## 3 System Overview  
This section includes the hardware components followed by the description of the proposed approach for hug detection.
The circuit is composed of a microprocessor (Arduino UNO) connected to the smartphone and the external computer by a Wi-Fi module (Seeed Studio, V1.0). A printed circuit board was attached on top of the Arduino and the WiFi shield. Alongside the sensors, the circuit contains three full-color LEDs and one vibration motor. The LEDs were placed on the sides to look like the cheeks and in the tail tip to emphasize the caricatures' features. The vibration motor was attached to the bottom of the plastic case. The robotic device has two types of sensors to detect tangible gestures: pressure sensors covering the robot's body, and a stretch sensor in the tail. The pressure sensors were made to endow the robotic device with huge detection. It is made of 5 mm thick conductive foam (Seiren Electronics Co., Tokyo, Japan) divided into eight petal-shaped pieces covering an 18 cm diameter plastic sphere. Handmade electrodes were made using copper sheets with conductive tape (Seiren Electronics Co., Tokyo, Japan) and attached to the foam pieces. The wires were attached to the copper sheet, and each piece of the sensor was connected in parallel with a 15 Kohm resistor. The stretch sensor was made following the approach from [55] that uses the properties and structure of the material for sensing gestures. A silicone tail containing a magnet, together with a linear Hall effect sensor (Figure 3) was used to detect when the tail was stretched. Silicon was poured into a cast of half of the tail (longitudinal section), and the wires were introduced while the silicon was still soft. After it dried, the other half was poured covering the wires. To prevent the wires from snapping, they were coiled and placed inside the cast before pouring in the silicon. When the tail is pulled, the distance between the magnet and sensor changes, which is detected as changes in the magnetic field.  
The second part comprises a smartphone (Galaxy Nexus, Samsung electronics Co., Suwon, South Korea) which is connected to a pico-projector (EAD-R10, Samsung electronics Co., Suwon, South Korea), making it possible to display the screen content on any surface. The projector was placed in one eye, and the smartphone's camera in the other. An Android application manages the content of the screen, which changes according to the interaction with the device. The smartphone works as a server, receiving the sensor data and sending it to the external computer.  
Figure 1: [PERSON]: a huggable robot companion with caricatured appearance.  
Figure 2: Device components: composed by a smartphone that communicates with the robot’s circuit and an external computer.  
The last component of the system is an external computer, which is used to visualize and store the sensor data. All of the elements are connected using TCP/IP sockets. The smartphone works as the server, mediating the communication between the microcontroller and external computer. By doing this, it is possible to send commands from the computer to the device remotely (for example, to start collecting data from the sensors and visualize it on the computer screen).