Design of a Variable Constraint Hip Mechanism for a Hybrid Neuroprosthesis to Restore Gait After Spinal Cord Injury

To, Curtis S.; Kobetic, Rudi; Schnellenberger, John R.; Audu, Musa L.; Triolo, Ronald J.

doi:10.1109/tmech.2008.918551

Cited by 43 publications

(35 citation statements)

References 21 publications

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“…The exoskeleton weighing 22.2 kg was a modified IRGO where the reciprocating bar was replaced with the VCHM and the drop-lock knee joints were replaced with a pair of prototype hydraulic stance-control knee mechanisms (SCKMs) [19][20]. The SCKM was necessary to lock the knee in extension against collapse during stance while allowing for free motion during FNS-driven swing (Figure 1).…”

Section: Test Casesmentioning

confidence: 99%

“…The VCHM was designed as a closed hydraulic system to couple, free, or lock the hips [19]. The mechanism provides stance hip support by constraining the hip against flexion while allowing it to extend by means of hip extensor stimulation during contralateral swing.…”

Section: Rule-based Feedback Control Of Variable-constraint Hip Mechamentioning

confidence: 99%

“…Thus, this control scheme allowed free hip flexion during swing for increasing the step length, provided that stimulation of hip flexors could drive the contralateral limb into extension. The controller parameters were defined through preliminary bench [19][20] and nondisabled testing.…”

Section: Rule-based Feedback Control Of Variable-constraint Hip Mechamentioning

confidence: 99%

“…The hip is fully extended once the hip angle crosses below a first threshold (8°, hip extension is negative) and is considered fully extended as long as it remains greater than a second hip angle threshold (0°). The difference between the first and second hip angle thresholds is the acceptable compliance of the VCHM while it is constraining the hip against flexion, which was determined in bench testing to be approximately 8° at a locking torque of 35 Nm [20]. Rule 3 took precedence over rule 2.…”

Section: Rulementioning

confidence: 99%

“…However, the postural support provided by RGOs are intermittent and only beneficial during the double support phases of gait and actually hinder lower-limb kinematics during the rest of the gait cycle [5]. Thus, a hydraulic variable-constraint hip mechanism (VCHM) was developed [19] to actively modulate the reciprocal coupling of the hips (Figure 1). The VCHM was designed to reciprocally couple the hips or independently free or lock a hip against motion through sensor signal feedback control.…”

Section: Introductionmentioning

confidence: 99%

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Sensor-based hip control with hybrid neuroprosthesis for walking in paraplegia

Kobetic

Bulea

et al. 2014

J Rehabil Res Dev

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Abstract-The objectives of this study were to test whether a hybrid neuroprosthesis (HNP) with an exoskeletal variableconstraint hip mechanism (VCHM) combined with a functional neuromuscular stimulation (FNS) controller can maintain upright posture with less upper-limb support and improve gait speed as compared with walking with either an isocentric reciprocating gait orthosis (IRGO) or FNS only. The results show that walking with the HNP significantly reduced forward lean in FNS-only walking and the maximum upper-limb forces by 42% and 19% as compared with the IRGO and FNS-only gait, respectively. Walking speed increased significantly with VCHM as compared with 1:1 reciprocal coupling and by 15% when using the sensor-based FNS controller as compared with HNP with fixed baseline stimulation without the controller active.

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Section: Test Casesmentioning

confidence: 99%

Section: Rule-based Feedback Control Of Variable-constraint Hip Mechamentioning

confidence: 99%

Section: Rule-based Feedback Control Of Variable-constraint Hip Mechamentioning

confidence: 99%

Section: Rulementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Sensor-based hip control with hybrid neuroprosthesis for walking in paraplegia

Kobetic

Bulea

et al. 2014

J Rehabil Res Dev

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An adaptive robust observer for velocity estimation in an electro‐hydraulic system

Mohanty

Gayaka

Yao

2012

Adaptive Control & Signal

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This paper proposes the design of an observer to estimate the velocity of an electro-hydraulic system by using pressure measurements only. The difficulties involved in the design of an observer for such a system include the highly nonlinear system dynamics, severe parametric uncertainties such as large variation of inertial load and unmatched model uncertainties. In order to address these issues, a nonlinear model-based adaptive robust observer is designed to estimate the velocity. The contributions of the proposed work is twofold. First, it introduces a novel coordinate transformation to reconstruct the velocity estimate. And second, from a structural viewpoint, the design has two important features: (i) an underlying robust filter structure, which can attenuate the effect of uncertain nonlinearities such as friction and disturbances on the velocity estimation, and (ii) an adaptation mechanism to reduce the extent of parametric uncertainties. Experimental results on the swing motion control of an electro-hydraulic robot arm demonstrate the effectiveness of the proposed observer.AN ADAPTIVE ROBUST OBSERVER FOR VELOCITY ESTIMATION IN AN EH SYSTEM 1077 common because of the cheaper cost of installing pressure sensors. Position and velocity feedback sensors, however, are not typically used in such systems because of the prohibitive costs and the high likelihood of failure in harsh environments. Hence, design of observers, which estimate the velocity from available measurements, for example, the cylinder pressures, is essential for the implementation of the feedback control law [6].The theoretical challenges in designing a velocity observer for EHS arises from the inherent nonlinear nature of the system, for example, deadband and hysteresis present in the control valves, nonlinear pressure/flow relations, and variation in the fluid volumes due to the movement of the actuator. Apart from the nonlinearities, hydraulic systems have large extents of modeling uncertainties. The uncertainties can be classified into (i) parametric uncertainties and (ii) uncertain nonlinearities. Examples of parametric uncertainties include the large changes in load experienced by the system and the variations in hydraulic parameters due to change in temperature, pressure, and component wear [7,8]. Another class of uncertainties such as external disturbances, leakage, and friction cannot be modeled exactly, and the nonlinear functions that describe them are not known. These uncertainties are termed as uncertain nonlinearities [9,10]. Addressing both the issues simultaneously makes the observer design a fairly challenging problem.In the past, observer design was largely performed by linearizing the system and applying Luenberger observer design techniques to the linearized plant. Unfortunately, as discussed in the previous section, the hydraulic system is inherently nonlinear, and many of the nonlinearities are non-smooth and discontinuous like control input saturation, directional change of valve opening, friction, and valve deadband. Hence,...

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