Distortion Analysis And Control For Electro-magnetic Vibrator System

As a high-precision geophysics exploration method, seismic exploration iswidely used in mineral resources prospecting and geological structure explanation. Ininternational seismic exploration, vibrator has become main seismic source.Electro-magnetic vibrator is a broadband vibrator, which have better performance inshallow high-resolution seismic exploration compared to other types of vibrators.However, with increasing frequency by electromagnetic vibrator, signal distortioncaused by nonlinear coupling between vibrator and the ground become more andmore prominent, which limited seismic exploration precision. In the paper, nonlineardistortion of electro-magnetic vibrator were researched focused on thevibrator-coupled ground system model, distortion analysis and distortion control, thecharacteristics of nonlinear distortion were analyzed and the control strategies weregiven, and a solution of integrative controller for electro-magnetic vibrator was putforward, which provide theoretical basis for further study of electro-magnetic vibratorsystem and motion control.First, dual-parameter linear elastic equivalent model was established bykinematic principle based on mechanical structure characteristics of electro-magneticvibrator. On this basis, taking several nonlinear factors including system flaws ofelectro-magnetic vibrator, vibrator-coupled ground effect, and scale effect of rock andsoil into consideration, piecewise-linear elastic equivalent model was established. Atlast, a test method of modeling based on extended least squares system identificationwas proposed.Second, considering the effects of system nonlinear, both qualitativeand quantitative analysis for amplitude and phase distortion were conductedby numerical simulation and experiments, and the characteristic parameters of seismicwavelet under different distortion. Then distortion measurement and analysis for domestic vibrator, PHVS-500, was conducted. The results shown that harmonicdistortion in low frequency and nonlinear phase distortion in high frequency wereserious.Finally, in order to solving signal distortion of electro-magnetic vibrator, the PIDcontrol strategy for determinate model, PID control with feed-forward compensationfor non-minimum phase system, and full digital phase lock control for phasedistortion was introduced. In consideration of the completed nonlinear characteristicsand uncertain model parameters of vibrator, a generalized predictive control strategywith strong robustness based on generalized extended least squares systemidentification algorithms was proposed and verified by numerical simulation. At last,a design scheme of integrative controller for electro-magnetic vibrator was putforwardand three types of conventional lock-control methods before the zero phasedistortion feed-forward compensation control. In consideration of the vibrator Delaycharacteristics and nonlinear characteristics, the study of generalized predictivecontrol strategy based on augmented least squares system identification algorithms,numerical simulation, verification that the method can control the vibrator distortionin a certain range inside. Finally, the existing electromagnetic vibrator electroniccontrol system defects, proposed integrated controller based on FPGA design,hardware design simulation and test show that a stable and reliable for our fineexploration of mineral resources to provide a reliable technical support.