• Smart Structures and Systems
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• v.29 no.5
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• pp.661-675
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• 2022

In this paper, an electric vehicle drives with efficient control and low cost hardware using four quadrant DC converter with Permanent Magnet Direct Current (PMDC) motor fed by DC boost converter is presented. The main idea of this work is to improve the energy efficiency of the conversion chain of an electric vehicle by inserting a boost converter between the battery and the four quadrant-DC motor chopper assembly. Consequently, this method makes it possible to maintain the amplification gain of the 4 quadrant chopper constant regardless of the battery voltage drop and even in the presence of a fault in the battery. One of the most important control problems is control under heavy uncertainty conditions. The higher order sliding mode control technique is introduced for the adjustment of DC bus voltage and mechanical motor speed. To implement the proposed approach in the automotive field, experimental tests were carried out. The performances obtained show the usefulness of this system for a better energy management of an electric vehicle and an ideal control under different operating conditions and constraints, mostly at nominal operation, in the presence of a load torque, when reversing the direction of rotation of the motor speed and even in case of battery chamber failure. The whole system has been tested experimentally and its performance has been analyzed.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.2
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• pp.89-94
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• 2005

In this paper, we propose a fuzzy PID controller of new method. There are two problems in absolute digital PID controller. First, much calculation time need for obtain the sum of data at each period. Second, this is problem need much memory because to storage every data at the before period. We use the speed type PID digital controller to improvement such problems. In the propose controller doesn't use without adjustment the crisp output error and we doesn't use nile tables in the fuzzy inference process at the forward stage fuzzifier. We inference output member ship function by using the relation and range of two variable of PID gain parameters. We can obtained desired results through the simulation and a experiment of the hydraulic servo motor control system.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.5
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• pp.401-408
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• 2000

In this paper, we proposed a fuzzy controller that founded by the general feedback control with the new adjustment method when it's tuning. The general feedback controller is operated that supply to the plant making the control input multiplying the appropriate gain of controller on the error between the output of the plant and the reference, But proposed feedback fuzzy controller consist of three loops. The inner loop consists of plant and an ordinary feedback controller. The fuzzy inference of controller performed by the outer loops, which is composed of a fuzzy modeling and inference. We can observe that the output of control system converges toward the reference. Also, the behaviour of feedback fuzzy system is converged from the transient. That is, we verified that designed fuzzy controllers was adapted effectively through the experiments in the hydraulic motor system using floating point DSP processor.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.6
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• pp.532-539
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• 2012

This paper proposes a balancing and driving control system for a bicycle robot. A reaction wheel pendulum control method is adopted to maintain the balance while the bicycle robot is driving. For the driving control, PID control algorithm with a variable gain adjustment has been developed in this paper, where the gains are heuristically adjusted during the experiments. To measure the angles of the wheels the encoders are used. For the balancing control, a roll controller is designed with a non-model based algorithm to make the shortest cycle. The tilt angle is measured by the fusion of the acceleration and gyroscope sensors, which is used to generate the control input of the roll controller to make the tilt angle zero. The performance of the designed control system has been verified through the real experiments with the developed bicycle robot.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.2
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• pp.61-74
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• 2014

In recent years, development of femtocells are receiving considerable attention towards increasing the network coverage, capacity, and improvement in the quality of service for users. In 3GPP LTE-Advanced (LTE-A) system, to efficiently utilize the bandwidth, femtocell and macro cell uses the same frequency band, but this deployment poses a technical challenge of cross-tier interference to macro users. In this paper, the novel quality of service based fractional power control (QoS-FPC) scheme under the heterogeneous networks environment is proposed, which considers the users priority and QoS-requirements during the power allocation. The proposed QoS-FPC scheme has two focal points: firs, it protects the macrocell users uplink communication by limiting the cross-tier interference at eNB below a given threshold, and second, it ensures the optimization of femtocell users power allocation at each power adjustment phase. Performance gain is demonstrated with extensive system-level simulations to show that the proposed QoS-FPC scheme significantly decreases the cross-tier intereference and improves the overall users throughput.

• Journal of the Korean Home Economics Association
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• v.44 no.8
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• pp.23-32
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• 2006

Understanding the experience of parents without custody after divorce is important in terms of facilitating their adjustment and positive relationships with their children. Ninety-two noncustodial parents divorced within the previous 5 years completed a structured questionnaire. We examined differences between noncustodial fathers and mothers in terms of the frequency of the contact and the relationship satisfaction with children. In addition, using the regression model, we analyzed the effects of several characteristics of noncustodial parents, including gender, on the frequency of contact as well as the relationship satisfaction with children. The main results of the study are as follows. First, noncustodial fathers and mothers exhibited similar low levels of contact by phone and in-person visits. Second, noncustodial parents with a child older than 8 years old visited the child more frequently, and were more satisfied than noncustodial parents with younger children. Third, the level of desire to gain the child custody had a significant effect on the frequency of contact and the satisfaction of the relationship between the noncustodial parents and their children. Fourth, noncustodial parents with more positive feeling about their former spouse contacted more frequently with the children. Fifth, compared with noncustodial fathers, noncustodial mothers demonstrated a higher relationship satisfaction with their children.

• The Journal of the Acoustical Society of Korea
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• v.31 no.5
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• pp.340-351
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• 2012

In this paper, we proposed the stereo-10.2channel blind upmix algorithm for the enhanced 3D sound. Recently, consumers want to enjoy better sound and the use of a various of multichannel configuration has been steadily improved. Thus, upmix algorithms have been researched. However, conventional upmix algorithms have the problem that distorts the spatial information of original source. To solve this problem and enhance the spatial sound quality, we proposed front and rear channel gain adjustment and 10.2 channel upmix algorithm for each additional channel. The listening test results show that it maintains spatial information of stereo input and enhances 3D sound effects unlike other conventional upmix algorithms.

