Organized chaos gets robots going (Update)

Jan 17, 2010
Following the principle of chaos control, the robot produces regular leg movements when walking normally. In addition, it can use the uncontrolled chaotic movement pattern to free itself when its leg is trapped in a hole. Image: Network Dynamics Group, Max Planck Institute for Dynamics and Self-Organization

(PhysOrg.com) -- Even simple insects can generate quite different movement patterns with their six legs. The animal uses various gaits depending on whether it crawls uphill or downhill, slowly or fast. Scientists from Gottingen have now developed a walking robot, which can flexibly and autonomously switch between different gaits. The success of their solution lies in its simplicity: a small and simple network with just a few connections can create very diverse movement patterns. To this end, the robot uses a mechanism for "chaos control."

In humans and animals, periodically recurring movements like walking or breathing are controlled by small neural circuits called "central pattern generators" (CPG). Scientists have been using this principle in the development of walking machines. To date, typically one separate CPG was needed for every gait. The receives information about its environment via several - about whether there is an obstacle in front of it or whether it climbs a slope. Based on this information, it selects the CPG controlling the gait that is appropriate for the respective situation.

This video is not supported by your browser at this time.
Movie: Escaping from danger from behind, orienting and self-protection

The robot developed by the Göttingen scientists now manages the same task with only one CPG that generates entirely different gaits and which can switch between these gaits in a flexible manner. This CPG is a tiny network consisting of two circuit elements. The secret of its functioning lies in the so-called "chaos control". If uncontrolled, the CPG produces a chaotic activity pattern. This activity, however, can very easily be controlled by the sensor inputs into periodic patterns that determine the gait. Depending on the sensory input signal, different patterns - and thus different gaits - are generated.

The connection between sensory properties and CPG can either be preprogrammed or learned by the robot from experience. The scientists use a key example to show how this works: the robot can autonomously learn to walk up a slope with as little energy input as possible. As soon as the robot reaches a slope, a sensor shows that the energy consumption is too high. Thereupon, the connection between the sensor and the control input of the CPG is varied until a gait is found that allows the robot to consume less energy. Once the right connections have been established, the robot has learned the relation between slope and gait. When it tries to climb the hill a second time, it will immediately adopt the appropriate gait.

This video is not supported by your browser at this time.
Movie: Robot exploits chaos for self-untrapping.

In the future, the robot will also be equipped with a memory device which will enable it to complete movements even after the sensory input ceases to exist. In order to walk over an obstacle, for instance, the robot would have to take a large step with each of its six legs. "Currently, the robot would not be able to handle this task - as soon as the obstacle is out of sight, it no longer knows which gait to use," says Marc Timme, scientist at the Max Planck Institute for Dynamics and Self-Organization. "Once the robot is equipped with a motor memory, it will be capable to use foresight and plan its movements".

Explore further: New method for non-invasive prostate cancer screening

More information: Silke Steingrube, Marc Timme, Florentin Wörgötter and Poramate Manoonpong, Self-organized adaptation of a simple neural circuit enables complex robot behaviour , Nature Physics, January 17th, 2010 (DOI: 10.1038/NPHYS1508)

Related Stories

Monkey's Thoughts Make Robot Walk from Across the Globe

Jan 17, 2008

In a first-of-its-kind experiment, the brain activity of a monkey has been used to control the real-time walking patterns of a robot halfway around the world, according to researchers at Duke University Medical Center.

New robot skier takes to the slopes (w/ Video)

Oct 23, 2009

(PhysOrg.com) -- A new robot skier has been invented that can be fitted with off-the-shelf skis. This is not the first skiing robot, since Japanese scientists have produced their own (see PhysOrg.com article here), but is bigger and heavie ...

Underwater robot with a sense of touch

May 04, 2009

(PhysOrg.com) -- Maintenance of offshore drilling rigs or underwater cables, taking samples of sediment - underwater robots perform a variety of deep-sea tasks. Research scientists now aim to equip robots ...

iPhone Software That Controls Robot Movements (w/ Video)

Nov 18, 2009

(PhysOrg.com) -- At the graduate school of media design at Keio University in Tokyo, a project called "Walky" is under developed. Researchers have developed specifically designed software for the iPhone that ...

Recommended for you

New method for non-invasive prostate cancer screening

4 hours ago

Cancer screening is a critical approach for preventing cancer deaths because cases caught early are often more treatable. But while there are already existing ways to screen for different types of cancer, ...

How bubble studies benefit science and engineering

5 hours ago

The image above shows a perfect bubble imploding in weightlessness. This bubble, and many like it, are produced by the researchers from the École Polytechnique Fédérale de Lausanne in Switzerland. What ...

Famous Feynman lectures put online with free access

6 hours ago

(Phys.org) —Back in the early sixties, physicist Richard Feynman gave a series of lectures on physics to first year students at Caltech—those lectures were subsequently put into print and made into text ...

Single laser stops molecular tumbling motion instantly

10 hours ago

In the quantum world, making the simple atom behave is one thing, but making the more complex molecule behave is another story. Now Northwestern University scientists have figured out an elegant way to stop a molecule from ...

User comments : 0