Hwan Choi - Academia.edu (original) (raw)
Papers by Hwan Choi
2020 8th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob), 2020
Passive ankle prostheses are the most common prosthetic device used by people with lower limb amp... more Passive ankle prostheses are the most common prosthetic device used by people with lower limb amputation. They use an energy recycling mechanism that mimics the behavior of the Achilles tendon and gastrocnemius muscle. The passive ankle prosthetic foot, which is usually made of carbon fiber, similarly stores energy during early to mid-stance by bending under the body’s weight. This energy is returned to the gait as the weight of the body is shifted off the device during terminal stance. However, most current standard of care passive ankle prostheses return the stored energy too early, dissipating most of the energy pushing the limb upward rather than propelling the body forward due to the absence of any muscle control.In this study, we developed an ankle prosthetic timing module that can control the energy return timing of an ankle prostheses, replicating the function of the gastrocnemius muscle. Our ankle prosthetic timing module is designed to be installed onto most current standa...
Many individuals with cerebral palsy (CP) and stroke are prescribed ankle foot orthoses (AFOs) fo... more Many individuals with cerebral palsy (CP) and stroke are prescribed ankle foot orthoses (AFOs) for use during daily life. AFOs have been shown to improve pathologic gait and walking speed in CP and stroke by providing support and alignment. There are many different types of AFOs available such as posterior leaf spring AFOs, rigid AFOs, and articulated AFOs. Further, there are many parameters that can be customized or tuned for each type of AFO, such as stiffness, heel height, shank to vertical angle, and foot plate length. However, how different types of AFOs and the customization of specific parameters impact muscle function remains unclear. The goals of this dissertation were to evaluate how different types of AFOs and different tuning parameters impact gait kinematics and muscle function. Of particular interest is the gastrocnemius, a key muscle that crosses the knee and ankle joints and is commonly tight among individuals with CP or stroke. Gastrocnemius operating length, define...
Introduction Identifying human kinematics is the primary step of biomechanics analyses and clinic... more Introduction Identifying human kinematics is the primary step of biomechanics analyses and clinical evaluation for people with walking disabilities. A typical method for calculating human kinematics is to use a marker-based motion capture system. Such method has a major drawback when capturing motions outside the lab, makes it challenging to measure the various dynamic tasks in daily living. To solve this issue, it has been suggested [1] to use inertial measurement unit (IMU) sensors to capture the motion [1]. However, this method requires attachment of IMU sensors on each body segment. People may feel this is too cumbertom to apply in daily life, limiting the use in real application. Thus, this study aims to investigate the feasibility of capturing the joint angles of lower extremities with a reduced number of IMU sensors using a deep learning algorithm. We hypothesize that if we can train a deep learning model good enough, it can extract the information from a reduced number of IM...
Identifying 3D human walking poses in unconstrained environments has many applications such as en... more Identifying 3D human walking poses in unconstrained environments has many applications such as enabling prosthetists and clinicians to access the amputees’ walking functions outside clinics and helping amputees obtain an optimal walking condition with predictive control. Thus, we propose the wearable motion capture problem of reconstructing and predicting 3D human poses from the wearable IMU sensors and wearable cameras. To solve this challenging problem, we introduce a novel Attention-Oriented Recurrent Neural Network (AttRNet) that contains a sensor-wise attention-oriented recurrent encoder, a reconstruction module, and a dynamic temporal attention-oriented recurrent decoder, to reconstruct the current pose and predict the future poses. To evaluate our approach, we collected a new WearableMotionCapture dataset using wearable IMUs and wearable video cameras, along with the musculoskeletal joint angle ground truth. The proposed AttRNet shows high accuracy on theWearableMotionCapture...
