## 4 Simulation Results Using PI, PID, and ISTSMC Strategy
The output voltage of the VTOL platform varies between 4 V and 8 V. The values of different physical parameters are shown in Figure 9.  
Figure 6: Pitch of the VTOL system and motor current of actuator model based on cascaded loop controller. Figure 7: (**A–D**) represent the pitch of the VTOL system and motor current of actuator model based on ISTSMC and cascaded loop controller. and tabulated in Figure 8 and Table 1, respectively. The system is subjected to an ambient temperature of 28 degrees and humidity of 38% in the control and instrumentation lab of Balochistan University of Engineering and Technology Kluzdar, Pakistan. Figure 9 shows the motor current \(I_{m}\) (red) of the propeller assembly with the \(I_{ref}\) (blue) as a reference current level. The motor current \(I_{m}\) (red) of the propeller assembly tracking the \(I_{ref}\) (blue) as a reference current level is shown in Figure 9. The tracking performance of the motor current based on the PI controller using the experimental setup based on LabVIEW, shown in Figure 9, is closely mapped to Figure 5 based on the PI controller using MATLAB simulation. In this case, the hardware of the VTOL system is operated using a PI controller, with the gain calculated using Equation (12) as \(k_{i}\) = 648 V/A and \(k_{p}\) = 17.4 V/A. Figure 10 shows the pitch (deg) of the VTOL system while oscillating along the horizontal axis based on the PI controller. Initially, at static conditions, the aluminum arm of the VTOL system reaches an angle of \(-25^{\circ}\) along the horizontal axis. When switching the VTOL experimental setup and setting the pitch (deg) parameter of the aluminum arm, raising its position, and reflecting at \(10^{\circ}\) above the horizontal position, the system oscillation decays slowly with a significant tracking error, as observed in the simulation conducted in MATLAB and as shown in Figure 5.  
Figure 8: Experimental setup of VTOL system. Figure 9: VTOL motor reference current and output current in LabVIEW based on PI controller. Figures 11 and 12 show the pitch of the VTOL system with the actuator motor current \(I_{m}\) tracking \(I_{ref}\) based on the cascaded control strategy using PID and PI in the LabVIEW platform interfaced with the QNET VTOL experimental setup, considering the values of \(k_{p}=0.9,k_{i}=0.13,\text{and}\)\(k_{v}=0.12\), computed using Equation (21). The gains of the inner loop current controller are obtained as \(k_{i}=648\) V/A and \(k_{p}=17.4\) V/A. The results obtained using the experimental hardware setup are shown in Figures 11 and 12, and they are closely mapped to the simulation analysis conducted in MATLAB, as shown in Figure 5.0 In Figure 11, the measured response of pitch \(\theta_{m}\) shows slight delay due to the inertia of the overall VTOL assembly as compared to the reference value \(\theta_{ref}\). The \(\theta_{m}\) tracking the pulse generator signal \(\theta_{ref}\) has a frequency of 0.34 Hz, magnitude of 2, and pulse width of nearly 50%. The experimental result based on the cascaded control strategy is better than that of the PI-based VTOL system shown in Figures 9 and 10. The actuator motor current \(I_{m}\) in Figure 12 accurately tracks the \(I_