Daiki Sato

Bio: Daiki Sato is an academic researcher from Tokyo Institute of Technology. The author has contributed to research in topics: Damper & Structural engineering. The author has an hindex of 7, co-authored 60 publications receiving 153 citations.

Equivalent-input-disturbance approach to active structural control for seismically excited buildings

Abstract: A new method of active structural control, which suppresses vibrations in civil structures due to seismic shocks, has been developed. It is based on the equivalent-input-disturbance (EID) approach, which estimates the effect of a seismic shock and produces an equivalent control signal on the control input channel to compensate for it. A system designed by this method can be viewed as a conventional state-feedback control system with an EID estimator plugged in. Unlike conventional control systems, this one has two degrees of freedom, which yields better control performance. Simulations on a model of a ten-degree-of-freedom building demonstrated the validity of the method. In addition, the effect of the parameters of the low-pass filter in the EID estimator on the vibration suppression performance was examined. A comparison revealed that this method is superior to a linear-quadratic regulator and sliding-mode control.

A new performance index of LQR for combination of passive base isolation and active structural control

Abstract: This paper considers the problem of designing a state-feedback controller with both passive base isolation (PBI) and active structural control (ASC). In order to improve control performance, state-feedback gains are designed based on the linear quadratic regulator (LQR) method that optimizes a new performance index containing absolute acceleration, and inter-story drifts and velocity. Simulations on a model of an eleven degree-of-freedom shear building for four earthquake accelerograms are used to verify this method. Comparison studies show that, compared with PBI, the combination of PBI and ASC improves control performance; and this method yields better control results than the conventional ASC, which considers relative displacement and relative velocity of each story. The results are also discussed from the viewpoint of control system structure regarding the location of system zeros. In addition, the effect of weights in the LQR on control performance is discussed. A method for selecting the weights is presented by using the infinity norm of a system as a criterion to visualize their effect.

Automatic determination of LQR weighting matrices for active structural control

Abstract: This paper presents a method for the automatic selection of weighting matrices for a linear-quadratic regulator (LQR) in order to design an optimal active structural control system. The weighting matrices of a control performance index, which are used to design optimal state-feedback gains, are usually determined by rule of thumb or exhaustive search approaches. To explore an easy way to select optimal parameters, this paper presents a method based on Bayesian optimization (BO). A 10-degree-of-freedom (DOF) shear building model that has passive-base isolation (PBI) under the building is used as an example to explain the method. A control performance index that contains the absolute acceleration, along with the inter-story drift and velocity of each story, is chosen for the design of the controller. An objective function that contains the maximum absolute acceleration of the building is chosen for BO to produce optimal weighting matrices. In the numerical example, a restriction on the displacement of the PBI is used as a constraint for the selection of weighting matrices. First, the BO method is compared to the exhaustive search method using two parameters in the weighting matrices to illustrate the validity of the BO method. Then, thirty-three parameters (which are automatically optimized by the BO method) in the weighting matrices are used to elaborately tune the controller. The control results are compared to those for the exhaustive search method and conventional optimal control, in terms of the control performance of the relative displacement, absolute acceleration, inter-story-drift angle, and the story-shear coefficient of each story. The damping ratio for each mode, and the control energy and power are also compared. The comparison demonstrates the validity of the method.

Disturbance rejection and performance analysis for nonlinear systems based on nonlinear equivalent-input-disturbance approach

Abstract: This paper presents a nonlinear equivalent-input-disturbance (NEID) approach to rejecting an unknown exogenous disturbance in a nonlinear system. An NEID compensator has two parts: a conventional equivalent-input-disturbance estimator and a nonlinear state feedback term. This design ensures that only the exogenous disturbance is rejected and the useful nonlinearity of the system is retained. Unlike other active disturbance-rejection methods, a Lipschitz condition is not necessary to guarantee the convergence of the observation error. Analysis of control performance provides upper bounds for the evaluation of disturbance rejection and the degree of nonlinearity retention. Numerical examples show the validity and superiority of this method.

Carbon dioxide capturing material

Abstract: PROBLEM TO BE SOLVED: To capture and separate a carbon dioxide from gas with low concentration of carbon dioxide.SOLUTION: The carbon dioxide is captured and separated from the gas that contains the carbon dioxide by using a carbon dioxide capturing material which includes a porous body that contains a cerium oxide whose peak pore diameter of a pore volume distribution is 1.5-10 nm. Preferably, the porous body further contains at least one element selected from the group consisting of Na, Mg, Y, La, and Sm.

Proposed design models for the asymmetric friction connection

Abstract: KTA (Sarawak) Sdn Bhd, No. 33, Jalan SS 24/8, Taman Megah, 47301 Petaling Jaya, Selangor Darul Ehsan, Malaysia Department of Civil Engineering, Unitec Institute of Technology, Carrington Road, Private Bag 92025, Auckland 1025, New Zealand Department of Civil and Environmental Engineering, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand AECOM, AECOM House, PO Box 4241 Shortland St, Auckland 1140, New Zealand

A state-of-the-art review on passive friction dampers and their applications

Abstract: This paper presents a state-of-the-art review on friction type passive energy dissipation devices. Friction dampers are highly preferred as an energy dissipation device, particularly for the seismic fortification of the engineering structures due to their simplicity, reliability, and maximum energy dissipation as a result of the generation of rectangular hysteretic loops. Additionally, their performance is not significantly influenced by the loading amplitude, frequency, and the number of cycles. Hence, with a better understanding of friction mechanism and behavior, numerous novel passive dry friction dampers have been invented and applied in the field of civil engineering since 1980. However, decades of studies over these dampers are highly scattered throughout the academic community. Hence, the availability of many valuable pieces of research is out of reach for further studies. Therefore, a holistic chronological detail of advancement (development and application) in the field of passive friction dampers has been presented systematically in this study. The major purpose of this paper is to present an integrated and holistic overview of passive friction damper for the ease of further studies and generate future research directions for researchers who will be working in this field.

Novel metaheuristic-based tuning of PID controllers for seismic structures and verification of robustness

Abstract: In the present study, an active structural control using metaheuristic tuned Proportional-Integral-Derivative (PID) type controllers is presented. The aim of the study is to propose a feasible active control application considering time delay and a feasible control force. In the optimum control methodology, near-fault directivity pulse was considered for ground motion. Three different metaheuristic algorithms are separately employed in the optimum tuning of PID parameters such as proportional gain, integral time and derivative time. The employed algorithms are Flower Pollination Algorithm, Teaching Learning Based Optimization and Jaya algorithm. The maximum control force limit is considered as a design constraint. The methodology contains the time delay consideration and a process to avoid the stability problem on the trial results during the optimization process. The method is explained in three stages as The Pre-Optimization Stage, The Dynamic Analysis Stage and The Optimization Stage. The optimum PID parameters of different algorithms are very different, but the performance of active control is similar since a similar control signal can be generated by different proportion of controller gains such as proportion, integral and derivative processes. As the conclusion of the study, the amount of control force must be chosen carefully since big control forces may resulted with stability problems if the control system has long delay.