Analysis of Radial Vibration Considering the Phase Shift of Modulated Electromagnetic Excitations in FSCW PMSMs for Robot Joint Applications

초록

In this article, the phase characteristics of the lowest spatial order modulated excitations and their influence on radial vibration are analyzed for fractional-slot concentrated winding (FSCW) permanent magnet synchronous motors (PMSMs) with pole–slot combinations satisfying 2p = S ± 2, which are widely adopted in robot joint applications. The phase shifts of the modulated radial and tangential forces, and moment are analytically derived by considering tangential air-gap electromagnetic force density with respect to the slot opening pitch. Then, 2-D finite-element analysis is used to characterize the phase relationships of the lowest spatial order modulated excitations under no-load and load conditions. The results show that the excitation phases depend on the slot opening pitch under no-load conditions, whereas they are primarily influenced by armature reaction under load conditions. Accordingly, the phase-dependent radial vibration contributions of the modulated excitations are established for different slot opening pitches and pole–slot combinations. The proposed analysis framework is further applied to FSCW PMSMs with different pole–slot combinations with 2p = S ± 2 to assess the generality of the observed phase characteristics. Finally, radial vibration contributions under no-load and load conditions are verified through vibration experiments.

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