The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform
J Sladek - One of the best experts on this subject based on the ideXlab platform.
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axial symmetric elasticity analysis in non homogeneous bodies under Gravitational Load by triple reciprocity boundary element method
International Journal for Numerical Methods in Engineering, 2009Co-Authors: Yoshihiro Ochiai, V Sladek, J SladekAbstract:In general, internal cells are required to solve elasticity problems by involving a Gravitational Load in non-homogeneous bodies with variable mass density when using a conventional boundary element method (BEM). Then, the effect of mesh reduction is not achieved and one of the main merits of the BEM, which is the simplicity of data preparation, is lost. In this study, it is shown that the domain cells can be avoided by using the triple-reciprocity BEM formulation, where the density of domain integral is expressed in terms of other fields that are represented by boundary densities and/or source densities at isolated interior points. Utilizing the rotational symmetry, the triple-reciprocity BEM formulation is developed for axially symmetric elasticity problems in non-homogeneous bodies under Gravitational force. A new computer program was developed and applied to solve several test problems.
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Axial symmetric elasticity analysis in non‐homogeneous bodies under Gravitational Load by triple‐reciprocity boundary element method
International Journal for Numerical Methods in Engineering, 2009Co-Authors: Yoshihiro Ochiai, V Sladek, J SladekAbstract:In general, internal cells are required to solve elasticity problems by involving a Gravitational Load in non-homogeneous bodies with variable mass density when using a conventional boundary element method (BEM). Then, the effect of mesh reduction is not achieved and one of the main merits of the BEM, which is the simplicity of data preparation, is lost. In this study, it is shown that the domain cells can be avoided by using the triple-reciprocity BEM formulation, where the density of domain integral is expressed in terms of other fields that are represented by boundary densities and/or source densities at isolated interior points. Utilizing the rotational symmetry, the triple-reciprocity BEM formulation is developed for axially symmetric elasticity problems in non-homogeneous bodies under Gravitational force. A new computer program was developed and applied to solve several test problems.
Gregory S Sawicki - One of the best experts on this subject based on the ideXlab platform.
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Erratum: More is not always better: Modeling the effects of elastic exoskeleton compliance on underlying ankle muscle-tendon dynamics (Bioinspiration and Biomimetics (2014) 9 (046018))
Bioinspiration and Biomimetics, 2015Co-Authors: Benjamin D Robertson, Dominic James Farris, Gregory S SawickiAbstract:Development of robotic exoskeletons to assist/enhance human locomotor performance involves lengthy prototyping, testing, and analysis. This process is further convoluted by variability in limb/body morphology and preferred gait patterns between individuals. In an attempt to expedite this process, and establish a physiological basis for actuator prescription, we developed a simple, predictive model of human neuromechanical adaptation to a passive elastic exoskeleton applied at the ankle joint during a functional task. We modeled the human triceps surae-Achilles tendon muscle tendon unit (MTU) as a single Hill-type muscle, or contractile element (CE), and series tendon, or series elastic element (SEE). This modeled system was placed under Gravitational Load and underwent cyclic stimulation at a regular frequency (i.e. hopping) with and without exoskeleton (Exo) assistance. We explored the effect that both Exo stiffness [Formula: see text] and muscle activation [Formula: see text] had on combined MTU and Exo (MTU + Exo), MTU, and CE/SEE mechanics and energetics. Model accuracy was verified via qualitative and quantitative comparisons between modeled and prior experimental outcomes. We demonstrated that reduced [Formula: see text] can be traded for increased [Formula: see text] to maintain consistent MTU + Exo mechanics (i.e. average positive power [Formula: see text] output) from an unassisted condition (i.e. [Formula: see text]). For these regions of parameter space, our model predicted a reduction in MTU force, SEE energy cycling, and metabolic rate [Formula: see text], as well as constant CE [Formula: see text] output compared to unassisted conditions. This agreed with previous experimental observations, demonstrating our model's predictive ability. Model predictions also provided insight into mechanisms of metabolic cost minimization, and/or enhanced mechanical performance, and we concluded that both of these outcomes cannot be achieved simultaneously, and that one must come at the detriment of the other in a spring-assisted compliant MTU.
