Test method for contact safety assessment of a wearable robot -analysis of load caused by a misalignment of the knee joint-

Akiyama, Yasuhiro; Yamada, Yoji; Ito, Koji; Oda, Shiro; Okamoto, Shogo; Hara, Susumu

doi:10.1109/roman.2012.6343807

Cited by 25 publications

(37 citation statements)

References 10 publications

(15 reference statements)

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“…5-6, a sample is given by a 23-year-old Asia female of 165 cm in height. According to the definition of the coordination system in the article (Andriacchi et al, 1998), the coordination system of tibia and femur is built, and a twodimensional tibiofemoral joint model is obtained by using 3-D Guidance driveBAY and trakSTAR.…”

Section: Optimization Results Based On the Working Patternmentioning

confidence: 99%

Kinematic analysis and optimization of a planar parallel compliant mechanism for self-alignment knee exoskeleton

2018

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Abstract. Misalignment between the instantaneous center of rotation (ICR) of human joint and the ICR of wearable robotic exoskeleton widely exists among most of exoskeletons widely used in rehabilitation, which results in discomfort, even endangers human safety. In order to alleviate it, this study focuses on the solution of misalignment in knee joint of lower limb exoskeletons, and proposes a compliant five-bar parallel mechanism, which offers two mobility in sagittal plane, as well as the torsional springs mounted on this mechanism, have the potential to automatically adjust the ICR of output link connected to thigh with respect to the basis link connected to shank. To reach this goal, we build the stiffness model of the mechanism and optimize its variables. And the self-alignment of the compliant five-bar parallel mechanism is verified via experimental investigations.

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Section: Optimization Results Based On the Working Patternmentioning

confidence: 99%

Kinematic analysis and optimization of a planar parallel compliant mechanism for self-alignment knee exoskeleton

2018

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“…In other words, when the misalignment was significant, the generative force was not effectively utilized for foot dorsiflexion. Studies regarding wearable physical assistant robots have similarly reported that misalignments increase the unnecessary contact forces (Akiyama et al, 2012(Akiyama et al, , 2015a(Akiyama et al, , 2015bSchiele and Van der Helm, 2006;Schiele, 2008). is below the ankle: f y is smaller and f z is larger, and (c) is above the ankle: f y is larger and f z is smaller.…”

Section: Effect Of Misalignment Of the Rotation Axesmentioning

confidence: 99%

“…In other words, misalignments may necessarily occur when using stretching machines. Studies on the effects of misalignments of the rotation axes of the machine and biological joints of the elbows, shoulders, and knees (Akiyama et al, 2012(Akiyama et al, , 2015a(Akiyama et al, , 2015bSchiele andVan der Helm, 2006, Jarrasse andMorel, 2012;Zanotto et al, 2015) indicate that the contact forces increase in an undesirable manner. However, studies using ankle stretching machines and those regarding the effects of misalignments on stretching have not been conducted.…”

Section: Introductionmentioning

confidence: 99%

Effective position of the rotation axis of an ankle stretching machine and the effect of misalignment

Shiraishi

Okamoto

Yamada

et al. 2020

JBSE

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The mechanical rotation axes of joint exercisers are believed to operate better when they match the biomechanical axes of human joints. However, there are few studies regarding ankle stretching machines. Further, the maleffects of rotation axis misalignments are not well known. Hence, we investigate the effective positions of rotation axes for ankle stretching machines and the effects of misalignments using a pneumatic-driven stretching machine developed in our previous study (Shiraishi et al., 2020). Eight healthy young males (ages 23.3 ± 1.4 years) participated in stretching exercises while the relative positions of the rotation axes between the machine and ankle were changed via plates installed under the heel. The stretching machine dorsiflexed the feet of the participants, and the dorsiflexion angles and three-axial forces applied to the forefeet were recorded. The measured values at the maximum dorsiflexion angle were evaluated by two-way analysis of variance and/or regression analysis. We determined that the rotation axis of the machine must be placed 7 mm above the lateral ankle because the normal force applied to the forefoot and maximum dorsiflexion angle were large, whereas the friction force was moderate. Further, the relationships among the dorsiflexion angle and contact forces were investigated via covariance selection. The three-axial forces significantly decreased as the axis of the machine was lowered below the ankle. Additionally, the force normal to the sole had large positive effects on the dorsiflexion angle and friction force of the sole, which could damage the skin. The misalignment of the rotation axis increased the contact force at the sole when the axis of the machine was above the ankle or decreased the efficiency of force transmission from the stretching machine to the user's foot when the machine's axis was below the ankle.

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“…Wearable robots are attached closely to the human body and exert assistive torque and force through the area at which fixation occurs [4]- [6]; hence, the safety of wearable robots should be considered carefully. For example, some studies have assessed conduction risks from wearable robots [7], [8] and examined human-robot interaction at the fixation area [9]- [11]. Further, the international standard ISO-13482:2014 [12] requires considering the contact safety of wearable robots.…”

Section: Introductionmentioning

confidence: 99%

A Three-Dimensional Skin-Shape Reproduction Mechanism for Evaluating the Risk of Wounds When Using a Wearable Robot

Sakai

Akiyama

Yamada

et al. 2018

SICE Journal of Control, Measurement, and System Integration

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When using a wearable robot, the interaction force applied at the point of contact may cause skin injuries. Therefore, validating the safety of wearable robots becomes important for their practical application. One method for evaluating contact safety at the fixation area of a wearable robot is to reproduce the relative motion and interaction force that occur at the area on a dummy. However, humans have various shapes, and evaluation of various human skin shapes is required. This study aims to develop a three-dimensional skin-shape reproduction mechanism with which to validate the safety of wearable robots. To that end, we have developed a simulation consisting of a cable-reinforced membrane that estimates surface deformation to examine different dummy shapes. Comparisons between device and simulation shapes validated the process of reproducing human skin and the range of deformation and elasticity of the dummy.

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Test method for contact safety assessment of a wearable robot -analysis of load caused by a misalignment of the knee joint-

Cited by 25 publications

References 10 publications

Kinematic analysis and optimization of a planar parallel compliant mechanism for self-alignment knee exoskeleton

Kinematic analysis and optimization of a planar parallel compliant mechanism for self-alignment knee exoskeleton

Effective position of the rotation axis of an ankle stretching machine and the effect of misalignment

A Three-Dimensional Skin-Shape Reproduction Mechanism for Evaluating the Risk of Wounds When Using a Wearable Robot

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