Estimation of battery state of charge using H∞ observer

Since an autonomous mobile robot often works with various tasks in different environments, the current of battery onboard is time-varying, hence the battery internal resistance is variable. This paper presents an estimation method for battery State of Charge (SOC) based on an H∞ observer to deal with the effect of the modeling errors caused by the variation of the internal resistance. The observer gain is obtained by solving a linear matrix inequality. The convergence and existence of the H∞ observer are analyzed. The effectiveness of the proposed method is verified on a prototype of a battery powered robot prototype for high voltage power transmission line inspection. Experimental results show that the proposed method can provide accurate SOC estimation.