ABSTRACT

This paper addresses the problem of three-dimensional (3-D) way-point tracking for a biomimetic underwater vehicle (BUV) propelled by undulatory fins: RobCutt-II. Based on the specific mechanical design and control system configuration, the RobCutt-II can perform diversified locomotion patterns, especially submerging or surfacing vertically in the water. In order to deal with the challenging problem of motion control of the BUV in underwater operation, a switching control for 3-D way-point tracking is proposed. Moreover, we design an experiment simulating the actual underwater operation process. The RobCutt-II first dives to the desired depth vertically, then swims successively to the way-points along the horizontal plane, and finally keeps depth at the last way-point. Simulation and experimental results demonstrate the feasibility and effectiveness of the proposed switching control.

INTRODUCTION

Natural selection and evolution make biological systems diversify into nearly every possible habitat and preserve remarkable adaptations for locomotion. Mimicking the unique undulatory propulsion mode of cuttlefish, biomimetic underwater vehicles (BUVs) propelled by undulatory fins have many advantages such as higher maneuverability, stronger disturbance rejection, and quieter actuation than conventional underwater vehicles equipped with jets or axial propellers (Neveln, Bai, Snyder, Solberg, Curet, Lynch and MacIver, 2013). Hence these BUVs are expected to be widely used in marine and military fields (Blidberg, 2001).

As growing research on the wave-like propulsion mechanism and hydrodynamics analysis demonstrate a variety of prospective utilities in undersea vehicles, researchers and engineers have developed many kinds of biomimetic robotic prototypes with fin propulsion. Curet et al. designed a robotic knifefish with an undulatory propulsor using 32 servo motors to drive the long-fin (Curet, Patankar, Lauder and MacIver, 2011). Hu et al. developed a robotic undulating model and proposed a control scheme that enabled it to mimic fin-ray undulation kinematics of live fish (Hu, Low, Shen and Xu, 2014). Rahman et al. designed a squid-like underwater robot with two undulating side fins simulating stingrays or cuttlefishes (Rahman, Sugimori, Miki, Yamamoto, Sanada and Toda, 2013). However, although many types of BUVs have been developed, few BUVs have been put into practical applications as far as we know. There are several possible reasons for this fact. In addition to the complex hydrodynamics and the model uncertainty in underwater environment, researchers seldom consider the closed-loop motion control such as way-point tracking for these BUVs, which are of primary importance for most applications.

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