Modal-sensitive radial force shaping for NVH optimisation of switched reluctance motors

To meet the demand for high power density and low noise–vibration performance in switched reluctance motors (SRMs), this paper investigates radial-force shaping strategies from a modal-sensitive frequency-domain perspective. A multi-physics coupled modelling and analysis framework is developed to identify frequency bands in which structural modes exhibit high participation and are therefore prone to vibration excitation. Under identical copper-loss conditions, three representative force-sharing functions—Heaviside, linear and exponential—are systematically compared with conventional current chopping control (CCC). The results show that the NVH performance of an SRM is governed primarily by the spectral distribution of radial-force harmonics within modal-sensitive frequency bands, rather than by enforcing a constant resultant radial force. Heaviside-type shaping effectively suppresses high-frequency excitations in these sensitive bands and leads to reduced vibration response, but at the cost of increased torque ripple. In contrast, CCC provides smoother torque but introduces high-frequency radial-force components that coincide with dominant structural modes, resulting in elevated vibration levels. These findings reveal an intrinsic frequency-domain trade-off between radial-force and torque optimisation in SRMs, and provide new insights for multi-objective control design and electromagnetic–structural co-design.