Exoskeleton+Biomechanics

back to Load Carrying Exoskeleton = = =[|Human Gait]=


 * Human gait** is the way [|locomotion] is achieved using human [|limbs]. Human gait is defined as bipedal, biphasic forward propulsion of centre of gravity of human body, in which there is alternate sinuous movements of different segments of the body with least expenditure of energy. Different gaits areby differences in limb movement patterns, overall velocity, forces, kinetic and potential energy cycles, and changes in the contact with the [|surface] ([|ground], [|floor], etc.).



Expand on: Inertia Weight Distribution

=Resources=

Journal Articles
Limited research has been done on exoskeletons to enable faster movements of the lower extremities. An exoskeleton’s mechanism can actually hinder agility by adding weight, inertia and friction to the legs; compensating inertia through control is particularly difﬁcult due to instability issues. The added inertia will reduce the natural frequency of the legs, probably leading to lower step frequency during walking. We present a control method that produces an approximate compensation of an exoskeleton’s inertia. The aim is making the natural frequency of the exoskeleton-assisted leg larger than that of the unaided leg. The method uses admittance control to compensate for the weight and friction of the exoskeleton. Inertia compensation is emulated by adding a feedback loop consisting of low-pass ﬁltered acceleration multiplied by a negative gain. This gain simulates negative inertia in the low-frequency range. We tested the controller on a statically supported, single-degree-of-freedom exoskeleton that assists swing movements of the leg. Subjects performed movement sequences, ﬁrst unassisted and then using the exoskeleton, in the context of a computer-based task resembling a race. With zero inertia compensation, the steady-state frequency of the leg swing was consistently reduced. Adding inertia compensation enabled subjects to recover their normal frequency of swing.

This study investigated the eﬀects on metabolic cost and gait biomechanics of using a prototype lower-body exoskeleton (EXO) to carry loads. Nine US Army participants walked at 1.34 m/s on a 0% grade for 8 min carrying military loads of 20 kg, 40 kg and 55 kg with and without the EXO. Mean oxygen consumption (VO2) scaled to body mass and scaled to total mass were signiﬁcantly higher, by 60% and 41% respectively, when the EXO was worn, compared with the control condition. Mean _VO2 and mean _VO2 scaled to body mass signiﬁcantly increased with load. The kinematic and kinetic data revealed signiﬁcant diﬀerences between EXO and control conditions, such as walking with a more ﬂexed posture and braking with higher ground reaction force at heel strike when wearing the EXO. Study ﬁndings demonstrate that the EXO increased users’ metabolic cost while carrying various loads and altered their gait biomechanics compared with conventional load carriage.

The study investigated the eﬀects of using a lower body prototype exoskeleton (EXO) on static limits of stability and postural sway. Measurements were taken with participants, 10 US Army enlisted men, standing on a force platform. The men were tested with and without the EXO (15 kg) while carrying military loads of 20, 40 and 55 kg. Body lean to the left and right was signiﬁcantly less and postural sway excursions and maximal range of movement were signiﬁcantly reduced when the EXO was used. Hurst values indicated that body sway was less random over short-term time intervals and more random over long-term intervals with the EXO than without it. Feedback to the user’s balance control mechanisms most likely was changed with the EXO. The reduced sway and relatively small changes in sway with increasing load weights suggest that the EXO structure may have functioned to provide a bracing eﬀect on the body.