The Bielefeld Anthropomorphic Robot Head “Flobi”
Ingo Lu¨tkebohle, Frank Hegel, Simon Schulz, Matthias Hackel, Britta Wrede, Sven Wachsmuth and Gerhard Sagerer
Abstract—A robot’s head is important both for directional
sensors and, in human-directed robotics, as the single most
visible interaction interface. However, designing a robot’s head
faces contradicting requirements when integrating powerful
sensing with social expression. Furher, reactions of the general
public show that current head designs often cause negative user
reactions and distract from the functional capabilities.
Therefore, this contribution presents a novel anthropomor-
phic robot head called “Flobi”, which combines state-of-the-art
sensing functionality with an exterior that elicits a sympathetic
emotional response. It can display primary and secondary
emotions in a human-like way, to enable intuitive human-robot-
interaction. To facilitate further research on facial appearance,
the exterior is fully modular and replaceable.
While current state-of-the-art still requires trade-offs when
integrating sensing and social expression, Flobi has been
designed to enable service robotic applications, with high-
resolution, wide-angle stereo vision, gyroscope motion compen-
sation and stereo audio. For ease of integration, the head is self-
contained, including 18 actuators, sensors and control boards,
all in a human-head sized package.
I. THE CHALLENGE OF SENSING VS. EXPRESSION
Building robots that are well suited for interaction with
humans is a challenging task that needs to be addressed by
a range of disciplines. One of the most challenging issues in
this vein at the moment, and for the foreseeable future, is the
design of a robot’s head. This is because a head has to realize
multiple functions with partially contradicting requirements.
Most important among these are active sensing and social
expression for intuitive human-robot interaction.
Corresponding to the first function, many robotic heads
have been reported on in the literature that exhibit powerful,
active sensing capabilities: Here, many, often large, sensors
are packed together and combined with few, powerful ac-
tuators for rapid, accurate motion. Examples include POP-
EYE [1], Cog [2] and the Karlsruhe Humanoid Head [3].
A recognizably distinct line of research has given us
robotic heads with social expressiveness that is intuitively
understandable to humans. These usually need many, small
actuators that are capable of smooth motion with varying
This work was partially supported by the German Federal Ministry
of Education and Research (BMBF) under grant no. 01IME01N and the
German Research Society (DFG) within the Collaborative Research Centre
673 “Alignment in Communication”.
Ingo Lu¨tkebohle, Frank Hegel, Britta Wrede and Gerhard Sagerer
are with the Applied Informatics Group, Bielefeld University, Germany.
filuetkeb,fhegel,bwredeg@techfak.uni-bielefeld.de
Matthias Hacke is with Mabotics GmbH, Germany. mhackel@mabotic.de
Simon Schulz and Sven Wachsmuth are with the Central Lab Facilities,
Cognitive Interaction Technology Excellence Cluster, Bielefeld University,
Germany. fsschulz,swachsmug@techfak.uni-bielefeld.de
dynamics. The exterior of such robots tends to be non-
frightening and generally signals the robot’s capabilities to
the non-technical eye. Examples of this approach include
Kismet [4], iCub [5], Infanoid [6] and iCat [7].
Obviously, both of these lines always exhibit features of
the other: Social robot heads also need sensors and sensor
heads also have an exterior. However, their requirements par-
tially contradict each other and therefore it is no surprise that
most projects so far have chosen a trade-off that favors either
sensing or social communication. We have summarized the
relevant state-of-the-art briefly in section II.
However, we believe that the state of the art has advanced
to a level where significant progress can only be made if both
aspects are implemented, and evaluated, in conjunction.
It has long been recognized that the motion of directed
sensors, such as cameras, is interpreted socially by humans,
even if not intended to do so [8]. This has two consequences:
Firstly, any kind of robotic head, when directed at humans,
has a social impact and adverse reactions can result if the ef-
fect of its exterior and motion are not adequately considered.
The consequences of failing to address this fact can readily
be discerned from popular reporting about robotics research,
which abounds with negative remarks about appearance.
Secondly, the social impact of a robot cannot be divided
from its function and studies of social behavior therefore
benefit from the use of a head whose function is comparable
to a functional system.
Fig. 1. Flobi male-neutral (left) and female-smiling (right) configurations.
The “Flobi” head is our contribution towards addressing
both the requirements for a sensor head and the requirements
for social interaction. On the sensor side, the head combines
a wide-angle, high resolution stereo camera setup with gy-
roscopes for motion compensation and stereo microphones
for speaker localization and speech recognition. The cameras