• Structural Engineering and Mechanics
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• v.67 no.1
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• pp.33-43
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• 2018

The dynamic output-feedback robust control method based on linear matrix inequality (LMI) method is presented for suppressing vibration response of a functionally graded material (FGM) beam with piezoelectric actuator/sensor layers in this paper. Based on the reduced model obtained by using direct mode truncation, the linear fractional state space representation of a piezoelectric FGM beam with material properties varying through the thickness is developed by considering both the inherent uncertainties in constitution material properties as well as material distribution and the model error due to mode truncation. The dynamic output-feedback robust H-infinity control law is implemented to suppress the vibration response of the piezoelectric FGM beam and the LMI method is utilized to convert control problem into convex optimization problem for efficient computation. In numerical studies, the flexural vibration control of a cantilever piezoelectric FGM beam is considered to investigate the accuracy and efficiency of the proposed control method. Compared with the efficient linear quadratic regulator (LQR) widely employed in literatures, the proposed robust control method requires less control voltage applied to the piezoelectric actuator in the case of same control performance for the controlled closed-loop system.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.400-405
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• 1990

This paper deals with the design technique of the controller for the discrete system control using Extended Safe Petri Net which is deduced from Petri Net as its subclass with a specific constraint and which is introduced to develop the design and analysis for the discrete systems. First, we propose a construction matrix suitable for the discrete systems that represent the marking flows which are the dynamic behavior of the discrete systems. Next, we develop a method that can design the controller for the discrete system control by analyzing the proposed construction matrix into the incidence matrix of Extended Safe Petri Net. Finally, the validity of the proposed method is shown by using the incidence matrix and matrix equation of Extended Safe Petri Net model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2554-2566
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• 1994

Robot position/force control has been a difficult task owing to the interaction between a robot and an environment with a rather high stiffness. In addition to the dynamic instability, the interaction causes the following problem : 1) chattering at steady-state, 2) dynamic coupling effect of robot, and 3) performance degradation due to a titled environment. To solve the problem, the Time Delay Control(TDC), which has been known to be quiet robust to plant uncertainties and disturbances, has been applied. In conjunction to TDC, the following three ideas were also used : 1) To reduce the amplitude of the chattering at the steady state, a novel scheme was adopted to enhance the resolution type solution of A/D conversion for the force sensor. 2) To reduce the dynamic coupling, a trajectory type position command was tried on a comparative basis to the step command, as well as a more accurate mass matrix was used instead of the constant mass matrix. 3) And finally to improve the performance in the tilted environment, force derivatives instead of position derivatives were used in the TDC law. Computer simulations and experiments resulted in obvious improvements on the quality of the hybrid control, thereby clearly demonstrating the effectiveness of TDC with the proposed ideas.

• International Journal of Control, Automation, and Systems
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• v.6 no.1
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• pp.24-34
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• 2008

A novel neural network model, termed the standard neural network model (SNNM), similar to the nominal model in linear robust control theory, is suggested to facilitate the synthesis of controllers for delayed (or non-delayed) nonlinear systems composed of neural networks. The model is composed of a linear dynamic system and a bounded static delayed (or non-delayed) nonlinear operator. Based on the global asymptotic stability analysis of SNNMs, Static state-feedback controller and dynamic output feedback controller are designed for the SNNMs to stabilize the closed-loop systems, respectively. The control design equations are shown to be a set of linear matrix inequalities (LMIs) which can be easily solved by various convex optimization algorithms to determine the control signals. Most neural-network-based nonlinear systems with time delays or without time delays can be transformed into the SNNMs for controller synthesis in a unified way. Two application examples are given where the SNNMs are employed to synthesize the feedback stabilizing controllers for an SISO nonlinear system modeled by the neural network, and for a chaotic neural network, respectively. Through these examples, it is demonstrated that the SNNM not only makes controller synthesis of neural-network-based systems much easier, but also provides a new approach to the synthesis of the controllers for the other type of nonlinear systems.

