• International Journal of Control, Automation, and Systems
• /
• v.2 no.2
• /
• pp.144-155
• /
• 2004

This paper addresses the issue of position control of a chain of multiple mass-spring-damper (CMMSD) units which can be found in many physical systems. The dynamic model of a CMMSD system with any degrees of freedom is expressed in a closed-form for the convenience of the controller design. Backstepping and model reference adaptive control (MRAC) approaches are then used to develop two adaptive output feedback controllers to control the position of a CMMSD system. The proposed controllers rely on the measurements of the input (force) and the output (position of the mass unit at the end of the chain) of the system without the knowledge of its parameters and internal states. Simulations are used to verify the effectiveness of the controllers

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.1
• /
• pp.1-5
• /
• 2007

Many nonlinear controllers for the power system are based on nonlinear models involving the power angle as an element of the state, and therefore the reference value for the power angle is needed. As this reference value is not generally available, it is difficult to apply such nonlinear control methods in practice. To deal with this problem, we present an input-output feedback linearizing control scheme by selecting the output as a combination of the squared voltage and the relative frequency. It is shown that the internal dynamics are locally stable with controllable damping, and that the frequency remains bounded for all time. Simulations illustrate the effectiveness of the proposed method.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.47.1-47.1
• /
• 2019

A gas giant formed in a massive protoplanetary disk via gravitational instability migrates inward due to its gravitational interaction with the disk. Planet migration occurs in various ways depending on the disk structure and internal processes, but previous studies only considered quantitative radiative feedback resulting from mass accretion onto the planet. Allowing for accretion feedback, we perform three-dimensional hydrodynamic simulations with GIZMO to investigate orbital evolution of giant planets in a protoplanetary subject to -cooling. This work shows a planet gains mass due to accretion and gradually opens a gap as it moves inward. The migration in the end halts when the planet clears the gas around its orbit. A more massive planet grows its mass faster and migrates more rapidly, stalling at an orbit farther away from the protostar. Models with a cold disk readily construct a circumplanetary disk and result in high mass growth of the planet. Accretion feedback, in general, reduces the rate of the planet growth and delays migration. We discuss our results with GIZMO in comparison with the previous results with different codes.

• Journal of Korean Academy of Nursing Administration
• /
• v.9 no.3
• /
• pp.495-505
• /
• 2003

Purpose: The purpose of this study was to develop 360 feedback for nursing unit manager based on the current personnel evaluation system and to evaluate the new tool according to evaluation subjects. Total of 277 subjects of nurse unit managers and staff nurses were participated in this study. Method: The study was conducted in three phases each for development, application, and analysis of 360 feedback. SAS program was utilized for data analysis with descriptive statistics, t-test, and analysis of variance. Result: The evaluation criteria of the developed 360 feedback tool consisted of 13 subscales such as professional knowledge, apprehension & judgement, job performance, applicability, creativity, leadership, responsibility, promptness & accuracy, administrative ability & sense of mission, activeness, cooperation, communicability, and general attitude. The internal consistency of the tool was Cronbach's alpha .939. The evaluation score by! peers(M=4.30) was the highest one, followed by self-evaluation(M=4.23), evaluation by supervisor(M=4.17), and evaluation by subordinate(M=4.10). The differences in the total evaluation scores among the subjects supervisor, self, peer, and subordinate were not statistically significant, but significant differences were found in some subscales scores. Conclusion: Further research is required to test the reliability and validity of the $360^{\circ}$ feedback tool, and to test the outcome and the process of $360^{\circ}$ feedback system.

• Journal of the Optical Society of Korea
• /
• v.17 no.2
• /
• pp.177-181
• /
• 2013

We present an all-fiberized power-scalable, sub-nanosecond mode-locked laser based on a frequency-shifted-feedback ring cavity comprised of an erbium-doped fiber, a downshifting acousto-optic modulator (AOM), and a bandpass filter (BPF). With the aid of the frequency-shifted feedback mechanism provided by the AOM and the narrow filter bandwidth of 0.45 nm, we generate self-starting, mode-locked optical pulses with a spectral bandwidth of ~0.098 nm and a pulsewidth of 432 to 536 ps. In particular, the output power is readily scalable with pump power while keeping the temporal shape and spectral bandwidth. This is obtained via the consolidation of bound pulse modes circulating at the fundamental repetition rate of the cavity. In fact, the consolidated pulses form a single-entity envelope of asymmetric Gaussian shape where no discrete internal pulses are perceived. This result highlights that the inclusion of the narrow BPF into the cavity is crucial to achieving the consolidated pulses.

