IEC 61131-7-2000 pdf free download – Programmable controllers – Part 7: Fuzzy control programming.
ln this example,Valve_Control_1 is a user defined Function Block Instance of the FunctionBlock Type Fuzzy_FB. The Function Block Type Fuzzy_FB may be programmed in FuzzyControl Language FCL according to clause 5.The Function Block Fuzzy_FB is used here in aprogram or a Function Block which is represented in the graphical language FBD (FunctionBlock Diagram) of IEC 61131-3.
5 Fuzzy Control Language FCL
5.1 Exchange of fuzzy control programs
The definition of the Fuzzy Control Language FCL is based on the definitions of theprogramming languages in lIEC 61131-3. The interaction of the fuzzy control algorithm with itsprogram environment causes it to be “hidden” from the program.The fuzzy control algorithm istherefore externally represented as a Function Block according to lEC 61131-3.The necessaryelements for describing the internal linguistic parts of the fuzzy control Function Block likemembership functions，rules，operators and methods have to be defined according to thisclause.
The language elements of FCL standardize a common representation for data exchangeamong fuzzy control configuration tools of different manufacturers shown in figure 2.Using thiscommon representation，every manufacturer of programmable controllers may keep hishardware， software editors and compilers. The manufacturer has only to implement the datainterface into his specific editor. The customer would be able to exchange fuzzy controlprojects between different manufacturers.
5.2 Fuzzy Control Language elements
Fuzzy control language elements in this subclause are described using examples. The detailed production rule is given in 5.4.
With these language elements, it is possible to describe a function block interface. The function block interface is defined with parameters which are passed into and out of the function block. The data types of these parameters shall be defined according to IEC 61131-3.
Figure 3 shows an example of a Function Block declaration in Structured Text (ST) and Function Block Diagram (FBD) languages.
5.2.2 Fuzzification
The values of the input variables have to be converted into degrees of membership for the membership functions defined on the variable. This conversion is described between the keywords FUZZIFY and END_FUZZIFY.
After the keyword FUZZIFY, the name of a variable which is used for the fuzzification shall be named. This is the name of a previously defined variable in the VAR_INPUT section. This linguistic variable shall be described by one or more linguistic terms . The linguistic terms introduced by the keyword TERM described by membership functions in order to fuzzify the variable. A membership function is a piece-wise linear function. It is defined by a table of points.
With this definition, all simple elements, for example ramp and triangle, may be defined. The points shall be given in ascending order of variable value. The membership function is linear between successive points. The degree of membership for each term is therefore calculated from the crisp input value by the linear interpolation between the two relevant adjacent membership function points. The minimum number of points is two. The maximum number is restricted according to clause 6 conformance classes.
If the value of a linguistic variable is less than the first base point in the look-up table, all values below the first point in the look-up table shall have the same membership degree as defined at the first point. If the value of a linguistic variable is greater than the last base point in the look-up table, all values greater than the last point in the look-up table shall have the same membership degree as defined at the last point.IEC 61131-7 pdf download