An adaptive tunable vibration absorber using a new magnetorheological elastomer for vehicular powertrain transient vibration reduction

During the transient stage of acceleration, the powertrain experiences a period of high level vibration because the engine speed passes through one or several powertrain natural frequencies. This paper presents a concept design of an adaptive tuned vibration absorber (ATVA) using a new magnetorheological elastomer (MRE) for powertrain transient vibration reduction. The MRE material used to develop the ATVA is a new one, which is synthesized from a highly elastic polymer and carbonyl iron particles of 3-5 and 40-50 mu m. Under a magnetic field of 0.3 T, the MRE material has a giant increase, which is more than two orders, in both the storage and loss moduli. To facilitate the ATVA design, effective formulae for the storage modulus and loss factor were derived as explicit functions of the applied magnetic field density. With the derived formulae, ATVA parameters such as the stiffness and damping coefficients were converted effectively from the magnetic field density. Thus, the ATVA frequency can be tuned properly according to the excitation frequency. Numerical simulations of a powertrain system fitted with the ATVA were conducted to examine the ATVA proposed design. By using the MRE-based ATVA, the powertrain natural frequencies can be actively tuned far away from the resonant area of excitation frequency. Also, the time histories of powertrain frequencies depending on the magnetic field density before and after installing the ATVA have been compared to show that the resonant phenomena have been dealt with completely. As a result, the powertrain transient vibration response is significantly suppressed. In addition, the effect of the ATVA's moment of inertia, stiffness and damping on the ATVA's effectiveness during the transient stage was investigated to choose the ATVA's optimal parameters. The MRE-based ATVA will be a novel device for powertrain vibration control not only for the steady stage but also for transient vibration.