Entomological Engineering

Eoin Dillon

The mechanical marvels of insects, and what we can learn from them.

 

Insects have been crawling and flying around the Earth since they evolved in the Ordovician period 480 million years ago (1). In this time they have perfected various means of survival and natural selection has molded them into thousands of diverse morphologies. However it is only in recent years that we humans have begun to turn towards our 6-legged friends for inspiration in designing robotics with a range of uses from space exploration to searching for survivors after earthquakes. Here I will outline some of the ground-breaking research engineers are carrying out with inspiration from insects.

Space Exploration

Insects are characterised by their 3 pairs of legs stemming from their thoracic segments, but it isn’t by chance that 6 is the magic number when dealing with insect legs. The way the legs are arranged allow for amazing co-ordination and dexterity no matter the speed they are travelling at. At low speeds an insect will lift one leg at a time, leaving the other 5 stationary. At intermediate speeds the insects adopt what’s known as a metachronal gait. Here the insect first lifts its hind leg forward on one side, followed by the middle and then the fore leg then alternates between the right and left sides (2). Finally, at their top speeds insects use a tripod gait, here three legs remain in contact with the ground at all time and push the insect forward while the other three are lifted. The legs that stay in contact with the ground form a tripod shape, from which the name is derived. Two legs on one side (Fore and hind legs) of the insect will stay down, and one on the opposite side(middle leg), and then they alternate (3). By switching between the three states depending on what’s needed insects can ensure their centre of balance is always stable.

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The Tripod Gait

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The 6-legged mechanism of locomotion has recently been an inspiration for engineers in China who plan on designing robots with 6 legs used to fetch samples from asteroids. These ant-like robots can traverse the uneven surface of asteroids much more successfully than rolling machines like the Mars Rover (4). Whether or not the machines will be built to reflect the complexity of movement insects can perform remains to be seen.

Roach Robots to the Rescue

Although hated almost universally by people (I personally love them), it seems that cockroaches offer a unique new perspective on building small robots used to find survivors in rubble after a catastrophe such as an earthquake or a mine collapse. Researchers at the University of California, Berkeley have designed a robot with an assemblage of cockroach characteristics capable of squeezing through cracks while remaining durable. Their work took inspiration from the American cockroach (Periplaneta americana) which was chosen due to its high speeds, robustness, maneuverability and its tenacity to enter and leave spaces.

Cockroach squeezing
Depiction of P. americana’s changes in height while squeezing through tight spaces

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So, what makes cockroaches so good at what they do. Their hard exoskeleton is arranged in a series of overlapping plates, this allows for maximum flexibility and durability. American cockroaches can squeeze through spaces less than a quarter of their height and are also capable of withstanding weight 900 times their own without getting hurt (5).The most amazing part of this flexible exoskeleton is their movement while squeezing through tight spaces. A locomotive process called ‘body friction legged crawling’ which allows the roaches to run at 20 body lengths per second. Even though the legs can’t move properly when confined, special sensory leg spines push against the floor allowing movement. By designing a robot with a flexible spine and a series of overlapping plates on the dorsal side Robert Full and Kaushik Jayaram of UC Berkeley successfully imitated the roach’s amazing abilities (6).

RoboRoach
U. C. Berkeley’s robot cockroach next to the real thing

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Reach for the Sky

It is believed that insects first took to the skies 400 million years ago (1), well before the other flying animals (birds and bats) even began to develop flight. For a long time the aerodynamic principles governing insects flight was unknown, but now humans have a fair understanding of how insects wings work. To generate lift many insects use what’s known as the “clap-and-fling effect” whereby the fore and hind wings initially clap together in flight then peel apart which creates a low pressure air pocket. As air rushes into the low pressure area lift is generated to keep the insect in the air (7).

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The RoboBee next to a US penny

 

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By applying the principles found in insects wings, the hope is to create drones much more resilient than those around today. The problem with rotor-drones is that collisions and strong wind gusts can be detrimental, and recovering in mid air is very difficult. Using wings instead of rotors would allow enough maneuverability to travel through enclosed spaces such as buildings, as well as a means to dodge obstacles. Inspired by bees, researchers from the Wyss Institute, Harvard’s School of Engineering and Applied Sciences (SEAS) and Northeastern University have designed RoboBees weighing less than 0.1 gram and half the size of a paperclip. These robots have wings which are controlled independently and have an array of sensors to mimic the eyes and antennae of bees. Potential applications for these mechanical insects include crop pollination, traffic monitoring, search-and-rescue missions and surveillance to name but a few (8).

As we move on into the future of technology, it is my belief that more and more engineers will find their muse and inspiration from natural examples which have millions of years of evolution behind them. And no other natural source is as varied, or as awe-inspiring than those found right beneath our feet, every day in the insect world.

 

References

  1. https://www.sciencedaily.com/releases/2014/11/141106143709.htm
  2. Akimoto, K., Watanabe, S. and Yano, M. (1999). An insect robot controlled by the emergence of gait patterns. Artif Life Robotics, 3(2), pp.102-105.
  3. Cranston, P. and Gullan, P. (2010). The insects. Chichester: Wiley-Blackwell.
  4. http://news.xinhuanet.com/english/2015-10/15/c_134716387.htm
  5. http://www.wired.com/2016/02/cockroaches-squish-their-way-into-rescue-robotics/
  6. Jayaram, K. and Full, R. (2016). Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot. Proceedings of the National Academy of Sciences, 113(8), pp.E950-E957.
  7. Weis-Fogh, T. (1975). Unusual Mechanisms for the Generation of Lift in Flying Animals. Sci Am, 233(5), pp.80-87.
  8. http://wyss.harvard.edu/viewpage/457
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