Research On Buoyancy Adjustment Technology Based On Weight Adjustment

With the acceleration of human exploitation of the ocean,the research of various types of underwater robots is booming.Buoyancy control system can lead or assist the underwater robot to hover at fixed depth,lift and adjust its attitude,etc.It is a key research technology in the field of underwater robots.In this paper,two buoyancy control modes of weight adjustment and volume adjustment are analyzed,focusing on the research of buoyancy control technology based on weight adjustment,aiming at accurately controlling the gravity and buoyancy of buoyancy control system.The main research contents are as follows:(1)The factors that affect the precise control of gravity and buoyancy in two buoyancy control modes of weight adjustment and volume adjustment are analyzed,and design the adjustment mode.Aiming at the problem that the deformation of the outer oil pocket can’t accurately determine the control accuracy in the oil pocket volume adjustment mode,a screw-piston volume adjustment mode is designed.Aiming at the weight adjustment mode of hydraulic pump-ballast water tank,the influence of each component unit in the system on the control accuracy is analyzed,and the system combination mode under different working conditions is designed.Through comparative analysis,the final adjustment mode is determined.The deformation suppression method in cabin design is studied.The cylindrical cabin is designed by critical instability pressure,and the square cabin is designed by maximum deflection analysis.(2)The overall scheme of buoyancy control system using hydraulic pump-ballast water tank regulation mode is studied.Building the hydraulic circuit of the system,calculate and select each component,study the electric control reversing method of manual reversing three-way ball valve,design the main controller and circuit of each module,design two control strategies according to the working characteristics of seawater pump and driver control characteristics,and determine the final working form through comparative analysis.(3)The control technology of buoyancy control system is studied.The overall mathematical model of the system is established,and PID controller and fuzzy PID controller are designed to solve the problems of slow response speed and weak anti-interference ability of the system.The response speed and anti-interference ability of the system under the two controllers are compared and analyzed by using MATLAB to determine the final controller.(4)The experiments on the developed system prototype are finished to verify the relevant technical indexes.According to the underwater experimental environment,the pressure-resistant cabin for the experiment is designed.Carrying out cabin tightness test,angle error test of ball valve electric control reversing,pressure sensor calibration test,flow characteristic test and onshore and underwater quantitative filling and discharging test.Through various experiments,the feasibility of the buoyancy control technology studied is verified,and a useful reference is provided for its improvement and application in the environment of large depth and large adjustment.