Commercial exoskeletons currently utilize multiple sensors, including inertial measurement units, electromyography sensors, and torque/force sensors, to detect human motion. While these sensors improve motion recognition by leveraging their unique strengths, they can also lead to discomfort due to direct skin contact, added weight, and complex wiring. In this paper, we propose a simplified motion recognition method that relies solely on encoders embedded in the motors. Our approach aims to accurately classify various movements by learning their distinctive features through a deep learning model. Specifically, we employ a convolutional neural network algorithm optimized for motion classification. Experimental results show that our model can effectively differentiate between movements such as standing, lifting, level walking, and inclined walking, achieving a test accuracy of 98.76%. Additionally, by implementing a sliding window maximum algorithm that tracks three consecutive classifications, we achieved a real-time motion recognition accuracy of 97.48% with a response time of 0.25 seconds. This approach provides a cost-effective and simplified solution for lower limb motion recognition, with potential applications in rehabilitation-focused exoskeletons.
Carrying heavy objects in agricultural and industrial sites is the most basic labor, which requires a lot of energy. Many equipment such as crane, chain block, elevator, and forklift truck has been developed to reduce human power. Nevertheless, many tasks require human labor. In addition, rapid aging is increasing musculoskeletal diseases in industrial workers. Consequently, various muscle auxiliary wear robots and devices are being developed. In this study; a passive upper limbs exoskeleton (H-Frame) was developed to help carry over 20 kg of weight in industrial and agricultural sites. For the functional test of the developed H-Frame, tests were carried out for 20, 30, and 40 kg of each box. To measure the objective and numerical data of the H-Frame, various sensor values such as EMG (Electromyography), harness compression force sensor, and load cell value of side support and rope were measured. EMG and metabolic experiments were also performed on 8 subjects before and after wearing the device. The average value of the upper extremity muscle showed a 44% reduction effect after wearing. The device helped the wearer when carrying heavy objects. It could help prevent musculoskeletal diseases in industrial and agricultural fields.
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Comparative Analysis between IMU Signal-based Neural Network Models for Energy Expenditure Estimation Chang June Lee, Jung Keun Lee Journal of the Korean Society for Precision Engineering.2024; 41(3): 191. CrossRef
Many human movements can be aided by exo-suit. One of them is that humans put a lot of strain on their knee and waist joints while lifting large objects, but using an exo-suit can lessen the risk. However, since the weight of the exo-suit itself acts as an additional burden on body, an appropriate torque distribution strategy considering the entire system is necessary. To solve this problem, this paper proposed an assistive technique based on whole-body control. Meanwhile, when the legs are fully extended during torque control, the system has a singularity problem and the required torque will be highly increased. Singularity is serious problem because it is essential to fully straighten the legs during the lifting operation. In this paper, this problem was solved by adding a straight-leg term to the whole-body control cost function. The feasibility of the proposed method was verified through simulation, and it was shown that the exo-suit could stably perform lifting motions due to the method.
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Comparative Analysis between IMU Signal-based Neural Network Models for Energy Expenditure Estimation Chang June Lee, Jung Keun Lee Journal of the Korean Society for Precision Engineering.2024; 41(3): 191. CrossRef
Herein, we describe the development of a wearable lower limb rehabilitation robot that can perform walking movement according to the walking pattern trajectory. The robot can adjust the left and right widths of the waist and the front and rear widths of 100 and 20 mm, and the length of the thigh link and calf link by 100 and 80 mm, respectively, so that stroke patients of different heights and weights can use it in hospitals. For manufacturing the lower limb rehabilitation robot, the right exoskeleton was safely designed through structural analysis, and the motor and reducer constituting the hip joint actuator were calculated. The fabricated lower limb rehabilitation robot was divided into its own characteristic experiment and wearing characteristic experiment. Its own characteristic experiment was an experiment by the robot itself, and the wearing characteristic experiment was an experiment conducted after a person wears the robot. Through these two experiments, angular deviation of the walking pattern was analyzed. Results of the analysis confirmed that the wearable walking characteristic test was performed within 3.1° based on the self walking characteristic test result. Therefore, the fabricated lower limb rehabilitation robot can be used for gait training in stroke patients.
