Stability Analysis of Electric Motor Control System on two types of motors: DC Moog BN12HS-13AF-01 and AC single-phase Simtach AC120M-11J30A motors based on electromechanical parameters

Abstract

The analysis of stability in electric motor control systems is essential in automation because of the fundamental second-order electromechanical dynamics resulting from the interplay between electrical parameters (such as resistance and inductance) and mechanical characteristics (like inertia and damping). This research examines the DC Moog BN12HS-13AF-01 and AC single-phase Simtach AC120M-11J30A motors, both represented by first-principle derivations that incorporate parameters derived from experiments. The DC motor model, established with armature resistance (R = 9.8 Ω), inductance (L = 0.34 mH), torque constant (Kₜ = 0.0031 Nm/A), and inertia (J = 3.9×10⁻⁸ kg·m²), produces a comprehensive second-order transfer function of the shape G(s) = Kₜ / [(Js + B)(Ls + R)], facilitating thorough transient analysis. For the AC motor, electromechanical characteristics were derived from partial datasheet data and literature, resulting in an approximate second-order model that represents nonlinear influences from the coupling of stator and auxiliary windings. Step-response simulations with unity feedback in MATLAB indicate that the DC motor shows a quick settling time (14 ms), minimal overshoot (3.8%), and insignificant steady-state error (0.4%), whereas the AC motor displays a slower response (87 ms settling), increased overshoot (10.2%), and steady-state error (2.1%). Frequency-domain evaluation through Bode and Nyquist plots verifies wider gain and phase margins for the DC system (14.5 dB, 47.8°) compared to the AC system (6.2 dB, 28.4°). Sensitivity analysis with a ±20% change in key parameters indicates that the DC model demonstrates greater robustness to variations in inertia and damping. The key contributions of this research are: (1) a cohesive modeling method for both motor types based on electromechanical principles; (2) detailed performance comparisons in both time and frequency domains; and (3) determination of essential parameters influencing closed-loop stability. These findings facilitate effective control design for resource-limited or real-time embedded systems and emphasize the comparative benefits of DC motors in precision applications over AC motors.