Search

An active mass driver has been designed for installation on the upper observation deck of the 310 m Nanjing TV transmission tower in China in order to reduce the acceleration response under strong wind gusts. In this paper, the linear quadratic Gaussian (LQG), [H.sup.[infinity]], and continuous sliding mode control (CSMC) strategies have been applied to the active mass driver system based on the acceleration feedbacks. Emphasis is placed on the practical applications of LQG, [H.sup.[infinity]], and CSMC controllers, including limitations on the actuator peak force and stroke, the limited number of sensors, and noise pollution. Further, a method for modulating the control effort for the CSMC controller is proposed in this paper to satisfy the practical constraints on the actuator. A state reduced-order system has been established to design the dynamic output feedback controllers. The wind loads acting on the tower are defined by the Davenport cross-power spectral density matrix. Simulation results demonstrate that, when designed appropriately, the LQG, [H.sup.[infinity]], and CSMC control strategies are suitable for full-scale implementations of the active mass driver, and their control performances are quite remarkable.

This study develops fuzzy control that is designed with sliding modes to achieve stability of the fuzzy controller. Fuzzy control is formulated in the form of variable structure system (VSS) control. In contrast to previous works in which Lyapunov functions are used to examine the stability, the current study investigates the stability of fuzzy control from the viewpoints of differential geometric methods and the sliding mode theory. Best values for parameters in fuzzy control rules are determined with the aid of sliding modes. In order to improve control performance, a tuning algorithm is executed to adjust parameters for dealing with uncertainties and disturbances. Both computer simulations and experiments with regard to an inverted pendulum hinged to a rotating disk are carried out to validate the proposed method. This apparatus can to some extent represent cornering motion of a motorcycle on which a rider leans to maintain stability. Effects of rider's leaning angle on both stability and handling control are examined according to Bode plots.

Recently, [H.sub.[infinity]] and sliding mode control methods have been investigated for applications to active/hybrid control of seismically excited structures. Numerical simulation results indicate that both control methods are quite promising for civil engineering applications. In the present paper, shaking table experimental tests were conducted to verify the [H.sub.[infinity]] and continuous sliding mode control methods. The test structure used was the three-story 1/4-scaled building model, equipped with an active tendon control system, which was used extensively at the State University of New York, Buffalo. Different earthquake records were used as the input excitations, including the El Centro, Pacoima, Hachinohe, and Taft. Both the full-state feedback controllers and the static output feedback controllers were used. Experimental data correlate satisfactorily with numerical simulation results. Extensive experimental results demonstrate that the [H.sub.[infinity]] and continuous sliding mode control methods, in particular the static output feedback controllers using only the measured information from a limited number of sensors installed at strategic locations without an observer, are quite promising for practical implementations of active control systems on seismically excited structures.