Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/transjsme.21-00180

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications  

We propose a new active vibration control strategy of structural systems based on the information of future seismic waveform observed in remote observation sites. The observed waveform information of the remote site is transmitted by a waveform transmission network to the structure under control. The waveform transmission network is realized by interconnecting multiple controlled structures and observation sites. By using the remote waveform containing the future information of the disturbance at the location of the controlled structure, we propose an active control method that achieves fairly higher control performance over conventional methodologies. A preview control consisting of the state-feedback and feedforward control (preview action) is adopted as the control law. For the preview action, a future seismic waveform in some time interval is needed. Because the future seismic waveform is not available, the preview action contributing the performance improvement is generally impossible. To get over this difficulty, an artificial intelligence–based waveform estimation system to estimate the future seismic waveform is proposed. The core of the wave estimation system is a multi-layered artificial neural network. Through a small-scale simulation study with a recorded seismic event in Japan, we show that the proposed control method achieves much higher control performance over the optimized [Formula: see text] state-feedback control law.

DOI： 10.1177/1077546319901024

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Other Link： http://journals.sagepub.com/doi/full-xml/10.1177/1077546319901024

Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/transjsme.20-00059

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Hindawi Limited  

We propose an adaptive gain scheduled semiactive control method using an artificial neural network for structural systems subject to earthquake disturbance. In order to design a semiactive control system with high control performance against earthquakes with different time and/or frequency properties, multiple semiactive control laws with high performance for each of multiple earthquake disturbances are scheduled with an adaptive manner. Each semiactive control law to be scheduled is designed based on the output emulation approach that has been proposed by the authors. As the adaptive gain scheduling mechanism, we introduce an artificial neural network (ANN). Input signals of the ANN are the measured earthquake disturbance itself, for example, the acceleration, velocity, and displacement. The output of the ANN is the parameter for the scheduling of multiple semiactive control laws each of which has been optimized for a single disturbance. Parameters such as weight and bias in the ANN are optimized by the genetic algorithm (GA). The proposed design method is applied to semiactive control design of a base-isolated building with a semiactive damper. With simulation study, the proposed adaptive gain scheduling method realizes control performance exceeding single semiactive control optimizing the average of the control performance subject to various earthquake disturbances.

DOI： 10.1155/2018/3762784

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS LTD  

As a new control design framework for motion and vibration control of mechanical and structural systems, an active/semi-active hybrid control (ASHC) methodology is proposed in this paper. In the proposed ASHC framework, a mechanical system that has both an actuator for motion and vibration control, and a semi-active control device, e.g., MR damper, for vibration control is defined as a control configuration. Depending on the location of the actuator and the semi-active device, two ASHC problems are formulated as optimization problems of the control performance on the motion and vibration control. In the ASHC approach, the higher control performance is accomplished by the cooperative and complementary control of the actuator and the semi-active control device. Some solution candidates and design examples are presented to show the effectiveness and the importance of the ASHC framework.

DOI： 10.1177/1077546314550700

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

A new semi-active control strategy that approximates a predicted control output of a reference active control is proposed. A variable parameter of a semi-active control device is selected at every time instant so that the predicted control output of the semi-active control system becomes close to the corresponding predicted control output of the reference active control as much as possible. Parameters of the reference active control law are optimized in the premise of the aforementioned output emulation' strategy so that the control performance of the semi-active control becomes good and the error' in the sense of achieved control performance between the reference active control and semi-active control systems becomes small. A pole placement method based on a linear matrix inequality (LMI) framework is adopted as the reference active control law. Parameters to determine the domain in the complex plane where the closed-loop poles are placed are searched so that control performance of the semi-active control system based on the output emulation approach is optimized. Copyright (c) 2015 John Wiley & Sons, Ltd.

DOI： 10.1002/stc.1770

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

This paper presents a new type of electromagnetic damper with rotating inertial mass that has been developed to control the vibrations of structures subjected to earthquakes. The electromagnetic inertial mass damper (EIMD) consists of a ball screw that converts axial oscillation of the rod end into rotational motion of the internal flywheel and an electric generator that is turned by the rotation of the inner rod. The EIMD is able to generate a large inertial force created by the rotating flywheel and a variable damping force developed by the electric generator. Device performance tests of reduced-scale and full-scale EIMDs were undertaken to verify the basic characteristics of the damper and the validity of the derived theoretical formulae. Shaking table tests of a three-story structure with EIMDs and earthquake response analyses of a building with EIMDs were conducted to demonstrate the seismic response control performance of the EIMD. The EIMD is able to reduce story drifts as well as accelerations and surpasses conventional types of dampers in reducing acceleration responses. Copyright (c) 2013 John Wiley & Sons, Ltd.

DOI： 10.1002/eqe.2355

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Various semi-active control methods have been proposed for vibration control of civil structures. In contrast to active vibration control systems, all semi-active control systems are essentially asymptotically stable because of the stability of general structural systems with structural damping and the energy dissipative nature of the semi-active control itself. In this study, by utilizing the aforementioned property on the stability of semi-active control systems, a structural model for the semi-active control design and a model-based semi-active control law are simultaneously designed so that the control performance of the resulting semi-active control system becomes good. The model for the control system design is assumed to be a linear parameter varying model with adjustable structural design parameters. The semi-active control law is based on the one step ahead prediction of the structural response of the designed model for the control system design. A genetic algorithm is adopted to obtain design parameters in the model for the control system design and the semi-active control law. Those design parameters are optimized so that the closed-loop system with the detailed dynamic model that accurately approximates the dynamic behavior of the real structural system and the semi-active control law obtained with the model for the control system design. The effectiveness of the present approach is shown with a simulation study. Copyright (c) 2013 John Wiley & Sons, Ltd.

DOI： 10.1002/stc.1581

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI PUBLISHING CORPORATION  

A new control design framework for vibration control, the cooperative control of active and semiactive control, is proposed in the paper. In the cooperative control, a structural system having both of an actuator and a semiactive control device, for example, MR damper and so forth, is defined as the control object. In the proposed control approach, the higher control performance is aimed by the cooperative control between the active control with the actuator and the semiactive control with the semiactive control device. A design method to determine the active control input and the command signal to drive the semiactive control device based on the one-step prediction of the control output is proposed. A simulation example of a control system design for a benchmark building is presented to show the effectiveness of the proposed control framework.

DOI： 10.1155/2014/518276

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

A new control framework of motion and/or vibration control system design for mechanical systems with a time varying mechanical and control parameters is studied. As examples of such time varying mechanical and control parameters, we can assume a variable damping or stiffness parameter of semi-active control devices and a time varying weighting function in a generalized plant respectively. The mechanical system in the present study is assumed to have also an actuator for active motion and/or vibration control. The active control law to drive the actuator is obtained by a gain-scheduling controller based on linear matrix inequalities (LMIs) so that the closed-loop system is stable for all assumed values of the time varying mechanical and control parameters in the generalized plant. We use the adjustability of the time varying mechanical and control parameters in the closed-loop system to realize given control specifications. As the control law of the time varying parameters in the closed-loop system, a multi-layered feedforward artificial neural network (ANN) is designed as a dynamic map from available signals in the control system to time varying mechanical and control parameters. Design parameters of the ANN are optimized with a genetic algorithm (GA). With a design example of an active positioning and vibration control of a mechanical system with variable damping coefficient, the proposed design approach is shown to be capable of achieving highly sophisticated control specifications that are hard to be satisfied by conventional control methods.

