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Physical human-robot interaction of an active pelvis orthosis: toward ergonomic assessment of wearable robots

View Article: PubMed Central - PubMed

ABSTRACT

Background: In human-centered robotics, exoskeletons are becoming relevant for addressing needs in the healthcare and industrial domains. Owing to their close interaction with the user, the safety and ergonomics of these systems are critical design features that require systematic evaluation methodologies. Proper transfer of mechanical power requires optimal tuning of the kinematic coupling between the robotic and anatomical joint rotation axes. We present the methods and results of an experimental evaluation of the physical interaction with an active pelvis orthosis (APO). This device was designed to effectively assist in hip flexion-extension during locomotion with a minimum impact on the physiological human kinematics, owing to a set of passive degrees of freedom for self-alignment of the human and robotic hip flexion-extension axes.

Methods: Five healthy volunteers walked on a treadmill at different speeds without and with the APO under different levels of assistance. The user-APO physical interaction was evaluated in terms of: (i) the deviation of human lower-limb joint kinematics when wearing the APO with respect to the physiological behavior (i.e., without the APO); (ii) relative displacements between the APO orthotic shells and the corresponding body segments; and (iii) the discrepancy between the kinematics of the APO and the wearer’s hip joints.

Results: The results show: (i) negligible interference of the APO in human kinematics under all the experimented conditions; (ii) small (i.e., < 1 cm) relative displacements between the APO cuffs and the corresponding body segments (called stability); and (iii) significant increment in the human-robot kinematics discrepancy at the hip flexion-extension joint associated with speed and assistance level increase.

Conclusions: APO mechanics and actuation have negligible interference in human locomotion. Human kinematics was not affected by the APO under all tested conditions. In addition, under all tested conditions, there was no relevant relative displacement between the orthotic cuffs and the corresponding anatomical segments. Hence, the physical human-robot coupling is reliable. These facts prove that the adopted mechanical design of passive degrees of freedom allows an effective human-robot kinematic coupling. We believe that this analysis may be useful for the definition of evaluation metrics for the ergonomics assessment of wearable robots.

No MeSH data available.


Related in: MedlinePlus

Average intra-subject variability of hip (left), knee (center), ankle (right) flexion-extension angle for all speeds (slow (V1), self-selected (V2), fast (V3)) and walking conditions (natural walking –no APO- (NW), transparent mode -APO shadows the wearer- (TM), low assistance (AM1), moderate assistance (AM2), high assistance (AM3)). Black columns represent one SD band
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Fig6: Average intra-subject variability of hip (left), knee (center), ankle (right) flexion-extension angle for all speeds (slow (V1), self-selected (V2), fast (V3)) and walking conditions (natural walking –no APO- (NW), transparent mode -APO shadows the wearer- (TM), low assistance (AM1), moderate assistance (AM2), high assistance (AM3)). Black columns represent one SD band

Mentions: Despite the hip and knee ROM increase with assistance, the overall f/e angle trajectories in all walking conditions are highly overlapped, showing consistency between the kinematics in NW and in other walking conditions. In fact, when considering H-HAD, H-KAD, and H-AAD (see Fig. 5 and Table 3), which account for the global difference between the kinematics in NW and in other conditions, we obtain values comparable with the average intra-subject variability of the hip, knee, and ankle f/e angles (see Fig. 6 and Table 4). H-HAD ranges from 1.8 ± 0.8° in V1-TM to 3.9 ± 1.1° in V2-AM3, while the average intra-subject variability of the hip f/e angle ranges from 1.5 ± 0.5° in V3-NW to 2.4 ± 1.0° in V3-AM3. H-KAD ranges from 2.6 ± 1.5° in V2-TM to 5.7 ± 1.5° in V1-AM2, while the average intra-subject variability of the knee f/e angle ranges from 1.6 ± 0.2° in V3-NW to 3.4 ± 0.6 in V1-AM2. H-AAD ranges from 1.7 ± 0.8° in V2-TM to 3.8 ± 3.0° in V1-AM2, while the average intra-subject variability of the ankle f/e angle ranges from 1.4 ± 0.2° in V3-NW to 2.2 ± 0.2 in V1-AM2.Fig. 5


