Samer Mohammed

title: Human gait characterization and movement assistance using wearable robots


The proportion of elderly worldwide was 8% in 1950 and is expected to reach 22% in 2050. The continuous ageing of the worldwide population is a phenomenon that affects the tomorrow’s society and requires to face major scientific, technological, economic and societal challenges.
Biologically, ageing generally results in deficiencies and disorders of the neuro-musculoskeletal system and particularly a loss of the muscular force that alters the equilibrium process and increases the risk of falls and fractures. Such an evolution also affects the daily living activities
and causes a gradual loss of the autonomy, which impacts the elderly’s quality of life. In this context, robotics seems to be a well suited and promising solution to develop assistive systems able to improve the autonomy of elderly during daily living activities such as : standing, sitting,
stairs up/down, etc. Recently, many research works were conducted across the world to develop wearable robots or exoskeletons that can be used as mobility assistive devices allowing to increase the motor skills of the wearers, or as neuro-muscular rehabilitation devices. In this context, the framework of my research activities lies within the assistive robotics and particularly the modeling, identification and control of robotic systems such as lower limb exoskeletons used for movement assistance and rehabilitation. This is supplemented by other research activities on the development of observation functions necessary for, on the one hand, the contextualized control of exoskeletons, and on the other hand, the human gait analysis in a context of diagnosis and therapeutic monitoring of gait pathologies. More particularly, these activities deal with automatic and non-intrusive recognition of daily living activities with a focus on the recognition of the sub-phases of a gait cycle. In this talk, I will present a recent control approach of the LISSI-UPEC lower limb exoskeleton by modulating the original impedance of the wearer’ swinging leg to reduce the muscular efforts during walking. The proposed method ensures compensation of the damping, stiffness and gravity effects of the wearer’s leg to desired levels offering though the possibility to adapt the lower limb wearer’s impedance as a function of the gait phase evolution. EMG activities of the extensor muscles spanning the knee-joint are used as assesment criteria. The results show that the muscular activities required to perform classical daily activity movements, with/without exoskeleton, are effectively reduced by providing lower desired joint damping and stiffness with exoskeleton’s assistance. The talk will be concluded by presenting some ongoing work and future perspectives. 
































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