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Time plays a key role for all living beings. Their activity is governed by cycles of
different duration which determine their individual and social behavior. Some of these cycles are crucial for their survival. There are biological processes and specific actions which require a precise timing. Some of these actions demand a level of expertise that only can be acquired after a long period of training but others take place spontaneously. How do these actions occur? Possibly through synchronization of individual actions in a population. We also observe similar phenomena in the inanimate world. The Dutch physicist Christian Huygens, whose interest in astronomy led him to investigate precise timekeeping and clock making, was bedridden for a time in 1665 while recovering from an illness. With nothing much to do, he noticed that the pendula of two clocks located near one another swung in unison, the clocks keeping perfect time with one another. When separated, however, the clocks were seen to differ by about five seconds a day.
To explain what he called "an odd kind of sympathy," Huygens speculated that the clocks were interacting through imperceptible movements in the wooden beams supporting the clocks. This video from MIT's McGovern Institute illustrates: to the top right One of the essential benefits of swarm robotic systems is redundancy. In case one robot breaks down, another robot can take steps to repair the failed robot or take over the failed robot's task. Although fault tolerance and robustness to individual failures have often been central arguments in favor of swarm robotic systems, few studies have been dedicated to the subject.
In this study, they show how a group of robots can synchronize based on firefly-inspired flashing behavior and how dead robots can be detected by other robots. The algorithm is completely distributed.
Each robot flashes by lighting up its on-board LEDs and neighboring robots are driven to flash in synchrony. Since robots that are suffering catastrophic failures do not flash periodically, they can be detected by operational robots. |
A swarm of fireflies that start off blinking randomly and eventually begin to flash in unison.
On a real multi-robot system of 10 autonomous robots, we show how the group can correctly detect multiple faults, and that when given (simulated) repair capabilities, the group can survive a relatively high rate of failure. Crickets and frogs communicate with cyclic sound much as fireflies do with cyclic light. In some parts of the country, the night-time soundscape is full of the chirps of crickets and the chorus of frogs croaking. Sometimes these sounds can spontaneously synchronize within a species in a process that is similar to how fireflies synchronize their flashes. Biological synchronization is not limited to insects. The cells that make up the human heart's natural pacemaker, the rhythm keeper that controls the electrical signals that cause the heart to pump, display a propensity for spontaneous synchronization. Each cell can be thought of as an individual oscillator, in much the same way that a firefly can, but with a few key differences. |
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