This document discusses active suspension systems for vehicles. It provides information on different types of active suspension technologies used by various car manufacturers. These include magnetic ride control used in Cadillacs, electronic air suspension in Range Rovers, and active body control in Mercedes Benz cars. The document also covers quarter car models, optimal control approaches like LQR control, and active suspension control strategies. Key active suspension technologies are described in detail, including how they work and their benefits in improving ride comfort and vehicle handling.

1. Jan 2004 Mechanical and Industrial Engineering
Active Suspension System

2. Jan 2004 Behzad Samadi
Vehicle Dynamics
Lateral dynamics
Handling: transient and steady state cornering
Stability: rollover and yaw

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Vehicle Dynamics
Longitudinal dynamics
Acceleration
Braking

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Vehicle Dynamics
Vertical dynamics
Ride comfort: Noise, vibration and harshness (NVH)

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Vehicle Dynamics
Suspension design
Ride comfort
Road holding
Handling

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Active Suspension
Active suspension systems
move each wheel up and
down to control body motion
in response to road
abnormalities.
With an active suspension, a
vehicle can simultaneously
provide the smooth ride of a
soft suspension along with
superior handling associated
with a firm suspension.

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Car manufacturers
GM
Ford
Daimler Chrysler
VW
Toyota
…

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Cadillac SRX
Magnetic Ride Control

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Range Rover
Electronic Air Suspension (EAS)

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Mercedes Benz CL 55 AMG
Active Body Control (ABC)

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Adaptable Variable Suspension
AVS allows the driver to select from four suspension
settings - comfort to sports firm – at the flick of a
switch. Computerized sensors also monitor steering
and wheel speed to eliminate dive, squat, lean and
roll.

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Active Height Control Suspension
Low makes it easier for passengers to enter
and exit. High accommodates rough terrain.
It takes 10-15 seconds to raise the vehicle
and 3-8 seconds to lower it.

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Active Body Control
Active Body Control is an active suspension and damping
system which automatically adjusts the chassis settings to the
driving situation.
Body movements when moving off, cornering and braking are
reduced as necessary and the optimum level of damping is
provided.
The ABC chassis system offers sports car style responsiveness
without compromising comfort. This apparent conflict of
interests is resolved through a combination of active control and
passive damping.
http://www.mercedes-benz.com

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Active Body Control

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Active Body Control - Benefits
Reduced roll and pitch when braking
and accelerating
Less body roll when cornering
Sporty driving dynamics and optimum
comfort
Greater directional stability in all
situations
Self-leveling suspension

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Active Body Control
Sensors:
Level
Vertical acceleration
Lateral acceleration
Actuators:
High pressure hydraulic

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Body Control Damping

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Active Roll Control
TRW Automotive: http://www.trw.com

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Active Roll Control

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Dynamic Body Control

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Magne Ride
Delphi Automotive: http://www.delphi.com

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Magne Ride – How it works
Magneto-rheological (MR) fluid is a suspension of magnetically
soft particles such as iron microspheres in synthetic
hydrocarbon base fluid. There are two work states:
Not magnetized state: The particles exhibit a random pattern.
Magnetized state: The applied magnetic field aligns the metal
particles into fibrous structures, changing the fluid rheology to a
near plastic state.
By controlling the current to an electromagnetic coil inside the
piston of the damper, the MR fluid's shear strength is changed,
varying the resistance to fluid flow. By fine tuning of the
magnetic current, continuously variable real time damping is
gained.

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Magne Ride - Features
Simple monotube design with no electro-mechanical
valves or small moving parts
Improved performance and reliability over valve-
based competitive systems
Full software tunable damping characteristics provide
excellent low frequency body control without
excessive harshness at high velocities
Excellent roll control during transient steering and
evasive maneuvers
Wide range of force control and high bandwidth for
fast response
Low power requirements (20 W per damper max)

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Magne Ride - Benefits
Flatter ride -- by controlling vehicle body motions
Greater sense of safety and security -- due to
improved road-holding capabilities
Enhanced handling -- by controlling the lateral and
longitudinal load transfer characteristics of the
suspension during transient movements
Road isolation -- by reducing the transmission of
high-frequency road disturbances through the
dampers
Greater vehicle dynamics control when combined
with unified chassis control

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ROADMASTER
http://www.activesuspension.com

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Suspension control strategies

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Active suspension

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Quarter Car Model

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Quarter Car Model
Equations of motion:

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Quarter Car Model
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Optimal Control

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Optimal Control - LQR
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