Multivariate Sensitivity Analysis of Electric Machine Efficiency Maps and Profiles Under Design Uncertainty
Pith reviewed 2026-05-17 20:42 UTC · model grok-4.3
The pith
Multivariate sensitivity analysis assigns one importance index per design parameter for the full efficiency map or profile of an electric machine.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Multivariate global sensitivity analysis provides a single sensitivity index per parameter, allowing a holistic estimation of parameter importance over the full efficiency map or profile, in contrast to applying variance-based sensitivity analysis elementwise.
What carries the argument
Multivariate global sensitivity analysis, which computes a single sensitivity index per uncertain parameter over the entire efficiency map or profile instead of separately at each operating point.
If this is right
- Simplified models that vary only the influential parameters produce uncertainty estimates comparable to those from the full models.
- Polynomial chaos expansions require less computation than Monte Carlo sampling while delivering the same sensitivity indices.
- The method applies equally to electric machine models of low and high fidelity.
- Model simplification guided by the single indices per parameter maintains the overall uncertainty behavior of the maps and profiles.
Where Pith is reading between the lines
- The same single-index approach could rank parameters for other machine outputs such as torque or loss maps.
- Design optimization loops could restrict random sampling to the influential parameters identified here, lowering overall cost.
- Checking the indices against measured data from prototype machines would test whether nominal values adequately capture real manufacturing scatter.
Load-bearing premise
That fixing non-influential parameters to their nominal values after the analysis preserves the overall uncertainty behavior of the efficiency maps, as confirmed only by comparing uncertainty estimates between full and reduced models.
What would settle it
A case in which the reduced model, after fixing parameters according to the multivariate indices, produces clearly different uncertainty distributions or bounds on the efficiency map compared with the full model under identical input variations.
Figures
read the original abstract
This work introduces the use of multivariate global sensitivity analysis for assessing the impact of uncertain electric machine design parameters on efficiency maps and profiles. Contrary to the common approach of applying variance-based (Sobol') sensitivity analysis elementwise, multivariate sensitivity analysis provides a single sensitivity index per parameter, thus allowing for a holistic estimation of parameter importance over the full efficiency map or profile. Its benefits are demonstrated on permanent magnet synchronous machine models of different fidelity. Computations based on Monte Carlo sampling and polynomial chaos expansions are compared in terms of computational cost. The sensitivity analysis results are subsequently used to simplify the models, by fixing non-influential parameters to their nominal values and allowing random variations only for influential parameters. Uncertainty estimates obtained with the full and reduced models confirm the validity of model simplification guided by multivariate sensitivity analysis.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript introduces multivariate global sensitivity analysis (GSA) for assessing the impact of uncertain electric machine design parameters on efficiency maps and profiles. It contrasts this with the common elementwise application of variance-based Sobol' analysis by providing a single sensitivity index per parameter, enabling a holistic evaluation across the full map or profile. The approach is demonstrated on permanent magnet synchronous machine (PMSM) models of varying fidelity, with comparisons between Monte Carlo sampling and polynomial chaos expansions regarding computational cost. Sensitivity results are used to simplify models by fixing non-influential parameters to nominal values, with validation via comparison of uncertainty estimates between full and reduced models.
Significance. If the multivariate GSA successfully yields a single per-parameter index that captures holistic importance and the subsequent model reduction preserves uncertainty behavior, the work could facilitate more efficient uncertainty quantification and design exploration in electric machines by reducing the number of random parameters without sacrificing map-level fidelity. The demonstrations across model fidelities and the explicit MC-versus-PCE cost comparison are practical strengths that support broader adoption in computational engineering workflows.
major comments (1)
- [§5] §5 (model reduction and validation): The claim that uncertainty estimates from the full and reduced models confirm the validity of simplification guided by multivariate GSA is load-bearing for the central result. However, it is not clear whether the compared quantities include pointwise variance fields, quantile maps, or distributional distances across the torque-speed plane, or are limited to scalar summaries such as total output variance or mean efficiency. If the latter, this does not fully substantiate preservation of the spatial structure and operating-point dependence of the efficiency map uncertainty.
minor comments (2)
- [Abstract and results section] The abstract states that computations based on Monte Carlo and polynomial chaos are compared, but specific quantitative metrics (e.g., number of samples, convergence rates, or wall-clock times) for the two methods on each fidelity model are not tabulated or plotted in the results section.
