2. Design considerations

robots, contrary to the industrial robots, naturally require more interactions with humans and have to be designed accordingly. The term "social robot" was coined jointly by researchers in artificial intelligence and robotics in the early 90s and refers to the robots engaging in social interactions with the humans. Studies [1, 2] define social robots as autonomous agents designed to interact with humans and possibly other robots exhibiting the expected social behaviors of the assigned role. Such interactions, in addition to the primary expected tasks, involve communication, recognition of individuals, familiarization with the environment and adapting accordingly to the variety of situations encountered. In order to enable them to interact socially, these robots need to be equipped with what is generally termed as "social intelligence". Lazzeri et al. [3] argue that this social intelligence enables robots not only to converse with humans (and other robots) but also interpret the emotional signals and react accordingly hence producing an impression of a real human being. In addition to the conventional role of serving humans, other typical roles include providing guidance or assistance at homes, offices or public places, provide companionship and care services and serve as pets. The expectations from a social robot naturally vary as the function

Breazeal [4] argues that humans tend to anthropomorphize robots for interaction and identifies four classes of social robots. These include "socially evocative", "social interface", "socially receptive" and "sociable robots". Socially evocative robots, for instance toy robots, are designed to engage in entertaining interactive sessions with the humans. According to him,

of the role it takes.

4 Human-Robot Interaction - Theory and Application

Figure 1. Taxonomy of social robots in literature.

Every passing decade is forcing robot designers and engineers to push their skills to the limit. As robots integrate further into our lives, high expectations are posing new challenges in their creation. All robots, whether industrial, field or social, must address a number of design issues. However factors of social believability and social intelligence increase the complexity of designing a socially interactive robot. One of the foremost conditions of believability in a social robot is its near realistic embodiment, to which users can relate without reluctance or discomfort. Secondly a socially interactive robot is expected to be expressive in terms of rich dialog, emotions and gestures. In addition to expressiveness, a social robot is required to manifest social behavior which includes perception of its surroundings and ability to plan and execute appropriate goal oriented actions. Variance in social situations and expected performance outcomes make it difficult to generalize design strategy for a social robot. Nevertheless designers broadly divide design approaches into two categories i.e. Bio-inspired and Function-inspired [1]. Bio-inspired design strategies are a multitude of disciplines like anthropology, cognition, psychology and sociology. On the other hand function-inspired approaches focus on task oriented designs. However, realizing the gap between available technology and performance expectations is of prime significance.

#### 2.1. Embodiment and expressiveness

According to Fong et al. [1], a robot's visual appearance is the first projection of its believability. People establish performance expectations based on a robot's outlook. In a way, physical embodiment influences human robot interactions as people interact with humanoids differently from non-humanoids. Other than expectations, a robot's morphology plays a vital role in its usability, acceptability and expressiveness. Therefore it is required that a robot's morphology should correlate to its proposed functionality. For instance, robots that are intended to

2.1.1. Anthropomorphism

2.1.1.1. Humanoid head

design i.e. morphology, behavior and interaction.

able, as suggested in Mori's "Uncanny Valley" theory [6].

2.1.1.2. Whole-body dynamics and control

DARPA Robotics Challenge (DRC)<sup>1</sup>

www.romela.org/robocup/

https://en.wikipedia.org/wiki/DARPA\_Robotics\_Challenge

1

2

Anthropomorphism is the provenance of human characteristics in something non-human. According to Fink [5], anthropomorphism can be introduced in all three aspects of a robot's

Socially Believable Robots

7

http://dx.doi.org/10.5772/intechopen.71375

The most effective anthropomorphic feature of a robot is its head. To project human likeness and better expressiveness, the simplest kind of humanoid robot heads are equipped with RGB LEDs, cameras, microphones and speakers. These mechanical parts are mostly cost-effective and provide a variety of expressions for more naturalistic human robot interaction. DARwIn-OP, HOAP-3, Pepper, NAO, UXA-90, Roboy and ASIMO are some of the examples of humanoids with faces equipped with LEDs and speakers. Perception of emotions by humans, while interacting with these robots is at times difficult due to limited modes of expressions giving unrealistic or mechanical effect. Some humanoids are provided with kinematic heads. These humanoid heads can perform transformations from one emotional state to another by tilting head, moving eyes and mouth etc. In contrast to LEDs, these heads are equipped with actuators and moving parts which work in intense coordination. Romeo, iCUB, Simon, RoboThespian, MERTZ and KOBIAN RII, are some of the humanoids featuring kinematic head with moving eyelids, eyebrows, jaws and neck. In quest to manifest ultimate humanness, roboticists experimented with animatronic heads with flexible skin. Alice, Albert HUBO, Roman and Actroid are some of the examples of robots with animatronics head consisting of several DC motors and artificial skin made of special material called Frubber. Figure 3 shows three different kinds of humanoid heads with their ability to express emotions. Nevertheless such humanoid heads have a tendency to make users uncomfort-

The idea of substituting humans with surrogates for tasks like search and rescue in challenging scenarios has been prevailing for some time now [8]. With the introduction of socially interactive and socially assistive robots, designing humanoids to be autonomous has become inevitable. In a rich social setup, robots require high level of autonomy including extended physical mobility. Although robots are becoming more sophisticated both mechanically and emotionally, yet they are still far from achieving agile human-like manipulation and interaction, thus providing significant research potential in these areas. Dimensions of robot's body (i.e. height and weight etc.), Degree of Freedom (DoF), tactile sensors, number and flexibility of joints are the design factors that determine its mobility (i.e. walking, sitting, standing and turning etc.) and manipulation (i.e. reaching and grasping, pulling and pushing and holding etc.) capabilities. Whole-body control techniques [9, 10] have matured over the past few years enabling various humanoids to interact with their environment in a more robust manner. There is a steady transition of robot's actions in predictable contacts to unpredictable ones. Forums like

, RoboCup2 and other international robotic challenges [11]

Figure 2. Advance humanoids: (a) ATLAS, (b) Sophia, (c) Pepper.

carry out human like tasks must be equipped accordingly; visual human likeness may not be of much importance in such cases as in the case of ATLAS and similar humanoids (Figure 2a). On the other hand those designed for interaction purposes must be more human like, with distinct facial expressions (e.g. Sophia) (Figure 2b) or with emotional speech capabilities (e.g. Pepper) (Figure 2c).

With the aim to achieve a naturalistic embodiment, designers get inspiration from nature itself. Morphological design of natural looking social robots can be attributed to anthropomorphism. Based on their area of application, morphological inspirations for a robot's outlook can also be taken from zoomorphism (e.g. pets or creatures), caricature (e.g. animations or fictional characters) and functional expectations (e.g. assistive or service robots etc.). Nevertheless most social robots are intended to work with humans; thus the general notion is to give them a human-like appearance. Therefore we will emphasize more on anthropomorphism.
