Design of a single-input fuzzy logic controller and its properties

✍ Scribed by Byung-Jae Choi; Seong-Woo Kwak; Byung Kook Kim

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 558 KB
• Volume: 106
• Category: Article
• ISSN: 0165-0114
• DOI: 10.1016/s0165-0114(97)00283-2

✦ Synopsis

We suggest a simple but powerful FLC (Fuzzy Logic Controller) design method using a single fuzzy input variable, which is equivalent to the pseudo sliding mode controller. Input variables of conventional FLCs are mostly the error e and the change-of-error ~ regardless of the complexity of controlled plants. A rule table is then constructed in a two-dimensional input space. The output of fuzzy inference is applied to the plant as the control input u or the change of control input Au. This scheme came from concepts of linear PD (proportional-derivative) and PI (proportional-integral) controllers. We found that rule tables of most FLCs have skew-symmetry property, and the absolute magnitude of the control input [u] or [Au] is proportional to the distance from its main diagonal line in the normalized input space. Considering these facts, we derive a new variable called the signed distance, which is a sole fuzzy input variable in our simple FLC called single-input FLC (S-FLC). The S-FLC has many advantages: The total number of rules is greatly reduced compared to two-dimensional FLCs, and hence, generations and tuning of control rules are easy. Control performance is nearly the same as that of conventional FLCs. We also show that this S-FLC is equivalent to the pseudo SMC (sliding mode controller), and hence, the stability is guaranteed using the Lyapunov stability. The performance of S-FLC is revealed via computer simulations using a nonlinear plant. (~) 1999 Elsevier Science B.V. All rights reserved.