WHEN you are in hostile territory, it pays to stick together 鈥� especially if you are a robot. Falling into line will be easier with an innovative communication system that combines the clout of robots鈥� individual radio antennas, making sure they stay in touch with their headquarters.
Communicating with robots on the ground gets harder once they move beyond the line of sight, but equipping a group with the 鈥渟parse antenna鈥� technology improves communications by extending the radio range. The technology eliminates dead spots, where contact is lost completely, and minimises interference from large buildings or potential signal jammers.
It could make it easier to communicate with robots working in hard-to-reach environments, such as urban disaster areas.
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The robots are the product of a joint project. of Adaptive Communications Research in San Diego, California, is leading the antenna work. On the robotics side is at Santa Clara University, also in California.
To form the sparse array antenna the robots are programmed to arrange themselves 鈥� usually in circular patterns or grids 鈥� at roughly equal intervals, from 10 centimetres to several metres apart. The signal-processing software then turns the robots鈥� radio-controlled antennas into a powerful transmitter. The software uses the individual robot鈥檚 position and the properties of its radio signal to enhance the overall signal. That super-signal is then funnelled through one robot to communicate with HQ.
With the robots arranged in a smart antenna array you get what鈥檚 called diversity gain, says Okamoto. 鈥淭his enables the signals from the different antennas to be added constructively,鈥� he says. So you don鈥檛 get 鈥渕ultipath fading鈥�, which happens when radio signals reach the receiving antenna by two or more paths and the resultant interference causes dead spots, he adds.
With eight robots, says Okamoto, signal gain is equivalent to a 60-fold increase in signal strength. However, there is a limit to how much you can reduce the multipath fading, so the benefits improve for up to about 12 robots before tailing off.
The transmission-sharing software and manoeuvre-control for the robot formation are complete, and the robots needed for an integrated demonstration should be complete within three months, says Kitts.
鈥淚n principle, this idea has some merit,鈥� says , director of the Bristol Robotics Laboratory at the University of Bristol, UK. 鈥淭he trick will be to get the robots to position themselves and then maintain their relative position within the tolerances of the transmission media.鈥�
