Tzu-Hao Huang | City College of New York (original) (raw)

Papers by Tzu-Hao Huang

Recent research has demonstrated the benefits of hip exoskeletons for human movement assistance i... more Recent research has demonstrated the benefits of hip exoskeletons for human movement assistance in lab settings with the improved metabolic economy and gait kinematics, but its adoption in community settings has been restricted by factors like the device mass and its torque capabilities. This paper presents the design of a lightweight and high-torque hip exoskeleton with quasi-direct-drive actuation using compact and high torque density motors. The portable hip exoskeleton including battery weighs 3.4 kg and can generate 45 Nm peak torque. Unlike conventional actuation method using high speed and low torque motor with high gear ratio transmission, our hip exoskeleton uses a quasi-direct drive actuation paradigm with high torque density motor and 8:1 low gear ratio transmission to achieve high backdrivability (0.4 Nm) and high control bandwidth (62.4 Hz) which provides physical intelligence (e.g. high backdrivability and high bandwidth) without active control for versatile applicatio...

Sensors

In this paper, the washability of wearable textronic (textile-electronic) devices has been studie... more In this paper, the washability of wearable textronic (textile-electronic) devices has been studied. Two different approaches aiming at designing, producing, and testing robust washable and reliable smart textile systems are presented. The common point of the two approaches is the use of flexible conductive PCB in order to interface the miniaturized rigid (traditional) electronic devices to conductive threads and tracks within the textile flexible fabric and to connect them to antenna, textile electrodes, sensors, actuators, etc. The first approach consists in the use of TPU films (thermoplastic polyurethane) that are deposited by the press under controlled temperature and pressure parameters in order to protect the conductive thread and electrical contacts. The washability of conductive threads and contact resistances between flexible PCB and conductive threads are tested. The second approach is focused on the protection of the whole system-composed of a rigid electronic device, flexible PCB, and textile substrate-by a barrier made of latex. Three types of prototypes were realized and washed. Their reliabilities are studied.

Journal of Medical and Biological Engineering

The needs for light-weight and soft smart clothing in homecare have been rising since the past de... more The needs for light-weight and soft smart clothing in homecare have been rising since the past decade. Many smart textile sensors have been developed and applied to automatic physiological and user-centered environmental status recognition. In the present study, we propose wearable multi-sensor smart clothing for homecare monitoring based on an economic fabric electrode with high elasticity and low resistance. The wearable smart clothing integrated with heterogeneous sensors is capable to measure multiple human biosignals (ECG and respiration), acceleration, and gyro information. Five independent respiratory signals (electric impedance plethysmography, respiratory induced frequency variation, respiratory induced amplitude variation, respiratory induced intensity variation, and respiratory induced movement variation) are obtained. The smart clothing can provide accurate respiratory rate estimation by using three different techniques (Naïve Bayes inference, static Kalman filter, and dynamic Kalman filter). During the static sitting experiments, respiratory induced frequency variation has the best performance; whereas during the running experiments, respiratory induced amplitude variation has the best performance. The Naïve Bayes inference and dynamic Kalman filter have shown good results. The novel smart clothing is soft, elastic, and washable and it is suitable for long-term monitoring in homecare medical service and healthcare industry.

Uncertainty Modelling in Knowledge Engineering and Decision Making, 2016

International Journal of Automation and Smart Technology, 2013

2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013

ABSTRACT Human intention estimation is important for assistive lower limb exoskeleton, and the ta... more ABSTRACT Human intention estimation is important for assistive lower limb exoskeleton, and the task is realized mostly by the dynamics model or the EMG model. Although the dynamics model offers better estimation, it fails when unmodeled disturbances come into the system, such as the ground reaction force. In contrast, the EMG model is non-stationary, and therefore the offline calibrated EMG model is not satisfactory for long-time operation. In this paper, we propose the self-learning scheme with the sliding mode admittance control to overcome the deficiency. In the swing phase, the dynamics model is used to estimate the intention while teaching the EMG model; in the consecutive swing phase, the taught EMG model is used alternatively. In consequence, the self-learning control scheme provides better estimations during the whole operation. In addition, the admittance interface and the sliding mode controller ensure robust performance. The control scheme is justified by the knee orthosis with the backdrivable spring torsion actuator, and the experimental results are prominent.