DOI： 10.1299/jamdsm.2014jamdsm0028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASME  

We address a simultaneous optimal design problem of a semi-active (SA) control law and design parameters in a semi-active control device for civil structures. The vibration control device (VCD) that is being developed by authors is used as the semi-active control device. The VCD is composed of a ball screw with a flywheel for the inertial resistance force and an electric motor with an electric circuit for the damping resistance force. A new bang-bang type semi-active control law referred to as inverse Lyapunov approach is proposed. In the inverse Lyapunov approach, the Lyapunov matrix in the bang-bang type semi-active control based on the Lyapunov function is searched so that the control performance of the semi-active control system is optimized. Design parameters to determine the Lyapunov function and those of the VCD are optimized with the genetic algorithm (GA). The effectiveness of the proposed approach is presented with simulation studies. [DOI: 10.1115/1.4007033]

DOI： 10.1115/1.4007033

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI PUBLISHING CORPORATION  

An LMI-based method for the integrated system identification and controller design is proposed in the paper. We use the fact that a class of a system identification problem results in an LMI optimization problem. By combining LMIs for the system identification and those to obtain a discrete time controller we propose a framework to integrate two steps for the model-based control system design, that is, the system identification and the controller synthesis. The framework enables us to obtain a good model for control and a model-based feedback controller simultaneously in the sense of the closed-loop performance. An iterative design algorithm similar to so-called Windsurfer Approach is presented.

DOI： 10.1155/2012/328186

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

In the present paper an Inverse Lyapunov method in a bang-bang type semi-active control for civil structures is proposed. The vibration control device (VCD) that has been developed by authors is employed for the semi-active control. The VCD is installed between two neighboring stories of structures like general dampers and generates two types of resistance forces, i.e. an inertial force proportional to the relative acceleration and a damping force proportional to the relative velocity of the two floors. The damping coefficient of the VCD can be changed by a command signal to an electric circuit connected to the VCD. In conventional Lyapunov-based semi-active control the Lyapunov function is firstly determined, mostly it is defined as the sum of the kinetic and potential energies at every instant, and the bang-bang type control is derived so that the dissipation rate of the defined Lyapunov function (the total energy) is maximized. In this paper, conversely, we assume the simple bang-bang type control firstly and then the Lyapunov function is searched so that the high performance on vibration suppression of civil structures, e. g. small relative displacement between adjacent two floors and absolute acceleration of each storey, etc., is achieved. Genetic Algorithm is adopted for the search of the Lyapunov function. Structural responses subject to recorded and artificial earthquake waves are used in the searching process. We show the effectiveness of the proposed Inverse Lyapunov Approach with a simulation example for a 15-storey building with three VCDs. Copyright (C) 2010 John Wiley & Sons, Ltd.

DOI： 10.1002/stc.375

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

An integrated design method of structural and semi-active control systems for civil structures is presented. The Vibration Control Device (VCD) that has been developed by authors is used as the semi-active control device. A new semi-active control method, which is referred to as the <I>inverse Lyapunov approach</I>, is proposed. In the inverse Lyapunov approach we firstly assume a bang-bang type semi-active control law based on an unknown Lyapunov function. The Lyapunov matrix that defines the Lyapunov function is optimized so that quantitative performance measures on vibration suppression of civil structures are optimized. The control design problem of the semi-active control law in the inverse Lyapunov approach results in an optimization problem of the Lyapunov matrix to construct the Lyapunov function. In the present study, in addition to the design parameters to determine the Lyapunov matrix, structural design parameters, the stiffness between neighboring two floors of the structural system itself and the parameters of the VCD, are optimized simultaneously so that the structural responses subject to recorded and/or artificial earthquake waves are optimized in the sense of the specifications on vibration suppression of civil structures. We adopt the Genetic Algorithm (GA) to get the optimal Lyapunov matrix and the structural design parameters.

DOI： 10.1299/jsdd.5.665

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

In this paper we address an integrated design problem of semi-active controlled civil structures with Vibration Control Device (VCD) that has been developed by authors. A new semi-active control law based on a one-step-ahead prediction of the seismic response is proposed. The VCD generates two types of resistance forces, i. e., a damping force proportional to the relative velocity and an inertial force proportional to the relative acceleration between two stories. The damping coefficient of the VCD can be changed with a command signal to an electric circuit connected to the VCD. In the present paper the command signal for changing the damping coefficient of each VCD is assumed to take two values, i.e., the command to take the maximum or minimum damping coefficient. The optimal command signal is selected from all candidates of command signals so that a norm of the one-step-ahead predicted seismic response, calculated by a numerical integration, is minimized. Under the semi-active control law the stiffness distribution between neighboring two stories of the structure, design parameters of the VCDs and those in the semi-active control are optimized so that the seismic responses subject to various recorded and artificial earthquake waves are optimized. Genetic Algorithm (GA) is adopted for the optimal design. A simulation example of a fifteen-story building with three VCDs is presented. With the proposed integrated design method structural parameters and the semi-active control law that achieve the good control performance have been obtained.

DOI： 10.1299/kikaic.76.1193

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer US  

The traditional design optimization of system parameters and a feedback controller usually follows a sequential strategy, where the open-loop system parameters are optimized first, followed by the controller design. However, this design strategy will not lead to an optimal closed-loop performance due to the coupled nature of the plant and controller optimization problems. Specifically, this two-step design methodology does not utilize the full design freedom to achieve an optimal overall system. It has been shown that the overall system performance can be significantly improved if the design process of the plant and the control system is integrated [17,18,28-30]. The integrated design strategy corresponds to a simultaneous optimization of the design parameters of both the plant and the controller to satisfy desired set of design specifications and to optimize the closed-loop system performance. Past research work has demonstrated the improved performance achieved using the integrated design strategy compared to the sequential method of design. © 2010 Springer Science+Business Media, LLC.

DOI： 10.1007/978-1-4419-5757-3_12

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

We propose a semi-active control of civil structures based on a one-step-ahead prediction of the seismic response. The vibration control device (VCD), which has been developed by authors, generates two types of resistance forces, i.e., a damping force proportional to the relative velocity and an inertial force proportional to the relative acceleration between two stories. The damping coefficient of the VCD can be changed with a command signal to an electric circuit connected to the VCD. In the present paper the command signal for changing the damping coefficient of each VCD is assumed to take two values, i.e., the command to take the maximum or minimum damping coefficient. The optimal command signal is selected from all candidates of command signals so that the Euclidean norm of the one-step-ahead predicted seismic response, calculated by a numerical integration, is minimized. As an example a semi-active control of a fifteen-story building with three VCDs is considered. The simulation results show that the proposed semi-active control achieves superior performance on vibration suppression compared with a passive control case where the damping coefficient of each VCD is fixed at its maximum value.

DOI： 10.1299/jsdd.4.103

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

A static-rate-feedback control for collocated structural systems is considered in this paper. The feedback gain matrix is obtained by solving linear matrix inequalities (LMIs) to minimize an upper bound of the closed-loop H-infinity or H-2 norm. The LMI conditions are obtained by assuming the form of Lyapunov matrices in the standard LMI conditions for evaluating the H-infinity or H-2 norm. We demonstrate that the obtained upper bounds of the H-infinity and H-2 norms closely match their actual values, respectively, when a relatively large amount of energy is allowed for the control. A decentralized rate feedback controller that globally minimizes the upper bound of the closed-loop H-infinity or H-2 norm can also be obtained with the proposed framework. Furthermore, if the coefficient matrices of the system&apos;s equations of motion are linear functions of structural design parameters, the obtained result for the controller synthesis can be easily extended to an integrated design problem of structural and control systems, a simultaneous optimal design of the structural design parameters and the feedback controller, while retaining the LMI structure with respect to the feedback gain matrix and structural design parameters. This fact means that the global optimal solution to the integrated design problem, which is generally hard to solve in a global sense, can be obtained if we take the upper bound of the closed-loop norm as the objective function. Copyright (c) 2008 John Wiley & Sons, Ltd.

DOI： 10.1002/stc.261

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DOI： 10.1299/kikaic.75.1770

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Language：English   Publisher：Akita University  

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Other Link： http://hdl.handle.net/10295/1712

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The authors have developed a vibration control device (VCD) using an electromagnetic damping. The device has an inertial force generated by a flywheel, and a damping force derived from an energy dissipation of a power generator. The small scale experimental model was manufactured, and the vibration tests were carried out. In this paper, for the purpose of applying the device to a large structure, new two VCDs of 30kN load range are developed, and shipped to NCREE in Taiwan. In order to investigate the dynamic properties of the VCD, performance tests are carried out, and the resisting force characteristics are measured. And vibration tests of 3-story structure with the VCDs are carried out by using a shaking table. The 3-story structure has 9m height, 3m width, and 18 tons weight. Seismic responses at each story are measured in cases of passive or semiactive type. The VCDs are controlled by Bang-Bang control which is based on minimizing the time derivative of the Lyapunov function. The effects of vibration suppression using the VCD are confirmed experimentally.

