Research On Reliability Of Buoyancy System Of Underwater Glider Based On Accelerated Life Testing

Underwater glider is a novel marine environment observation platform for unmanned underwater operation,which has the characteristics of low energy consumption,good maneuverability,strong observation and detection ability,long sailing mileage and low cost.It is mainly driven by its own buoyancy system.It often takes hundreds of days for the underwater glider to complete the given ocean observation and detection task.The underwater glider is required to have high reliability,to ensure the success of the task and the safe recovery of equipment.During operation,the underwater glider can adjust its own buoyancy with the buoyancy system by changing the drainage volume of the fuselage,so as to realize the ascending and descending of the underwater glider,and do zigzag gliding.The reliability of buoyancy system directly affects the completion of the task.This paper takes the buoyancy system of a Petrel-L long-range underwater glider developed by Tianjin University as the research object.The ordinary life test,with long testing time and large data error,is not suitable for the reliability test of buoyancy system.Therefore,based on the theory of accelerated life testing,this study designs and carries out reliability testing of the plunger pump motor and plunger pump,the key components of buoyancy system,and analyzes the system reliability by combining the fault tree model and fuzzy occurrence probability.The main contents and achievements of this paper are as follows.An accelerated life testing based on temperature is designed to test the reliability of the plunger pump motor of the buoyancy system,which verifies the reliability technical index of the motor within the specified time.Then,the mean time between failures of the motor is 29940 H by combining the thermal aging law of motor winding.To test the reliability of the plunger pump,the accelerated life testing is designed,which takes the accelerated stress as the pressure.The two stress accelerated life testing scheme under small samples is used to solve the acceleration factor.The life of the plunger pump with the target depth of 4500 m is transformed into that with the working depth of 1000 m by using the inverse power law model.Based on the accelerated life testing data,the maximum likelihood estimation method is used to obtain the estimated value of Weibull distribution parameters and reliability index of piston pump.The mean time between failures is 586 H;The fault tree of buoyancy system is established,and the failure mode and failure probability of each component are analyzed.The occurrence probability of component failure is defined by fuzzy set,and the average number of fault-free profiles of buoyancy system is 2594,and the importance of each component are obtained.Finally,the results of fault tree quantitative analysis are verified by Monte Carlo simulation.