Active vibration isolation for TBM guidance system: Modeling, decoupling and experimental validation

To enhance the measurement accuracy of Tunnel Boring Machine (TBM) guidance systems under strong vibration environments, this study designed a novel multi-degree-of-freedom (MDOF) active vibration isolation system. The system employs a composite structure of metal coil springs and eight large-air-gap voice coil actuators. This design effectively addresses the insufficient suppression of MDOF, large-amplitude (2 mm), low-frequency (5 Hz) strong vibrations by existing passive isolation systems and active micro-vibration isolation systems. Using modal analysis, the strong coupling effects between multiple channels were eliminated (coupling bandwidth reduced from >5.81 Hz to 0 Hz). Based on this decoupling, an Extended State Observer (ESO) and a high-frequency robust control algorithm were designed, significantly improving the system’s ability to suppress low-frequency disturbances. Tests show that under sweep excitation in the X/Y/Z directions, the system reduced the RMS measurement errors of pitch angle and roll angle by 78% and 74.8% respectively, and reduced the RMS linear vibrations in the X/Y/Z directions by 89.37%, 80.24%, and 94.92% respectively. The novel MDOF active vibration isolation system designed in this study provides a foundation for stable and high-precision operation of TBM guidance systems in complex geological vibration environments.