Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Improved Performance on Moving-Mass Hopping Robots with Parallel
  Elasticity   Robotic Hopping is challenging from the perspective of both modeling the
dynamics as well as the mechanical design due to the short period of ground
contact in which to actuate on the world. Previous work has demonstrated stable
hopping on a moving-mass robot, wherein a single spring was utilized below the
body of the robot. This paper finds that the addition of a spring in parallel
to the actuator greatly improves the performance of moving mass hopping robots.
This is demonstrated through the design of a novel one-dimensional hopping
robot. For this robot, a rigorous trajectory optimization method is developed
using hybrid systems models with experimentally tuned parameters. Simulation
results are used to study the effects of a parallel spring on energetic
efficiency, stability and hopping effort. We find that the double-spring model
had 2.5x better energy efficiency than the single-spring model, and was able to
hop using 40% less peak force from the actuator. Furthermore, the double-spring
model produces stable hopping without the need for stabilizing controllers.
These concepts are demonstrated experimentally on a novel hopping robot,
wherein hop heights up to 40cm were achieved.

15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio