  Kinematic structure of an exoskeleton is the most fundamental block of its
design and is determinant of many functional capabilities of it. Although
numerous upper limb rehabilitation devices have been designed in the recent
years, there is not a framework that can systematically guide the kinematic
design procedure. Additionally, diversity of currently available devices and
the many minute details incorporated to address certain design requirements
hinders pinpointing the core kinematics of the available devices to compare
them against each other. This makes the review of literature for identifying
drawbacks of the state of the art systems a challenging and puzzling task. In
fact, lack of a unifying framework makes designing rehabilitation devices an
intuitive process and prone to biases from currently available designs. This
research work proposes a systematic approach for kinematic design of upper limb
rehabilitation exoskeletons based on conceptual design techniques. Having
defined a solution neutral problem statement based on the characteristics of an
ideal device, the main functionality of the system is divided into smaller
functional units via the Functional Decomposition Method. Various directions
for concept generation are explored and finally, it has been shown that a vast
majority of the current exoskeleton designs fit within the proposed design
framework and the defined functionalities.