This paper deals with the development of a passive modular hip exoskeleton system aimed at preventing musculoskeletal low back pain, which commonly occurs in heavy weight transport workers, by improving back muscle strength. The passive exoskeleton system has the advantage of being lightweight, making it suitable for modular exoskeleton systems. The cam and spring actuator designed in this study was applied to the passive modular exoskeleton system to build human hip and lumbar muscle strength. In order to evaluate the effectiveness of the passive modular exoskeleton system, a test was performed in which a subject lifted a 15 kg weight three times in a stoop posture, using heart rate measurement and Borg scale recording. According to the results, all subjects showed 26.83% lower maximum heart rate and 34.73% lower average heart rate than those who did not wear the system, and Borg scale evaluation result was lower. All subjects wore this system and did not experience back pain during the experiment. Through this study, we validated the effectiveness of the passive modular exoskeleton system and proved that this system can build the strength of industrial workers and be a solution to prevent musculoskeletal lumbar disease.
For the teleoperation of dual-arm robots with various tasks, the existence of a controller with a high degree of freedom is indispensable. Especially when precise work is required, additional information such as force feedback is very helpful for the operator. In transmitting such force information, a control device of exoskeleton-type with many points of contact with the human body can be one of the solutions. This paper proposes an optimal design method for the 7 degrees of freedom (DOF) exoskeleton systems. The proposed method optimizes the kinematic parameters by using kinematic performance indices related to the dexterity of the human and exoskeleton system. The manipulability ellipsoid is a representative index that can confirm the dexterity of the robot. In this study, we derived the objective function considering the human body model and then optimized it using a genetic algorithm. Unlike other HRI (Human-Robot Interaction) systems, exoskeleton robots share the end-effector as well as the base of the robot with the wearer. Therefore, it is hypothesized that the proposed performance index will be highly suitable for exoskeleton systems.
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Development of a Realistic Simulator for Driving Education of a Disaster-Responding Special Purpose Machinery Hyo-Gon Kim, Jung-Woo Park, Hyo-Jun Lee, Sung-Ho Park, Young-Ho Choi, Byeong-Kyu Lee, Jin-Ho Suh Journal of Power System Engineering.2021; 25(2): 86. CrossRef
In the case of paralysis caused by brain diseases and accidents, proper rehabilitation and supplementary systems for daily life are essential. In this study, we designed a system that can enable daily life by supporting the hand of a patient whose function has been lost to paralysis. The hand exoskeleton robot proposed in this study can be transported for the purpose of ADL (activities of daily living). It was designed to focus on the most important assistant for the thumb and index finger. The hand exoskeleton robot proposed in this study enables grasp and pinch motor skills during the human hand operation through the specific mechanism for the segment movement of the human finger simultaneously. Finally, the finger movement trace of the wearer through the vision system is measured, respectively.
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Design for Additive Manufacturing of Agricultural Strength Assisting Exoskeleton Suit Kwanhyung Park, Haeyong Yun, Yongjun Cho, Hyunggil Hong, Sunho Jang, Minsu Kang, Jaehyo Kim, Hochan Kim Journal of the Korean Society of Manufacturing Process Engineers.2022; 21(12): 69. CrossRef
Actuators for exoskeleton robots comprise various types such as electric, hydraulic, and pneumatic and it is necessary to apply the correct actuator according to the purpose. Most exoskeleton robots mainly use electric actuators, and some special-purpose robots, such as for heavy-load transport requiring large force, use hydraulic actuators. In this paper, friction of the actuation module consisting of a harmonic drive and a brushless DC motor is measured through experiments. And the friction characteristics of the actuation module are analyzed. The harmonic drive transmission system has various advantages, but it also has hysteresis and nonlinear friction characteristics. The friction compensation control of the actuation module enables precise control of the exoskeleton robot, and improves the robot’s performance. Appropriate friction model selection and design affects friction compensation performance. In this study, static and dynamic friction models are designed and analyzed based on the friction data of the actuation module.
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Method for Radial Stiffness Measurement of Strain Wave Gear Flexspline Sangwoong Lee, Daegwon Koh, Jong-Geol Kim, Murim Kim Journal of the Korean Society for Precision Engineering.2024; 41(12): 923. CrossRef
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Patients with complete paralysis that only walk with the assistance of exoskeleton robots because they lost their ability to walk. However, robots do not allow the exoskeleton robot to grasp the current state before walking and change the walking pattern. A "Stability Circle Region" was proposed to determine the current state of the exoskeleton robot. The Stability Circle is an area that can determine the possibility of a fall situation before the next walk using the link parameters of the robot and the current center of gravity of the patients. This study verified the validity of "stability circle" by simulating the change in the center of mass. Simulation results can be used to determine the stability of walking depending on whether the position of the center of mass before the walking is included in the circle area.
