The Experts below are selected from a list of 53310 Experts worldwide ranked by ideXlab platform
Ronald J. Triolo - One of the best experts on this subject based on the ideXlab platform.
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center of Mass Acceleration feedback control of standing balance by functional neuromuscular stimulation against external postural perturbations
IEEE Transactions on Biomedical Engineering, 2013Co-Authors: Raviraj Nataraj, Musa L. Audu, Ronald J. TrioloAbstract:This study investigated the use of center of Mass (COM) Acceleration feedback for improving performance of a functional neuromuscular stimulation control system to restore standing function to a subject with complete, thoracic-level spinal cord injury. The approach for linearly relating changes in muscle stimulation to changes in COM Acceleration was verified experimentally and subsequently produced data to create an input-output map driven by sensor feedback. The feedback gains were systematically tuned to reduce upper extremity (UE) loads applied to an instrumented support device while resisting external postural disturbances. Total body COM Acceleration was accurately estimated (>;89% variance explained) using 3-D outputs of two accelerometers mounted on the pelvis and torso. Compared to constant muscle stimulation employed clinically, feedback control of stimulation reduced UE loading by 33%. COM Acceleration feedback is advantageous in constructing a standing neuroprosthesis since it provides the basis for a comprehensive control synergy about a global, dynamic variable and requires minimal instrumentation. Future work should include tuning and testing the feedback control system during functional reaching activity that is more indicative of activities of daily living.
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Comparing joint kinematics and center of Mass Acceleration as feedback for control of standing balance by functional neuromuscular stimulation.
Journal of neuroengineering and rehabilitation, 2012Co-Authors: Raviraj Nataraj, Musa L. Audu, Ronald J. TrioloAbstract:The purpose of this study was to determine the comparative effectiveness of feedback control systems for maintaining standing balance based on joint kinematics or total body center of Mass (COM) Acceleration, and assess their clinical practicality for standing neuroprostheses after spinal cord injury (SCI). In simulation, controller performance was measured according to the upper extremity effort required to stabilize a three-dimensional model of bipedal standing against a variety of postural disturbances. Three cases were investigated: proportional-derivative control based on joint kinematics alone, COM Acceleration feedback alone, and combined joint kinematics and COM Acceleration feedback. Additionally, pilot data was collected during external perturbations of an individual with SCI standing with functional neuromuscular stimulation (FNS), and the resulting joint kinematics and COM Acceleration data was analyzed. Compared to the baseline case of maximal constant muscle excitations, the three control systems reduced the mean upper extremity loading by 51%, 43% and 56%, respectively against external force-pulse perturbations. Controller robustness was defined as the degradation in performance with increasing levels of input errors expected with clinical deployment of sensor-based feedback. At error levels typical for body-mounted inertial sensors, performance degradation due to sensor noise and placement were negligible. However, at typical tracking error levels, performance could degrade as much as 86% for joint kinematics feedback and 35% for COM Acceleration feedback. Pilot data indicated that COM Acceleration could be estimated with a few well-placed sensors and efficiently captures information related to movement synergies observed during perturbed bipedal standing following SCI. Overall, COM Acceleration feedback may be a more feasible solution for control of standing with FNS given its superior robustness and small number of inputs required.
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Center of Mass Acceleration feedback control for standing by functional neuromuscular stimulation: a simulation study.
Journal of rehabilitation research and development, 2012Co-Authors: Raviraj Nataraj, Musa L. Audu, Robert F. Kirsch, Ronald J. TrioloAbstract:The potential efficacy of total body center of Mass (COM) Acceleration for feedback control of standing balance by functional neuromuscular stimulation (FNS) following spinal cord injury (SCI) was investigated. COM Acceleration may be a viable alternative to conventional joint kinematics due to its rapid responsiveness, focal representation of COM dynamics, and ease of measurement. A computational procedure was developed using an anatomically-realistic, three-dimensional, bipedal biomechanical model to determine optimal patterns of muscle excitations to produce targeted effects upon COM Acceleration from erect stance. The procedure was verified with electromyographic data collected from standing able-bodied subjects undergoing systematic perturbations. Using 16 muscle groups targeted by existing implantable neuroprostheses, data were generated to train an artificial neural network (ANN)-based controller in simulation. During forward simulations, proportional feedback of COM Acceleration drove the ANN to produce muscle excitation patterns countering the effects of applied perturbations. Feedback gains were optimized to minimize upper extremity (UE) loading required to stabilize against disturbances. Compared to the clinical case of maximum constant excitation, the controller reduced UE loading by 43% in resisting external perturbations and by 51% during simulated one-arm reaching. Future work includes performance assessment against expected measurement errors and developing user-specific control systems.
