Research On The Hydraulic System And Energy Consumption Of The 4000-meter Argo Profiling Floats

The broad-scale global array of temperature/salinity profiling floats,also known as Argo,is an ocean observation project launched by atmospheric and oceanography scientists in 1998(Freeland and Cummins,2005),aiming at long-term and accurate acquisition of hydrological data in the upper layer of the global ocean(Riser et al.,2016).The main task of Argo profiling float is to carry out the up-and-down motion in the deep ocean profile,during which carried sensors could perform sampling task.The real-time data sampled is of far-reaching significance to the study of marine science.While the hydraulic technology is the key to realize the heaving motion,a reliable and efficient hydraulic system is the guarantee for the successful completion of the monitoring task of the Argo profiling floats.At present,the hydraulic system of the 2000-meter profiling float is mainly composed of a reciprocating single-stroke plunger pump and a variable volume oil bladder placed outside the float This kind of hydraulic system is mainly applicable to the working range of 0-2000m.When it is applied to deeper sea,it would face a series of challenges.First of all,in order to increase the net buoyancy,the size of the piston cylinder needs to be increased accordingly,which is not conducive to the utilization of the internal space of the float.Secondly,with larger load pressure,the strength and mass of the piston cylinder will inevitably increase,which seriously affects the net buoyancy and carrying capacity of Argo,limiting the number of carrying sensors.In addition,when the float submerges to deep sea,considering that the working pressure of the hydraulic system will increase linearly,the requirements of hydraulic components are also much more stringent Therefore,a set of efficient and stable hydraulic system is critical for the 4000-meter deep-sea profiling floats,which is the basis for the realization of detection and sampling.The research object of the paper is the 4000-meter Argo intelligent profiling float independently developed by Shandong University.In view of the difficulties in the development of the deep-sea profiling float this paper focuses on the design and energy-saving optimization of the hydraulic system of the 4000 meter Argo profiling float.Considering problems of the extant hydraulic system performed in the experiment and sea trial,a set of low-power hydraulic system which is suitable for the deep-sea 4000-meter profiling floats is proposed,and then simulation analysis and comparison of the two hydraulic systems are taken to verify the feasibility of the proposed system.The multi-objective particle swarm optimization is used to optimize the parameters of the hydraulic system,so as to improve the volumetric efficiency and decrease the working time of the system.On the basis of this,a set of piecewise oil-pumping control strategies based on closed-loop control is proposed to improve the stability and energy-saving of the float.The feasibility and stability of the hydraulic system were verified with a high-pressure test rig,and the sea trial was carried out.The main contents and contributions are summarized as follows:1.Based on the extant deep-sea hydraulic system of profiling floats,a set of low-power hydraulic system which is suitable for the deep-sea 4000-meter profiling floats is designed.The feasibility of the system is verified with AMESim and MATLAB joint simulation,and a high-pressure test system is constructed to verify the correctness of the designed model,which provides a theoretical and engineering basis for the design of the hydraulic system of the deep-sea profiling floats.2.Based on hydrodynamics modeling and AMESim simulation,multi-objective particle swarm optimization algorithm is applied to optimize the model parameters of pressuriser,which is the core component of the proposed hydraulic system.The optimal solution set of the three objective functions of volume efficiency,working time of outputting unit volume hydraulic oil and mass is obtained,which provides basis for the design and optimization of pressuriser model in practical application in the future.3.The control strategies of the piecewise oil-pumping based on closed-loop control are proposed during the ascending stages of the float.The simulation model and the dynamic and energy consumption models of the float in the stage are established,and the simulation results of the traditional control strategy and the designed control strategies are compared and analyzed.The optimized strategies improved the operational stability and energy consumption of the float,and provide a reference for the further study of the oil-pumping strategy of the deep-sea profiling floats.