Partial Natural Torsional Frequency Modification of Vehicle Driveline Considering Modal Damping

Torsional resonance is a common phenomenon in engineering vehicle drivelines. To avoid the influence of resonance on the driveline, it is typical to modify the frequency. However, traditional frequency modification methods cannot precisely achieve expected frequencies while keeping others unchanged. They often cause frequency ‘overflow’ and fail to account for the influence of modal damping on drivelines. To address the issues above, a passive modification method is proposed to modify the natural frequencies of engineering vehicle drivelines, considering modal damping. In this paper, the dynamic equations for gears and shafts are derived by a lumped-parameter model that employs the Lagrange method to establish a reasonably equivalent model as a serial-parallel system consisting of (moment of inertia)-(torsional spring)-(torsional damper) with free boundary conditions. Additionally, the passive structural modification for the partial eigenvalue assignment (PEVAPSM) method is employed to modify the specified partial natural torsional frequencies to realizable expected values, while others remain unchanged. The modal damping of the original driveline is modified based on the orthogonal decomposition method. Finally, the practical applicability of the method proposed in this paper is demonstrated through a specific example. Results indicate that the PEVAPSM method has been successfully extended and supplemented from a theoretical translational system, ignoring modal damping, to a practical torsional system considering modal damping to modify natural frequencies of the structure. The improved PEVAPSM method enables to precisely determine the moment of inertia and modal damping of gears in the driveline, preventing resonance with other structures at the same frequency. It offers valuable guidance for studying the torsional vibration characteristics of engineering vehicle drivelines.