Development of an interactive game-based mirror image hand rehabilitation system

Kim, Sangjoon J.,Han, Sang Yun,Yang, Gi-Hun,Kim, Jung,Ahn, Bummo SPRINGER SCIENCE + BUSINESS MEDIA 2019 INTELLIGENT SERVICE ROBOTICS Vol.12 No.2

Development of an MR-compatible hand exoskeleton that is capable of providing interactive robotic rehabilitation during fMRI imaging

Kim, Sangjoon J.,Kim, Yeongjin,Lee, Hyosang,Ghasemlou, Pouya,Kim, Jung Springer-Verlag 2018 Medical & biological engineering & computing Vol.56 No.2

<P>Following advances in robotic rehabilitation, there have been many efforts to investigate the recovery process and effectiveness of robotic rehabilitation procedures through monitoring the activation status of the brain. This work presents the development of a two degree-of-freedom (DoF) magnetic resonance (MR)-compatible hand device that can perform robotic rehabilitation procedures inside an fMRI scanner. The device is capable of providing real-time monitoring of the joint angle, angular velocity, and joint force produced by the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of four fingers. For force measurement, a custom reflective optical force sensor was developed and characterized in terms of accuracy error, hysteresis, and repeatability in the MR environment. The proposed device consists of two non-magnetic ultrasonic motors to provide assistive and resistive forces to the MCP and PIP joints. With actuation and sensing capabilities, both non-voluntary-passive movements and active-voluntary movements can be implemented. The MR compatibility of the device was verified via the analysis of the signal-to-noise ratio (SNR) of MR images of phantoms. SNR drops of 0.25, 2.94, and 11.82% were observed when the device was present but not activated, when only the custom force sensor was activated, and when both the custom force sensor and actuators were activated, respectively.</P>

Design of a seamless active ankle foot orthosis empowered by a custom portable pneumatic pump

Sangjoon J. Kim,Handduet Chang,Haedo Cho,Jung Kim 제어로봇시스템학회 2018 제어로봇시스템학회 국제학술대회 논문집 Vol.2018 No.10

Development of a compact optical torque sensor with decoupling axial-interference effects for pHRI

Lee, Hyein,Kim, Sangjoon J.,Chang, Handdeut,Kim, Jung Elsevier 2018 Mechatronics Vol.52 No.-

<P>This paper presents the design of an optical torque sensor that can structurally decouple the effect of axial-interference for use in various robotics applications. Torque sensors are widely used in the joints of intelligent service or wearable robots to realize safe human-robot interaction. Whole robot body sensing using torque sensors is essential for safe interaction. However, most torque sensors are bulky, heavy and expensive. Therefore, many optical-based torque sensors have been proposed to deal with such problems, but the issue of axial-interference still remains. We resolved the axial-interference problem via the geometrical structure of the sensor body and differential signaling using two reflective optical sensors. The moment interference error was successfully decreased from 4.49% (with one optical sensor) to 0.11% (with two optical sensors) using the proposed sensor structure while maintaining a compact size, lightweight, and low cost. Static tests and dynamic tests were carried out and analyzed for accuracy error, hysteresis, and repeatability. We then compared the performance of an impedance controller that is widely used in service and wearable robots using the proposed sensor and a commercial torque sensor with respect to various control loop rates. The control performance of the proposed sensor was comparable to that of commercial sensors.</P>

Development of Active Stiffness Mechanism for Self-stabilizing Manipulator

Handdeut Chang,Sangjoon J. Kim,Jung Kim 제어로봇시스템학회 2016 제어로봇시스템학회 국제학술대회 논문집 Vol.2016 No.10

