Dynamic and Vibration Analysis of a Multimotor DC Drive System With Elastic Shafts Driving a Tissue Paper Machine

In this paper, the influence of the stiffness and damping of real elastic shafts on the behavior of a multidrive system driving a tissue paper machine is investigated. The drive system consists of four DC motors, where two of them drive the Yankee drying cylinder and the other two drive the presses section. Six-pulse thyristor bridge power converters that are connected to the same power transformer supply the motors. The inertias of the motors and the driven machines, in conjunction with the shaft stiffness, form mechanical resonators. Thus, resonance phenomena may occur, which may lead to undesirable results. This particular case results to two three-mass and one five-mass systems. This paper presents an analysis of the resonance frequencies of two sections of the machine during startup and machine production, considering the shaft stiffness (shaft diameter, length, and thickness). The elastic shafts eliminate the ripple of the motor electromagnetic torque, which is transferred to the driven machine. The behavior of elastic shafts with different stiffness in the transmission system is studied. Moreover, the steady state and dynamic behavior of the system considering the influence of the elastic shafts and vibration analysis were investigated using simulation. A model algorithm for system simulation was developed using the MATLAB/SIMULINK software. Characteristic simulation results are presented and are expressed in terms of speed and torque response. Considering the resonance frequency analysis and simulation results, mechanical design guidelines can be given for the most significant drive components in order to avoid torsional oscillation resonance phenomena and minimize torsional oscillations of the drive system.