Seventh International Symposium on Precision Engineering Measurements and Instrumentation, 2011

A fractal approach is employed for the brain motor imagery recognition and applied to brain compu... more A fractal approach is employed for the brain motor imagery recognition and applied to brain computer interface (BCI). The fractal dimension is used as feature extraction and SVM (Support Vector Machine) as feature classifier for on-line BCI applications. The modified Inverse Random Midpoint Displacement (mIRMD) is adopted to calculate the fractal dimensions of EEG signals. The fractal dimensions can effectively reflect the complexity of EEG signals, and are related to the motor imagery tasks. Further, the SVM is employed as the classifier to combine with fractal dimension for motor-imagery recognition and use mutual information to show the difference between two classes. The results are compared with those in the BCI 2003 competition and it shows that our method has better classification accuracy and mutual information (MI).

2013 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2013

ABSTRACT The estimation of the human applying torque is critical in many applications, especially... more ABSTRACT The estimation of the human applying torque is critical in many applications, especially in the design of assistive exoskeleton. The most common approaches are the estimation by the inverse dynamics or by the EMG signal. However, the EMG-based torque estimation is not always stable owing to the sweats of skin, the noise from posture change, and the nonlinear mapping between the EMG signal and the human torque. In addition, the estimation based on the dynamic model is unstable in the multi-DOFs system and especially in the existence of exogenous disturbance, such as ground reaction force. Therefore, we propose the Bayesian human intention estimator and the graphical model of human-exoskeleton system to solve these issues. Through the experiments, the proposed method can merge the information from both the EMG signal and dynamic model, and can make the estimated torque more stable.

2012 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2012

ABSTRACT Simultaneously considering the physical interaction between the user and the robot withi... more ABSTRACT Simultaneously considering the physical interaction between the user and the robot within safety and performance constraints in rehabilitation and human walking situations, this paper proposes a new backdrivable torsion spring actuator (BTSA) with hybrid control that switches between direct electromyography (EMG) biofeedback control and zero impedance control, to provide a novel rehabilitation training and walking assistance mechanism for humans. The proposed backdrivable 1-DOF serial elastic actuator is designed to achieve intrinsic safety, compliance properties, and control performance. The proposed mechanical system can provide desirable backdrivable property and softer stiffness than that of traditional robots. In additional, the proposed hybrid control not only considers the assistive function, when human assistance is required, but also the compliance property, when assistance is not needed. Compared to state-of-the-art assistive methods, the BTSA with the proposed hybrid control system is unique in that it can simultaneously achieve assistance control through EMG biofeedback and compliance control through zero impedance control. A simple human-robot interaction model is built to investigate performance and explain the whole control concept. Further, a knee exoskeleton is built and three kinds of controls are used on a human subject to demonstrate the difference between them. Both simulation and experimental results show that the proposed BTSA mechanism with hybrid control offers the desired properties.

Journal of Neuroscience and Neuroengineering, 2013

ABSTRACT

2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2011

Focusing on the physical interaction between people and machines within safety constraints in ver... more Focusing on the physical interaction between people and machines within safety constraints in versatile situations, this paper proposes a new, efficient actuation approach, continuous-state coupled elastic actuation (CCEA), to provide oncoming human-machine systems with an intrinsic programmable stiffness capacity to shape output force corresponding to the deviation between human motions and set positions of the system. As one of all the possible CCEA systems, a prototype of a 2-DOF coupled elastic actuator is designed to provide a compromise between performance and safety. Using a pair of antagonistic four-bar linkages, the inherent stiffness of the system can be adjusted dynamically. Compared to the state-of-the-art variable stiffness actuators, the CCEA system is unique in that it can achieve near zero mechanical stiffness in an efficient way. In addition, a human-robot interaction model is built to investigate the controlled bandwidth and safety of the CCEA system. For the application of assistive exercises, this study also proposes two kinds of controls for assistive exercises. Finally, a CCEA exoskeleton is built for elbow rehabilitation. Both simulations and experiments are conducted to show some desired properties of the proposed CCEA system.

