In a car body, structural vibrations are generated by the engine, the wheels, the chassis and the airflow, and propagate through the entire vehicle body. The low damping of the metallic car body causes the sound generated by these vibrations to circulate in the interior of the car (Hurlebaus et al, 2007).
In a car body, structural vibrations are generated by the engine, the wheels, the chassis and the airflow, and propagate through the entire vehicle body. The low damping of the metallic car body causes the sound generated by these vibrations to circulate in the interior of the car (Hurlebaus et al, 2007). With the rising demand for more silent vehicles, along with lighter weight for greater fuel efficiency, active control techniques may be able to supply more effective solutions than passive vibration control techniques. The active control of vibrations consists in the attenuation of structural excitation through the application of vibrations that are out of phase with respect to the ones created by the source. The out-of-phase signals are generated by actuators on the surface of the structure (Elliott, 2008). Active control techniques have already revealed to be more efficient than passive control at low frequencies (Paulitsch et al., 2007).
The performance of a control system depends on the number of actuators and the actuator positions on the structure. The first objective of this project is to investigate these two key problems through simulations on an aluminium rectangular panel using the elemental approach. The second objective is to study the effects of the changes in the curvature of the structure on the performance of the actuators. The outcomes observed in this second part will be important to the application of active control in cars, where curved surfaces such as the roof top are of interest for the installation of actuators.
The numerical experiments were conducted by using feedback control first with force actuators and then with inertial actuators. The simulations were run for a rectangular flat panel and curved square and rectangular panels. In each case, the structural performance and sound radiation were analysed and the optimal control and stability conditions were estimated. The results were verified using the finite element modelling software ANSYS. The effects of increasing curvature on the efficiency of control were investigated. Finally, the outcomes of the simulations were compared to experimental data based on impact hammer vibration measurement on an actual car roof top.