## 4 Experimental Verification  
To validate the dynamic characteristics of the electric drive system under self-fault-tolerant control, the experimental platform shown in Figure 13 was constructed. The platform comprises a load motor, controller, helical planetary gearbox, circuit breaker, torque sensor, power supply, non-phase shift DTP-PMSM, and host computer. Vibration monitoring of the gear system employs an accelerometer with 98.29 mV/g sensitivity and a data acquisition card at 10 kHz sampling rate to analyze vibration signals for system dynamic response. During experiments, vibration acceleration signals of the gear system were acquired via the accelerometer, processed through the acquisition card, and subsequently analyzed for dynamic characteristics. Open-phase faults were simulated by connecting a circuit breaker in series with phase D of the controller's six-phase power supply circuit (Figure 14), allowing controlled fault triggering. Figure 15 compares the experimental dynamic characteristics of the electric drive transmission system under rated conditions (3000 r/min and 0.5 Nm) in normal operation, open-phase faults, and self-fault-tolerant control. As shown in Figure 15a,b, after D-phase open fault, the self-fault-tolerant control strategy promptly transitions the system into a self-fault-tolerant mode. The current of the faulty D phase rapidly decays to zero, and the current amplitudes of the E and F phases decrease. Conversely, the current amplitude of the healthy A phase increases and the current amplitudes of the B and C phases also increase  
Figure 14: The experimental self-fault-tolerant control method. Figure 13: Experimental platform. slightly. In contrast, during a D-phase open fault, conventional control (without fault tolerance) causes significantly increased current ripple in every phase. Figure 15c shows that the rapid intervention of self-fault-tolerant control enables the electromagnetic torque to quickly recover to the rated value. After a brief fluctuation at the moment of the fault, the torque stabilizes. However, under an open-phase fault without control intervention, the electromagnetic torque pulsation intensifies substantially. The measured dynamic response process under rated operating conditions closely matches the simulation results, verifying the simulation model's accuracy in representing the system's self-fault-tolerant operational capabilities. Figures 16 and 17 compare the experimental spectral characteristics of the system under rated conditions in normal, open-phase faults, and self-fault-tolerant control. As shown in Figures 16a and 17a, compared with the normal operation, the amplitudes of odd-order harmonics such as the 3 rd, 5 th, and 7 th in the phase current spectrum increase under both open-phase faults and self-fault-tolerant control conditions. However, under self-fault-tolerant control, the increase in harmonic amplitudes is significantly smaller than that under the open-phase faults condition. Figures 16b and 17b show that open-phase faults can causes a significant increase in the amplitude of even-order harmonics such the 2 nd, 4 th, and 6 th in the electromagnetic torque spectrum, with the 2 nd harmonic amplitude increasing by approximately 25 dB. In contrast, after applying self-fault-tolerant control, the overall amplitude of the electromagnetic torque spectrum remains largely unchanged, and only the amplitude of the 2 nd harmonic component exhibits a slight  
Figure 15: Experimental dynamic response of electric drive transmission systems at rated conditions open-phase faults and before and after self-fault-tolerant control: (**a**) ABC phase currents; (**b**) DEF phase currents; (**c**) electromagnetic torque. increase (approximately 5.6 dB). As shown in Figures 16c and 17c, open-phase faults significantly amplify the 2 nd and 4 th harmonic components in the planetary gearbox vibration spectrum by approximately 8.6 dB and 9.8 dB, respectively.