Research On The Test And Control Of The Electromagnatic And Permanent Vibration Table

Compared with the traditional electromagnetic vibration table,the novel electromagnetic and permanent vibration table based on direct-drive principle is more suitable for the environmental vibration test experiments,because of its small heat dissipation,wide bandwidth,no mutual induction,convenient control of waveform,and the like.However,it suffers from complex nonlinearity such as hysteresis,which will coupled with severe harmonic distortion and affect the low-frequency performance.Moreover,the testing method about electromagnetic vibration table below 5Hz hasn't be stipulated in the national standard.In addition,over test about output force will damage the structure of the spacecraft.To address this issues,this paper presents the modeling of novel electromagnetic vibration table,the analysis about the mechanism of harmonic distortion,the testing method of low-frequency,the waveform tracking,the force limited control and the compensation of hysteresis.The main research are listed as follows.A direct-drive mechanism based on electromagnetic and permanent is presented and it is modeled with Hamilton principle.Based on the outline and velocity equivalent design of the cam,the dynamic model of the system is established.Then,the nonlinearity model is simplified when the output of the displacement is small enough.After that,a simulation is utilized to analysis the output characteristics and harmonic distortion of the system.Finally,the mechanism of the harmonic distortion is figured out according to the direct-drive structure and processing method.The testing method and index of electromagnetic vibration table below 5 Hz are designed to supply the national standard.Based on the testing index,a testing platform is established.The experimental results demonstrate that the novel electromagnetic vibration table has wide bandwidth,superior low-frequency output performance,low harmonic distortion.After that,the vibration tables with different mechanisms are compared in every aspect,the results demonstrated that the novel electromagnetic vibration table has the advantages of bigger displacement,lower vibration frequency and more stable waveform output.An adaptive inverse control strategy based on the Fx-LMS algorithm is applied to handle the harmonic distortion.The waveform tracking principle with adaptive inverse controller is presented.Then,in order to ensure the usage of LMS algorithm,a filtered-x signal is introduced,based on which the adaptive inverse controller is designed.After that,an experiment platform for waveform tracking is established,the experimental results validate that the strategy effectively improves the output waveforms of novel electromagnetic vibration table in the lowfrequency.In addition,the over test about output force will damage the structure of the spacecraft.Thus,a force limited testing system is designed to alleviate the over test.The experimental results come out the force limited control is efficient to sinusoidal signal.A modified repetitive controller is designed to handle the hysteresis nonlinearity in the low-frequency.A hysteresis decomposition method is presented.It is analyzed that hysteresis nonlinearity can be decomposed into a linear gain and a bounded-periodic disturbance for periodic signal input,thus,the complex modeling is avoided.Then,the PI controller is designed to control the linear system.The modified repetitive controller is designed to handle the hysteresis nonlinearity.Moreover,spectrumselection filter is applied to alleviate the amplification of the nonfrequency-doubled disturbance.The experimental results validate that the modified repetitive controller effectively improves the output waveforms of novel electromagnetic vibration table in the low-frequency.