Enhancing Elderly Mobility: A Sturdy, Two-Body Robot for Handlebar Placement in Any Location.

Grab bars are widely used to provide elderly persons with support for daily activities, but their utility is limited by room geometry, cost of installation, and potential obstruction of other movements. We address these challenges through a mobile robot that can place a handlebar at any point in space, to optimally support postural transitions. Informed by a survey of elderly people and care professionals, we propose a novel two-body robot structure, consisting of two small-footprint mobile bases connected by a four bar linkage. Kinematic analysis shows that the structure can bear the entire weight of a human body, and provides secure support without sliding or tipping. The robot has a minimum width of 29.2 cm to be maneuverable within confined spaces, making it likely the slimmest robot ever developed for mobile postural assistance. A control plan for geometric path tracking is proposed that is generalizable to all robots with two coupled, nonholonomic, mobile bases. This consists of a leader-follower scheme as well as various enhancements to path tracking and dead reckoning that allow the robot to accurately follow a series of waypoints. On an 0.4 m long test path, despite significant tread slippage, a 1:4 scale model of the robot achieved a root mean square error of 0.01 m and a deviation of 0.015 m from the path terminus, using only the encoders on the treads and robot frame. Finally, the robot's utility for supporting activities of daily living is demonstrated as a proof of concept.