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184 Biomimetics: Biologically Inspired Technologies

Figure 6.4 Whegs II of Case Western Reserve University.

around sharp bends, over refuse, and up stairs. Most other sewer robots are tethered by power and
control cables and navigate uni-directionally. The wireless, waterproof, and two-headed MAKRO,
however, can autonomously navigate bi-directionally, monitoring its own position, detecting sewer
landmarks, and enacting mission tasks, such as taking sewage samples.
Case Western Reserve University robot Whegs II combines wheels and legs, words that contract
to spell ‘‘whegs,’’ now a trademarked word for wheel–leg combinations (see Figure 6.4). In Whegs
II, a bio-inspired design of the leg is made more functional by the addition of the useful,
nonbiological structure of the wheel. Whegs II boasts a segmented body that enables complex,
insect-like flexures that allow the climbing of large obstacles with improved stability. What makes
Whegs really interesting is that they use only one propulsion motor, yet passively adapt their gait to
the terrain using preflexive components. Because of these advantages, Whegs II can climb obstacles
taller than twice their leg lengths, accelerate so rapidly as to jump, and also run faster than 3 body
lengths per second.
Other compound wheel–leg combinations show promise as well. McGill’s ANT hybrid archi-
tecture, with springy, biologically inspired legs that are tipped with actuated wheels, results in
vehicles that can substantially outperform vehicles which use wheels or tank-treads alone (Steeves
et al., 2002).
To contend with the mutability of the real world, a robot may need to change shape and function
on the fly. Many bio-systems self-reconfigure to meet environmental circumstances, and this ability
is the inspiration for reconfigurable robotics (Fukuda and Kawakuchi, 1990; Rus and Vona, 2001).
For example, a robot could assume a flat or snakelike form to squeeze though a slim passage, but
then morph into a hexapod to traverse rough terrain upon exiting the passage. Reconfigurable
robotics researchers do not just focus on macroanimal forms though. Some researchers draw
reconfiguration analogies to molecules and in particular folding proteins, in robots labeled ‘‘mol-
ecule robots’’ (Kotay and Rus, 1999) (see Figure 6.5).

6.2.3 Walking and Running

Other roboticists choose a four-legged or quadruped configuration. While not as stable as a
hexapod, especially over rugged terrain, four legs do offer better inherent static stability than
two- or one-leg architectures.
In 1999, Sony introduced the Aibo robot dog (Figure 6.6) a quadruped robot with an RISC
processor, camera, and quadruped locomotion, and in this regard Aibo is distinguished from low-