Browsing by Author "Lai, Chien-Liang"

Now showing 1 - 9 of 9

Analysis and Implementation of a Model-free Approach in Network-induced Delay Compensation for Remote Control Systems
(2011)
Lai, Chien-Liang
;
Hsu, Pau-Lo
;
電機工程學系
;
Department of Electrical and Computer Engineering
With the rapid development and implementation of Internet technologies, well-designed/tuned controllers obtained from control design without network are desired, which can be further realized in remote control systems directly. Theoretically, available networked control system (NCS) designs are developed with a known system model and time delay. However, the nature of network-induced delay is unpredictable, which depends on network protocol and hardware, and available design approaches usually become impractical in real concerns. The study presents an NCS structure with the proposed perfect delay compensation (PDC) scheme, which is constructed with modified butterfly elements to deal with unknown delay effects without system model and delay information. Both analytical and simulation results prove that the proposed model-free PDC scheme effectively compensates for the unknown network-induced delays. Furthermore, the proposed PDC is carried out using Ethernet, and a well-tuned PI controller for the AC servo motor was directly networked to the remote control system. Experimental results indicate that the proposed PDC renders satisfactory and desirable design results in real NCS applications.
Design of the Adaptive Smith Predictor for the Time-Varying Network Control System
(2008)
Lai, Chien-Liang
;
Hsu, Pau-Lo
;
Wang, Bor-Chyun
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Ibis paper integrates Ethernet and control area network (CAN) with the TCP/IP communication gateway. The developed system has been applied to a remote control system for an AC 400W servo motor to verify the proposed adaptive Smith Predictor control method with the time-delay estimation algorithm. The time delay effect, defined as the round-trip time (1117), between the application layer of the server and the application layer of the client, has been measured and analyzed. Moreover, results indicate that NCS performance is degraded, and may even become unstable mainly due to the serious network time delay in a stochastic nature mainly occurred in the Ethernet. The Smith predictor is adopted to eliminate the constant time delay. However, the delay in a commercial network is time varying and it depends on the number of end users. An adaptive Smith predictor control scheme is developed in this paper by applying the on-line estimation to further improve control performance of the proposed NCS with the integrated Ethernet and CAN buses. Experimental results indicate that the time delay is drifting in both bounded and random natures for the integrated Ethernet+CAN network and the proposed control approach significantly improves motion accuracy as in the NCS for an AC motor-based motion system.
Design of the Multiple-rate Robust Controller for Wireless Networked Control Systems
(2008)
Lai, Chien-Liang
;
Hsu, Pau-Lo
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper integrates the IEEE 802.11 g ad-hoc wireless network and the control area network (CAN) in the present network control systems (NCS) or wireless-NCS (WNCS). Both the TCP and the CAN protocols are adopted as the communication gateway in a remote control system. The time delay between the application layer of the client and the application layer of the remote control target has been measured and analyzed in this paper. Experimental results on an AC 400W servo motor indicate that the communication jam mainly causes the instability due to the induced time delay. In this paper, by applying the adaptive Smith predictor with the switching sampling time, satisfactory control performance of WNCS can be obtained even though the time delay seriously increases. Moreover, the feasibility of the proposed WNCS has been proven through experimental results.
Design the Remote Control System With the Time-Delay Estimator and the Adaptive Smith Predictor
(2010-02-01)
Lai, Chien-Liang
;
Hsu, Pau-Lo
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In real applications, a remote control system is generally an integration of different networks consisting of a commercial network for message transmission and an industrial network to control the remote hardware through a communication gateway. Since the induced time-delay in network control system (NCS) may cause system instability, this paper proposes a remote NCS structure by implementing the adaptive Smith predictor with an online time-delay estimator. As the delay in a commercial network Ethernet is significantly time-varying depending on the number of end-users, the delay is estimated in this paper by processing the online measurement of the round-trip time (RTT) between the application layers of the server and the client. The adaptive Smith predictor control scheme is developed by directly applying the estimated time-delay. To prove the feasibility of the proposed remote control system, the developed design has been applied to an AC 400 W servo motor tested from a 15 km distance. The experimental results indicate that the significantly improved stability and motion accuracy can be reliably achieved by applying the proposed approach.
Realization of Networked Control Systems on Ethernet with Varied Time Delay
(2010)
Lai, Chien-Liang
;
Hsu, Pau-Lo
;
電機工程學系
;
Department of Electrical and Computer Engineering
An online delay estimation algorithm is adopted for the adaptive Smith predictor in the networked control systems (NCS) design under the significant delay time. However, the Smith predictor is sensitive to parameter uncertainties within the system model and time delay. The quantitative feedback theory (QFT) controller is suitable to cope with parameter uncertainties of the Smith predictor in this paper; moreover, a template expressed in phase and gain for the QFT design has been constructed by considering the bounded variations with the time delay and the external loading. Therefore, the adaptive Smith predictor control scheme with QFT controller provides better tolerance to parameter uncertainties. Both simulation and experimental results on AC servo motor with both the hybrid controller area network (CAN) bus and the Ethernet network have proven the feasibility and improved performance of the proposed NCS.