DOI： 10.1299/kikaic.75.2659

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DOI： 10.1299/kikaic.74.1303

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Language：Japanese   Publisher：Architectural Institute of Japan  

New bang-bang type semi-active control based on the theory of dissipative systems is proposed in this paper. The bang-bang type semi-active control has been adopted mainly for the vibration control of civil structures. The switching schedule of the damping coefficient of the semi-active damper has been determined with the value of the time derivative of the Lyapunov function, generally defined as the sum of the kinetic and the potential energies of the structural systems. The objective of the conventional bang-bang type control is to maximize the rate of the energy dissipation and the control scheme cannot deal with vibration suppression performance of the specific control outputs such as the absolute displacement of each floor from a quantitative aspect. We propose a new Lyapunov function using the basic result of the dissipative systems theory in this paper. With the theory of the dissipative systems the Lyapunov matrix is obtained as the solution to LMIs (Linear Matrix Inequalities) to achieve a smaller L_2 norm of the control output of interest. A design example for a semi-active control of a 3-story civil structure is presented to show the validity of the current analysis and the effectiveness of the proposed semi-active control.

DOI： 10.3130/aijs.72.33_4

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Other Link： http://www.aij.or.jp/paper/detail.html?productId=183243

DOI： 10.1299/kikaic.73.2742

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

A unified methodology of structural and/or control design for mechanical systems based on a polynomial matrix approach is proposed. A closed-loop <i>D</i>-stability specification is considered in this paper. By employing the polynomial matrix approach structural design parameters of mechanical systems, e.g., the mass, the damping and the stiffness and a feedback controller that is allowed to have a specified structure can be obtained simultaneously by solving LMIs. A simple iterative algorithm to obtain a <i>better D</i>-stable closed-loop system and a <i>better</i> central polynomial matrix is proposed. Design examples are provided to show the effectiveness of the present idea.

DOI： 10.1299/jsdd.1.605

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this paper, the authors developed a vibration control device (V.C.D.) using a power generator and a flywheel which is suitable for vibration suppression of a structure. The V.C.D. consists of a ball screw, a ball nut, a flywheel, a gear, and a power generator. The linear motion is converted into a rotating motion by the ball screw mechanism. The damping force is generated by the power generator, and controlled by an electric resistance at the terminal of the power generator. The inertial force is created by the flywheel which is attached to the end of the screw shaft. Since these forces are magnified by the ball screw and the gear, the V.C.D. has resisting force characteristics as the sum of the controllable damping force and the inertial force in the low frequency range. In order to investigate dynamic properties, a test V.C.D. is manufactured, and the resisting force characteristics are measured by using a vibration actuator. The experiments of frequency response are carried out using a shaking table, and the experimental results are compared with the theoretical results. The seismic responses are calculated under a semiactive control based on Linear Quadratic Regulator, and the effects of the vibration suppression of the V.C.D. are discussed experimentally and numerically.

DOI： 10.1299/kikaic.73.2926

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Other Link： http://hdl.handle.net/10295/1470

Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We consider an integrated design problem of structural and control systems. It is well known that even the simplest formulation of this problem results in a kind of a BMI problem. In this paper, homotopy-like iterative design method based on LMIs is proposed to obtain an optimal plant and a controller simultaneously for a full-order output feedback problem. We can deal with a multiobjective problem, e. g., H-2/H-infinity control problem etc. in the proposed design method. We can also optimize structural design parameters appearing non-linearly in the coefficient matrices of the plant state space form using the first order approximation of the non-linear dependence in the proposed algorithm. Several design examples show that the proposed algorithm works quite effectively for various integrated design problems.

DOI： 10.1080/00207170600750105

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Publisher：The Society of Instrument and Control Engineers  

In this paper we deal with a simultaneous optimal design problem of mechanical/dynamical parameters and a control system for robot manipulators. The mechanical parameters are evaluated from an index of manipulability based on Jacobian matrix of the robot manipulators. We propose an LMI based optimization method for the mechanism of the manipulator whose Jacobian matrix is an affine function on the length of each link. Dynamical parameters are evaluated by a closed-loop performance controlled by an LMI based gain-scheduled controller. We propose a new simultaneous optimal design method of mechanical/dynamical parameters and gain-scheduled controller using a numerical design algorithm that consists of an iterative LMI approximation of nonlinear matrix inequalities.

DOI： 10.9746/sicetr1965.42.1216

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DOI： 10.1299/kikaic.72.1785

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD  

We consider a shape optimization problem for a cantilevered pipe conveying fluid. The outer diameter distribution of the pipe and the location of the sensor and the actuator are optimized such that the critical flow velocity of the closed-loop system is maximized. The outer diameter distribution is optimized such that the total volume of the pipe is unchanged with the initial diameter distribution. The critical flow velocity of the closed-loop system is defined as the flow velocity which cannot be stabilized by active control law with a predetermined energy quantity. By this definition, it is physically reasonable comparing the quality of several design candidates since all candidates are actively controlled with the same energy consumption. We propose a method for obtaining the critical flow velocity with consideration of the amount of computation for the optimal design. This optimal design problem results in a maximization problem with equality and inequality constraints. We adopt simulated annealing method which is known as one of discrete optimization techniques for obtaining the optimal design. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/S0022-460X(03)00745-4

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We deal with a simultaneous optimal design of structural and control system of cantilevered pipes conveying fluid. We consider a combined pipe conveying fluid which is consisted of a beam (with variable shape) sandwiched by two pipes conveying fluid. The mathematical model of the combined pipe system is derived as a single pipe conveying fluid whose structural properties are variable. The width distribution of the beam and the location of the sensor and the actuator are structural design parameters. We employ the LQG control law with the input energy constraint as the active control method. The structural design parameters and the LQG controller are simultaneously adjusted so that the critical flow velocity of the controlled system ( closed-loop critical flow velocity) is maximized with an iterative numerical optimization technique. The simulation result shows the necessity of the simultaneous optimal design approach in designing the active control system of the cantilevered pipe conveying fluid. The experimental study is also conducted. The experimental result fairly agrees with the simulation result and emphasizes the proposed design methodology.

DOI： 10.1299/kikaic.68.817

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper considers a simultaneous optimization problem of structure and control systems. We parameterize all passive parameters of the mechanical structure such that the parameters work in the control system like static output feedback gains. Using this parameterization, we define a performance index, which consists of the quadratic term of LQ regulator and the quadratic term of dynamical forces of the structure. When DVDFB (Direct Velocity and Displacement Feedback) control law is applied to the class of a certain plant, it is shown analytically in this paper that the performance index can be expressed as a positive function of the structure parameters, which can be adjusted. This result comes from that DVDFB control law is one solution of the LQ regulator with a certain weighting function. A numerical example is given to illustrate how to use the result for practical design optimizing. In the simultaneous optimization problem for which an analytical solution can hardly obtained except for some cases, this paper shows clearly the relations between the performance index and the structure parameters under the class of the limited plant and control law. In this paper, it is shown that we can analytically obtain the structure parameters, which gives a global solution of the performance index under the defined simultaneous optimization problem.