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More is not always better: Modeling the effects of elastic exoskeleton compliance on underlying ankle muscle-tendon dynamics
Bioinspiration and Biomimetics, 2014Co-Authors: Benjamin D Robertson, Dominic James Farris, Gregory S SawickiAbstract:Development of robotic exoskeletons to assist/enhance human locomotor performance involves lengthy prototyping, testing, and analysis. This process is further convoluted by variability in limb/body morphology and preferred gait patterns between individuals. In an attempt to expedite this process, and establish a physiological basis for actuator prescription, we developed a simple, predictive model of human neuromechanical adaptation to a passive elastic exoskeleton applied at the ankle joint during a functional task. We modeled the human triceps surae-Achilles tendon muscle tendon unit (MTU) as a single Hill-type muscle, or contractile element (CE), and series tendon, or series elastic element (SEE). This modeled system was placed under Gravitational Load and underwent cyclic stimulation at a regular frequency (i.e. hopping) with and without exoskeleton (Exo) assistance. We explored the effect that both Exo stiffness [Formula: see text] and muscle activation [Formula: see text] had on combined MTU and Exo (MTU + Exo), MTU, and CE/SEE mechanics and energetics. Model accuracy was verified via qualitative and quantitative comparisons between modeled and prior experimental outcomes. We demonstrated that reduced [Formula: see text] can be traded for increased [Formula: see text] to maintain consistent MTU + Exo mechanics (i.e. average positive power [Formula: see text] output) from an unassisted condition (i.e. [Formula: see text]). For these regions of parameter space, our model predicted a reduction in MTU force, SEE energy cycling, and metabolic rate [Formula: see text], as well as constant CE [Formula: see text] output compared to unassisted conditions. This agreed with previous experimental observations, demonstrating our model's predictive ability. Model predictions also provided insight into mechanisms of metabolic cost minimization, and/or enhanced mechanical performance, and we concluded that both of these outcomes cannot be achieved simultaneously, and that one must come at the detriment of the other in a spring-assisted compliant MTU.
Yoshihiro Ochiai - One of the best experts on this subject based on the ideXlab platform.
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axial symmetric elasticity analysis in non homogeneous bodies under Gravitational Load by triple reciprocity boundary element method
International Journal for Numerical Methods in Engineering, 2009Co-Authors: Yoshihiro Ochiai, V Sladek, J SladekAbstract:In general, internal cells are required to solve elasticity problems by involving a Gravitational Load in non-homogeneous bodies with variable mass density when using a conventional boundary element method (BEM). Then, the effect of mesh reduction is not achieved and one of the main merits of the BEM, which is the simplicity of data preparation, is lost. In this study, it is shown that the domain cells can be avoided by using the triple-reciprocity BEM formulation, where the density of domain integral is expressed in terms of other fields that are represented by boundary densities and/or source densities at isolated interior points. Utilizing the rotational symmetry, the triple-reciprocity BEM formulation is developed for axially symmetric elasticity problems in non-homogeneous bodies under Gravitational force. A new computer program was developed and applied to solve several test problems.
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Axial symmetric elasticity analysis in non‐homogeneous bodies under Gravitational Load by triple‐reciprocity boundary element method
International Journal for Numerical Methods in Engineering, 2009Co-Authors: Yoshihiro Ochiai, V Sladek, J SladekAbstract:In general, internal cells are required to solve elasticity problems by involving a Gravitational Load in non-homogeneous bodies with variable mass density when using a conventional boundary element method (BEM). Then, the effect of mesh reduction is not achieved and one of the main merits of the BEM, which is the simplicity of data preparation, is lost. In this study, it is shown that the domain cells can be avoided by using the triple-reciprocity BEM formulation, where the density of domain integral is expressed in terms of other fields that are represented by boundary densities and/or source densities at isolated interior points. Utilizing the rotational symmetry, the triple-reciprocity BEM formulation is developed for axially symmetric elasticity problems in non-homogeneous bodies under Gravitational force. A new computer program was developed and applied to solve several test problems.
Benjamin D Robertson - One of the best experts on this subject based on the ideXlab platform.
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Erratum: More is not always better: Modeling the effects of elastic exoskeleton compliance on underlying ankle muscle-tendon dynamics (Bioinspiration and Biomimetics (2014) 9 (046018))
Bioinspiration and Biomimetics, 2015Co-Authors: Benjamin D Robertson, Dominic James Farris, Gregory S SawickiAbstract:Development of robotic exoskeletons to assist/enhance human locomotor performance involves lengthy prototyping, testing, and analysis. This process is further convoluted by variability in limb/body morphology and preferred gait patterns between individuals. In an attempt to expedite this process, and establish a physiological basis for actuator prescription, we developed a simple, predictive model of human neuromechanical adaptation to a passive elastic exoskeleton applied at the ankle joint during a functional task. We modeled the human triceps surae-Achilles tendon muscle tendon unit (MTU) as a single Hill-type muscle, or contractile element (CE), and series tendon, or series elastic element (SEE). This modeled system was placed under Gravitational Load and underwent cyclic stimulation at a regular frequency (i.e. hopping) with and without exoskeleton (Exo) assistance. We explored the effect that both Exo stiffness [Formula: see text] and muscle activation [Formula: see text] had on combined MTU and Exo (MTU + Exo), MTU, and CE/SEE mechanics and energetics. Model accuracy was verified via qualitative and quantitative comparisons between modeled and prior experimental outcomes. We demonstrated that reduced [Formula: see text] can be traded for increased [Formula: see text] to maintain consistent MTU + Exo mechanics (i.e. average positive power [Formula: see text] output) from an unassisted condition (i.e. [Formula: see text]). For these regions of parameter space, our model predicted a reduction in MTU force, SEE energy cycling, and metabolic rate [Formula: see text], as well as constant CE [Formula: see text] output compared to unassisted conditions. This agreed with previous experimental observations, demonstrating our model's predictive ability. Model predictions also provided insight into mechanisms of metabolic cost minimization, and/or enhanced mechanical performance, and we concluded that both of these outcomes cannot be achieved simultaneously, and that one must come at the detriment of the other in a spring-assisted compliant MTU.
