## 5 Experimental Study
parameter mismatches, the overshoot of (a) was about 65.3% of the steady-state reference value, and the time to restore stability was about 0.012 s, while the overshoot of (b) was about 3.3% of the steady-state reference value, and the time to restore stability was about 0.006 s. Figure 15 shows that when the three parameters of the model were simultaneously changed to 1.5 times their actual values, the overshoot of (a) was about 53.3% of the steady-state reference value, and the time to restore stability was about 0.013 s, while the overshoot of (b) was about 4.3% of the steady-state reference value, and the time to restore stability was about 0.013 s. As can be seen in Figure 16, when the three parameters of the model were simultaneously changed to 0.75 times their actual values, the overshoot of (a) was about 67.3% of the steady-state reference value, and the time to return to stability was about 0.015 s, while (b) hardly produced any overshooting, and the time to return to stability was about 0.008 s. In terms of the time required to first achieve a steady-state value, it can be seen from the above three situations that (b) takes longer than (a). In terms of overshooting and the time needed to restore stability, it is clear that the weakened integral sliding mode surface not only weakens the overshoot due to the introduction of the integral term when the currents change, but that it also shortens the time required to reach a steady state. Figure 14: Experimental comparison of \(q\)-axis currents of two methods under current variation (0 A to 1.5 A) without parameter mismatches (\(R_{0}=R_{s}\), \(L_{0}=L_{s}\), and \(\psi_{f0}=\psi_{f}\)): (**a**) DPCC with normal integral sliding mode compensation combined with weight factors; (**b**) DPCC with weakened integral sliding mode compensation combined with weight factors. Figure 15: Experimental comparison of \(q\)-axis currents of two methods under current variation (0 A to 1.5 A) with simultaneous mismatches of three parameters (\(R_{0}=1.5R_{s}\), \(L_{0}=1.5L_{s}\), and \(\psi_{f0}=1.5\psi_{f}\)). (**a**) DPCC with normal integral sliding mode compensation combined with weight factors; (**b**) DPCC with weakened integral sliding mode compensation combined with weight factors. Figure 17-22 show the load variation experiment based on the simulation in which the \(dq\)-axis current variations of DPCC and DPCC with weakened integral sliding mode compensation combined with weight factor optimization are compared in the case of parameter mismatching. In the experiment, the DC voltage was set to 60 V, the rotational speed was 450 rpm, and the load torque increased from 0.2 to 0.5 Nm at 0.5 s and then decreased from 0.5 to 0.2 Nm at 3.5 s.  
Figure 16: Experimental comparison of \(q\)-axis currents of two methods under current variation (0 A to 1.5 A) with simultaneous mismatches of three parameters (\(R_{0}=0.75R_{s}\), \(L_{0}=0.75L_{s}\), and \(\psi_{f0}=0.75\psi_{f}\)). (**a**) DPCC with normal integral sliding mode compensation combined with weight factors; (**b**) DPCC with weakened integral sliding mode compensation combined with weight factors. Figure 17: Experimental comparison of \(dq\)-axis currents at 450 rpm with torque variation (0.2 to 0.5 to 0.2 Nm) and without parameter mismatches (\(R_{0}=R_{s}\), \(\psi_{f0}=\psi_{f}\), and \(L_{0}=L_{s}\)): (**a**) DPCC; (**b**) DPCC with weakened integral sliding mode compensation combined with weight factors. Figure 19: Experimental comparison of \(dq\)-axis currents at 450 rpm with torque variation (0.2 to 0.5 to 0.2 Nm) and inductance mismatch: (**a,b**) \(L_{0}=1.4L_{s}\); (**c,d**) \(L_{0}=0.5L_{s}\); (**a,c**) DPCC; (**b,d**) DPCC with weakened integral sliding mode compensation combined with weight factors. Figure 11:0 Experimental comparison of \(dq\)-axis currents at 450 rpm with torque variation (0.2 to 0.5 to 0.2 Nm) and resistance mismatch: (**a,b**) \(R_{0}=2R_{s}\); (**c,d**) \(R_{0}=0.5R_{s}\); (**a,c**) DPCC; (**b,d**) DPCC with weakened integral sliding mode compensation combined with weight factors.