DOI： 10.1299/kikaic.68.1728

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Language：English   Publishing type：Research paper (international conference proceedings)  

We consider a shape optimization problem for a cantilevered I pipe conveying fluid. The outer diameter distribution of the pipe and the location of the sensor and the actuator are optimized such that the critical flow velocity of the closed-loop system is maximized. The outer diameter distribution is optimized such that the total volume of the pipe is unchanged with the initial diameter distribution. The critical flow velocity of the closed-loop system is defined as the one which cannot be stabilized by active control law with a prescribed energy quantity. By this definition, it is physically reasonable comparing the quality of several design candidates since all candidates are actively controlled with the same energy consumption. We propose a method for obtaining an upper bound of the critical flow velocity with consideration of the amount of computation for the optimal design. This optimal design problem results in a maximization problem with equality and inequality constraints. We adopt SA (simulated annealing) method which is known as one of discrete optimization techniques for obtaining the optimal design.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

This paper deals with simultaneous optimal design of structure and control systems. For structures with collocated sensors and actuators, a stabilizing state-feedback gain and an estimator gain can be obtained easily. Using these two gain matrices, we can parameterize all stabilizing controllers for the structure by Youla parameterization scheme. Since stability of the closed-loop system is guaranteed, we can optimize design parameters in the structure and the controller simultaneously without taking two-step design procedures which consist of the step for controller synthesis and that for structural parameter tuning. Hence, convergence to the local optima is achieved with standard descent-based nonlinear optimization techniques (steepest descent, Newton method, etc.). By a design example, we show the effectiveness of proposed design method.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1006/jsvi.1999.2530

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Language：Japanese   Publisher：日本スキ-学会誌編集事務局  

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DOI： 10.1299/kikaic.66.793

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We consider a shape optimization problem for a cantilevered pipe conveying fluid. The pipe is controlled actively by LQG controller which is synthesized for a mathematical model of the pipe system in a specified flow velocity. The outer diameter distribution of the pipe and the location of the sensor and the actuator are optimized such that the critical flow velocity of the closed-loop system is maximized. The outer diameter distribution is optimized such that the total volume of the pipe is nuchanged with the initial diameter distribution. This optimal design problem results in a maximization problem with an equality constraint. Since the critical flow velocity of the closed-loop system may not be continuous for each design parameter, we can not utilize a gradient information of the objective function. In this paper, we use SA(simulated annealing)method which is known as one of discrete optimization techniques.

DOI： 10.1299/kikaic.66.45

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Language：Japanese   Publisher：日本スキ-学会誌編集事務局  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JSME  

This paper deals with simultaneous optimal design of structure and control systems. For structures with collocated sensors and actuators, a stabilizing state-feedback gain and an estimator gain can be obtained easily. Using these two gain matrices, we can parameterize all stabilizing controllers for the structure by Youla parameterization scheme. Since stability of the closed-loop system is guaranteed, we can optimize design parameters in the structure and the controller simultaneously without taking two-step design procedures which consist of the step for controller synthesis and that for structural parameter tuning. Hence, convergence to the local optima is achieved with standard descent-based nonlinear optimization techniques (steepest descent, Newton method, etc.). By a design example, we show the effectiveness of proposed design method.

DOI： 10.1299/jsmec.43.326

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper deals with simultaneous optimal design of structure and control systems. For structures with collocated sensors and actuators, a stabilizing state-feedback gain and an estimator gain can be derived easily. Using these two gain matrices, we can parameterize all stabilizing controllers for the structure by Youla parameterization scheme. Since stability of the closed-loop system is completely guaranteed, we can optimize design parameters in the structure and the controller simultaneously without taking two-step procedures which consist of the step for controller synthesis and that for structural parameter tuning. Hence, convergence to the local optima is achieved using standard descent-based nonlinear optimization techniques (steepest descent, Newton method, etc. ). By a design example, we show the effectiveness of the proposed design method.

DOI： 10.1299/kikaic.65.515

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper deals with a stabilization of cantilevered pipes conveying fluid. To suppress the unstable phenomena of the pipe system, we employ so called gain scheduling technique. This control design procedure consists of following two steps. First, several linear time invariant controllers are obtained for the pipe system with fixed flow velocity. Next, those controllers are scheduled according to the flow velocity, i.e. scheduling parameter. The control object which consists of the pipe system and the actuator is modeled mathematically by Galerkin method. The experimental setup consists of the pipe system, a laser sensor, an A/D converter, a personal computer, a D/A converter, a DC servomotor which is used as an actuator, and a flow meter. The flow meter measures the flow velocity which is used in the controller. Experimental results show that the gain scheduled controller has superior property to stabilize unstable phenomena of the pipe system.

DOI： 10.1299/kikaic.65.1448

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS LTD  

This paper deals with the stabilization of flutter in cantilevered pipes conveying: fluid with constraints on input energy for control. The controller in this study is designed by using an algorithm which iteratively tunes the weighting matrix of the quadratic performance index in the LQG problem. This controller design method takes the performance of the actuator into consideration. The theoretical and experimental results show that the effectiveness of the controller in stabilizing flutter in cantilevered pipes conveying fluid varies according to the input variance constraints, i.e., the difference in the dynamic range of an actuator. Furthermore, the critical flow velocity at instability of the pipe can be estimated by the method stated in this paper, where the system loses its stability because of the restriction of control force produced by an actuator. (C) 1998 Academic Press.

DOI： 10.1006/jfls.1997.0154

Web of Science

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper deals with an optimal placement problem of sensors and actuators for active vibration control of flexible structures. For undamped flexible structures with collocated sensors and actuators, each solution of two generalized algebraic Riccati equations are obtained explicitly. Using these two solutions, it is shown that the stabilizing H_∞ suboptimal controller based on the normalized left coprime factorization approach can be synthesized directly for all candidates of the placement. The sensor/actuator placement problem which optimizes other closed-loop performance can be formulated easily by applying this H_∞ controller. As a design example, a placement problem which minimizes H_2 norm of the closed loop transfer matrix using this H_∞ controller is considered for a cantilevered beam. The experimental results show the effectiveness of the sensor/actuator placement method stated in this paper.

DOI： 10.1299/kikaic.64.1508

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper deals with a sensor/actuator placement problem in design of active vibration control system for flexible structures. This problem is formulated as a minimization problem of the total energy which is defined as a sum of a kinetic and strain energy in a colatrolled structure with a constraint of control effort. The inequality constraint on the variance of the closed loop control effort is adopted to represent the capacity of the actuator. Using a design algorithm which iteratively tunes the weighting matrix of the quadratic performance index in LQG problem, the controller which meets these specifications can be synthesized. The optimal location of the sensor/actuator is determined by calculating the total energy for each candidate of them under several energy constraints of the control effort. It is found that the optimal placement of the sensor/actuator depends on the input energy constraint. The simulation and a experiment for a cantilevered beam as a typical example of flexible structures are conducted. It is shown that these results of the optimization can be used as a guide to the design of active vibration control systems.

DOI： 10.1299/kikaic.64.2536

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Recent advances in the field of control theory have enabled us to design active vibration control systems for various large-flexible structures. In many cases, the controller used to achieve vibration suppression has been synthesized for the given mathematical model of the structure. The control system designer has not been able to utilize the degree of freedom to adjust the structural parameters of the control object. To overcome this problem, some studies are now using on the so-called "Structure/Control Simultaneous Optimization" method, which involves a numerical optimization technique. In this paper, we parametrize all controllers to optimize the structure and control systems simultaneously and show that these controllers have a special form of a decentralized-type controller. In this framework, a criterion is given to judge whether the result of the optimization is valid from the viewpoint of the energy needed to achieve the desired closed-loop performance. Using this concept, a constrained optimization problem is formulated and solved numerically.

DOI： 10.1299/kikaic.63.3454

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Publisher：The Society of Instrument and Control Engineers  

In this paper, we consider the design problem of simultaneous stabilizing controller which takes into account various closed-loop performances, e.g. sensitivity or robust stability etc.. Using the parametrization of simultaneous stabilizing controller, this problem is formulated as a standard model-matching-type problem whose objective function is affine in the design parameter. Under this formulation, a simple sufficient condition to achieve simultaneous stabilization is derived as in the form of an inequality <i>H</i>_∞ norm constraint on the design parameter. Moreover, we show that the presented design problem including above constraint can be cast as convex optimization problem. By a design example, the effectiveness of the proposed method is presented.

