A walking robot that switches gaits

Even simple insects can generate quite different movement patterns with their six legs. The animal uses various gaits (manner of walking)depending on whether it crawls uphill or downhill, slowly or fast. Scientists from Gottingen have now developed a walking robot, which depending on the situation 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.” This interdisciplinary work was carried out by a team of scientists at the Bernstein Center for Computational Neuroscience Gottingen, the Physics Department of the Georg-August-University of Gottingen and the Max Planck Institute for Dynamics and Self-Organization.

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 robot receives information about its environment via several sensors — 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.

One single pattern generator for many gaits.

The robot developed by the Gottingen 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.

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.”

(Courtesy: Science Daily)

World's highest airport in Tibet?

China is to build the world's highest airport, at an altitude of 4,436 metres (14,500ft), in Tibet. The construction, at Nagqu, is likely to be a daunting task given the altitude and climate, with average temperatures staying below zero throughout the year.The airport will be just 764 metres lower than the Mount Everest base camp

on the Chinese side, which is located 5,200 metres above sea level.Nagqu is in the centre of the Qinghai-Tibet plateau, about 186 miles from the Tibetan capital of Lhasa, with a population of 400,000.

The airport will be the sixth in Tibet, and its addition means there will be one airport in each prefecture."The airport construction is planned for 2011 with a construction period of three years," said Xu Jian, director of the Nagqu committee of development and reform.

"It is expected to cost 1.8bn yuan [£160m] and cover an area of 233-266 hectares."China announced in 2008 that it would build 97 new airports by 2020, so that four-fifths of the population would be within a 90-minute drive of an airport."With the airport, Nagqu, which is also on the Qinghai-Tibet railway line, is expected to become the centre of an economic hub in the plateau region," said Tan Yongshou, commissioner of the prefecture.Xu Bo, director of the Tibetan branch of the China civil aviation administration, added: " The objective for the next stage of development is to open direct air routes from Tibet to south Asian countries."The new airport will beat the current altitude record holder “ Bamda airport in Bangda, Qamdo, which, also in Tibet, sits at an elevation of 4,334 metres.

That airport overtook the one at Lhasa, which has been built at a mere 3,600 metres.The plans underline the astonishing speed with which China is unrolling ­ambitious infrastructure projects, often under challenging conditions, and, in particular, highlights the rapid development occurring in Tibet.An extraordinary railway line connecting Tibet to the rest of China opened four years ago, and the government is constructing six new rail lines in and around the vast region, which is rich in natural resources.Beijing argues that such changes are needed to boost growth and raise living standards.

Courtesy:-AFP