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Center of Mass Acceleration feedback control of functional neuromuscular stimulation for standing in presence of internal postural perturbations
Journal of rehabilitation research and development, 2012Co-Authors: Raviraj Nataraj, Musa L. Audu, Ronald J. TrioloAbstract:This study determined the feasibility and performance of center of Mass (COM) Acceleration feedback control of a neuroprosthesis utilizing functional neuromuscular stimulation (FNS) to restore standing balance to a single subject paralyzed by a motor and sensory complete, thoracic-level spinal cord injury (SCI). An artificial neural network (ANN) was created to map gain-modulated changes in total body COM Acceleration estimated from body-mounted sensors to optimal changes in stimulation required to maintain standing. Feedback gains were systematically tuned to minimize the upper extremity (UE) loads applied by the subject to an instrumented support device during internally generated postural perturbations produced by volitional reaching and object manipulation. Total body COM Acceleration was accurately estimated (> 90% variance explained) from two three-dimensional (3-D) accelerometers mounted on the pelvis and torso. Compared to constant muscle stimulation employed clinically, COM Acceleration feedback control of stimulation improved standing performance by reducing the UE loading required to resist internal postural disturbances by 27%. This case study suggests that COM Acceleration feedback could potentially be advantageous in a standing neuroprosthesis since it can be implemented with only a few feedback parameters and requires minimal instrumentation for comprehensive, 3-D control of dynamic standing function.
L. S. Chou - One of the best experts on this subject based on the ideXlab platform.
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Region of Stability Derived by Center of Mass Acceleration Better Identifies Individuals with Difficulty in Sit-to-Stand Movement
Annals of Biomedical Engineering, 2014Co-Authors: M. Fujimoto, L. S. ChouAbstract:Poor performance of sit-to-stand (STS) has been identified as one of the predictors of fall risk among elderly adults. This study examined differences in the whole body center of Mass (COM) kinematic variables in relation to the regions of stability between elderly adults with difficulty in STS and healthy individuals. Whole body motion data while performing STS were collected from 10 young, 10 elderly and 10 elderly subjects with difficulty in STS. Young subjects were also asked to stand up with their trunk purposely bent forward. The regions of stability were defined with COM position at seat-off and its instantaneous velocity (ROSv) or peak Acceleration (ROSa), using a single-link-plus-foot inverted pendulum model. Peak COM Accelerations prior to seat-off differed significantly among groups; however, no significant differences were detected in its velocities at seat-off. The ROSa demonstrated a better ability to discriminate elderly adults with difficulty from healthy individuals. Although a similar COM momentum was observed at seat-off, how the momentum was controlled differed between healthy individuals and individuals with difficulty in STS. ROSa could provide insight into how the COM momentum is controlled prior to seat-off, which could be used to differentiate individuals with functional limitations from healthy individuals.
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Dynamic balance control during sit-to-stand movement: An examination with the center of Mass Acceleration
Journal of biomechanics, 2011Co-Authors: M. Fujimoto, L. S. ChouAbstract:The purpose of this study was to establish the region of stability of balance control using the center of Mass (COM) Acceleration and to characterize age-related differences during sit-to-stand (STS) movement. Whole body motion data were collected from 10 young and 10 elderly subjects while performing STS at their self-selected manners. In addition, young subjects were asked to perform another block of trials with their trunk purposely bent forward prior to seat-off. With the use of a single-link-plus-foot inverted pendulum model, boundaries for the region of stability were determined based on the COM position at seat-off and its instantaneous velocity or its peak Acceleration (ROSv or ROSa, respectively). No significant group differences were detected in COM velocities at seat-off. However, peak COM Accelerations differed significantly between groups and conditions. This suggested that even though a similar COM momentum was observed at seat-off, this momentum was controlled differently prior to seat-off. Young and elderly subjects utilized similar strategies but with different COM Acceleration profiles to perform STS. Furthermore, data from an elderly subject who complained of difficulty in STS during the experiment were located outside the forward boundary of the ROSa, demonstrating a potential use of ROSa to differentiate individuals with declined balance control ability. The ROSa could provide insights into how the COM is controlled prior to seat-off, which may allow us to better identify elderly individuals who are most likely at a risk for imbalance or falls.
