State and parameter estimation of lithium-ion battery by Kreisselmeier-type adaptive observer for fractional calculus system

Lithium-ion battery's complicated dynamics can be described as simple equivalent circuit (Randles circuit) containing Warburg impedance, which can be expressed as the fractional calculus. In order to control or identify lithium-ion battery system described as fractional order system containing unknown variable parameters, online parameter estimate mechanism for the coefficients of transfer function containing fractional order (like s^0.5) must be needed. In this paper, we designed the Kreisselmeier-type adaptive observer for the linear time-variable fractional order system. Then, we applied the proposed observer to the lithium-ion battery modeled by Randles circuit under semi-infinite linear diffusion, and confirm the effectiveness of our observer by numerical simulation.