Making robot roaches run into walls

Lessons learned from cockroaches offers a fresh approach to high speed machines. Andrew Masterson reports.

Impact! A robot cockroach smacks into a wall.
Impact! A robot cockroach smacks into a wall.
Kaushik Jayaram

Scientists have invented cockroach-sized robots that can run head first into walls.

And while that might seem at first to be a skill of rather limited value, it may provide a new approach for the design of fast moving robots that enables the rapid transition from horizontal to vertical planes without the need for complicated sensors and actuators.

A team of roboticists led by Kaushik Jayaram from the department of integrative biology at the University of California, Berkeley, in the US, built the wall-hitting robots after being inspired by the behaviour of real cockroaches.

The researchers noted that when a cockroach needs to perform an extreme escape manoeuvre it will often run flat-chat across a floor until it encounters a wall. At this point it will smack into it – making no attempt no lessen the violence of the collision – so that its head functions as a kind of bumper, flipping the insect through 90 degrees so that its feet make contact with the wall. Its escape continues, although now in a different plane.

Jayaram and colleagues noted that this transition happens extremely fast – a roach moving at 50 body lengths per second can flip in just 75 microseconds. It does this by exploiting its robust exoskeleton and its passive body shape: by making no attempt to avoid, dodge or slow down, the cockroach simply lets physics get on with the job.

And this is potentially a very useful trick for roboticists to borrow. Currently, when robots are tasked with making extreme escape manoeuvres, write the researchers in a paper published in the Journal of the Royal Society Interface, “neural control can approach or exceed its operating limits in response time and bandwidth”.

In other words, escape strategies are expensive, taxing and difficult. In part, this is because avoiding obstacles and hazards at high speed and short notice requires a lot of sensors, and a lot of data processing.

Crash or crash through: a robo-roach changes direction through sheer head-on abandon.
Crash or crash through: a robo-roach changes direction through sheer head-on abandon.
Jayaram et al

Cockroaches, in contrast, achieve escape very cheaply: they just run until they hit something, get flipped by the force, then keep running. It is not a thinking operation.

Jayaram’s team decided to see if robots could be designed to mimic the trick. First the researchers filmed 18 captive male cockroaches of the species Periplaneta americana barrelling down a specially built track with a vertical wall at one end.

Next, they constructed a number of basic palm-sized six-legged robots and made them do the same thing. To determine the optimum force with which the machines needed to hit the wall, the scientists first suspended dead cockroaches, using thin wire, and made them swing like pendulums, colliding with a brass paperweight. By filming the results, it was possible to determine the best impact speed.

To manage the plane transition, the robot roaches had to be fitted with a cone-shaped cardboard “nose” – an analogue of a real cockroach head. Thus kitted out, the experiment was a success.

Jayaram and his colleagues call the result a “paradigm shift” in robotics. They say that by relying on the mechanics of the body rather than sensor-based controls make robots (and animals) much more robust under extreme conditions.

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Andrew Masterson is news editor of Cosmos.
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