• Proceedings of the KIEE Conference
• /
• 1998.11b
• /
• pp.423-425
• /
• 1998

Resonance effects and nonlinear frictions which generate many problems in control system exist in almost all the servo system. therefore, In this paper, the design procedure which employs $H_{\infty}$ control theory after augmenting with two integrators is proposed to track the ramp input. Limit cycles are unavoidable by the effect of interaction between two integrators and Coulomb friction in these system. The describing function is used to check the limit cycles and decide the coefficients of two integrators to minimize the effect of the limit cycles.

• Proceedings of the KIEE Conference
• /
• 1995.07b
• /
• pp.720-725
• /
• 1995

The most important problems which should be considered in designing servo controllers are resonance effects and nonlinear friction. These problems exist in almost all the servo systems, especially for the robotic maniplators and numerical control systems and cause difficulties in designing controllers. In this paper, controller design procedure which employs $H_{\infty}$ control theory is proposed for the servo systems with these problems. Sometimes, for these systems, there is a possibility of limit cycles due to the interation between the nonlinear friction and integrator. To check the possibility of limit cycles, describing fuction method is used.

• Proceedings of the KIEE Conference
• /
• 2001.07d
• /
• pp.1970-1972
• /
• 2001

This paper is concerned with the $H_{\infty}$ controller design of linear systems subject to time-delay in the state and saturating controls. The controller is derived from the matrix inequalities whish are obtained by minimizing the $L_{2}$ gain from the disturbance to the measured output, and this can be done by LMI control toolbox. An example is presented to show the usefulness of our result.

• Journal of Institute of Control, Robotics and Systems
• /
• v.22 no.6
• /
• pp.429-434
• /
• 2016

This paper introduces a stabilization condition for polynomial fuzzy systems that guarantees $H_{\infty}$ performance under the imperfect premise matching. An $H_{\infty}$ control of polynomial fuzzy systems attenuates the effect of external disturbance. Under the imperfect premise matching, a polynomial fuzzy model and controller do not share the same membership functions. Therefore, a polynomial fuzzy controller has an enhanced design flexibility and inherent robustness to handle parameter uncertainties. In this paper, the stabilization conditions are derived from the polynomial Lyapunov function and numerically solved by the sum-of-squares (SOS) method. A simulation example and comparison of the performance are provided to verify the stability analysis results and demonstrate the effectiveness of the proposed stabilization conditions.

• Journal of the Korea Convergence Society
• /
• v.8 no.5
• /
• pp.1-11
• /
• 2017

With a given spring-mass-damper system, $H_{\infty}$ and ${\mu}$-synthesis control methods are used to build system controllers which minimize vibrations at two major natural frequencies in two cases; without uncertainty; with 20% uncertainty. In order to check the stability and performance of two controllers, those are examined using GM and PM values. The signal strength of output responses is compared using the concept of central numerical differentiation and then results are quantified using the RMS method. Lastly, 40 random samples of $H_{\infty}$ and ${\mu}$-synthesis controllers are obtained for three different $W_{per\;f1}$ weighting functions and drawn in the time domain in order to compare the stability. Overall, ${\mu}$-synthesis controller manages the vibrations much better than $H_{\infty}$ controller according to the robust stability and performance values obtained by simulating random samples of 40 plant models.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.227-277
• /
• 2000

This paper presents an application of Mixed-Sensitivity H$_{\infty}$ control of a flexible manipulator. Firstly the detail model transfer function is derived from system identification. The objective is to position the free end of the beam with model including uncertainties and disturbance. we derive multiplicative uncertainties based on frequency response from difference between detail model and reduced model for designing controller. Finally we compare simulation results with experimental results.

• International Journal of Control, Automation, and Systems
• /
• v.5 no.3
• /
• pp.349-354
• /
• 2007

This paper considers the problem of designing static output feedback controllers for nonlinear systems represented by Takagi-Sugeno (T-S) fuzzy models. Based on linear matrix inequality technique, a new method is developed for designing fuzzy stabilizing controllers via static output feedback. Furthermore, the result is also extended to $H_{\infty}$ control. Examples are given to illustrate the effectiveness of the proposed methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1994.10a
• /
• pp.165-169
• /
• 1994

This paper describes the vibration control of a cantilever beam that is reformulated as the sensitivity minimization problem and solved in H$_{\infty}$ controller that is studied widely nowadays. The result of suggested controller is compared with that special form of H$_{2}$ controller, i.e., LQG. Piezoelectric actuator is chosen and disturbance is applied in the form of base excitation to match real aeronautical problems. Simulations are given, whose results reveals the performance of suggested controller is better than LQG in many cases.

• 제어로봇시스템학회:학술대회논문집
• /
• 1993.10b
• /
• pp.339-344
• /
• 1993

An H$_{\infty}$ control system design for a magnetic levitation system is presented. In the control system design, we consider the influence of both disturbances and uncertainties in the model. The main disturbances stem from the position sensors.The uncertainties are divided into electromagnetic and mechanical ones: the former are due to the gain change in the current amplifier, the influence of leakage flux and modelling error in the magnetic circuit and the latter are due to the changes of the mass and the moments of inertia of the vehicle. Therefore, the designed controller is indispensable to guarantee the robustness of this system for both stability and performance. The controller design is based on the standard H$_{\infty}$ optimal control problem. As the novel features in this paper :(1) there are two poles on j.omega.-axis in the control model;(2) an integrator is included in the controller so that equivalently there are three poles on j.omega.-axis in the model. Finally, several experiments and simulations are carried out to verify the high performance and robustness of the designed control system.m.

• 제어로봇시스템학회:학술대회논문집
• /
• 1992.10a
• /
• pp.754-759
• /
• 1992

In this paper, we proposed a mixed H$_{2}$/H$_{\infty}$ optimal controller design method using the parameterization of H$_{2}$ suboptimal controller. The method is based on the minimization of H$_{2}$ performance measure with an H$_{\infty}$-norm constraint. We also derived the necessary and sufficient conditions for existence of solution from the decoupled Riccati equations. And the designed controller has state-space representation.n.