New magnetorheological engine mount with controllable stiffness characteristics towards improved driving stability and ride comfort

Engine mount is an important subassembly installed between the chassis and the engine. Its importance is mainly reflected by its capability of protecting the car body from the engine-induced vibrations. The current semi-active engine mount works to mitigate the vibration by changing its damping, while the property of variable stiffness can further suppress the vibrations by reducing the vibration transmissibility. Therefore, this paper developed a new magnetorheological engine mount which can change its stiffness to shift the natural frequency of the mounting system away from the excitation frequency so that resonance can be avoided when the engine is starting. The stiffness controllability also meets the stiffness design conflict between vibration isolation requirement and engine stability requirement when the cars drive on rough roads. The characterization test has verified its field-dependent properties that the effective stiffness has increased by 80.65% and the equivalent damping coefficient has increased by 26.85% as the applied current increases from 0 A to 1.5 A. Then a vibration isolation test was performed to evaluate the mounting system’s vibration reduction performance using a commercial internal combustion engine. The test results verified that the new magnetorheological engine mount under the semi-active control algorithm named Short Time Fourier Transformation is much better at suppressing the engine-induced vibrations than under passive control. And finally, a stability test was conducted and it verified that the new magnetorheological engine mount under Short Time Fourier Transformation control algorithm (semi-active control) performed better stability than the passive control. These experimental results indicate that this new magnetorheological engine mount is highly effective in isolating the engine-induced vibrations and keeping the driving stability.