(A) study on design of fuzzy logic controller using time delay

Abstract

In this thesis, we propose a new approach to design the fuzzy logic controller, which is based on time-delay information such as time-delay control scheme and a time-delay reward. The proposed new design methods are applied to system stability and multi-objective control problems, depending on the different type of time-delay information, respectively, and show their effectiveness compared wth the previous research results. For a problem statement and an initial research result on stability problem, HRIV (Hybrid Rule Interval Variation) method is presented, as a means of stabilizing a class of fuzzy control-based nonlinear systems. The HRIV method consists of two modes: I-mode (Minimum Approximation Error-based control) and R-mode (Rule Interval Variation-based control). In I-mode, sliding mode control is used to compensate for the minimum approximation error caused by heuristic characteristics of fuzzy logic control. In R-mode, RIV (Rule Interval Variation) method reduces the interval lengths of rules as the states converge to an equilibrium point. The HRIV method considers the analytic upper bound of the minimum approximation error and reduces its effect in the control input, which is considered to be advantageous compared with the previous results. To show effectiveness of the proposed method, a simulation experiment is conducted to stabilize a simple nonlinear system and a modified inverted pendulum system. Design of Mamdani-type FLC (Fuzzy Logic Control) heavily depends on a priori knowledge while TSK-type FLC requires determination of a common matrix `` P `` for stability. On the other hand, the TDC (Time Delay Control) method shows guaranteed stability depending on a sufficiently large time span and a sufficiently small time-delay. In this paper, the TDC scheme is combined with FLC in two different ways to resolve those disadvantages of FLC and TDC schemes. In case of Mamdani-type TDFLC, SMC (Sliding Mode Control) and ADC (Adaptive Control) are incorpora...