## 4 Experiment  
To validate the proposed approach, both the proposed and conventional indirect FOC methods were implemented on a hardware testbench, as shown in Figure 14. The testbench utilized Texas Instruments' motor control platform (TMDSHVMVTRINSPIN), which is based on the TMS320F28335 digital signal processor (DSP). The development environment consisted of Code Composer Studio v5, along with the InstaSPIN library provided by TI (Texas Instruments founded in 1930; Headquartered in Dallas, TX, USA; [[https://www.ti.com](https://www.ti.com)]([https://www.ti.com](https://www.ti.com))). Table 2 summarizes the specifications of the induction motor used in the experiments. The control program was developed by extending the standard induction motor drive project available in the InstaSPIN library. This baseline project, verified and promoted by TI, served as the foundation for integration. The proposed control algorithm was implemented by embedding the estimation and switching logic modules into the existing control framework. The experiment was conducted under four combinations of speed commands and load torques: 720 rpm and 1620 rpm for speed, and 0 Nm and 1 Nm for torque. Representative results are shown in Figure 15, which records the phase-A stator current under each condition. The root mean square (RMS) values were calculated under steady-state operation. In the figure, the dashed lines represent the performance of the conventional indirect FOC method, while the solid lines correspond to the proposed method. Figure 14: The picture of the testbench. Figure 16 summarizes several RMS values of the phase-A stator current measured under different load torque conditions at two speed commands: 720 rpm and 1620 rpm. The experiment utilized the MAGTROL HB-3500 dynamometer, which generates output torque in response to an input current command. Therefore, the horizontal axis of the figure represents the current input to the dynamometer, which serves as a proxy for load torque. Additionally, since the rated current of the tested motor is 1.2 A, this value is defined as 1 per unit (pu) in the experimental environment. Accordingly, the vertical axis displays the RMS stator current in pu, as observed from the DSP development environment. As in previous figures, dashed lines indicate the performance of the conventional indirect FOC method, while solid lines represent the proposed method. In summary, compared to the conventional indirect FOC method, the proposed technique consistently results in significantly lower steady-state stator current while maintaining comparable torque and speed responses. The reduction in stator current contributes to decreased power transmission losses, enables the use of lower-rated components, and potentially reduces overall system cost. \begin{table}
\begin{tabular}{l l} \hline
**Quantity** & **Rated Value** \\ \hline Power & 1/4 (hp) \\ Speed & 1800 (rpm) \\ Voltage & 238 (V) \\ Frequency & 60 (Hz) \\ Number of poles & 4 \\ Rotor’s resistance & \(r_{r}=6.11\) (\(\Omega\)) \\ Stator’s resistance & \(r_{s}=11.05\) (\(\Omega\)) \\ Inductance of flux leakage & \(L_{ls}=L_{lr}=0.022484\) (H) \\ Mutual inductance & \(L_{m}=0.293939\) (H) \\ \hline \end{tabular}
\end{table} 
Table 2: The ratings and parameters of this real motor. Figure 15: The waveforms of phase A current in the steady state and theirrms values under different conditions. To enhance the comprehensiveness of the manuscript, a comparative summary is presented in Table 3. This table clearly highlights the distinctive features and advantages of the proposed method over other commonly adopted sensorless control strategies for induction motors. Specifically, the comparison encompasses key performance aspects, including robustness to parameter variations, transient response, steady-state accuracy, computational complexity, implementation cost, sensitivity to noise, and practical applicability. Figure 16: The rms value of phase A current vs. the torque load under different speed commands.