Free Vibration Response of a Frame Structural Model Controlled by a Nonlinear Active Mass Driver System

Abstract

Active control devices, such as active mass dampers, are mainly employed for the reduction of wind-induced vibrations in highrise buildings, with the final aim of satisfying vibration serviceability limit state requirements and of meeting appropriate comfort criteria. When such active devices, normally operating under wind loads associated with short return periods, are subjected to seismic events, they can experience large amplitude vibrations and exceed stroke limits. This may lead to a reduced performance of the control system that can even worsen the performance of the whole structure. In this paper, a nonlinear control strategy based on a modified direct velocity feedback algorithm is proposed for handling stroke limits of an active mass driver (AMD) system. In particular, a suitable nonlinear braking term proportional to the relative AMD velocity is included in the control law in order to slowdown the device in the proximity of the stroke limits. Experimental and numerical free vibration tests are carried out on a scaled-down five-story frame structure equipped with an AMD to demonstrate the effectiveness of the proposed control strategy.

Seismic Behavior of Turbine-Generator Foundation under Strong Earthquake Action in Different Directions

“…In the pseudodynamic test method, the central difference method is used to solve the discrete time dynamic equations [12], and the structural displacement d i+1 of time t i+1 is given by the following equation: e damping ratio was selected as 0.05 [13], according to the code [11]. e foundation was regarded as a single degree of freedom model with the equivalent mass method [14]. e model equivalent mass was 17,812 kg.…”

A Review on Adaptive Methods for Structural Control

“…Yamamoto e Sone [122] proposed to modulate the feedback obtained by pole assignment method by a coefficient representing the activity of the AMD and depending on the stroke displacement and the time derivative of the first modal displacement estimated by a Kalman filter. Venanzi et al [123,124] recently proposed an enhanced non-linear damping (ENLD) approach for AMDs, capable of solving the issue of a limited stroke extension and force saturation. The ENLD method is a skyhook control algorithm complemented by a non-linear breaking term that becomes effective in the vicinity of the stroke limit and a modulation term that is activated close to the control force limit.…”

An enhanced nonlinear damping approach accounting for system constraints in active mass dampers

“…The nonlinear damping approach (NLD), originally proposed in [25], is a control strategy capable of avoiding stroke limits crossing of AMD systems. The NLD approach prevents the movable mass from attaining its limits by slowing down its motion in the vicinity of the stroke stop.…”

“…The shear-type assumption is adopted to model the frame as a simplified dynamic system having 5 degrees of freedom, one for each floor. The numerical model represents a frame adopted for laboratory testing whose mass and stiffness coefficients were obtained from model updating using the modal characteristics obtained by structural identification [25]. Stiffness and mass parameters of the frame are summarized in Table 1, while modal parameters are summarized in Table 2.…”

“…Furthermore, most procedures require an estimation of the state through the implementation of a state observer that represents an additional complication and produces time delay. To overcome these drawbacks, the authors recently proposed a nonlinear damping (NLD) approach [25] for AMDs, capable of solving the issue of a limited stroke extension. The main feature of the NLD method is related to the ease of its implementation, owing to its collocated nature.…”