ACTIVE vs SEMI-ACTIVE SUSPENSION ANALYSIS

MODULE OBJECTIVE :

At the end of this module, trainee must be able to :

1. Understand difference between active and semi-active suspension.

2. Understand between active and passive suspension

3. Hydraulic Actuated Systems

4. Electromagnetic Recuperative

5. Solenoid/valve Actuated

6. Magneto Rheological Damper

TYPES OF SUSPENSIONS

Fig.1 : Types of Suspensions

• Passive
• Movement determined entirely by surface vehicle is riding on.

Fig.2 : Bicycle is passive or no suspension system

• Semi-Active


• Only changes viscous damping coefficient of shock absorber.

Fig.3: Semi-Active Suspensions System

• Active
• Use independent forces on the suspension to increase riding characteristics.

Fig.4: Active Suspension system layout in vehicle

Fig.5: Shock Absorber layout for active suspension system.

Fig.6: Active Suspension system in axle location.

Fig.7: Active Suspension on bus using Air Suspension System

Fig.8: Voice-Coil-Motor System for Active Suspension System

Active Vs. Passive Suspension

Advantages                                                                      

• Virtually eliminates body roll and pitch variation.               
• Better ride quality                                                                 
• Better handling                                                                        

Disadvantages

• Expensive
• Added Complication
• Can be difficult to reliably diagnose

Hydraulic Actuated Systems

Fig. 8: Hydraulic Actuated Systems

žControlled by hydraulic servomechanisms

žžSelf Leveling and Height Adjustment

žLowers height at high speeds

žžDeveloped in 1980’s

Electromagnetic Recuperative

žBose System

                Released in 2009
Uses Linear Electromagnetic motor at each wheel

Possible “Drop-in” Installation

Fig.9:  Electromagnetic Recuperative in vehicle.

Solenoid/Valve Actuated

Most basic semi-active suspension

žžAlters flow of hydraulic fluid inside shock absorber

Air ride suspensions

Fig.10: Air Suspension system

Fig.11: Pneumatic components for air suspension system

Fig.12: Air Suspension system on vehicle

Magneto Rheological Damper

žAudi System

Magnetic field changes alignment of the particles

Increasing current flow in damper raises spring stiffness

—žOriginally developed in the 1980’s

Finding increased usage in the USA

Fig.13:  Magneto Rheological Damper

Conclusion

Active Suspension

žMore expensive

žProvides extremely good suspension performance

žžProvides excellent ride quality

žžVery complex systems, since the vehicle must be able to manipulate the suspension in many different ways. 

Semi-Active Suspension
žMuch cheaper
žPerformance can be very comparable to active suspension
žRide quality also can be very similar to active suspension
žMuch simpler systems than active suspensions, since only the damping coefficient changes

Resources informations:

žhttp://eprints.utm.my/2578/1/JTjun44D%5B3%5DCRC.pdf

ž žhttp://en.wikipedia.org/wiki/Active_suspension

ž žhttp://www.activeshock.com/main_semi_active_suspension.htm

ž žhttp://www.gizmag.com/go/5752/picture/24202/

ž žhttp://www.bose.com/controller?url=/automotive/bose_suspension/applied_learning.jsp

ž žhttp://www.ferraricars.org/img/ferrari-360-spider/suspension-03.jpg

ž žhttp://www.carbibles.com/docs/racecar.pdf

ž žhttp://www.carbibles.com/suspension_bible_pg3.html