**3. Integration process**

4 Will-be-set-by-IN-TECH

related to the iCub platform; section 3.1.1 presents a new implementation of iCub fingertip with experimental data related to their behavior characterization; section 3.2 is related to KASPAR and section 3.3 presents the ROBOSKIN integration on robot NAO; finally section 4

As we told before, ROBOSKIN tactile system, incorporates a distributed pressure sensor based on capacitive technology. The transducer consists of a soft dielectric sandwiched by electrodes. When pressure is applied to the sensor, the distance between the electrodes above and below the dielectric changes, and the capacitance changes accordingly (capacitance is a

The basis of the sensor is a flexible printed circuit board (PCB). It includes the electronics to obtain 12 measurements of capacitance and send them over a serial bus. In particular, each PCB includes 12 round pads, one for each taxel, and a capacitance to digital converter (CDC)

(a) (b)

**Figure 1.** The triangular module: (a) in the front view it is possible to see the 12 round taxels, in the back view the CDC chip from Analog Devices is shown; (b) An hexagonal patch glued on a cover with the

The chip can measure the capacitance of all taxels with 16 bit resolution, but we use only 8 bit measurements, as any higher resolution is covered by noise. As a result, one measurement unit corresponds to 2.88 fF. The CDC has an I2C serial interface and each chip can be assigned with a 2 bit address; therefore up to 4 chips can communicate over the same serial bus. The shape of the PCB is in most cases a triangle (only for the fingertips of the robot iCub we used a unique solution, which we will discuss in section 3.1.1), see figure 1(a). The triangular shape was chosen in analogy to polygonal modeling in 3D computer graphics, which uses triangles to describe the shapes of objects. The triangles can conform up to a certain degree to generic

The triangular PCBs also include the electronics to communicate between themselves: three communications ports placed along the sides of the triangle (one for input and two for output) relay the signals from one triangle to the adjacent one. Up to 16 triangles can be connected in this way (4 serial buses with 4 different addresses each) and only one of them needs to be connected to a microcontroller board (MTB, see figure 3). This is a critical advantage since it reduces the amount of wires and electrical connections that are required. The MTB can also

is dedicated to conclusion.

function of distance).

**2. ROBOSKIN technology**

(AD7147 from Analog Devices).

foam elastomer and electrically conductive lycra layers.

smooth curved surfaces (see figure 2(a) and figure 2(b)).

In order to integrate the ROBOSKIN sensor on a robot, this general procedure must be followed:

6 Will-be-set-by-IN-TECH 190 Smart Actuation and Sensing Systems – Recent Advances and Future Challenges

(a) (b) (c)

**Figure 4.** The production steps for the palm of iCub. For a description of each step, please refer to the text.

