• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.680-684
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• 1998

This paper presents an efficient method which estimates the systems with unmodeled dynamics using D-L networks. This method is applied for estimating the system with unmodeled dynamics from only input-output information , so it can exclude additional procedure for system description and reduce the computational burden required for real-time estimation. Higher convergence speed is achieved in this manner in comparison with widely-used conventional methods.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.9-16
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• 1997

The method of designing robust two degree of freedom(2 DOF) controllers for linear systems with parameter uncertainties and unmodeled dynamics is presented in this paper. Robust performance condition that accounts for robust model matching of closed loop system and disturbance rejection is derived. Using the robust performance condition, the feedback controller is designed to meet robust stability and disturbance rejection specifications, while prefilter is used to improve the robust model matching properties. The $H^{\infty}$ and $\mu$ controller for six degree of freedom vehicle with parameter variations are designed and compared. Simulations for hydrodynamic parameter variations and disturbance are presented to demonstrate the achievement of good robust performance.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.113-115
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• 1997

This paper presents an efficient method which can estimate the system with unmodeled dynamics using D-L networks. The proposed method is to estimate system with unmodeled dynamics recursively from only input-output information, which can exclude additional procedure for system description and thus reduce the required computational burden for real-time estimation. Higher convergence speed is achieved with our manner when compared with widely-used conventional methods.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.66-71
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• 2017

In this paper, we study the robustness of disturbance observer based controller for DC motor in the presence of unmodeled dynamics. It is well known that the robustness property usually becomes weaker as the control gain becomes larger. On the contrary to this expectation, it is shown that the phase margin of DOB controller remains quite a large value even though the time constant of Q-filter becomes smaller. The computer simulation results show that DOB controller is able to stabilize the motor system even in the presence of unmodeled dynamics. On the contrary, the unity-feedback system fails to maintain stability when a high gain feedback is employed for the purpose of achieving better disturbance attenuation performance.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.4
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• pp.298-306
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• 1989

Robustness of adaptive pole-placement control against unmodeled dynamics is proved. This proof is done by showing that the sufficient condition for robustness, conic condition and stability of a specific operator, is satisfied for a larger set of unmodeled dynamics. The simulation results show the proposed method is quite powerful. And the difference between the concept of the pseudoplant control and the known internal model control is shown by the closed loop analysis.

• International Journal of Control, Automation, and Systems
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• v.1 no.1
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• pp.54-67
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• 2003

In this paper, a novel estimation technique for a robust adaptive control scheme is presented for a class of uncertain nonlinear systems with a general set of uncertainty. For a class of introduced more extended semi-strict feedback forms which generalize the systems studied in recent years, a novel estimation technique is proposed to estimate the states of the fully nonlinear unmodeled dynamics without stringent conditions. With the introduction of powerful functions, the estimation error can be tuned to a desired small region around the origin via the estimator parameters. In addition, with some effective functions, a modified adaptive backstepping for dynamic uncertainties is presented to drive the output to an arbitrarily small region around the origin by an appropriate choice of the design parameters. With our proposed schemes, we can remove or relax the assumptions of the existing results.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.353-356
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• 1991

This paper proposes a robust direct adaptive control system implementation using a 80286 microprocessor-based system for controlling the speed of a DC servo motor. In this paper, assuming that the unmodeled dynamics of the plant are sufficiently small in the low-frequency range, the plant as linear time-invariant system is the second relative degree, we construct the direct adaptive control system with the algorithm considering plant unmodeled dynamics and execute the experiment, and compare the characteristics with those of PI algorithm's. It shows that an easy implementation of the built controller is due to the usage of software for the algorithm.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.9
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• pp.1322-1331
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• 1989

This paper proposes a new adaptation algorithm with which a model reference adaptive control can give a local boundedness of the tracking error applied to a continuous-time linear time-invariant single-input single-output plant whose reduced-order model is of relative degree 1 and whose unmodeled dynamics may be represented in a sigular perturbation form. With the addition of an offset term and an extra adaptation structure, this algorithm is shown to have a robustness property in the sense that this gives zero residual tracking errors when the unmodeled dynamics are disappeared.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.373-375
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• 1993

In this paper we deal with the design and implementation problem of a robust adaptive controller for a direct drive manipulator with unmodeled dynamics. The proposed controller ensures that the closed loop system is stable and output errors are converged to some boundary. To validate the improved performance of the proposed controller experimental results are presented in this paper.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.54.2-54
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• 2001

In this paper two control strategies, command shaping control and optimal control, which aim to the reduction of the residual vibrations of the payload in a container crane system are investigated. Both control methods are open loop control. Due to unmodeled dynamics of the plant and disturbances like initial sway and wind, some residual sway always exists at the end of trolley movement. Command inputs are designed to achieve the control objectives including minimal residual vibration and robustness in the presence of unmodeled dynamics. Simulation results of various command inputs are compared in terms of arrival time, residual sway angle, robustness, and maximum sway distance during the traveling. Command shaping method provides a more competent tool than optimal control.