On its own, each robot would 'just get lost' but as a colony they can navigate
Scientists in the US have built and tested robotic ants that they say behave just like a real ant colony.
The robots do not resemble their insect counterparts; they are tiny cubes equipped with two watch motors to power the wheels that enable them to move.
But their collective behaviour is remarkably ant-like.
By being programmed simply to move forward toward a target and avoid obstacles, the robot colony finds the fastest way through a network or maze.
The secret, the researchers report in the open access journal Plos Computational Biology, is in their ability to take cues from one another - just like an insect swarm.
"Each individual robot is pretty dumb," said Simon Garnier from the New Jersey Institute of Technology, lead researcher on the study. "They have very limited memory and limited processing power."
"By themselves, each robot would just move around randomly and get lost... but [they] are able to work together and communicate."
This is because, like ants, the robots leave a trail that the others follow; while ants leave a trail of chemicals - or pheromones - that their nest mates are able to sniff out, the robots leave a trail of light.
Continue reading the main story?Start Quote
End Quote Dr Paul Graham University of SussexYou don't need something as complex as choice to get some of the behaviour you see in ants?
To achieve this, the researchers set up a camera to track the path of each robot. A projector connected to the camera then produced a spot of light at regular intervals along their route, leaving a "breadcrumb trail" of light that got brighter every time another robot tracked over the same path.
Dr Garnier explained: "[The robots each] have two antennae on top, which are light sensors. If more light falls on their left sensor they turn left, and if more light falls on the right sensor, they turn right."
"It's exactly the same mechanism as ants."
The researcher explained how both the robots and ants worked together, describing their navigation skills as a "positive feedback loop".
"If there are two possible paths from A to B and one is twice as long as [the other], at the beginning, the ants [or] robots start using each path equally.
"Because ants taking the shorter path travel faster, the amount of pheromone (or light) deposited on that path grows faster, so more ants use that path."
Learning from nature Continue reading the main storySuperorganisms
- There are an estimated 20,000 species of ants in the world
- Ant colonies have structured social system, with different castes - worker, soldier, queen and drone - all of which carry out specific tasks for the colony
- Ant colonies are sometimes referred to as "superorganisms" because ants appear to operate as a single entity
There are many other research and engineering projects that take inspiration from nature to solve problems or design robots, as Dr Paul Graham, a biologist from the University of Sussex, explained.
"The classic example," he said, "is the way in which we design information networks to move packets of data around.
"Ants don't have someone in charge telling them where to go, so you can [mimic this].
For instance - in a complex network, there may be a junction with different possible routes that packets [of data] could take. Packets would leave messages for each other at the junction to give information about which routes were quick."
This, he explained, is the basis of an algorithm called ant colony optimisation which has already been used in telecoms networks.
And although Dr Graham doesn't see an immediate practical use for these particular robotic insects he says the study demonstrates an important and interesting piece of biology.
"Lots of animal behaviour gets described using words like 'choice'.
"This shows that you don't need something as complex as choice to get some of the behaviour you see in ants.
"And these things look pretty cool, too."
Source: http://www.bbc.co.uk/news/21956795#sa-ns_mchannel=rss&ns_source=PublicRSS20-sa
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Known as the Twitter of China, Sina Weibo is also infamous in the West for the number of high profile users who have had tweets censored, including Kai-fu Lee. The former head of Google China, who was once booted off Sina and Tencent Weibo for three days, recently made a graph of how often his microblogging posts have been censored. Computer scientists Jed Crandall and Dan Wallach conducted a study on how quickly censorship on Sina Weibo can work, with findings reported by the BBC and originally published on arXiv.org. The two researchers, who believe their study is the first “real-time analysis of Weibo posts,” say they “found a landscape in which a post could be deleted as quickly as five minutes after being put online and where the censors appear not to work a regular day, but seem to take a break when China’s all-important 19:00 news comes on.” Censors work rapidly: most deletions happened within the first hour after a post had been made, with about five percent of deletions happening within the first eight minutes, and 30 percent in the first half hour. Nearly 90 percent were made within the first 24 hours. Crandall and Wallach spent 30 days tracking posts by 3,500 users on Sina Weibo. During that time, they write, 300 of the accounts, or 12 percent of the total, were deleted. Accounts that got censored the most often also had posts censored the most quickly, showing that they might be the target of more scrutiny. Though they could not estimate the exact number of people dedicated to deleting posts on Sina Weibo, the two computer scientists said that Sina Weibo would need to employ at least 4,000 censors every day if none of the process was automated. Crandall and Wallach called censorship a “sophisticated operation,” with “relatively sophisticated programmers who build their censorship tooling.” Automated systems appear to include keyword alerts for sensitive topics, as well as monitors for certain users who write frequently about sensitive issues. Launched in 2010, Sina Weibo has 300 million users, with about 100 million messages sent daily.