The stabilization of most artificial systems has been achieved by sensor based state feedback control with high signal transmission speed and high computational power, and stiff structures. In contrast, many biological systems can achieve similar or superior stable behavior with low signal transmission speed and low computational power via nervous system, and flexible structures. In order to explain this phenomenon, our research group focused the concept of self-stabilization of musculoskeletal system. Self-stabilization is defined as the ability to restore its original state after a disturbance with feedforward control. In our previous research, we analytically investigated the self-stabilizing condition of biological musculoskeletal system using the Lyapunov stability criteria and come to a conclusion that stiffness and viscosity of the joint play significant role in self-stabilization. Particularly, there exist two types of stiffness in biological muscle; one is spring-like passive stiffness and the other is active stiffness that is proportional to muscle activation. We believe that active stiffness plays a significant role in self-stabilization for dynamic movement. In this paper, we develop an active stiffness mechanism that can assign self-stabilizing function to a robotic arm. As a result, theoretically predicted self-stabilizing function is experimentally verified and explains why biological musculoskeletal system can be stabilized with feedforward control.

Force estimation in fatigue condition using a muscle-twitch model during isometric finger contraction

Na, Youngjin,Kim, Sangjoon J.,Kim, Jung Elsevier 2017 Medical engineering & physics Vol.50 No.-

<P><B>Abstract</B></P> <P>We propose a force estimation method in fatigue condition using a muscle-twitch model and surface electromyography (sEMG). The twitch model, which is an estimate of force by a single spike, was obtained from sEMG features and measured forces. Nine healthy subjects performed isometric index finger abduction until exhaustion for a series of dynamic contractions (0–20% MVC) to characterize the twitch model and static contractions (50% MVC) to induce muscle fatigue. Muscle fatigue was identified based on the changes of twitch model; the twitch peak decreased and the contraction time increased as muscle fatigue developed. Force estimation performance in non-fatigue and fatigue conditions was evaluated and its results were compared with that of a conventional method using the mean absolute value (MAV). In non-fatigue conditions, the performance of the proposed method (0.90 ± 0.05) and the MAV method (0.88 ± 0.06) were comparable. In fatigue conditions, the performance was significantly improved for the proposed method (0.87 ± 0.05) compared with the MAV (0.78 ± 0.09).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Muscle fatigue has a significant effect on the characteristics of sEMG in long-term contractions.. </LI> <LI> The proposed twitch model was used to detect muscle fatigue and estimate isometric finger force in fatigue condition. </LI> <LI> Based on manifestation of changes in the twitch model, proposed method could be used as an indicator of muscle fatigue. </LI> <LI> The force estimation with the twitch model showed superior results compared to a conventional method in fatigue condition. </LI> </UL> </P>

Dispenser printing of piezo-resistive nanocomposite on woven elastic fabric and hysteresis compensation for skin-mountable stretch sensing

Lee, Hyosang,Cho, Haedo,Kim, Sangjoon J,Kim, Yeongjin,Kim, Jung Institute of Physics Publishing 2018 Smart materials & structures Vol.27 No.2

<P>Recently, piezo-resistive nanocomposites have emerged as an important smart material for realizing less obtrusive and more comfortable stretch sensing applications. To manufacture cost-effective and skin-mountable stretch sensor, dispenser printing is advantageous method because piezo-resistive nanocomposites can be directly printed on a woven elastic fabric in various patterns. However, both electrical and mechanical properties of the nanocomposites need to be modulated to achieve favorable sensing performance as well as strong adhesion between the nanocomposite and the fabric to sustain large strains. Moreover, inherent hysteretic behavior of the soft nanocomposite should be compensated to obtain consistent stretch sensing. This paper presents silicone rubber mixed with long multi-walled carbon nanotubes (Long-MWCNTs) composites as a piezo-resistive transducing material for dispenser printing. High aspect ratio of the Long-MWCNTs resulted in low viscosity of a liquid state nanocomposite and high electrical conductivity. Due to the low viscosity, the liquid state nanocomposite could permeate into gaps of the woven elastic fabrics and ensured strong bonding force in large strains up to 35%. In addition, a modified Prandtl-Ishilinskii (MPI) model was adopted to compensate for piezo-resistive hysteresis of the nanocomposite. For validation, the skin-mountable sensor was applied to estimate rotation angle of a wrist. The sensor system estimated the rotation angle of the wrist with an estimation error of 1.93 degrees within 65 degrees range (2.9%) for the step increment and decrement test, and 7.15 degrees within 75 degrees range (9.5%) for the arbitrary movement test. Thus, the experimental results show that the dispenser printing method incorporated with hysteresis compensation can provide a guideline to implement skin-mountable smart fabrics for stretch sensing using various nanocomposites</P>

