Even though the sense of touch is crucial for humans, most humanoid robots lack tactile sensing. While a large number of sensing technologies exist, it is not trivial to incorporate them into a robot. We have developed a compliant “skin” for humanoids that integrates a distributed pressure sensor based on capacitive technology. The skin is modular and can be deployed on nonflat surfaces. Each module scans locally a limited number of tactile-sensing elements and sends the data through a serial bus. This is a critical advantage as it reduces the number of wires. The resulting system is compact and has been successfully integrated into three different humanoid robots. We have performed tests that show that the sensor has favorable characteristics and implemented algorithms to compensate the hysteresis and drift of the sensor. Experiments with the humanoid robot iCub prove that the sensors can be used to grasp unmodeled, fragile objects

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Distributed tactile sensing is crucial to perform stable, subtle, and precise manipulation so that a robot can recognize and handle objects properly. However, currently existing skin sensors still have common problems such as complex and expensive production or are difficult to integrate into robot hands. In particular, a practical distributed soft skin sensor system that can cover various parts of the robot hand, measure force in 3axis, with a subcentimeter spatial density, and digital output at the same time does not exist yet. This paper discusses uSkin, a soft, distributed, 3-axis force sensor for robot hands and presents its implementation for multi-curved fingertips. The sensor is lowcost, easy to manufacture, and can measure normal and shear forces. The experimental results revealed that this sensor has 10% hysteresis for perpendicular force with a maximum range of 6 N. The Signal to Noise Ratio (SNR) value of 54 dB for 0.4 N load was achieved, which constitutes the state of the art for this kind of sensors. Evaluation experiments also showed that the distributed 3-axis load cells could produce vectors that represent the shape of objects. This opens the possibility that the sensor can be used for classifying different shapes. Furthermore, the fingertip sensor was installed on the Allegro hand and the changing force measurements when the robot is grasping an object are presented.

In order to successfully perform object manipulation, humanoid robots must be equipped with tactile sensors. However, the limited space that is available in robotic fingers imposes severe design constraints. In [1] we presented a small prototype fingertip which incorporates a capacitive pressure system. This paper shows an improved version, which has been integrated on the hand of the humanoid robot iCub. The fingertip is 14.5 mm long and 13 mm wide. The capacitive pressure sensor system has 12 sensitive zones and includes the electronics to send the 12 measurements over a serial bus with only 4 wires. Each synthetic fingertip is shaped approximately like a human fingertip. Furthermore, an integral part of the capacitive sensor is soft silicone foam, and therefore the fingertip is compliant. We describe the structure of the fingertip, their integration on the humanoid robot iCub and present test results to show the characteristics of the sensor.