Measurement of human body movement is an essential step in biomechanical analysis. The current st... more Measurement of human body movement is an essential step in biomechanical analysis. The current standard for human motion capture systems uses infrared cameras to track reflective markers placed on the subject. While these systems can accurately track joint kinematics, the analyses are spatially limited to the lab environment. Though Inertial Measurement Unit (IMU) can eliminate the spatial limitations of the motion capture system, those systems are impractical for use in daily living due to the need for many sensors, typically one per body segment. Due to the need for practical and accurate estimation of joint kinematics, this study implements a reduced number of IMU sensors and employs machine learning algorithm to map sensor data to joint angles. Our developed algorithm estimates hip, knee, and ankle angles in the sagittal plane using two shoe-mounted IMU sensors in different practical walking conditions: treadmill, level overground, stair, and slope conditions. Specifically, we p...
Abstracts of the 26th Annual Meeting of the GCMAS, 2021
Scientific Reports, 2021
With the spread of COVID-19, significant emphasis has been placed on mitigation techniques such a... more With the spread of COVID-19, significant emphasis has been placed on mitigation techniques such as mask wearing to slow infectious disease transmission. Widespread use of face coverings has revealed challenges such as mask contamination and waste, presenting an opportunity to improve the current technologies. In response, we have developed the Auto-sanitizing Retractable Mask Optimized for Reusability (ARMOR). ARMOR is a novel, reusable face covering that can be quickly disinfected using an array of ultraviolet C lamps contained within a wearable case. A nanomembrane UVC sensor was used to quantify the intensity of germicidal radiation at 18 different locations on the face covering and determine the necessary exposure time to inactivate SARS-CoV-2 in addition to other viruses and bacteria. After experimentation, it was found that ARMOR successfully provided germicidal radiation to all areas of the mask and will inactivate SARS-CoV-2 in approximately 180 s, H1N1 Influenza in 130 s, a...
Scientific Reports, 2018
Powered ankle prostheses have been designed to reduce the energetic burden that individuals with ... more Powered ankle prostheses have been designed to reduce the energetic burden that individuals with transtibial amputation experience during ambulation. There is an open question regarding how much power the prosthesis should provide, and whether approximating biological ankle kinetics is optimal to reduce the metabolic cost of users. We tested 10 individuals with transtibial amputation walking on a treadmill wearing the BiOM powered ankle prosthesis programmed with 6 different power settings (0-100%), including a prosthetist-chosen setting, chosen to approximate biological ankle kinetics. We measured subjects' metabolic cost of transport (COT) and the BiOM's net ankle work during each condition. Across participants, power settings greater than 50% resulted in lower COT than 0% or 25%. The relationship between power setting, COT, and net ankle work varied considerably between subjects, possibly due to individual adaptation and exploitation of the BiOM's reflexive controller. For all subjects, the best tested power setting was higher than the prosthetist-chosen setting, resulting in a statistically significant and meaningful difference in COT between the best tested and prosthetistchosen power settings. The results of this study demonstrate that individuals with transtibial amputation may benefit from prescribed prosthetic ankle push-off work that exceeds biological norms. Individuals with transtibial amputation spend 10-30% more metabolic energy when walking compared to able-bodied individuals 1-3. This observed increase in energy expenditure may be due to the fact that most ankle prostheses are passive-elastic devices, which store and release energy when in contact with the ground but cannot perform positive net work. In fact, passive-elastic prostheses only produce about an eighth the power of the intact gastrocnemius and soleus muscles 4. This deficit has a significant impact on walking as the majority of the total mechanical power generated during the gait cycle comes from the ankle-foot complex 5-7. As a result of decreased ankle power generation, people with amputation may put forth additional muscular effort from their residual limb or compensate with their intact limb to walk with passive prostheses 8. Additionally, physical fitness may play an important role in determining the metabolic demands of individuals with amputation 9. To overcome these limitations of passive devices, various types of powered ankle prostheses have been developed 10-12. These powered devices use actuators to deliver positive work to