**3.2 Actuators**

6 Will-be-set-by-IN-TECH

Advances in nano-materials are making it possible to integrate a large amount of sensors in flexible and stretchable surfaces (Bao et al., 2009; Peratech, 2011; Takei et al., 2010). Rob finds the approach taken by Prof. Zhenan Bao very interesting since it includes not only a sensitive resolution that surpasses that of human skin, but also the possibility to sense chemicals or biological materials (Bao et al., 2009). In addition, they are also working on embedding solar cells within the same films (Lipomi et al., 2011), which is an outstanding innovation since it

Rob remembers that human skin is composed of two primary layers: epidermis and dermis. The dermis is located beneath the epidermis and contains all sensors for temperature and touch. He thinks about this because the dermis helps also to cushion the body from stress and strain, a task that is augmented by the morphological interaction of muscles, water, bones, etc. This dynamic plays an important role in tasks such as manipulation and locomotion. Therefore the design of Rob's future humanoid robot's skin should include not only a large amount and various types of sensors, but also an inner mechanism that provides similar

Rob knows that microphones are the standard tools for acquiring sound information from the environment in a robotic platform. They can be installed in different configurations and detect/regulate sound in ways that surpass human abilities. But detecting a sound is just the starting point of a more complex challenge. Once a sound has been detected, it is time to localize the origin or source of that sound. Humans' remarkable ability to detect, localize and recognize sound can be exemplified using the *cocktail-party effect*. This term describes the ability of a person to direct his/her attention on the source of a sound amidst other sound sources which makes possible, for example, to talk to another person in a noisy, crowded

It has been shown in humans that a continuous interaction between auditory and visual cues take place in the brain (Cui et al., 2008). In humanoid robots the localization of a sound source is mainly done by computing the difference in times and levels of signals arriving to the different sensors, in this case microphones (Keyrouz, 2008). Attempts to integrate sensor information from visual with auditory modalities has also been done in humanoid platforms

Rob trusts that at least from the hardware point of view, he will not have many problems. The real challenge for the future is to improve the way different sensor modalities can be merged to replicate or surpass the abilities found in humans. However this point belongs to the *mindware* of his platform, so he will focus on working in optimized configurations of microphones.

Rob gets a strange feeling at this point and thinks, "Should I even consider spending time thinking about a robot with these two senses? After all, robots do not need to eat anything as humans do, they just need a power cable and will have all the energy they need. And electricity has no smell, right?" But then he starts thinking in more holistic terms– maybe robots will need to somehow recognize smells and flavors; moreover, they will need to associate that information with visual, auditory and tactile cues. Otherwise it is going to be difficult, if not impossible, to interact with humans using more or less the same language. Artificial noses and "tongues" have already been developed and they are also overmatching those of humans (Mahmoudi, 2009). Artificial noses are able to detect and classify thousands

would help to solve another major challenge for humanoid robots, i.e. energy.

dynamics like those found in human bodies.

party (Haykin & Chen, 2005).

(Ruesch et al., 2008).

**3.1.4 Odor and taste**

**3.1.3 Sound**

In the case of actuators, Rob illustrates the current state of the art of active components, although he is lately more biased towards approaches which make use of spring-damper components. He knows that the right choice of these components forms one of the critical challenges for his future humanoid robot. Rob's preference for non-linear components comes from the fact that the human body is made, from an engineering perspective, almost exclusively of spring-damper type elements: cartilages, tendons, muscles, fat, skin, etc. whose interaction results in stability, energy efficiency and adaptability.
