Many people consider GPS to be just another way of saying “navigation.” But there is an equally good way to go about the task that involves much less effort. A robot ant can find its way back to its “nest” just like its role model in the desert.
Dogs, jellyfish, spiders, dragonflies and apes – robot researchers are fond of using animals as blueprints for their work. There is nothing new about this approach. Even Leonardo da Vinci wanted to fly through the air like a bird. Generally, though, this research focuses on the specific way that each particular animal moves.
Not so for the roboticists at Aix-Marseille University. Their AntBot robot certainly cannot completely hide its “superficial” kinship with the desert ant. But the really interesting stuff is hidden inside. While its “relatives” generally get their bearings with the help of global navigation satellite systems (GNSS) like GPS, the robot ant from France follows in the footsteps of its role model and uses sunlight and its own stride-counting system.
The concept is simple: Light waves are electromagnetic waves whose original direction of oscillation is randomly distributed. If the waves are reflected or broken up or if they are sent through a polarizing filter, they will suddenly oscillate only in one level – they are thus polarized. This partially occurs when sunlight passes through the Earth’s atmosphere.
Bees, locusts and, of course, desert ants use this polarized pattern for navigation purposes. It is a highly efficient system. A desert ant has just a few thousand neurons for the job. It uses them to determine the direction of the electromagnetic rays of sunlight, the position of the sun, its own stride count and its speed across the desert floor.
While humans – at least in Hollywood movies – tend to run in circles while in the desert, desert ants can easily find the shortest way home after covering hundreds of meters of structureless terrain.
Robot ant with a sky compass
The researchers have applied this navigation model to the six-legged, 2.3-kilogram robot by using sensors for UV light, for the rate that the ground moves past the eye (optical flow measurement) and for the polarization of sunlight. A pedometer and information about the course of the sun at the appropriate latitudes were added as well.
The job for the AntBot was to find its way “home.” But before it was asked to do so, the robot was sent all over the experiment field. The ant robot easily found its way home regardless of weather conditions. And it performed just as well as much more elaborate and expensive systems do.
Today’s navigation systems used by such things as container ships, delivery drones and cars could be enhanced with an additional “sky compass.” Even the simple AntBot is more exact than the non-military GPS version is. But it needs a little bit of clear sky and daylight. In theory, moonlight would do. More sensitive sensors would help as well. But they do not exist yet.
“AntBot: A six-legged walking robot able to home like desert ants in outdoor environments”, Science Robotics, 02/14/2019.