Roboethics - Ethical Engineering for International Development and Environmental Sustainability - page 71

and move sideways or turn quickly. Therefore, legged robots can work in environ-
ments which are unsuitable for wheeled robots. However, wheeled robots which use
Mecanum wheels can also, in principle, move in any direction using rollers at an
angle around the periphery or sometimes centrally mounted on an axle that can be
pivoted (Diegel et al. 2002 ).
The design of legged robots is a more complex problem than the design of
wheeled robots, since a generally smooth pace is required and the robot needs to
remain stable. Where interaction with the user is involved, the robot will need to
move at walking pace, adjust its speed to the user's desired pace, not overbalance
the user, and have motion which looks natural. Legged robots can be classifi ed by
their number of legs, i.e. (1) one leg (hopping), (2) two legs (biped), (3) four legs
(multiped), (4) six legs (hexapod) and (5) more than six legs (snake).
From the control engineering perspective, walking on two legs is a complex sta-
bility problem. Bipedal robots have high-order highly coupled nonlinear dynamics
and discrete changes in dynamics. While walking, the robot alternates between a
statically stable phase with both feet on the ground and a statically unstable phase
with only one foot in contact (Kati 2003 ). The two main

approaches to achieving stable and reliable bipedal walk are walking pattern gen-
erators and robot controllers (Zhou and Low 2001 ; Zhou et al. 2000 ; Zielinska and
Heng 2002 ). Mechanisms to prevent overbalance include control of the foot landing
position and the desired zero momentum point (Hirai et al. 1998 ).
Humanoid robots have 'human characteristics'. Bipedal walking machines
equipped with external sensors are the basis for humanoid robots, and a number of
prototypes are currently available (Kopacek 2013 ). They have a torso, two arms and
two legs and a head with a 'face', 'eyes' and a 'mouth'. However, there is a great
difference between a bipedal walking machine and something which looks and
thinks like a person and is, for instance, able to display emotion appropriately,
engage in conversation with people and learn from experience and by observing its
surroundings. A number of robots, including some museum guide robots (Burgard
et al. 1999 ; Thrun et al. 2000 ) and humanoid robots (Barakova and Lourens 2010 ),
have simple displays of emotion and are able to engage in simple interactions with
people. The voice quality in synthetic speech output is improving and becoming
more natural. However, the development of 'intelligence' able to produce appropri-
ate output in response to complex input is still technically challenging. The associ-
ated ethical issues will be discussed in Sect. 3 .
Research on the desirability or otherwise of the resemblance of robots to a person
is still inconclusive. For instance, Mori ( 1970 ) developed a function relating robot
acceptance to its similarity to a person and found an 'uncanny valley' in which robots
are too similar to people and the differences cause disquiet. Several studies (e.g.
Arras and Cerqui 2005 , Hersh and Johnson 2010 , Oestreicher 2007 and Wu et al.
2012 ) have found that potential users preferred a robot looking like a machine to one
with a humanoid appearance. On the other hand, other studies indicate that people
prefer software agents with human faces (Kiesler and Sproull 1997 ; Koda and Maes
1996 ; Takeuchi and Naito 1995 ), robots with a more human appearance (Hinds et al.
2004 ) and robots to communicate in a humanlike way (Dautenhahn et al. 2005 ).

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