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Efficient State and Parameter Estimation of Nonlinear State-Space Models through Probabilistic Optimal Control
Proceedings of The 8th Annual Learning for Dynamics and Control Conference, PMLR 331:1306-1321, 2026.
Abstract
This work presents a novel representation of the smoothing distribution - the posterior state distribution of a discrete-time dynamical system - through its connection to probabilistic optimal control. The key idea is to represent the posterior as the closed-loop behavior of a synthetic control system governed by an optimal stochastic policy. This formulation enables forward simulation of equally weighted trajectories that capture the statistics of the posterior without the need for backward sampling or importance weighting. We derive a practical algorithm based on probabilistic dynamic programming to compute this policy efficiently, with linear computational complexity in the number of particles. Furthermore, the uniform particle weighting significantly simplifies and accelerates the Expectation–Maximization algorithm, providing substantial benefits for system identification of nonlinear dynamical systems with latent states. The proposed method offers a simple, stable, and scalable alternative to traditional particle smoothers and demonstrates accurate parameter estimation and model learning at significantly reduced computational cost.