The present invention relates to a drive unit (10) comprising a rolling means (12) intended to be infrictional engagement with a surface over which said drive unit (10) is intended to move. The drive unit (10) also comprises a first driving means (14) and a second driving means (16), co-operatively operable to provide both propulsion and steering of said drive unit (10) while eliminating slippage between said rolling means (12) and said surface. The first driving means (14) is arranged on a rotatable support means (18) rotatable about a center axis (c.a.) and is operable to rotate said rolling (12) about a roling axis. rolling means (12) is displaced a predetermined distance from said center axis (c.a.), and the second driving means (16) is operable rotate the support means (18) about said center axis (c.a.).