• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.80-83
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• 1999

The windup phenomenon appears and results in performance degradation such as large overshoot, slow settling time when the integral-proportional (IP) controller output is saturated. An anti-windup IP controller is proposed to improve the control performance for the motor drives. The proposed algorithm is applied to the current control of a vector-controlled induction motor driven by a pulse width modulated(PWM) voltage-source inverter. The integral state is separately controlled corresponding to whether the IP controller output is saturated or not. The experimental results show that the current response has much improved performance such as little overshoot and fast settling time.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.2
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• pp.163-169
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• 2000

From the viewpoint of the cost effective design of power conversion systems, it is very important to fully u utilize the CillTent capacity of power devices over all circumstances. Therefore this paper deals with the l practical design of digital CillTent controller to meet the requirements of fast and overshoot free control r response over the varying control voltage bOlmds, the accompanied computational delay, and the system U W1certainties. The proposed controller consists of high gain PI control schemes using both the conditional i integrator and the modified delay compensator. The simulation and experimental results show the validity of t the proposed controller.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1696-1710
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• 2017

An improved Reactor Regulating System (RRS) logic architecture, which is combined with genetic algorithm (GA), is implemented in this work. It is devised to provide an optimal solution to the current RRS. The current system works desirably and has contributed to safe and stable nuclear power plant operation. However, during the ascent and descent section of the reactor power, the RRS output reveals a relatively high steady-state error, and the output also carries a considerable level of overshoot. In an attempt to consolidate conservatism and minimize the error, this work proposes to apply GA to RRS and suggests reconfiguring the system. Prior to the use of GA, reverse engineering is implemented to build a Simulink-based RRS model. Reengineering is followed to produce a newly configured RRS to generate an output that has a reduced steady-state error and diminished overshoot level. A full-scope APR1400 simulator is used to examine the dynamic behaviors of RRS and to build the RRS Simulink model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1362-1368
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• 2016

This paper proposes the improved transition scheme for a sensorless drive of an interior permanent magnet synchronous motor (IPMSM). In order to operate the IPMSM, the current controller can be used until 300 rpm for the initial operation. After that, the control method of IPMSM is changed to the speed controller for the sensorless control method. At that point, the rotor speed overshoot is generated due to the rapid change of the current reference for the speed controller. The proposed algorithm is able to reduce the overshoot of a rotor speed by compensating the estimated feedforward value to the speed controller. The feedforward value of the current reference is estimated by using a coordinate transformation and is approximated to the current reference after the transition of the control mode. The effectiveness of the proposed scheme is verified by experiments using an IPMSM drive system.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.336-340
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• 2001

In a digital system, there are inevitable delays in calculations and applying the inverter output voltages to the motor terminals. Because of the delays, the conventional predictive current controller implemented in the digital system has large overshoot and large harmonics. A new predictive current controller, considering the delays, for a permanent magnet synchronous motor (PMSM) is presented. The effectiveness and feasibilities are shown by experimental results.

• Journal of IKEEE
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• v.26 no.1
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• pp.124-128
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• 2022

Conventional LDO regulator external capacitors can reduce transient response characteristics such as overshoot and undershoot. However, the capacitorless LDO regulator proposed in this study applied body technology to the pass transistor to improve the transient response and provide excellent current drive capability. The operating conditions of the proposed LDO regulator are set to an input voltage that varies from 3.3V to 4.5V, a maximum load current of 200mA, and an output voltage of 3V. As a result of the measurement, it was found that when the load current was 100 mA, the voltage was 95 mV in the undershoot state and 105 mV in the overshoot state.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.10
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• pp.591-598
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• 2017

