Page 56 - Modern Robotics Building Versatile Macines

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LEARNING TO WALK

MARC RAIBERT AND ROBOTS WITH LEGS

any robots in science fiction movies walk like people, striding
Malong confidently. But most real-world mobile robots (such as
those that deliver prescriptions in hospitals) roll along on wheels.
It is not easy to get a robot to master walking, a skill that humans
learn as toddlers. But there are some very good reasons to make
robots that can walk or run.
In a 1986 article for Communications of the ACM, the journal of
the Association for Computing Machinery, robotics engineer Marc
Raibert pointed out:

There is a need for vehicles that can travel in difficult terrain, where
existing vehicles cannot go. Wheels excel on prepared surfaces such as
rails and roads, but perform poorly where the terrain is soft or uneven.
Because of these limitations, only about half the earth’s landmass is acces-
sible to existing wheeled and tracked vehicles, whereas a much greater
area can be reached by animals on foot. It should be possible to build
legged vehicles that can go to the places that animals can now reach.

Raibert went to explain a key reason why legs can be better than
wheels:

One reason legs provide better mobility in rough terrain is that they
can use isolated footholds that optimize support and traction, whereas
a wheel requires a continuous path of support. As a consequence, a

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