Research On Testing Load Adaptive Fuzzy Control Technology Of The Resonant Material Fatigue Tester

Metallic material fatigue test is a very important testing way to study the fatigue life of specimens under the different alternating load, it has great significance for the produt design. For all fatigue tests, the fatigue crack propagation test is the most important and basic test according to the related international standard. Currently, the major problem in high-frequency fatigue test system is that during the test process the stiffness of the specimen will change with the crack’s growing, resulting in the natural frequency and vibration load changes. In order to achieve the high precise control of the testing load, an accurate mechanical model of the controlled object has to be established, the dynamic characteristics of the system has to be analysed.And on this basic, deeper study in the control strategy of testing load. The major research in this paper is as follows:1、Established the two freedom degrees of linear time-varying model of the high-frequency fatigue tester, got the law of the natural frequency of the specimen change with time, analysis of the dynamic characteristics of the dynamic fatigue test system2、Designed the vibrating load adaptive fuzzy PID controller of resonant metallic material fatigue testing system and performed the Matlab simulation.analysis, because of the complexity of the fatigue test system model, and the requirements of fast-track, high-precision control response.3、Developed a implementation process of high-frequency fatigue testing load control system, performed the vibration load control system design. Proposed a serial communications protocol between High-frequency fatigue test system and on-site PC controlle r4、Completed the crack propagation experiment, testing load adaptive fuzzy PID controll and PID controll experiment, the experimental data and the results had been analyed.The analysis of dynamic characteristics of fatigue testing machine in this paper provided a theoretical basis for constant amplitude control of testing load. Dynamic load control system designed according to this theory has been greatly improved the control performance, which has important significance and application value to the development of fatigue test technique.