Object Exploration Using a Three-Axis Tactile Sensing Information

Problem statement: To advance the robust object recognition of robots, we present an algorithm for object exploration based on three-axis tactile data that is necessary and sufficient for the evaluation of contact phenomena. Approach: The object surface contour is acquired by controlling the finger position so that the normal force, measured by optical three-axis tactile sensors, remains constant as two fingertips slide along the object surface. In this algorithm, when the robot grasps an object, the tangential force increment is checked to judge the initial contact state because it is more sensitive than the normal force. After contact between the fingertips and the object, the normal force is adjusted to remain constant with a tolerant value between the upper and lower thresholds. Results: In the verification test, shape exploration experiments were conducted using a hand-arm robot equipped with our tactile sensor and a hard sinusoidal-shaped wooden object. Experimental results show that the hand-arm robot is capable of gathering the object contour having a concave or convex portion because its finger position controlled by three-axis tactile sensing information follows the object surface. Conclusion/Recommendations: We derive a control algorithm in robot fingers based on time tangential force increment and normal force detection to perform a shape exploration procedure.