- [Methodology section] Notation for the multivariate sensitivity indices (e.g., how the total-effect index is aggregated over the map) should be defined explicitly with reference to the underlying Sobol' decomposition before the numerical demonstrations.
Simulated Author's Rebuttal
We thank the referee for their constructive feedback. We address the major comment point by point below and have made revisions to the manuscript to clarify and strengthen the validation section.
read point-by-point responses
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Referee: [§5] §5 (model reduction and validation): The claim that uncertainty estimates from the full and reduced models confirm the validity of simplification guided by multivariate GSA is load-bearing for the central result. However, it is not clear whether the compared quantities include pointwise variance fields, quantile maps, or distributional distances across the torque-speed plane, or are limited to scalar summaries such as total output variance or mean efficiency. If the latter, this does not fully substantiate preservation of the spatial structure and operating-point dependence of the efficiency map uncertainty.
Authors: We appreciate the referee's comment highlighting the importance of specifying the uncertainty quantities used for validation. In the original submission, the comparisons between full and reduced models were based on scalar summaries, including total output variance and mean efficiency. We agree that this alone does not fully address the spatial structure. In the revised manuscript, we have expanded Section 5 to include pointwise variance fields and quantile maps across the torque-speed plane. New figures have been added to show these comparisons, demonstrating that the reduced model preserves the operating-point dependence of the uncertainty estimates. We believe this addresses the concern and strengthens the central result. revision: yes
Circularity Check
No significant circularity; derivation is self-contained
full rationale
The paper applies standard multivariate global sensitivity analysis (via Monte Carlo or polynomial chaos) to obtain per-parameter indices over the full efficiency map, ranks parameters, fixes non-influential ones to nominal values, and then independently validates the reduced model by comparing its uncertainty estimates against the full model. No step reduces a claimed prediction or result to its own inputs by construction, no load-bearing uniqueness theorem or ansatz is imported via self-citation, and the validation comparison is presented as an external check rather than a definitional tautology. The central claim therefore rests on the independent numerical evidence of the sensitivity indices and the subsequent uncertainty comparison.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Variance-based (Sobol') sensitivity analysis can be meaningfully extended from scalar to multivariate outputs such as efficiency maps
- domain assumption Fixing non-influential parameters to nominal values does not materially alter the uncertainty quantification of the efficiency maps
Lean theorems connected to this paper
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IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
multivariate sensitivity analysis provides a single sensitivity index per parameter... Gn = tr(Cn)/tr(C)
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
K. Heineke, P. Kampshoff, and T. M ¨oller, “Spotlight on mobility trends,” McKinsey & Company, 2024
work page 2024
-
[2]
Traction motors for electric vehicles: Maximization of mechanical efficiency–a review,
M. Gobbi, A. Sattar, R. Palazzetti, and G. Mastinu, “Traction motors for electric vehicles: Maximization of mechanical efficiency–a review,” Applied Energy, vol. 357, p. 122496, 2024
work page 2024
-
[3]
Effi- ciency maps of electrical machines: A tutorial review,
E. Roshandel, A. Mahmoudi, S. Kahourzade, and W. L. Soong, “Effi- ciency maps of electrical machines: A tutorial review,”IEEE Transac- tions on Industry Applications, vol. 59, no. 2, pp. 1263–1272, 2022
