Active suspension system of a 3 DOF quarter car using fuzzy logic control for ride comfort

Passenger ride comfort is considered to be of utmost importance in designing any suspension system. The primary objective of any suspension system in automobiles is to isolate the road disturbances experienced by the tyres from being transmitted to the passengers. ISO- 2631-1:1997(E) has provided certain guidelines to analyse ride comfort and also indicates the degree to which the vibration exposure will be acceptable. Hence active suspension systems are becoming crucial to improve ride quality and passenger comfort, in view of the established superiority over conventional systems. In this paper considering direction of vibrations acting on human body in the translational vertical direction of the coordinate system, bump analysis is carried out on a 3 DOF quarter car model. Since the system dynamics change with increase in the Degrees of freedom, fuzzy logic control is used to control active suspension of a 3-DOF quarter car model. The objective function of the fuzzy logic control has been defined to minimize the sprung mass acceleration and seat acceleration, and is evaluated by simulating the transient response to road perturbations. In this paper the study is extended to a quarter car (3-DOF) seat-suspension model instead of 2 DOF suspension systems, since the vibrations are transmitted to human body through broad contact area like buttocks when sitting. The performance parameters, chassis acceleration, seat acceleration, seat displacement and chassis displacements are analyzed and also the ride comfort levels are analyzed according to ISO-2631-1:1997(E). Results indicate more ride comfort to the occupants through the active suspension system with the proposed fuzzy controller rather than the passive suspension system.