%

%  readme.m  for the fuzzy logic matlab package by Tom Ahola

%

%    The fuzzy matlab functions are copyright (C) Tom Ahola 1995

%    You may use them freely for educational and personal purposes

%

%    The idea behind the fuzzy controlled temperature sensor

%    is from an article by Lei Wang and Hans Volker

%

%    Type help followed by the function name on the

%    matlab command line to get instructions on how to

%    use the functions.

%

%              Tom Ahola

%                  Helsinki University of Technology

%                  Metrology Research Institute

%                  E-mail:  tom.ahola@hut.fi

%                  WWW:     http://www.hut.fi/~tahola/

%

type readme;

return;



%============ the fuzzy matlab functions ================



% the fuzzy matlab functions



mf=mmembr(centr,width);         %   Create a triangular fuzzy set

mf=mmembr2(a,b,trans);          %   Create a trapezoidal fuzzy set

mf=mmembr3(a,b,transa,transb);  %   Create a trapezoidal fuzzy set

memplot(mf);                    %   plots membership function graph



c=ismembr(mf,x);                %   The degree of membership of x in mf

mf=hatfunc(mf1,hat);            %   Limit membership function by hat value



mf=fuzzyadd(mf1,mf2);           %   Add two fuzzy sets together

mf=fuzzyand(mf1,mf2);           %   Fuzzy AND operation (minimum)

mf=fuzzyor(mf1,mf2);            %   Fuzzy OR operation (maximum)



c=centroid(mf);                 %   Returns center of gravity of fuzzy set





%============ an example fuzzy controller ================



% create fuzzy sets



tlow=mmembr2(-100,20,10);  % temperature low

thigh=mmembr2(20,200,10);  % temperature high

dtneg=mmembr2(-100,0,1);   % temperature change negative

dtlow=mmembr2(0.5,2,1);    % temperature change low

dthigh=mmembr2(2,100,1);   % temperature change high

izero=mmembr(0,5);         % heater current zero

ilow=mmembr2(5,10,5);      % heater current low

ihigh=mmembr2(10,40,5);    % heater current high



% fuzzy control algorith



% TS=current temperature, temps=previous temperature

rule1=hatfunc(ihigh,min([ismembr(tlow,TS),ismembr(dthigh,TS-temps)]));

rule2=hatfunc(ilow,min([ismembr(tlow,TS),ismembr(dtlow,TS-temps)]));

rule3=hatfunc(ilow,min([ismembr(thigh,TS),ismembr(dthigh,TS-temps)]));

rule4=hatfunc(ilow,min([ismembr(thigh,TS),ismembr(dtlow,TS-temps)]));

rule5=hatfunc(izero,ismembr(dtneg,TS-temps));

result=fuzzyadd(rule1,rule2);

result=fuzzyadd(result,rule3);

result=fuzzyadd(result,rule4);

result=fuzzyadd(result,rule5);

heat=centroid(result);

if (heat<0) heat=0; end;





% the rules in the controller are:



  1 - IF temperature is low AND temperature change is high

      THEN current is high



  2 - IF temperature is low AND temperature change is low

      THEN current is low



  3 - IF temperature is high AND temperature change is high

      THEN current is low



  4 - IF temperature is high AND temperature change is low

      THEN current is low



  5 - IF temperature change is negative

      THEN current is zero





% end of readme.m