Detection system of incident slippage and friction coefficient based on a flexible tactile sensor with structural electrodes

It is a task to estimate the surface roughness and slippage as a robotic finger slides through an object, but this is an essential perception of a human hand as a finger moves across a wide variety of surfaces or the hand grasps objects. In the present study, a novel flexible tactile sensor was developed for detecting the coefficient of friction and slippage. We introduced an innovative concept of structural electrodes consisting of a microstructure and distributed microelectrodes on a piezoelectric film to detect the lateral force that acts on a tactile sensor. As experimental results show, the output signals of two distributed microelectrodes can reveal the opposite voltage peaks corresponding to the compressive and tensile stress state underneath the microstructure as the held object begins to slip. Clear-cut signals effectively improve the definition of slippage occurrence compared with other slippage sensors. Furthermore, the coefficients of static friction for objects made of different materials were also evaluated based on slippage detection in a drop test. In order to facilitate the applications in a robot, a compact readout module integrated with a tactile sensor was also developed and demonstrated based on a PC-based program.