Meet the PMB-2: an autonomous mobile base for robotic projects. It is fully compatible with ROS and customizable. This mobile base is navigation ready. You can add your own sensors to do more with it. The PMB-2 has a max payload of 50kg and 1 m/s max velocity. It measures 0.54m x 0.54m x 0.3m.
The PMB-2 is modular. You can upgrade its software and hardware. This is the same base used by TIAGo and StockBot. More information is available here.