ACE-Ankle: A Novel Sensorized RCM (Remote-Center-of-Motion) Ankle Mechanism for Military Purpose Exoskeleton

SummaryThis paper presents a novel three-degree of freedom (DOF) sensorized remote-center-of-motion (RCM) ankle module for a military-purpose lower-limb exoskeleton. A military-purpose exoskeleton should assist and follow the fast and dexterous motion of a soldier in rough terrain environments. Among the lower-limb joints, the ankle joint plays an important role in stabilizing walking motion during the stance phase. Thus, aligning the rotation center of the ankle module with the center of the wearer’s ankle is very important to reduce potential risks and fatigue of a soldier. To this end, the ankle exoskeleton was designed using two spherical chains. The two spherical chains were designed such that the intersection of all revolute pairs, which consist of the spherical chains, is located close to the rotation center of the wearer’s ankle. In addition, three encoders are attached to each of the three revolute pairs of a spherical chain to measure the three-DOF orientation of the ankle mechanism. For the design, the required range of motion is analyzed via gait analysis in three environment conditions. Forward and inverse kinematic relations are derived, and the workspace of the ankle is analyzed. For the prototype ankle mechanism, the range of motion and measurement performance are verified by a static experiment. In addition, comparative studies between the proposed RCM ankle and an ankle mechanism with offset rotation center are performed for three walking conditions: level walking, ascending and descending stairs, and a vertical slope. Via comparative study, it is confirmed that, compared to the ankle mechanism with offset center of rotation, the proposed RCM ankle is advantageous for sensing wearer’s ankle motion and reducing mechanical interference to wearer’s natural ankle motion.

Download Full-text

Effect of prosthetic ankle units on the gait of persons with bilateral trans-femoral amputations

Prosthetics and Orthotics International ◽

10.1080/02699200701847244 ◽

2008 ◽

Vol 32 (1) ◽

pp. 111-126 ◽

Cited By ~ 30

Author(s):

Lexyne L. McNealy ◽

Steven A. Gard

Keyword(s):

Power Generation ◽

Range Of Motion ◽

Ankle Joint ◽

Lower Limb ◽

Stance Phase ◽

Sagittal Plane ◽

The Body ◽

Control Group ◽

Initial Contact ◽

Ankle Motion

In able-bodied individuals, the ankle joint functions to provide shock absorption, aid in foot clearance during the swing phase, and provides a rocker mechanism during stance phase to facilitate forward progression of the body. Prosthetic ankles currently used by persons with lower limb amputations provide considerably less function than their anatomical counterparts. However, increased ankle motion in the sagittal plane may improve the gait of persons with lower limb amputations while providing a more versatile prosthesis. The primary aim of this study was to examine and quantify temporal-spatial, kinematic, and kinetic changes in the gait of four male subjects with bilateral trans-femoral amputations who walked with and without prosthetic ankle units. Two prosthesis configurations were examined: (i) Baseline with only two Seattle LightFoot2 prosthetic feet, and (ii) with the addition of Endolite Multiflex Ankle units. Data from the gait analyses were compared between prosthetic configurations and with a control group of able-bodied subjects. The amputee subjects' freely-selected walking speeds, 0.74 ± 0.19 m/s for the Baseline condition and 0.81 ± 0.15 m/s with the ankle units, were much less than that of the control subjects (1.35 ± 0.10 m/s). The amputee subjects demonstrated no difference in walking speed, step length, cadence, or ankle, knee, and hip joint moments and powers between the two prosthesis configurations. Sagittal plane ankle range of motion, however, increased by 3–8° with the addition of the prosthetic ankle units. Compared to the control group, following initial contact the amputee subjects passively increased the rate of energy storage or dissipation at the prosthetic ankle joint, actively increased the power generation at the hip, and increased the extension moment at the hip while wearing the prosthetic ankle configuration. The amputee subjects increased the power generation at their hips, possibly as compensation for the reduced rate of energy return at their prosthetic ankles. Results from subject questionnaires administered following the gait analyses revealed that the prosthetic ankle units provided more comfort during gait and did not increase the perceived effort to walk. The subjects also indicated that they preferred walking with the prosthetic ankle units compared to the Baseline configuration. The results of the study showed that the prosthetic ankle units improved sagittal plane ankle range of motion and increased the comfort and functionality of the amputee subjects’ prostheses by restoring a significant portion of the ankle rocker mechanism during stance phase. Therefore, prosthetic ankle mechanisms should be considered a worthwhile option when prostheses are prescribed for persons with trans-femoral amputations.

Download Full-text

Analyzing Motor Primitives of Healthy Subjects Wearing a Lower Limb Exoskeleton

10.26678/abcm.cobem2017.cob17-1214 ◽

2017 ◽

Author(s):

Wilian dos Santos ◽

Samuel Lourenco ◽

Adriano Siqueira ◽

Polyana Ferreira Nunes

Keyword(s):

Lower Limb ◽

Healthy Subjects ◽

Motor Primitives ◽

Lower Limb Exoskeleton

Download Full-text

INFLUENCE OF FOOT INSOLE ON THE GAIT PERFORMANCE IN SUBJECTS WITH FLAT FOOT DISORDER

Journal of Mechanics in Medicine and Biology ◽

10.1142/s0219519419500507 ◽

2019 ◽

Vol 19 (06) ◽

pp. 1950050

Author(s):

M. T. KARIMI ◽

R. B. TAHMASEBI ◽

B. SATVATI ◽

F. FATOYE

Keyword(s):

Range Of Motion ◽

Ankle Joint ◽

Lower Limb ◽

Walking Speed ◽

Force Plate ◽

Flat Foot ◽

Gait Performance ◽

Positive Effects ◽

Significant Difference ◽

Foot Disorder

Flat foot is the most common foot disorder that influences the alignment of the lower limb structure. It is controversial whether the use of foot insole influences kinetic and kinematic of the leg or not. Therefore, this study investigated the influence of foot insole on the gait performance in subjects with flat foot disorder. A group of flat foot subject was recruited into this study (the number of subjects was 15). The motion of the leg joints was determined using the Qualysis motion analysis system. Moreover, the force applied on the lower limb was recorded by a Kistler force plate. The range of motion of the lower limb joints, the moments applied on the lower limb joints and force transmitted through the leg were the parameters used in this study. The difference between these parameters during walking with and without insole was evaluated using the paired [Formula: see text]-test. Significant value was set at [Formula: see text]. There was no significant difference between the range of motion of ankle joint while walking with and without insole. However, the medial directed force applied on the leg decreased significantly [Formula: see text]. The use of foot insole did not influence the moments transmitted through the hip and knee joints. The walking speed of the subjects improved while walking with foot insole. Use of foot insole influenced the magnitude of the force applied on the leg and the adductor moment of ankle joint due to its influence on foot alignment. As the walking speed of the improved subjects follows the use of insole, it can be concluded that it may have a positive effects on the performance of flat foot subjects.

Download Full-text