Fuzzy control of a universal battery charger

Fuzzy control of a Universal Battery Charger is investigated. Effective control of the charging process is complex, due to the exponential relationship between the charging current and the charging time. Classical control algorithms such as PID, PI etc. are difficult to implement in this event, due to nonlinear current-time relationships of rechargeable batteries. Initial peak charging current is estimated depending on the coefficient of discharge of the battery. An intelligent microcontroller based system is developed to sense the charging current and the present charge, after which a fast fuzzy inference mechanism defines the next level of the charging current. Delay time of the switching of the main supply is calculated after the fuzzy inference, and the power switch is switched accordingly. Experimental results and expert knowledge are used for tuning of the membership functions and the rule base of the fuzzy controller