Interval State Estimation for Li-Ion Batteries Using Thermally Coupled Equivalent Hydraulic Model

This article investigates an interval (i.e., set-valued) state estimation problem for lithium-ion (Li-ion) battery cells. A thermally coupled equivalent hydraulic model (TEHM) characterizes lithium exchange and thermal phenomena in the electrodes of a battery cell, which is modeled as a nonlinear system with state interval constraints. For this nonlinear system, we propose an iterative zonotope-based method to achieve accurate interval estimation and investigate its convergence. In the proposed method, we adopt a zonotopic DC (ZDC) programming (where DC stands for difference of convex) to handle the nonlinearties, and present a zonotope estimator to manage the interval constraints. We consider an interval hull-based optimization problem to facilitate the zonotope estimator design, which is physically interpretable and can be efficiently solved via linear programming. Finally, results on experimental battery cell data demonstrate that the proposed method can produce accurate interval estimation results.