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Seulki Kyeong,Jirou Feng,Jae Kwan Ryu,Jung Jae Park,Kyeong Ha Lee,Jung Kim 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.3
Recognizing the user’s motion intentions is a crucial challenge to develop human augmented robotic devices due to safety and easiness of interactions. Among the possible sensorial modalities, surface electromyography (sEMG) signals have been tested to be a primary motion intention channel due to the inherent advantage of electromechanical delay and the muscle activation information. However, the lack of detailed sEMG characteristics as motion recognition has been difficult issues to develop safe and intuitive interactions with the robots. In this study, we evaluated the sEMG characteristics for their potential applicability to recognizing the motion intentions of humans. For the discrete motion intention recognition, the walking environments were classified using only sEMG signals by support vector machine (SVM) and linear discriminated analysis (LDA) models with accuracy of 79.1% and 76.3%. Due to the fact that it is crucial to identify an unexpected disturbance by the collision between the exoskeleton and surrounding environment in recognizing the user intention to guarantee the safety of the user, sEMG and torque sensors were used to classify user-intended interaction forces and disturbance forces in the event of collisions. A control algorithm was proposed that detects and compensates for collisions, and its performance showed that robust motion intention recognition and control of powered exoskeletons are possible. We investigated the effect of muscle fatigue caused by long-term walking with heavy load wearing an exoskeleton. The sEMG amplitude and frequency were analyzed for muscle fatigue due to single-joint (knee extensions) and multi-joint (walking) exercises, and muscle fatigue due to walking was prominent in the signal from the vastus medialis (VM). The characteristics of sEMG due to muscle fatigue should be seriously considered in continuous motion estimation.
A Mechatronic Mirror-Image Motion Device for Symmetric Upper-Limb Rehabilitation
Seulki Kyeong,Youngjin Na,Jung Kim 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.5
This paper presents an upper-limb rehabilitation device that provides symmetric bilateral movements with motion measurementsusing inertial sensors. Mirror therapy is one of widely used methods for rehabilitation of impaired side movementsbecause voluntary movement of the unimpaired side facilitates reorganizational changes in the motor cortex. The developedupper-limb exoskeleton was equipped with two brushless DC motors that helped generate three axes of upper-limb movementscorresponding to other arm movements that were measured using inertial sensors. In this study, inertial sensors wereused to estimate the joint angles for three target upper-limb movements: elbow fl exion and extension (fl ex/ext), wrist fl ex/ext, and forearm pronation and supination (pro/sup). Elbow fl ex/ext was performed by the actuator that was directly attachedto the elbow joint. The actuation of the forearm pro/sup and wrist fl ex/ext shared one motor using a developed cable-drivenmechanism, and two types of motion were selectively performed. We assessed the feasibility of the proposed mirror-imagedevice with the accuracy and precision of the motion estimation and the actuation of joint movements. An individual couldperform most upper-limb movements for activities of daily living using the proposed device.
Indium-Free Amorphous Ca-Al-O Thin Film as a Transparent Conducting Oxide
Sim, So Hee,Kang, Kyeong Tae,Lee, Sangyun,Lee, Miso,Taniguchi, Hiroki,Kim, Suyoung,Roh, Seulki,Oh, Jun Hyeob,Lee, Sang A,Bae, Jong-Seong,Jang, Jae Hyuck,Hwang, Jungseek,Han, Seungwu,Park, Tuson,Choi, American Chemical Society 2019 Chemistry of materials Vol.31 No.19
<P>Transparent conducting oxide (TCO) is a promising material system for transparent electrodes, which is one of the most essential elements in current electronic and energy devices. In particular, In-based TCOs such as Sn:In<SUB>2</SUB>O<SUB>3</SUB> (ITO) and In-Ga-Zn-O (IGZO) have shown large optical band gap and high electrical conductivity, sufficient for the applications. However, In is an expensive element, which hampers its facile industrial application. Moreover, In-based TCOs show an abrupt decrease in conductivity when their thickness decreases below ∼100 nm, possibly due to inhomogeneity within the thin films. Here, we introduce an amorphous Ca-Al-O (CAO) thin film as a promising candidate for the In-free TCOs. The amorphous CAO thin film has very low resistivity (∼10<SUP>-5</SUP> Ω cm) at room temperature, as well as high transparency in the visible region of the light spectrum (>80%). The isotropic Ca <I>s</I>-orbital in the conduction band is found to be responsible for the superior performance of CAO as a TCO. Owing to the exceptional structural homogeneity of the CAO thin film, thickness-independent transport characteristics are observed, maintaining its TCO performance down to 10 nm of thickness.</P> [FIG OMISSION]</BR>