ROOM
54
Astronautics
future human and robotic missions to Mars, the
lunar vicinity is a key area for the development of
an affordable and sustainable space economy that
would completely transform the current landscape
of space exploration [2].
High-speed lunar rover
Successful robotic systems currently operating
on the surface of Mars, such as the Mars Science
Laboratory ‘Curiosity’ and the ‘Opportunity’ Mars
Exploration Rover, were provided with locomotion
systems all designed based on the same principles: a
six-wheel, self-propelled chassis with a rocker-bogie
type of suspension system.
Despite the difference in weight (185 kg for
Opportunity and 899 kg for Curiosity) and the
use of a slightly different version of the rocker-
bogie suspension (differential for Opportunity
and hinged-lever for Curiosity) the properties
that characterise the performance of both robotic
systems are very similar [3].
Rocker-bogie suspension systems have proved
to be simple and highly reliable when traversing
rough and uneven terrains without compromising
overall stability. However, some important
limitations can be found with regards to its
mobility and locomotive performance, such as the
maximum traverse speed that a rover is capable
of attaining.
Mobility could be defined in broad terms as
the capacity of a rover to traverse between two
distance points of an uncharted or unprepared
region [3]. This capacity is merely characterised
by the relief and the variation of the physical
properties of the terrain [4].
Current rover designs are not suited for
accomplishing many of the goals envisaged in
future exploration missions [5]. Aspects such as
the uneven distribution of torques between the
wheels, the maximum operational speed (i.e.,
2.5 cm/s for Curiosity and 5 cm/s for the Mars
Exploration Rovers, Spirit and Opportunity), and
the issues experienced by several rovers on past
and present exploration missions (mainly related to
skidding, which causes the sinking of the wheels)
raised the need to develop the mechanics of a future
generation of planetary rovers.
As part of our mission at the Space Robotics
Lab we are developing a locomotive system for
an improved mobility rover. This includes the
mechanical design of the suspension, wheels and
drive systems together with the improvement of
mobility-related control algorithms. In addition
to the mechanics of the locomotive system, other
aspects related to the navigational ability of a rover,
such as path planning, sensing and localisation, have
a direct influence on the overall performance of
planetary robots.
Our work is oriented towards the design of the
mechanics and the development of traction control
algorithms for a lunar prospecting rover intended
for the exploration and characterisation of the lunar
south polar region. Due to limited illumination,
irregular topography together with the need to avoid
the use of radioisotope thermal heaters, a long-
range, high-speed prospecting rover is required.
Current rover
designs are
not suited for
accomplishing
many of
the goals
envisaged
in future
exploration
missions
Artist’s concept of a
future lunar habitation.
ESA
