Publication: IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences Publication Date: 2009/04/01 Vol. E92-ANo. 4pp. 952-957 Type of Manuscript: Special Section PAPER (Special Section on Advanced Technologies Emerging Mainly from the 21st Workshop on Circuits and Systems in Karuizawa) Category: Keyword: fuzzy control, L2 space, variation problem, feedback control, approximate reasoning,