Name: Monir Ahmad
Fall II 2018
A comparative study of semi- active control strategies for base isolated buildings
Earthquake is a violent and sudden shock of the earth, which is often caused by two layers of the ground slipping from one another. Earthquakes are measured in accordance with their magnitudes. The earthquakes with higher magnitudes have higher destruction levels. Scientists believe that earthquakes can occur anywhere, anytime, and are unpredictable. The engineering society believes there are no systems that can reduce the magnitude of the earthquakes but they have several techniques that would protect the safety of buildings in earthquakes.
There are several methods used in the control of semi-active control which includes;
(i) ”Maximum energy dissipation algorithm and modulated homogeneous friction algorithm”
The behavior of devices that are semi-active is mostly nonlinear, and as such, one of the major challenges during application of this technology is the appropriate development of control algorithm. A number of algorithms are tested for use with the MR (Magneto rheological Damper), a semi-active control device that’s been innovated and is quite promising to the civil engineering applications. Discussion of each control system takes place after simulation, with results indicating that the control systems’ performance is dependent on the employed algorithm (Dyke and Spencer Jr., 1997).
(i) ”Sliding mode control”
SMC is a nonlinear control method which forces a system slide over a cross-section of the systems’ normal behavior through alteration of the nonlinear systems’ dynamics. The method can switch from one continuous structure to another making the method a variable structure method (Komatsu et al., 2007).
(ii) ”Backstopping control technique and quantitative feedback theory”
Suspension systems are crucial even in vehicles. The suspension systems are designed to ensure the comfort of the passengers, protect the chassis, and load. Suspensions have been designed to mitigate uncomfortable and harmful vibrations through the use of dampers. In cases where the suspension systems are used in semi-active controls, two control methodologies are used in making use of magneto rheological dampers. For the appropriate performance of these dampers, their nonlinear dynamics requires the use of control methodologies that are nonlinear. The first methodology involves the use of the backstopping technique. The other methodology is the QFT (Quantitative Feedback Theory). Despite the fact that QFT is designed for linear systems, it could also be used for nonlinear systems. Achievement of this can only be possible in the event nonlinear dynamics are represented as linear systems, with representations of uncertainties that are approximately true with the behavior of the plant to be controlled (Zapateiro et al., 2010).
(iii) ”Force tracking”
Force tracking is a method used in testing structures and facilities and is widely applied in seismic and civil engineering. For there to be efficient suppression of the surplus force that results from acceleration motion during the force control process, an FVFC (Force and Voltage Feed forward Controller) and FIDOB (Feed forward Inverse with Disturbance Observer) is presented. As an inner loop feed forward controller, it constitutes the real-time control voltage signal and the generated force feedback signal of the actuators’ acceleration as compensation for the specimens’ acceleration motion for better disturbance rejection model. The FVFC requires little information of the parameters or dynamic structure of the system. FIDOB is then combined with FVFC to deal with remaining disturbances as an outer-loop for the controlled testing of the electro-hydraulic hybrid system. Therefore, there is an integration of the proposed controller advantages of FVFC controller and FIDOB in terms of high tracking performance and easy implementation. The uniaxial electro-hydraulic hybrid test rig is used to carry out comparative experiments, with the effectiveness of the proposed control strategy being seen from the results from the xPC rapid prototyping technology and experiments (Dyke and Spencer Jr., 1997).