.The trickle-down
effect will take some time, but it'll happen and when
such a time comes we can expect much lesser
accidents, less fatalities and more comfort in driving
the roads.
Conclusion

30. THANK YOU