The Butterfly-Shaped Feedback Loop in Networked Control Systems for the Unknown Delay Compensation
(2014-08-01)
Lai, Chien-Liang
;
Hsu, Pau-Lo
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Available model-based networked control system (NCS) design approaches are basically formulated from the known system model and the information of the networked-induced delay time. Because the delay in remote control systems is significant and time-varied as commercial networks involved, available model-based NCS design approaches may thus become impractical. The increase of time delay due to the limited communication bandwidth usually induces data dropout to make NCS design even more difficult. In this paper, the scheme of the perfect delay compensation (PDC) is proposed by introducing the butterfly-shaped inner feedback loop in NCS to deal with the unknown network-induced time delay. Furthermore, analytical results indicate that the controller obtained in general control systems can be directly implemented on NCS with the proposed PDC scheme. Both simulation and experimental results were successfully carried out on an ac servo motor at a distance of 15 km through Ethernet to maintain a stable remote control system.
The Butterfly-Shaped Feedback Loop in Networked Control Systems for the Unknown Delay Compensation
(2014-08-01)
Lai, Chien-Liang
;
Hsu, Pau-Lo
;
電機工程學系
;
Department of Electrical and Computer Engineering
Available model-based networked control system (NCS) design approaches are basically formulated from the known system model and the information of the networked-induced delay time. Because the delay in remote control systems is significant and time-varied as commercial networks involved, available model-based NCS design approaches may thus become impractical. The increase of time delay due to the limited communication bandwidth usually induces data dropout to make NCS design even more difficult. In this paper, the scheme of the perfect delay compensation (PDC) is proposed by introducing the butterfly-shaped inner feedback loop in NCS to deal with the unknown network-induced time delay. Furthermore, analytical results indicate that the controller obtained in general control systems can be directly implemented on NCS with the proposed PDC scheme. Both simulation and experimental results were successfully carried out on an ac servo motor at a distance of 15 km through Ethernet to maintain a stable remote control system.
The Intelligent Message Estimator for Wireless Network Control Systems
(2010)
Chang, Che-Wei
;
Lai, Chien-Liang
;
Hsu, Pau-Lo
;
電機工程學系
;
Department of Electrical and Computer Engineering
The data dropout and the time delay in networked control systems (NCS) degrade their performance greatly, especially under the wireless applications. In this study, both the message estimator and the traffic monitor designed for the wireless network control system (WiNCS) are proposed. Instead of the event-trigger NCS, the output feedback signal is sent by the timing trigger and the received node implemented with a message estimator for effectively compensating those lost data. Different estimators applied to the WiNCS have been discussed and results indicate that the Taylor estimator is preferred with easy implementation on a light-traffic network. Moreover, with the heavy-load network, the intelligent message estimator (IME) is suitable to cope with the unstable problem occurred in the Taylor estimator. Experimental results show that the Taylor estimator reduced the output error 30.1 % within a light-traffic network, and the IME reduced the output error 74.7% even with a heavy network load. Finally, when the network traffic is heavy enough, the sampling time of the WiNCS must be adjusted according to the data dropout rate based on the network traffic monitor to further decrease the dropout rate.
The time-delay effect of multiple-network systems in NCS
(2007)
Cheng, Ching-Wen
;
Lai, Chien-Liang
;
Wang, Bor-Chyun
;
Hsu, Pau-Lo
;
電子工程學系及電子研究所
Applications of the network control system (NCS) improve the efficiency, the flexibility, and the reliability of large-scale systems in modem industries. In the same time, applications of NCS for remote control and monitoring reduce the time and cost of installation, reconfiguration, and maintenance. This study integrates the Ethernet, the control area network (CAN) network, and the wireless 802.11b in the present NCS. The TCP/IP and the CAN protocols are adopted as the communication gateway in a remote control system for an AC 400W servo motor. The time delay between the application layer of the client and the application layer of the remote control target has been measured and analyzed in this study. Experimental results indicate that different sampling rates and the environments will greatly affect the delayed time. Also, results indicate that the distance will not affect the delay time in wireless communication. However, as the sampling period reduces, the delay time of the network increases dramatically. In the wireless network, the delay time may change suddenly by the environment interferences. Finally, with a serious time delay, a Smith predictor has been successfully applied to control the servo motor from Kaohsiung which is in 300 kin away to verify the feasibility of the proposed NCS.