Study On Measuring Model And Experiment Of Torsional Vibration For The Rolling Mill's Drive System

The rolling mill's drive system, which transmits the rotating mechanical energy to roller, is an important component of the rolling mill. With the continuous improvement of the rolling speed and intensity, the abnormal instability phenomenon offen occurs due to the torsional vibration of the rolling mill's drive system. The torsional vibration causes fatigue damage and life reduction of the rolling parts. Further, the torsional vibration affects products quality and production efficiency. Torsional vibration suppression of the rolling mill's drive system is the key to stable operation of rolling mill, and the accurate measuring model is the premise of torsional vibration suppression. The project is supported by the national major technologies and equipment development projects for 10th-5-year Plan of China (Development of the large broadband steel cold rolling complete sets of equipment/Research and application on the key technology of the rolling mill's drive system torsional vibration.Grant No.ZZ02-13B-02-03-1). The theory and experiment of the rolling mill's drive system measuring model were studied. On the basis of torsional vibration mechanism and drive system dynamics model, the rolling mill's drive system measuring model was proposed. The dynamic response solution of the measuring model was obtained. The experimental results showed the effectiveness and feasibility of the measurement model.Firstly, the torsional vibration mechanics of rolling mill's drive system was studied, and the influence of rolling load on torsional vibration was analyzed. Based on the lumped parameter modeling method, single straight string lumped parameter system model and multiple branch lumped parameter system model were studied. According to D'Alembert-Lagrange dynamic principle, the two degrees of freedom dynamic model and the multiple degrees of freedom dynamic model of the rolling mill's drive system were established, and the inherent characteristics of system were known.Secondly, on the basis of torsional vibration dynamic model, the torsional vibration linear measuring model of the simplified rolling mill's drive system was established, and the measuring model under mutation loading and cyclic loading was studied. Based on the torsional vibration linear measuring model and typical nonlinear factors, the torsional vibration nonlinear measuring model of the rolling mill drive system was proposed. By constructing Lyapunov function, the stability of the nonlinear measuring model was analyzed. The nonlinear measuring model under different frequency forcing excitation was studied using the method of perturbation. For the key point unmeasured problem which was caused by the structure complicacy and infection factor complicacy, the soft measuring model was established and the torsional vibration measurement of the unmeasured point was realized.Thirdly, the torsional vibration multiple degrees of freedom measuring model was established on rolling mill drive system. When the system disturbance forms are time function, velocity function and displacement function, the dynamic response of the measuring model under the different boundary conditions, the typical load and the space was studied. The torsional vibration evolution mechanism of the rolling mill drive system was revealed, and the theoretical foundation of the rolling mill's torsional vibration measurement was established.Fourthly, in order to certify the measuring model, the measured signal feature must be extracted effectively. For the nonlinear and nonstationary characteristics of the torsional vibration measured signal, the torsional vibration signal processing method based on Empirical Mode Decomposition (EMD) was studied. The EMD algorithm was given, and the mode fission phenomenon caused by noise signal and the influence of the end effect on decomposition results were analyzed. The medium filtering denoising algorithm, the nonlinear wavelet threshold denoising algorithm and the envelope extreme extension algorithm were studied. The validity of EMD was improved.Finally, the torsional vibration measurement system was designed, and the dynamic experiment was finished on the torsional vibration analogue platform. The torsional vibration feature of the measurement signal was extracted by empirical mode decomposition and Hilbert trasnsform. The availability and feasibility of the measuring model was verified.