Analysis and design of active suspension system for motor vehicles

The main functions of the suspension system are to isolatethe body of the vehicle from vibrations due to irregularities inthe road surface and to provide vehicle stability and directionalcontrol during handling manoeuvres. In addition, the suspensionshould be insensitive to externally applied loads, such ascross-wind aerodynamic forces and cargo load variations. Theconventional type of the suspension system, which is called aconventional passive suspension system is considered to containonly springs and dampers whose rates are not capable of beingchanged by external signals. Hence the designer is faced with theproblem of choosing the suspension stiffness and dampingcoefficient of a fixed values, which inevitably involves adifficult compromise in view of the wide range of conditions overwhich a vehicle operates. Although many passive suspension designsare realised in an inexpensive, reliable, and satisfactory mannerwith passive elements, it is clear that there are distinctperformance limitations when only passive elements are used.Nowadays, modern vehicle suspensions contains levelling systemswhich automatically adjust the static ride height of the vehicleaccording to the change in the suspension load or sprung mass.with recent advances in micro electronics and actuators, there hasbeen an upsu;rge of interest in the concept of active suspensioncontrol.