US Patent 10300783 Statically stable robot using wheel with inner system

The invention relates to a vehicle including a chassis and a pair of wheels supported in spaced apart relationship by the chassis for rotation about a common axis. A pair of drive modules is associated with the respective wheels. The drive modules and the chassis are connected for rotation as a sub-assembly relative to the wheels about the common axis with the centre of mass of the sub-assembly below the common axis in a static equilibrium position. Each of the drive modules is housed substantially within the respective wheel.