Human leg | EPFL Graph Search

The human leg is the entire lower limb of the human body, including the foot, thigh or sometimes even the hip or buttock region. The major bones of the leg are the femur (thigh bone), tibia (shin bone), and adjacent fibula. The thigh is between the hip and knee, while the calf (rear) and shin (front) are between the knee and foot. Legs are used for standing, many forms of human movement, recreation such as dancing, and constitute a significant portion of a person's mass. Evolution has led to the human leg's development into a mechanism specifically adapted for efficient bipedal gait. While the capacity to walk upright is not unique to humans, other primates can only achieve this for short periods and at a great expenditure of energy. In humans, female legs generally have greater hip anteversion and tibiofemoral angles, while male legs have longer femur and tibial lengths. Structure In human

On the dynamics of human locomotion and co-design of lower limb assistive devices

Jesse van den Kieboom

Recent developments in lower extremities wearable robotic devices for the assistance and rehabilitation of humans suffering from an impairment have led to several successes in the assistance of people who as a result regained a certain form of locomotive capability. Such devices are conventionally designed to be anthropomorphic. They follow the morphology of the human lower limbs. It has been shown previously that non-anthropomorphic designs can lead to increased comfort and better dynamical properties due to the fact that there is more morphological freedom in the design parameters of such a device. At the same time, exploitation of this freedom is not always intuitive and can be difficult to incorporate. In this work we strive towards a methodology aiding in the design of possible non-anthropomorphic structures for the task of human locomotion assistance by means of simulation and optimization. The simulation of such systems requires state of the art rigid body dynamics, contact dynamics and, importantly, closed loop dynamics. Through the course of our work, we first develop a novel, open and freely available, state of the art framework for the modeling and simulation of general coupled dynamical systems and show how such a framework enables the modeling of systems in a novel way. The resultant simulation environment is suitable for the evaluation of structural designs, with a specific focus on locomotion and wearable robots. To enable open-ended co-design of morphology and control, we employ population-based optimization methods to develop a novel Particle Swarm Optimization derivative specifically designed for the simultaneous optimization of solution structures (such as mechanical designs) as well as their continuous parameters. The optimizations that we aim to perform require large numbers of simulations to accommodate them and we develop another open and general framework to aid in large scale, population based optimizations in multi-user environments. Using the developed tools, we first explore the occurrence and underlying principles of natural human gait and apply our findings to the optimization of a bipedal gait of a humanoid robotic platform. Finally, we apply our developed methods to the co-design of a non-anthropomorphic, lower extremities, wearable robot in simulation, leading to an iterative co-design methodology aiding in the exploration of otherwise hard to realize morphological designs

EPFL2014

Characterization of lower-limbs inter-segment coordination during the take-off extension in ski jumping

Kamiar Aminian, Julien Chardonnens, Julien Favre

Take-off, the most important phase in ski jumping, has been primarily studied in terms of spatio-temporal parameters, with little known about its motor control aspects. This study aims to assess the inter-segment coordination of the shank-thigh and thigh-sacrum pairs using the continuous relative phase (CRP). In total 87 jumps were recorded from 33 athletes with an inertial sensor-based system. The CRP curves indicated that the thighs lead the shanks during the first part of take-off extension and that the shanks rotated faster at take-off extension end. The thighs and sacrum first rotated synchronously, with the sacrum then taking lead, with finally the thighs rotating faster. Five characteristic features were extracted from the CRP and their relationship with jump length was tested. Three features of the shank-thigh pair and one of the thigh-sacrum pair reported a significant association with jump length. It was observed that athletes who achieved longer jumps had their thighs leading their shanks during a longer time, with these athletes also having a more symmetric movement between thighs and sacrum. This study shows that inter-segment coordination during the take-off extension is related to performance and further studies are necessary to contrast its importance with other ski jumping aspects.

Elsevier2013

A Novel Five-leg Inverter PWM Technique for Two-Motor Centre-Driven Winders

Drazen Dujic

Two three-phase motors can be controlled independently using a five-leg inverter as the supply, with one leg being common to both machines. Major shortcoming of this topology for general applications is the need to double the DC bus voltage in order to achieve the same speed control range as with the standard dual three-phase voltage source inverter (VSI) supply. Further, the semi-conductors of the common leg have to withstand up to twice the operating current of the other legs. This paper investigates use of the five-leg inverter topology for a specific constant-power two-motor centre-driven winder drive, where the listed drawbacks can be either fully avoided or at least reduced. A PWM method is developed, which enables control over how the available DC bus voltage is allocated to the two motors. This PWM technique, when used for two-motor winder control, enables operation without any increase in the required DC link voltage. The increase of the switch current rating in the common inverter leg can be kept at 50%, meaning that the five-leg topology enables a saving in the capital cost when compared to the standard dual three-phase topology.

IEEE2007

On the dynamics of human locomotion and co-design of lower limb assistive devices

Jesse van den Kieboom

EPFL2014