The Research Of The Excitation Control System For The High-Frequency Fatigue Test Machine

Fatigue test machine is a machinery used for measuring metals and their components state at room temperature tensile, compressive or tensile and compressive alternating load fatigue test, fatigue life and other test machine, it is widely used for material experiment in aerospace, transportation and many other important engineering fields. Because of its high-thrust output, large displacement, etc., electro-hydraulic servo fatigue test machine can cover the shortage of the electromagnetic resonant test machine. It will have an important effect in metal fatigue experiment with good prospects for development in the future.In this paper, electro-hydraulic servo high-frequency fatigue test machine is considered as the application background, we do research to the core component-electro-hydraulic vibration exciter and its control technology. We use a2D excitation valve with two degrees of freedom to control the hydraulic cylinder, which can increase excitation frequency to2500Hz. Simultaneously, it can achieve the frequency control and amplitude control of the vibration exciter. In order to achieve the bias control of vibration center of the high-frequency electro-hydraulic vibration exciter to realize the output alternating stretching and compression loads of fatigue test machine, we place a2D digital servo valve in parallel with2D excitation valve, they both work on the double rods hydraulic cylinder to achieve the bias control of excitation center.The primary contents and research results are presented as follows:In chapter Ⅰ, discuss the research purpose and significance of fatigue test machine; introduce the operational principle of three different kinds of fatigue test machine:mechanical vibration, electromagnetic resonant and electro-hydraulic servo fatigue test machine, discuss the current research situation of fatigue test machine and its control technology at home and abroad.In chapter2, analysis and discuss the composition and operational principle of a high-frequency fatigue test machine and its core component-electro-hydraulic vibration exciter. Place a digital servo valve in parallel with the2D excitation valve to achieve the bias control of the excitation central position of the vibration exciter, thus to realize the output alternating stretching and compression loads of fatigue test machine. Then introduce the structure and working principle of the2D excitation valve and digital servo valve and establish their mathematical model. In chapter3, the model of the electro-hydraulic system is founded by Matlab and Simulink and simulation is done to analysis its output frequency characteristics and amplitude characteristics at different excitation frequencies and vibration amplitudes.In chapter4, complete the hardware and software design of electro-hydraulic vibration exciter’s embedded controller based on TMS320F2812, construct the excitation control system of fatigue test machine.In chapter5, experimental study is done to analysis the output load waveform at different vibration frequencies and excitation amplitudes. We get the load waveform at the excitation frequency of50Hz,100Hz300Hz,600Hz,800Hz,1000Hz,1500Hz,2500Hz and an axial valve port opening of0.5mm,1mm,1.5mm. Complete the direction control of the output load force, and do research to the variation characteristics of the output load force when the paralleled digital servo valve opens to the positive side50%,100%and to the negative side50%,100%. Experimental results show that the high-frequency fatigue test machine can achieve high-frequency, high-thrust and alternating tension and compression load output.In chapter6, summarizes the work done in the paper and look forward to further research work and orientation in the future.