Flexible tactile sensor array for distributed tactile sensing and slip detection in robotic hand grasping

Distributed tactile information sensing is crucial for the stable grasping and manipulation of intelligent robotics. This paper presents a flexible tactile sensor array with spatial resolution of 3.5 mm that can be easily worn on the robotic hand for distributed three-axis contact force sensing in grasping applications. The proposed tactile sensor array has 3 × 3 sensing units, each unit has a five-electrode pattern’s design and using conductive rubber as the sensing material. The fabricated prototype of the tactile sensor array has good flexibility, and its performance is characterized with high sensitivities: 0.471 V/N in x-axis and 0.466 V/N in y-axis. As for z-axis, the sensitivities are 0.201 V/N at 0˜6 N and 0.067 V/N at 6˜15 N measurement ranges. Then the tactile sensor array and its scanning circuit are integrated into the robotic hand for distributed three-axis contact force perception when grasping different objects. By using discrete wavelet transform analysis, the threshold values of wavelet coefficients for slip detection can be determined, and the slippage during robotic grasping of objects can be successfully detected. Therefore, the developed flexible tactile sensor array has the ability of detecting distributed contact forces and slippage simultaneously, and could be used for robotic dexterous grasping and manipulations.