Vibration reduction on city buses: Determination of optimal position of engine mounts

This study is composed of three essential parts. The first part describes an indirect semi-experimental method which is used to reconstruct the excitation force of an operating diesel engine from the acceleration data measured at the mounting points. These internal forces can not be directly measured with force sensors; they have to be derived from the dynamic deformation of the engine support, so a theoretical analysis is carried out to derive the equations for the force re-construction.The second part deals with prevention of low frequency vibration of the powertrain from spreading to the rest of the vehicle. Three uncoupling techniques are used to minimize these vibrations. The first technique reduces the non-diagonal elements of stiffness matrix. The second technique uses the elastic axes decoupling criterion. The third technique uncouple the torque roll axis (TRA) by using the previously determined excitation efforts.In the third part, numerical and experimental results are discussed. The solicitations deducted and the positions of mounts allowing decoupling of the powertrain are presented.