# Dynamics Investigation on Axial-Groove Gas Bearing-Rotor System with Rod-Fastened Structure
## 1 Introduction
Based on time delays and feedback control gains, the dynamic behavior of the rotor supported by the self-acting three-axial-grooved gas-lubricated bearings were investigated by us [PERSON] et al. (2020), and a mathematical method used to obtain the dynamic characteristics of the nonlinear gas bearing-rotor system is presented. The unbalanced responses of a rigid rotor system supported by two-axial-groove gas bearings were analyzed by us [PERSON] et al. (2020); a numerical model was established and utilized to acquire the rich nonlinear phenomena. Continuous rotor models have been investigated thoroughly in rotor-gas bearing systems [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018). [PERSON] et al. [PERSON] et al. (2020) analyzed the rotor vibration characteristics of a gas bearing-rotor system, jointed by bolted-disk, by considering dynamic parameters of bolted-disk joints. Using the changes of the bending stiffness and tangential stiffness of the bolted-disk joints, the dynamic vibration characteristics of the rotor system were analyzed. An improved integrated modal technique with a free interface for reducing the number of degrees of freedom of a continuous flexible rotor system was presented by us [PERSON] et al. (2018). The nonlinear dynamic behavior of a continuous rotor with multi-span bearing support was investigated by our proposed method. [PERSON] and [PERSON] [PERSON] and [PERSON] (2018) proposed a new semi-analytical method for simulating the dynamic response of multi-segment continuous rotor bearing systems. [PERSON] et al. [PERSON] et al. (2018) numerically suppressed the unbalance responses of the continuous flexible rotor systems supported on the tilting-pad gas bearings by using the proportional-derivative control model. Compared with the continuous rotors, the rod-fastened rotors are widely used to adapt the actual working conditions in the aircraft engine and gas turbines. Because of the effects of contacts among the components, the dynamic characteristics of the rod-fastened rotor have been studied increasingly. [PERSON] et al. [PERSON] et al. (2020) proposed a method for investigating the dynamic stability and bifurcation behaviors of the rod fastening rotor and complete bearing system. The comparison results of the periodic motions and stability conditions in the rod fastening and continuous rotor-bearings system indicated that their bifurcation characteristics have a general resemblance. [PERSON] et al. [PERSON] et al. (2020) built a mechanical model of a rod fastening rotor-bearing system by considering the contact effect between the disks. To characterize the contact interface, a nonlinear stiffness matrix containing stiffness coefficients was presented. [PERSON] et al. [PERSON] et al. (2020) studied the dynamic charac teristics of an air bearing-rod fastening rotor system, which considered the heterogeneous bending stiffness of the contact interface; the linear and nonlinear dynamics behaviors were obtained. [PERSON] et al. [24] analyzed the effects of the internal damping of a rod-fastened rotor-bearing nonlinear system on the dynamic responses and rotor stability. With the effect of internal damping, the amplitudes of dynamic response were decreased to some extent at lower speed and amplified significantly at higher speed. The dynamic responses and bifurcation phenomenon of a rod-fastened rotor supported by a fixed-tilting pad gas bearing were investigated by us [25]. The periodic orbits, pendulum angles, and Poincare map with the different pad pivot ratios and preloads for the symmetrical and asymmetrical rotor-bearing system were analyzed. Our results showed that the rod-fastened rigid rotor system has better stability than the continuous integral rotor system. [PERSON] et al.