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Limits of Dynamic Balance Control Derived by Center of Mass Acceleration during Sit-to-Stand Movement
IFMBE Proceedings, 2010Co-Authors: M. Fujimoto, L. S. ChouAbstract:The purpose of this study was to establish a region of stability using the center of Mass (COM) Acceleration and characterize age-related differences in the control of COM in relation to the region during sit-to-stand (STS) movement. A single-link-plus-foot inverted pendulum model was used to determine boundaries of the regions of stability using COM velocity and Acceleration (ROSv and ROSa). Ten healthy young and elderly adults [Young (Norm) and Elderly] were asked to stand up from a chair at self-selected natural speed. Young subjects were also asked to perform another block of trials with purposely bending their trunk prior to seat-off [Young (Bend)]. No significant differences among the three groups were detected in COM velocity at seat-off. However, peak COM Acceleration differed significantly, suggesting that even though a similar momentum is observed at seat-off to achieve the STS task, the momentum is controlled differently prior to seat-off. The ROSa could serve as a complement to the ROSv, providing insights into how the COM is controlled prior to seat-off during STS movement.
Raviraj Nataraj - One of the best experts on this subject based on the ideXlab platform.
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center of Mass Acceleration feedback control of standing balance by functional neuromuscular stimulation against external postural perturbations
IEEE Transactions on Biomedical Engineering, 2013Co-Authors: Raviraj Nataraj, Musa L. Audu, Ronald J. TrioloAbstract:This study investigated the use of center of Mass (COM) Acceleration feedback for improving performance of a functional neuromuscular stimulation control system to restore standing function to a subject with complete, thoracic-level spinal cord injury. The approach for linearly relating changes in muscle stimulation to changes in COM Acceleration was verified experimentally and subsequently produced data to create an input-output map driven by sensor feedback. The feedback gains were systematically tuned to reduce upper extremity (UE) loads applied to an instrumented support device while resisting external postural disturbances. Total body COM Acceleration was accurately estimated (>;89% variance explained) using 3-D outputs of two accelerometers mounted on the pelvis and torso. Compared to constant muscle stimulation employed clinically, feedback control of stimulation reduced UE loading by 33%. COM Acceleration feedback is advantageous in constructing a standing neuroprosthesis since it provides the basis for a comprehensive control synergy about a global, dynamic variable and requires minimal instrumentation. Future work should include tuning and testing the feedback control system during functional reaching activity that is more indicative of activities of daily living.
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Comparing joint kinematics and center of Mass Acceleration as feedback for control of standing balance by functional neuromuscular stimulation.
Journal of neuroengineering and rehabilitation, 2012Co-Authors: Raviraj Nataraj, Musa L. Audu, Ronald J. TrioloAbstract:The purpose of this study was to determine the comparative effectiveness of feedback control systems for maintaining standing balance based on joint kinematics or total body center of Mass (COM) Acceleration, and assess their clinical practicality for standing neuroprostheses after spinal cord injury (SCI). In simulation, controller performance was measured according to the upper extremity effort required to stabilize a three-dimensional model of bipedal standing against a variety of postural disturbances. Three cases were investigated: proportional-derivative control based on joint kinematics alone, COM Acceleration feedback alone, and combined joint kinematics and COM Acceleration feedback. Additionally, pilot data was collected during external perturbations of an individual with SCI standing with functional neuromuscular stimulation (FNS), and the resulting joint kinematics and COM Acceleration data was analyzed. Compared to the baseline case of maximal constant muscle excitations, the three control systems reduced the mean upper extremity loading by 51%, 43% and 56%, respectively against external force-pulse perturbations. Controller robustness was defined as the degradation in performance with increasing levels of input errors expected with clinical deployment of sensor-based feedback. At error levels typical for body-mounted inertial sensors, performance degradation due to sensor noise and placement were negligible. However, at typical tracking error levels, performance could degrade as much as 86% for joint kinematics feedback and 35% for COM Acceleration feedback. Pilot data indicated that COM Acceleration could be estimated with a few well-placed sensors and efficiently captures information related to movement synergies observed during perturbed bipedal standing following SCI. Overall, COM Acceleration feedback may be a more feasible solution for control of standing with FNS given its superior robustness and small number of inputs required.