work page 2022
-
[4]
P. K. Dhakal, K. Heidarikani, R. Seebacher, and A. Muetze, “A com- parative study on drive cycle performance of laboratory PMSMs using efficiency maps and time-stepping approaches,”Energies, vol. 18, no. 21, p. 5802, 2025
work page 2025
-
[5]
R. Ramarotafika, A. Benabou, and S. Clenet, “Stochastic modeling of soft magnetic properties of electrical steels: Application to stators of electrical machines,”IEEE Transactions on Magnetics, vol. 48, no. 10, pp. 2573–2584, 2012. 8
work page 2012
-
[6]
Stochastic post-processing calculation of iron losses–application to a PMSM,
M. Fratila, R. Ramarotafika, A. Benabou, S. Cl ´enet, and A. Tounzi, “Stochastic post-processing calculation of iron losses–application to a PMSM,”COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 32, no. 4, pp. 1383–1392, 2013
work page 2013
-
[7]
Uncertainty quantification in computational electromagnet- ics: The stochastic approach,
S. Clenet, “Uncertainty quantification in computational electromagnet- ics: The stochastic approach,”International Compumag Society Newslet- ters, vol. 20, no. 1, pp. 2–12, 2013
work page 2013
-
[8]
P. Offermann, H. Mac, T. T. Nguyen, S. Cl ´enet, H. De Gersem, and K. Hameyer, “Uncertainty quantification and sensitivity analysis in electrical machines with stochastically varying machine parameters,” IEEE Transactions on Magnetics, vol. 51, no. 3, pp. 1–4, 2015
work page 2015
-
[9]
Z. Bontinck, H. De Gersem, and S. Sch ¨ops, “Response surface models for the uncertainty quantification of eccentric permanent magnet syn- chronous machines,”IEEE Transactions on Magnetics, vol. 52, no. 3, pp. 1–4, 2015
work page 2015
-
[10]
A. Belahcen, P. Rasilo, T.-T. Nguyen, and S. Cl ´enet, “Uncertainty propagation of iron loss from characterization measurements to compu- tation of electrical machines,”COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 34, no. 3, pp. 624–636, 2015
work page 2015
-
[11]
S. Liu, H. Mac, S. Clenet, T. Coorevits, and J.-C. Mipo, “Study of the influence of the fabrication process imperfections on the performance of a claw pole synchronous machine using a stochastic approach,”IEEE Transactions on Magnetics, vol. 52, no. 3, pp. 1–4, 2015
work page 2015
-
[12]
A. Galetzka, Z. Bontinck, U. R ¨omer, and S. Sch¨ops, “A multilevel Monte Carlo method for high-dimensional uncertainty quantification of low- frequency electromagnetic devices,”IEEE Transactions on Magnetics, vol. 55, no. 8, pp. 1–12, 2019
work page 2019
-
[13]
A. Beltran-Pulido, D. Aliprantis, I. Bilionis, A. R. Munoz, F. Leonardi, and S. M. Avery, “Uncertainty quantification and sensitivity analysis in a nonlinear finite-element model of a permanent magnet synchronous machine,”IEEE Transactions on Energy Conversion, vol. 35, no. 4, pp. 2152–2161, 2020
work page 2020
-
[14]
Robust design optimization of electrical machines: Multi-objective approach,
G. Lei, G. Bramerdorfer, B. Ma, Y . Guo, and J. Zhu, “Robust design optimization of electrical machines: Multi-objective approach,”IEEE Transactions on Energy Conversion, vol. 36, no. 1, pp. 390–401, 2020
work page 2020
-
[15]
Y . Yang, C. Zhang, G. Bramerdorfer, N. Bianchi, J. Qu, J. Zhao, and S. Zhang, “A computationally efficient surrogate model based robust optimization for permanent magnet synchronous machines,”IEEE Transactions on Energy Conversion, vol. 37, no. 3, pp. 1520–1532, 2022
work page 2022
-
[16]
H. Liu, X. Jin, N. Bianchi, G. Bramerdorfer, P. Hu, C. Zhang, and Y . Yang, “A permanent magnet assembling approach to mitigate the cogging torque for permanent magnet machines considering manufac- turing uncertainties,”Energies, vol. 15, no. 6, p. 2154, 2022
work page 2022
-
[17]
D. Liang, Z.-Q. Zhu, P. Taras, R. Nilifard, Z. Azar, and N. Madani, “Sensitivity analysis and uncertainty quantification of thermal behavior for permanent magnet synchronous machines,”IEEE Access, vol. 12, pp. 65 386–65 402, 2024
work page 2024
-
[18]
