• Journal of Institute of Control, Robotics and Systems
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• v.2 no.2
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• pp.81-87
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• 1996

Time delay control(TDC) law has been recently suggested as an effective control technique for nonlinear time-varying systems with uncertain dynamics and/or unpredictable disturbances. This paper focuses on the applications of the TDC algorithm to torque control of an engine system and speed control of an engine/automatic transmission system. Through the stability analysis of the engien system based on TDC, determination of the appropriate time delay and control factor is investigated. It was revealed that the size of time delay of the TDC law should be greater than that of transport delay of the system for both stability and better control performance. Simulation and experimental results for the engine torque control and engine/automatic transmission speed control systems show both relatively good command following and disturbance rejection properties. However, TDC controller shows rather slow responses when applied to the system with large transport delay.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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• pp.379-384
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• 1999

In this paper, we present a new time-varying sliding surface to achieve fast and robust tracking of higher-order uncertain systems. The surface passes through an initial error, and afterwards, it moves towards a predetermined target surface by means of a variable named by sliding surface gain and its intercept. Specifically, the sliding surface gain is determined so that its initial value can minimize a shifting distance of the surface and that the system roots in sliding mode can follow certain stable trajectories. The designed sliding mode control forces the system errors to stay always on the proposed surface from the beginning. By this means, the system remains insensitive to system uncertainties and disturbances for the whole time. To illustrate the effectiveness of the proposed method, the comparative study with conventional time-invariant sliding mode control is performed.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.12
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• pp.41-49
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• 1997

This paper deals with the attitude control of a self-made VTOL vehicle which is round shape and has four fans and motors. Although hovering mechanisms are suitable for field work at a mountainous region or a building site etc., it is known that modeling the structure of the plant is quite difficult due to its unstable or uncertain characteristics. So, a robust controller is requried in order to cope with these uncertainties. WE first model the structure of the plant under the actual hovering setting and then determine the uncertainty of the acquired mathematical model by using system identification method as exactly as possible. We adopt the $H^{\infty}$ theory as a control algorithm because of its availability, and the structure of two-degree-of-freedom is used as a basic feedback control system to improve the transient response of the plant. Finally, we show the appropriateness of the designed controller through simulations and experiments. That is, the proposed VTOL system is able to maintain its roubust performance in spite of parameter variations and existing disturbances..

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.759-766
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• 2003

The amount of container freight continuously has been increased. and the low efficiency of container crane causes jamming frequently in transportation and cargo handling at port. The conventional control techniques based on a mathematical model are not well suited for dealing with ill-defined and uncertain systems. Recently. Fuzzy control has been successfully applied to a wide variety of practical problems as robots. automatic train operation system. etc. In this paper. a fuzzy controller for container crane is proposed to accomplish a design of improved control system for minimizing the swing motion at destination. In this scheme a mathematical model for the system is obtained in state space form. Finally. to exhibit the tracking performance and robustness of the proposed controller. computer simulations were carried out with various references, parameter variations and disturbances.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.78-86
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• 2002

In this paper, LMI (Linear Matrix Inequality) based on H$\_$$\infty$/ controller for a lire of sight (LOS) stabilization system. It shows that the proposed controller has more excellent stabilization performance than that of the conventional PI-Lead controller. An H$\_$$\infty$/ control has been also applied to the system for reducing modeling errors and the settling time of the system. The LMI-based H$\_$$\infty$/ controller design is more practical in view of reducing a run-time than Riccati-based H$\_$$\infty$/ controller. This H$\_$$\infty$/ controller is available not only to decrease the gain in PI-Lead control, but also to compensate the identifications for the various uncertain parameters. Therefore, this paper, shows that the proposed LMI-based H$\_$$\infty$/ controller had good disturbance attenuation and reference input tracking performance compared with the control performance of the conventional controller under any real disturbances.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.92-94
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• 2007

This paper considers an optimal control problem for a remote control to an electrical drive system with a DC motor. Since it is a linear control system with time-delay subject to unknown but bounded disturbance, we construct a worst-case feedback control policy. This policy can guarantee that, for all admissible uncertain disturbances, the real system state should be in a prescribed neighborhood of a desired value, and the cost functional takes the best guarantee value. The worst-case feedback control policy is allowed to be corrected at one correction point between the initial to the final time, which is equivalent to solving a 1-level min-max problem. Since the min-max problem at the stage does not yield a simple analytical solution, we consider an approximate control policy, which is equivalent and can be solved explicitly m the numerical experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.9
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• pp.1368-1375
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• 1993

This paper deals with the decentralized robust adaptive controller design for large-scale interconnected systems. We consider an arbitrary interconnection of subsystems with unkown parameters and bounded disturbances. When the disturbance and uncertain interconnections are present, the stability of the controlled large scale system is ensured if there exists a positive definite M-matrix which is related to the bound of the interconnections. The possible bound of the interconnections is assumed to be known Pth order polynomials for the decentralized adaptive controller. A modified adaptive law is proposed guaranteeing the existence of a region of attraction from which all signals converge to a residual set Do, which contains the equilibrium.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.444-444
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• 2000

For a class of nonlinear systems which satisfy a certain condition so called output feedback exponential passivity (OFEP), it is well known that one can easily design a high-gain output feedback control system. The designed high-gain controller has simple structure and high robustness. However, from the viewpoint of practical application, it is important to consider a robust control scheme for controlled systems for which some of the assumptions of output feedback stabilization are not valid. In this paper. we deal with a design problem of the robust high-gain adaptive output feedback control for the above-mentioned class of nonlinear systems with uncertain nonlinearities and/or disturbances.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.12
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• pp.48-58
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• 2010

In this study, position tracking and force reflection control of a master-slave manipulator which will be used for handling objects contaminated by radioactivity has been addressed. Since available measurements concerning on dynamic motion of the master-slave manipulator are restricted, a simple constrained control structure was suggested. In the consideration of the uncertain dynamic behaviors of the slave manipulator which is dependent upon mass and shape of work pieces grasped and dynamic properties of the environment contacted, a simple structured sliding mode control was suggested to guarantee robustness with respect to parameter uncertainties and external disturbances. The proposed control was applied to a 1-DOF master-slave link system. The control performances were verified along with some computer simulation results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.391-395
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• 1996

This paper presents a robust force tracking control of a small-sized SMA gripper with two fingers using shape memory alloy(SMA) actuators. The mathematical governing equation of the proposed system is derived by Hamilton's principle and Lagrangian equation and then, the control system model is integrated with the first-order actuator dynamics. Uncertain system parameters such as time constant of the actuators are also included in the control model. A robust two degree of freedom(TDF) controller using H$_{\infty}$ control theory, which has inherent robustness to model uncertainties and external disturbances, is adopted to achieve end-point force tracking control of the two-finger gripper. Force tracking control performances for desired trajectories represented by sinusoidal and step functions are evaluated by undertaking both simulation and experimental works.