Optimal Matching Analysis of Net Buoyancy and Pitching Angle for Underwater Gliders

Control parameter optimization is an efficient way to improve the endurance of underwater gliders(UGs),which influences their gliding efficiency and energy consumption.This paper analyzes the optimal matching between the net buoyancy and the pitching angle and proposes a segmented control strategy of Petrel-L.The optimization of this strategy is established based on the gliding range model of UG,which is solved based on the approximate model,and the variations of the optimal control parameters with the hotel load are obtained.The optimization results indicate that the segmented control strategy can significantly increase the gliding range when the optimal matching between the net buoyancy and the pitching angle is reached,and the increase rate is influenced by the hotel load.The gliding range of the underwater glider can be increased by 10.47%at a hotel load of 0.5 W.The optimal matching analysis adopted in this study can be applied to other UGs to realize endurance improvement.

Design,Hydrodynamic Analysis,and Testing of a Bio-inspired Movable Bow Mechanism for the Hybrid-driven Underwater Glider

Hybrid-driven Underwater Glider(HUG)is a new type of underwater vehicle which integrates the functions of an Autonomous Underwater Glider(AUG)and an Autonomous Unmanned Vehicle(AUV).Although HUG has the characteristics of long endurance distance,its maneuverability still has room to be improved.This work introduces a new movement form of the neck of the underwater creature into HUG and proposes a parallel mechanism to adjust the attitude angle and displacement of the HUG’s bow,which can improve the steering maneuverability.Firstly,the influence of bow movement and rotation on the hydrodynamic force and flow field of the whole machine is analyzed by using the Computational Fluid Dynamics(CFD)method.The degree of freedom,attitude control range and movement amount of the Movable Bow Mechanism(MBM)are obtained,and then the design of MBM is completed based on these constraints.Secondly,the kinematic and dynamic models of MBM are established based on the closed vector method and the Lagrange equation,respectively,which are fully verified by comparing the results of simulation in Matlab and Adams software,then a Radial Basis Function(RBF)neural network adaptive sliding mode controller is designed to improve the dynamic response effect of the output parameters of MBM.Finally,a prototype of MBM is manufactured and assembled.The kinematic,dynamics model and controller are verified by experiments,which provides a basis for applying MBM in HUGs.

Dynamic Model and Motion Characteristics of an Underwater Glider with Manta-inspired Wings

An underwater glider with bionic wings controlled by two operating modes is proposed to perform a variety of marine exploration tasks.The system composition of the vehicle and the structural design of wings inspired by manta ray are presented.The bionic wings can keep outstretched or realize oscillating motions according to the operating modes of the vehicle.A universal dynamic model of the vehicle was derived from multibody theory.Gliding,sailing and steering motions were simulated based on the dynamic model to illustrate the dynamic behaviors of the vehicle under different types of propulsion techniques.The results obtained through simulated calculation are basically consistent with the experimental data,which indicate that the developed dynamic model is applicable to describe the motion characteristics of the vehicle.Experiments were conducted in coastal area to analyze the propulsive characteristics of the bionic wings and sea trials involving multifarious motions were carried out,the applicability of the vehicle in marine environment was verified.

A Bionic Flexible-bodied Underwater Glider with Neutral Buoyancy

The buoyancy of traditional Underwater Glider(UG)with a rigid hull is aff ected by the changing marine parameters,making it difficult for the vehicle to dive deeper with good motion characteristics.In the present work,the development of a novel UG for neutral buoyancy,which is equipped with a Flexible-Liquid-Rigid(FLR)composite hull,is presented.The innovative hull that imitates the buoyancy regulation mechanism of marine organisms is easily adaptable to the changing marine environment.The rigid part of the composite hull withstands hydrostatic pressure for inner function modules of the vehicle.The liquid of the composite hull mainly serves as a buoyancy compensation to mitigate the eff ect of buoyancy variation caused by the changing marine parameters.The flexible covering provides a good hydrodynamic shape for the vehicle under the internal liquid pressure.The buoyancy variation due to the composite hull compression as well as changes of seawater density and temperature was comprehensively considered in the design process and integrated to the dynamic model.In addition,sea trials were performed to verify the motion characteristics of the proposed vehicle.The results reveal that the Flexible-bodied Underwater Glider(FUG)has a better gliding performance in practice.