  When we develop wearable assistive devices comfort and support are two main
issues needed to be considered. In conventional design approaches, the degree
of freedom of wearer's joint movement tends to be oversimplified. Accordingly,
the wearer's motion becomes restrained and bone/ligament injuries might occur
in case of unexpected fall. To mitigate those issues, this letter proposes a
novel joint link mechanism inspired by a human spine structure as well as
functionalities. The key feature of the proposed spine-like joint link
mechanism is that hemispherical blocks are concatenated via flexible synthetic
fiber lines so that their concatenation stiffness can be adjusted according to
a tensile force. This feature has a great potentiality for designing a wearable
assistive devices that can support aged people's sit-to-stand action or augment
a spinal motion by regulating the concatenation stiffness. In addition, the
concatenated hemispherical blocks enables the wearer to move his/her joint with
the full degree of freedom, which in turn, increases wearer's mobility and
prevents joint misalignment. The experimental results with a testbed and a
pilot wearer substantiated that the spine-like joint link mechanism can serve
as a key component to design the wearable assistive devices for better mobility
and safety.
