Analysis Of Working Performance And Adaptability Of Deep Sea Pump

The ocean contains precious and abundant resources such as minerals and biology,which have good mining and utilization value.With the development of underwater equipment technology,ocean exploration has gradually moved from shallow sea to deep sea.The deep sea has the characteristics of high pressure and low temperature,which will affect the normal use of underwater operating equipment.Hydraulic transmission technology has the advantages of strong bearing capacity,high power density,easy to achieve stepless speed regulation,etc,so it is widely used in deep sea equipment.The hydraulic pump is the core power component of the hydraulic unit and has a large impact on the overall performance of the hydraulic system.This paper took the deep-sea piston pump as the research object,analyzed the effects of the change of oil viscosity and stiffness on the working characteristics of the piston pump under different water depths,and obtained the variation of dynamic and static performance of the piston pump with water depth.By using the Model Reference Adaptive Control(MRAC)strategy,optimized the dynamic performance of the deep sea pump,and obtained the underwater ideal performance.The specific research content is as follows.Fistly,established deep-sea environment models with water depth as an independent variable,such as environmental pressure-water depth,seawater temperature-water depth,and obtained the variation law of two environmental parameters with water depth.Constructed dynamic viscosity and variable stiffness model of oil under variable temperature and variable pressure with temperature and pressure as independent variables,and combined with the deep sea environment model,the dynamic model of oil viscosity-water depth and stiffness-water depth was further obtained.Analyzed the characteristics of the oil medium with ISO VG 32 hydraulic oil,obtained a two-stage variation law of viscosity increasing rapidly and steadily with the increase of water depth,and a three-stage variation law of stiffness increasing rapidly,slowly and gradually with the increase of water depth.When a single environmental parameter was applied,further analyzed the variation law of dynamic viscosity and variable stiffness of oil.It can be seen that the effects of environmental pressure and seawater temperature on the characteristics of oil medium under different water depths were different.Specifically,in shallow water depth,seawater temperature played a leading role in oil viscosity and stiffness,while environmental pressure had less influence,however,under the deep water depth,the influence of seawater temperature was weakening,and environmental pressure became the main influencing factor.The research results laid the foundation for the analysis of the dynamic and static characteristics of the piston pump.Then,established the pressure and flow control models of the deep-sea piston pump respectively,analyzed the two models theoretically,and further analyzed the influence of variable viscosity and stiffness of oil on dynamic and static performance of system under different water depths by MATLAB simulation function,and finally verified the validity of theoretical analysis results and simulation results by experiments.Achieved the following conclusions:when the viscosity changed alone,as the water depth increased,the rapid response of system gradually decreased,and the stability of system gradually increased;when the stiffness changed alone,the change in system performance under the effect of stiffness alone is opposite to the result of viscosity single action;When the viscosity and stiffness of the oil changed simultaneously,the change of rapid response a nd stability of the system with the increase of water depth was the same as the viscosity single action,but the extent of the change was different.By further compared the effect of oil viscosity and stiffness on the dynamic and static performance of the system under different water depths,the system within 0-1000 m could be regarded as a variable stiffness-dynamic viscosity system,and the system within 1000m-7000 m was considered as a fixed stiffness-variable viscosity system.Finally,based on Lyapunov stability theory,applied MRAC strategy to optimize the dynamic performance of deep-sea pump control system.Designed the Lyapunov-MRAC controller and calculate the corresponding control law.Taken the control model of the deep-sea pump under sea level as a reference model,and taken the pressure control model under different water depths as the actual controlled model.Then simulated different input signals for the designed control system.The results showed that the system control error decreased with time,that was,the accuracy of the control system increased gradually.The controlled model had good ability to follow changes in the reference model.Compared with the uncontrolled model,it could be seen that the system under Lyapunov-MRAC control had better dynamic response performance.Analyzed the influence of controller parameters on the performance of the control system.It showed that increasing the amplitude of the input signal,the initial control accuracy of the system was reduced,but the stability speed of the system was accelerated.Increasing the gain of the control system could simultaneously improve the initial control accuracy and stable speed of the system.This paper analyzed the variation law of oil medium characteristics under different water depths,and researched its influence on the stability and rapid response of the piston pump,and optimized the dynamic performance of piston pump based on Lyapunov-MRAC strategy.It provided a theoretical basis for the selection of medium for deep-sea hydraulic equipment,and also provided ideas for the development of deep-sea hydraulic pumps.