Development and active noise control of a piezo-actuated attenuator for underwater vehicle pipelines

Abstract In underwater applications, the mechanical noise has become one of the key limiting factors affecting the acoustic stealth performance of underwater vehicles. Among them, the main power unit noise and propeller noise have been effectively controlled. However, the hydraulic pipeline system noise still needs to be solved. In this paper, a piezoelectric actuated attenuator for underwater pipeline pulsation suppression is developed. The attenuator changes the local liquid volume in the secondary channel through the output displacement of the piezoelectric stack, causing regular changes in the pressure in the area, thereby generating secondary pressure pulsations to offset the pressure pulsations in the main path. The system identification is conducted based on a customized fabricated prototype and the built experimental set. Then an active noise control (ANC) technology based on the developed attenuator using enhanced variable step-size filtered-x least mean square (VSS-FxLMS) algorithm is proposed to suppress low frequency vibration and underwater noise in the pipelines. The ANC is tested and compared with existing algorithms to show the effectiveness. Results show that the proposed VSS-FxLMS can suppress the initial pulsation fluctuations fast by converging within 1 second and maintaining a low residual error in the steady state stage. In terms of quantitative comparison of the noise attenuation, PID and phase shift controllers achieved attenuation effects of –7.62 dB and –8.04 dB respectively, while the FxLMS algorithm improved to –10.34 dB. As for the proposed VSS-FxLMS, it shows better control effects in each stage, and finally achieves a noise attenuation of –11.83 dB. The developed piezo-actuated attenuator as well as its ANC algorithm can provide a new structure and control scheme for noise attenuation of underwater vehicle pipeline systems.