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More is not always better: Modeling the effects of elastic exoskeleton compliance on underlying ankle muscle-tendon dynamics
Bioinspiration and Biomimetics, 2014Co-Authors: Benjamin D Robertson, Dominic James Farris, Gregory S SawickiAbstract:Development of robotic exoskeletons to assist/enhance human locomotor performance involves lengthy prototyping, testing, and analysis. This process is further convoluted by variability in limb/body morphology and preferred gait patterns between individuals. In an attempt to expedite this process, and establish a physiological basis for actuator prescription, we developed a simple, predictive model of human neuromechanical adaptation to a passive elastic exoskeleton applied at the ankle joint during a functional task. We modeled the human triceps surae-Achilles tendon muscle tendon unit (MTU) as a single Hill-type muscle, or contractile element (CE), and series tendon, or series elastic element (SEE). This modeled system was placed under Gravitational Load and underwent cyclic stimulation at a regular frequency (i.e. hopping) with and without exoskeleton (Exo) assistance. We explored the effect that both Exo stiffness [Formula: see text] and muscle activation [Formula: see text] had on combined MTU and Exo (MTU + Exo), MTU, and CE/SEE mechanics and energetics. Model accuracy was verified via qualitative and quantitative comparisons between modeled and prior experimental outcomes. We demonstrated that reduced [Formula: see text] can be traded for increased [Formula: see text] to maintain consistent MTU + Exo mechanics (i.e. average positive power [Formula: see text] output) from an unassisted condition (i.e. [Formula: see text]). For these regions of parameter space, our model predicted a reduction in MTU force, SEE energy cycling, and metabolic rate [Formula: see text], as well as constant CE [Formula: see text] output compared to unassisted conditions. This agreed with previous experimental observations, demonstrating our model's predictive ability. Model predictions also provided insight into mechanisms of metabolic cost minimization, and/or enhanced mechanical performance, and we concluded that both of these outcomes cannot be achieved simultaneously, and that one must come at the detriment of the other in a spring-assisted compliant MTU.
Wan Kyun Chung - One of the best experts on this subject based on the ideXlab platform.
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External torque sensing algorithm for flexible-joint robot based on disturbance observer structure
2014 IEEE RSJ International Conference on Intelligent Robots and Systems, 2014Co-Authors: Young Jin Park, Wan Kyun ChungAbstract:Since a flexible-joint robot (FJR) consists of two subsystems centered around joint-torque (J-T) sensors, there are two independent resultant torques, i.e., an actuating motor torque and an external link torque, applied to the system. In this paper, an external torque sensing algorithm for the FJR is proposed to estimate both torques simultaneously by using the disturbance observing property of the disturbance observer (DOB). The proposed algorithm has no restriction of selecting Q-filter such that a high-performance low-pass filter can be applied for accurate estimation. The estimated torques can be very useful for FJR applications. As an illustrative example, the estimated actuating motor torque containing the motor disturbance is utilized to the motor disturbance compensation of the FJR with modified Q-filter due to the compensation feedback loop. The basic structure of the proposed algorithm is illustrated, and the performance is verified though a custom-designed experimental testbed for a vertical configuration with a Gravitational Load.
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Unified external torque-sensing algorithm for flexible-joint robot based on Kalman filter
2013 10th International Conference on Ubiquitous Robots and Ambient Intelligence URAI 2013, 2013Co-Authors: Young Jin Park, Wan Kyun ChungAbstract:The external torque estimation problem in a 1-degree-of-freedom flexible-joint robot system with a joint torque sensor is revisited. The flexible-joint robot has two dynamics, motor-side and link-side dynamics, making the problem more complicated. An external torque-sensing algorithm for the flexible-joint robot is proposed, which treats these two dynamics simultaneously for extracting external torques applied to the system. The basic structure of the proposed algorithm is illustrated, and the performance is verified by a custom-designed experimental apparatus for vertical configuration with a Gravitational Load.
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External torque-sensing algorithm for flexible-joint robot based on Kalman filter
Electronics Letters, 2013Co-Authors: Young Jin Park, Wan Kyun ChungAbstract:The external torque estimation problem in a 1-degree-of-freedom flexible-joint robot system with a joint torque sensor is revisited. The flexible-joint robot has two dynamics, motor-side and link-side dynamics, making the problem more complicated. An external torque-sensing algorithm for the flexible-joint robot is proposed, which treats these two dynamics simultaneously for extracting external torques applied to the system. The basic structure of the proposed algorithm is illustrated, and the performance is verified by a custom-designed experimental apparatus for vertical configuration with a Gravitational Load.
