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Direct Adaptive Fuzzy Sliding Mode Control for Under-actuated Uncertain Systems
Shun-Feng Su,Yao-Chu Hsueh,Cio-Ping Tseng,Song-Shyong Chen,Yu-San Lin 한국지능시스템학회 2015 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.15 No.4
The development of the control algorithms for under-actuated systems is important. Decoupled sliding mode control has been successfully employed to control under-actuated systems in a decoupling manner with the use of sliding mode control. However, in such a control scheme, the system functions must be known. If there are uncertainties in those functions, the control performance may not be satisfactory. In this paper, the direct adaptive fuzzy sliding mode control is employed to control a class of under-actuated uncertain systems which can be regarded as a combination of several subsystems with one same control input. By using the hierarchical sliding control approach, a sliding control law is derived so as to make every subsystem stabilized at the same time. But, since the system considered is assumed to be uncertain, the sliding control law cannot be readily facilitated. Therefore, in the study, based on Lyapunov stable theory a fuzzy compensator is proposed to approximate the uncertain part of the sliding control law. From those simulations, it can be concluded that the proposed compensator can indeed cope with system uncertainties. Besides, it can be found that the proposed compensator also provide good robustness properties.
Tzi Dong Ng,Hsueh Chu Chen 아시아영어교육학회 2016 The Journal of Asia TEFL Vol.13 No.3
The purposes of this study were (a) to identify how ESL learners make phonological changes in English words in a code-mixing context; and (b) to examine ESL learners’ attitudes toward Cantonese-accented English and code-mixing in the classroom setting. Two groups of learners with high proficiency (HP) and mid-level proficiency (MP) were recruited to participate in the research. A specially designed codemixed script, an English translated version, and a list of isolated English words served as the tasks for collecting phonological data. A questionnaire survey was then used to examine participants’ opinions on code-mixing and its effects on pronunciation learning. The results showed that HP and MP learners pronounced numerous words similarly in a Cantonese-accented manner; however, MP learners were less likely to switch back to the correct pronunciation when the context of code-mixing was changed to pure English or when given a list of isolated English words. The survey results found that MP learners tended to be slightly more positive toward Cantonese-accented English and the use of a mixed code in English as a medium of instruction classrooms. Nonetheless, the use of code-mixing was less preferred in English lessons for learners of both groups. More HP learners considered Cantonese-accented English as a symbol of identity as Hongkongers than MP learners.
Direct Adaptive Fuzzy Sliding Mode Control for Under-actuated Uncertain Systems
Su, Shun-Feng,Hsueh, Yao-Chu,Tseng, Cio-Ping,Chen, Song-Shyong,Lin, Yu-San Korean Institute of Intelligent Systems 2015 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.15 No.4
The development of the control algorithms for under-actuated systems is important. Decoupled sliding mode control has been successfully employed to control under-actuated systems in a decoupling manner with the use of sliding mode control. However, in such a control scheme, the system functions must be known. If there are uncertainties in those functions, the control performance may not be satisfactory.In this paper, the direct adaptive fuzzy sliding mode control is employed to control a class of under-actuated uncertain systems which can be regarded as a combination of several subsystems with one same control input. By using the hierarchical sliding control approach, a sliding control law is derived so as to make every subsystem stabilized at the same time. But, since the system considered is assumed to be uncertain, the sliding control law cannot be readily facilitated. Therefore, in the study, based on Lyapunov stable theory a fuzzy compensator is proposed to approximate the uncertain part of the sliding control law. From those simulations, it can be concluded that the proposed compensator can indeed cope with system uncertainties. Besides, it can be found that the proposed compensator also provide good robustness properties.