1. Passive, Semi-Active and Active Suspension System

2. Definition:
Suspension system: a mechanical system of springs and shock absorbers that connect the wheels and axles to the chassis of a wheeled vehicle

3. The Function of suspension system:
The job of a car suspension are: - to carry the static weight of the vehicle - to maximize the friction between the tires and the road surface, - to provide steering stability with good handling (minimize body roll) - to ensure the comfort of the passengers (ability to smooth out a bumpy road).

4. The Function of Spring and Shock Absorber
The Function of Spring: to absorb shock energy from road bump and convert it into potential energy of spring
The Function of Shock Absorber: to dissipate shock energy from road bump without causing undue oscillation in the vehicle.

5. Classification of Suspension System
Passive
Semi-Active
- Orifice Based Damper
- MR fluid based Damper
Active
Slow Active
Fully Active

6. Passive Suspension
The damping value (Cs) of a passive damper is determined by the total orifice area (the number of hole) in the piston head.

7. Orifice based Semi-Active Suspension

8. MR fluid based Semi-Active Suspension

9. MR Fluid
Magnetorheological fluid is composed of oil and varying percentages of ferrous particles (20-50 microns in diameter) that have been coated with an anti-coagulant material.
Varying the magnetic field strength has the effect of changing the viscosity of the magnetorheological fluid.

10. Force – velocity relationship

11. Active Suspension System
Active suspension system uses hydraulic actuator to reduce the amount of external power necessary to achieve the desired performance characteristics and is able to exert an independent force on the suspension to improve the riding characteristics.

12. Schematic Diagram and Basic Configuration of Hydraulically Actuated Active Suspension System

14. Pneumatically Actuated Active Suspension System Developed in Autotronics Lab - UTeM

16. Active VS Semi-Active Semi-Active: Lower implementation cost
Lower power consumption
Easier to control
Simpler design
Easy to install
Disadvantage: damper constraint, the force range is limited, performance is not as good as active system

17. Active VS Semi-Active Active System: Wider range of force
No force-velocity constraint
Can achieve better performance (vehicle dynamics)
Disadvantages: power consumption is high, higher weight to power ratio, expensive, major modification should be made before installing active system into the existing vehicle