An optimal control method of internal resonances for vibration isolation system using an aperiodic isolator

Periodic isolator is well known for its wave filtering characteristic. While in middle and high frequencies, the internal resonances of the periodic isolator are evident especially when damping is small. This study proposes a novel aperiodic vibration isolation for improving the internal resonances control of the periodic isolator. The mechanism of the internal resonances control by the aperiodic isolator is firstly explained. For comparing the internal resonances suppression effect of the aperiodic isolator with the periodic isolator, a dynamic model combing the rigid machine, the isolator, and the flexible plate is derived through multi subsystem modeling method and transfer matrix method, whose accuracy is verified through the finite element method. The influences of the aperiodicity and damping of the isolator on the vibration isolation performance and internal resonances suppression effect are investigated by numerical analysis. The numerical results demonstrate that vibration attenuation performances of the periodic isolator and aperiodic isolator are greatly over than that of the continuous isolator in middle and high frequencies. The aperiodic isolator opens the stop bandgaps comparing with the periodic isolator where the pass bandgaps are periodically existed. The damping of the isolator has the stop bandgap widening effect on both the periodic isolator and the aperiodic isolator. In addition, a parameter optimization algorithm of the aperiodic isolator is presented for improving the internal resonances control effect. It is shown that the vibration peaks within the target frequency band of the aperiodic isolator are effectively reduced after the optimization. Finally, the experiments of the three different vibration isolation systems are conducted for verifying the analysis work. (Figure presented.)