25-05-2012, 12:39 PM
Swimming and Crawling with an Amphibious Snake Robot
Swimming and Crawling with an Amphibious Snake Robot.pdf (Size: 231.43 KB / Downloads: 59)
INTRODUCTION
The aim of this project is to build a biologically inspired
amphibious snake-like robot, called AmphiBot I. The goals
of the project are three-fold: (1) to build an amphibious
robot for outdoor robotics tasks, taking inspiration from
snakes and elongate fishes such as lampreys, (2) to use the
robot as a test-bed for novel types of adaptive controllers
based on the concept of central pattern generators [1],
and (3) to use the robot to investigate hypotheses of how
locomotion-controlling neural networks are implemented in
real animals.
Such a robot can have multiple applications. On one
hand, as mentioned before, it can be used to test neurobiological
hypotheses about the structure of the neural
networks controlling locomotion in fishes and snakes. On
the other hand, the form of an amphibious snake-like
robot, its locomotion capabilities and its ability to deal
with multiple kinds of environments (including difficult
ones) make it well-suited for inspection and exploration
tasks (e.g. in areas not easily accessible by humans, such
as pipes), and for the participation to search and rescue
missions (e.g. under a collapsed building or in a flooded
zone).
RELATED WORKS
Snake-like robots are not a recent invention: Hirose
and colleagues built in 1972 a robot that is probably the
first snake robot [2], generically naming it an active cord
mechanism (ACM). Some other snake robots have been
built by the same group [3]. A very big snake robot has
been developed at Caltech in 1992 [4]. In 1994 the NASA
Jet Propulsion Laboratory presented a serpentine robot [5].
Miller developed several snake robots prototypes; the last
one, named S5 [6], has a very realistic locomotion. In 2002
Saito and colleagues presented a simple snake robot they
used to validate theoretical results [7]. In 2003, Conradt
developed WormBot [8], a snake-like robot controlled by
local CPGs. For a more detailed review of snake robots
(including those with powered wheels, not considered
here), see [9] and [10].
LOCOMOTION CHARACTERIZATION
In order to test the locomotor abilities of the robot, we
tested it using a range of different sine-based undulations.
The parameters characterizing the sinusoidal crawling or
swimming gaits are the amplitude A, the frequency ν and
the phase lag Δφ.
RESULTS
A. Swimming
Swimming results are presented in Figures 4(a) and
5(a) for ν = 0.25 Hz and ν = 0.5 Hz. The results for
ν = 0.75 Hz are not included, because we found out that
the torque requirements for undulations with large amplitudes
exceed our motor capabilities (i.e. actual trajectories
1The parameters used in these snapshots are not optimal but only near
the optimum. The snapshots with the optimal gait have not been realized
for technical reasons.