DOI： 10.9746/sicetr1965.33.875

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We presents an active control of cantilevered pipes conveying fluid with constraint on input energy. The controller used in this study is designed with constraints on input energy variances. LQG control law is used to obtain the feedback controller. This controller design method takes the performance of the actuator into consideration. The control object which consists of a pipe system and an actuator is modeled mathematically by the Galerkin method. The experimental setup consists of the pipe system, a laser sensor, an A/D converter, a personal computer, a D/A converter, and a DC servomotor which produces a transverse force for active control of the pipe. The experimental results show that the effectiveness of the controller in stabilizing unstable phenomena of cantilevered pipes conveying fluid varies according to the conditions of input variance constraints.

DOI： 10.1299/kikaic.62.4507

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DOI： 10.1299/kikaic.62.3394

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

There have been many reports on the design of active vibration control systems. Most of them have optimized control systems based on the LQ optimal regulator or H_∞ control theory. However, there are no answers to the problem whether given passive parameters of plants (e. g. , spring constant on damping coefficient) are 'suitable' for the designed controller. In this paper, we consider structure and control simultaneous optimization for an active vibration control system. To provide solutions, several methods have been proposed which are based on tuning the design paramethers existing in the structure and controller. Most of the control laws are those of standard LQ optimal requlators which require full states measurements and estimate performance of a closed-loop control systems in the time domain. From the viewpoint of active vibration control, it is natural to discuss the performance of the control system in the frequency domain. Therefore, we adopt the frequency shaped LQG control law in simultaneous optimization design, which enables output feedback control and frequency shaping.

DOI： 10.1299/kikaic.61.1450

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Recently, LQ optimal regulators have been successfully applied to design of active vibration control systems. Most of them have been discussed in terms of the closed-loop performance and the relationship to the performance indices. However, optimization through the entire design procedure has not been completed on passive elements. So, for optimizing all design parameters, we propose a numerical method which is based on the necessary condition for controller parameters and the performance sensitivities to passive parameter changes. The method includes an iterative procedure ; the convergence is examined using 2-degree-of-freedom models. It is shown that the proposed method provides good closed-loop performance and LQ optimality.

DOI： 10.1299/kikaic.61.4264

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Integrated Design of Large-Scale Collocated Structural System and Control Parameters Using a Norm Upper Bound Approach (Mona Meisami-Azad, Javad Mohammadpour Velni, Kazuhiko Hiramoto and Karolos M. Grigoriadis, in J. Mohammadpour and K.M. Grigoriadis Eds. Efficient Modeling and Control of Large-Scale Systems)

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Event date： 2014.7

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Event date： 2014

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As a method for semi-active control of structural systems, the active-control-based method that emulates the control force of a targeted active control law by semi-active control devices has been studied. In the active-control-based method, the semi-active control devices are not necessarily able to generate the targeted active control force because of the dissipative nature of those devices. In such a situation, the meaning of the targeted active control law becomes unclear in the sense of the control performance achieved by the resulting semi-active control system. In this study, a new semi-active control strategy that approximates the control output (not the control force) of the targeted active control is proposed. The variable parameter of the semi-active control device is selected at every time instant so that the predicted control output of the semi-active control system becomes close to the corresponding predicted control output of the targeted active control as much as possible. Parameters of the targeted active control law are optimized in the premise of the above "output emulation" strategy so that the control performance of the semi-active control becomes good and the "error" of the achieved control performance between the targeted active control and the semi-active control becomes small.

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Event date： 2013.9

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Event date： 2013.9

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Event date： 2013.8

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As a method for semi-active control of structural systems, the active-control-based method that emulates the control force of a targeted active control law by semi-active control devices has been studied. In the active-control-based method, the semi-active control devices are not necessarily able to generate the targeted active control force because of the dissipative nature of those devices. In such a situation, the meaning of the targeted active control law becomes unclear in the sense of the control performance achieved by the resulting semi-active control system. In this study, a new semi-active control strategy that approximates the control output (not the control force) of the targeted active control is proposed. The variable parameter of the semi-active control device is selected at every time instant so that the predicted control output of the semi-active control system becomes close to the corresponding predicted control output of the targeted active control as much as possible. Parameters of the targeted active control law are optimized in the premise of the above "output emulation" strategy so that the control performance of the semi-active control becomes good and the "error" of the achieved control performance between the targeted active control and the semi-active control becomes small.

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Event date： 2013

Language：English  

As a method for semi-active control of structural systems, the active-control-based method that emulates the control force of a targeted active control law by semi-active control devices has been studied. In the active-control-based method, the semi-active control devices are not necessarily able to generate the targeted active control force because of the dissipative nature of those devices. In this study, a new semi-active control strategy that approximates the control output of the targeted active control is proposed. The variable parameter of the semi-active control device is selected at every time instant so that the predicted control output of the semi-active control system becomes close to the corresponding predicted control output of the targeted active control as much as possible. Parameters of the targeted active control law are optimized in the premise of the above "output emulation" strategy so that the control performance of the semi-active control becomes good and the "error" of the achieved control performance between the targeted active control and the semi-active control becomes small.

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Event date： 2013

Language：English  

As a method for semi-Active control of structural systems, the active-control-based method that emulates the control force of a targeted active control law by semi-Active control devices has been studied. In the active-control-based method, the semi-Active control devices are not necessarily able to generate the targeted active control force because of the dissipative nature of those devices. In this study, a new semi-Active control strategy that approximates the control output of the targeted active control is proposed. The variable parameter of the semi-Active control device is selected at every time instant so that the predicted control output of the semi-Active control system becomes close to the corresponding predicted control output of the targeted active control as much as possible. Parameters of the targeted active control law are optimized in the premise of the above "output emulation" strategy so that the control performance o f the semi-Active control becomes good and the "error" of the achieved control performance between the targeted active control and the semi-Active control becomes small.

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Event date： 2012.9

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Event date： 2012.9

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Event date： 2011.9

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Various semi-active control methods have been proposed for vibration control of civil structures. In contrast to active vibration control systems, all semi-active control systems are essentially asymptotically stable because of the stability of the structural systems (with structural damping) themselves and the energy dissipating nature of the semi-active control law. In this study, by utilizing the above property on the stability of semi-active control systems, a reduced-order structural model and a semi-active control law are simultaneously obtained so that the performance of the resulting semi-active control system becomes good. Based on the above fact any semi-active control laws derived from some models stabilize all real-existing structural systems that have structural damping. It means that the difference of dynamic behaviors between the real structural system and the reduced-order mathematical model in the sense of the open-loop response is no longer an important issue. In other words, we do not have to consider the closed-loop stability, which is one of the most important constraints in active control, in the process of the reduced-order structural modeling and the semi-active control design. We can only focus on the control performance of the closed-loop system with the real structure with the (model-based) semi-active control law in obtaining the reduced-order model. The semi-active control law in the present study is based on the one step ahead prediction of the structural response. The Genetic Algorithm (GA) is adopted to obtain the reduced-order model and the semi-active control law based on the reduced order model.

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Event date： 2011

Language：English  

Various semi-active control methods have been proposed for vibration control of civil structures. In contrast to active vibration control systems, all semi-active control systems are essentially asymptotically stable because of the stability of the structural systems themselves (with structural damping) and the energy dissipating nature of the semi-active control law. In this study, by utilizing the above property on the stability of semi-active control systems, a reduced-order structural model and a semi-active control law are simultaneously obtained so that the performance of the resulting semi-active control system becomes good. Based on the above fact any semi-active control laws derived from some models stabilize all real-existing structural systems that have structural damping. It means that the difference of dynamic behaviors between the real structural system and the reduced-order mathematical model in the sense of the open-loop response is no longer an important issue. In other words, we do not have to consider the closed-loop stability, which is one of the most important constraints in active control, in the process of the reduced-order structural modeling and the semi-active control design. We can only focus on the control performance of the closed-loop system with the real structure with the (modelbased) semi-active control law in obtaining the reduced-order model. The semi-active control law in the present study is based on the one step ahead prediction of the structural response. The Genetic Algorithm (GA) is adopted to obtain the reduced-order model and the semi-active control law based on the reduced order model. Copyright © 2011 by ASME.

