Page 45 - Introduction to Autonomous Mobile Robots

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Figure 2.18 Chapter 2
Genghis, one of the most famous walking robots from MIT, uses hobby servomotors as its actuators
(http://www.ai.mit.edu/projects/genghis). © MIT AI Lab.

structures, such as microscopic barbs and textured pads, that increase the gripping strength
of each leg significantly. Robotic research into such passive tip structures has only recently
begun. For example, a research group is attempting to re-create the complete mechanical
function of the cockroach leg [65].
It is clear from the above examples that legged robots have much progress to make
before they are competitive with their biological equivalents. Nevertheless, significant
gains have been realized recently, primarily due to advances in motor design. Creating
actuation systems that approach the efficiency of animal muscles remains far from the
reach of robotics, as does energy storage with the energy densities found in organic life
forms.

2.3 Wheeled Mobile Robots

The wheel has been by far the most popular locomotion mechanism in mobile robotics and
in man-made vehicles in general. It can achieve very good efficiencies, as demonstrated in
figure 2.3, and does so with a relatively simple mechanical implementation.
In addition, balance is not usually a research problem in wheeled robot designs, because
wheeled robots are almost always designed so that all wheels are in ground contact at all
times. Thus, three wheels are sufficient to guarantee stable balance, although, as we shall
see below, two-wheeled robots can also be stable. When more than three wheels are used,
a suspension system is required to allow all wheels to maintain ground contact when the
robot encounters uneven terrain.
Instead of worrying about balance, wheeled robot research tends to focus on the prob-
lems of traction and stability, maneuverability, and control: can the robot wheels provide