2011 IEEE International Conference on Systems, Man, and Cybernetics, 2011

ABSTRACT

Focusing on physical human-robot interaction, biosignal feedback allows a rehabilitation and assi... more Focusing on physical human-robot interaction, biosignal feedback allows a rehabilitation and assistive robotic system possess many advantages, such as providing human intention estimations, suitable treatment evaluations, capacity of generating power assistive strategies in advance, etc. In general, electromyogram (EMG), angle, and force signals can be used to estimate the intention of the human by two kinds of human intention estimators, such as binary intention and continuous intention estimators. In this paper, we propose a hybrid estimator of human intention using a Support Vector Machine (SVM) and Linear Regression to recognize human intention and apply it to a new rehabilitation and assistive system, the coupled elastic actuation robotic system (CEBOT), which is designed to enhance the human mobility. With unique intrinsic adjustable stiffness and human intention recognition capacity, the CEBOT, possessing inherent safety, gentler treatment, suitable motion patterns, capacity ...

Medical & Biological Engineering & Computing, 2006

De Quervain's tenosynovit... more De Quervain's tenosynovitis is often observed on repetitive flexion of the thumb. In the clinical setting, the conservative treatment is usually an applied thumbspica splint to immobilize the thumb. However, the traditional thumbspica splint is bulky and heavy. Thus, this study used the finite element (FE) method to remove redundant material in order to reduce the splint's weight and increase ventilation. An FE model of a thumbspica splint was constructed using ANSYS9.0 software. A maximum lateral thumb pinch force of 98 N was used as the input loading condition for the FE model. This study implemented topology optimization and design optimization to seek the optimal thickness and shape of the splint. This new design was manufactured and compared with the traditional thumbspica splint. Ten thumbspica splints were tested in a materials testing system, and statistically analyzed using an independent t test. The optimal thickness of the thumbspica splint was 3.2 mm. The new design is not significantly different from the traditional splint in the immobilization effect. However, the volume of this new design has been reduced by about 35%. This study produced a new thumbspica splint shape with less volume, but had a similar immobilization effect compared to the traditional shape. In a clinical setting, this result can be used by the occupational therapist as a reference for manufacturing lighter thumbspica splints for patients with de Quervain's tenosynovitis.

Journal of Intelligent & Robotic Systems, 2013

Advanced Robotics, 2011

ABSTRACT

Recent research has demonstrated the benefits of hip exoskeletons for human movement assistance i... more Recent research has demonstrated the benefits of hip exoskeletons for human movement assistance in lab settings with the improved metabolic economy and gait kinematics, but its adoption in community settings has been restricted by factors like the device mass and its torque capabilities. This paper presents the design of a lightweight and high-torque hip exoskeleton with quasi-direct-drive actuation using compact and high torque density motors. The portable hip exoskeleton including battery weighs 3.4 kg and can generate 45 Nm peak torque. Unlike conventional actuation method using high speed and low torque motor with high gear ratio transmission, our hip exoskeleton uses a quasi-direct drive actuation paradigm with high torque density motor and 8:1 low gear ratio transmission to achieve high backdrivability (0.4 Nm) and high control bandwidth (62.4 Hz) which provides physical intelligence (e.g. high backdrivability and high bandwidth) without active control for versatile applicatio...

Sensors

In this paper, the washability of wearable textronic (textile-electronic) devices has been studie... more In this paper, the washability of wearable textronic (textile-electronic) devices has been studied. Two different approaches aiming at designing, producing, and testing robust washable and reliable smart textile systems are presented. The common point of the two approaches is the use of flexible conductive PCB in order to interface the miniaturized rigid (traditional) electronic devices to conductive threads and tracks within the textile flexible fabric and to connect them to antenna, textile electrodes, sensors, actuators, etc. The first approach consists in the use of TPU films (thermoplastic polyurethane) that are deposited by the press under controlled temperature and pressure parameters in order to protect the conductive thread and electrical contacts. The washability of conductive threads and contact resistances between flexible PCB and conductive threads are tested. The second approach is focused on the protection of the whole system-composed of a rigid electronic device, flexible PCB, and textile substrate-by a barrier made of latex. Three types of prototypes were realized and washed. Their reliabilities are studied.