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Center of Mass Acceleration feedback control for standing by functional neuromuscular stimulation: a simulation study.
Journal of rehabilitation research and development, 2012Co-Authors: Raviraj Nataraj, Musa L. Audu, Robert F. Kirsch, Ronald J. TrioloAbstract:The potential efficacy of total body center of Mass (COM) Acceleration for feedback control of standing balance by functional neuromuscular stimulation (FNS) following spinal cord injury (SCI) was investigated. COM Acceleration may be a viable alternative to conventional joint kinematics due to its rapid responsiveness, focal representation of COM dynamics, and ease of measurement. A computational procedure was developed using an anatomically-realistic, three-dimensional, bipedal biomechanical model to determine optimal patterns of muscle excitations to produce targeted effects upon COM Acceleration from erect stance. The procedure was verified with electromyographic data collected from standing able-bodied subjects undergoing systematic perturbations. Using 16 muscle groups targeted by existing implantable neuroprostheses, data were generated to train an artificial neural network (ANN)-based controller in simulation. During forward simulations, proportional feedback of COM Acceleration drove the ANN to produce muscle excitation patterns countering the effects of applied perturbations. Feedback gains were optimized to minimize upper extremity (UE) loading required to stabilize against disturbances. Compared to the clinical case of maximum constant excitation, the controller reduced UE loading by 43% in resisting external perturbations and by 51% during simulated one-arm reaching. Future work includes performance assessment against expected measurement errors and developing user-specific control systems.
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Center of Mass Acceleration feedback control of functional neuromuscular stimulation for standing in presence of internal postural perturbations
Journal of rehabilitation research and development, 2012Co-Authors: Raviraj Nataraj, Musa L. Audu, Ronald J. TrioloAbstract:This study determined the feasibility and performance of center of Mass (COM) Acceleration feedback control of a neuroprosthesis utilizing functional neuromuscular stimulation (FNS) to restore standing balance to a single subject paralyzed by a motor and sensory complete, thoracic-level spinal cord injury (SCI). An artificial neural network (ANN) was created to map gain-modulated changes in total body COM Acceleration estimated from body-mounted sensors to optimal changes in stimulation required to maintain standing. Feedback gains were systematically tuned to minimize the upper extremity (UE) loads applied by the subject to an instrumented support device during internally generated postural perturbations produced by volitional reaching and object manipulation. Total body COM Acceleration was accurately estimated (> 90% variance explained) from two three-dimensional (3-D) accelerometers mounted on the pelvis and torso. Compared to constant muscle stimulation employed clinically, COM Acceleration feedback control of stimulation improved standing performance by reducing the UE loading required to resist internal postural disturbances by 27%. This case study suggests that COM Acceleration feedback could potentially be advantageous in a standing neuroprosthesis since it can be implemented with only a few feedback parameters and requires minimal instrumentation for comprehensive, 3-D control of dynamic standing function.
A. T. Papagiannakis - One of the best experts on this subject based on the ideXlab platform.
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International Standards organization-compatible Index for pavement roughness
Transportation Research Record, 1998Co-Authors: A. T. Papagiannakis, Balu RaveendranAbstract:The development of a new pavement roughness index, which is compatible to the current International Standards Organization (ISO) standard on "exposure to whole-body vibration" is described. The index was intended to be the independent variable in the future development of relationships between user cost (i.e., vehicle depreciation, repairs, discomfort and so on) and pavement roughness; hence it was named RIDE (Roughness Index for Driving Expenditure). RIDE is based on the sprung Mass Acceleration response of a reference vehicle to the pavement profile. It is calculated in the frequency domain by multiplying the power spectral density (PSD) of the pavement profile by the square of the transfer function of the sprung Mass Acceleration of the reference vehicle. The resulting sprung Mass Acceleration PSD is integrated over frequency to yield the root-mean-square of the sprung Mass Acceleration per unit length of pavement traveled. The sprung Mass Acceleration is shown to be the main contributor of dynamic axl...
