A Robot That Runs Like a Cat

A Robot That Runs Like a Cat

  8:22:00 AM    Science Lover

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Thanks to its legs, whose design faithfully reproduces feline morphology, EPFL's four-legged "cheetah-cub robot" has the same advantages as its model: it is small, light and fast. Still in its experimental stage, the robot will serve as a platform for research in locomotion and biomechanics.

This is cheetah-cub, a compliant quadruped robot.
(Credit: (c) EPFL)

Even though it doesn't have a head, you can still tell what kind of animal it is: the robot is definitely modeled upon a cat. Developed by EPFL's Biorobotics Laboratory (Biorob), the "cheetah-cub robot," a small-size quadruped prototype robot, is described in an article appearing today in the International Journal of Robotics Research. The purpose of the platform is to encourage research in biomechanics; its particularity is the design of its legs, which make it very fast and stable. Robots developed from this concept could eventually be used in search and rescue missions or for exploration.

This robot is the fastest in its category, namely in normalized speed for small quadruped robots under 30Kg. During tests, it demonstrated its ability to run nearly seven times its body length in one second. Although not as agile as a real cat, it still has excellent auto-stabilization characteristics when running at full speed or over a course that included disturbances such as small steps. In addition, the robot is extremely light, compact, and robust and can be easily assembled from materials that are inexpensive and readily available. 

Faithful reproduction

The machine's strengths all reside in the design of its legs. The researchers developed a new model with this robot, one that is based on the meticulous observation and faithful reproduction of the feline leg. The number of segments -- three on each leg -- and their proportions are the same as they are on a cat. Springs are used to reproduce tendons, and actuators -- small motors that convert energy into movement -- are used to replace the muscles.

"This morphology gives the robot the mechanical properties from which cats benefit, that's to say a marked running ability and elasticity in the right spots, to ensure stability," explains Alexander Sprowitz, a Biorob scientist. "The robot is thus naturally more autonomous."

Sized for a search

According to Biorob director Auke Ijspeert, this invention is the logical follow-up of research the lab has done into locomotion that included a salamander robot and a lamprey robot. "It's still in the experimental stages, but the long-term goal of the cheetah-cub robot is to be able to develop fast, agile, ground-hugging machines for use in exploration, for example for search and rescue in natural disaster situations. Studying and using the principles of the animal kingdom to develop new solutions for use in robots is the essence of our research."

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Engineered Robot Interacts With Live FishEngineered Robot Interacts With Live Fish

Engineered Robot Interacts With Live FishEngineered Robot Interacts With Live Fish

  3:22:00 PM    Science Lover

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A bioinspired robot has provided the first experimental evidence that live zebrafish can be influenced by engineered robots.

A robotic zebrafish. 
(Credit: Image courtesy of Institute of Physics)

Results published 8 June in IOP Publishing's journal Bioinspiration and Biomimetics, provide a stepping stone on the path to using autonomous robots in an open environment to monitor and control fish behaviour.

In the future, water-based robots could potentially contribute to the protection of endangered animals and the control of pest species.

The robot, created by researchers from Polytechnic Institute of New York University and Instituto Superiore di Sanitá, Italy, was 15 centimetres long and spray-painted with the characteristic blue stripes of the zebrafish. The tail of the robot was mechanically controlled by the researchers to mimic the action of the zebrafish itself.

When placed in a 65 litre fish tank, the movements of the robot's tail attracted both individual and shoals of zebrafish; the researchers believe that such capability was influenced by its bioinspired features which were optimised to increase attraction.

For example, the robot was given a rounder shape to mimic a fertile female, which is preferred by both male and female zebrafish, and its colour pattern -- a magnified stripe width and saturated yellow pigment -- emphasized distinctive biologically relevant features.

The robot was in a fixed position in the tank so that the tail movements could be controlled, recorded and, most importantly, associated with the behaviour of the zebrafish.

The fish tank where the experiments took place was divided into one large middle section and two smaller sections at either end, separated by transparent Plexiglas. A total of 16 experiments were performed in which individual, and then shoals of, zebrafish were placed in the middle compartment of the tank and two stimuli were placed at either end behind the Plexiglass.

The combinations of stimuli were: one fish versus an empty space; ten fish versus an empty space; ten fish versus one fish; the robot versus an empty space, and the robot versus one fish.

A camera was placed above the tank to monitor the movements of the zebrafish, and statistical tests were performed to calculate whether the robot acted as an attractive, neutral or aversive stimulus and whether this relationship depends on the fish being isolated or in a shoal.

Although the live zebrafish tended to prefer each other to the robot, when given the choice to spend time next to the robotic fish or an empty space, both the individual fish and shoal of fish preferred the robot. While the noise of the robot's motor was shown to decrease its attraction, the actual beating of the tail emphasized its attractiveness.

The corresponding author, Dr Maurizio Porfiri, said: "These findings provide practical evidence that a species' preference for conspecifics may be used to inspire the design of robots which can actively engage their source of inspiration.

"New studies are currently underway in our lab investigating the interactions between fish and robotic fish when they are free to swim together under controlled and ecologically complex conditions."

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