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Event date： 2010

Language：English  

We address a simultaneous optimal design problem of a semi-active control law and design parameters in a vibration control device for civil structures. The Vibration Control Device (VCD) that is being developed by authors is used as the semiactive control device in the present paper. The VCD is composed of a mechanism of a ball screw with a flywheel for the inertial resistance force and an electric motor with an electric circuit for the damping resistance force. A new bang-bang type semiactive control law referred to as Inverse Lyapunov Approach is proposed as the semi-active control law. In the Inverse Lyapunov Approach the Lyapunov function is searched so that performance measures in structural vibration control are optimized in the premise of the bang-bang type semi-active control based on the Lyapunov function. The design parameters to determine the Lyapunov function and the design parameters of the VCD are optimized for the good performance of the semi-active control system. The Genetic Algorithm is employed for the optimal design.

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Event date： 2010

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Event date： 2010

Language：English  

An LMI-based method for the simultaneous system identification and controller design is proposed in the paper. With the fact that a class of system identification problem results in an LMI optimization problem a model update with a constraint on the closed-loop performance in an approximate sense is proposed. By combining the LMI-based identification method with the LMI-based conventional controller design we propose a framework to integrate two steps, system identification and controller design. The framework enables us to obtain a good model and feedback controller simultaneously in the sense of the closed-loop performance. An iterative design algorithm similar to so-called Windsurfer Approach is presented in the paper.

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Event date： 2010

Language：English  

In a previous paper the authors developed a semiactive damper that generates electrical power, and carried out vibration tests using a 3-story benchmark structure at NCREE, Taiwan in 2006. At that time, the dampers were installed at 1st and 2nd floors. The damper has a large inertia mass by flywheel and controllable damping force by generator, and a load capacity of 30 kN. In the test, the damper at 1st floor was only controlled by Bang-bang control that was based on Lyapunov function.
In this paper as the next step, in order to demonstrate more effectiveness of vibration suppression, the dampers are installed at all floors of the 3-story structure, and vibration tests using the same structure are carried out again in 2008. The control law which is proposed here is based on Lyapunov function or predictive switching control for all of damper at each floor. The structure has 9 m high, 3 m wide, 2 m span, 18 tons total weight. Several earthquake waves normalized to be 150 gal are inputted horizontally to the base by a shaking table, and the seismic responses of each floor are estimated quantitatively. It is obviously from the experimental results that the seismic reductions for acceleration and displacement in case of large inertia mass are much better than the case of small one, but control effect is decreasing. Because seismic reduction can be depended on a balance between inertial force and controllable damping force, and plus the one of the reason is time delay of the damper. At last, we can summarize that the semiactive damper is available for seismic isolation in practical use.

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Event date： 2010

Language：English  

In a previous paper the authors proposed a semi-active vibration control device (VCD) that generates power. The device utilizes a ball screw, and has inertial and damping forces. The damping coefficient is adjusted by altering resistance at the terminal of the power generator. A small-scale VCD was manufactured for experimental testing. Frequency responses of a small-scale spring mass structure were measured in order to confirm the effects of vibration suppression within a wide range of frequencies.
In this paper, as the next step, vibration tests using a benchmark structure with an installed VCD that has a 30 kN capacity are carried out at the National Center for Research on Earthquake Engineering (NCREE) in Taiwan The benchmark structure has three stories with a 3 m height and a mass of 6 tons at each floor level for a total height and weight of 9 m and 18 tons, respectively. The VCDs arc installed between adjacent floors with steel chevron braces A simple control law that is based on a minimized Lyapunov function and employs bang-bang operation is used as a variable current controller instead of the modifying the resistance level of the VCD. Scaled earthquake motions including the Imperial Valley El Centro north-south component that is normalized to be a peak level of 0 5 m/s(2), are applied to the base of the steel framed structure in the horizontal direction by a shaking table Experimental responses of each floor for the uncontrolled and controlled cases are compared with analytical responses, and effects of vibration suppression for the large-scale model are discussed quantitatively

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Event date： 2010

Language：English  

We propose a semi-active control of civil structures based on a one-step-ahead prediction of the seismic response. The vibration control device (VCD), which has been developed by authors, generates two types of resistance forces, i.e., a damping force proportional to the relative velocity and an inertial force proportional to the relative acceleration between two stories. The damping coefficient of the VCD can be changed with a command signal to an electric circuit connected to the VCD. In the present paper the command signal for changing the damping coefficient of each VCD is assumed to take two values, i.e., the command to take the maximum or minimum damping coefficient. The optimal command signal is selected from all candidates of command signals so that the Euclidean norm of the one-step-ahead predicted seismic response is minimized. As an example a semi-active control of a fifteen-story building with three VCDs is considered. The simulation results show that the proposed semi-active control achieves superior performance on vibration suppression compared with a passive control case where the damping coefficient of each VCD is fixed at its maximum value. Copyright © 2009 by ASME.

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Event date： 2010

Language：English  

A new collaborative control strategy between time varying design parameters in LPV plants and the feedback controllers is proposed in the present paper As the feedback control law the gain scheduling control scheme is adopted to guarantee the closed-loop L(2) gain performance against the variation of the time varying parameter in the control object. The gain-scheduling controller can be obtained in an analytical manner by solving LMIs. For the closed-loop system with the LPV plant and the gain scheduling controller Genetic algorithm (GA), known as a so-called intelligent optimization method, is applied to optimize the closed-loop response. The proposed control system has a complementary structure between the LMI-based analytical control strategy and the flexible intelligent control method that does not impair their advantages each other In this sense a win-win situation for the LMI-based gain scheduling control and the GA-based intelligent optimization is realized in the proposed approach. A simple simulation example is presented to show the effectiveness of the proposed method.

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Event date： 2010

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Event date： 2010

Language：English  

Functional electrical stimulation (FES) rowing is a whole-body exercise in which the lower extremities are moved by electric stimulation and the upper extremities are moved voluntarily by paraplegics. The purpose of this study was to identify the kinematic factors of the lower extremities required to perform FES-rowing through the biomechanical analysis. Eighteen healthy adult men participated in this study. A mathematical model was developed to analyze the conventional rowing with or without handle and FES lower extremity extension exercise. The calculated data has the potential to be applied in the low-load and safe FES rowing exercise for the paraplegics. ©2010 IEEE.

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Event date： 2009

Language：English  

In this paper, we address the problem of integrated design of output feedback control, structural damping parameters, and sensor/actuator placement to satisfy an upper bound on the closed-loop ℋ∞ or ℋ2 norm performance of externally symmetric systems. By combining results on the upper bound of the closed-loop norm for externally symmetric systems with a homotopy-like approximation of an optimization problem, we provide a formulation of the integrated design problem of minimizing the upper bound ℋ∞ or ℋ2 norm via iterative LMI optimization problems. In this formulation, the corresponding decision variables are the structural damping parameters, the static rate feedback gain, and the sensor and actuator locations. By iteratively solving the approximated LMI problem, a locally optimal solution is obtained. The method is validated on a numerical example of active collocated vibration control of a simply supported beam. ©2009 IEEE.

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Event date： 2009

Language：English  

In this paper, we address the problem of integrated design of output feedback control, structural damping parameters, and sensor/ actuator placement to satisfy an upper bound on the closed-loop H-infinity or H-2 norm performance of externally symmetric systems. By combining results on the upper bound of the closed-loop norm for externally symmetric systems with a homotopy-like approximation of an optimization problem, we provide a formulation of the integrated design problem of minimizing the upper bound H-infinity or H-2 norm via iterative LMI optimization problems. In this formulation, the corresponding decision variables are the structural damping parameters, the static rate feedback gain, and the sensor and actuator locations. By iteratively solving the approximated LMI problem, a locally optimal solution is obtained. The method is validated on a numerical example of active collocated vibration control of a simply supported beam.

