Knee Exoskeleton Reduces Muscle Effort and Improves Balance During Sit-to-Stand Transitions After Stroke: A Case Study

Sarkisian, Sergei V.; Gunnell, Andrew; Foreman, K. Bo; Lenzi, Tommaso

doi:10.1109/icorr55369.2022.9896571

Cited by 2 publications

(2 citation statements)

References 23 publications

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“…The exoskeleton aids the user based on the algorithm shown in Figure 5 . The high-level controller uses the activation of the Vastus Medialis on the exoskeleton side to define the desired extension knee torque during stair ascents ( Figure 5 ; Sarkisian et al, 2022 ). We chose Vastus Medialis for high-level control because it is a monoarticular knee extensor, unlike Rectus Femoris, which is a biarticular muscle spanning both the knee and hip joints.…”

Section: Human Experimentsmentioning

confidence: 99%

“…To test the performance of the proposed SEA, we modified the Utah ExoKnee (Figure 1b), a powered knee exoskeleton previously used for physical human-robot interaction studies (Sarkisian et al, 2020(Sarkisian et al, , 2021 and stroke assistance (Sarkisian et al, 2022). The frame of the exoskeleton remained largely unchanged, aside from some machined parts to accommodate the specific dimensions of the proposed SEA.…”

Section: Designmentioning

confidence: 99%

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Series-elastic actuator with two degree-of-freedom PID control improves torque control in a powered knee exoskeleton

Sarkisian,

Gabert,

Lenzi

2023

Wearable Technol.

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Powered exoskeletons need actuators that are lightweight, compact, and efficient while allowing for accurate torque control. To satisfy these requirements, researchers have proposed using series elastic actuators (SEAs). SEAs use a spring in series with rotary or linear actuators. The spring compliance, in conjunction with an appropriate control scheme, improves torque control, efficiency, output impedance, and disturbance rejection. However, springs add weight to the actuator and complexity to the control, which may have negative effects on the performance of the powered exoskeleton. Therefore, there is an unmet need for new SEA designs that are lighter and more efficient than available systems, as well as for control strategies that push the performance of SEA-based exoskeletons without requiring complex modeling and tuning. This article presents the design, development, and testing of a novel SEA with high force density for powered exoskeletons, as well as the use of a two degree-of-freedom (2DOF) PID system to improve output impedance and disturbance rejection. Benchtop testing results show reduced output impedance and damping values when using a 2DOF PID controller as compared to a 1DOF PID controller. Human experiments with three able-bodied subjects (N = 3) show improved torque tracking with reduced root-mean-square error by 45.2% and reduced peak error by 49.8% when using a 2DOF PID controller. Furthermore, EMG data shows a reduction in peak EMG value when using the exoskeleton in assistive mode compared to the exoskeleton operating in transparent mode.

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Section: Human Experimentsmentioning

confidence: 99%

Section: Designmentioning

confidence: 99%

Series-elastic actuator with two degree-of-freedom PID control improves torque control in a powered knee exoskeleton

Sarkisian,

Gabert,

Lenzi

2023

Wearable Technol.

Self Cite

View full text Add to dashboard Cite

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Prediction of ground reaction forces and moments and joint kinematics and kinetics by inertial measurement units using 3D forward dynamics model

HARAGUCHI,

HASE

2024

JBSE

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Predicting the ground reaction force (GRF) and ground reaction moment (GRM) with a biomechanical modelbased approach has an advantage for biomechanical gait analysis in situations where a statistical model cannot be used due to a lack of training data. However, the current prediction methods using a biomechanical model have some issues for clinical application. The present study developed a new inertial measurement unit (IMU)based method to predict the GRF, the GRM, and the joint kinematics and kinetics with a 3D biomechanical model and simple system. The present method predicts them using a 3D forward dynamics model that computationally generates human movements that minimize the hybrid cost function defined by physical loads and errors between the motion of the model and that of the participants recorded by six IMUs, which allows the prediction system to use only a relatively small number of IMUs. We investigated the prediction accuracy during walking by comparing the new method with a conventional analysis using a force plate and motion capture system. As a result, we observed strong and excellent correlations between the prediction and measurement of the anterior GRF, vertical GRF, sagittal GRM, hip flexion angle, knee flexion angle, hip flexion torque, and ankle dorsiflexion torque. Considering the accuracy of previous studies and that required for gait analysis, the present method could predict them with practical accuracy due to estimated biomechanically valid motions based on optimization using the hybrid cost function that includes a biomechanical evaluation. Moreover, the prediction system has an advantage for clinical applications because the present method observed practical accuracy that has the potential to be applied to some sports analysis and can analyze 3D motion with a simple system consisting of a small number of hardware components and a software.

show abstract

Knee Exoskeleton Reduces Muscle Effort and Improves Balance During Sit-to-Stand Transitions After Stroke: A Case Study

Cited by 2 publications

References 23 publications

Series-elastic actuator with two degree-of-freedom PID control improves torque control in a powered knee exoskeleton

Series-elastic actuator with two degree-of-freedom PID control improves torque control in a powered knee exoskeleton

Prediction of ground reaction forces and moments and joint kinematics and kinetics by inertial measurement units using 3D forward dynamics model

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