01-09-2016, 10:21 AM
1451971731-DevelopmentofawallclimbingrobotusingatrackedwheelmechanismKSME3.pdf (Size: 719.98 KB / Downloads: 55)
Abstract
In this paper, a new concept of a wall-climbing robot able to climb a vertical plane is presented. A continuous locomotive
motion with a high climbing speed of 15m/min is realized by adopting a series chain on two tracked wheels on
which 24 suction pads are installed. While each tracked wheel rotates, the suction pads which attach to the vertical
plane are activated in sequence by specially designed mechanical valves. The engineering analysis and detailed mechanism
design of the tracked wheel, including mechanical valves and the overall features, are described in this paper. It is
a self-contained robot in which a vacuum pump and a power supply are integrated and is controlled remotely. The
climbing performance, using the proposed mechanism, is evaluated on a vertical steel plate. Finally, the procedures are
presented for an optimization experiment using Taguchi methodology to maximize vacuum pressure which is a critical
factor for suction force.
Introduction
The application of mobile robots in high places doing
work such as cleaning outer walls of high-rise
buildings, construction work, painting large vessels
and inspecting storage tanks in nuclear power plants
is required because they are currently performed predominantly
by human operators and are extremely
dangerous. For this reason, as a specific research field
of mobile robotics, a number of climbing robots capable
of climbing vertical surfaces have been researched
and developed all over the world [1-4]. Most
climbing robots developed at the present can be classified
into two main functions: locomotion and adhesion.
With an adhesive mechanism, climbing robots
can attach to the wall by using suction force, magnetic
force, micro-spines for interlocking and van der
Waals force. The mechanism using magnetic force is
only available when the climbing environment is composed of a ferromagnetic surface [4].
A robot using a micro-spine is able to attach to
rough surfaces well, but cannot perform on a smooth
surface like glass walls and ceilings [5]. A robot using
van der Waals force mimics a Gecko’s dry adhesion.
This mechanism is novel and it requires no power for
adhesion, but the value of the adhesion force is
greatly affected by surface roughness, so it needs
more research to insure its robustness actually [6].
Suction pads are widely used for industrial purposes
and the most currently applicable and robust compared
to other adhesive mechanisms.
In the case of locomotive mechanisms, they can
generally be divided into legged mechanisms, sliding
mechanisms and tracked wheel mechanisms. The
advantage of the climbing robots employing a legged
mechanism is that they can overcome uneven surfaces
[2, 7]. But, they are comparatively heavy and the
control system is complicated due to the number of
actuators and gait control. These problems result in
low speeds with discontinuous motion. Meanwhile,
the realization of the sliding mechanism is relatively simple in comparison with legged mechanisms, but
its speed is also low due to discontinuous motion [3,
8]. Cleanbot II, developed by Zhu and Sun [1], which
uses a tracked wheel mechanism, can move relatively
fast with continuous motion. It employs a chain-track
on which 52 suction pads are installed and each suction
pad is controlled by a solenoid valve. But this
robot has a large size, with a length of 720 mm, a
width of 370 mm, and a height of 390 mm. It also has
a heavy weight of 22kg, even if a power supply and a
vacuum pump are not included in the robot. Furthermore,
the maximum speed is 8m/min in spite of using
the tracked wheel mechanism.
In this paper, a new concept of a climbing robot
able to climb a vertical wall with continuous motion
is presented. The locomotive motion with a high
climbing speed is realized by adopting a series chain
of two tracked wheels on which 24 suction pads are
installed. Mechanical valves, installed on the robot
instead of solenoid valves to control vacuum supply
into suction pads, contributed to the improvement in
climbing speed. It is a self-contained robot in which a
vacuum pump and a power supply are integrated.
In this paper, the main mechanical structure based
on engineering design [9], a wireless control and
working principle of the tracked wheel mechanism
are described, and then engineering analyses about
the required suction force and the tendency of vacuum
pressure in our system are presented. Experimental
results such as climbing speed and payloads
are described, and then the climbing performance
using the proposed mechanism is verified. Finally, an
optimization experiment to maximize vacuum pressure
and minimize the fluctuation of vacuum pressure
of the suction pads using Taguchi methodology is
presented.