• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.4
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• pp.129-136
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• 2002

This paper presents a $H_{\infty}$ robust controller with parameter estimation in polynomial approach. For good performance of a uncertain system, the parameters are estimated by RLS algorithm. The controller minimizes the sum of $H_{\infty}$ norm between sensitivity function and complementary sensitivity function by employing the Youla parameterization and polynomial approach at the same time. A numerical example and its simulation results are given to show the validity of the proposed controller.

• Journal of Power System Engineering
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• v.7 no.4
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• pp.38-43
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• 2003

This paper proposes an optimum design problem of structural and control systems. taking a 3-D truss structure as an example. The structure is supposed to be subjected to initial static loads and time-varying disturbances. The structure is controlled by a state feedback $H_{\infty}$ controller to suppress the effect of the disturbances. The design variables are the cross sectional areas of truss members. The structural objective function is the structural weight. As the control objective, we consider two types of performance indices. The first function represents the effect of the initial loads. The second one is the norm of the feedback gain. These objective functions are in conflict with each other. Then, first, two control objective functions are transformed into one control objective by the weighting method. Next, the structural objective is treated as the constraint. By introducing the second control objective which considers the magnitude of the feedback gain, we can per limn the design which is robust in modeling errors.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.3
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• pp.41-49
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• 1999

In this paper, we design a controller using the $\mu$-synthesis method and apply it for the spring-mass system with noncollocated sensors and actuators. We assume that the values of the spring stiffness and load mass of the plant are uncertain. The plant is modeled with parametric uncertainty by using the state space equation, especially the descriptor form. The $H_\infty$ controller designed by the $\mu$-synthesis method is compared with the standard $H_\infty$ controller To compare performances of two $H_\infty$ controllers, it is assumed that both controllers were designed with same weighting functions except that the $\mu$-synthesis controller has structured uncertainties. By compared with the standard $H_\infty$ controller, we show that the designed controller has satisfactory robust performance as well as robust stability by simulations and experiments.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.11
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• pp.868-873
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• 2003

$H_{\infty}$ control has been applied to the design of practical control systems widely because of its robustness. It can minimize $H_{\infty}$ norm of the transfer function between the desired output and the disturbances. The SMC(Sliding Mode Control) is more robust and give the better performance than the $H_{\infty}$ control if the matching condition is satisfied. A controller which can have the advantages of $H_{\infty}$ control and the SMC is proposed to add the robustness of the SMC to the $H_{\infty}$ controller. Its design is based on the augmented system of which dynamics have one higher order than that of the original system and has the same dynamic as the desired system in spite of uncertainties. The dynamic of proposed sliding surface is the same dynamic as the system controlled by $H_{\infty}$ controller without the uncertainties which satisfy the matching condition.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.284-287
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• 2001

This paper presents the robust control simulation of a composite beam using self-sensing actuators(SSA). The self-sensing actuator is a new concept for intelligent material, where a single piezoelectric element simultaneously functions as both a sensor and an actuator. In a practical implementation of the self-sensing actuator an electrical bridge circuit is used to measure strain. The circuit could provide significant information about strain in the element if it were well-balanced. Our aim is design a robust controller which guarantees that the performance of a self-sensing actuator is robust against perturbation of the bridge balance and to confirm the advantages of this technique. Simulation results show that the self-sensing actuator driven by the designed controller exhibits excellent performance in suppressing the vibration of a composite beam.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.496-499
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• 2002

The LQG/LTR controller is a robust and stable control which is systematic method with a view of engineering. And the H$^{\infty}$ scheme is adopted for the design of the controller to reduce the effects of the disturbances. In this paper, LQG/LTR and H$^{\infty}$ Controller Design of Lateral Control System for an Automobile is developed with 3 DOF (degree-of-freedom) model. The performance has been compared for the employed two types of controllers via computed simulations. The results show that the H$^{\infty}$ controller provides more robustness property for the disturbances and lower control input.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.318-321
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• 2002

The LQG/LTR controller is a robust and stable control which is systematic method with a view of engineering. And the H$^{\infty}$ scheme is adopted for the design of the controller to reduce the effects of the disturbances. In this paper, LQG/LTR and H$^{\infty}$ Controller Design of Lateral Control System for an Automobile is developed with 3 DOF (degree-of-freedom) model. The performance has been compared for the employed two types of controllers via computed simulations. The results show that the H$^{\infty}$ controller provides more robustness property for the disturbances and lower control input.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2191-2193
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• 2004

The Sliding Mode Control is more robust and give the better performance than the $H_{\infty}$ control if the matching condition is satisfied. So in this paper, a controller which can have the advantages of $H_{\infty}$ control and the SMC is proposed to add the robustness of the SMC to the $H_{\infty}$ controller. The dynamic of proposed sliding surface is the same dynamic as the system controlled by $H_{\infty}$ controller without the uncertainties which satisfy the matching condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.1899-1909
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• 2000

This paper proposes a new $H_{\infty}$ yaw moment control scheme using brake torque switching for improving vehicle performance and stability especially in high speed driving. In the scheme, one wheel is selected, depending on the vehicle states, at which a brake torque for control is applied. Steering angles are modeled as a disturbance to the system and the $H_{\infty}$ controller is designed to minimize the difference between the performance of the vehicle and that of the desired model. Its performance robustness as well as stability robustness to system parameter variations is assured through ${\mu}$-analysis. Various simulations with a nonlinear 8-DOF vehicle model show that proposed controller enhances the vehicle performance and stability under disturbances and parameter variations as well as under the normal driving condition.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.4
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• pp.264-269
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• 2002

In this paper, Η$_{\infty}$ depth and course controller of an AUV(Autonomous Underwater Vehicle) using Η$_{\infty}$ servo control is proposed. The Η$_{\infty}$ servo problem is formulated to design the controllers satisfying a robust tracking property with modeling errors and disturbances. The solution of the Η$_{\infty}$ servo problem is as fellows: first, this problem is modified as an Η$_{\infty}$ control problem for the generalized plant that includes a reference input mode, and then a sub-optimal solution that satisfies a given performance criteria is calculated by LMI(Linear Matrix Inequality) approach. The Η$_{\infty}$ depth and course controller are designed to satisfy with the robust stability about the modeling error generated from the perturbation of the hydrodynamic coefficients and the robust tracking property under disturbances(wave force, wave moment, tide). The performances of the designed controllers are evaluated with computer simulations, and finally these simulation results show the usefulness and application of the proposed Η$_{\infty}$ depth and course control system.