Physical human-robot interaction of an active pelvis orthosis: toward ergonomic assessment of wearable robots
Average intra-subject variability of hip (left), knee (center), ankle (right) flexion-extension angle for all speeds (slow (V1), self-selected (V2), fast (V3)) and walking conditions (natural walking –no APO- (NW), transparent mode -APO shadows the wearer- (TM), low assistance (AM1), moderate assistance (AM2), high assistance (AM3)). Black columns represent one SD band
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5391543&req=5

Fig6: Average intra-subject variability of hip (left), knee (center), ankle (right) flexion-extension angle for all speeds (slow (V1), self-selected (V2), fast (V3)) and walking conditions (natural walking –no APO- (NW), transparent mode -APO shadows the wearer- (TM), low assistance (AM1), moderate assistance (AM2), high assistance (AM3)). Black columns represent one SD band
Mentions: Despite the hip and knee ROM increase with assistance, the overall f/e angle trajectories in all walking conditions are highly overlapped, showing consistency between the kinematics in NW and in other walking conditions. In fact, when considering H-HAD, H-KAD, and H-AAD (see Fig. 5 and Table 3), which account for the global difference between the kinematics in NW and in other conditions, we obtain values comparable with the average intra-subject variability of the hip, knee, and ankle f/e angles (see Fig. 6 and Table 4). H-HAD ranges from 1.8 ± 0.8° in V1-TM to 3.9 ± 1.1° in V2-AM3, while the average intra-subject variability of the hip f/e angle ranges from 1.5 ± 0.5° in V3-NW to 2.4 ± 1.0° in V3-AM3. H-KAD ranges from 2.6 ± 1.5° in V2-TM to 5.7 ± 1.5° in V1-AM2, while the average intra-subject variability of the knee f/e angle ranges from 1.6 ± 0.2° in V3-NW to 3.4 ± 0.6 in V1-AM2. H-AAD ranges from 1.7 ± 0.8° in V2-TM to 3.8 ± 3.0° in V1-AM2, while the average intra-subject variability of the ankle f/e angle ranges from 1.4 ± 0.2° in V3-NW to 2.2 ± 0.2 in V1-AM2.Fig. 5

View Article: PubMed Central - PubMed

ABSTRACT

Background: In human-centered robotics, exoskeletons are becoming relevant for addressing needs in the healthcare and industrial domains. Owing to their close interaction with the user, the safety and ergonomics of these systems are critical design features that require systematic evaluation methodologies. Proper transfer of mechanical power requires optimal tuning of the kinematic coupling between the robotic and anatomical joint rotation axes. We present the methods and results of an experimental evaluation of the physical interaction with an active pelvis orthosis (APO). This device was designed to effectively assist in hip flexion-extension during locomotion with a minimum impact on the physiological human kinematics, owing to a set of passive degrees of freedom for self-alignment of the human and robotic hip flexion-extension axes.

Methods: Five healthy volunteers walked on a treadmill at different speeds without and with the APO under different levels of assistance. The user-APO physical interaction was evaluated in terms of: (i) the deviation of human lower-limb joint kinematics when wearing the APO with respect to the physiological behavior (i.e., without the APO); (ii) relative displacements between the APO orthotic shells and the corresponding body segments; and (iii) the discrepancy between the kinematics of the APO and the wearer’s hip joints.

Results: The results show: (i) negligible interference of the APO in human kinematics under all the experimented conditions; (ii) small (i.e., < 1 cm) relative displacements between the APO cuffs and the corresponding body segments (called stability); and (iii) significant increment in the human-robot kinematics discrepancy at the hip flexion-extension joint associated with speed and assistance level increase.

Conclusions: APO mechanics and actuation have negligible interference in human locomotion. Human kinematics was not affected by the APO under all tested conditions. In addition, under all tested conditions, there was no relevant relative displacement between the orthotic cuffs and the corresponding anatomical segments. Hence, the physical human-robot coupling is reliable. These facts prove that the adopted mechanical design of passive degrees of freedom allows an effective human-robot kinematic coupling. We believe that this analysis may be useful for the definition of evaluation metrics for the ergonomics assessment of wearable robots.

No MeSH data available.


Related in: MedlinePlus