the user during the push-off phase, and can potentially alleviate the increased energetic demand that people with amputation experience during walking. Of these devices, only the BiOM powered ankle prosthesis (BionX, Bedford, MA) is currently commercially available. Investigating the efficacy of the BiOM in clinical trials has resulted in mixed outcomes. For walking speeds faster than 0.75 m/s, Herr et al. 10 found a significant reduction in metabolic cost when individuals with transtibial amputation walked with a powered ankle prosthesis (BiOM) compared to passive, dynamic-response feet. Similarly, Esposito et al. 13 found a 16% decrease in metabolic rate in highly active individuals using the BiOM compared to their prescribed dynamic-response feet. In contrast, Gardinier et al. 14 found no significant differences in metabolic cost between individuals using the BiOM and dynamic-response prostheses. The mixed results of studies evaluating the efficacy of powered prostheses are likely related to a variety of factors, including different subject populations. In the study by Gardinier et al. 14 individuals with the maximum functional classification level
Journal of Biomechanics, 2017
Ankle foot orthoses (AFOs) are designed to improve gait for individuals with neuromuscular condit... more Ankle foot orthoses (AFOs) are designed to improve gait for individuals with neuromuscular conditions and have also been used to reduce energy costs of walking for unimpaired individuals. AFOs influence joint motion and metabolic cost, but how they impact muscle function remains unclear. This study investigated the impact of different stiffness AFOs on medial gastrocnemius muscle (MG) and Achilles tendon (AT) function during two walking speeds. We performed gait analyses for eight unimpaired individuals. Each individual walked at slow and very slow speeds with a 3D printed AFO with no resistance (free hinge condition) and four levels of ankle dorsiflexion stiffness: 0.25Nm/°, 1Nm/°, 2Nm/°, and 3.7Nm/°. Motion capture, ultrasound, and musculoskeletal modeling were used to quantify MG and AT lengths with each AFO condition. Increasing AFO stiffness increased peak AFO dorsiflexion moment with decreased peak knee extension and peak ankle dorsiflexion angles. Overall musculotendon length and peak AT length decreased, while peak MG length increased with increasing AFO stiffness. Peak MG activity, length, and velocity significantly decreased with slower walking speed. This study provides experimental evidence of the impact of AFO stiffness and walking speed on joint kinematics and musculotendon function. These methods can provide insight to improve AFO designs and optimize musculotendon function for rehabilitation, performance, or other goals.
Disability and Rehabilitation: Assistive Technology, 2015
univ-valenciennes.fr
Abstract Recently, the increase of transfemoral amputees from industrial disasters, traffic acci... more Abstract Recently, the increase of transfemoral amputees from industrial disasters, traffic accidents, vascular diseases and aging is emerging as a social issue. For transfemoral amputees, it is very important to recover their lost functions. Myoplasty, which is one of ...
Journal of Biomechanics, 2008
The optimized prosthetic mass distribution was a controversial problem in the previous studies be... more The optimized prosthetic mass distribution was a controversial problem in the previous studies because they are not supported by empirical evidence. The purpose of the present study was to evaluate the effect of prosthetic mass properties by modeling musculoskeletal system, based on the gait analysis data from two above-knee amputees. The joint torque at hip joint was calculated using inverse dynamic analysis as the mass was changed in knee and foot prosthetic components with the same joint kinematics. The results showed that the peak flexion and abduction torque at the hip joint were 5 Nm and 15 Nm when the mass of the knee component was increased, greater than the peak flexion and abduction torque of the control group at the hip joint, respectively. On the other hand, when the mass of the foot component was increased, the peak flexion and abduction torque at the hip joint were 20 Nm and 15 Nm, greater than the peak flexion and abduction torque of the control, respectively. The hip flexion torque was 4.71-fold greater and 7.92-fold greater than the hip abduction torque for the knee mass increase and the foot mass increase on the average, respectively. Therefore, we could conclude that the effect of foot mass increase was more sensitive than that of knee mass increase for the hip flexion torque. On the contrary, the mass properties of the knee and foot components were not sensitive for the hip abduction torque. In addition, optimized prosthetic mass and appropriate mass distributions were needed to promote efficiency of rehabilitation therapy with consideration of musculoskeletal systems of amputees.
