Study On In-situ Shear Force Measurement And Penetration System For Seabed Sediments

Deep sea scientific research and resource and energy development engineering activities and marine security defense engineering have entered the age of full ocean depth,and there is an urgent need to accurately learn the mechanical properties of deep sea sediments.At present,there is no device that can accurately test the penetration resistance,pore water pressure and shear strength of deep seabed sediments in full ocean depth.The key technical difficulties in the accurate measurement of the mechanical properties of deep sediments in the whole sea are:how to accurately sense small pressure increments under high pressure background,how to reduce the disturbance of weak sediments caused by the test device landing,how to ensure the stability of the test device landing to realize the large-stroke penetration of the probe rod and the sampling tube,how to use the test data to correctly evaluate the mechanical properties of the sediment,and how to achieve the full ocean depth test on the scientific research ship that does not have a winch of more than 10,000 meters.In this paper,the seabed sediment shear strength measuring device is taken as the research object,and a full ocean depth cross plate shear module that can be integrated into the full ocean depth lander is developed.This paper includes six chapters.The first chapter is an introduction,which mainly elaborates the research background and significance of this subject and introduces the research status of deep sea sediment mechanical properties at home and abroad.Meanwhile,it also points out the current scientific problems and technical difficulties in the research.Finally,it introduces the main research content of this article.The second chapter is the structural design of the cross plate shear module.After satisfying the requirement of large stroke penetration depth,the module is subjected to finite element analysis during the penetration process and the shearing process,to ensure that the entire module can work safely and reliably.The third chapter is to design and study the torque sensor of this module.It introduces the classification of torque measurement methods,and determine the method to measure torque.Theoretical analysis of the resistance strain effect and the stress of the induction shaft is introduced.At the same time,the relationship between strain gauge resistance and pressure change is obtained through the pressure test of strain gauge,which provides a theoretical basis for eliminating the influence of high-pressure environment on torque measurement.Finally,the torque sensor structure design,further determine the torque sensor internal power plant and reducer model.The fourth chapter is to study the hydraulic unit of the deep-sea penetration device and design the hydraulic unit that meets the work requirements.The viscosity-temperature characteristic,viscosity-pressure characteristic and elastic modulus of the selected hydraulic oil in deep sea environment are studied.At the same time,the valve box installed in the deep sea lander is designed,in which the pressure compensation device installed above the valve box is studied.The fifth chapter is to study the hydraulic control system.Firstly,it introduces the hydraulic control technology and classification.Secondly,the designed servo direct drive hydraulic control system is introduced,and the selected hydraulic control system is modeled mathematically.Finally,the real data is brought into the mathematical model,and the Bode diagram of the hydraulic control system is obtained through Simulink simulation analysis.The results show that by using the logarithmic stability criterion,the system has good stability.The sixth chapter is the co-simulation of the pump-controlled cylinder dynamic mechanism based on AMESim/Simulink.Firstly,the basic contents of the software and the setting of co-simulation are introduced.Then,the hydraulic system designed in the fourth chapter is modeled,analyzed and studied in AMESim.Finally,the performance of the traditional PID and fuzzy PID controllers in the deep-sea environment is analyzed through simulation.The results show that the fuzzy PID controller has faster response and anti-interference ability than the traditional PID controller.Finally,it summarizes the full text and proposes the future.The cross plate shear module is studied in this paper.Simulation results show that the module can operate safely and stably in deep sea.The hydraulic oil,pressure compensation device and hydraulic control part involved in this module are studied.It provides the research foundation for the similar subsea sediment mechanical property measurement device.