A closed-loop self-righting controller for seated balance in the coronal and diagonal planes following spinal cord injury

Bheemreddy, Akhil; Lombardo, Lisa M.; Miller, Michael E.; Foglyano, Kevin M.; Bailey, Stephen; Triolo, Ronald J.; Audu, Musa L.

doi:10.1016/j.medengphy.2020.10.010

Cited by 4 publications

(7 citation statements)

References 27 publications

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“…Returning the subject to an upright stable posture faster after a reach will reduce the length of time in an unstable posture. In instances with possible falls it is also crucial to restore upright sitting as fast as possible [ 21 , 42 ]. The return to upright movements are likely a combination of eccentric and concentric contractions.…”

Section: Discussionmentioning

confidence: 99%

“…Prior experiments have demonstrated the ability of a threshold-based controller to return a person to an upright position after a large trunk disturbance [ 20 , 21 ]. These benefits continued to be evident during smaller internal disturbances caused by an upright reaching task in the current study.…”

Section: Discussionmentioning

confidence: 99%

“…As the subject leaned away from the erect position the gravity vector projection on the local accelerometer coordinate frame changed such that variation in the x-axis value corresponded to lateral bending of the trunk, while changes in the z-axis (Fig. 1) corresponded to trunk flexion/extension [20,21,25]. Baseline x and z values were set at the beginning of each trial while the subject assumed an upright seated posture.…”

Section: Feedback Control Systemmentioning

confidence: 99%

“…Various forms of feedback controllers have been proposed to maintain seated balance in the sagittal plane by adjusting stimulation parameters to resist external perturbations applied to the trunk [ 18 , 19 ]. Murphy et al [ 20 ] and Bheemreddy et al [ 21 ] implemented a threshold-based self-righting controller to recruit trunk muscles with supramaximal stimulation once the subject exceeded a predetermined trunk flexion or bending threshold to effectively return the user to an erect posture from large forward flexed or sideways bending postures. Proportional, integral, derivative (PID) control was found to be particularly appropriate for upright sitting since the extrinsic (active muscles) properties of the trunk are dominated by the proportional and derivative model components [ 22 ].…”

Section: Introductionmentioning

confidence: 99%

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Feedback control of upright seating with functional neuromuscular stimulation during a reaching task after spinal cord injury: a feasibility study

Friederich

Bao

Triolo

et al. 2022

J NeuroEngineering Rehabil

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Background Restoring or improving seated stability after spinal cord injury (SCI) can improve the ability to perform activities of daily living by providing a dynamic, yet stable, base for upper extremity motion. Seated stability can be obtained with activation of the otherwise paralyzed trunk and hip musculature with neural stimulation, which has been shown to extend upper limb reach and improve seated posture. Methods We implemented a proportional, integral, derivative (PID) controller to maintain upright seated posture by simultaneously modulating both forward flexion and lateral bending with functional neuromuscular stimulation. The controller was tested with a functional reaching task meant to require trunk movements and impart internal perturbations through rapid changes in inertia due to acquiring, moving, and replacing objects with one upper extremity. Five subjects with SCI at various injury levels who had received implanted stimulators targeting their trunk and hip muscles participated in the study. Each subject was asked to move a weighted jar radially from a center home station to one of three target stations. The task was performed with the controller active, inactive, or with a constant low level of neural stimulation. Trunk pitch (flexion) and roll (lateral bending) angles were measured with motion capture and plotted against each other to generate elliptical movement profiles for each task and condition. Postural sway was quantified by calculating the ellipse area. Additionally, the mean effective reach (distance between the shoulder and wrist) and the time required to return to an upright posture was determined during reaching movements. Results Postural sway was reduced by the controller in two of the subjects, and mean effective reach was increased in three subjects and decreased for one. Analysis of the major direction of motion showed return to upright movements were quickened by 0.17 to 0.32 s. A 15 to 25% improvement over low/no stimulation was observed for four subjects. Conclusion These results suggest that feedback control of neural stimulation is a viable way to maintain upright seated posture by facilitating trunk movements necessary to complete reaching tasks in individuals with SCI. Replication of these findings on a larger number of subjects would be necessary for generalization to the various segments of the SCI population.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Feedback Control Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Feedback control of upright seating with functional neuromuscular stimulation during a reaching task after spinal cord injury: a feasibility study

