Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

232 Chapter 9 Comparing Locomotion Methods
THE ENVIRONMENT
Moving around in the relatively benign indoor environment is a simple
matter, with the notable exception of staircases. The systems in this book
mostly focus on systems designed for the unpredictable and highly varied
outdoor environment, an environment that includes large variations in
temperature, ground cover, topography, and obstacles. This environment
is so varied, that only a small percentage of the problems can be listed, or
the number of comparison parameters would become much too large.
Hot and cold may not seem related to mobility, but they are in that the
mobility system must be efficient so it doesn’t create too much heat and
damage itself or nearby components when operating in a desert. The
mobility system must not freeze up or jam from ice when operating in
loose snow or freezing rain. As for ground cover, the mobility system
might have to deal with loose dry sand, which can get everywhere and
rapidly wear out bearings, or operate in muddy water. It might also have
to deal with problematic topography like steep hills, seemingly impassable
nearly vertical cliffs, chasms, swamps, streams, or small rivers. The
mobility system will almost definitely have to travel over some or all of
those topographical challenges. In addition, there are the more obvious
obstacles like rocks, logs, curbs, pot holes, random bumps, stone or concrete
walls, railroad rails, up and down staircases, tall wet grass, and
dense forests of standing and fallen trees.
This means that the mobility system’s effectiveness should be evaluated
using the aforementioned parameters. How does it handle sand or
pebbles? Is its design inherently difficult to seal against water? How
steep an incline can it negotiate? How high an obstacle, step, or bump
can it get over or onto? How wide a chasm can it cross? Somehow, all
these need to be simplified to reduce the wide variety down to a manageable
few.
The four categories of temperature, ground cover, topography, and
obstacles can be either defined clearly or broken up into smaller more
easily defined subcategories without ending up with an unmanageably
large list. Let’s look at each one in greater detail.
Thermal
Temperature can be divided simply into the two extremes of hot and
cold. Hot relates to efficiency. A more efficient machine will have fewer
problems in hot climates, but better efficiency, more importantly, means
battery powered robots will run longer. Cold relates to pinch points,