| More and more large structures are used in ship. When ships are sailing, they are affected by various periodic load such as wave and wind, which can easily lead structures to the fatigue failure. Fatigue failure affects ships' normal operation, it also threat life security of people and can cause great economic loss.To study the performance of these structures, fatigue test is necessary.For the load of those structures are complicate, the fatigue test system must be high precision and high response. The electro-hydraulic servo system provides the possibility to realize the loading system, for its characteristics is small volume, light weight, high precision and high response.This paper is a research project to develop a control system of fatigue testing platform for large structures. It is based on the characteristics of electro hydraulic servo force control system. The characteristic of this project is large load force and high precision. Design, development and debugging of testing platform is finished through optimization and simulation. Following is the main research work.First step of this project is determining the control mode of platform. According to the characteristics of project, we propose asymmetric valve control asymmetric cylinder as the force control mode, which needs less space and can afford large load, and analysis the dynamic characteristics of the fatigue testing platform by the establishment of mathematical model, which vertified the tationality of the control mode.According to requirement of different structures fatigue test, then we designed the overall structure, hydraulic oil source system and hydraulic loading control system according the stress characteristics of test structures, carry out the system dynamiv simulation and correction based on AMEsim,which lay the foundation for system debugging.At last it is the design of the console which can be divided to hardware part and software part. The design of hardware is selecting the industrial control computer and data acquisition card and designing the filter circuit. The software job is design the platform control programme. The platform realizes high precision control by the control method of intrgral separation PID.The fatigue testing platform which was developed in this project can achieve high load, high frequency fatigue test. The loading mechanism of platform is independent and flexible. The combination mode of loading mechanism can be changed easily to meet the requirement of different structures fatigue test.At present the fatigues testing platform has been put into practical and its cumulative loading times is more than ten million times. The platform runs smoothly and achieved good results. |
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