A. Partovizadeh, S. Sch ¨ops, and D. Loukrezis, “Fourier-enhanced reduced-order surrogate modeling for uncertainty quantification in elec- tric machine design,”Engineering with Computers, vol. 41, pp. 2619– 2639, 2025
work page 2025
-
[19]
A. Saltelli, S. Tarantola, F. Campolongo, and M. Ratto,Sensitivity analysis in practice: a guide to assessing scientific models. Wiley Online Library, 2004, vol. 1
work page 2004
-
[20]
A. Saltelli, M. Ratto, T. Andres, F. Campolongo, J. Cariboni, D. Gatelli, M. Saisana, and S. Tarantola,Global sensitivity analysis: the primer. John Wiley & Sons, 2008
work page 2008
-
[21]
Global sensitivity indices for nonlinear mathematical models and their Monte Carlo estimates,
I. Sobol’, “Global sensitivity indices for nonlinear mathematical models and their Monte Carlo estimates,”Mathematics and Computers in Simulation, vol. 55, no. 1, pp. 271–280, 2001
work page 2001
-
[22]
Multivariate global sensitivity analysis for dynamic crop models,
M. Lamboni, D. Makowski, S. Lehuger, B. Gabrielle, and H. Monod, “Multivariate global sensitivity analysis for dynamic crop models,”Field Crops Research, vol. 113, no. 3, pp. 312–320, 2009
work page 2009
-
[23]
Multivariate sensitivity analysis to measure global contribution of input factors in dynamic models,
M. Lamboni, H. Monod, and D. Makowski, “Multivariate sensitivity analysis to measure global contribution of input factors in dynamic models,”Reliability Engineering & System Safety, vol. 96, no. 4, pp. 450–459, 2011
work page 2011
-
[24]
Sensitivity analysis when model outputs are functions,
K. Campbell, M. D. McKay, and B. J. Williams, “Sensitivity analysis when model outputs are functions,”Reliability Engineering & System Safety, vol. 91, no. 10-11, pp. 1468–1472, 2006
work page 2006
-
[25]
Sensitivity indices for multivariate outputs,
F. Gamboa, A. Janon, T. Klein, and A. Lagnoux, “Sensitivity indices for multivariate outputs,”Comptes Rendus. Math ´ematique, vol. 351, no. 7-8, pp. 307–310, 2013
work page 2013
-
[26]
Analysis of variance designs for model output,
M. J. Jansen, “Analysis of variance designs for model output,”Computer Physics Communications, vol. 117, no. 1-2, pp. 35–43, 1999
work page 1999
-
[27]
A. Saltelli, P. Annoni, I. Azzini, F. Campolongo, M. Ratto, and S. Tarantola, “Variance based sensitivity analysis of model output. design and estimator for the total sensitivity index,”Computer Physics Communications, vol. 181, no. 2, pp. 259–270, 2010
work page 2010
-
[28]
Statistical inference for Sobol pick-freeze Monte Carlo method,
F. Gamboa, A. Janon, T. Klein, A. Lagnoux, and C. Prieur, “Statistical inference for Sobol pick-freeze Monte Carlo method,”Statistics, vol. 50, no. 4, pp. 881–902, 2016
work page 2016
-
[29]
Global sensitivity analysis using polynomial chaos expan- sions,
B. Sudret, “Global sensitivity analysis using polynomial chaos expan- sions,”Reliability Engineering & System Safety, vol. 93, no. 7, pp. 964– 979, 2008
work page 2008
-
[30]
Global sensitivity analysis for multivariate output using polynomial chaos expansion,
O. Garcia-Cabrejo and A. Valocchi, “Global sensitivity analysis for multivariate output using polynomial chaos expansion,”Reliability En- gineering & System Safety, vol. 126, pp. 25–36, 2014
work page 2014
-
[31]
Losses in efficiency maps of electric vehicles: An overview,
E. Roshandel, A. Mahmoudi, S. Kahourzade, A. Yazdani, and G. Shafi- ullah, “Losses in efficiency maps of electric vehicles: An overview,” Energies, vol. 14, no. 22, p. 7805, 2021
work page 2021
-
[32]
Krishnan,Permanent magnet synchronous and brushless DC motor drives
R. Krishnan,Permanent magnet synchronous and brushless DC motor drives. CRC press, 2017
work page 2017
-
[33]
Estimation of PM machine efficiency maps from limited data,
S. Kahourzade, A. Mahmoudi, W. L. Soong, N. Ertugrul, and G. Pelle- grino, “Estimation of PM machine efficiency maps from limited data,” IEEE Transactions on Industry Applications, vol. 56, no. 3, pp. 2612– 2621, 2020
work page 2020
-
[34]