2020 8th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob), 2020
Passive ankle prostheses are the most common prosthetic device used by people with lower limb amp... more Passive ankle prostheses are the most common prosthetic device used by people with lower limb amputation. They use an energy recycling mechanism that mimics the behavior of the Achilles tendon and gastrocnemius muscle. The passive ankle prosthetic foot, which is usually made of carbon fiber, similarly stores energy during early to mid-stance by bending under the body’s weight. This energy is returned to the gait as the weight of the body is shifted off the device during terminal stance. However, most current standard of care passive ankle prostheses return the stored energy too early, dissipating most of the energy pushing the limb upward rather than propelling the body forward due to the absence of any muscle control.In this study, we developed an ankle prosthetic timing module that can control the energy return timing of an ankle prostheses, replicating the function of the gastrocnemius muscle. Our ankle prosthetic timing module is designed to be installed onto most current standa...
Many individuals with cerebral palsy (CP) and stroke are prescribed ankle foot orthoses (AFOs) fo... more Many individuals with cerebral palsy (CP) and stroke are prescribed ankle foot orthoses (AFOs) for use during daily life. AFOs have been shown to improve pathologic gait and walking speed in CP and stroke by providing support and alignment. There are many different types of AFOs available such as posterior leaf spring AFOs, rigid AFOs, and articulated AFOs. Further, there are many parameters that can be customized or tuned for each type of AFO, such as stiffness, heel height, shank to vertical angle, and foot plate length. However, how different types of AFOs and the customization of specific parameters impact muscle function remains unclear. The goals of this dissertation were to evaluate how different types of AFOs and different tuning parameters impact gait kinematics and muscle function. Of particular interest is the gastrocnemius, a key muscle that crosses the knee and ankle joints and is commonly tight among individuals with CP or stroke. Gastrocnemius operating length, define...
Introduction Identifying human kinematics is the primary step of biomechanics analyses and clinic... more Introduction Identifying human kinematics is the primary step of biomechanics analyses and clinical evaluation for people with walking disabilities. A typical method for calculating human kinematics is to use a marker-based motion capture system. Such method has a major drawback when capturing motions outside the lab, makes it challenging to measure the various dynamic tasks in daily living. To solve this issue, it has been suggested [1] to use inertial measurement unit (IMU) sensors to capture the motion [1]. However, this method requires attachment of IMU sensors on each body segment. People may feel this is too cumbertom to apply in daily life, limiting the use in real application. Thus, this study aims to investigate the feasibility of capturing the joint angles of lower extremities with a reduced number of IMU sensors using a deep learning algorithm. We hypothesize that if we can train a deep learning model good enough, it can extract the information from a reduced number of IM...
Identifying 3D human walking poses in unconstrained environments has many applications such as en... more Identifying 3D human walking poses in unconstrained environments has many applications such as enabling prosthetists and clinicians to access the amputees’ walking functions outside clinics and helping amputees obtain an optimal walking condition with predictive control. Thus, we propose the wearable motion capture problem of reconstructing and predicting 3D human poses from the wearable IMU sensors and wearable cameras. To solve this challenging problem, we introduce a novel Attention-Oriented Recurrent Neural Network (AttRNet) that contains a sensor-wise attention-oriented recurrent encoder, a reconstruction module, and a dynamic temporal attention-oriented recurrent decoder, to reconstruct the current pose and predict the future poses. To evaluate our approach, we collected a new WearableMotionCapture dataset using wearable IMUs and wearable video cameras, along with the musculoskeletal joint angle ground truth. The proposed AttRNet shows high accuracy on theWearableMotionCapture...
