  Mobile manipulators for indoor human environments can serve as versatile
devices that perform a variety of tasks, yet adoption of this technology has
been limited. Reducing size, weight, and cost could facilitate adoption, but
risks restricting capabilities. We present a novel design that reduces size,
weight, and cost, while supporting a variety of tasks. The core design consists
of a two-wheeled differential-drive mobile base, a lift, and a telescoping arm
configured to achieve Cartesian motion at the end of the arm. Design extensions
include a 1 degree-of-freedom (DOF) wrist to stow a tool, a 2-DOF dexterous
wrist to pitch and roll a tool, and a compliant gripper. We justify our design
with anthropometry and mathematical models of static stability. We also provide
empirical support from teleoperating and autonomously controlling a commercial
robot based on our design (the Stretch RE1 from Hello Robot Inc.) to perform
tasks in real homes.
