Grasping Strategy and Control Algorithm of Two Robotic Fingers Equipped with Optical Three-Axis Tactile Sensors

AbstractThis paper presents grasping strategy of robot fingers based on tactile sensing information acquired by optical three-axis tactile sensor. We developed a novel optical three-axis tactile sensor system based on an optical waveguide transduction method capable of acquiring normal and shearing forces. The sensors are mounted on fingertips of two robotic fingers. To enhance the ability of recognizing and manipulating objects, we designed the robot control system architecture comprised of connection module, thinking routines, and a hand/finger control modules. We proposed tactile sensing-based control algorithm in the robot finger control system to control fingertips movements by defining optimum grasp pressure and perform re-push movement when slippage was detected. Verification experiments were conducted whose results revealed that the finger's system managed to recognize the stiffness of unknown objects and complied with sudden changes of the object's weight during object manipulation tasks

Advanced Design of Columnar-conical Feeler-type Optical Three-axis Tactile Sensor

AbstractAlthough the three-axis tactile sensor is capable of delicate measurement, it is weak for heavy contact force. In order to enhance resistance to a high degree of applied force, we attached a rubber skin onto the sensor surface to protect the sensing element. FEM analyses found that sensitivity is not significantly reduced and that the skin induces subsidiary effects such as the disappearance of insensible areas and the enhancement of stability of the columnar feeler. If the skin is substantially softer than the columnar-conical feeler, the sensor can measure three-axis force without reduction of sensitivity. Based on these simulated results, we produced a columnar-conical feeler-type three-axis tactile sensor with rubber skin. The experimental results show, as demonstrated by FEM analyses, that the sensor possesses three-axis sensing capability and that the insensible area vanishes