# Predictive Current Control for Switched Reluctance Motor Based on Local Linear Phase Voltage Model
## 3 Experimental Verification  
In order to prove the superiority of the proposed PCC over the conventional HCC, experiments were conducted based on the test bench shown in Figure 7. The parameters of the experimental SRM are listed in Table 2. A magnetic powder brake was used as the load machine. A three-phase asymmetric half-bridge circuit was used as the power converter. MOSFETs were selected as the power switches. A 72 V battery was used as the DC power supply. The STM32F103 RCT6 microcontroller (MCU) was used to realize the control algorithms.  
\begin{table}
\begin{tabular}{c l} \hline \hline
**Symbol** & **Meaning** \\ \hline \(U_{\text{dc}}\) & DC-link voltage \\ \(v\), \(i\) & Voltage and current of a phase winding \\ \(R_{s}\), \(L\), \(L_{\text{inc}}\) & Resistance, inductance and incremental inductance of a phase winding \\ \(\theta\), \(\omega\) & Rotor position and speed \\ \(P\), \(Q\) & Slope and intercept of the local linear phase voltage model \\ \(T_{\text{P}}\), \(f_{\text{P}}\) & PWM cycle and frequency \\ \(M_{\text{CTR}}\) & Maximum value of the PWM counter \\ \(CR_{1}\), \(CR_{2}\) & Comparison values for the PWM drive signals of the upper and lower power \\ \(CR_{\text{U}}\), \(CR_{\text{L}}\) & Upper and lower limits of the comparison values \(CR_{1}\) and \(CR_{\text{L}}\) \\ \(T_{\text{cal}}\) & Calculation time of the comparison values \\ \(k\), \(\Delta\) & Subscripts denoting current time index and quantities related to phase A \\ \(\cdot\), \(-\) & Superscripts denoting referenced and average quantities \\ \(\Delta\) & Triangle on the left of other symbols denoting incremental quantities \\ \(\overline{v}_{\text{A},\omega,\sigma}\) & Average voltage during the time interval from the time index \(sv\) to the time index \(ev\) \\ \(\Delta I_{\text{A},\Delta,i,\sigma}\) & Difference between phase A currents at time indexes \(si\) and \(ei\) \\ \(\Delta I_{\text{A},\Delta,t,\sigma}\) & Time difference between time indexes \(st\) and \(et\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: List of symbols in formulas of Section 2.  
Figure 6: Current control in stage II.  
Figure 7: Experimental bench of the switched reluctance motor drive system.  
For the proposed PCC, the PWM frequency was set to 10 kHz; the upper and lower limits of comparison values were set to 80% and 20% of the maximum value of the PWM counter, respectively. For conventional HCC, the current sampling and control frequency were both set to 20 kHz to make a fair comparison; the hysteresis band was set to 0.5 A. The reason for the PWM frequency selection is explained in Section 3.3 below.  
To quantify the overall current-tracking performance, the current root-mean-square error (RMSE) is defined as  
\[i_{\text{A,RMSE}}=\sqrt{\frac{1}{N}\sum_{j=1}^{N}i_{\text{A,err}}{}^{2}}= \sqrt{\frac{1}{N}\sum_{j=1}^{N}\left[i_{\text{A}}^{*}(j)-i_{\text{A}}(j)\right] ^{2}} \tag{21}\]  
where \(N\) is the number of data points.  
Similarly, to measure the torque ripple, the torque RMSE is defined as  
\[T_{\text{A,RMSE}}=\sqrt{\frac{1}{N}\sum_{j=1}^{N}T_{\text{A,err}}{}^{2}}= \sqrt{\frac{1}{N}\sum_{j=1}^{N}\left[T_{\text{A}}^{*}(j)-T_{\text{A}}(j)\right] ^{2}} \tag{22}\]