Quantized Static Output Feedback Control For Discrete-Time Systems

Chang, Xiao-Heng,Xiong, Jun,Li, Zhi-Min,Park, Ju H. IEEE 2018 IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS - Vol.14 No.8

<P>This paper investigates the problem of output feedback control for discrete-time systems with two quantized signals in measurement output and control input. Since the measurement output and control input are quantized by general quantizers before they are passed to the controller and the system, the closed-loop system will include the quantization error terms, which might lead to that the performance of the closed-loop system is not guaranteed. For this purpose, this paper proposes a novel quantized output control strategy such that the closed-loop system is asymptotically stable or satisfies the prescribed <TEX>$\mathcal {H}_\infty$</TEX> performance. The corresponding design conditions for the output feedback controllers and the quantizers’ dynamic parameters are presented in terms of solutions to a set of linear matrix inequalities. Finally, a simulation example is given to prove the effectiveness of the proposed design method.</P>

H_∞ Controller Design for Linear Systems with Time-invariant Uncertainties

Xiao-Heng Chang 제어·로봇·시스템학회 2011 International Journal of Control, Automation, and Vol.9 No.2

This paper considers the problem of designing robust H_∞ state feedback controller for linear continuous-time systems with time-invariant uncertainties. The main result given here concerns H_∞ controller design using the parameter dependent Lyapunov function approach and a new control law. A new condition ensuring the linear systems to be is asymptotically stable with a prescribed H_∞ performance is proposed in terms of a set of linear matrix inequalities (LMIs). Theoretic proof is given to show that the proposed condition is less conservative than existing results in the literature. An example is provided to demonstrate the efficiency of the proposed method.

Relaxed Stability Condition and State Feedback H∞ Controller Design for T-S Fuzzy Systems

Xiao-Heng Chang,Guang-Hong Yang 제어·로봇·시스템학회 2009 International Journal of Control, Automation, and Vol.7 No.1

In this paper, a fuzzy Lyapunov approach is presented for stability analysis and state feedback H∞ controller design for T-S fuzzy systems. A new stability condition is obtained by relaxing the ones derived in previous papers. Then, a set of LMI-based sufficient conditions which can guarantee the existence of state feedback H∞ controller for T-S fuzzy systems is proposed. In comparison with the existing literature, the proposed approach not only provides more relaxed stability conditions but also ensures better H∞ performance. The effectiveness of the proposed approach is shown through two numerical examples.

Fuzzy Resilient Energy-to-Peak Filtering for Continuous-Time Nonlinear Systems

Chang, Xiao-Heng,Park, Ju H.,Shi, Peng Institute of Electrical and Electronics Engineers, 2017 IEEE Transactions on Fuzzy Systems Vol. No.

<P>The problem of resilient energy-to-peak filtering for a class of uncertain continuous-time nonlinear systems is investigated in this paper. A Takagi–Sugeno fuzzy model with norm-bounded uncertainties is used to represent the nonlinear plant. Attention is focused on the design of an energy-to-peak filter such that the filtering error system is asymptotically stable and the prescribed energy-to-peak filtering performance is guaranteed, where the designed filter is assumed to have additive gain variations. The proposed design is aimed at all filter matrices with gain variations, which improves the existing results on resilient energy-to-peak filtering for continuous-time systems. A simulation example is provided to show the effectiveness of the proposed methods.</P>

Fault Detection Observer Design for Fuzzy Systems with Local Nonlinear Models via Fuzzy Lyapunov Function

Guojun Liu,Xiao-Heng Chang,Yong-Yan Cao 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.5

This paper concerns with the problem of designing fault detection (FD) observer for Takagi-Sugeno (TS)fuzzy systems subject to local nonlinear models. Different from the quadratic Lyapunov function approaches,fuzzy Lyapunov function approach is applied to design the fault detection observer, and corresponding sufficientconditions are given in terms of linear matrix inequalities. In addition, combined with nonlinear local modelsscheme and slack variable technique, the T-S fuzzy systems have fewer fuzzy rules to reduce the computationalburden. Compared with the existing results, less conservative results on existence of fuzzy fault detection observersare derived. Moreover, the designed fuzzy fault detection observer not only guarantees the residual system stabilitybut also improves the H_ index estimation. It is noted that the H_ index is employed to measure the worst-cast faultsensitivity performance. Finally, a numerical simulation is given to illustrate the effectiveness of the designed faultdetection observer.

