## 4 Experimental Results  
A dual-inverter configuration was employed for an open winding 6/4 VFRM (State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin, China) to assess the effectiveness of the decoupled current control-based ITHESO in rejecting disturbances and reducing torque ripple. The setup included the particular specifications of the VFRM as outlined in Table 1, while a schematic representation of the experimental apparatus is presented in Figure 6. The operation of the VFRM was governed by a dual-inverter system, with control performed via a dSPACE 1202 connected to MATLAB 2015a, and the IGBT switching frequency was maintained at 10 kHz. The load for the experimental validation was provided by a dynamometer with a rated torque of 7.5 Nm, a power range of 750 W to 1500 W, and a maximum speed of 5000 rpm. This setup enabled realistic testing conditions, replicating dynamic torque and speed variations to evaluate the proposed control strategy. The analysis of the torque output from the VFRM was conducted utilizing a Kistler 4502A torque sensor in conjunction with a Yokogawa DL850E, which served as the oscilloscope for the experimental procedures. During the experimental procedures, the torque ripple of the VFRM, as assessed, is defined by \(\Delta T_{\text{ripple}}\), which is derived by deducting the minimum torque from the maximum torque and subsequently normalizing this difference using the average torque, as specified in (32). Simultaneously, the voltage utilization amplitude \(U_{\text{s}}\) is computed by taking the  
Figure 5: Diagram of the decoupled current control system based on ITHESO. harmonic current components is necessary because the fundamental current interacts with itself to generate the main torque ripple. In the proposed method, the remaining third harmonic current interacts with itself to offset the inherent torque ripple caused by the fundamental current, which can be verified experimentally. Figure 9 compares the transient responses of torque under ADRC and the proposed strategy, as demonstrated in the second experiment. Figure 9a,b shows the torque result when the speed increases from 600 rpm to 900 rpm. Figure 10a,b illustrates the system's behavior during a speed reduction from 900 rpm to 600 rpm. The analysis of these plots reveals the distinct advantages of the proposed strategy in terms of torque ripple reduction. Figure 8: Comparison of FFT analysis results of phase current when the speed is 900 rpm and the load is configured to 0.17 Nm. Figure 7: Comparison of steady-state waveforms at a speed of 900 rpm with a load configured to 0.17 Nm: (**a**) ADRC. (**b**) Decoupled Current Control. In terms of overshoot, the proposed strategy exhibits a clear advantage over ADRC. During both speed transitions, ADRC displays a significant overshoot, with torque peaking further from the desired value. In Figure 9, where the speed increases, ADRC overshoots notably, whereas the proposed method maintains the torque closer to the target. Similarly, in Figure 10, during the speed decrease, the ADRC control shows a pronounced overshoot, while the proposed strategy responds more smoothly. This reduction in overshoot with the proposed method indicates improved control over sudden torque changes, which is beneficial for minimizing mechanical stress on the machine. The proposed strategy also outperforms ADRC in terms of settling time. Across both speed changes, the torque under the proposed method reaches a stable state more quickly than with ADRC. This faster settling time suggests that the proposed strategy adapts more  
Figure 10: Comparison of transient state waveforms with a load configured to 0.17 Nm and decrease in speed from 900 rpm to 600 rpm. (**a**) ADRC. (**b**) Proposed strategy. Figure 9: Comparison of transient state waveforms with a load configured to 0.17 Nm and an increase in speed from 600 rpm to 900 rpm. (**a**) ADRC. (**b**) Proposed strategy.