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In this paper the problem of controlling a bar supporting, at one end a pointer and hinged, at the other end, to a structural system vibrating under any exteral excitation is investigated. The problem is to maintain the pointer toward the target with a prescribed tolerance. | Vietnam Journal of Mechanics, NCST of Vietnam Vol. 23, 2001, No 1 (17 - 24) CONTROL OF A POINTER LOCATED ON A VIBRATING SYSTEM 1 L. FARAVELI 1 , NGUYEN DONG ANH 2 Dept. of Structural Mechanics University of Pavia, Italy 2 Institute of Mechanics, NCST of Vietnam F. CASCIATI , 1 ABSTRACT. In this paper the problem of controlling a bar supporting, at one end a pointer and hinged, at the other end, to a structural system vibrating under any exter~al excitation is investigated. The problem is to maintain the pointer toward the target with a prescribed tolerance. Emphasis is put on the uncertainty, which characterises the problem and a simple fuzzy controller approach is ciiscussed. Some numerical simulations are presented. Keywords. Active control, fuzzy control, linear electromagnetic motor, pointer. 1. Introduction The control of a structure can pursue two different objectives. [Cassiati et al. (1998) , Kobori et al. (1999)]: - To reduce the response to extreme external excitation in order to reduce the stresses and hence to increase the system reliability; - To respect service ability constraints even when external disturbances would · prevent from it. This paper approaches the latter problem in which the control of a bar supporting, at one end, a pointer and hinged, at the other end~ to a structural system vibrating under any external excitation is considered. The problem is to maintain the pointer toward the target with a prescribed tolerance. Further, since fuzzy control is a recognised alternative to standard control tools allowing the resolution of imprecise or uncertain information, [Casciati and Faravelli (1991)], a fuzzy-chip controller is introduced in order to incorporate uncertainty and to ensure robustness. 2. Problem formulation With reference to figure 1, consider the bar 00 1 of length L and mass m. It is supported by a hinge 0 while PQ = u(t) is regarded as a control distance. The control action is provided by a linear electromagnetic engine. .
