Nonlinear modeling and control of automotive vibration isolation systems

The vertical response of light-duty vehicles depends on the suspension system design parameters. Although the packaging may differ, suspension systems contain springs and shock absorbers to isolate the occupant from road surface irregularities to provide a satisfactory ride. This approach has provided acceptable results for paved road, but does not offer an ideal solution for off-road applications where the driver may be subjected to prolonged vibrations at higher levels. Therefore, the design of semi-active and active suspension systems have been pursued to attenuate the vibrations between the vehicle´s sprung and unsprung masses. However, this approach tends to be expensive (e.g., actuators, sensors, and computational burden) and power intensive (e.g., hydraulic or pneumatic sources). An attractive alternative is the placement of the isolation system in the passenger compartment between the vehicle floor and driver´s seating system to minimize the vibrations transmitted to the occupant´s lower and upper torso. In the paper, two vibration isolation systems have been proposed which use hydraulic and electromechanical components to provide semi-active and active operation. Dynamic models with attached controllers are presented for each actuator to provide vibration attenuation for vehicles subjected to road disturbances. Representative results are discussed and metrics introduced to quantify the performance gains available through each actuator´s design and control strategy