Power overshoot phenomenon was observed in microbial fuel cells (MFCs) used non-catalyzed graphite felt as cathode. Voltage loss in MFCs was mainly caused by cathode potential loss. Cheap stainless steel scrubber, which has high conductivity, and Pt/C coated graphite felt as cathode were used for overcoming power overshoot and reducing the cathode potential loss in MFCs. The MFCs used stainless steel scrubber showed no power overshoot even slow catholyte flow rate and produced 29% enhanced maximum current density ($23.9A/m^3$) than MFCs used non-catalyzed graphite felt while the power overshoot phenomenon was existed in Pt/C coated MFCs. Increasing catholyte flow rate resulted in disappearing power overshoot of MFCs used non-catalyzed graphite felt. In addition, maximum power density and current density of both MFCs used non-catalyzed graphite felt and stainless steel scrubber increased by 2-3.5 times. Cathode potential losses in all region of activation loss, ohmic loss, and mass transport loss were reduced according to increase of catholyte flow rate. Therefore, stainless steel scrubber has advantages that are economical materials as electrode and prevents power overshoot, leading to enhance electricity generation. In addition, increasing catholyte flux is one of great solution when power overshoot caused by cathodic overpotential is observed in MFCs.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.2
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• pp.18-25
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• 2008

The current display systems including TVs are going digital and large-sized, and high visual quality of those systems becomes a very important selling point in the current display system market. Thus, various researches have been carried out for enhancing the visual quality of digital display systems. One of the important digital image(or video) enhancement techniques is sharpness enhancement, and it is generally based on a transient improvement technique that reduces the edge transition time. However, this technique often generates overshoot and undershoot, which cause undesirable pixel-level changes around the transient improved edge. In this paper, we propose a new nonlinear filter-based adaptive shoot elimination method for effectively suppressing the overshoot and undershoot that occur in the transient improvement, so that we can obtain visually sharper and clearer digital images(or videos). The proposed method uses two orthogonal directional min/max nonlinear filters with an adaptive shoot elimination scheme in order to effectively suppress the visually sensitive overshoot and undershoot. Experimental results show that the proposed method suppresses the overshoot and undershoot almost perfectly while maintaining the effect of the transient improvement. The applications of the proposed method include digital TVs, digital monitors, digital cameras/camcoders, portable media players(PMP), etc.

• Journal of the Korean Applied Science and Technology
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• v.19 no.3
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• pp.189-197
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• 2002

The color stability and purity from OLED is of current interest. Aggregation of dyes alters the device color after fabrication of the devices. Exciplex and electroplex formations have been proposed to explain the aggregate color change. We investigate the possibility of exciplex formation and propose the new electroplex state that can cause the bathochromic shift of the electroluminescence spectrum from the devices with TPD/PBD layers. The photoluminescence maximum of the device was 420nm, and the electroluminescence maximum of the device to became 480nm. The bathochromic shift cannot be attained with photoluminescence study with highly concentrated TPD/PBD mixture. This clearly indicates that the 480nm spectrum of the devices is not resulted from the exciplex formation with TPD and PBD. We observed the overshoot in EL spectrum from the OLEDs. The most intense overshoot was observed at 460nm, which may be due to the aggregates that are formed after the electric field has been removed from the devices.

• Journal of Power Electronics
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• v.15 no.1
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• pp.177-189
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• 2015

The output of the controller is said to exceed the input limits of the plant being controlled when a control system operates in a non-linear region. This process is called the windup phenomenon. The windup phenomenon is not preferable in the control system because it leads to performance degradation, such as overshoot and system instability. Many anti-windup strategies involve switching, where the integral component differently operates between the linear and the non-linear states. The range of state for the non-overshoot performance is better illustrated by the boundary integral error plane than the proportional-integral (PI) plane in windup inspection. This study proposes a PI controller with a separate closed-loop integral controller and reference value set with respect to the input command and external torque. The PI controller is compared with existing conventional proportional integral, conditional integration, tracking back calculation, and integral state prediction schemes by using ScicosLab simulations. The controller is also experimentally verified on a direct current motor under no-load and loading conditions. The proposed controller shows a promising potential with its ability to eliminate overshoot with short settling time using the decoupling mode in both conditions.