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Examining the practice of a reading-to-speak test task: anxiety and experience of EFL students
Heng-Tsung Danny Huang 서울대학교 교육연구소 2010 Asia Pacific Education Review Vol.11 No.2
In the literature, little research has hitherto been conducted to examine the implementation of integrated speaking test tasks. This study, in response, set out to compare the anxiety induced by a reading-to-speak task and the anxiety produced by a speaking-only task and to explore students' experiences of taking the reading-to-speak task. Forty-seven Taiwanese EFL learners completed a reading-to-speak task and a speaking-only task, filled out a state anxiety inventory twice, and responded to an open-ended questionnaire. The paired t-test revealed that the reading-to-speak task produced a statistically comparable degree of anxiety as the speaking-only task, possibly owing to the additional anxiety inflicted by its reading component. The qualitative analysis disclosed that students preferred the reading-to-speak task to the speaking-only task, even though it provoked additional anxiety, featured additional challenges, and entailed different response strategies. In light of these findings, implications are proposed for oral assessment research and EFL oral assessment practices.
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Optimization of Super Twisting Sliding Mode Control Gains using Taguchi Method
Chiew Tsung Heng,Zamberi Jamaludin,Ahmad Yusairi Bani Hashim,Nur Aidawaty Rafan,Lokman Abdullah 대한산업공학회 2018 Industrial Engineeering & Management Systems Vol.17 No.1
This paper focuses on optimization of super twisting controller gains using Taguchi method with objective to minimize tracking error and the chattering effect. Two gain parameters in super twisting algorithm, that is L and W were identified as two factors with three levels respectively. The optimization method applied a L9 orthogonal array and the performance index used was root mean square of tracking error and Fast Fourier Transform of control inputs. The optimized super twisting controller with traditional sliding surface and the continuous control action laws was validated on a single axis direct driven linear motor. Analyses of variance and main effect plots were performed on the effect of gains variation on performance index. Values of L and W were chosen as 0.00002 and 0.08 respectively and were confirmed through confirmation test based on calculated confidence interval. Experimental results with 95% confidence level identified gain L as the significant factor in minimizing chattering effect while both gains L and W were responsible in minimizing tracking error in optimum condition. Optimized algorithm achieved 9.3% of reduction in root mean square of tracking error and 38.4% of reduction in chattering experimentally.
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Design of Super Twisting Algorithm for Chattering Suppression in Machine Tools
Chiew Tsung Heng,Zamberi Jamaludin,Ahmad Yusairi Bani Hashim,Lokman Abdullah,Nur Aidawaty Rafan 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.3
Sliding mode control is known for its robustness against plant uncertainties and disturbance rejection. An extension of this technique is the addition of super twisting algorithm that suppresses the chattering effectcommonly observed with sliding mode control application. This paper elaborates on the design and analysis ofthe super twisting algorithm with focus on optimizing the gain parameters. Two main components of the slidingmode super twisting controller were designed and validated; that is, the switching function and the control laws. The traditional sliding surface was used as the switching function while control laws with continuous control actionwere applied. Two gain parameters of the control laws were designed and analyzed in terms of tracking errorreduction and chattering effect. A Kalman-Bucy continuous filter was applied for velocity signal estimation. FastFourier Transform was applied on the control inputs to investigate the chattering amplitude and root mean squareof the tracking error was used as performance indicator for tracking error reduction. Analyses were performedon the effect of gains variation to control performance. Experimental results showed that gain L was sensitive tochattering amplitude while gain W provided wider range of tuning. The control performance was compared tothe traditional pseudo-sliding mode controller in terms of tracking error reduction and chattering effect. Resultsshowed that the super twisting algorithm produced superior results in tracking error reduction and was effective insuppressing chattering effect compared to the pseudo-sliding mode controller.
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