  Preserving and encouraging mobility in the elderly and adults with chronic
conditions is of paramount importance. However, existing walking aids are
either inadequate to provide sufficient support to users' stability or too
bulky and poorly maneuverable to be used outside hospital environments. In
addition, they all lack adaptability to individual requirements. To address
these challenges, this paper introduces WANDER, a novel Walking Assistive
omNi-Directional Exo-Robot. It consists of an omnidirectional platform and a
robust aluminum structure mounted on top of it, which provides partial body
weight support. A comfortable and minimally restrictive coupling interface
embedded with a force/torque sensor allows to detect users' intentions, which
are translated into command velocities by means of a variable admittance
controller. An optimization technique based on users' preferences, i.e.,
Preference-Based Optimization (PBO) guides the choice of the admittance
parameters (i.e., virtual mass and damping) to better fit subject-specific
needs and characteristics. Experiments with twelve healthy subjects exhibited a
significant decrease in energy consumption and jerk when using WANDER with PBO
parameters as well as improved user performance and comfort. The great
interpersonal variability in the optimized parameters highlights the importance
of personalized control settings when walking with an assistive device, aiming
to enhance users' comfort and mobility while ensuring reliable physical
support.
