## 4 Simulation Results and Experimental Results
### Experimental Results  
To validate the effectiveness of the automatic and accurate diagnosis method for demagnetization faults in DDPMSMs proposed in this paper, a prototype with demagnetization faults was developed, and a testing platform for fault characteristics of the machine was established, as shown in Figure 14.  
The experimental platform is composed of a prototype (Shenzhen, China, Yokokawa DMF280-270 FE), a driver used to drive the prototype (Shenzhen, China, Yokokawa VCHI-10-230), a magnetic powder brake (Haian, China, LanLing FZ400) a torque and speed measurement used to measure machine torque and speed (Beijing, China, BeijingZhong-HangKeDian ZH07-500Z), a DC power used to supply power to the magnetic powder brake (Haian, China, LanLing SC-1D), a host computer which is mainly responsible for data acquisition, storage, and fault diagnosis tasks (lenovo), a data acquisition card with 12 bit ADC resolutions used to collect the voltages of DFISs (American, NI USB-6009), and a digital oscilloscope (Shenzhen, China, Yokogawa 750). The implementation process of the experiment is as follows:  
(1) Develop a healthy prototype installed with the toroidal-yoke-search coils proposed in this article. Specifications for the healthy prototype are the same as the machine described in Section 2.3, which are listed in Table 2. This healthy prototype is installed on the testing platform shown in Figure 14, and the voltages of three toroidal-yoke-search coils (TYC1, TYC2, and TYC3) are collected by NI USB-6009 and transmitted to a host computer through  
Figure 14: Experimental setup. USB connection. The voltages of TYC1 and TYC2 of the healthy prototype under rated load and rated speed are shown in Figure 15a, and the voltages of the \(\text{SI}_{\text{m}}\) of the healthy prototype under rated load and rated speed are shown in Figure 15b. (2) Develop a demagnetization faulty prototype installed with the toroidal-yoke-search coils proposed in this article. Specifications for the faulty prototype are the same as the machine described in Section 2.3, but two permanent magnets have been removed to simulate a demagnetization fault. In order to reduce the eccentricity caused by the removal of permanent magnets, two permanent magnets (PM 11 and PM33) symmetrical with respect to the rotor centerline were removed to simulate a fault with a 100% demagnetization of the two permanent magnets in prototype. This demagnetization faulty prototype is installed on the testing platform shown in Figure 14 too. The voltages of TYC1, TYC2, and TYC3 of the faulty prototype under rated load and rated speed are shown in Figure 16a, and the voltages of \(\text{SI}_{\text{m}}\) and \(\text{SI}_{\text{a1}}\) of the faulty prototype under rated load and rated speed are shown in Figure 16b. (3) Partition \(\text{SI}_{\text{m}}\), \(\text{SI}_{\text{a1}}\), and \(\text{SI}_{\text{a2}}\) by electrical period, and input the partition signals to the three PNNs; then, the location of all demagnetized permanent magnets in the machine are identified. Figure 15a depicts the voltages of TYC1 and TYC2 under healthy machine conditions for the experimental results and the simulation results. The simulation results of the voltages of TYC1 and TYC2 are highly similar to the experimental results; the maximum error of the two results is 2.4%. This is caused by unbalanced voltage caused by the inhomogeneity of the permanent magnet magnetic field, environmental noise, etc. Figure 15b depicts the voltages of \(\text{SI}_{\text{m}}\) under healthy machine conditions for the experimental results and the simulation results. The simulation results of \(\text{SI}_{\text{m}}\) are in agreement with the experimental results; the maximum error of the two results is 1%. This is caused by environmental noise. It can be observed from Figure 16a that the sixth and seventeenth electrical periods of the \(\text{SI}_{\text{m}}\) of the demagnetization faulty prototype (when PM11 and PM33 are removed) have a signal.