Volvo is experimenting with the use of roads embedded with magnets to guide the movements of driverless vehicles.
At a testing facility in Hallered, Sweden, Volvo engineers have embedded small magnets along tracts of road to guide the movements of vehicles equipped with highly sensitive sensors.
Volvo’s engineers didn’t want to grease the skids for the experimental technology, building the first makeshift road on difficult terrain in a patch of forest. According a report on the project, the road consisted of “a layer of stones of various sizes and on top of that a thick layer of soil that had formed over the years.”
The engineers inserted a series of magnets of two types below the road surface – neodymium magnets measuring 20 millimetres in diameter and 10 millimetres in thickness, and broad but flatter ferrite magnets measuring 30 millimetres in diameter and five millimetres in thickness.
In total, 100 of the magnets were placed along 100 metres of the forest roadway, deposited in plastic tubes inserted into the road in vertical positions, the openings of which were situated just below the surface.
According to the results of testing the road was capable of calculating the position of a sensor-equipped vehicle within 10 centimetres when it was travelling at speeds of almost 45 miles (approximately 72 kilometres) per hour.
Similar tests performed on a paved length of roadway, to which the magnets were attached using glue, produced even more impressive results, with the sensors capable of calculating the position of the vehicle to the same degree of accuracy at speeds of over 90 miles (145 kilometres) per hour.
The key to the success of the experiment was the use of a highly sensitive sensor rig which was capable of harvesting data while passing over the small magnets at rapid speeds.
The sensors had to have a sampling rate of at least 400 readings per second when travelling over 90 miles per hour – a staggering amount given that standard magnetic sensors have a rate of only three samples per second when within centimetres of their target.
Volvo managed to produce a sensor setup capable of a 500 readings per second, by putting together a rig comprised of five sensor modules, consisting in turn of 15 small modules made from Honeywell HMC1053 magnetoresistive sensors.
In Volvo’s opinion, magnets are a better means of guiding automated vehicles than electronic transmission, as they are capable of operating in all weather conditions as well as in the presence of obstacles.
Calculations also indicate that the system is reasonably economical, with the sensor rigs costing only around $109 each when made at a scale of 50,000 units. The cost for retrofitting existing highways would be around $24,405 per kilometre, and would entail installing seven parallel lines of magnets separated by a distance of 2.8 metres from each other on a standard two-lane road.
The Swedish company has strong ambitions for the development autonomous vehicles. It commenced testing of driverless cars in 2011 and recently launched the Drive Me program, which aspires to have 100 autonomous vehicles running on Gothenburg roads by 2017.