| Umbilical is the key component of submarine production.Its fatigue fracture is occurred easily due to the harsh service condition,resulting in severe environmental pollution,property damage and casualties.It is significant to study the fatigue mechanism of umbilical to avoid such disaster by reasonable design of umbilical structure.Therefore,a subsea dynamic umbilical in-situ fatigue test machine is developed,with bending and stretching function,to simulate the load of umbilical under different working conditions.The control system is affected by external disturbances during the period of test machine operation,such as,(1)The internal layers slide with each other because of multilayer composite structure of umbilical,resulting in nonlinear bending stiffness and tensile stiffness.(2)The load of bending end is time-varing due to the vibration of the test umbilical during operation.(3)The stretching end and the bending end are coupled to each other,etc.The control accuracy is deduced greatly by the influence of these above factors.Considering these problems,the control system of the umbilical fatigue test machine is analyzed and designed in detail.Based on the current research of the test machine,the overall design plan and structure of the machine are designed detailedly in this paper.Then,the static and modal analysis is performed to verify the reliability of the structure.To solve the existing problems of multi-cylinder hydraulic synchronous system,the system scheme of bending end is designed.The open-loop transfunction of the system is determined by analyzing the characteristics of the main hydraulic components in the system.In order to study the stability of the system without controller,the open-loop bode diagram and step response characteristics of the system under different load stiffness are analyzed.There exists a large synchronization error between the two hydraulic cylinders,due to the nonlinear,time-varying and random interference of the hydraulic system.To improve the antiinterference ability of the system and the accuracy of synchronous motion,the control algorithm of the synchronous control system is studied.By comparing with pso-pid control algorithm and general sliding mode control algorithm,an adaptive fuzzy sliding mode control algorithm based on PSO optimization algorithm is proposed.Simulation of dynamic characteristic of system is operated in Simulink,to analyze the response characteristic and verify the superiority of the proposed algorithm.Finally,based on the developed umbilical fatigue test machine,the input signal of the system is determined by studying the relationship between the swing angle of the swing head and the displacement of hydraulic cylinder.Then,verify the feasibility of the designed synchronization system and control strategy through the analysis of the test result. |
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