Journal of Medical and Biological Engineering

The needs for light-weight and soft smart clothing in homecare have been rising since the past de... more The needs for light-weight and soft smart clothing in homecare have been rising since the past decade. Many smart textile sensors have been developed and applied to automatic physiological and user-centered environmental status recognition. In the present study, we propose wearable multi-sensor smart clothing for homecare monitoring based on an economic fabric electrode with high elasticity and low resistance. The wearable smart clothing integrated with heterogeneous sensors is capable to measure multiple human biosignals (ECG and respiration), acceleration, and gyro information. Five independent respiratory signals (electric impedance plethysmography, respiratory induced frequency variation, respiratory induced amplitude variation, respiratory induced intensity variation, and respiratory induced movement variation) are obtained. The smart clothing can provide accurate respiratory rate estimation by using three different techniques (Naïve Bayes inference, static Kalman filter, and dynamic Kalman filter). During the static sitting experiments, respiratory induced frequency variation has the best performance; whereas during the running experiments, respiratory induced amplitude variation has the best performance. The Naïve Bayes inference and dynamic Kalman filter have shown good results. The novel smart clothing is soft, elastic, and washable and it is suitable for long-term monitoring in homecare medical service and healthcare industry.

Uncertainty Modelling in Knowledge Engineering and Decision Making, 2016

International Journal of Automation and Smart Technology, 2013

2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013

ABSTRACT Human intention estimation is important for assistive lower limb exoskeleton, and the ta... more ABSTRACT Human intention estimation is important for assistive lower limb exoskeleton, and the task is realized mostly by the dynamics model or the EMG model. Although the dynamics model offers better estimation, it fails when unmodeled disturbances come into the system, such as the ground reaction force. In contrast, the EMG model is non-stationary, and therefore the offline calibrated EMG model is not satisfactory for long-time operation. In this paper, we propose the self-learning scheme with the sliding mode admittance control to overcome the deficiency. In the swing phase, the dynamics model is used to estimate the intention while teaching the EMG model; in the consecutive swing phase, the taught EMG model is used alternatively. In consequence, the self-learning control scheme provides better estimations during the whole operation. In addition, the admittance interface and the sliding mode controller ensure robust performance. The control scheme is justified by the knee orthosis with the backdrivable spring torsion actuator, and the experimental results are prominent.

Seventh International Symposium on Precision Engineering Measurements and Instrumentation, 2011

A fractal approach is employed for the brain motor imagery recognition and applied to brain compu... more A fractal approach is employed for the brain motor imagery recognition and applied to brain computer interface (BCI). The fractal dimension is used as feature extraction and SVM (Support Vector Machine) as feature classifier for on-line BCI applications. The modified Inverse Random Midpoint Displacement (mIRMD) is adopted to calculate the fractal dimensions of EEG signals. The fractal dimensions can effectively reflect the complexity of EEG signals, and are related to the motor imagery tasks. Further, the SVM is employed as the classifier to combine with fractal dimension for motor-imagery recognition and use mutual information to show the difference between two classes. The results are compared with those in the BCI 2003 competition and it shows that our method has better classification accuracy and mutual information (MI).

2013 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2013

ABSTRACT The estimation of the human applying torque is critical in many applications, especially... more ABSTRACT The estimation of the human applying torque is critical in many applications, especially in the design of assistive exoskeleton. The most common approaches are the estimation by the inverse dynamics or by the EMG signal. However, the EMG-based torque estimation is not always stable owing to the sweats of skin, the noise from posture change, and the nonlinear mapping between the EMG signal and the human torque. In addition, the estimation based on the dynamic model is unstable in the multi-DOFs system and especially in the existence of exogenous disturbance, such as ground reaction force. Therefore, we propose the Bayesian human intention estimator and the graphical model of human-exoskeleton system to solve these issues. Through the experiments, the proposed method can merge the information from both the EMG signal and dynamic model, and can make the estimated torque more stable.

