  An autonomous robot that is able to physically guide humans through narrow
and cluttered spaces could be a big boon to the visually-impaired. Most prior
robotic guiding systems are based on wheeled platforms with large bases with
actuated rigid guiding canes. The large bases and the actuated arms limit these
prior approaches from operating in narrow and cluttered environments. We
propose a method that introduces a quadrupedal robot with a leash to enable the
robot-guiding human system to change its intrinsic dimension (by letting the
leash go slack) in order to fit into narrow spaces. We propose a hybrid
physical Human-Robot Interaction model that involves leash tension to describe
the dynamical relationship in the robot-guiding human system. This hybrid model
is utilized in a mixed-integer programming problem to develop a reactive
planner that is able to utilize slack-taut switching to guide a blind-folded
person to safely travel in a confined space. The proposed leash-guided robot
framework is deployed on a Mini Cheetah quadrupedal robot and validated in
experiments.
