Research And Implementation Of The Digital Self-adaptive Dynamic Electro-hydraulic Fatigue Testing Machine

Based on electro-hydraulic servo control technology and computer control technology, this thesis studies the digital self-adaptative control dynamic electro-hydraulic fatigue testing machine, which is widely applied in several fields, such as aerospace, national defense and military industry, railways equipment, machinofacture, vehicle and ship industry, metallurgy, mine engineering, architectural material, petrochemical industry, plastic and rubber industry, wire and cable industry, etc. The target of the research is that the system comes up to the technical requirements, including high-responsivity, high static precision, high dynamic precision, digital control, self-adaptative control.Consulted numerous related literatures and reference materials at home and abroad, hydraulic system and control system are designed, relative components are chosen or manufactured, and then experiment study of the system is done.At First, the thesis researches the dynamic characteristic of servo valve, model of dynamical outfit about valve control unsymmetrical hydraulic ram, influence of the additional disturbing force and the systematic static error, on the base of analysis of fatigue testing machine system. Then the mathematical models of position control system and force control system are built. According to the principle of load-matching, the hydraulic dynamical outfit and power source system are designed and components are chosen. Then the correlative parameters of system model are calculated and the simulation study is carried out. Furthermore, the stability and controllability of the both control systems are analyzed.Next, the hardware and software of control system is designed. The control scheme of computer and data acquisition card are determined, meanwhile the extra circuit and digital filter are designed. The control interface and control software is designed by graphical programming language—LabVIEW. In addition, the thesis discusses the method of using real-time system development environment basing on MATLAB/xPC, by using which the effective control of testing machine is achieved in Simulink external mode. Through some tests with the system, which indicate the availability and validity of the control system and the correctness of hardware and software's design and choose, the results show that all performances have achieved.Finally, the thesis introduces the self-adaptive control strategy of the system. Self-optimization control and zero auto-tuning algorithms are mainly presented, and the tips of switch between position control and force control is studied.