Compared with high speed dolphin and tuna, the current biorobotics unmanned undersea vehicle still has a long way to go. Yet compared with conventional single-screw propeller AUV, SPC-III has made great progress. With small displacement tonnage, it realizes one-component vector converter and increases low speed maneuverability of AUV remarkably. In addition, the power of caudal fin thruster is also satisfactory. It can be said that using actuating motors to drive two joints caudal fin thruster is a feasible option with the current engineering technology. Of course, there also exist some congenital deficiencies. For example, actuating motors works in oscillation condition and its peak power is 40% higher than that at even pace at similar power output, therefore actuating motor and amplifier possess higher power redundancy. This means power density of the propeller is also reduced. This is the exact reason why Vehicle velocity of SPC-III is hard to increase. Working in oscillation condition also prevents the actuating motors and reducer from work continuously at optimum efficiency points. It is foreseeable that both electro-mechanical conversion efficiency and transmission efficiency of caudal fin thruster are lower than screw propeller which is in a uniform rotation. In respect of noise, since reducer is adopted, there are no strong points in terms of radiated noise. Yet flapping frequency of caudal fin is far lower than working frequency of the propeller at the same vehicle speed, which means hydrodynamics noise may be low . Future work can be carried out to obtain experiment data on noise through comparison experiment.
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