## 2 Proposed Method and Environment
### Design and Fabrication of Experimental Rotating Equipment  
The simulation equipment was manufactured as described below. Pulse 3560C and four accelerometers (B&K 4371) were used to acquire the rotation and vibration data, and the data acquisition time for each condition was 30 s. Table 1 lists the specifications of the data acquisition system. Figure 2 presents the RK4 (Rotor-kit) of the lab-scale rotating simulation equipment, which is the experimental model, and the locations of the sensors used in the experiment. The experiment system was composed of a motor to operate the rotating equipment, a flexible coupling connecting the rotor and motor, and two copper sleeve bearings supporting the rotor. An 800 g disk was installed between the bearings to simulate the unbalance fault. Sensors were installed on the drive-end side of the motor and rotor. The measurements were taken at locations in the vertical and axial directions of the motor and rotor. The experimental equipment was operated at 2000 RPM (Rotating Per Minute), avoiding 2400 RPM, which is the first critical speed. In this experiment, fault simulations were carried out by simulating four representative conditions of the rotating equipment: Normal, Unbalance, Misalignment, and Shaft rubbing conditions. Figure 3 presents the methods of application of the normal condition and each type of fault. A normal condition was obtained after performing shaft balancing using the RK4, and the residual unbalance was measured to be 0.02 g/117.4\({}^{\circ}\) after balancing. Unbalance was induced by attaching a 3.2 g object in a direction towards the location of residual unbalance (117.4\({}^{\circ}\)). Misalignment was achieved by installing a 4 mm shim plate at the foot of the drive-end side of the motor, and shaft rubbing was applied in the horizontal direction using a magnetic base. In addition, a contact device made from Teflon was used to minimize the damage to the axis that may occur due to rubbing. \begin{table}
\begin{tabular}{c c} \hline \hline
**Type** & **Properties** \\ \hline Pulse 3560C & Operating Freq. range: 0\(\sim\)25.6 kHz \\ (B\&K) & Direct/Constant Current Line Drive (CCLD)/Microphone (MIC). preamp 1 Tacho \\  & Conditioning \\ Accelerometer & Operating Freq. range: 1\(\sim\)25.6 kHz \\ (B\&K 4371) & Operating Temp. \(\sim\)50 C\(\sim\)121 C \\  & Sensitivity: 9.84 pC/g \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of the data acquisition system [3]. Figure 2: Measurement of experiment system. Unbalance is the most fundamental fault that causes vibrations in rotating equipment. Unbalance occurs when the mass distribution of the rotor is asymmetric with respect to the axis centerline, and all the causes of unbalance exist to some degree in the rotors. Excessive unbalance increases the vibrations and noise of the rotating equipment. As a result, fatigue destruction may occur due to a deterioration of the bearings and consumable parts. Misalignment is one of the most common faults of rotating equipment along with unbalancing [41], and refers to a condition where the centers of the two axes do not coincide, or a condition where the centers coincide but are not parallel. A large degree of misalignment can cause overheating of the coupling, an increase in the shaft cracks and fatigue, and damage to the bearings and consumable parts. A rubbing fault is a secondary transient phenomenon caused by excessive unbalance and misalignment in rotating machinery [42]. Rubbing may be caused by the occurrence of friction between the stator and rotor caused by excessive vibrations, or a narrow gap due to thermal expansion during equipment operation. Continuous rubbing during the operation of rotating machinery may cause the separation of parts or axis bending, and severe rubbing can lead to the destruction of the rotating equipment. The sampling rate of the obtained signals was 65,536 Hz.