SUMMARYAn analytical model is developed to evaluate performance characteristics of unidirectional seismic simulators (shaking tables). The validity of the model is verified with experimental measurements of the frequency response of the shaking table at the Catholic University of Peru.Interaction effects between shaking table and structure are first studied by analysing the response of a two DOF (degree of freedom) oscillator with mechanical properties representative of the actuator-table-structure system. A single DOF viscoelastic oscillator representing the structural test specimen is then included in the analytical model of the seismic simulator, and the behaviour of the combined system is evaluated, in the frequency domain, in terms of response stability and accuracy of reproduction of the command signal. Numerical simulations of system response under different load conditions are subsequently performed in order to study the influence of shaking table and test structure characteristics on the interaction phenomenon.The results obtained explain some of the performance degradation observed in seismic simulation tests involving very heavy structures and provide guidelines for the design of more reliable shaking table systems.

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ResumenEste trabajo presenta la validación de un sistema de control adaptativo por modelo de referencia con ley de control proporcional-derivativo MRAC-PD, que es usado como sistema de control de una mesa vibratoria de dos ejes. La mesa controlada se basa en un mecanismo biela-manivela utilizada para reproducir movimientos sísmicos sobre modelos a escala de estructuras civiles. El controlador MRAC-PD se diseñó en base a la regla MIT de optimización como mecanismo de adaptación de los parámetros proporcional y derivativo. Los resultados fueron mejores que los obtenidos con controladores MRAC con uno y dos parámetros de adaptación proporcionales, controladores adaptativos con predictor Smith para compensar el error introducido por los retardos de los sistemas, y un controlador Fuzzy. La validación de los sistemas de control se implementa en una plataforma hardware de 32 bits de Microchip y se accede de forma remota a través de la red nacional RENATA. Palabras clave: control adaptativo, controlador MRAC-PD, predictor Smith, mesa vibratoria, biela-manivela Model Reference Adaptive Controller for Biaxial Shaking Table Based on the Slider-Crank Mechanism AbstractThis work shows the validation of a model reference adaptive controller with proportional-derivative control law MRAC-PD. This model is designed as a control system of a shaking table with two axis, based on a slider-crank mechanism, and it is used to generate earthquakes on scale models of civilian structures. The MRAC-PD design was based on the MIT optimization rule as adaptation mechanism for the proportional and derivative parameters. The results are better than those obtained with MRAC controllers with one and two proportional adaptation parameters, adaptive controllers with Smith predictor to compensate the delay errors introduced by the systems and a Fuzzy controller. The validation of the control systems are implemented on a 32 bits hardware platform from Microchip and it is remotely accessed through the national RENATA network.