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Event date： 2009

Language：Japanese  

This development of machines and equipment to make elderly people healthy in their daily lives is becoming increasing important these days. Especially, resistance training equipment is effective for prevention of muscle atrophy in not only healthy adult people, but also the elderly people, and even disabled individuals. Functional Electrical Stimulation (FES) is the artificial stimulation of muscle which have lost nervous control, with the aim of providing muscular contraction and producing a functional useful movement for exercise, standing, and walking. Some authors demonstrated that FES-rowing for persons with spinal cord injury was safe and it also decreased the risk factors for cardiovascular disease. Based on a new concept to effectively restrengthen disused muscles and to enable whole body exercise in seniors or paraplegics, we developed a hybrid power rehabilitation equipment including FES technology. The purpose of this study was to analyze the body load in case of rowing exercise.

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Event date： 2008.7

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Event date： 2008.7

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Event date： 2008.7

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Event date： 2008.7

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Event date： 2008

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Event date： 2008

Language：English  

Recently, structural problems in tall buildings and power plants have become evident as a result of long-period vibrations due to earthquakes. In order to ameliorate these problems a number of damping devices have been developed by many researchers. One of the authors also has developed the Mechatro damper which has a damping force that is imposed on the structure by a power generator. The force of the damper is proportional to its velocity. On the other hand, the mechanical snubber utilizes an inertial force derived from a flywheel that is proportional to acceleration. That is, the device has a so-called series inertia mass. The authors developed a vibration cut-off system using water or a functional fluid that acts as a series inertia mass, and the effects of vibration cut-off have been confirmed. In a previous paper the authors proposed a new vibration control device (VCD) that also generates power. The VCD has an inertial force created by an inertial disk and damping force provided by energy dissipation of the power generator. This device acts as a semi-active damper, and functions as a fail-safe mechanism under controller malfunction. A prototype model was fabricated and vibration tests were carried out in a laboratory. The focus of this paper is application of the prototype large-scale VCD to a real structure. Two new VCDs that have a force capacity in the range of 15 kN have been manufactured and shipped to the National Center for Research on Earthquake Engineering (NCREE) in Taiwan for testing on a three-story structure that is excited by a large shake table. In order to investigate dynamic properties of the VCD, performance tests are carried out and the resisting force characteristics of the device are measured. Next, vibration tests are conducted on the structure by a shake table with the VCDs installed. Seismic responses at each story level are measured for the Imperial Valley, El Centro north-south component of motion. A control law that is based on minimizing the Lyapunov function is used along with bang-bang operation of the VCD. The effects of vibration suppression using the VCD are shown to be confirmed. © 2008 ASCE.

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Event date： 2007.9

Language：Japanese  

In the previous paper the authors proposed a new vibration control device (V.C.D.) using power generator. The device has an inertial force created inertia disk, and damping force derived an energy dissipation of the power generator. The trial experimental model was made, and the vibration tests were carried out in our laboratory. In this paper, for the purpose of applying the device to a real large structure, new two V.C.D.s for 15 kN range are manufactured, and shipped to NCREE, Taiwan. In order to investigate about dynamic properties of the V.C.D., performance tests are carried out, and the resisting force characteristics are measured. Next, vibration tests of 3-story structure when the V.C.D.s are attached are carried out using by shaking table. Seismic responses at each story are measured when the earthquake wave of Imperial Valley El Centro NS component is inputted. The control law based on minimizing the Lyapunov function is used, and it is controlled by Bang-Bang type. The effects of vibration suppression using the V.C.D. are confirmed.

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Event date： 2007.5

Language：Japanese  

In this paper we deal with a simultaneous optimal design problem of dynamic parameters and the trajectory for robot manipulators. The dynamic characteristic of robot manipulators is uniquely determined by base parameters, which are functions of physical parameters, e.g., the mass the moment of inertia and damping, etc.. We propose a new simultaneous optimal design method of base parameters and the trajectory using a numerical design algorithm. The optimal base parameters can be obtained by proposed method for the resultant trajectory.

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Event date： 2007

Language：English  

In this paper we deal with a global optimal design of dynamic parameters of robot manipulators. The dynamic characteristic of robot manipulators is uniquely determined by base parameters, which are functions of physical parameters, e.g., the mass, the moment of inertia and the damping of each link, etc.. Using the fact that the equation of motion of manipulators generally becomes an affine function on the base parameters we propose an LMI based global optimal design of the base parameters of robot manipulators. In this paper we obtain the global optimal base parameters minimizing the required energy to achieve a given task (given by the reference trajectory of the end-effector). We adopt the computed torque method as the control law for the robot manipulators. The proposed design method guarantees the global optimality of the optimized base parameters. As a design example an optimal design of the base parameters of planar two link manipulator is presented.

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Event date： 2007

Language：English  

We propose a new collaborative control strategy between time varying design parameters of the plant and the feedback controller. As the feedback control law we adopt the LMI based gain scheduling control scheme to guarantee the closed-loop L-2 gain performance against the variation of the time varying parameter of the control object. Under the gain scheduling control we propose a method for the adjustment of the time varying parameter using the theory of dissipative systems. The objective of the time varying parameter tuning is to obtain smaller L-2 norm of the controlled output. We refer to this control strategy as Active Gain Scheduling Control (AGSC) because the scheduling parameter is actively changed while the control system is working. We show that the tuning rule of the time varying design parameter becomes a bang-bang type in some cases.

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Event date： 2006

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Event date： 2006

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Event date： 2005.8

Language：Japanese  

In this paper we deal with a simultaneous optimal design problem of mechanical/dynamical parameters and a control system for robot manipulators. The mechanical parameters are evaluated from an index of manipulability based on Jacobian matrix of the robot manipulators. We propose an LMI based optimization method for the mechanism of the manipulators whose Jacobian matrix becomes an affine function on the length of each link. Dynamical parameters are evaluated by a closed-loop performance controlled by a gain-scheduled controller. We propose a new simultaneous optimal design method of mechanical/dynamical parameters and gain-scheduled controller using a numerical design algorithm of an iterative LMI approximation.

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Event date： 2005

Language：English  

We consider an integrated design problem of structural and control systems. It is well known that even the simplest formulation of this problem results in a kind of a BMI problem. In this paper, a homotopy-like iterative design method based on LMIs is proposed to obtain an optimal plant and a controller simultaneously for a full-order output feedback problem. We can deal with a multiobjective problem, e.g., H-2/H-infinity control problem etc. in the proposed design method. We can also optimize structural design parameters appearing nonlinearly in the coefficient matrices of the plant state-space form using the first order approximation of the nonlinear dependence in the proposed algorithm. Several design examples show that the proposed algorithm works quite effectively for various integrated design problems.

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Event date： 2005

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Event date： 2003.10

Language：Japanese  

In actively controlled cantilevered pipes conveying fluid the critical flow velocity depends not only on the structural property of the pipe but also the feedback controller. In this report we discuss an integrated design of a cantilevered pipe conveying fluid to optimize both parameters in the pipe system and the controller in simultaneous manner. The pipe is composed by a beam with variable width and two pipes conveying fluid attached on both sides of the beam. The beam is divided into several parts and the width of each part can be independently adjusted so as to obtain the higher closed-loop critical flow velocity. This means that the resulted beam has a stepped form after the optimization The location and the number of the division of the beam are determined by the sign distribution of the sensitivity function of the critical flow velocity on the small width change of each divided part of the beam. The effectiveness of the proposed design methodology is justified by a simulation study.

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Event date： 2003

Language：English  

We deal with an integrated design problem of structural and control systems. For a plant with unstable poles and zeros we consider a design problem of the plant itself for minimizing the closed-loop H-infinity norm. The design parameter of the optimal design problem is the location of unstable poles and zeros of the plant. The achievable minimum., norm of the closed-loop system can be obtained just by examining the determinant of Pick matrix defined by the unstable poles and zeros of the plant. We show the analytic relation between the unstable poles/zeros and the optimal closed-loop H-infinity norm for a class of plants with two unstable poles (and/or zeros). In the general case (the number of unstable poles/zeros is more than three) the optimal design problem can be formulated as a minimization of the maximum eigenvalue in a generalized eigenvalue problem related to Pick matrix.