Measurement of human body movement is an essential step in biomechanical analysis. The current st... more Measurement of human body movement is an essential step in biomechanical analysis. The current standard for human motion capture systems uses infrared cameras to track reflective markers placed on the subject. While these systems can accurately track joint kinematics, the analyses are spatially limited to the lab environment. Though Inertial Measurement Unit (IMU) can eliminate the spatial limitations of the motion capture system, those systems are impractical for use in daily living due to the need for many sensors, typically one per body segment. Due to the need for practical and accurate estimation of joint kinematics, this study implements a reduced number of IMU sensors and employs machine learning algorithm to map sensor data to joint angles. Our developed algorithm estimates hip, knee, and ankle angles in the sagittal plane using two shoe-mounted IMU sensors in different practical walking conditions: treadmill, level overground, stair, and slope conditions. Specifically, we p...
Abstracts of the 26th Annual Meeting of the GCMAS, 2021
Scientific Reports, 2021
With the spread of COVID-19, significant emphasis has been placed on mitigation techniques such a... more With the spread of COVID-19, significant emphasis has been placed on mitigation techniques such as mask wearing to slow infectious disease transmission. Widespread use of face coverings has revealed challenges such as mask contamination and waste, presenting an opportunity to improve the current technologies. In response, we have developed the Auto-sanitizing Retractable Mask Optimized for Reusability (ARMOR). ARMOR is a novel, reusable face covering that can be quickly disinfected using an array of ultraviolet C lamps contained within a wearable case. A nanomembrane UVC sensor was used to quantify the intensity of germicidal radiation at 18 different locations on the face covering and determine the necessary exposure time to inactivate SARS-CoV-2 in addition to other viruses and bacteria. After experimentation, it was found that ARMOR successfully provided germicidal radiation to all areas of the mask and will inactivate SARS-CoV-2 in approximately 180 s, H1N1 Influenza in 130 s, a...
Scientific Reports, 2018
Powered ankle prostheses have been designed to reduce the energetic burden that individuals with ... more Powered ankle prostheses have been designed to reduce the energetic burden that individuals with transtibial amputation experience during ambulation. There is an open question regarding how much power the prosthesis should provide, and whether approximating biological ankle kinetics is optimal to reduce the metabolic cost of users. We tested 10 individuals with transtibial amputation walking on a treadmill wearing the BiOM powered ankle prosthesis programmed with 6 different power settings (0-100%), including a prosthetist-chosen setting, chosen to approximate biological ankle kinetics. We measured subjects' metabolic cost of transport (COT) and the BiOM's net ankle work during each condition. Across participants, power settings greater than 50% resulted in lower COT than 0% or 25%. The relationship between power setting, COT, and net ankle work varied considerably between subjects, possibly due to individual adaptation and exploitation of the BiOM's reflexive controller. For all subjects, the best tested power setting was higher than the prosthetist-chosen setting, resulting in a statistically significant and meaningful difference in COT between the best tested and prosthetistchosen power settings. The results of this study demonstrate that individuals with transtibial amputation may benefit from prescribed prosthetic ankle push-off work that exceeds biological norms. Individuals with transtibial amputation spend 10-30% more metabolic energy when walking compared to able-bodied individuals 1-3. This observed increase in energy expenditure may be due to the fact that most ankle prostheses are passive-elastic devices, which store and release energy when in contact with the ground but cannot perform positive net work. In fact, passive-elastic prostheses only produce about an eighth the power of the intact gastrocnemius and soleus muscles 4. This deficit has a significant impact on walking as the majority of the total mechanical power generated during the gait cycle comes from the ankle-foot complex 5-7. As a result of decreased ankle power generation, people with amputation may put forth additional muscular effort from their residual limb or compensate with their intact limb to walk with passive prostheses 8. Additionally, physical fitness may play an important role in determining the metabolic demands of individuals with amputation 9. To overcome these limitations of passive devices, various types of powered ankle prostheses have been developed 10-12. These powered devices use actuators to deliver positive work to