BRIEFRapid BatteryCharger UsingFuzzy Controller is,moderntechnology whichare being utilizedthese days;based on FuzzyLogic,which is quitedifferent fromclassical Booleanlogic.Fuzzy logic iswidely used inmachine control.
NI-CD BATTERY• using nickel oxide hydroxide and• metallic cadmium as electrodes.The nickel–cadmiumbattery (NiCdbattery or NiCadbattery) is a typeof rechargeablebattery• but without doing any damage tothem.The main objective forthe development ofrapid battery chargerwas to charge the Ni-Cd batteries quickly,
Since the behavior of Ni-Cdbatteries at very highcharging rates was notavailable,• so there was need toobtain them throughexperimentation.• Based on the upper limit ofthe charging current asfixed at 8C i.e. 4A, sincebatteries with capacityC=500 mAh were the targetbatteries.Based on the rigorousexperimentation with the Ni-Cd batteries,• it was observed that thetwo input variables used tocontrol the charging rate(Ct) are absolutetemperature of thebatteries (T) and itstemperature gradient(dT/dt).• Universe of discourse for avariable is defined as itsworking range.
FUZZY CONTROLLERA fuzzy control system orfuzzy controller isa control system basedon fuzzy logic—• a mathematical system thatanalyzes analog input values in termsof logical variables that take oncontinuous values between 0 and 1,• in contrast to classical or digital logic,which operates on discrete values ofeither 1 or 0.
HISTORYFuzzy logic was firstproposed by Lotfi A.Zadeh.He elaborated on hisideas in a 1973paperthat introduced theconcept of "linguisticvariables",which equates to avariable defined as afuzzy set.
Applications:Research anddevelopment is alsocontinuing on fuzzyapplications in software,as opposed to firmware,design,• so-called adaptive "genetic" softwaresystems, with the ultimate goal of building"self-learning" fuzzy-control systems.including fuzzy expertsystems and integrationof fuzzy logicwith neural-network and
MATLAB (Matrix Laboratory) isa numerical computing environmentand fourth-generation programminglanguage.Developed by MathWorks, MATLABallows matrix manipulations,• plotting of functions and data,implementation of algorithms,• creation of user interfaces, and interfacingwith programs written in other languages,• including C, C++, Java,• and Fortran.
Simulink,• developed by MathWorks,• is a data flow graphical programminglanguage tool for modeling,• simulating and analyzingmultidomain dynamic systems.• Its primary interface is a graphical blockdiagramming tool and a customizable set ofblock libraries.Simulink is widely used in controltheory and digital signalprocessing for multidomainsimulation and Model-BasedDesign.
BASICS OF FUZZY CONTROLLER• A Fuzzifier, which converts inputdata into suitable linguisticvalues;• a fuzzy rule base, which consistsof a database with the necessarylinguistic definitions and thecontrol rule set;• a fuzzy inference engine whichsimulating a human decisionprocess, that infers the fuzzycontrol action from theknowledge of the control rulesand finally linguistic variabledefinitions;• a Defuzzifier, which yields anonfuzzy control action from aninferred fuzzy control action.
MembershipFunctionsFuzzy sets must be definedfor each input and outputvariable.As shown in Figure , fourfuzzy Subsets (ZERO, SMALL,MEDUM, HIGH) have beenchosen for charge currentwhile only two fuzzy subsets(SMALL, HIGH),• have been selectedfor the Batterytemperature andvoltage changes inorder to smooth thecontrol action.
This & Above Figures are the Membership Functions of Rapid BatteryCharger.
The first step in thefuzzy controllerdefinition is toselect input andoutput variables.Block diagram ofthe fuzzy controllerstructure show thatwe have two inputvariable (batterytemperature andoutput voltage)While the onlyoutput variable ischarge current as anexternal signal toswitch duty-cycle.Fuzzy controller issimulated in fuzzytoolbox of MATLABsoftware.
SIMULATIONSTEPSMATLAB simulationtoolbox is stronggraphical softwarefor analyzing ofcontrol systems.The system containsthree importantblocks, fuzzycontroller,BUCK converter andthe battery.The basic scheme ofa general-purposefuzzy controlledbattery charger isshown in Figure.
Derivation Of Control RulesFuzzy control rules areobtained from the analysisof the system behavior.In their formulation it mustbe considered that usingdifferent control lawsdepending on theoperating conditions cangreatly improve the batterycharger performances.The improvedperformances are thedynamic response androbustness.
voltageerrorvoltagescopevoltagef(u)temperaturetempsetpointtempscopetemperrortempf(u)VoltageTo Workspace 1outTo WorkspaceinMux 5MuxMux 4MuxMux 3MuxMux2MuxFuzzy LogicControllerDemuxDemuxsetpointFig. Simulation of Rapid Battery Charger using FCS
Conclusion:As a final result, it is shownthat fuzzy controller providesa safe and stable chargeprocess with optimized timeand acceptable temperaturevariations.This fast and safe method isused to charge a set of Ni-Cdbatteries and the charge timeis 100 min and temperatureduring charge process doesntexceed from 40°CThis system can be used tocharge batteries with differentcharacteristics because of itsindependence to statevariables and system model
Future ScopeThe suggested framework canbe extended to increase theflexibility of the searchby incorporating additionalparameters so that the searchfor optimal solution could beexecuted in terms of number ofmembership functions for eachvariable,the type of membershipfunction and the number ofiterations &possibly trying variants of PSOalgorithm for identifying fuzzysystems with an objective toimprove their performancefurther.