Failure of cutterhead driving system (CDS) of tunnel boring machine (TBM) often occurs under shock and vibration conditions.\nTo investigate the dynamic characteristics and reduce system vibration further, an electromechanical coupling model of CDS is\nestablished which includes the model of direct torque control (DTC) system for three-phase asynchronous motor and purely\ntorsional dynamic model of multistage gear transmission system. The proposed DTC model can provide driving torque just as the\npractical inverter motor operates so that the influence of motor operating behavior will not be erroneously estimated. Moreover,\nnonlinear gear meshing factors, such as time-variant mesh stiffness and transmission error, are involved in the dynamic model.\nBased on the established nonlinear model of CDS, vibration modes can be classified into three types, that is, rigid motion mode,\nrotational vibration mode, and planet vibration mode. Moreover, dynamic responses under actual driving torque and idealized\nequivalent torque are compared,which reveals that the ripple of actual driving torquewould aggravate vibration of gear transmission\nsystem. Influence index of torque ripple is proposed to show that vibration of system increases with torque ripple. This study\nprovides useful guideline for antivibration design and motor control of CDS in TBM.
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