• International journal of advanced smart convergence
• /
• 제5권1호
• /
• pp.34-46
• /
• 2016

Networked Control System (NCS) has evolved in the past decade through the advances in communication technology. The problems involved in NCS are broadly classified into two categories namely network issues due to network and control performance due to system network. The network problems are related to bandwidth allocation, scheduling and network security, and the control problems deal with stability analysis and delay compensation. Various delays with variable length occur due to sharing a common network medium. Though most delays are very less and mostly neglected, the network induced delay is significant. It occurs when sensors, actuators, and controllers exchange data packet across the communication network. Networked induced delay arises from sensor to controller and controller to actuator. This paper presents an adaptive delay compensation process for efficient control. Though Smith predictor has been commonly used as dead time compensators, it is not adaptive to match with the stochastic behavior of network characteristics. Time delay adaptive compensation gives an effective control to solve dead time, and creates a virtual environment using the plant model and computed delay which is used to compensate the effect of delay. This approach is simulated using TrueTime simulator that is a Matlab Simulink based simulator facilitates co-simulation of controller task execution in real-time kernels, network transmissions and continuous plant dynamics for NCS. The simulation result is analyzed, and it is confirmed that this control provides good performance.

• 대한전기학회논문지
• /
• 제39권9호
• /
• pp.997-1005
• /
• 1990

Integral Error and State Feedback (IESF) controller which incorporates state feedback as a modern control scheme and integral action as a classical control scheme has better performance than that of conventional PID controller in linear time invariant system. But the structure of the IESF controller requires all the state variables of the system and is applicable only to pole assignable linear time invariant systems without time delay. Many industrial processes have large time delay and it is impossible to directly apply IESF control scheme to those processes. In this paper, a new controller structure, Modified Integral Error and State Feedback (MIESF) has been suggested in order to effectively control processes having time delay and its performance has been analyzed and its effectiveness has also been confirmed. As the proposed controller uses output feedback scheme based on integral error and state feedback (IESF) method, it can be simply designed by pole assignment algorithm irrespective of the order of the process. The MIESF controller can follow setpoint changes without overshoot. It is robuster than conventional Smith-Predictor plus PI(D) controller in case of occurring time delay mismatch and extra parameter mismatches between the process and the model. It can enhance control performance by intentional time delay mismatch.

• 여성건강간호학회지
• /
• 제11권2호
• /
• pp.156-162
• /
• 2005

Purpose: The study was done to identify the relationship of symptoms of stress, cancer prevention behavior, the quality of life in women, and the factors influencing the quality of life. Method: The subjects of this study were 210 married women. They were living in Gyeonggi Province and Busan Metropolitan City. Symptoms of stress were measured by the Park's Stress Scale. Cancer preventive behavior was measured by Suh's Korean scale, and Smith Kline Beecham Quality of life' Scale by Dunbar. Data was analyzed with the SPSS program by ANOVA, Pearson's correlation, and Multiple Regression Analysis. Result: The higher scores of physical stress correlated with lower practice scores of cancer prevention behavior. Psychological and physical stress revealed negative correlations among sub-items of the QOL such as competence, psychological well-being, stability, physical well-being and activity. Multiple regression analysis revealed that the predictor of quality of life in the women was stress. A combination of symptoms of stress and cancer prevention behaviors accounted for 35.3% of the variance in the quality of life in the women. Conclusion: The most important factor influencing the quality of life of women was stress. Thus the study's findings can be useful in directing a comprehensive nursing care plan to improve the QOL of women.

• 전자공학회논문지SC
• /
• 제44권1호
• /
• pp.33-39
• /
• 2007

LonWorks/IP VDN은 LonWorks 디바이스 네트워크와 IP(데이터) 네트워크와의 통합네트워크로 산업현장에 대한 유비쿼터스 접근을 제공하여 설비에 대한 예지 및 예방보전을 가능하게 한다. 산업현장에 대한 예지 및 예방보전을 위한 실시간 분산제어 환경에서 즉각적인 응답은 필수불가결한 요소이다. LonWorks/IP 가상 디바이스 네트워크(VDN) 상에서 불확실한 시간지연은 산업현장에 대한 실시간 예지 및 예방보전을 위해 분산 제어를 수행할 때 시스템의 안정성과 성능을 악화시킨다. 따라서 네트워킹 된 분산제어시스템의 안정성을 보장하고 성능을 개선하기 위해서는 시간에 따라 가변적인 불확실한 시간지연을 보상할 필요가 있다. 본 논문에서는 LonWorks/IP VDN와 같은 분산제어 환경 하에서 서보 제어를 수행하는 경우에 외란관측기와 위상지연 보상기로 ZPETC(Zero Phase Error Tracking Controller)를 도입한 제어구조가 제시되고 컴퓨터 모의실험이 수행된다. 제안된 제어기의 성능은 컴퓨터 모의실험을 통하여 외란관측기를 도입한 Smith 예측기 기반의 내부모델제어기(IMC)의 제어결과와 비교 제시된다. 제안된 제어기는 외란과 잡음에 강인한 특성을 가지며, 주기적인 신호에 대한 추종성능을 상당히 개선시키므로 가변적인 시간지연을 갖는 LonWorks/IP VDN 상에서 주기적인 작업 수행에 필요한 분산 서보제어에 매우 적합하다.

• 간호행정학회지
• /
• 제11권1호
• /
• pp.1-12
• /
• 2005

Purpose: The purpose was to analyze the effects of internal marketing activity factors on nurse's turnover intention, nursing task performance and nursing productivity. Methods: The subjects were 355 nurses who were working at the 3 universities hospital over 1 year. The instruments were used of internal marketing activity factors(Lee, 2001), turnover intension(Lee, 1995), nursing task performance(Park, 1988) and nursing productivity(McNeese-Smith, 1996). Results: The mean score of internal marketing activity factors was 2.79, education and training 2.97, individualization 2.93, communication 2.87, promotion 2.76, work environment 2.63, reward system 2.62, and management vision for employee 2.61. The turnover intention was 3.12, nursing task performance 3.49, and nursing productivity 3.38. The internal marketing activity factors were negatively correlated with turnover intention(r=-0.37, p<0.0001), and positively correlated with nursing task performance(r=0.29, p<0.0001) and nursing productivity(r=0.30, p<0.0001). The key predictor of turnover intension was reward system, education and training, communication, and salary. They explained 35.0% of the total variance. In nursing task performance, communication, management vision for employee, salary and unit explained 26.0% of the total variance. In nursing productivity, communication, reward, education and training, salary, and position explained 24.0%. Conclusions: To increase nurse's nursing task performance and nursing productivity and to decrease turnover intention, it is necessary to concentrate on improving communication and reward system in the internal marketing activity factors. Through these activities, the effectiveness of internal marketing strategies will be enhanced and finally, nursing organizational outcome will be increased.