A six-degree-of-freedom active micro-vibration isolation system for suppressing multi-directional random micro-vibrations

Current research on active vibration isolation systems is primarily focused on single-degree-of-freedom sinusoidal sweep excitations provided by shakers, or limited to unidirectional micro-vibrations induced by environmental disturbances. However, studies addressing multi-directional random micro-vibrations induced by ambient excitations remain insufficient. This paper presents a six-degree-of-freedom (6-DOF) active micro-vibration isolation (AMVI) system for attenuating multi-directional random micro-vibrations. The isolation system is designed with an equilateral triangular layout of three support units, utilizing planar voice coil motors and high-sensitivity, high signal-to-noise ratio (SNR) accelerometers for actuation and error sensing. A 6-DOF dynamic model is established using the Newton-Euler method, followed by configurational decoupling based on the structural layout of the system and line vector theory. A hybrid control strategy, integrating PI feedback with model-inverse feedforward control, is implemented. Simulation results demonstrate that the feedback controller effectively suppresses and shifts the resonance peaks to lower frequencies, while the feedforward controller reduces the overall transmissibility of the low-frequency band. Finally, an experimental rig is established to verify that the proposed AMVI system can effectively suppress multi-directional random micro-vibrations, with the experimental results demonstrating high consistency with the simulations. Specifically, the peak transmissibilities in the x , y , and z directions are reduced by 42.6 dB, 32.7 dB, and 39.1 dB, respectively. This research provides valuable insights into the development of AMVI systems for suppressing complex ambient micro-vibrations.