Friederich

Bao

Triolo

et al. 2022

J NeuroEngineering Rehabil

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“…However, these sensor fusion methods are subject to random drift from the integration of the gyroscopic data [ 22 ] and ferromagnetic disturbances to the magnetometer readings [ 23 ]. Previous integration of IMUs in feedback control of trunk posture has been achieved with an externally-mounted 3-axis accelerometer placed on the chest or the back [ 18 , 19 , 24 ] to reflect tilt based on the consistent gravity vector compared to the inclined accelerometer coordinate frame. To obtain relevant measures of trunk orientation, the sensor was carefully aligned with the anatomical axes of the body.…”

Section: Introductionmentioning

confidence: 99%

Trunk Posture from Randomly Oriented Accelerometers

Friederich

Audu

Triolo

2022

Sensors

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Feedback control of functional neuromuscular stimulation has the potential to improve daily function for individuals with spinal cord injuries (SCIs) by enhancing seated stability. Our fully implanted networked neuroprosthesis (NNP) can provide real-time feedback signals for controlling the trunk through accelerometers embedded in modules distributed throughout the trunk. Typically, inertial sensors are aligned with the relevant body segment. However, NNP implanted modules are placed according to surgical constraints and their precise locations and orientations are generally unknown. We have developed a method for calibrating multiple randomly oriented accelerometers and fusing their signals into a measure of trunk orientation. Six accelerometers were externally attached in random orientations to the trunks of six individuals with SCI. Calibration with an optical motion capture system resulted in RMSE below 5° and correlation coefficients above 0.97. Calibration with a handheld goniometer resulted in RMSE of 7° and correlation coefficients above 0.93. Our method can obtain trunk orientation from a network of sensors without a priori knowledge of their relationships to the body anatomical axes. The results of this study will be invaluable in the design of feedback control systems for stabilizing the trunk of individuals with SCI in combination with the NNP implanted technology.

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Nonlinear neural control using feedback linearization explains task goals of central nervous system for trunk stability in sitting posture

Vette

Noamani

2023

J. Neural Eng.

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Objective: Characterizing the task goals of the neural control system for achieving seated stability has been a fundamental challenge in human motor control research. This study aimed to experimentally identify the task goals of the neural control system for seated stability.Approach: Ten able-bodied young individuals participated in our experiments, which allowed us to measure their body motion and muscle activity during perturbed sitting. We used a nonlinear neuromechanical model of the seated human, along with a full-state feedback linearization approach and optimal control theory for identifying the neural control system and characterizing its task goals.Main results: We demonstrated that the neural feedback for trunk stability during seated posture uses angular position, velocity, acceleration, and jerk in a linearized space. The mean squared error between the predicted and measured motor commands was less than 0.6% among all trials and participants, with a median correlation coefficient (r) of more than 0.9. Our identified optimal neural control primarily used trunk angular acceleration and near-minimum muscle activation to achieve seated stability while keeping the deviations of the trunk angular position and acceleration sufficiently small. Significance: Our proposed approach to neural control system identification relied on a performance criterion (e.g., cost function) explaining what the functional goal is and subsequently, finds the control law that leads to the best performance. Therefore, instead of assuming what control schemes the neural control might utilize (e.g., proportional-integral-derivative control), optimal control allows the motor task and the neuromechanical model to dictate a control law that best describes the physiological process. This approach allows for a mechanistic understanding of the neuromuscular mechanisms involved in seated stability and for inferring the task goals used by the neural control system to achieve the targeted motor behaviour. Such neural control characterization can contribute to the development of objective balance evaluation tools and of bio-inspired assistive neuromodulation technologies.

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A closed-loop self-righting controller for seated balance in the coronal and diagonal planes following spinal cord injury

Cited by 4 publications

References 27 publications

Feedback control of upright seating with functional neuromuscular stimulation during a reaching task after spinal cord injury: a feasibility study

Feedback control of upright seating with functional neuromuscular stimulation during a reaching task after spinal cord injury: a feasibility study

Trunk Posture from Randomly Oriented Accelerometers

Nonlinear neural control using feedback linearization explains task goals of central nervous system for trunk stability in sitting posture

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