The Research Of Buoyancy Regulation And Jettison System In Autonomous Underwater Vehicle

Along with the rapid development of marine industry and technology in the world,underwater vehicle has become an important tool for ocean resources survey and exploration.Autonomous Underwater Vehicle(AUV)has attracted an increasing number of researchers' attention,due to its wide operating range,strong mobility and flexibility,and high intelligence.Since the energy carried in AUV is finite in the process of operation,energy-saving technology for AUV has attracted much attention.Meanwhile,safety and reliability have become an important index for AUV in the complex and unknown ocean environment.Therefore,it is significant and applicable to study the heave control based on the buoyancy regulating system and self-rescue(BRSS)technology.The main research contents include:(1)This paper reviewed and analyzed the current situation of the buoyancy regulation and self-rescue technology of underwater vehicle in the world.And the features of the buoyancy regulation and self-rescue devices were presented Then,it reviewed the current situation of the liquid level control,and the paper analyzed the low regulation precision caused by high external-pressure in the complex ocean environment.Finally,the paper presented the overall scheme of the buoyancy regulation system based on booster bump with the ocean-water medium and self-rescue system based on load-rejection.And the prototype was designed.(2)In order to meet the application requirement in the deep ocean environment,the paper completed the selection and development of BRSS.Since the priorly developed pressure balance valve life was short,and the spring was susceptible to ocean-water,a novel pressure balanced valve is been designed.With respect to the unsatisfactory performance caused by the difference the desired rupture-pressure and the real rupture-pressure,a new trigger approach for passive load-rejectionwas studied in the paper.For the inadequate pressure in the inlet port of the gear pump with oil pressure,it developed the oil accumulator in order to improve the hydraulic gear pump inlet port purposes.For fluctuations of liquid surface in the pressureproof cabin pressure,the paper studied an improved structure of float ball.An appropriate treatment program was designed to solve corrosion problem of iron pan of load-rejection system.Due to the integration feature of AUV,the paper considered the assembly program of the load-rejection system to achieve the convenience of assembly.(3)Sincethe hydraulic power source is not suitable to be used in the deep-sea environment,the paper made improvements in the pressure-resistance design of the low-pressure loop in the booster pump and the dynamic-seal design in gear pump.And the experiments were performed to illustrate their efficiency.The paper calculated the output power of the hydraulic power unit to test whether it met the requirement.In order to improve the efficiency,a novel booster pump was designed so that the flow can be provided in the low-pressure loop and high-pressure loop in the booster pump,respectively.As for thepulsation problem that existedin the hydraulic system,a kind of passive method used to reduce hydraulic pulsationwas studied.Besides,the paper proposed a vibration-attenuation scheme by integrating harmonic damper with interferential damper.And simulations were carried out by using AMESim.As for the problem that the passive load-rejection devicedid not be released due to the inadequate depth if AUV reached the seabed,a load-rejection device with mechanical timer was designed,which can be also used to the case of signal interruption.Meanwhile,to improve the reliability of the passive load-rejection device itself,multistage dual trigger passive load-rejection technology was studied in the paper.(4)With respect to the influence to motor speed and volumetric efficiency of hydraulic power unit in different depth,the paper establishedthe mathematical model of the buoyancy regulation control system under different depth.As for the problem in the conventional proportional control,PID control and fuzzy sliding mode control were investigated.In order to illustrate the performance of PID and fuzzy sliding mode control,simulations of water quantity control are presented with no load,10 MPa and random 1MPa disturbance,respectively.Furthermore,the paper analyzed comparatively the simulation results from regulation speed,regulation precision and disturbance-rejection.(5)In order to verify the drainage performance of the booster pump,flow experiments with no load and 10 MPa load respectivelywere carried out and their results were analyzed comparatively.Since there existed some leakage when the pressure valve approached to the given designed position,the real depth to reject the load deviated from the desired.Furthermore,the depth error to reject the load was required to be less than 50 m when AUV was required to operate in the 50 m above the seabed.In accordance with the requirement,the paper accomplished the startup performance of valve.With respect to the requirement for the passive load-rejection device based on mechanical timer,the startup performance of the trigger valve was performed in the high-pressure environment.To test the liquid level control performance based on the buoyancy regulation control,water regulation experiments were conducted under the condition with 10 MPa pressure.Finally,To test the performance of the buoyancy regulation and self-rescue system installed in the AUV,the experiments are conducted in a pool with 10 m depth and real oceanenvironment,respectively.