Simulation
E-Motor NVH via Hyperreduction
The Discrete Empirical Interpolation Method applied to laminated e-motor stacks reduces nonlinear frictional contact force evaluations by nearly two orders of magnitude, enabling NVH analysis of laminated electric motor designs in under 20 seconds.
Links & Resources
Laminated Structures and NVH
Laminated steel stacks are found throughout rotating electric machinery, including e-motors and power conversion equipment. Lamination suppresses eddy current losses, which is its primary function, but the resulting structure introduces a new challenge: the NVH behavior depends on the frictional contact forces between hundreds of individual laminae. In a finite element framework, capturing these forces accurately requires on the order of 100,000 contact force evaluations per iteration.
The Discrete Empirical Interpolation Method
DEIM, introduced 15 years ago as a hyperreduction technique for projection-based model reduction frameworks, addresses a specific cost bottleneck. Standard model reduction reduces the size of the system — the number of degrees of freedom. DEIM targets the evaluation cost of nonlinear functions within the reduced model, which quickly becomes the dominant expense once the model itself is small. It works by evaluating the nonlinear function only at a set of critical interpolation points and reconstructing the rest of the field from a snapshot-based basis.
The technique was explored previously in the context of gear contact simulations, where it provided around one order of magnitude reduction in contact force FLOPs. In that application, safeguarding the accuracy of the hyperreduced model proved difficult enough that the practical payoff was limited.
Laminated e-motor stacks present a more favorable case. The contact pattern is geometrically regular, the laminae are nominally identical, and the deformation fields are smooth enough that a compact DEIM basis can capture them accurately.
Results
The implementation reduces contact force evaluations by nearly two orders of magnitude without significant loss of accuracy in contact force, stress or eigenfrequency prediction. Full NVH analysis of a laminated e-motor — from FE model generation through reduced-order model preparation to time-domain simulation — completes in approximately 20 seconds. This enables close to 200 design parameter variations per hour, which is the threshold where simulation becomes a practical design exploration tool rather than a post-hoc check.