| Electro-hydraulic servo vibration table is an important experimental equipment for engineering research.It is widely used in many important industrial fields such as aerospace,automotive,and construction.The vibration test is to fix the test piece on the test platform and simulate the effect of the load on the test piece to study the influence of the load on the test piece,the reliability analysis of the test piece or the performance analysis of the vibration reduction system.With the improvement of reliability requirements for products,especially for aerospace products,the performance requirements of vibration test systems,which are key equipments for reliability tests,are also increasing.In the field of engineering technology,improving the accuracy of timedomain waveform reproduction of such devices has become a hot topic of research.Firstly,this paper systematically summarizes and deeply analyzes related research at home and abroad,and introduces the research significance and main research contents of the paper.Then based on the previous analysis of multi-axis electro-hydraulic vibration table servo control system with three-state control strategy,as well as the analysis on the servo control system of the multi-axis electro-hydraulic vibration table with independent degree of freedom controller and pressure stabilization controller we model after considering the basis of the nonlinearity of the hydraulic actuator flow and the dead zone,the zero deviation,the coulomb friction and the viscous firction of the servo valve he effects of various nonlinear factors and excitation signal amplitudes on the system acceleration output response are also simulated and analyzed.However,due to the timevarying nature of the system,the combined effects of various nonlinear factors,and the effect of temperature on the performance of each component,eliminating a certain nonlinearity alone does not fundamentally eliminate harmonics.Instead,it increases the amount of calculation and makes it difficult to achieve real-time control.Therefore,it is necessary to design a harmonic elimination controller that can achieve real-time control of harmonic elimination caused by any nonlinearity.Due to the nonlinear characteristics of the above-mentioned multi-axis electrohydraulic vibration table and the uncertainty of the test conditions,the waveform of the actual response signal of the acceleration of the hydraulic vibration table is seriously distorted,the amplitude stability is poor,and compared with the expected acceleration signal,the amplitude attenuation,phase hysteresis and higher harmonics are larger and the frequency of harmonics is usual y an integer multiple of the test signal frequency.These problems reduce the credibility of the sinusoidal vibration test results and even make the test impossible.Therefore,in order to design a harmonic elimination controller that can run online,it is necessary to analyze the adaptive control algorithm first.This paper mainly compares the difference of convergence speed and mean square error of the adaptive transversal filter designed based on LMS algorithm,ASLMS algorithm and gradient algorithm.Based on the research of adaptive filter,firstly,the amplitude-phase controller is used to improve the signal tracking index,and high-precision sinusoidal vibration control is achieved.Then an adaptive harmonic elimination controller was designed to suppress harmonic components respectively based on ASLMS step size adaptive minimum mean square algorithm and gradient algorithm.This paper verifies the advancement of the research work on the multi-axis electrohydraulic vibration table through experiments and analysis. |
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