The present disclosure relates to an articulated,self-propelled robotic tool1, having a first platform 3 with a first wheel assembly 5 and a second platform 7 with a second wheel assembly 9. A link arrangement 15, 17, 19, 21 connects the first and second platforms at a turning axis 11. A goniometer arrangement senses the angle between the first and second platforms, and comprises a magnet 29 attached to a first part 17 connected to the first platform, and a Hall sensor arrangement 31 attached to the second platform 7.
