<![CDATA[This paper presents a comparative analysis of three control system design methodologies, namely Root Locus, Bode plot frequency response, and Proportional-Integral-Derivative (PID) control, applied to the longitudinal pitch dynamics of a fixed-wing Unmanned Aerial Vehicle (UAV). The plant is modeled as a fourth-order transfer function exhibiting non-minimum-phase (NMP) characteristics due to the presence of a right-half-plane (RHP) zero. These characteristics complicate the control design, resulting in an initial undershoot and pronounced oscillatory behavior. Open-loop analysis reveals a steady-state error of 1.790 and an Integral Absolute Error (IAE) of 54.765. To address these limitations, a proportional control strategy was designed using Root Locus and subsequently evaluated through frequency response analysis. Although the proportional controller improves the settling time to 5.694 s, it retains a steady-state error of 0.458 and produces an overshoot of 106.17%. To address these limitations, a PID controller was designed using a reference-tracking tuning procedure. The integral action eliminates the steady-state error, while the derivative action contributes to improved transient damping. The selected PID controller achieves a peak overshoot of 0% relative to the reference command, although a sub-reference damped oscillation remains and the settling time increases to 13.444 s. The PID controller reduces the total IAE from 54.765 to 2.081, corresponding to a 96.2% reduction. These results quantify the trade-off between transient response speed and tracking accuracy and provide a comparative basis for selecting control strategies for non-minimum-phase UAV pitch dynamics.]]>
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