Research About Modular Buoyancy Adjusting Technology Of Autonomous Underwater Vehicles

More and more attention is being paid to marine resources.As an important means of detecting marine environments and resources,AUVs are becoming more and more important for every country.The buoyancy of AUV would be influenced by the effects of seawater temperature,salinity and depth.There are less domestic studies of AUVs with buoyancy adjusting system.Three kinds of modular high precision buoyancy adjusting devices were developed in this thesis.One prototype of the most optimal solutions was developed and thedevice can be widely used in small and medium-sized unmanned underwater equipment.It is able to achieve buoyancy ratio,posture adjustment and buoyancy driven,etc.This technology will achieve good reliability,is easy to design,structurally of small size,easy to modulate and has high precision of control.These advantages have important research significance and practical value on reducing consumption of energy and system cost,improving the maneuverability of AUV,safety and quality of underwater operation.The main research contents include:1.According to the subject,the selected topic backgrounds and basis were studied indetail.The research of buoyancy regulating technology of AUV both in domestic and abroad was analyzed,and the emphases and difficulties in scheme design were generalized.Technical route was formulated according to the priority and special target requirement of Chinese Academy of Sciences.2.An oil capsule buoyancy regulating device is designed and analyzed in this thesis.The gas volume variation was measured in pressure tank in order to calculate the amount of the buoyancy regulation.The accuracy and sensitivity for measuring the gas volume variation is analyzed.The accuracy and sensitivity for measuring the gas volume variation is analyzed;A simulation experiment of this hydraulic system is performed within AMESim,and key components are selected and checked,selection,checking for key components to verify thefeasibility of the designed oil capsule buoyancy regulating device.3.A high-precision oil capsule buoyancy regulating device is designed and analyzed.A high-precision oil linear displacement sensor was installed on the outside of the oil capsule to measure the amount of oil variation,thus calculating the volume of buoyancy regulation in an indirect way;A simulation experiment of this hydraulic system is performed within AMESim and key components are selected and checked to verify the feasibility of the designed oil capsule buoyancy regulating device.4.A piston cylinder buoyancy regulating device is designed,which utilizes the hydraulic system to drive the fluid cylinder to absorb and discharge seawater,so as to achieve buoyancy adjustment.Linear displacement sensors are adopted to measure the amount of oil variation,thus calculating the volume of buoyancy regulation in an indirect way.Then the hydraulic system is simulated by AMESim,designing,selecting and checking key components to verify the feasibility;the hardware and software of the control system were design and developed for Variable Buoyancy Device,an experimental prototype of the buoyancy regulating system design was developed.Its prominent features which are operating reliablely and have good sealing performance,high efficiency,low power consumption,high precision,and small volume.5.Ordinary type,high precision oil capsule type oil,and the hydraulic cylinder type buoyancy regulating systems were compared and analyzed,testing displacement,total quality,volume regulation,accuracy,and response speed.Piston cylinder type buoyancy adjusting technology was decided to be the principle prototype according to the priority and special target requirement of Chinese Academy of Sciences.The prototype piston cylinder type buoyancy adjusting device was developed successfully,which provides a foundation for subsequent buoyancy adjusting technology.