摘要 |
The apparatus comprises a platform (28), two ground engaging drive wheels (2) positioned one at each side of the platform (28), drive means (11, 12) for independently driving each drive wheel, a control device (14) for continuously controlling the drive means (11, 12), whereby operation of the drive means (11, 12) causes the apparatus to progress over a predetermined route within the predetermined area, and at least one sensor (6) coupled to the control device (14) for sensing the proximity of signal means (23, 24) defining the borders of the predefined area. |