• Structural Engineering and Mechanics
• /
• v.16 no.3
• /
• pp.327-340
• /
• 2003

Variations in system parameters due to uncertainties of parameters may result in system performance deterioration and create system internal stability problems. Uncertainties in structural modeling of structures are often considered to ensure that the control system is robust with respect to response errors. So the uncertain concept plays an important role in the analysis and design of the engineering structures. In this paper, the active control of the intelligent structures with the uncertainties is studied and a new method for analyzing the robustness of systems with the uncertainties is presented. Firstly, the system with uncertain parameters is considered as the perturbation of the system with deterministic parameters. Secondly, the feedback control law is designed on the basis of deterministic system. Thirdly, perturbation analysis and robustness analysis of intelligent structures with uncertainties are discussed when the feedback control law is applied to the original system and perturbed system. Combining the convex model of uncertainties with the finite element method, the analysis theory of the robustness of intelligent structures with the uncertainties can be developed. The description and computation of the robustness of intelligent structures with uncertain parameters is obtained. Finally, a numerical example of the application of the present method is given to show the validity of the method.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.4
• /
• pp.811-818
• /
• 2016

A continuous fine-tuning phase locked loop with an additional negative feedback loop has been proposed. When the phase locked loop is out-of-lock, the phase locked loop has a fast locking characteristic using the continuous band-selection loop. When the phase locked loop is near in-lock, the bandwidth is narrowed with the fine loop. The additional negative feedback loop consists of a voltage controlled oscillator, a frequency voltage converter and its internal loop filter. It serves a negative feedback function to the main phase locked loop, and improves the phase noise characteristics and the stability of the proposed phase locked loop. The additional negative feedback loop makes the continuous fine-tuning loop work stably without any voltage fluctuation in the loop filter. Measurement results of the fabricated phase locked loop in $0.18{\mu}m$ CMOS process show that the phase noise is -109.6dBc/Hz at 2MHz offset from 742.8MHz carrier frequency.

• The Korean Journal of Health Service Management
• /
• v.6 no.2
• /
• pp.111-119
• /
• 2012

The purpose of the study were to investigate the effect of the neuro-feedback program which improves brain function and stress reduction effect. The research design is one group pretest-posttest survey. 121 nursing students of a college in the Busan region took part in the study. Training involving the neuro-feedback program was conducted twice a week, 30 minutes per session, for a total of 10 weeks. The collected data was encoded and analyzed using SPSS 12.0 Version. The brain function and stress levels of the subjects were analyzed through the before-and-after results of the training were analyzed using a paired t-test. The results of the study showed that the BQ and SQ were enhanced as a result of the neuro-feedback. In particular, there were significant increases in the SRQ, ATQ, ACQ, and EQ of the BQ. SQ is correlated with the prevalence rate and resistance to disease, meaning not only psychological anxiety, uneasiness and excitement, but also physical anxiety and response to disease. Based on the study, by using the neuro-feedback training as a program for stress reduction, it is expected that nursing students will receive less stress from internal and external factors, and their ability to cope with stress will be enhanced.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.27 no.2
• /
• pp.195-203
• /
• 2017

This paper is concerned with the active vibration control of shell structure that is subjected to internal unbalanced excitation by using active mounts and accelerometers. The unbalanced excitation is caused by a rotating unbalanced mass. The control algorithm considered in this study is the negative acceleration feedback (NAF) control. A simplified dynamic model was derived to verify the effectiveness of the NAF control. Four actuators and four accelerometers were mounted on the shell structure, so that the multiple-input and multiple-output (MIMO) NAF controller was designed by both centralized and decentralized ways. Numerical results show that both the decentralized and centralized NAF controllers are effective. Based on the numerical simulation, the proposed decentralized NAF controller was applied to the real shell structure. Experimental results show that the proposed decentralized NAF controller can effectively suppress vibrations of the shell structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.643-648
• /
• 2003

The problem considered in this paper is that the tip position of a flexible cantilever beam is controlled to follow a command signal, using a pair of piezoelectric actuators at the clamped end. The beam is lightly damped and so the natural transient response is rather long, and also since the sensor and actuator are not collocated, the plant response is non-minimum phase. Two control strategies were investigated. The first involved conventional PID control in which the feedback gains were adjusted to give the fastest closed-loop response to a step input. The second control strategy was based on an internal model control (IMC) architecture. The control filter in the IMC controller was a digital FIR device designed to minimize the expectation of the mean square tracking error. The IMC controller designed fur the beam was found to have very much reduced settling times to a step input compared with those of the PID controller.