Mr. Chi-Lun Ng Profile

Chi-Lun Ng

at Hong Kong Polytechnic Univ

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Proceedings Article | 29 July 2004 Paper

Seismic response control of a complex structure using semi-active friction dampers

Chi-Lun Ng, You-Lin Xu

Proceedings Volume 5391, (2004) https://doi.org/10.1117/12.540901

KEYWORDS: Buildings, Control systems, Earthquakes, Electroluminescence, Logic, Feedback control, Matrices, Actuators, Control systems design, Connectors

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Mitigating seismic responses of adjacent buildings by using control devices linked the two buildings has been recognized as a feasible alternative control scheme in past decade. A numbers of research studies have been undertaken in revealing and comparing the control capability among passive, active and semi-active control strategies employed in the coupled building system. The general interest and intention for the coupling control approach are mainly placed on the adjacent high-rise structures, and the LQ control algorithm relying on feedback with multiple measurement points is also the major design preference. This paper will focus on evaluating the effectiveness of controllable friction dampers as coupling devices that are implemented with semi-active control strategy based on local response feedback for a coupled podium structure and medium-rise building system. The effect of the height, mass and stiffness of two semi-actively controlled structures is one of the investigations. A comparison on control performance by a proposed semi-active control strategy with passive and clipped optimal control strategy is also presented. It is shown that control strategy with local response feedback can provide increased control performance over the passive strategy, and it is also of similar efficiency compared to the clipped optimal control strategy.

Proceedings Article | 29 July 2004 Paper

Hybrid control of microvibration of high-tech facility under horizontal and vertical ground motion

You-Lin Xu, An-Xin Guo, Hui Li, Chi-Lun Ng

Proceedings Volume 5391, (2004) https://doi.org/10.1117/12.540900

KEYWORDS: Actuators, Roads, Picosecond phenomena, Control systems, Motion models, Finite element methods, Feedback control, Numerical simulations, Matrices, Motion analysis

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Hybrid control platform is investigated in this paper for mitigating microvibration of a batch of high tech equipment installed in a high tech facility (building) subject to nearby road vehicle-induced horizontal and vertical ground motions. Hybrid control platform, on which high tech equipment is installed, is mounted on the building floor through a series of passive mounts and controlled by hydraulic actuators in both horizontal and vertical directions. The hybrid control platform is taken as an elastic body with significant bending modes of vibration, and a sub-optimal control algorithm is used to manipulate the hydraulic actuators with the actuator dynamics included. The governing equations of motion of the coupled platform-building system are established in the absolute coordinate to facilitate the feedback control and performance evaluation of the platform. The horizontal and vertical ground motions at the base of the building induced by nearby moving road vehicles are assumed to be random and statistically stationary processes. A typical three-story high tech building is selected as a case study. The case study shows that the ground motion and vibration of the high tech building are higher in the vertical direction than in the horizontal direction. The use of hybrid control platform can effectively reduce both horizontal and vertical microvibrations of a vast quantity of high tech equipment to the level satisfying the most stringent microscale velocity requirement specified in the BBN criteria.

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