the user during the push-off phase, and can potentially alleviate the increased energetic demand that people with amputation experience during walking. Of these devices, only the BiOM powered ankle prosthesis (BionX, Bedford, MA) is currently commercially available. Investigating the efficacy of the BiOM in clinical trials has resulted in mixed outcomes. For walking speeds faster than 0.75 m/s, Herr et al. 10 found a significant reduction in metabolic cost when individuals with transtibial amputation walked with a powered ankle prosthesis (BiOM) compared to passive, dynamic-response feet. Similarly, Esposito et al. 13 found a 16% decrease in metabolic rate in highly active individuals using the BiOM compared to their prescribed dynamic-response feet. In contrast, Gardinier et al. 14 found no significant differences in metabolic cost between individuals using the BiOM and dynamic-response prostheses. The mixed results of studies evaluating the efficacy of powered prostheses are likely related to a variety of factors, including different subject populations. In the study by Gardinier et al. 14 individuals with the maximum functional classification level
Journal of Biomechanics, 2017
Ankle foot orthoses (AFOs) are designed to improve gait for individuals with neuromuscular condit... more Ankle foot orthoses (AFOs) are designed to improve gait for individuals with neuromuscular conditions and have also been used to reduce energy costs of walking for unimpaired individuals. AFOs influence joint motion and metabolic cost, but how they impact muscle function remains unclear. This study investigated the impact of different stiffness AFOs on medial gastrocnemius muscle (MG) and Achilles tendon (AT) function during two walking speeds. We performed gait analyses for eight unimpaired individuals. Each individual walked at slow and very slow speeds with a 3D printed AFO with no resistance (free hinge condition) and four levels of ankle dorsiflexion stiffness: 0.25Nm/°, 1Nm/°, 2Nm/°, and 3.7Nm/°. Motion capture, ultrasound, and musculoskeletal modeling were used to quantify MG and AT lengths with each AFO condition. Increasing AFO stiffness increased peak AFO dorsiflexion moment with decreased peak knee extension and peak ankle dorsiflexion angles. Overall musculotendon length and peak AT length decreased, while peak MG length increased with increasing AFO stiffness. Peak MG activity, length, and velocity significantly decreased with slower walking speed. This study provides experimental evidence of the impact of AFO stiffness and walking speed on joint kinematics and musculotendon function. These methods can provide insight to improve AFO designs and optimize musculotendon function for rehabilitation, performance, or other goals.
Disability and Rehabilitation: Assistive Technology, 2015
univ-valenciennes.fr
Abstract Recently, the increase of transfemoral amputees from industrial disasters, traffic acci... more Abstract Recently, the increase of transfemoral amputees from industrial disasters, traffic accidents, vascular diseases and aging is emerging as a social issue. For transfemoral amputees, it is very important to recover their lost functions. Myoplasty, which is one of ...
Journal of Biomechanics, 2008
The optimized prosthetic mass distribution was a controversial problem in the previous studies be... more The optimized prosthetic mass distribution was a controversial problem in the previous studies because they are not supported by empirical evidence. The purpose of the present study was to evaluate the effect of prosthetic mass properties by modeling musculoskeletal system, based on the gait analysis data from two above-knee amputees. The joint torque at hip joint was calculated using inverse dynamic analysis as the mass was changed in knee and foot prosthetic components with the same joint kinematics. The results showed that the peak flexion and abduction torque at the hip joint were 5 Nm and 15 Nm when the mass of the knee component was increased, greater than the peak flexion and abduction torque of the control group at the hip joint, respectively. On the other hand, when the mass of the foot component was increased, the peak flexion and abduction torque at the hip joint were 20 Nm and 15 Nm, greater than the peak flexion and abduction torque of the control, respectively. The hip flexion torque was 4.71-fold greater and 7.92-fold greater than the hip abduction torque for the knee mass increase and the foot mass increase on the average, respectively. Therefore, we could conclude that the effect of foot mass increase was more sensitive than that of knee mass increase for the hip flexion torque. On the contrary, the mass properties of the knee and foot components were not sensitive for the hip abduction torque. In addition, optimized prosthetic mass and appropriate mass distributions were needed to promote efficiency of rehabilitation therapy with consideration of musculoskeletal systems of amputees.