TidyBot++: An Open-Source Holonomic Mobile Manipulator for Robot
  Learning
Authors: name: Jimmy Wu, name: William Chong, name: Robert Holmberg, name: Aaditya Prasad, name: Yihuai Gao, name: Oussama Khatib, name: Shuran Song, name: Szymon Rusinkiewicz, name: Jeannette Bohg

Exploiting the promise of recent advances in imitation learning for mobile
manipulation will require the collection of large numbers of human-guided
demonstrations. This paper proposes an open-source design for an inexpensive,
robust, and flexible mobile manipulator that can support arbitrary arms,
enabling a wide range of real-world household mobile manipulation tasks.
Crucially, our design uses powered casters to enable the mobile base to be
fully holonomic, able to control all planar degrees of freedom independently
and simultaneously. This feature makes the base more maneuverable and
simplifies many mobile manipulation tasks, eliminating the kinematic
constraints that create complex and time-consuming motions in nonholonomic
bases. We equip our robot with an intuitive mobile phone teleoperation
interface to enable easy data acquisition for imitation learning. In our
experiments, we use this interface to collect data and show that the resulting
learned policies can successfully perform a variety of common household mobile
manipulation tasks.