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 the slippage as a robotic finger sliding through the object but this is an essential perception of a human hand as finger moving on a wide variety of surface or grasping objects. In 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, which consists of a microstructure and distributed microelectrodes upon a piezoelectric film, to detect the lateral force acting on the tactile sensor. As experimental results, 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 holding object start to slip. Therefore, the clear-cut signals effectively improve the definition of slippage occurrence as compared with other slippage sensors. Furthermore, the coefficients of static friction for objects made of different materials were also evaluated based on the slippage detection in a drop test. In order to facilitate the applications in robot, a compact readout module integrated with tactile sensor has also developed and demonstrated based on PC-based program.