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International Standards Organization-Compatible Index for Pavement Roughness
Transportation Research Record: Journal of the Transportation Research Board, 1998Co-Authors: A. T. Papagiannakis, Balu RaveendranAbstract:The development of a new pavement roughness index, which is compatible to the current International Standards Organization (ISO) standard on “exposure to whole-body vibration” is described. The index was intended to be the independent variable in the future development of relationships between user cost (i.e., vehicle depreciation, repairs, discomfort and so on) and pavement roughness; hence it was named RIDE (Roughness Index for Driving Expenditure). RIDE is based on the sprung Mass Acceleration response of a reference vehicle to the pavement profile. It is calculated in the frequency domain by multiplying the power spectral density (PSD) of the pavement profile by the square of the transfer function of the sprung Mass Acceleration of the reference vehicle. The resulting sprung Mass Acceleration PSD is integrated over frequency to yield the root-mean-square of the sprung Mass Acceleration per unit length of pavement traveled. The sprung Mass Acceleration is shown to be the main contributor of dynamic axle loads in heavy trucks, which relate to vehicle and cargo damage and also to pavement damage.
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Roughness model describing heavy vehicle-pavement interaction
Transportation Research Record, 1995Co-Authors: A. T. Papagiannakis, Manoj Sharad GujarathiAbstract:The pavement roughness characteristics that affect interaction between pavement and heavy vehicles are addressed. A roughness model describing the pavement roughness attributes affecting heavy vehicles is presented. Dynamic vehicle response data from two sources were analyzed, namely, experimental data obtained with the instrumented vehicle developed by the National Research Council of Canada and simulated data obtained with a quarter-vehicle simulation. It was found that the vehicle response parameter of interest in this interaction is the sprung Mass vehicle Acceleration because it relates to both pavement and vehicle damage as well as to ride quality and cargo damage. This was demonstrated by analyzing the transfer functions of both the dynamic axle load and the vertical sprung Mass Acceleration over a range of pavement roughnesses and vehicle speeds. The sprung Mass vertical Acceleration transfer function showed sensitivity to a pavement roughness excitation frequency of 3.5 Hz. A pavement roughness statistic was proposed that is calculated as follows : (a) calculate the spectral density of the pavement roughness profile, (b) multiply this spectral density by the square of a transfer function to obtain the spectral density of the vertical sprung Mass Acceleration of the reference quarter vehicle selected, and (c) calculate the integral of the spectral density of the vertical sprung Mass Acceleration over the full frequency spectrum and take the square root. The resulting statistic has units of energy per unit Mass per unit length of pavement traveled and represents the energy input from the road to the vehicle and vice versa.
Balu Raveendran - One of the best experts on this subject based on the ideXlab platform.
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International Standards organization-compatible Index for pavement roughness
Transportation Research Record, 1998Co-Authors: A. T. Papagiannakis, Balu RaveendranAbstract:The development of a new pavement roughness index, which is compatible to the current International Standards Organization (ISO) standard on "exposure to whole-body vibration" is described. The index was intended to be the independent variable in the future development of relationships between user cost (i.e., vehicle depreciation, repairs, discomfort and so on) and pavement roughness; hence it was named RIDE (Roughness Index for Driving Expenditure). RIDE is based on the sprung Mass Acceleration response of a reference vehicle to the pavement profile. It is calculated in the frequency domain by multiplying the power spectral density (PSD) of the pavement profile by the square of the transfer function of the sprung Mass Acceleration of the reference vehicle. The resulting sprung Mass Acceleration PSD is integrated over frequency to yield the root-mean-square of the sprung Mass Acceleration per unit length of pavement traveled. The sprung Mass Acceleration is shown to be the main contributor of dynamic axl...
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International Standards Organization-Compatible Index for Pavement Roughness
Transportation Research Record: Journal of the Transportation Research Board, 1998Co-Authors: A. T. Papagiannakis, Balu RaveendranAbstract:The development of a new pavement roughness index, which is compatible to the current International Standards Organization (ISO) standard on “exposure to whole-body vibration” is described. The index was intended to be the independent variable in the future development of relationships between user cost (i.e., vehicle depreciation, repairs, discomfort and so on) and pavement roughness; hence it was named RIDE (Roughness Index for Driving Expenditure). RIDE is based on the sprung Mass Acceleration response of a reference vehicle to the pavement profile. It is calculated in the frequency domain by multiplying the power spectral density (PSD) of the pavement profile by the square of the transfer function of the sprung Mass Acceleration of the reference vehicle. The resulting sprung Mass Acceleration PSD is integrated over frequency to yield the root-mean-square of the sprung Mass Acceleration per unit length of pavement traveled. The sprung Mass Acceleration is shown to be the main contributor of dynamic axle loads in heavy trucks, which relate to vehicle and cargo damage and also to pavement damage.