S.-W. Hwang, J.-Y . Ryu, J.-W. Chin, S.-H. Park, D.-K. Kim, and M.-S. Lim, “Coupled electromagnetic-thermal analysis for predicting traction motor characteristics according to electric vehicle driving cycle,”IEEE Transactions on Vehicular Technology, vol. 70, no. 5, pp. 4262–4272, 2021
work page 2021
-
[35]
R. C. Smith,Uncertainty quantification: theory, implementation, and applications. SIAM, 2024
work page 2024
-
[36]
W. Betz, I. Papaioannou, and D. Straub, “Numerical methods for the discretization of random fields by means of the Karhunen–Lo `eve expansion,”Computer Methods in Applied Mechanics and Engineering, vol. 271, pp. 109–129, 2014
work page 2014
-
[37]
Analysis of discreteL 2 projection on polynomial spaces with random evaluations,
G. Migliorati, F. Nobile, E. V on Schwerin, and R. Tempone, “Analysis of discreteL 2 projection on polynomial spaces with random evaluations,” Foundations of Computational Mathematics, vol. 14, no. 3, pp. 419–456, 2014
work page 2014
-
[38]
Sparse polynomial chaos ex- pansions: Literature survey and benchmark,
N. L ¨uthen, S. Marelli, and B. Sudret, “Sparse polynomial chaos ex- pansions: Literature survey and benchmark,”SIAM/ASA Journal on Uncertainty Quantification, vol. 9, no. 2, pp. 593–649, 2021
work page 2021
-
[39]
——, “Automatic selection of basis-adaptive sparse polynomial chaos expansions for engineering applications,”International Journal for Un- certainty Quantification, vol. 12, no. 3, 2022
work page 2022
-
[40]
A. Galetzka, D. Loukrezis, N. Georg, H. De Gersem, and U. R ¨omer, “An hp-adaptive multi-element stochastic collocation method for surrogate modeling with information re-use,”International Journal for Numerical Methods in Engineering, vol. 124, no. 12, pp. 2902–2930, 2023
work page 2023
-
[41]
Dimensionality reduction in surrogate modeling: A review of combined methods,
C. K. J. Hou and K. Behdinan, “Dimensionality reduction in surrogate modeling: A review of combined methods,”Data Science and Engineer- ing, vol. 7, no. 4, pp. 402–427, 2022
work page 2022
-
[42]
A. Muetze, K. Heidarikani, P. K. Dhakal, R. Seebacher, and S. Sch ¨ops, ““CREATOR case”: PMSM and IM electric machine data for validation and benchmarking of simulation and modeling approaches,”COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, 2025
work page 2025
-
[43]
The WLTP: How a new test procedure for cars will affect fuel consumption values in the EU,
P. Mock, J. K ¨uhlwein, U. Tietge, V . Franco, A. Bandivadekar, and J. German, “The WLTP: How a new test procedure for cars will affect fuel consumption values in the EU,”International Council on Clean Transportation, vol. 9, no. 3547, pp. 1–20, 2014
work page 2014
-
[44]
A new design for the implementation of isogeometric anal- ysis in Octave and Matlab: GeoPDEs 3.0,
R. V ´azquez, “A new design for the implementation of isogeometric anal- ysis in Octave and Matlab: GeoPDEs 3.0,”Computers & Mathematics with Applications, vol. 72, no. 3, pp. 523–554, 2016
work page 2016
-
[45]
S. J. Salon,Finite element analysis of electrical machines. Kluwer academic publishers Boston, 1995, vol. 101
work page 1995
-
[46]
Combined parameter and shape optimization of electric machines with isogeometric analysis,
M. Wiesheu, T. Komann, M. Merkel, S. Sch ¨ops, S. Ulbrich, and I. Cortes Garcia, “Combined parameter and shape optimization of electric machines with isogeometric analysis,”Optimization and Engi- neering, vol. 26, no. 2, pp. 1011–1038, 2025
work page 2025
-
[47]
Robust adaptive least squares polynomial chaos expansions in high-frequency applications,
D. Loukrezis, A. Galetzka, and H. De Gersem, “Robust adaptive least squares polynomial chaos expansions in high-frequency applications,” International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, vol. 33, no. 6, p. e2725, 2020
work page 2020
-
[48]
D. Loukrezis, E. Diehl, and H. De Gersem, “Multivariate sensitivity- adaptive polynomial chaos expansion for high-dimensional surrogate modeling and uncertainty quantification,”Applied Mathematical Mod- elling, vol. 137, p. 115746, 2025
work page 2025
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