Bj. Choi et al., FUZZY LOGIC-BASED TUNING OF THE BOUNDARY-LAYER THICKNESS OF THE VARIABLE-STRUCTURE CONTROLLER, Intelligent automation and soft computing, 4(3), 1998, pp. 241-251
The variable structure control (VSC) is a simple and powerful nonlinea
r controller, but it leads to a high frequency chattering on the contr
ol input. To decrease the chattering phenomenon of the VSC, a boundary
layer is commonly introduced. Then its thickness requires a compromis
e between the steady state error and the chattering amplitude. In this
paper, we propose a new VSC that tunes the boundary layer thickness u
sing the fuzzy logic system. The tuning methods presented are two: One
uses absolute error and its derivative as fuzzy input variables, whic
h decreases the number of tuning rules as compared with using common f
uzzy variables of error and change of error. The other uses only a sin
gle fuzzy variable of a distance. This variable is derived by the prop
erty of two-dimensional rule table which is composed of absolute error
and its derivative. Since the second method uses a single variable fo
r tuning the thickness, the number of tuning rules is greatly decrease
d. Furthermore, we obtain the good tracking performance which is almos
t the same as that of the first method. To ensure the control performa
nce in both cases, we perform computer simulations using an inverted p
endulum as a controlled plant.