2012 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2012

ABSTRACT Simultaneously considering the physical interaction between the user and the robot withi... more ABSTRACT Simultaneously considering the physical interaction between the user and the robot within safety and performance constraints in rehabilitation and human walking situations, this paper proposes a new backdrivable torsion spring actuator (BTSA) with hybrid control that switches between direct electromyography (EMG) biofeedback control and zero impedance control, to provide a novel rehabilitation training and walking assistance mechanism for humans. The proposed backdrivable 1-DOF serial elastic actuator is designed to achieve intrinsic safety, compliance properties, and control performance. The proposed mechanical system can provide desirable backdrivable property and softer stiffness than that of traditional robots. In additional, the proposed hybrid control not only considers the assistive function, when human assistance is required, but also the compliance property, when assistance is not needed. Compared to state-of-the-art assistive methods, the BTSA with the proposed hybrid control system is unique in that it can simultaneously achieve assistance control through EMG biofeedback and compliance control through zero impedance control. A simple human-robot interaction model is built to investigate performance and explain the whole control concept. Further, a knee exoskeleton is built and three kinds of controls are used on a human subject to demonstrate the difference between them. Both simulation and experimental results show that the proposed BTSA mechanism with hybrid control offers the desired properties.

Journal of Neuroscience and Neuroengineering, 2013

ABSTRACT

2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2011

Focusing on the physical interaction between people and machines within safety constraints in ver... more Focusing on the physical interaction between people and machines within safety constraints in versatile situations, this paper proposes a new, efficient actuation approach, continuous-state coupled elastic actuation (CCEA), to provide oncoming human-machine systems with an intrinsic programmable stiffness capacity to shape output force corresponding to the deviation between human motions and set positions of the system. As one of all the possible CCEA systems, a prototype of a 2-DOF coupled elastic actuator is designed to provide a compromise between performance and safety. Using a pair of antagonistic four-bar linkages, the inherent stiffness of the system can be adjusted dynamically. Compared to the state-of-the-art variable stiffness actuators, the CCEA system is unique in that it can achieve near zero mechanical stiffness in an efficient way. In addition, a human-robot interaction model is built to investigate the controlled bandwidth and safety of the CCEA system. For the application of assistive exercises, this study also proposes two kinds of controls for assistive exercises. Finally, a CCEA exoskeleton is built for elbow rehabilitation. Both simulations and experiments are conducted to show some desired properties of the proposed CCEA system.

2011 IEEE International Conference on Systems, Man, and Cybernetics, 2011

ABSTRACT

Focusing on physical human-robot interaction, biosignal feedback allows a rehabilitation and assi... more Focusing on physical human-robot interaction, biosignal feedback allows a rehabilitation and assistive robotic system possess many advantages, such as providing human intention estimations, suitable treatment evaluations, capacity of generating power assistive strategies in advance, etc. In general, electromyogram (EMG), angle, and force signals can be used to estimate the intention of the human by two kinds of human intention estimators, such as binary intention and continuous intention estimators. In this paper, we propose a hybrid estimator of human intention using a Support Vector Machine (SVM) and Linear Regression to recognize human intention and apply it to a new rehabilitation and assistive system, the coupled elastic actuation robotic system (CEBOT), which is designed to enhance the human mobility. With unique intrinsic adjustable stiffness and human intention recognition capacity, the CEBOT, possessing inherent safety, gentler treatment, suitable motion patterns, capacity ...

Medical & Biological Engineering & Computing, 2006

De Quervain's tenosynovit... more De Quervain's tenosynovitis is often observed on repetitive flexion of the thumb. In the clinical setting, the conservative treatment is usually an applied thumbspica splint to immobilize the thumb. However, the traditional thumbspica splint is bulky and heavy. Thus, this study used the finite element (FE) method to remove redundant material in order to reduce the splint's weight and increase ventilation. An FE model of a thumbspica splint was constructed using ANSYS9.0 software. A maximum lateral thumb pinch force of 98 N was used as the input loading condition for the FE model. This study implemented topology optimization and design optimization to seek the optimal thickness and shape of the splint. This new design was manufactured and compared with the traditional thumbspica splint. Ten thumbspica splints were tested in a materials testing system, and statistically analyzed using an independent t test. The optimal thickness of the thumbspica splint was 3.2 mm. The new design is not significantly different from the traditional splint in the immobilization effect. However, the volume of this new design has been reduced by about 35%. This study produced a new thumbspica splint shape with less volume, but had a similar immobilization effect compared to the traditional shape. In a clinical setting, this result can be used by the occupational therapist as a reference for manufacturing lighter thumbspica splints for patients with de Quervain's tenosynovitis.

Journal of Intelligent & Robotic Systems, 2013

Advanced Robotics, 2011

ABSTRACT