Design of Active Controller for Low-Frequency Vibration Isolation Considering Noise Levels of Bandwidth-Extended Absolute Velocity Sensors

The low-frequency performance of active vibration isolation system depends on the low-frequency measurement ability of inertial sensor such as geophone. Bandwidth extension-based methods may serve as a cost-effective solution to increase the low-frequency measurement accuracy of geophone, but suffered the deteriorations of the noise. Traditionally, the available extension bandwidth of geophone is merely based on the measured noise level or sensor dynamic, which may result in a degraded vibration isolation performance due to geophone's over- or undercompensation. In this paper, an integrated approach to hybrid controller design and compensation of geophone dynamic is developed by weighing the influences of sensor dynamic and noise on vibration isolation performance, and sets low-frequency design rules to moderately utilize the noisy responses of sensor. In feedback controller design, the aimed frequency is selected by the stability condition, the signal-to-noise ratio of sensor gives the design constraint to avoid the overuse bandwidth of geophone, while in feedforward control, the analyses are reversed, and consequently different aimed frequencies are achieved. The effectiveness of the designed controller was validated by experiments, indicating that the results were good consistencies with the analysis models, and the deteriorations by noise were avoided at low frequencies.