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Event date： 2002.11

Language：Japanese  

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Event date： 2002

Language：English  

A design problem of active controlled micromachines has been considered in this paper. Stable two-dimensional vibration of a structure at pre-specified frequencies is sought subject to the vibration amplitude and the actuator capacity requirements. It is shown that the simultaneous optimization both on the mechanical structure and the active controller is quite useful for this kind of design problems.

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Event date： 2001.9

Language：Japanese  

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Event date： 2001.8

Language：Japanese  

We deal with a simultaneous optimal design of structural and control system of cantilevered pipes conveying fluid. A combined pipe conveying fluid, which is a beam (with variable shape) sandwiched by two pipes conveying fluid is considered in this report. The mathematical model of the combined pipe system is derived as a single pipe conveying fluid whose structural properties are variable. The width distribution of the beam and the location of the sensor and the actuator are structural design parameters. We employ the LQG control law with the input energy constraint as the active control method. The structural design parameters and the LQG controller are simultaneously adjusted so that the critical flow velocity of the controlled system (closed-loop critical flow velocity) is maximized with an iterative numerical optimization technique. The simulation result shows that the necessity of the simultaneous optimal design methodology for designing the active control system of the cantilevered pipe conveying fluid. The experimental study is also conducted. Fairly agreement is achieved between the simulation and the experimental results. The result of the experiment emphasizes the proposed design method.

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Event date： 2001.8

Language：Japanese  

This report deals with an attempt of the development of the new ski-system for legs-disabled persons. This ski-system is a sledge type which has two ski plates and the rotation mechanism operated by hands. Therefore, this is safe and useful for beginners and serious disabled persons. The rotation mechanism is introduced such that the beginners can easily turn by parallel christiania and stop by snowplow. Furthermore, this ski-system has the mechanism moving the center of gravity. We examine the abilities of this ski-system in a skiing slope and compare the skiing turn between with and without this mechanism by means of three-dimensional motion analysis. It is found that this mechanism is effective in realizing a stable skiing turn.

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Event date： 2001.4

Language：Japanese  

We deal with an integrated design problem of structural and control systems. The integrated design, problem is formulated as an optimization problem for obtaining the class of the control object and the controller. With LMI based gain scheduled controller design scheme we propose an integrated design algorithm. The algorithm is an iterative method which is constructed by an LMI optimization and a vertex moving of the passive parameter. We show that the design algorithm is guaranteed to converge at least to a local optimal solution if the direction and the size of the vertex moving are selected appropriately.

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Event date： 2001

Language：English  

We consider a shape optimization problem for a cantilevered I pipe conveying fluid. The outer diameter distribution of the pipe and the location of the sensor and the actuator are optimized such that the critical flow velocity of the closed-loop system is maximized. The outer diameter distribution is optimized such that the total volume of the pipe is unchanged with the initial diameter distribution. The critical flow velocity of the closed-loop system is defined as the one which cannot be stabilized by active control law with a prescribed energy quantity. By this definition, it is physically reasonable comparing the quality of several design candidates since all candidates are actively controlled with the same energy consumption. We propose a method for obtaining an upper bound of the critical flow velocity with consideration of the amount of computation for the optimal design. This optimal design problem results in a maximization problem with equality and inequality constraints. We adopt SA (simulated annealing) method which is known as one of discrete optimization techniques for obtaining the optimal design.

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Event date： 2000.10

Language：Japanese  

We consider an integrated design problem of structural and control systems for a class of lossless systems. For such class of control object we show that the maximum stability margin for the normalized coprime factorization becomes 1/√<2>. With this result the H_∞ controller proposed by McFarlane and Glover can be obtained explicitly. We show that an integrated design of the structural and control system for the closed-loop system can be approximately cast as LMI.

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Event date： 2000.9

Language：Japanese  

This report deals with an optimal sensor/actuator placement problem for active control of a cantilevered pipe conveying fluid. The optimal sensor/actuator/placement is determined such that the closed-loop critical flow velocity is maximized. We adopt LQG control law with constraint on input variance. The optimal placement is obtained by searching over all candidates of the sensor/actuator placement. It is found that the closed-loop critical flow velocity highly depends on their placements. Moreover, the optimal sensor/actuator placement also depends on the input wariance constraint. The obtained result are partially verified by an experiment.

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Event date： 2000.9

Language：Japanese  

We consider a shape optimization problem for a cantilevered pipe conveying fluid. The outer diameter distribution of the pipe and the location of the sensor and the actuator are optimized such that the critical flow velocity of the closed-loop system is maximized. The outer diameter distribution is optimized such that the total volume of the pipe is unchanged with the initial diameter distribution. The critical flow velocity of the closed-loop system is defined as the one which cannot be stabilized by active control law with a prescribed energy quantity. By this definition, it is physically reasonable comparing the quality of several design candidates since all candidates are actively controlled with the same energy. We propose a method for obtaining an upper bound of the critical flow velocity with consideration of the amount of computation for the optimal design. This optimal design problem results in a maximization problem with equality and inequality constraints. We adopt SA (simulated annealing) method which is known as one of discrete optimization techniques for obtaining the optimal design.

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Event date： 2000

Language：Japanese  

This report deals with an attempt of the development of the new ski-system for legs-disabled persons. This ski-system is a sledge type which has two ski plates and the rotation mechanism operated by hands. Therefore, this is safe and useful for beginners and serious disabled persons. The rotation mechanism is introduced such that the beginners can easily turn by parallel christiania and stop by snowplow. We examine the abilities of this ski-system in a skiing slope and compare the skiing turns between able bodied and disabled persons by means of three-dimensional motion analysis. It is found that the carving turn and the stable snowplow can be realized by this ski-system.

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Event date： 1999

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Event date： 1999

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Event date： 1999

Language：English  

We consider an integrated design problem of structural and control systems. Using reduced-order H∞ controller design method proposed by Mustafa and Glover, we formulate the integrated design as a simultaneous design of the structural design parameter and the reduced order H∞ controller. The formulated problem does not need to take an iterative procedure (controller synthesis and structural modification) which is employed in most integrated design.

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Event date： 1997

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Event date： 1997

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Event date： 1997

Language：English  

This paper deals with the stabilization of flutter phenomena of cantilevered pipes conveying fluid with constraints on input energy for control. The controller in this study is designed by using an algorithm which iteratively tunes the weighting matrix of the quadratic performance index in LQG problem. This controller design method takes the performance of the actuator into consideration. The theoretical and experimental results show that the effectiveness of the controller in stabilizing the flutter phenomena of cantilevered pipes conveying fluid varies according to the input variance constraints, i.e., the difference in the dynamic range of an actuator. Furthermore, the critical flow velocity at instability of the pipe can be estimated by the method stated in this paper, where the system loses its stability because of the restriction of control force produced by an actuator.

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Event date： 1997

Language：English  

This paper deals with a sensor/actuator placement problem in design of active vibration control systems for flexible structures. This problem is formulated as a minimization problem of the total energy which is defined as a sum of a kinetic and strain energy in a controlled structure with a constraint of control effort. The inequality constraint on the variance of the closedloop control effort is adopted to represent the capacity (dynamic range) of the actuator. Using a design algorithm which iteratively tunes the weighting matrix of the quadratic performance index in the LQG problem, the controller which meets these specifications can be synthesized. The optimal location of the sensor/actuator is determined by calculating the total energy for each candidate under several energy constraints of the control effort. The optimal placement of the sensor/actuator depends on the control energy constraint. Simulations and experiments for a cantilevered beam are conducted. These results of the optimization can be used as a guide to the design of active vibration control system.

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Event date： 1996

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Event date： 1996

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Language：English   Presentation type：Oral presentation (general)  

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Language：English  

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Language：English  

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Language：English  

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Language：English  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English  

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