A Novel Design of Unpowered Exoskeleton for Loaded Walking Using Only Hip Abduction Torque

An upper extremity device can help humans when they are walking with a load. However, when using such a device that does not have lower limb parts, the upper and lower bodies of the wearer should support the weight of the load. To solve this limitation, this study proposes an unpowered wearable exoskeleton that can reduce the weights of loads felt by the wearer when they are walking. Using supporting force, trunk extension, and loaded walking tests, for a load weight of 12 kgf, the exoskeleton could reduce the weight transmitted to the wearer by 7 kgf, decrease the human trunk extension angle by up to 1.8° compared to that in case of an upper extremity device, and lower the net metabolic rate of the wearer by up to 47.41% during loaded walking. Especially, such reductions in the net metabolic rate have not been reported to date. These three primary results indicate that the exoskeleton in this article can be used to augment the human load-carrying capability and solve the structural problems associated with the use of an upper extremity device. Furthermore, because the exoskeleton requires no power sources and actuators, it is energy-efficient and can be used in the water environments. This exoskeleton is economical owing to its simple structure. Moreover, the model verified in this paper can be utilized in other similar systems having a spring mechanism to optimize the systems.