Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Investigation on a bipedal robot: Why do humans need both Soleus
  andGastrocnemius muscles for ankle push-off during walking?   Legged locomotion in humans is influenced by mechanics and neural control.
One mechanism assumed to contribute to the high efficiency of human walking is
the impulsive ankle push-off, which potentially powers the human swing leg
catapult. However, the mechanics of the human's lower leg with its complex
muscle-tendon units spanning over single and multiple joints is not yet
understood. Legged robots allow testing the interaction between complex leg
mechanics, control, and environment in real-world walking gait. We custom
developed a small, 2.2 kg human-like bipedal robot with soleus and
gastrocnemius muscles represented by linear springs, acting as mono- and
biarticular elasticities around the robot's ankle and knee joints. We tested
the influence of three soleus and gastrocnemius spring configurations on the
ankle power curves, on the synchronization of the ankle and knee joint
movements, on the total cost of transport, and on walking speed. We controlled
the robot with a feed-forward central pattern generator, leading to walking
speeds between 0.35 m/s and 0.57 m/s at 1.0 Hz locomotion frequency, at 0.35 m
leg length. We found differences between all three configurations; the soleus
spring supports the robot's speed and energy efficiency by ankle power
amplification, while the GAS spring facilitates the synchronization between
knee and ankle joints during push-off.

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The categories of this paper are: atom-ph
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: gr-qc
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
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The categories of this paper are: math
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The categories of this paper are: stat
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th