• The Journal of Korea Robotics Society
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• v.17 no.1
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• pp.76-85
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• 2022

One of the most fundamental challenges when designing controllers for dynamic systems is the adjustment of controller parameters. Usually the system model is used to get the initial controller, but eventually the controller parameters must be manually adjusted in the real system to achieve the best performance. To avoid this manual tuning step, data-driven methods such as machine learning were used. Recently, reinforcement learning became one alternative of this problem to be considered as an agent learns policies in large state space with trial-and-error Markov Decision Process (MDP) which is widely used in the field of robotics. However, on initial training step, as an agent tries to explore to the new state space with random action and acts directly on the controller parameters in real systems, MDP can lead the system safety-critical system failures. Therefore, the issue of 'safe exploration' became important. In this paper we meet 'safe exploration' condition with Control Barrier Function (CBF) which converts direct constraints on the state space to the implicit constraint of the control inputs. Given an initial low-performance controller, it automatically optimizes the parameters of the control law while ensuring safety by the CBF so that the agent can learn how to predict and control unknown and often stochastic environments. Simulation results on a quadrotor UAV indicate that the proposed method can safely optimize controller parameters quickly and automatically.

• Journal of Korean Academy of Nursing
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• v.30 no.4
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• pp.1066-1077
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• 2000

The purpose of this study is to develop self-efficacy promotion program and to test its effects on self-efficacy, self-care, physiologic index of hemodialysis patients after applying this program to them. Preliminary study was carried out to identify the levels and types of self-care, self-efficacy of hemodialysis patients. To develop self-efficacy promoting program, several discussions with nursing professors and nurse specialists on hemodialysis patients were made after in-depth literature review on the area. Through these processes, the self-efficacy promoting program including 20 minutes long videotape and other counciling documents were completed. This videotape consisted of specific self-care techniques for hemodialysis patients including management of fistula, measurement of blood presure and body weight, special diets, medications, exercise and rest, management of physical problems and social adjustment. Two group equivalent pre and post test quasai-experimental research design was used in this study. The total subjects were 34 hemodialysis patients who received hemodialysis three time per week at 1 university hospital. Seventeen experimental group subjects were matched with control group subjects in sex and age. Data were analysed with the SPSS window program. Homogeniety between experimental and control group pretest data was tested by x$^2$ and t-test. There were no significanct differences in general characteristics, illness history, specific self-efficacy and self-care between the two groups. The differences of general self-efficacy of two groups were tested with the Repeated Measure ANCOVA because of significant differences of pretest data of general self efficacy between two groups. The differences of self-efficacy and self-care of two groups were tested with Repeated Measure ANOVA and the differences of physiologic indecies including blood potassium level and blood phosphorus level and interdialytic weight gain were tested by t-test. The results were as follows: 1. There was no significant difference in general self-efficacy between the two groups over four different time, and no interaction by groups and by time. 2. There was significant difference in specific self-efficacy between the two groups over four different time, and interaction by groups and by time. 3. There was significant difference in self-care between the two groups over four different time, and interaction by groups and by time. 4. There were no significant differences of blood potassium level and blood phosphorus level, but there was significant difference of interdialytic weight gain between the two groups. From the results above, it can be concluded that the self-efficacy promotion program for hemodialysis patients was effective to improve degree of specific self-efficacy and self-care and to decrease interdialytic weight gain. Considering results, the followings are recommended: 1) Repeated studies are needed for another hemodialysis patients. 2) This program can be used for improving degree of self-efficacy and self-care of hemodialysis patients by nurse practitioner and nurse educator.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.6
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• pp.800-807
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• 2019

Objective: The aim was to evaluate backgrounding beef steers on oat + ryegrass pastures mixed with vetch and/or using energy supplementation. Methods: A randomized block design with three treatments and three replications was used. The treatments were: grass + supplement (oat + ryegrass + supplementation), legume + supplement (oat + ryegrass + vetch + supplementation) and grass + legume (oat + ryegrass + vetch). A continuous grazing system with a variable stocking rate was used. Twenty-seven intact crossbred steers (1/4 Marchigiana, 1/4 Aberdeen Angus and 2/4 Nellore) aged 7 months old and average weight of 190 kg were used. Steers were supplemented at 1% of the body weight of ground corn. The experiment lasted 84 days, between May and August 2014. Behavioral assessments were performed two times per experimental period, for 24 hours. Results: The forage mass was different between treatments, being greater for steers fed without legume. The accumulation rate, forage allowance, and stocking rate did not differ between treatments due to the adequate adjustment of forage allowance. The final weight of animals, as well as the dry matter intake (kg/d), did not differ between treatments. However, forage intake was higher for non-supplemented animals in relation to supplemented steers. Supplement intake did not alter the total digestible nutrient intake due to pasture quality. Animals fed grass + supplement had higher live weight gain per area than those fed grass + legume. Animals without supplementation spent more time in grazing. Conclusion: Feeding behavior was not altered by mixing with vetch or supplementation. Non-supplemented animals started the grazing peak earlier and spent more time in grazing than those supplemented; however, the average daily gain was similar between treatments. The live weight gain per hectare was 47% higher in pastures in which the animals received supplementation compared with those mixed with vetch, a consequence of the substitutive effect.