Hybrid Active–Passive Vibration Isolation for Fast Steering Mirrors Using a Magnetic Quasi-Zero Stiffness Mechanism

In space optical communication systems, the fast steering mirror (FSM) serves as a core component for high-precision beam pointing and stabilization control. However, its tracking performance and disturbance rejection capability are constrained by the Bode “waterbed effect,” making it challenging for traditional active or passive methods to achieve a balance. This paper proposes a hybrid active–passive vibration isolation strategy by incorporating a magnetic quasi-zero stiffness (QZS) mechanism, which reduces the system stiffness from 12.3[Formula: see text]N ⋅ m/rad to 0.5[Formula: see text]N ⋅ m/rad, altering the plant dynamics to achieve near-zero dynamic stiffness while maintaining static stiffness for load support. The mechanism significantly lowers the natural frequency from 33.02[Formula: see text]Hz to 5.73[Formula: see text]Hz and eliminates the resonance peak. Under identical PID parameters, experimental results demonstrate a substantial improvement in low-frequency isolation performance, a slight increase in closed-loop bandwidth, enhanced closed-loop characteristics, and a reduction in maximum step disturbance response displacement from 1.13 to 0.10. The study validates the effectiveness of QZS in mitigating the “waterbed effect,” providing a novel pathway for FSM applications in high-disturbance environments.