Modeling and optimization of passive and semi-active suspension systems for passenger cars to improve ride comfort and isolate engine vibration

Suspension systems have been widely applied to vehicles, from the horse-drawn carriage with flexible leaf springs fixed at four corners, to the modern automobile with complex control algorithms. A good suspension system should provide a comfortable ride and good handling within a reasonable range of deflection. Though a passive suspension system can perform this task, its parameters are generally fixed, being chosen to achieve a certain level of the compromise between comfort and handling. The loads acting on the suspension system may be on-board and off-board, the latter being the road loads and the former being characterized mainly by vibrations induced by the engine. The primary object of this study is to improve ride comfort for a passenger car, first by optimising the values of stiffness and damping coefficient for a passive suspension system, and then by introducing a semi-active control system that makes use of sky-hook control methods.