Parameter-dependent Robust H∞ Filter Design for Uncertain Discrete-time Systems with Quantized Measurements

Ke-Zhen Han,Xiao-Heng Chang 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.1

This paper deals with the problem of parameter-dependent robust H∞ filter design for uncertain discrete-time systems with output quantization. The uncertain parameters are supposed to reside in a polytope. The system outputs are quantized by a memoryless logarithmic quantizer before being transmitted to a filter. Attention is focused on the design of a robust H∞ filter to mitigate quantization effects and ensure a prescribed H∞ noise attenuation level. Via introducing some slack variables and using the parameter-dependent Lyapunov function, sufficient conditions for the existence of a robust H∞ filter are expressed in terms of linear matrix inequalities (LMIs). Finally, a numerical example is provided to demonstrate the effectiveness of the proposed approach.

Human Embryonic Stem Cells - a Potential Vaccine for Ovarian Cancer

Zhang, Zu-Juan,Chen, Xin-Hua,Chang, Xiao-Hong,Ye, Xue,Li, Yi,Cui, Heng Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.9

Objective: To investigate the therapeutic potential of human embryonic stem cells (hESCs) as a vaccine to induce an immune response and provide antitumor protection in a rat model. Methods: Cross-reactivity of antigens between hESCs and tumour cells was screened by immunohistochemistry. Fischer 344 rats were divided into 7 groups, with 6 rats in each, immunized with: Group 1, hESC; Group 2, pre-inactivated mitotic NuTu-19; Group 3 PBS; Group 4, hESC; Group 5, pre-inactivated mitotic NuTu-19; Group 6, PBS; Group 7, hESC only. At 1 (Groups 1-3) or 4 weeks (Groups 4-6) after the last vaccination, each rat was challenged intraperitoneally with NuTu-19. Tumor growth and animal survival were closely monitored. Rats immunized with H9 and NuTu-19 were tested by Western blot analysis of rat orbital venous blood for cytokines produced by Th1 and Th2 cells. Results: hESCs presented tumour antigens, markers, and genes related to tumour growth, metastasis, and signal pathway interactions. The vaccine administered to rats in Group 1 led to significant antitumor responses and enhanced tumor rejection in rats with intraperitoneal inoculation of NuTu-19 cells compared to control groups. In contrast, rats in Group 4 did not display any elevation of antitumour responses. Western blot analysis found cross-reactivity among antibodies generated between H9 and NuTu-19. However, the cytokines did not show significant differences, and no side effects were detected. Conclusion: hESC-based vaccination is a promising modality for immunotherapy of ovarian cancer.

Delay of Surgery for Spinal Metastasis due to the COVID-19 Outbreak Affected Patient Outcomes

Chia-Jung Hsieh,Chun-Yu Wu,Yen-Heng Lin,Yu-Cheng Huang,Wen-Chi Yang,Tom Wei-Wu Chen,Wei-Li Ma,Wei-Hsin Lin,Feng-Ming Hsu,Furen Xiao,Shih-Hung Yang,Dar-Ming Lai,Chang-Mu Chen,Shin-Yi Chao,Fon-Yih Tsuan 대한척추신경외과학회 2023 Neurospine Vol.20 No.4

Objective: The present study is to analyze the effects of the coronavirus disease 2019 (COVID 2019) outbreak and the subsequent lockdown on the outcomes of spinal metastasis patients. Methods: The study was a retrospective analysis of data from a prospective cohort study. All patients underwent surgical intervention for spinal metastases between January 2019 and December 2021 and had at least 3 months of postoperative follow-up. The primary outcome was overall mortality during the 4 different stages (pre-COVID-19 era, COVID-19 pandemic except in Taiwan, national lockdown, lifting of the lockdown). The secondary outcomes were the oncological severity scores, medical/surgical accessibility, and patient functional outcome during the 4 periods as well as survival/mortality. Results: A total of 233 patients were included. The overall mortality rate was 41.20%. During the Taiwan lockdown, more patients received palliative surgery than other surgical methods, and no total en bloc spondylectomy was performed. The time from surgeon visit to operation was approximately doubled after the COVID-19 outbreak in Taiwan (75.97, 86.63, 168.79, and 166.91 hours in the 4 periods, respectively). The estimated survival probability was highest after the national lockdown was lifted and lowest during the lockdown. In the multivariate analysis, increased risk of mortality was observed with delay of surgery, with emergency surgery having a higher risk with delays above 33 hours, urgent surgery (below 59 and above 111 hours), and elective surgery (above 332 hours). Conclusion: The COVID-19 pandemic and related policies have altered daily clinical practice and negatively impacted the survival of patients with spinal metastases.