Navigation possibilities without GPS or 5G: the AntBot solution
Résumé
Autonomous navigation has become one of the major technological challenges of the 21st century because the need for robotic mobility is huge. Several outdoor location systems are now available: civil GNSS (Global Navigation Satellite System) with an accuracy of 5 m to 30 m depending on the weather and the environment, or GSM (Global System for Mobile communications) which self-localises using terrestrial networks by merging GSM and GNSS information. This can achieve an accuracy of 5 to 10 cm under optimal signal reception conditions. These technological solutions will work, but they also require significant energy due to radio emissions. Moreover, in the event of a blackout or service interruption, how will we guarantee the continuity of the localisation service? The solution lies in nature as many animals navigate with ease and precision without using such conventional systems. Bio-inspired solutions would allow navigation in the event of major faults in the GNSS and GSM networks. Directly inspired by the desert ant Cataglyphis fortis, the hexapod robot AntBot self-localises by counting its strides, measures its distance travelled from the integration of the visual scrolling of the ground and estimates its course using a celestial compass. AntBot repositions itself with an error of just 7 cm, almost 100 times lower than civil GNSS. AntBot’s celestial compass detects ultraviolet radiation scattered by the atmosphere. This compass is inspired by the dorsal part of the compound eyes of insects, and it only requires two photodiodes surmounted by linear rotary polarising filters that scan the sky dome. It thus measures the angle of polarisation of the light from the sky to provide the robot with a heading (accuracy: ~0.4°). The heading detection model is directly inspired by the polarisation vision used by insects. Although this biological model appears simple it is very interesting, due to its sensory parsimony, for developing bio-inspired instruments capable of providing directional information. The performance of this new bio-inspired navigation instrument attest to the innovative, reliable and robust nature of this optical compass for obtaining course information, and it is already the subject of research with industrial partners.