Title: Development of Next Generation Structural Engineering Laboratories
Speaker: Prof. Yang ZongYeun (University of British Columbia, Canada)
Time: Friday, Jun 16, 2017, 10:00 a.m.
Venue: 516, LiWu Technology Building, Wushan Campus
Contents: The knowledge of earthquake engineering is largely gained through experimental testing. The most direct method to recreate the loading experienced by a structure during an earthquake is via shaking table testing. Conventional shake tables employ linear controllers such as proportional-integral-derivative (PID) or loop shaping to regulate the movement. However, it is difficult to tune a linear controller to achieve accurate and robust tracking of different reference signals under payloads. The challenges are mainly due to the nonlinearity in hydraulic actuator dynamics and specimen behavior. Moreover, tracking a high frequency reference signal using a linear controller tends to cause actuator saturation and instability. In this presentation, a hierarchical control strategy is proposed to develop a high performance shake table. The high-level controller utilizes the Sliding Mode Control (SMC) technique to provide robustness to compensate for model nonlinearity and uncertainties experienced in experimental tests. The performance of the proposed controller is compared with a state-of-the-art loop shaping displacement-based controller. The experimental results show that the proposed hierarchical shake table control system with SMC can provide superior displacement, velocity and acceleration tracking performance and improved robustness against modeling uncertainty and nonlinearities. In addition to shaking table testing, hybrid simulation (HS) is becoming a favorable alternative experimental method to shaking table test. This is particularly useful for the development of novel structural components and systems, where only a small portion of the structure needed to be experimentally tested. Traditionally, HS is displacement-based. Many successful tests have been accomplished. However, such a methodology is not suitable for specimens with high stiffness. In this presentation, a hierarchical displacement-based and force-based control framework for HS is presented. In this framework, a high-level controller generates either the force or displacement commands based on finite element formulation and regulated the force or displacement commend using low-level controller(s). A detailed formulation for the high-level controller is presented.
