# Rotor Fault Diagnosis Method Based on VMD Symmetrical Polar Image and Fuzzy Neural Network
## 4 Experimental Analysis  
### Signal Acquisition  
For the sake of verifying the effectiveness of this proposed method, the rotor vibration signals used in this section are generated by ZT-3 rotor fault simulating experimental device, which could be seen in Figure 4. It is mainly consisted of one drive motor, onephotoelectric sensor, an acceleration sensor and a signal acquisition system. The motor speed is controlled by a speed controller, whose rated current of the motor is 2.5 A and the output power is 250 W. The rotor vibration signal is measured by using an AI005 acceleration sensor. The signal is processed by USB-5936 dynamic signal collector and it is stored by the computer. Table 2 shows the equipment list of the experiment.  
During the experiment, four fault states were simulated: bearing block looseness fault (BBLF), misalignment fault (MF), imbalance fault (IF) and local rub-impact fault (LRIF). Table 3 shows the fault simulation settings. Figure 5 shows the four faults in this experiment.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Order Number** & **Equipment Name** & **Main Parameters (or Components)** & **Quantity** \\ \hline \multirow{3}{*}{1} & ZT-3 rotor fault simulating & \multirow{3}{*}{1} & Speed regulation range of governor: 0–10,000 RPM; & \\  & experimental device & & 2 Shaft length: 320 mm, diameter: 9.5 mm; & 1 \\  & & & 3 Rotor width is 19 mm, diameter is 76 mm. & \\ \hline \multirow{3}{*}{2} & AI005 acceleration sensor & \multirow{3}{*}{1} & Sensitivity: (20 \(\pm\) 5 °C) 50 mv/mm/s2; & \\  & & & 2 Frequency range: 4–2000 Hz. & 1 \\ \hline \multirow{3}{*}{3} & USB-5936 dynamic signal & \multirow{3}{*}{1} & Number of channels: 4; & \\  & collector & & 2 Resolution ratio: 24 bit; & 1 \\  & & & 3 Dynamic range: 102 dB. & \\ \hline \multirow{3}{*}{4} & \multirow{3}{*}{Desktop computer} & \multirow{3}{*}{1} & CPU: i5-12490F; & \\  & & & 2 Graphic card: GeForce RTX 3060; & \\  & & & 3 Memory:512 G + 1 T; & \\  & & & 3 Hard disk: SSD + HHD. & \\ \cline{1-1}  & & & 1 Metal gasket; & 2 M2 screws; & \\ \cline{1-1}  & & & 3 Rub-impact screw; & 3 Data cable. & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Equipment list of the experiment.  
Figure 4: ZT-3 rotor fault simulating experimental device.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Order Number** & **The Fault Types** & **Fault Simulation Settings** \\ \hline
1 & BBLF & The screw used for fixing on the bearing block is loosened to simulate the looseness \\  & & fault of the bearing block. \\ \hline
2 & MF & Insert a metal gasket under the bearing block to raise the rotating shaft, and then \\  & & tighten the screw to simulate the misalignment fault. \\ \hline
3 & IF & Put two standard M2 screws (each screw weighs 0.3 g) into the \\  & & circumference-shaped groove of the rotor disc to simulate the imbalance fault. \\ \hline
4 & LRIF & A support is installed on the base of the test bench, and a threaded hole is reserved \\  & & above the support, a long screw made of plastic material is screwed into the \\  & & threaded hole to make it in contact with the rotating shaft of the rotor, as the rotation \\  & & speed increases, friction will occur between the rotating shaft and the screw, so as to \\  & & simulate the local rub-impact fault. \\ \hline \hline \end{tabular}
\end{table}
Table 3: The fault simulation settings.  
Figure 5: Four kinds of rotor faults: (**a**) BBLF, (**b**) MF, (**c**) IF, (**d**) LRIF.  
During signal acquisition, the signal sampling frequency was set to 2000 Hz and the motor speed was set to 2700 r/min. For each working condition of the rotor, 50 groups of samples were collected as a sample set in which 30 groups of signal samples were randomly chosen as the training sample set, the remaining samples were test sample set. The sampling length of each signal was 2000 points. Table 4 shows the relevant information on the sample signals used in this experiment.