• International Journal of Control, Automation, and Systems
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• v.6 no.2
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• pp.149-159
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• 2008

This paper considers the problem of adaptive fault-tolerant guaranteed cost controller design via dynamic output feedback for a class of linear time-delay systems against actuator faults. A new variable gain controller is established, whose gains are tuned by the designed adaptive laws. More relaxed sufficient conditions are derived in terms of linear matrix inequalities (LMIs), compared with the corresponding fault-tolerant controller with fixed gains. A real application example about river pollution process is presented to show the effectiveness of the proposed method.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.418-429
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• 2018

This paper studies the decentralized position/force control problem for constrained reconfigurable manipulator without torque sensing. A novel joint torque estimation scheme that exploits the existing structural elasticity of the manipulator joint with harmonic drive model is applied for each joint module. Based on the estimated joint torque and dynamic output feedback technique, a decentralized position/force control strategy is presented. In order to solve the problem of controller parameter perturbation, the non-fragile robust technique is introduced into the dynamic output feedback controller. Subsequently, the stability of the closed-loop system is proved using the Lyapunov theory and linear matrix inequality (LMI) technique. Finally, two 2-DOF constrained reconfigurable manipulators with different configurations are applied to verify the effectiveness of the proposed control scheme in numerical simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.9
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• pp.846-852
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• 2013

In this paper, the authors propose a new approach to control problem of the marine vessels which are moored or controlled by actuators. The vessel control problem in the specified area is called a DPS (Dynamic Positioning System). The main objective of this paper is to obtain more useful control design method for DPS. In this problem, a complicate fact is control allocation which is a numerical method for distributing the control signal to the controlled system. For this, many results have been given and verified by other researchers using two individual processes. It means that the controller design and control allocation design process are carried out individually. In this paper, the authors give more sophisticated design solution on this issue. In which the controller design and control allocation problem are unified by a robust controller design problem. In other word, the stability of the closed-loop system, control performance and allocation problem are unified by an LMI (Linear Matrix Inequality) constraint based on $H_2/H_{\infty}$ mixed design framework. The usefulness of proposed approach is verified by simulation with a supply vessel model and found works well.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.82-87
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• 1994

In this study, dynamic optimal design far a two degree-of-freedom anthropomorphic robot module is performed. Several dynamic design indices associated with the inertia matrix and the inertia power array are introduced. Analysis for the relationship between the dynamic parameters and the design indices shows that trade-offs exist between the isotropy and the dynamic design indices related to the actuator size. A composite design index is employed to deal with multi-criteria based design with different weighting factors, in a systematic manner. We demonstrate the fact that dynamic optimization is another significant step to enhance the system performances, followed by kinematic optimization.

• Journal of Ocean Engineering and Technology
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• v.26 no.3
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• pp.20-25
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• 2012

In this paper, the authors propose a new approach to the control problem of marine vessels that are moored or controlled by actuators. The vessel control system is basically based on Dynamic Positioning System (DPS) technology. The main object of this paper is to obtain a more useful control design method for DPS. In this problem, the control allocation is a complication. For this problem, many results have been given and verified by other researchers using a two-step process, with the controller and control allocation design processes carried out individually. In this paper, the authors provide a more sophisticated design solution for this issue. The authors propose a new design method in which the controller design and control allocation problems are considered and solved simultaneously. In other words, the system stability, control performance, and allocation problem are unified by an LMI (linear matrix inequality) based on control theory. The usefulness of the proposed approach is verified by a simulation using a supply vessel model.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.11
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• pp.895-900
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• 2005

We derive a linear matrix inequality(LMI) condition guaranteeing that any invariant zeros of a triple (A, B, C) lie in the open left half plane of the complex plane, i.e. $C(sI-A)^{-1}B$ is minimum phase. The LMI condition is equivalent to a certain constrained Lyapunov matrix equation which can be found in many results relating to stability analysis or control design. We show that the LMI condition can be used to simplify various control engineering problems such as a dynamic output feedback control problem, a variable structure static output feedback control problem, and a nonlinear system observer design problem. Finally, we give some numerical examples.