• IEMEK Journal of Embedded Systems and Applications
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• v.15 no.2
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• pp.103-109
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• 2020

This paper finds solutions for using ZigBee in wireless networked control system (WNCS). The round trip time delay and packet loss rate of the WNCS are measured. On the basis of these measured data, a playback buffer is used to solve the variable time delay in WNCS, and a Smith predictor is introduced to compensate for the time delay. The WNCS was able to be actually constructed to perform DC motor position control with 40 Hz sampling frequency.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.8
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• pp.768-773
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• 2012

Packet loss compensation techniques are increasingly important to stable remote control over wireless communication in WNCS (Wireless Networked Control Systems). Its time varying channels, limited bandwidth, interference, and poor signal not only leads to packet loss or latency, but also can negatively affect performance and system stability. This paper presents a compensation technique exploiting an EWMA (Exponentially Weighed Moving Average)-based value estimator to clarify the influence of packet loss on the overall WNCS behavior. As an example of actuator to be remotely controlled, a rotary-type inverted pendulum has been considered, and modeled. Performance evaluation results through Matlab/Simulink and Truetime co-simulation confirm the superiority of the proposed value estimation method over previous approaches.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.7
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• pp.572-580
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• 2013

IEEE 802.15.4e is a prospective standard for low latency control application in industries. This paper proposes a framework to evaluate the closed loop IEEE 802.15.4e based WNCS performance. The framework consists of two models: closed loop control system model and network model. The network model focuses on the PHY parameters of wireless link and takes the channel parameters into consideration. The PHY model combining with MAC model gives the control system model the probability of packet loss in a super-frame. In addition, redundancy mechanism is considered in IEEE 802.15.4e to reduce to data frame loss probability. The simulation is implemented in Matlab, PHY model takes the channel parameters from empirical results. Hence our evaluation gives insight into behavior of WNCS in different environments and it provides us a tool to design wireless network to achieve a good performance for control system.

• ICROS
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• v.18 no.3
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• pp.17-23
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• 2012

최근 십여년 간 통신 네트워크를 제어시스템에 도입한 네트워크 제어시스템 (Networked Control Systems : NCS)에 대한 연구가 활발히 진행 되고 있다. 이러한 NCS에 대한 최근의 연구동향을 살펴본다. NCS의 정의와 분류, NCS에서 발생하는 지연, 패킷손실, 양자화 오차, 이들을 해결하기 위한 제어기법, 스케줄링 등 여러 NCS와 관련한 제반 사항들의 동향을 살펴본다. 또, 현재 사용되고 있는 무선 네트워크의 종류, 실제로 무선네트워크 제어시스템(Wireless NCS : WNCS)을 구현한 예를 보인다.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.1
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• pp.9-15
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• 2018

This paper describes the applicability of Bluetooth and ZigBee networks for real-time control in wireless networked control system and suggests an effective usage of them. The Bluetooth SCO link, SPP and HID profiles and the ZigBee non-beacon enabled network are analyzed and the latency of them are measured. A number of wireless networked control system experiments are performed via DC motor control system and the various profiles of Bluetooth and ZigBee in real-time wireless networked control system are compared.

• Journal of Internet of Things and Convergence
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• v.9 no.1
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• pp.125-129
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• 2023

Age of Information (AoI) has been introduced in wireless networked control systems (WNCSs) to guarantee timely status updates. In addition, as the edge computing (EC) architecture has been deployed in NCS, EC close to sensors can be exploited to collect status updates from sensors and provide control decisions to actuators. However, when lots of sensors simultaneously deliver status updates, EC can be overloaded, which cannot satisfy the AoI requirement. To mitigate this problem, this paper uses actuators with computing capability that can directly receive the status updates from sensors and determine the control decision without the help of EC. To analyze the AoI of the actuation update via EC or directly using actuators, this paper developed an analytic model based on timing diagrams. Extensive simulation results are included to verify the analytic model and to show the AoI with various settings.