Integrated Metric-Based Frequency Optimization for eVTOL PMSM Propulsion Systems

Rapid advancement of electric vertical take-off and landing (eVTOL) aircraft has increased the demand for electric propulsion systems that deliver high efficiency and high reliability. Among the available technologies, permanent magnet synchronous motors (PMSMs) are widely adopted due to their high power density and precise controllability. However, the selection of control-related frequency parameters, specifically the sampling frequency and the inverter switching frequency (PWM frequency), has received limited attention in early stage system design. These frequencies directly influence torque ripple, speed ripple, spectral fidelity, and the computational and switching burdens on the hardware. This study proposes an integrated metric-based optimization approach to identify effective combinations of sampling and switching frequencies in PMSM propulsion systems for eVTOL applications. A two-dimensional frequency sweep was performed and four performance metrics—torque ripple, speed ripple, aliasing magnitude, and computational or switching loss—were normalized against practical thresholds and aggregated into a unified performance score. The results reveal a distinct high-performance band where the sampling frequency is several times higher than the PWM frequency. Within this band, the optimal configuration reduced torque ripple by 31 percent compared with a suboptimal case and by 66 percent relative to a near-Nyquist case, while also demonstrating improved aliasing characteristics. In particular, the comparison highlights that minimizing torque ripple does not necessarily guarantee reduced aliasing, underscoring the importance of multimetric evaluation. The proposed method provides a quantitative framework for evaluating trade-offs and offers practical hardware-agnostic guidelines for frequency selection in embedded motor controllers, thus supporting the early stage design of PMSM-based propulsion systems in eVTOL aircraft and related electric mobility platforms.