Characterization of Spastic Ankle Flexors Based on Viscoelastic Modeling for Accurate Diagnosis

신원석,Handdeut Chang,Sangjoon J. Kim,김정 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.1

Characterization of the musculoskeletal system is essential for diagnosis providing the implications for therapy corresponding to causes of the diseases. This paper presents a characterization of an ankle neuromuscular system of patients with spasticity, to provide quantitative pathological level of the ankle spasticity with biomechanical and neurological disorders. Measurements from manual spasticity evaluation combined with a suggested neuromuscular model and parameter optimization process enabled a reliable characterization of the spastic ankle flexors. The model included two non-neural parameters representing the viscoelasticity of the muscle and four neural parameters showing the dynamics of muscle activation and corresponding force only using the measured joint angle and resistance torque. Torque contributions from non-neural parameters especially elastic properties of muscle was greater than 50% of the overall torque, common in both patients with spasticity and healthy controls. Among subgroups of the patients, subjects with short post diseases period less than 5 years, had higher torque contribution level from neural components more than 50% of the overall torque compared to the patients with longer post diseases period more than 10 years who had overall torque less than 30% of the total estimated torque. We concluded that proposed model based ankle flexor characterization served as a tools for diagnosing the patients with spasticity corresponding to their causes of diseases with both quantified neural and non-neural parameters.

유연한 수술 로봇의 현재 문제점과 현황: Review

정회룡(Hoeryong Jung),김상준(Sangjoon J. Kim),박정훈(Junghoon Park),조해도(Haedo Cho),안범모(Bummo Ahn),나영진(Youngjin Na),김영진(Yeongjin Kim) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.10

최소 침습 수술(minimally invasive surgery, MIS)에서 수술 도구의 유연성과 조작 용이성은 매우 중요한 요소이다. 유연 수술 로봇은 유연한 동작이 가능하고 조작이 용이하여 기존 복강경 수술로봇 대비 향상된 수술결과를 기대할 수 있어 기존 수술로봇의 한계를 극복할 수 있는 진보된 수술로봇으로 주목을 받고 있다. 본 논문에서는 메소-스케일(meso-scale)의 최신 유연 수술 로봇을 소개하고, 유연 수술 로봇의 디자인 및 한계점을 분석하고자 한다. 연 조직(soft tissue)을 대상으로 개발된 다양한 최신의 유연수술 로봇들을 소개하고 유연 수술 로봇의 한계점을 극복하기 위한 영상 유도 기법, 관절의 강성 조절기법, 로봇의 재질 등에 대한 최신의 연구동향을 살펴본다. 현재 유연 수술 로봇의 기술적 한계점을 분석하고 향후 연구개발 방향을 제시한다. A soft surgical robot in a minimally invasive surgery offers flexibility and ease of operation. The robot can be used to easily access the lesion and perform surgical processes even in a narrow space within the abdominal cavity during surgery. This review paper introduces the latest meso-scale soft surgical robots and describes their design and limitations. This paper discusses various surgical robots used in various medical fields targeting soft tissues only. Image guidance techniques, stiffness modulation control of the soft joints, and materials of the robot body to overcome limitations of the existing soft surgical robots are a main focus of this review.

Fishing Line Spring Based Tendon for Concealed Ankle Brace

Seungjun Lee,Sanghee Lee,Hyunho Kim,Sanghun Jung,hyerim Jeon,Sangjoon J. Kim,Kyungseo Park,Yeongjin Kim 제어로봇시스템학회 2018 제어로봇시스템학회 국제학술대회 논문집 Vol.2018 No.10