• 설비공학논문집
• /
• 제24권1호
• /
• pp.1-8
• /
• 2012

Recently, the needs of system performances such as working speed and processing accuracy in machine tools have been increased. Especially, the speed increment generates harmful heat at both moving part of the machine tools and handicrafts. The heat is a main drawback to progress accuracy of the processing. Hence, a cooler system to control temperature is inevitable for the machine tools. In general, two representative control schemes, hot-gas bypass and variable speed control of a compressor, have been adopted in the water cooler system. In this paper, comparisons of system performances according to the control schemes in a cooler for machine tools were conducted in detail. Each proportional-integral feedback controller for the two different control systems is designed. The system performances, especially the temperature control accuracy and coefficient of performance which is a criterion of energy saving, were mainly analyzed through various experiments using 1RT water cooler system with different two types of control scheme. These evaluations will provide useful information to choose suitable water cooler system for the engineers who design controllers of the cooler system for machine tools.

• 대한안전경영과학회지
• /
• 제14권3호
• /
• pp.193-205
• /
• 2012

Since manufacturing and supplying corporations today come to view their practice of SCM as important, it becomes essential to analyze and control the structural relationship between the information sharing among corporations and the performances resulting from their practice of SCM. It is thus the purpose of this paper to examine the factors that may prompt corporations to implement SCM by means of analyses into the relationship between information sharing and practice of SCM which corporations should lay stress on as well as the relationship between financial and non-financial performances of corporations. The findings of the study can be summed up as follows: First, as for the relationship between information sharing among and practice of SCM by corporations, information sharing among corporations turned out to affect such factors of implementing their SCM as trust, commitment mutual dependence. Consequently, corporations are requested to endeavor to implement SCM itself faithfully if they really aim to achieve their performances by practice of SCM and, at the same time, to make efforts to obtain understanding and support for information sharing among themselves. Second, from the analysis of the relationship between SCM and financial as well as non-financial performances of corporations, it was found that trust, a factor of SCM practice, had influence upon non-financial performances of corporations, but not upon their financial performances, while commitment and mutual dependence affected both financial and non-financial achievements of corporations. Therefore, it was made clear from the analysis that the decision and systematic control of SCM activities which best suit to a corporation play an important role in improving its financial and non-financial performances, because they greatly depend on the implementing extent of SCM factors such as trust, commitment and mutual dependence among corporations.

• 음성과학
• /
• 제15권2호
• /
• pp.111-118
• /
• 2008

We identified the characteristic impairmants of linguistic semantic memory in patients with prodromal Alzheimer's disease(AD) and mild AD. To elucidate the earliest changes of semantic language function in subjects with AD, performances on confrontation naming test and verbal fluency task were compared among patients with AD patients (n=20), mild AD patients (n=27) and healthy elderly controls (n=20). Tasks in this study included the confrontation naming test of Test of Lexical Processing in Aphasia(TLPA/Japanese) and one-minute verbal fluency task (semantic/ phonetic categories). The results were as follows: 1) Performances of the prodromal AD group showed the comparable to those of the control group on the confrontation naming test, 2) In the semantic/phonetic verbal fluency tasks, the performances of the control group were better than those of the prodromal AD and mild AD groups, but no significant differences were shown between the prodromal AD and the mild AD group.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• 제9권4호
• /
• pp.309-314
• /
• 2009

This paper presents implementation of the adaptive neuro-fuzzy control method. Control performance of the adaptive neuro-fuzzy control method for a popular inverted pendulum system is evaluated. The inverted pendulum system is designed and built as an education kit for educational purpose for engineering students. The educational kit is specially used for intelligent control education. Control purpose is to satisfy balancing angle and desired trajectory tracking performance. The adaptive neuro-fuzzy controller has the Takagi-Sugeno(T-S) fuzzy structure. Back-propagation algorithm is used for updating weights in the fuzzy control. Control performances of the inverted pendulum system by PID control method and the adaptive neuro-fuzzy control method are compared. Control hardware of a DSP 2812 board is used to achieve the real-time control performance. Experimental studies are conducted to show successful control performances of the inverted pendulum system by the adaptive neuro-fuzzy control method.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
• /
• pp.700-703
• /
• 1997

A robust controller for a 6 DOF magnetically levitated fine manipulator is presented. The proposed controller consists of following two parts : a model reference controller (MRC) and a H$_{\infty}$ controller (HIC). First, the MRC stabilizes the motion of the manipulator. Then, the motion of the manipulator follows that of the reference model. Second, the HIC minimizes errors generated from the MRC due to noise and disturbance since the HIC is a kind of robust controller. The experiments of position control and tracking control are carried out by use of the proposed controller under the conditions of free disturbances and forced disturbances. Also, the experiments using PID controller are carried out under the same conditions. The results from above two controllers are compared to investigate the control performances. As the results, it is observed that the proposed controller has similar position accuracy but better tracking performances comparing to the PID controller as well as good disturbance rejection effect due to the robust characteristics of the controller. In conclusion, it is verified that the proposed controller has the simple control structure, the good tracking performances and good disturbance rejection effect due to the robust characteristics of the controller..

