Students at the University of Southampton have developed a low cost robot for swarm intelligence research.
"The clever issue is using surface mount motors from mobile phone vibrators so the whole thing can be made on a standard production line," academic Klaus-Peter Zauner told Electronics Weekly. "There are no special components and no hand assembly."
Estimated price of the 30x28x12mm machine is £24.
Zauner was at pains to point out he had nothing to do with the initial idea. "Students built the prototype by taking old mobile phones apart," he said. "I was so impressed that I arranged some funding."
Following natural examples including bees and ants, swam intelligence research attempts to discover 'emergent behaviour - where individuals following simple rules work together to produce complex results.
The whole process can be modelled in computers - there is a commercial spam email detection system that uses communicating software 'agents' - but sometimes the is no substitute for tens, hundreds, or even thousands of physical robots.
With an eye on cost, component count has been kept to a minimum.
The robots two surface-mount motors have wheels on their spindles and are soldered directly to the underside of the double-sided PCB which is also the robot's chassis.
Power comes from under-slung 320mAh Li-ion cell sufficient for 1.5h of operation between charges.
For their size, the robots move quickly: EW estimates they travel at somewhere between 300 and 500mm/s.
On-board intelligence comes from a 16MHz MSP430 microcontroller from Texas Instruments with 16kbyte flash and 512byte RAM. Of this, 6kbyte flash and 256byte RAM are needed to work the machine, the rest is available for behavioural algorithms
Three fast infrared sensors (black in the photos), mounted on top of the PCB facing horizontally at 120[deg] intervals, allow data to be received from other robots in any direction.
Three infra-red transmitters (white), mounted evenly between the receivers complete the 588bit/s broadcast-only communication link.
According to Zauner, the transmitters, and the receivers, are operated in parallel, during communication. Range is deliberately limited to around 10cm so robots communicate only with immediate neighbours.
IR communication allows not only co-operative behaviour but, as the robots can flash their own programme memory, allows new operating code to be passed around.
The protocol for re-programming includes a re-transmission request for robots that miss a code segment.
The IR transmitters and receivers can also be used as a simple wall detector. "When they start receiving their own packets, they know they are bouncing off something nearby," said Zauner.
Lastly, the three receivers can also be used to estimate the direction of bright light sources in their environment.
The only other sensor is a infra-red transmitter-receiver pair mounted underneath at the front which allows the robot to tell if it is over a dark or light surface.
The university's robot experiment arena has black wallpaper on the floor. "Someone took a robot to a DIY store and found the paper that reflected least," said Zauner.
One of the experimental objects made by the team is a balsa wood puck the size of a 2p coin.
It is stuck to a slightly larger circular piece of white paper and the geometry is such that the dark-light sensor can only see the white paper when the robot is nose-on to the puck.
Using the three top IR sensors as directional light detectors, and the underneath sensor, rules have been developed that cause a group of the robots to nudge this puck away from a bright light at the edge of the arena.
The robots know when they need to be charged and know where their charger is.
Four bare copper wires at the rear of the chassis, two for power and two for ground, pick up current for recharging. The two ground wires are bent so they double as skids in lieu of wheels.
Aside from the charging circuit, the only other components are a handful of drive transistors and a bi-colour LED on the top to indicate activity to human bystanders - a cluster of green LEDs in the arena, for example, indicating the swarm has found something of interest.
Zauner and the students: Alexis Johnson, Stephen English, Jeffrey Gough, Robert Spanton and Joanna Sun are part of the University's newly-formed Science and Engineering of Natural Systems (SENSe) group within its School of Electronics and Computer Science (ECS).