The Research Of The Controller For The Single-Axis High Frequency Electro-Hydraulic Shaking Table

As a key facility in reliability test, electro-hydraulic shaking table is widely used in many important project fields, such as the environmental test of aircrafts, vehicles and ships, the high-frequency fatigue test of engineering materials; the seismic test of bridges, high-rise buildings and other large engineering and construction, etc. Therefore, the level of technology and performance of electro-hydraulic shaking table will directly affect the technological progress and the development of these industrial fields. So the study of electro-hydraulic shaking table is an important fundamental research.The working frequency of the conventional electro-hydraulic shaking table constructed by a servo valve and a hydraulic cylinder or a motor is limited fairly narrow by the frequency response capability of the servo valve. The spool of2D valve (two-dimensional control valve) has two freedoms. The shaking table based on2D valve can work at a high frequency over2000Hz.The2D valve controlled shaking table’s control system can be divided into three parts: the frequency control, the amplitude control and the bias control. The rotary and sliding motions of the spool are independently exploited to control the frequency and the amplitude of the agitated vibration respectively. Since the2D valve is a rotary valve, it can’t realize the bias control by introducing a bias control signal to compose a closed loop control, as an ordinary electro-hydraulic servo system does. Thus we realize the bias control by connecting a digital servo valve in parallel with the2D valve and the hydraulic cylinder.The contents of each chapter are listed as follows:In chapter1, the research status and the development trend of the shaking table are summarized. The paper expounds the purpose and meanings of this research.In chapter2, the mathematical model of the2D valve controlled electro-hydraulic shaking table with single piston rod is constructed. And use MATLAB to simulate the amplitudes respectively at various frequencies and spool displacement. In chapter3, the principle and the sheme for the bias control of the2D valve controlled shaking table is elaborated.In chapter4, the hardware and software sheme of the shaking table’s controller based on DSP is elaborated. The controller is used to realize the frequency control, the amplitude control and the bias control of the shaking table. In chapter5, the experimental platform is constructed, The experimental result shows that the bias control system’s step response time is2.5seconds, and the steady-state error is3.04%.When the shaking table works at a frequency of1Hz, the steady-state error of vibration central position is0.3%, when the frequency comes to100Hz, the steady-state error is1.35%. Using the controller to control the frequency of the shaking table, the acceleration spectrums at100Hz,400Hz,1000Hz,1500Hz are acquired. Using the controller to control the amplitude, the waveforms at the spool displacement of0.5mm,1mm,1.5mm are acquired.In chapter6, a summary and a prospect of this thesis is proposed.