Analytical approach for geometric and topological analysis of fully coreless axial-flux permanent magnet machines for unmanned vehicle propulsion

Purpose This paper aims to perform a rigorous analytical evaluation of fully coreless axial-flux permanent magnet (AFPM) machines, targeting high-efficiency propulsion systems in unmanned vehicles. It focuses on the influence of permanent magnet geometries, winding topologies and current excitation types on key performance metrics. Design/methodology/approach A fully analytical framework is developed to evaluate 36 AFPM configurations. Using Coulombian charge and Biot–Savart laws, the magnetic field is modeled precisely. Back-electromotive force (EMF) and torque are derived under both sinusoidal and trapezoidal currents. Comparative analysis is performed based on total harmonic distortion (THD), torque ripple, efficiency and mass power density. Finally, the effectiveness and accuracy of the proposed approach are validated through 3D finite element simulations. Findings Performance is highly sensitive to the interplay between magnet shape, winding design and current waveform. Trapezoidal and curved rectangular windings, especially when paired with cylindrical or trapezoidal magnets and trapezoidal current, offer the best trade offs delivering high EMF, minimal THD, torque ripple reductions over 70% and efficiencies up to 97.5%. In contrast, triangular sector windings consistently yield the weakest performance. Originality/value This work introduces a fast, fully analytical tool for modeling and performance-driven optimization of coreless AFPM machines. It enables accurate, scalable evaluation of complex geometries and excitations without relying on computationally expensive numerical methods. The approach supports rapid design iteration and paves the way for next-generation high-speed, high-efficiency electric propulsion systems.