• 한국기계기술학회지
• /
• 제13권2호
• /
• pp.45-54
• /
• 2011

A vehicle suspension system performs two functions, the ride quality and the stability, which conflict with each other. Among the various suspension systems, an active suspension system has an external energy source, from which energy is always supplied to the system for continuous control of vehicle motion. In the process of the linearization for the nonlinear active suspension system, the frequency dependent damping method is used for the exact modelling to the real model. The pressure control valve which is controlled by proportional solenoid is the most important component in the active suspension system. The pressure control valve has the dynamic characteristics with 1st order delay. Therefore, It's necessary to adopt the lead compensator to compensate the dynamics of the pressure control valve. The sampling time is also important factor for the control performances. The sampling time value is proposed to satisfy the system performances. After the modelling and simulation for the pressure control valve and vehicle dynamic, the performances of the vehicle ride quality and the stability are enhanced.

• 제어로봇시스템학회논문지
• /
• 제16권7호
• /
• pp.681-687
• /
• 2010

In this paper, an implementation of force control for a slave mobile robot in tele-operation environment is presented. A mobile robot is built to have a force control capability with a force sensor and tested for force tracking control performances. Both position and contact force are regulated by a PID based hybrid control method and the impedance force control method. To minimize accumulated errors due to the adaptive impedance force control method, the novel force control method with a weighted function is proposed. Experimental studies of regulating contact forces for different control algorithms are tested and their performances are compared.

• 공학교육연구
• /
• 제19권2호
• /
• pp.3-7
• /
• 2016

A flow control system was designed and fabricated to control the flow rate of liquid through the pipe. This control system was composed of hardwares and software, hardwares as controller, gate valve, orifice meter and data aquisition board and software as National instruments Labview program. Control of flow rate was executed by adjusting the pneumatic valve located at the center of pipe line based on the control signal generated by LabView PID control algorithm, which converts analog signal measured by pressure difference of orifice to digital signal to adjust pneumatic valve. For the controller setup Ziegler-Nichols tuning technique was applied and control performances were investigated for not only the disturbance but also the set point changes. Developed system showed good control performances in flow control enough to use as teaching tool of feedback control theory and practice in university, and also as industrial application.

• 한국해양공학회지
• /
• 제34권2호
• /
• pp.77-88
• /
• 2020

In this study, heading characteristics and heading control performances were evaluated to achieve the wave shield effect. The wave shield effect originating from heading control reduces the relative motions of moored vessels in a floating liquefied natural gas bunkering terminal (FLBT). Therefore, loading and off-loading performances are improved through reduced relative motion. For the objective of this study and efficiency of the analysis, a simplified model was used that assuming no relative motion of the moored vessels in the FLBT. The simplified model involved modeling the environmental loads and inertia of several floating bodies, including FLBT, into the environmental loads and inertia of a single vessel. The simplified model was validated through comparisons with model tests. With the simplified model, heading characteristics and heading control simulations were performed using low-frequency planar motion equations. The heading characteristics and heading control performances of FLBT were analyzed through the results of simulations under the expected environmental conditions. The capacity of the tunnel thrust for the heading control performance was confirmed to be adequate for improvement of the loading and off-loading performances using the wave shielding effects under the operation conditions.

• International Journal of Safety
• /
• 제10권1호
• /
• pp.22-31
• /
• 2011

Seismic response control method of the bridge structures with semi-active control device, i.e., magneto-rheological (MR) damper, is studied in this paper. Design of various kinds of clipped optimal controller and fuzzy controller are suggested as a semi-active control algorithm. For determining the control force of MR damper, clipped optimal control method adopts bi-state approach, but the fuzzy control method continuously quantifies input currents through fuzzy inference mechanism to finely modulate the damper force. To investigate the performances of the suggested control techniques, numerical simulations of a multi-span continuous bridge system subjected to various earthquakes are performed, and their performances are compared with each other. From the comparison of results, it is shown that the fuzzy control system can provide well-balanced control force between girder and pier in the view point of structural safety and stability and be quite effective in reducing both girder and pier displacements over the existing control method.