New Methods Using Nonlinear Observers to Estimate the State of Charge for a Battery System
Portable electronic devices are limited by battery life which is determined directly by the state of charge (SOC). By estimating the SOC an accurate charging scheme can be designed and the battery life can possibly be extended. Recently, some new designs of nonlinear observers can reduce computational complexity in order to be applied for -real-time estimation. In this thesis we will construct nonlinear observers that take advantage of the non-linearity of the relationship between SOC and the open circuit voltage (OCV) measured at the battery terminals. We show that the estimated states asymptotically converge to the actual states even under the nonlinear relationship between the SOC and OCV. We also show that a canonical linear observer that attempts to estimates the real states of the system. We will also formulate the LMI of the state space system such that a feasible solution will produce a gain to guarantee the observer asymptotically converges to the actual states in a finite time.