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Hopping robots can conserve energy: Study

Last Updated: Sunday, November 4, 2012 - 16:54

Washington: Scientists have discovered that hopping robots can reduce the amount of energy they use by adopting a unique two-part "stutter jump", a finding that can extend the range of robotic rescue and exploration missions.

Taking a short hop before a big jump could allow spring-based "pogo-stick" robots to reduce their power consumption as much as ten-fold, found research from the Georgia Institute of Technology.

The formula for the two-part jump was discovered by analysing nearly 20,000 jumps made by a simple laboratory robot under a wide range of conditions.

"If we time things right, the robot can jump with a tenth of the power required to jump to the same height under other conditions," said Daniel Goldman, an assistant professor in the School of Physics at the Georgia Institute of Technology.

"In the stutter jumps, we can move the mass at a lower frequency to get off the ground. We achieve the same takeoff velocity as a conventional jump, but it is developed over a longer period of time with much less power," Goldman said.

Jumping is an important means of locomotion for animals, and could be important to future generations of robots. Jumping has been extensively studied in biological organisms, which use stretched tendons to store energy.

Researchers built a simple one-kilogramme robot that composed a spring beneath a mass capable of moving up and down on a thrust rod.

They used computer controls to vary the starting position of the mass on the rod, the amplitude of the motion, the pattern of movement and the frequency of movement applied by an actuator built into the robot`s mass.

Researchers expected to find that the optimal jumping frequency would be related to the resonant frequency of the spring and mass system, but that turned out not to be true.

Detailed evaluation of the jumps showed that frequencies above and below the resonance provided optimal jumping - and additional analysis revealed what the researchers called the "stutter jump".

The amount of energy that can be stored in batteries can limit the range and duration of robotic missions, so the stutter jump could be helpful for small robots that have limited power.

Optimising the efficiency of jumping could therefore allow the robots to complete longer and more complex missions. But because it requires longer to perform than a simple jump, the two-step jump may not be suitable for all conditions.

"If you`re a small robot and you want to jump over an obstacle, you could save energy by using the stutter jump even though that would take longer. But if a hazard is threatening, you may need to expend the additional energy to make a quick jump to get out of the way," Goldman said in a statement.

The research was published in the journal Physical Review Letters.


First Published: Sunday, November 4, 2012 - 16:54
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