A robot can autonomously navigate inside a building using a magnetometer and a detailed map of local magnetic anomalies.
The technique could provide a means for people as well as robots to find their way around large buildings.
Satellite navigation systems like Russia’s GLONASS and the European Union’s Galileo can provide accurate location information all over the planet, but they have weaknesses. Signals can be jammed in times of conflict, as GPS signals currently are in Ukraine, and they tend to be difficult to pick up indoors.
The US Air Force has run tests of magnetic anomaly navigation on fighter jets, which relies on the unique patterns produced by the geology of Earth’s crust and, crucially, can’t be jammed.
Now, Prashant Ganesh at the University of Florida and his colleagues have collaborated with a scientist from the Air Force Research Lab at Eglin Air Force Base in Florida to demonstrate that a similar technique can be used indoors by robots.
The team created a map of the magnetic anomalies in an 11-metre-by-6-metre area of a lab and showed that a robot equipped with a magnetometer could navigate to waypoints despite not being told its starting position.
Metal pipes beneath the floor became landmarks for the robot just as mountains are for aircraft
Ganesh says Air Force tests have focused on taking magnetic measurements and GPS readings together to test the accuracy of the concept, and his team’s robot is one of the first demonstrations of real-time, autonomous magnetic anomaly navigation.
The team’s small robot takes a reading of the magnetic field at its initial location and generates a database of possible locations based on its anomaly map. As the robot moves – at a constant rate of 20 centimetres a second – it gathers more readings, and ranks its location guesses in terms of probable correctness. Within several readings, the robot can determine where it is and begin to navigate to a target destination.
Ganesh says that when mapping the lab, the sensors picked up on metal pipes beneath the floor, which became landmarks for the robot just as mountains or ridges would be for an aircraft.
It may be some time before magnetic navigation becomes a practical consumer tool. The magnetic sensors used cost $10,000 and, at 16 centimetres long, are too bulky to fit inside a smartphone or tablet.
