A novel anti-hydropressure piezoelectric jetting micro thruster for steering AUV

Abstract

Achieving agile steering motion without auxiliary forward velocity is difficult for autonomous underwater vehicle (AUV) driven by rudders. Although installing vectored thrusters and more propellers can adjust AUV's posture in situ, the system complexity, cost and volume are multiplied due to the assembled sealing and anti-pressure devices. It is inaccessible to operate in deep-sea unstructured regions. Hence, a novel micro 3.2 cm-diameter piezoelectric jet thruster suitable for high-pressure environment is proposed, which realizes dual-drive system integration without increment in volume and structure complexity after a simple gluing insulation. The high-frequency micron-level deformation of piezoelectric vibrator directly acts on the cavity to form a m/s-level jet with no transmission structure. To achieve high-efficient propulsion of the thruster, the vibration characteristic of vibrator, the flow field and pressure variation and the driving enhancement mechanism are numerically investigated. Then, the exciting waveform parameters, the cavity and nozzle shapes are optimized, and the corresponding fluid flowing state behind is analyzed. The findings indicate that the opposite positions of maximum suction and ejection velocities, and their final values synergistically dominate driving force improving. And the largest average driving force occurs in the thruster with contractive hyperbolic-shaped cavity and nozzle. Reducing the suction velocity and time by changing the duty ratio and falling edge of the square wave is incapable of enhancing the driving performance. In addition, the consistent motion velocity without attenuation below 20 MPa water pressure proves the propulsion feasibility in deep sea. The AUV with body length (BL) of 32 cm can achieve agile steering motion directly driven by the integrated thruster without influencing the original streamlined structure, and the needed steering radius is only 0.42 times as long as its length. This work presents an effective solution for maneuvering deep-sea underwater vehicle in the narrow regions such as the seabed slit and gully.