Affordable Active Lower Limbs Exoskeleton for People with Paraplegia

Abstract

After a broad introduction to the medical and biomechanical background and detailed review of orthotic devices, two newly developed lower limbs exoskeletons for paraplegics are presented in this study. There was found out the main challenges of designing devices for paraplegic walking can be summarized into three groups, stability and comfort, high efficiency or low energy consumption, dimensions and weight. These all attributes have to be moreover considered and maintained during manufacturing of affordable device while setting a reasonable price of the final product. A new economical device for people with paraplegia which tackles all problems of the three groups is introduced in this work. The main idea of this device is based on HALO mechanism. HALO is a compact passive medial hip joint orthosis with contralateral hip and ankle linkage, which keeps the feet always parallel to the ground and assists swinging the leg. The medial hip joint is equipped with one actuator in the new design and the new active exoskeleton is called @halo. Due to this update, we can achieve more stable and smoother walking patterns with decreased energy consumption of the users, yet maintain its compact and lightweight features. It was proven by the results from preliminary experiments with able-bodied subjects during which the same device with and without actuator was evaluated. Waddling and excessive vertical elevation of the centre of gravity were decreased by 40% with significantly smaller standard deviations in case of the powered exoskeleton. There was 52% less energy spent by the user wearing @halo which was calculated from the vertical excursion difference. There was measured 38.5% bigger impulse in crutches while using passive orthosis, which produced bigger loads in upper extremities musculature. The inverse dynamics approach was chosen to calculate and investigate the loads applied to the upper extremities. The result of this calculation has proven that all main muscle groups are engaged more aggressively and indicate more energy consumption during passive walking. The new @halo device is the first powered exoskeleton for lower limbs with just one actuated degree of freedom for users with paraplegia.