The autonomous tool (10) has drive motors (12,14) and drive wheels (16,18). An evaluation unit (20) evaluates characteristic of a slippage of the drive wheel. The evaluation unit has a rotational speed sensor (28) and a torque sensor (32). The rotational speed sensor and the torque sensor evaluate rotational torque or rotational speed from the characteristic of the slippage. An independent claim is included for a method for operating autonomous tool.
