• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.5 no.2
• /
• pp.169-174
• /
• 2005

A neural networks (NN) saturation compensation scheme for DC motor systems is presented. The scheme that leads to stability, command following and disturbance rejection is rigorously proved. On-line weights tuning law, the overall closed loop performance and the boundness of the NN weights are derived and guaranteed based on Lyapunov approach. The simulation and experimental results show that the proposed scheme effectively compensate for saturation nonlinearity in the presence of system uncertainty.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.11
• /
• pp.1095-1099
• /
• 2004

In this paper, a novel sliding surface is proposed to guarantee that the sliding mode controller for a second order system produces a control signal whose magnitude is always within the bound of input saturation. The proposed sliding surface uses a time-varying function, and its time derivative works to make a control signal within the bounds of input saturation. Simulation results are presented to show the effectiveness of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.50 no.7
• /
• pp.325-331
• /
• 2001

A dynamic anti-windup method for state delayed control systems with input saturation is considered. Under the assumption that a linear controller has been designed for a state delayed control system based on the existing design technique which shows desirable nominal performance, an additional compensator is incorporated to provide a graceful performance degradation despite of input saturation. By regarding the difference of the controller states in the absence and presence of input saturation as an objective function, the dynamic compensator which minimizes it is determined explicitly. The proposed dynamic compensator is the closed form of plant and controller parameters. The proposed method not only provides graceful performance degradation, but it also guarantees the total stability of resulting systems. An illustrative example is provided to show the effectiveness of the proposed method.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2000.10a
• /
• pp.377-386
• /
• 2000

Hybrid mass dampers consist of passive tuned mass dampers and active mass dampers. They have the advantage that passive tuned mass dampers are still operated even when active mass dampers are stopped by excessive disturbances or power failure. This paper begins first with the comparative analysis of tuned mass dampers, hybrid mass dampers, and active mass dampers. Next more detailed study is carried out on the hybrid mass dampers: cascade hybrid mass dampers (CHMD) and active tuned mass dampers (ATMD). CHMD is regarded as more reasonable device because of its lighter active mass than ATMD's. However CHMD can not neglect stroke saturation problem caused by the length limitation of active damper mass. We compensate the saturation problem with nonlinear restoring force. The restoring force is calculated based on the states and phases of active mass dampers and added to the control force. It is shown that the presented compensation method prevents CHMD from saturation behavior without apparent changes of control force and responses compared to those in case of not considering the saturation problem.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.8 no.2
• /
• pp.1-8
• /
• 2004

Sliding mode control (SMC), which is one of active control algorithms showing remarkable control performance, requires the excessive control force for control of seismically excited civil structures. Therefore, controller saturation should be considered in design of SMC. In this study, a method for determining the maximum control force is developed in terms of the fraction of the lateral restoring force using a design response spectrum. Numerical analyses of MDOF structures with one or multiple control devices verify the effectiveness of the proposed method for the control of seismically excited civil structures with saturation problem.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.6 s.52
• /
• pp.93-102
• /
• 2006

Control input's saturation of active control devices for large structures under large external disturbances are often occurred. It is more difficult to obtain the exact values of mass and stiffness as structures are higher. The modelling errors between mathematical models and real structures must be also included as parameter uncertainties. Therefore, in active vibration control of civil engineering structures like buildings and bridges, the robust saturation controller design method considering both control input's saturation and parameter uncertainties of system is needed. In this paper, stabilities of linear optimal controller LQR, modified bang-bang controller, saturated sliding mode controller, and robust saturation controller among various controllers which have been studied and applied to active vibration control of buildings are investigated. Especially, unstable phenomena of the LQR, the modified bang-bang controller and the saturated sliding mode controller when the control input is saturated or parameter uncertainties exist are presented to show the necessity of the robust saturation controller. The robust stability of the robust saturation controller are shown through a numerical example of a 2DOF linear vibrating system and an experimental test of the two-story structure with an active mass damper (AMD).

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.10
• /
• pp.1000-1006
• /
• 2007

This paper presents an LMI-based method to design a saturated state-feedback $H_2$ controller for uncertain systems with actuator saturation. Specifically, the paper proposes a sufficient condition such that the system under norm-bounded uncertainties and actuator saturation is asymptotically stable and the $H_2$-norm of the system has an upper-bound. The resulting condition is further utilized to solve a convex optimization problem specified in the context of $H_2$-norm minimization, whose solution yields a saturated $H_2$ controller. A numerical example is presented to show the effectiveness of the proposed method.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.9
• /
• pp.1648-1654
• /
• 2007

In this paper, we consider the design of $H_\infty$ high-gain state feedback control for time-delayed linear systems with limited actuator capacities. The high-gain control means that the control permits the predetermined degree of saturation. Based on new Lyapunov-Krasovskii functional, we derive a result in the form of matrix inequalities. The matrix inequalities are consisted of LMIs those confirm the positive definiteness of Lyapunov- Krasovskii functional, satisfaction of predetermined degree of saturation, reachable set and $L_2$ gain constraint. The result is dependent on the bound of time-delay and its rate, predetermined degree of saturation, actuator capacity, and the allowed size of disturbances. Finally, we give a numerical example to show the effectiveness and usefulness of our result.

• Nuclear Engineering and Technology
• /
• v.53 no.11
• /
• pp.3685-3693
• /
• 2021

This paper presents a disturbance observer-based robust backstepping load-following control (DO-RBLFC) scheme for modular high-temperature gas-cooled reactors (MHTGRs) in the presence of actuator saturation and disturbances. Based on reactor kinetics and temperature reactivity feedback, the mathematical model of the MHTGR is first established. After that, a DO is constructed to estimate the unknown compound disturbances including model uncertainties, external disturbances, and unmeasured states. Besides, the actuator saturation is compensated by employing an auxiliary function in this paper. With the help of the DO, a robust load-following controller is developed via the backstepping technique to improve the load-following performance of the MHTGR subject to disturbances. At last, simulation and comparison results verify that the proposed DO-RBLFC scheme offers higher load-following accuracy, better disturbances rejection capability, and lower control rod speed than a PID controller, a conventional backstepping controller, and a disturbance observer-based adaptive sliding mode controller.

• Child Health Nursing Research
• /
• v.13 no.3
• /
• pp.299-307
• /
• 2007

Purpose: To investigate the effect of nonnutritive sucking(NNS) on the heart rate, oxygen saturation, and behavioral state of premature infants. Method: From December 15, 2004 to February 15, 2005, 20 premature infants hospitalized in the neonatal intensive care units were assigned to an experimental group (10), or a control group (10). Circular pacifiers for premature infants (Johnson, U.S.A.), which had been packed with $2{\times}2$ gauzes to create a vacuum, were used for 5 minutes, one hour after feeding for 5 days. Heart rates and oxygen saturation were checked every minute for 10 minutes once a day and behavioral states were monitored through video recording at the same time. Results: Changes in heart rate, oxygen saturation and behavioral state were found to show significant differences between the experimental group and the control group according to the point in time, and interactions were found between the group and the point of time. However, for behavioral state, no significant difference was found between the experimental group and the control group after the NNS was removed. Conclusion: From the results of this study it is possible to conclude that NNS is a positive intervention to bring about increased oxygen saturation and soothed behavioral state for premature infants.