Stable-by-Design Neural Network-Based LPV State-Space Models for System Identification
This addresses the challenge of maintaining stability in nonlinear system identification for control applications, representing an incremental improvement with stability constraints.
The paper tackled the problem of accurately modeling nonlinear systems for control by proposing a stable-by-design neural network-based LPV state-space model that learns latent states and scheduling variables from data, with results showing it matches or surpasses classical and recent methods on benchmark systems.
Accurate modeling of nonlinear systems is essential for reliable control, yet conventional identification methods often struggle to capture latent dynamics while maintaining stability. We propose a \textit{stable-by-design LPV neural network-based state-space} (NN-SS) model that simultaneously learns latent states and internal scheduling variables directly from data. The state-transition matrix, generated by a neural network using the learned scheduling variables, is guaranteed to be stable through a Schur-based parameterization. The architecture combines an encoder for initial state estimation with a state-space representer network that constructs the full set of scheduling-dependent system matrices. For training the NN-SS, we develop a framework that integrates multi-step prediction losses with a state-consistency regularization term, ensuring robustness against drift and improving long-horizon prediction accuracy. The proposed NN-SS is evaluated on benchmark nonlinear systems, and the results demonstrate that the model consistently matches or surpasses classical subspace identification methods and recent gradient-based approaches. These findings highlight the potential of stability-constrained neural LPV identification as a scalable and reliable framework for modeling complex nonlinear systems.