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Design of Assistive Wearable System for Walking Seong-Dae Choi, Sang-Hun Lee Journal of the Korean Society of Manufacturing Process Engineers.2019; 18(12): 111. CrossRef
Research of different types of powered exoskeleton have been conducted for various purposes. Recently, the exoskeleton has been used in rehabilitation training for patients with walking problems. For the exoskeletons to appropriately assist the user in gait rehabilitation, it is essential to understand user"s intention. The user"s walking intention includes the temporal aspect of timing of movements and the quantitative aspect of how large the movement is. This study, quantitatively identifies the relationship between arm and leg movements during walking, the user"s quantitative intention for gait, and suggests for a control strategy to assist user"s movement accordingly for a 1DoF hip exoskeleton for hemiplegic gait rehabilitation.
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Measurement, Evaluation, and Control of Active Intelligent Gait Training Systems—Analysis of the Current State of the Art Yi Han, Chenhao Liu, Bin Zhang, Ning Zhang, Shuoyu Wang, Meimei Han, João P. Ferreira, Tao Liu, Xiufeng Zhang Electronics.2022; 11(10): 1633. CrossRef
This study presented a mechanism overview of a novel modular knee exoskeleton, ACE-Knee, and the analysis of the design requirements by observing human knee-motion characteristics. The ACE-Knee exoskeleton consists of 1) base frame at waist, 2) a 3-DOF (degrees of freedom) passive spherical hip, and 3) a knee driving mechanism. The passive hip is designed based on a 3R spherical serial chain such that it has RCM (remote center of motion) capability. For designing a compact and efficient knee driving mechanism, it is realized by two crank-slider linkages where two sliders are coupled with a linear spring. The proposed kinematic structure enables the driving concept of the passive support by the linear spring and the active following by an actuator. In order to setup design requirements, gait experiments were performed for level walking and ascending/descending stairs. From the analysis of experimental results, unique motion and quasi-stiffness characteristics of human knee were identified.
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Static and Dynamic Friction Characteristics Analysis of Actuation Module for Friction Compensation of Exoskeleton Robot Byoung Ju Lee, Gwang Tae Kim, Hong Cheol Kim, Young June Shin Journal of the Korean Society for Precision Engineering.2019; 36(10): 929. CrossRef
To solve the limitation of motion synchronization measurement method applied to medical rehabilitation in most laboratories, a new method to measure the change of metabolic costs with or without a military exoskeleton on an external field environment has been proposed. The relationship between oxygen consumption and heart rate in male subjects aged 20- 30 years is analyzed and an equation that estimates oxygen consumption by heart rate was derived using a multiple regression analysis. An evaluation model which verifies the effectiveness of military exoskeleton was established for specific military scenarios utilizing exoskeleton. As a result, the proposed method is simple and effective for quantitative evaluation of exoskeleton system and can be a substitute of the evaluation methods for the metabolic costs or movement synchronization between human and exoskeleton.
In this paper, we examine the exoskeleton robot which can support the muscular strength of the soldiers handling the front load and its applicability in the military field. In fact, in the questionnaire survey on the military applicability of exoskeleton robots, many soldiers reported that they felt immensely fatigued due to the heavy load on their back during the operation. Most of the exoskeleton robots in the military have been developed to reduce fatigue during the mobility and movement of soldiers. Research on the exoskeleton robots to support the waist has been carried out with emphasis on its role in assisting performance of repetitive work in the industrial field or the medical field. To examine the studies on conventional back support exoskeleton robots and to find out the functions required to apply a back-support exoskeleton robot to soldiers, we have classified the existing back support exoskeleton robots into power type, supported body, waterproof grades, and others based on weight, purpose, working time, etc. Apparently, the shape of the exoskeleton robot suitable for application in the military field and the required performance is presented in the present work.
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Mapping of Human Contact Areas for Application Field of Wearable Robots Ran-i Eom, Yejin Lee International Journal of Costume and Fashion.2020; 20(2): 11. CrossRef
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