The document outlines the evolution and technology of suspension systems, focusing on active and semi-active types that adapt to road conditions. It explains the principles behind high bandwidth systems and the benefits of hydraulic and electromagnetic actuated suspensions. Additionally, adaptive suspensions utilize sensors and computer algorithms to adjust shock absorber firmness for optimal performance and stability.

1. ACTIVE
SUSPENSION
History of Suspension and
latest technology in
suspension.
Submitted by:
Mayank Khare
SGSITS, Indore

2. • The story of old passive suspensions was
determined entirely by the road surface
only.
• The Skyhook theory is an idea that states
that an object can maintain a stable
posture if it is traveling suspended by an
imaginary straight line (Skyhook). The
theory forms the basis of Active
suspension.
• A vehicle contacts the ground through the
spring and damper in a normal spring
damper suspension, as in figure. To
achieve the same sustainability in the
Skyhook theory, the vehicle must contact
the ground through the spring, and the
imaginary line with the damper.
HISTORY OF
SUSPENSION
SYSTEMS

3. • Active
– Hydraulic actuated
– Electromagnetic recuperative
• Adaptive
– Solenoid/valve actuated
– Magnetorheological damper
• Some production vehicles with active
and semi-active suspension
TYPES OF
SUSPENSIONS

4. • An active suspension system has the ability to store,
dissipate and to introduce energy to the system. It may
vary its parameters depending upon operating conditions
and can have knowledge other than the strut deflection
the passive system is limited to.
ACTIVE SUSPENSION SYSTEMS

5. High bandwidth systems
• In a high bandwidth (or ``fully active'') suspension
system we generally consider an actuator connected
between the sprung and un-sprung masses of the
vehicle.
• A fully active system aims to control the suspension
over the full bandwidth of the system.
• In particular this means that we aim to improve the
suspension response around both the ``rattle-space''
frequency (10-12 Hz) and ``tyre-hop'' frequency(3-4Hz).
The terms rattle-space and tyre-hop may be regarded as
resonant frequencies of the system.
• A fully active system will consume a significant amount
of power and will require actuators with a relatively
wide bandwidth. These have been successfully
implemented in Formula One cars and by, for example,
Lotus [Wright 84]
ACTIVE
SUSPENSION’S
CONTINUED:

6. Low bandwidth systems
• Also known as slow-active or band-limited
systems.
• In this class the actuator will be placed in
series with a road spring and/or a damper.
• A low bandwidth system aims to control the
suspension over the lower frequency range,
and specifically around the rattle space
frequency.
• At higher frequencies the actuator effectively
locks-up and hence the wheel-hop motion is
controlled passively.
• With these systems we can achieve a
significant reduction in body roll and pitch
during maneuver's such as cornering and
braking, with lower energy consumption than
a high bandwidth system.
ACTIVE
SUSPENSION’S
CONTINUED:

7. • Hydraulically actuated suspensions are controlled
with the use of hydraulic servomechanisms.
• The hydraulic pressure to the servos is supplied by a
high pressure radial piston hydraulic pump. Sensors
continually monitor body movement and vehicle
ride level, constantly supplying the computer with
new data.
• As the computer receives and processes data, it
operates the hydraulic servos, mounted beside each
wheel.
• Almost instantly, the servo-regulated suspension
generates counter forces to body lean, dive, and
squat during driving maneuvers.
• In practice, the system has always incorporated the
desirable self-levelling suspension and height
adjustable suspension features, with the latter now
tied to vehicle speed for
improved aerodynamic performance, as the vehicle
lowers itself at high speed.
HYDRAULICALLY
ACTUATED ACTIVE
SUSPENSIONS

8. • This type of active suspension uses linear
electromagnetic motors attached to each wheel.
• It provides extremely fast response, and allows
regeneration of power consumed, by using the
motors as generators.
• This nearly surmounts the issues of slow
response times and high power consumption of
hydraulic systems.
• Electronically controlled active suspension
system (ECASS) technology was patented by the
University of Texas Center for Electro-mechanics
in the 1990s and has been developed by L-3
Electronic Systems for use on military vehicles.
• The ECASS-equipped HMMWV exceeded the
performance specifications for all performance
evaluations in terms of absorbed power to the
vehicle operator, stability and handling.
ELECTROMAGNETIC
RECUPERATIVE

9. • Adaptive suspension is a computer-controlled
suspension system that varies shock absorber
firmness to match changing road or dynamic
conditions.
• Adaptive suspensions rely on a network of sensors
and a computer that optimizes the firmness of its
shock absorbers or struts based on the road surface
or the vehicle’s dynamics as it turns, brakes and
accelerates.
• The key to these systems is the variable-rate shock
or strut, the firmness of which can be changed in
fractions of a second.
• In these devices, an electric signal from the
computer varies the size of a valve through which
hydraulic fluid flows. (The movement of this fluid,
or oil, through valves is the basis of a shock
absorber’s operation.)
ADAPTIVE OR
SEMI-ACTIVE
SYSTEMS

10. • Basic type of semi-active suspensions.
• They consist of a solenoid valve which alters the
flow of the hydraulic medium inside the shock
absorber, therefore changing the damping
characteristics of the suspension setup.
• The solenoids are wired to the controlling
computer, which sends them commands
depending on the control algorithm (usually the
so-called "Sky-Hook" technique).
• Currently used in: This type of system used
in Cadillac's Computer Command Ride(CCR)
suspension system.
SOLENOID/VALVE
ACTUATED

11. • What sets it apart from other suspension systems is
the fact that it lacks any electro-mechanical valves
and it basically has no small moving parts. Instead,
the suspension is based on a magnetorheological
fluid (MR), a type of smart fluid, as it is called,
which reacts to a magnetic field.
• The use of a MR suspension system allows for a
better ride due to the flat and stable ride it ensures.
System allows for the action of each wheel to be
smoothened and isolated. The system can be
integrated with vehicle’s stability control to
enhance stability on gravel, and slippery road
surfaces. Thanks to the ECU's software, the MR
system allows for a wide range of damping force
control and high bandwidth for fast response.
• Currently use in: MR will become more of a
common sight as soon as the cost issue is resolved.
So far, the range of vehicles to use such a system
includes Acura MDX, Audi TT, Audi R8, Cadillac
DTS, SRX, STS, Chevrolet Corvette, Ferrari 599
GTB and Holden HSV Commodore.
MAGNETO-
RHEOLOGICAL
(MR)DAMPER

12. • http://www.autoevolution.com/news/how-
magnetorheological-suspension-works-
8947.html#ixzz4GwxUNxpp
• http://www.bwigroup.com/en/pshow.php?pid=22
• http://www.cvel.clemson.edu/auto/systems/active_susp
ension.html
• http://smartmastertrainer-
academy.blogspot.in/2013/08/electronic-control-
suspension-system.html
• https://w220.ee/Airmatic
• http://voitlab.com/courses/thermodynamics/index.php?
title=Imad_Zahid
REFERENCES: