Somha, Worawit

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Somha, Worawit
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worawit.so@kmitl.ac.th

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    Item type:Publication,
    Development of Remote Laboratory for Feedback Control System Class
    (2021-01-01)
    Jitthammapirom, Piya
    ;
    Chayratsami, Pornpimon
    ;
    Somha, Worawit
    This research presents a low cost web-based remote laboratory system for a feedback control system class. The system is created by an inexpensive single-board computer (Raspberry Pi 3B+) as laboratory server, an edge of extinct Lego Mindstorms set as a controlled plant, and an IP camera system. The laboratory server based on Ubuntu, which is a free and open-source software and the web application is written with JavaScript based on a MEAN stack platform. The proposed laboratory is used for verifying a design project of the angle control system using Proportional-Integral-Derivative (PID) control.
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    A Richardson-Lucy Algorithm Based Blind Deconvolution to Decouple the Two Unknown Spatial-Temporal SRAM Margin Variations
    (2023-01-01)
    Yamauchi, Hiroyuki
    ;
    Somha, Worawit
    A Richardson-Lucy algorithm (RLA) based blind deconvolution with a new filter design technique was successfully developed. This allowed decoupling and retrieving of the information of the two unknown factors at once for the Random Temporal Variation (RTV) and the Random Spatial Variation (RSV). The variations of SRAM operating voltage (VDDMIN) are caused by the two coupled factors of RTV and RSV. Thus, this decoupling technique is prerequisite for the margin analysis. The designs of the device characteristics and the screening test conditions based on the analysis results were briefly demonstrated. The proposed filter design technique for the RLA based blind deconvolution allowed to circumvent the ill-conditioning ringing phenomena. This gives to enjoy the advantage in convergence speed and simplicity of the RLA. The relative errors of the blind-deconvolution for the RSV and RTV distributions were reduced to less than 0.3% within only 300-iteration cycles compared with the conventional one.
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    A dual-band filter designed for retrieving both left- and right-tailed RTN distributions in an iterative deconvolution procedure
    (2025-05-01)
    Yamauchi, Hiroyuki
    ;
    Somha, Worawit
    This paper proposes a dual-band filter design to alleviate a crucial ringing issue of the Richardson–Lucy deconvolution algorithm (RL-deconv). We found that the RL-deconv doesn’t work for an exponentially decaying tail due to the ringing. The reasons why we must handle this issue in the VLSI chip reliability design are: (1) the VLSI chip bit density has increased up to a 10<sup>12</sup>-bit scale, making the fail probability obey the long tail down to 10<sup>–12</sup>, and (2) the VLSI chip margin variations have become prominent, caused by atomic-level random behaviors. The tail for the variations caused margin variations to obey the Gamma distributions. Consequently, the tail of the VLSI chip margin distribution doesn’t follow the Gaussian distribution anymore. These backgrounds compel us to newly adopt the inverse problem methods to predict the tail distribution based on the deconvolution. As the tail gets longer, the element-wise misalignment becomes larger between the corresponding elements of the feedback gain and the objective of deconvolution, and this causes to more critical wrong element-wise amplification, leading to a ringing. We found that it is not sufficient to retrieve only the right tail because the left tail can no longer be ignored. The length of the left tail becomes long enough to influence the distribution after aging. To address this issue, this paper proposes a dual-band filter design for retrieving both left and right tails, which contributes to widening the alignment range of the feedback gain with the retrieving target in the RL-deconv iterative processes. It is found that the proposed technique reduces the RTN deconvolution error by 12-fold compared with the conventional one.