11-05-2012, 10:49 AM
A SIMPLE ARCHITECTURE FOR IN-PIPE INSPECTION ROBOTS
A SIMPLE ARCHITECTURE FOR IN.doc (Size: 38.5 KB / Downloads: 52)
Abstract
The paper presents an original robot architecture for in-pipe inspection. The
robot consists of two parts articulated with a universal joint. One part is guided along the
pipe by a set of wheels moving parallel to the axis of the pipe, while the other part is
forced to follow an helical motion thanks to tilted wheels rotating about the axis of the
pipe. A single motor is placed between the two bodies to produce the motion. All the
wheels are mounted on a suspension to accommodate for changing tube diameter and
curves in the pipe. The robot is autonomous and carries its own batteries and radio link.
Four different prototypes have been constructed for pipe diameters of 170, 70 and 40
mm, respectively. For smaller diameters, the batteries and the radio receiver may be
placed on an additional body attached to the others. The autonomy of the prototypes is
about 2 hours. This architecture is very simple and the rotary motion can be exploited to
carry out scrubbing or inspection tasks.
Keywords: Autonomous mobile robot, In-pipe inspection, Helical motion
Introduction
Pipe inspection robots have been studied for a long time, and many original locomotion concepts have
been proposed to solve the numerous technical difficulties associated with the change in pipe
diameter, curves and energy supply. Although an exhaustive review of the literature is impossible due
to the limited space available, a few broad categories can be identified:
(i) For small size, many projects follow the earthworm principle consisting of a central part
moving axially while the two end parts are provided with blocking devices connected
temporarily to the pipe. Pneumatic versions of this concept have been proposed (e.g. [1]),
but they require an umbilical for power. For smaller diameter (10 mm or less), a
piezoelectric actuation has been considered, according to the inchworm principle, or
according to an inertial locomotion driven by a saw-tooth wave voltage [2], or using
vibrating fins with differential friction coefficients [3].
(ii) For medium size piping, classical electromechanical systems have been proposed with
various architectures involving wheels and tracks, with more or less complicated
kinematical structures, depending on the diameter adaptability and turning capability (e.g.
[4,5]).
(iii) For large pipes, walking tube crawlers have also been proposed [6].
The four mobile robots presented in this paper belong to the second category, they span a tube
diameter from 40 to 170 mm. The design results from an attempt to reduce the electromechanical
complexity through the use of a single actuator to achieve mobility along the tube. Although our study
can be regarded as an independent effort, it appears that the “spiral wheel” strategy was explored
before [7].
Architecture
The robot consists of two main parts, a stator and rotor, connected by an active joint including a D.C.
motor with reducer and, in some cases, a universal joint. The stator is equipped with a set of wheels
which allow the motion parallel to the tube axis; the rotor is equipped with wheels tilted with a small
angle with respect to the plane perpendicular to the tube axis (Fig. 1. a). In this way, the stator is
constrained to move along the tube axis while the wheels of the rotor can only move along helical
trajectories, and the rotation of the rotor with respect to the stator generates the axial motion.