From Data $H(jω_i)$ to Balanced Truncation Family: A Projection-based Non-intrusive Approach
Umair Zulfiqar
TL;DR
The paper tackles data-driven model order reduction for the balanced truncation (BT) family by developing a projection-based framework that uses transfer function samples on the imaginary axis to implicitly approximate Gramians. It introduces rational interpolation with pole/zero/shifted-pole placement and leverages it to construct non-intrusive, data-driven realizations for standard BT and eight generalizations (including FLBT, TLBT, SWBT, LQG BT, H∞ BT, PRBT, BRBT, and BST) without requiring spectral factor measurements. The key contributions are (i) projection-based Gramian factorization $\mathcal{P} \approx (V\tilde{Z}_p)(V\tilde{Z}_p)^*$ and $\mathcal{Q} \approx (W\tilde{Z}_q)(W\tilde{Z}_q)^*$, (ii) a unified shifted-pole/zero-placement scheme that yields ROMs with prescribed spectral properties, and (iii) numerical evidence on a high-order RLC model showing data-driven ROMs achieve accuracy comparable to intrusive BT across a range of orders and variants, with dominant Hankel-like singular values well captured. This framework eliminates the need for spectral-factor data and explicit Lyapunov/Riccati solves in the reduced models, enabling practical, non-intrusive MOR in control and systems applications.
Abstract
This paper presents data-driven implementations of balanced truncation and several of its generalizations that rely exclusively on transfer function samples on the imaginary axis. Rather than implicitly approximating the Gramians via numerical quadrature, the proposed approach approximates them implicitly through projection. This enables multiple members of the balanced truncation family to be implemented non-intrusively using practically measurable data, without requiring spectral factorizations. Using this projection-based framework, data-driven implementations are developed for standard balanced truncation, frequency-limited balanced truncation, time-limited balanced truncation, self-weighted balanced truncation, LQG balanced truncation, H-infinity balanced truncation, positive-real balanced truncation, bounded-real balanced truncation, and stochastic balanced truncation. Numerical results demonstrate that the proposed non-intrusive implementations achieve performance comparable to their intrusive counterparts and accurately capture the dominant Hankel singular values.
