Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Designing an Inertia Actuator with a Fast Rotating Gyro inside an
  Egg-shaped Robot   In this paper, we describe features of two new robot prototypes that are
actuated by an actively controlled gyro (flywheel, symmetric rotor) inside a
hollow sphere that is located in the middle of the robots. No external
actuators are used. The outside structure of the robots and the gyro are
connected by a gimbal, which is similar in structure to a control moment
gyroscope in spacecrafts. The joints of the gimbal can be actuated. In this
way, the orientation of axis for the gyro in relation to the egg can be
changed. Since the inertia of the fast rotating gyro is large in relation to
the outside structure, a relative rotation of the axis against the outside
structure results in a motion of the egg by inertia principle. In this way, we
can use this principle for controlling the robot to move forward and turn
around. The robots are shaped as spheroidal ellipsoids so they resemble eggs.
So far, we have built and tested two robot prototypes.

34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph